New Study of Antares Creates the Best Map Ever of a Distant Star

New Study of Antares Creates the Best Map Ever of a Distant Star:

When stars exhaust their supply of hydrogen fuel, they exit the main sequence phase of their evolution and enter into what is known as the Red Giant Branch (RGB) phase. This is characterized by the stars expanding significantly and becoming tens of thousands of times larger than our Sun. They also become dimmer and cooler, which lends them a reddish-orange appearance (hence the name).

Recently, a team of astronomers used the ESO’s Very Large Telescope Interferometer (VLTI) to map one such star, the red supergiant Antares. In so doing, they were able to create the most detailed map of a star other than our Sun. The images they took also revealed some unexpected things about this supergiant star, all of which could help astronomers to better understand the dynamics and evolution of red giant stars.

The study which details their work, titled “Vigorous Atmospheric Motions in the Red Supergiant Supernova Progenitor Antares“, recently appeared in the journal Nature. As indicated in the study, the team – which was led by Keiichi Ohnaka, an associate professor at the UCN Institute of Astronomy in Chile = relied on the VLTI at the ESO’s Paranal Observatory in Chile to map Antares’s surface and measure the motions of its surface material.

Artist’s impression of the red supergiant star Antares, located 550 ly away in the constellation of Scorpius. Credit: ESO/M. Kornmesser

The purpose of their study was to chart how stars that have entered their RGB phase begin to change. The VLTI is uniquely suited to this task, since it is capable of combining light from four different telescopes – the 8.2-metre Unit Telescopes, or the smaller Auxiliary Telescopes – to create one virtual telescope that has the resolution of a telescope lens measuring 200 meters across.

This allows the VLTI to resolve fine details far beyond what can be seen with a single telescope. As Prof. Ohnaka explained in a recent ESO press statement:

“How stars like Antares lose mass so quickly in the final phase of their evolution has been a problem for over half a century. The VLTI is the only facility that can directly measure the gas motions in the extended atmosphere of Antares — a crucial step towards clarifying this problem. The next challenge is to identify what’s driving the turbulent motions.”

For their study, the team relied on three of the VLTI Auxiliary Telescopes and an instrument called the Astronomical Multi-BEam combineR (AMBER). This near-infrared spectro-interferometric instrument combines three telescopic beams coherently, allowing astronomers to measure the visibilities and closure phases of stars. Using these instruments, the team obtained images of Antares’ surface over a small range of infrared wavelengths.

From these, the team was able to calculate the difference between the speed of atmospheric gas at different locations on Antares’ surface, as well as its average speed over the entire surface. This resulted in a two-dimensional velocity map of Antares, which is the first such map created of another star other than the Sun. As noted, it is also the most-detailed map of any star beyond our Solar System to date.

The study also made some interesting discoveries of what takes place on Antares’ surface and in its atmosphere. For example, they found evidence for high-speed upwellings of gas that reached distances of up to 1.7 Solar radii into space – much farther than previously thought. This, they claimed, could not be explained by convection alone, the process whereby cold material moves downwards and hot material upwards in a circular pattern.

This process occurs on Earth in the atmosphere and with ocean currents, but it is also responsible for moving pockets of hotter and colder gas around within stars. The fact that convection cannot explain the behavior of Antares extended atmosphere would therefore suggests that some new and unidentified process common to red giant stars must be responsible.

These results therefor offer new opportunities for research into stellar evolution, which is made possible thanks to next-generation instruments like the VTLI. As Ohnaka concluded:

“In the future, this observing technique can be applied to different types of stars to study their surfaces and atmospheres in unprecedented detail. This has been limited to just the Sun up to now. Our work brings stellar astrophysics to a new dimension and opens an entirely new window to observe stars.”

Not only is this kind of research improving our understanding of stars beyond our Solar System, it lets us know what to expect when our Sun exits it main sequence phase and begins expanding to become a red giant. Though that day is billions of years away and we can’t be certain humanity will even be around by that time, knowing the mechanics of stellar evolution is important to our understanding of the Universe.

It pays to know that even after we are gone, we can predict what will still be here and for how long. Be sure to check out this 3D animation of Antares, courtesy of the ESO:

Further Reading: ESO, Nature

The post New Study of Antares Creates the Best Map Ever of a Distant Star appeared first on Universe Today.

Dragonfly Proposed to NASA as Daring New Frontiers Mission to Titan

Dragonfly Proposed to NASA as Daring New Frontiers Mission to Titan:

In late 1970s and early 80s, scientists got their first detailed look at Saturn’s largest moon Titan. Thanks to the Pioneer 11 probe, which was then followed by the Voyager 1 and 2 missions, the people of Earth were treated to images and readings of this mysterious moon. What these revealed was a cold satellite that nevertheless had a dense, nitrogen-rich atmosphere.

Thanks to the Cassini-Huygens mission, which reached Titan in July of 2004 and will be ending its mission on September 15th, the mysteries of this moon have only deepened. Hence why NASA hopes to send more missions there in the near future, like the Dragonfly concept. This craft is the work of the John Hopkins University Applied Physics Laboratory (JHUAPL), which they just submitted an official proposal for.

Essentially, Dragonfly would be a New Frontiers-class mission that would use a dual-quadcopter setup to get around. This would enable vertical-takeoff and landing (VTOL), ensuring that the vehicle would be capable of exploring Titan’s atmosphere and conducting science on the surface. And of course, it would also investigate Titan’s methane lakes to see what kind of chemistry is taking place within them.

Image of Titan’s atmosphere, snapped by the Cassini spacecraft. Credit: NASA/JPL/Space Science Institute

The goal of all this would be to shed light on Titan’s mysterious environment, which not only has a methane cycle similar to Earth’s own water cycle, but is rich in prebiotic and organic chemistry. In short, Titan is an “ocean world” of our Solar System – along with Jupiter’s moons Europa and Ganymede, and Saturn’s moon of Enceladus – that could contain all the ingredients necessary for life.

What’s more, previous studies have shown that the moon is covered in rich deposits of organic material that are undergoing chemical processes, ones that might be similar to those that took place on Earth billions of years ago. Because of this, scientists have come to view Titan as a sort of planetary laboratory, where the chemical reactions that may have led to life on Earth could be studied.

As Elizabeth Turtle, a planetary scientist at JHUAPL and the principal investigator for the Dragonfly mission, told Universe Today via email:

“Titan offers abundant complex organics on the surface of a water-ice-dominated ocean world, making it an ideal destination to study prebiotic chemistry and to document the habitability of an extraterrestrial environment. Because Titan’s atmosphere obscures the surface at many wavelengths, we have limited information about the materials that make up the surface and how they’re processed.  By making detailed surface composition measurements in multiple locations, Dragonfly would reveal what the surface is made of and how far prebiotic chemistry has progressed in environments that provide known key ingredients for life, identifying the chemical building blocks available and processes at work to produce biologically relevant compounds.”

In addition, Dragonfly would also use remote-sensing observations to characterize the geology of landing sites. In addition to providing context for the samples, it would also allow for seismic studies to determine the structure of the Titan and the presence of subsurface activity. Last, but not least, Dragonfly would use meteorology sensors and remote-sensing instruments to gather information on the planet’s atmospheric and surface conditions.

The Aerial Vehicle for In-situ and Airborne Titan Reconnaissance (AVIATR) is another concept for an aerial explorer for Titan. Credit: Mike Malaska

While multiple proposals have been made for a robotic explorer mission of Titan, most of these have taken the form of either an aerial platforms or a combination balloon and a lander. The Aerial Vehicle for In-situ and Airborne Titan Reconnaissance (AVIATR), a proposal made in the past by Jason Barnes and a team of researchers from the University of Idaho, is an example of the former.

In the latter category, you have concepts like the Titan Saturn System Mission (TSSM), a concept that was being jointly-developed by the European Space Agency (ESA) and NASA. An Outer Planets Flagship Mission concept, the design of the TSSM consisted of three elements – a NASA orbiter, an ESA-designed lander to explore Titan’s lakes, and an ESA-designed Montgolfiere balloon to explore its atmosphere.

What separates Dragonfly from these and other concepts is its ability to conduct aerial and ground-based studies with a single platform. As Dr. Turtle explained:

“Dragonfly would be an in situ mission to perform detailed measurements of Titan’s surface composition and conditions to understand the habitability of this unique organic-rich ocean world.  We proposed a rotorcraft to take advantage of Titan’s dense, calm atmosphere and low gravity (which make flight easier on Titan than it is on Earth) to convey a capable suite of instruments from place to place — 10s to 100s of kilometers apart — to make measurements in different geologic settings.  Unlike other aerial concepts that have been considered for Titan exploration (of which there have been several), Dragonfly would spend most of its time on the surface performing measurements, before flying to another site.”

Dragonfly‘s suite of instruments would include mass spectrometers to study the composition of the surface and atmosphere; gamma-ray spectrometers, which would measure the composition of the subsurface (i.e. looking for evidence of an interior ocean); meteorology and geophysics sensors, which would measure wind, atmospheric pressure, temperature and seismic activity; and a camera suite to snap pictures of the surface.

Artist’s concept of the Titan Aerial Daughter quadcopter and its “Mothership” balloon. Credit: NASA/STMD

Given Titan’s dense atmosphere, solar cells would not be an effective option for a robotic mission. As such, the Dragonfly would rely on a Multi-Mission Radioisotope Thermoelectric Generator (MMRTG) for power, similar to what the Curiosity rover uses. While robotic missions that rely on nuclear power sources are not exactly cheap, they do enable missions that can last for years at a time and conduct invaluable research (as Curiosity has shown).

As Peter Bedini – the Program Manager at the JHUAPL Space Department and Dragonfly’s project manager – explained, this would allow for a long-term mission with significant returns:

“We could take a lander, put it on Titan, take these four measurements at one place, and significantly increase our understanding of Titan and similar moons. However, we can multiply the value of the mission if we add aerial mobility, which would enable us to access a variety of geologic settings, maximizing the science return and lowering mission risk by going over or around obstacles.”

In the end, a mission like Dragonfly would be able to investigate how far prebiotic chemistry has progressed on Titan. These types of experiments, where organic building blocks are combined and exposed to energy to see if life emerges, cannot be performed in a laboratory (mainly because of the timescales involved). As such, scientists hope to see how far things have progressed on Titan’s surface, where prebiotic conditions have existed for eons.

Titan’s thick, nitrogen and hydrocarbon-rich atmosphere lends the planet a cloudy, yellowsh-brown appearance. Credit: NASA/JPL-Caltech/Space Science Institute

In addition, scientists will also be looking for chemical signatures that indicate the presence of water and/or hydrocarbon-based life. In the past, it has been speculated that life could exist within Titan’s interior, and that exotic methanogenic lifeforms could even exist on its surface. Finding evidence of such life would challenge our notions of where life can emerge, and greatly enhance the search for life within the Solar System and beyond.

As Dr. Turtle indicated, mission selection will be coming soon, and whether or not the Dragonfly mission will be sent to Titan should be decided in just a few years time:

“Later this fall, NASA will select a few of the proposed New Frontiers missions for further work in Phase A Concept Studies” she said. “Those studies would run for most of 2018, followed by another round of review.  And the final selection of a flight mission would be in mid-2019… Missions proposed to this round of the New Frontiers Program would be scheduled to launch before the end of 2025.”

And be sure to check out this video of a possible Dragonfly mission, courtesy of the JHUAPL:



Further Reading: JHU Hub

The post Dragonfly Proposed to NASA as Daring New Frontiers Mission to Titan appeared first on Universe Today.

Is the “Alien Megastructure” around Tabby’s Star Actually a Ringed Gas Giant?

Is the “Alien Megastructure” around Tabby’s Star Actually a Ringed Gas Giant?:

KIC 8462852 (aka. Tabby’s Star) continues to be a source of both fascination and controversy. Ever since it was first seen to be undergoing strange and sudden dips in brightness (in October of 2015) astronomers have been speculating as to what could be causing this. Since that time, various explanations have been offered, including large asteroids, a large planet, a debris disc or even an alien megastructure.

The latest suggestion for a natural explanation comes from the University of Antioquia in Colombia, where a team of researchers have proposed that both the larger and smaller drops in brightness could be the result of a ringed planet similar to Saturn transiting in front of the star. This, they claim, would explain both the sudden drops in brightness and the more subtle dips seen over time.

The study, titled “Anomalous Lightcurves of Young Tilted Exorings“, recently appeared online. Led by Mario Sucerquia, a postdoctoral student at the University of Antioquia’s Department of Astronomy, the team performed numerical simulations and semi-analytical calculations to determine if a the transits of a ringed gas giant could explain the recent observations made of Tabby’s Star.

An artist impression of an exomoon orbiting a ringed exoplanet. Credit: Andy McLatchie

Currently, exoplanet-hunters use a number of methods to detect planetary candidates. One of the most popular is known as the Transit Method, where astronomers measure dips in a star’s brightness caused by a planet passing between it and the observer (i.e. transiting in front of a star). How a gas giant with rings would dim a star’s light was of concern here because it would do so in an irregular way.

Basically, the rings would be the first thing to obscure light coming from the star, but only to a small degree. Once the bulk of the gas giant transited the star, a significant drop would occur followed a second smaller drop as the rings on the other side passed by. But since the rings would be at a different angle every time, the smaller dips would be larger or smaller and the only way to know for sure would be to compare multiple transits.

In the past, researchers from the University of Antioquia developed a novel method for detecting rings around exoplanets (“exorings”). Essentially, they showed how an increase in the depth of a transit signal and the so-called “photo-ring” effect (often mistaken for false-positives in previous surveys) could be interpreted as signs of an exoplanet with a Saturn-like ring structure.

The team that devised this method was led by Jorge I. Zuluaga of the Harvard Smithsonian Center for Astrophysics (CfA), who was also a co-author on this study.  To test this theory with KIC 8462852, the team simulated a light curve from a ringed planet that was about 0.1 AU from the star. What they found was that a tilted ring structure could explain the dimming effects detected from Tabby’s Star in the past.

Artist’s impression of an exoplanet with an extensive ring system. Credit and Copyright: Ron Miller

They also found that a tilted ring structure would undergo short-term changes in shape and orientation as a result of the star’s gravitational tug on them. These would be apparent due to strong variations of transit depth and contact times even between consecutive transits. This too would likely be interpreted as anomalies in signal data, or lead to miscalculations of a planet’s properties (i.e. radius, semi-major axis, stellar density, etc).

This is not the first time that a ringed-structure has been suggested as an explanation for the mystery that is Tabby’s Star. And the team admits that there are other possible explanations, which include the possibility of an exomoon breaking up around a larger planet (i.e. leaving a debris disk). But as Sucerquia indicated in an interview with New Scientist, this latest study does offer some compelling food for thought:

“The point of this work is to show the community that there are mechanisms that can alter the light curves. These changes can be generated by the dynamics of the moons or the rings, and the changes in these systems can occur in such short scales as to be detected in just a few years.”

Another interesting takeaway from the research study is the fact that oscillating ring structures could also account for the strangeness of some light-curves that are already known. In other words, its possible that astronomers have already found evidence of ringed exoplanets, and simply didn’t know it. Looking ahead, it is possible that future surveys could turn up plenty more of these worlds as well.

Of course, if this study should prove to be correct, it means that what some consider our best hope of finding an alien megastructure has now been lost. Admittedly, this would be a disappointment. If there’s one thing about the mystery of Tabby’s Star that has been consistently intriguing, it’s the fact that a megastructure couldn’t be ruled out. If we have come to that point at last, there’s not much more to say.

Except, perhaps, that’s it’s a big Universe! There’s sure to be a Kardashev Type II civilization out there somewhere!

Further Reading: New Scientists, arXiv

The post Is the “Alien Megastructure” around Tabby’s Star Actually a Ringed Gas Giant? appeared first on Universe Today.

Here's a Weather Update for Solar Eclipse Day (Aug. 21, 2017)

Here's a Weather Update for Solar Eclipse Day (Aug. 21, 2017):

A cloudy partial solar eclipse.

Credit: Deacon MacMillan/Flickr

With eclipse day fast approaching, many people are obviously concerned about how the weather will impact their viewing. Here's how it's looking for locations all along the eclipse path. Before getting into this, however, I want to make sure anyone reading this acknowledges a "reality check" that this event is still three days away, and forecasters are not overly confident on some of the finer details. Over the weekend, this confidence will increase, especially as Monday comes into the time range of various shorter-term, higher-resolution computer models.

Pacific Northwest/Rocky Mountains/Northern Great Plains

The Oregon/Idaho/Wyoming part of the total eclipse path will experience a high-pressure ridge over the Pacific Northwest on Monday, according to the National Weather Service. There will also be a weak low off the Southern California coast that sends some monsoon moisture north from the desert Southwest — but all models keep the moisture south of the Oregon/Nevada border. That should ensure mostly clear skies for much of Oregon come Monday morning. The exception to this would be marine clouds coming onshore along Oregon's central coast. From a climatological point of view, however, marine clouds don't make it very far inland, so locations from the Coast Range eastward appear to have a very good chance of clear skies for the eclipse Monday morning.

For Idaho, haze and smoke could be present from area wildfires. It looks like the best cloud/storm chances will remain across the southern highlands and perhaps out of the totality path. [Solar Eclipse 2017: Traffic and Weather Forecasts for States in Totality]

As for Wyoming, the main weather concern for eclipse day will be a threat for scattered to occasionally broken cloud cover. For now, the consensus is a 30 to 60 percent cloud cover along the path of totality during the eclipse. Most of these clouds will be of the high and mid cloud variety with cumulus cloud buildups, mainly over the mountains, where only isolated shower or thunderstorm activity is expected.

Central Great Plains

Pushing into Nebraska/Kansas/Missouri and southern Illinois, the situation becomes more problematic, as a storm system is expected to move across northern Nebraska Monday morning. So those living near and along the totality path in Nebraska may have to deal with some potential storms and cloudiness early on Monday. The big question that we're focusing on right now is whether the clouds can clear enough later Monday morning after the rain in time for the eclipse.

Based on the latest guidance models, it seems that yes, there may be morning clouds and storms, but there's a decent chance that they will begin to scatter or break up by late morning. Obviously, trying to predict a cloud forecast with certainty for a 2-minute window that's still a few days away is a significant challenge.

Looking at Kansas and Missouri, this same unsettled weather system will be a factor. That, combined with a strong southerly wind, brings increasing low-level moisture for Sunday night into Monday. The GFS (Global Forecast System) and Canadian models are more bullish on rain and cloud-cover chances; this may be an issue for eclipse watchers.

But the Nebraska storm is expected to shift rapidly into Iowa by late Monday. As such, there is better support for good eclipse viewing for areas farther east into east-central and southeast Missouri, as well as southern Illinois, which should be farther away from what could be isolated thunderstorms. Western and central Missouri look to be in the worst spot in this four-state region. [Total Solar Eclipse 2017: When, Where and How to See It (Safely)]

Ohio and Tennessee valleys

Looking farther east at Kentucky and Tennessee, high pressure at the surface and aloft is expected to remain in place across the region. Kentucky looks to remain on the northern periphery of the ridge, and some of the model data suggest that isolated afternoon or evening storms could occur. Skies look to remain mainly clear in the morning, with cumulus clouds popping up during the afternoon.

In general terms, it looks like very typical weather for late August in the Ohio Valley. However, the development of these clouds is dependent on warming from the afternoon sun, and of course, solar heating will be reduced during Monday afternoon. Cumulus clouds may begin to form and then dissipate as the air cools in response to the eclipse. The same holds true for Tennessee, with 30 to 40 percent cloud cover currently anticipated, with only a slight probability (20 percent or less) for most of this region.

Piedmont and Southeast coast 

Our final stop is northeast Georgia and the Carolinas. Unfortunately, a stalled weather front is running from northern sections of Georgia and South Carolina east through the south end of North Carolina. And that front quite possibly could generate scattered afternoon showers and thunderstorms, which may wreak havoc for those wanting to witness the eclipse.

In this type of summer/sultry pattern, it is always difficult to discern, especially a few days out, specifically the different cloud and precipitation coverage. On a positive note, there are signs that an offshore ridge of high pressure will try to build in, possibly suppressing somewhat any cloud or shower development. The eclipse could also aid in keeping the threat of daytime clouds and shower development down by helping to lower temperatures in similar fashion to what we noted for Kentucky and Tennessee. Still, based on the projected setup, it is prudent to mention at least a 30 to 35 percent chance of showers and thunderstorms. Based on long-term climatological records, the best chance of encountering building afternoon clouds and showers will be over the high-terrain areas (Blue Ridge, Appalachian and Great Smoky mountains), while the best chance of getting some views of the sun will be along the coastal plain.

Some useful websites

Here are some websites related to weather and the upcoming Great American Solar Eclipse that may interest you:

National Weather Service Eclipse Page

Joe Rao's Eclipse Tutorial and Weather Prospects in Weatherwise Magazine

Jay Anderson's Great American Eclipse Weather Page

Joe Rao serves as an instructor and guest lecturer at New York's Hayden Planetarium. He writes about astronomy for Natural History magazine, the Farmer's Almanac and other publications, and he is also an on-camera meteorologist for Fios1 News based in Rye Brook, New York. Follow us @Spacedotcom, Facebook and Google+. Original article on Space.com.

Cassini-Huygens: Exploring Saturn's System

Cassini-Huygens: Exploring Saturn's System:

Artist's concept of NASA's Cassini spacecraft at Saturn.

Credit: NASA/JPL

The Cassini spacecraft has been orbiting Saturn since 2004. The mission is known for discoveries such as finding jets of water erupting from Enceladus, and tracking down a few new moons for Saturn. Now low on fuel, the spacecraft will make a suicidal plunge into the ringed planet in 2017 and capture some data about Saturn's interior on the way. (This will avoid the possibility of Cassini crashing someday onto a potentially habitable icy moon, such as Enceladus or Rhea.)

The ambitious mission is a joint project among several space agencies, which is a contrast from the large NASA probes of the past such as Pioneer and Voyager. In this case, the main participants are NASA, the European Space Agency and Agenzia Spaziale Italiana (the Italian space agency).

Development history

Cassini is the first dedicated spacecraft to look at Saturn and its system. It was named for Giovanni Cassini, a 17th-century astronomer who was the first to observe four of Saturn's moons — Iapetus (1671), Rhea (1672), Tethys (1684) and Dione (1684).

Before this spacecraft came several flybys of Saturn by Pioneer 11 (1979), Voyager 1 (1980) and Voyager 2 (1981). Some of the discoveries that came out of these missions included finding out that Titan's surface can't be seen in visible wavelengths (due to its thick atmosphere), and spotting several rings of Saturn that were not visible with ground-based telescopes.

It was shortly after the last flyby, in 1982, that scientific committees in both the United States and Europe formed a working group to discuss possible future collaborations. The group suggested a flagship mission that would orbit Saturn, and would send an atmospheric probe into Titan. However, there was a difficult "fiscal climate" in the early 1980s, NASA's Jet Propulsion Laboratory noted in a brief history of the mission, which pushed approval of Cassini to 1989.

The Europeans and the Americans each considered either working together, or working solo. A 1987 report by former astronaut Sally Ride, for example, advocated for a solo mission to Saturn. Called "NASA's Leadership and America's Future in Space," the report said that studying the outer gas giant planets (such as Saturn) help scientists learn about their atmospheres and internal structure. (Today, we also know that this kind of study helps us predict the structure of exoplanets, but the first exoplanets were not discovered until the early 1990s.)

"Titan is an especially interesting target for exploration because the organic chemistry now taking place there provides the only planetary-scale laboratory for studying processes that may have been important in the prebiotic terrestrial atmosphere," the report added, meaning that on Titan is chemistry that could have been similar to what was present on Earth before life arose.

Cassini's development came with at least two major challenges to proceeding. By 1993 and 1994, the mission had a $3.3 billion price tag (roughly $5 billion in 2017 dollars, or about half the cost of the James Webb Space Telescope.) Some critics perceived this as overly high for the mission. In response, NASA pointed out that the European Space Agency was also contributing funds, and added that the technologies from Cassini were helping to fund lower-cost NASA missions such as the Mars Global Surveyor, Mars Pathfinder and the Spitzer Space Telescope, according to JPL.

Cassini also received flak from environmental groups who were concerned that when the spacecraft flew by Earth, its radioisotope thermoelectric generator (nuclear power) could pose a threat to our planet, JPL added. These groups filed a legal challenge in Hawaii shortly before launch in 1997, but the challenge was rejected by the federal district court in Hawaii and the Ninth Circuit Court of Appeals.

To address concerns about the spacecraft's radioisotope thermoelectric generators, which are commonly used for NASA missions, NASA responded by issuing a supplementary document about the flyby and detailing the agency's methodology for protecting the planet, saying there was less than a one-in-a-million chance of an impact occurring.

Saturn's largest moon, Titan, passes in front of the planet and its rings in this true color snapshot from NASA's Cassini spacecraft. This view looks toward the northern, sunlit side of the rings from just above the ring plane. It was taken on May 21, 2011, when Cassini was about 1.4 million miles (2.3 million kilometers) from Titan.

Credit: NASA/JPL-Caltech/Space Science Institute

Launch and cruise

Cassini didn't head straight to Saturn. Rather, its mission involved complicated orbital mechanics. It went past several planets — including Venus (twice), Earth and Jupiter — to get a speed boost by taking advantage of each planet's gravity.

The nearly 12,600-lb. (about 5,700 kilograms) spacecraft was hefted off Earth on Oct. 15, 1997. It went by Venus in April 1998 and June 1999, Earth in August 1999 and Jupiter in December 2000.

Cassini settled into orbit around Saturn on July 1, 2004. Among its prime objectives were to look for more moons, to figure out what caused Saturn's rings and the colors in the rings, and understanding more about the planet's moons.

Perhaps Cassini's most detailed look came after releasing the Huygens lander toward Titan, Saturn's largest moon. The lander was named for Dutch scientist Christiaan Huygens, who in 1654 turned a telescope toward Saturn and observed that its odd blob-like shape — Galileo Galilei had first seen the shape in a telescope and drew it in his notebook as something like ears on the planet — was in fact caused by rings.

The Huygens lander descended through the mysterious haze surrounding the moon and landed on Jan. 14, 2005. It beamed information back to Earth for nearly 2.5 hours during its descent, and then continued to relay what it was seeing from the surface for 1 hour 12 minutes.

In that brief window of time, researchers saw pictures of a rock field and got information back about the moon's wind and gases on the atmosphere and the surface.

This first panorama of Titan released by ESA shows a full 360-degree view around the Huygens probe. The left-hand side shows a boundary between light and dark areas. The white streaks seen near this boundary could be ground 'fog', as they were not immediately visible from higher altitudes. Huygens drifted over a plateau (centre of image) and was heading towards its landing site in a dark area (right) during descent.

Credit: ESA/NASA/University of Arizona.

Magnificent moons

One of the defining features of Saturn is its number of moons. Excluding the trillions of tons of little rocks that make up its rings, Saturn has 62 discovered moons as of September 2012. NASA lists 53 named moons on one of its websites.

In fact, Cassini discovered two new moons almost immediately after arriving (Methone and Pallene) and before 2004 had ended, it detected Polydeuces. [Gallery: Latest Saturn Photos from NASA's Cassini Orbiter]

As the probe wandered past Saturn's moons, the findings it brought back to Earth revealed new things about their environments and appearances. Some of the more notable findings include:

Saturn has not gone ignored, either. For example, in 2012, a NASA study postulated that Saturn's jet streams in the atmosphere may be powered by internal heat, instead of energy from the sun. Scientists believe that heat brings up water vapor from the inside of the planet, which condenses as it rises and produces heat. That heat is believed to be behind jet stream formation, as well as that of storms.

Mission extension and end

Cassini was originally slated to last four years at Saturn, until 2008, but its mission has been extended multiple times. Its last and final leg was called the Cassini Solstice Mission, named because the planet and its moons reached the solstice again toward the mission end. Saturn orbits the sun every 29 Earth-years. With Cassini's mission lasting 13 years, this meant that the spacecraft observed almost half of Saturn's seasonal change as the planet went around its orbit.

In 2016, the spacecraft was set on a series of final maneuvers to provide close-up views of the rings, with the ultimate goal of plunging Cassini into Saturn on Sept. 15, 2017. This protected Enceladus and other potentially habitable moons from the (small) chance of Cassini colliding with the surface, spreading Earth microbe.

Major milestones of the finale included:

• Ring-grazing orbits: Every week between Nov. 30, 2016, and April 22, 2017, Cassini did loops around Saturn's poles to look at the outer edge of the rings, to learn more about their particles, gases and structure. It also observed small moons in this region, including Atlas, Daphnis, Pan and Pandora.
• On April 22, 2017, Cassini made the final flyby of Titan. The flyby was done in such a way to change Cassini's orbit so that it began 22 dives (once a week) between the planet and its rings. This was the first time any spacecraft explored this zone, and it entailed some risk because the orbit brought it between the outer part of the atmosphere and the inner zone of the rings (where it is at risk of striking particles or gas molecules). 
• On Sept. 15, 2017, Cassini will make a suicidal plunge into Saturn, taking measurements for as long as its instruments can make communications back to Earth.

Some of the science Cassini performed during this period included creating maps of the planet's gravity and magnetic fields, estimating how much material is in the rings, and taking high-resolution images of Saturn and its rings from close-up.

The spacecraft made an interesting discovery from its new vantage point. It found that Saturn's magnetic field is closely aligned with the planet's axis of rotation, which baffled scientists because of how they think magnetic fields are generated — through a difference of tilt between the magnetic field and a planet's rotation. As of late July 2017, however, scientists planned to gather more data to see if perhaps Saturn's internal processes confused their measurements.

Additional resource

How Astronomers Use Eclipses to Discover Alien Worlds

How Astronomers Use Eclipses to Discover Alien Worlds:

Artist's illustration of the star system Kepler-444, whose five planets were discovered by the Kepler space telescope as they passed in front of their star, dimming its light. All five orbit the star within less than 10 days.

Credit: Tiago Campante/Peter Devine

Paul Sutter is an astrophysicist at The Ohio State University and the chief scientist at COSI science center. Sutter leads science-themed tours around the world at AstroTouring.com. Sutter contributed this article to Space.com's Expert Voices: Op-Ed & Insights.

As we prepare for the upcoming total solar eclipse set to cross the continental United States on Aug. 21, the mechanics of the event are pretty straightforward to explain: Occasionally the sun, moon and Earth end up in straight line, and when they do, the moon casts its shadow on the Earth. Voila: eclipse!

From our perspective here on the surface of the Earth, it appears as if the disk of the moon covers the face of the sun. You have to be near or at totality — when the sun is fully covered — to notice the sun's dimming with your unaided eyes. However, sophisticated light-measuring instruments can easily pick up even the slightest hint of reduction in sunlight no matter the extent of the eclipse.

Now let's play a game. Let's say you attached these keen instruments to a telescope and you rocketed a few light-years away from the solar system. And instead of observing the sun-moon eclipse, you stared at the sun as the Earth meandered in its orbit. If you lined everything up just right and stared long enough, eventually you would get to see the tiny planet cross the face of its massive sun. [Total Solar Eclipse 2017: Here Are the Best Live-Video Streams to Watch]

With enough dedication to your astronomical duties, you could conceivably measure a dip in brightness as the Earth entered the edge of the sun, and a return to normalcy as the planet moved on.

Let's take it to the extreme: You're so far away that you can't even see a tiny dot representing the Earth. Could you still measure the telltale dip in brightness? Well, measuring the light output of a star is much easier than hunting for an insignificant speck of a rocky world, so I suppose with enough technological progress one could achieve it.

And imagine this: What if we did this all the time? Well, we do. This hunting for subtle eclipses is our primary method for detecting exoplanets — planets outside the solar system, orbiting their own host stars. Of course, astronomers don't call it "subtle eclipse method," but rather the "transit method."

This method allows us to find exoplanets big and small orbiting stars of all sizes and ages. Over 4,000 planets and counting! We haven't found an exact match for Earth yet — but we're getting closer to finding a match with every new planet detected.

The transit method isn't perfect, of course; it relies on a chance alignment among the star, the exoplanet and us. If that planet just happens to orbit perpendicular to our line of sight, we're out of luck. Thankfully, there are, to put it mildly, many stars out there, even within our nearby galactic neighborhood, so enough coincidences occur to give us a solid census of our celestial cousins.

So, as you're feasting your eyes on the upcoming solar eclipse, you might wonder if some distant observer is also enjoying the event.

Follow Paul @PaulMattSutter and facebook.com/PaulMattSutter. Follow us @Spacedotcom, Facebook or Google+. Originally published on Space.com.

Here's What It's Like to Be the Planetary Protection Officer at NASA

Here's What It's Like to Be the Planetary Protection Officer at NASA:

Credit: Reid Wiseman/NASA

If you want a job protecting Earth from threats from outer space — or even protecting Mars from us — NASA has an opening for you — sort of. The job of planetary protection officer generated quite a bit of buzz last week, when the public learned that a role seemingly out of a science fiction novel was actually a bonafide NASA job. But the position has nothing to do with protecting Earth from little green men, but a whole lot to do with important interplanetary science.

A primary task of the officer is to make sure that during NASA missions earthly microbes don't contaminate potentially habitable environments. And should a mission bring back samples from outer space, the officer is tasked with making sure that dust, or rocks, or whatever is brought back from outer space doesn't contaminate us.

John Rummel, a biology professor at East Carolina University, held the position twice, first between 1990 and 1993 and again from 1998 to 2006.

"The planetary protection job was mostly challenging in that it was not just important for each mission to do the right — required by requirements — thing, but to know why they were doing it, and why it was important to do a good job," Rummel said. "From that aspect, the job was definitely worth it. But as to 'rewards,' those were mostly internal.”

Rummel explained that the planetary protection office reports to the associate administrator for each mission, who oversees the cost of the project. That means recommendations made by the officer are often judged in the context of whether or not they will cost the administrator more money — a vexing problem many of us might easily understand from our own work experiences.

RELATED: The Mars Colony of the Future Could Be Powered by This Advanced Microgrid

Rummel's time as planetary protection officer coincided with the restart of NASA's Mars program.

After the successful twin Viking landings of the 1970s, a few famous searching-for-life experiments came up empty. NASA shifted its attention to other locations in the solar system, and Mars didn't get a launch opportunity until the failed Mars Observer mission in 1992.

A slew of missions followed, however, including the Mars Pathfinder mission that made it all the way to the surface in 1996 and deployed a mini-rover – Sojourner. Several other landing and orbiting missions followed — some successful, others not.

Those missions wouldn't have been possible without the approval of the planetary protection officer, who ensured that Sojourner and other Martian spacecraft were sterile enough to prevent microbes from taking root in potentially life-friendly areas. One of Rummel's first tasks in 1990 was to look at the risk of contamination on Mars and how scientific understanding had changed since the days of the Viking missions.

"I knew people would like to go back and land on Mars, but I also knew we didn't have current advice," Rummel said.

So he assisted in the drafting of a 1992 report – Biological Contamination of Mars. The report concluded that a large part of the surface was "extremely inhospitable to terrestrial life" and for that reason, future missions would not need to be sterilized as much as the Viking missions.

But changes in landing technology meant that NASA had to be extra mindful of different scenarios for its missions. Pathfinder, for example, was supposed to fall to the surface using airbags. If the airbags failed, the mission would need to withstand a fall and possible burial in the soil of up to 1.5 meters (5 feet) without exposing possible Earth microbes to the Martian environment.

NASA has seen extensive evidence of briny water flow in recurring slope lineae, which are features that develop on the slopes of craters. Rummel, among others, speculated about recurring slope lineae as early as 2002. While researchers have long observed the formations, it was only in 2015 that NASA had strong enough evidence to say the formations are probably due to liquid water on the surface.

Rummel warned against sending Curiosity to investigate a nearby recurring slope lineae. The materials on the rover's surface could not be thoroughly sterilized with UV radiation due to their properties. And inside the rover is a warm electronics box that could melt any ice with which the box comes into contact.

RELATED: NASA Center Shows Off Sleek New Mars Rover Concept Vehicle for Astronauts

Rummel was also part of early-stage planning for a "sample return" mission to bring pieces of Mars back to Earth, in collaboration with the French space agency CNES. While that mission never went forward, NASA has left the door open for future sample return missions. The next Mars rover, called Mars 2020, is expected to leave "caches" of interesting material behind for future missions to potentially pick up and bring back to Earth, when we presumably know a little more about how to protect ourselves.

Of course, Mars wasn't the only target of note back in the 1990s when Rummel began his work. NASA already had a Jupiter probe — called Galileo — and was about to launch Cassini, which has now been orbiting Saturn since 2004. Those missions confirmed some intriguing Voyager mission results from the 1970s and 1980s, showing that some of the moons are icy and potentially habitable.

Rummel remembers modifying the planetary protection plan for Galileo as evidence emerged that a liquid ocean might lie underneath Europa's icy surface.

At the end of Galileo's mission, an option was included to deliberately crash the probe into Io or Jupiter, just in case it happened to fall into Europa, damaging a potentially habitable environment underneath the ice. Because the mission planners were uncomfortable with changing Galileo's orbit to fall into Io, they went for a Jupiter extermination — collecting science all the way down.

NASA said the job posting has generated "a lot of excitement," including from Jack Davis a fourth grader from New Jersey and self-described "Guardian of the Galaxy." In a letter to the agency, Davis said he was fit for the job because his sister thought he was an alien, among other qualifications.

Although the planetary protection officer is no intergalactic warrior, it's a position that clearly provokes the imagination of skywatchers young and old.

Originally published on Seeker.

How to View a Solar Eclipse Without Damaging Your Eyes

How to View a Solar Eclipse Without Damaging Your Eyes:

The total solar eclipse of 2016 taken from a NASA webcast on March 8, 2016. The image was taken from Woleai Island in Micronesia. The next total solar eclipse will cross the entire continental U.S. on Aug. 21, 2017.

Credit: NASA TV

Editor's note: This story was originally posted on Feb. 2 and was updated on Aug. 19 with new resource links for eye safety during the 2017 total solar eclipse. 

We're just days away from the total solar eclipse of Aug. 21 and it's a good time for a refresher course on how to safely observe the event. Your parents probably told you to NEVER look directly at the sun with your naked eye. In fact, you've probably been told that by lots of reputable sources (including our own Space.com). But according to NASA and four other science and medical organizations, it's OK to look at a total solar eclipse with the naked eye — but only when the face of the sun is totally obscured by the moon.

A total solar eclipse happens when the central disk of the sun is completely covered by the moon. Many people have probably seen a partial solar eclipse, in which the disk of the moon appears to take a bite out of the sun's disk, but never fully obscures it. But total solar eclipses are a much rarer sight. And on Monday, a total solar eclipse will cross the continental U.S. from coast to coast.

A joint statement from NASA and the four other organizations says that with the right information, skywatchers can safely view the total solar eclipse in its full glory with the naked eye.

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Anyone in the United States on Aug. 21, 2017, will be able to see at least a partial solar eclipse (weather permitting, of course). But only those people in what's known as the "path of totality" will see a total solar eclipse. For the Aug. 21 eclipse, the path of totality is about 70 miles wide (112 kilometers), and extends from Oregon to South Carolina. Depending on where observers are located, the sun may be completely obscured by the moon for up to 2 minutes and 40 seconds.

The path of the total solar eclipse of 2017. Locations within the path of totality will experience up to 2 minutes and 40 seconds of darkness.

Credit: NASA


"During those brief moments when the moon completely blocks the sun's bright face … day will turn into night, making visible the otherwise hidden solar corona (the sun's outer atmosphere)," according to NASA's Eclipse website. "Bright stars and planets will become visible as well. This is truly one of nature's most awesome sights."

But in order to see this awesome natural sight, skywatchers need to know how to view the eclipse safely. In an effort to inform the public on this topic, an information guide on safe viewing has been written up and released by NASA, along with the American Astronomical Society (AAS), the American Academy of Ophthalmology, the American Academy of Optometry and the National Science Foundation.

Eye protection for looking at the sun

Looking directly at the sun without eye protection can cause serious eye damage or blindness. But there are ways to safely observe the sun. During a partial solar eclipse, people often use pinhole cameras to watch the progress of the moon across the sun's surface (pinhole cameras are easy to make at home). This is an "indirect" way of observing the sun, because the viewer sees only a projection of the sun and the moon.

To view the sun directly (and safely), use "solar-viewing glasses" or "eclipse glasses" or "personal solar filters" (these are all names for the same thing), according to the safety recommendations from NASA. The "lenses" of solar-viewing glasses are made from special-purpose solar filters that are hundreds of thousands of times darker than regular sunglasses, according to Rick Fienberg, press officer for the American Astronomical Society (AAS). These glasses are so dark that the face of the sun should be the only thing visible through them, Fienberg said. Solar-viewing glasses can be used to view a solar eclipse, or to look for sunspots on the sun's surface.

But beware! NASA and the AAS recommend that solar-viewing or eclipse glasses meet the current international standard: ISO 12312-2. Some older solar-viewing glasses may meet previous standards for eye protection, but not the new international standard, Fienberg said.

"Manufacturers that meet this standard include Rainbow Symphony, American Paper Optics and Thousand Oaks Optical," according to the information sheet on safe eclipse viewing. (Click any of the company links to find out how to purchase eclipse glasses). "Homemade filters or ordinary sunglasses, even very dark ones, are not safe for looking at the sun."

Fienberg said some manufacturers are making solar-viewing glasses with plastic frames, rather than the traditional paper frames. While these may look like regular sunglasses, do not be mistaken. Sunglasses are never a substitute for solar-viewing glasses. Fienberg said some people may even try to view the sun through two or three pairs of sunglasses in an attempt to replicate the protective power of real solar-viewing glasses; however, even multiple pairs of sunglasses will not protect your eyes from sun damage.

Telescopes, cameras, binoculars and other optical devices need their own solar filters. Solar-viewing glasses are not a substitute for a proper solar filter on magnification devices. Never view the disk of the sun through a telescope, binoculars or camera without a proper solar filter. Solar-viewing glasses are not powerful enough to protect your eyes from magnified sunlight. Even if you are wearing solar-viewing glasses, viewing the disk of the sun through a magnification device will result in serious eye damage if the device is not equipped with a proper solar filter, according to the viewing safety sheet.

"The concentrated solar rays will damage the filter and enter your eye(s), causing serious injury," according to the safety recommendations. "Seek expert advice from an astronomer before using a solar filter with a camera, a telescope, binoculars, or any other optical device."

Fienberg said there is no need for skywatchers to use a telescope during the eclipse, but a pair of binoculars can be helpful during totality. But, as per the recommendations, do not attempt to look at the disk of the sun through binoculars, even with solar-viewing glasses.

The safety sheet offers these tips regarding solar filters/eclipse glasses/solar viewers:

• Always inspect your solar filter before use; if scratched or damaged, discard it. Read and follow any instructions printed on or packaged with the filter. Always supervise children using solar filters. 
• Stand still and cover your eyes with your eclipse glasses or solar viewer before looking up at the bright sun. After glancing at the sun, turn away and remove your filter — do not remove it while looking at the sun. 
• Do not look at the uneclipsed or partially eclipsed sun through an unfiltered camera, telescope, binoculars or other optical device.

Safety during totality

Now that you have some general information about how to view the sun safely, here are NASA and the AAS's recommendations for how to safely view the total solar eclipse with the naked eye. Again, these tips come from NASA's safety information sheet here.

Viewers who are looking at the eclipse with solar-viewing glasses will be able to see when the sun's face is completely obscured by the moon (because, once again, the only light that can penetrate these solar-viewing glasses is the light from the sun's disk). Viewers will be able to observe the moon creep slowly over the sun's disk and eventually cover the sun entirely.

In the moments before totality, viewers looking through their solar-viewing glasses will see a crescent of light from the sun growing thinner and thinner as the moon progresses over its face. In the last few seconds just before the disk of the sun is entirely covered by the moon, the crescent will break up into a series of small dots of light that look like beads on a string (typically there are about three to eight such dots, according to Fienberg). These are called Baily's beads (after Francis Baily, the British astronomer who discovered them). Once the last bead disappears, the face of the sun has been covered by the moon, and totality has begun. [Solar Eclipses: An Observer's Guide (Infographic)]

"If you are within the path of totality, remove your solar filter only when the moon completely covers the sun's bright face," according to the official safety information sheet.

This image from NASA shows that the only time it is safe to remove your eye protection during a total solar eclipse is when the disk of the sun is entirely covered by the moon.

Credit: NASA


The safety information sheet also recommends that viewers be aware of another drastic change that takes place during a total solar eclipse: light levels drop dramatically, as if the world has suddenly been plunged into dusk. This is one indicator that totality has begun, and it is safe to take off your eclipse glasses.

When should you put your glasses back on? The official recommendations from the agencies suggest that viewers put their solar-viewing glasses back on before any part of the sun's disk becomes visible again.

"Experience totality, then, as soon as the bright sun begins to reappear, replace your solar viewer to glance at the remaining partial phases," the information sheet said.

In order to anticipate when the disk of the sun will reappear, viewers should first be aware of about how long the total eclipse should last where they are standing — the total eclipse will last, at most, about 2 minutes and 40 seconds. The nearer that viewers are to the edge of the path of totality, the shorter the total eclipse will be. Viewers who want to observe the total solar eclipse with the naked eye should try to move closer to the center of the path, so there is ample time to observe the eclipse safely.

Fienberg said that viewers should be aware of the moon moving across the surface of the sun during totality. The side of the sun that was the last to disappear behind the moon will be opposite to the side that is first to reappear. On the side of the moon where the sun will reappear first, viewers should look out for the "reddish hue" of the chromosphere, the layer of the sun's atmosphere that is closest to its surface. The sun will begin to reappear just as it disappeared — first as dots of light. If a dot of sunlight appears on the edge of the moon, it means totality is complete.

Baily's beads and diamond rings

The AAS and NASA are expecting huge crowds to flock to the path of totality for the 2017 total solar eclipse, including more experienced eclipse watchers. These seasoned observers may start shouting "Baily's beads!" when the spots of light appear at the edge of the moon. As the eclipse nears totality, people may also shout "Diamond ring!" Fienberg explains that when only one "bead" is still visible at the edge of the moon just before totality, it will glow like a diamond, and the red corona of the sun will create a circular band of light. Together, they will look like a diamond ring.

Experienced observers may decide to look at the eclipse with the naked eye just before the sun is completely covered by the moon, when the diamond ring appears.

"If you're in a group you'll hear people start screaming 'Diamond ring! Diamond ring! Filters off!'" Fienberg said. "If you're paying strict attention to the recommendation that you should not look at the sun without a filter, when any part of the bright face is still visible, you'll wonder if all those people are going blind, but they're not. The reason they're not is because it only lasts a second or so, and then it's gone and you see the corona, and its dark and its spectacular and beautiful."

While you may see some people removing their solar-viewing glasses before the eclipse reaches totality, this is not recommended by the official eclipse-viewing guide from NASA and the AAS.

What you'll see during a total solar eclipse

While Fienberg is adamant about eclipse-viewing safety, he is equally insistent that skywatchers should view the total solar eclipse with the naked eye, because the experience is like nothing else on Earth.

The sun's atmosphere "is always there but we can't see it," Fienberg said. "Satellites in orbit that block out the bright disk of the sun can see it, but from ground, we don't see it except during totality. And it is just magnificently beautiful. It's awesome in the truest sense of the word. It just makes your jaw drop. The first time you see it you just can't believe how beautiful it is. And it brings tears to people's eyes."

This composite image captures close to what the human eye sees during a total solar eclipse. The ribbons of light are the sun's atmosphere, which is controlled by the magnetic field.

Credit: NASA/S. Habbal, M. Druckmüller and P. Aniol


The sun's atmosphere isn't a uniform haze like the Earth's atmosphere, Fienberg said. It's "a tangle of streamers and jets and loops and twists and all kinds of stuff because its controlled entirely by the sun's magnetic field, which is very tangled and twisted."

The chromosphere, the atmosphere closest to the sun's surface, "is an unbelievably beautiful, pure magenta-red color. If the chromosphere is active and there are eruptions going on on the edge of the sun, you'll see prominences — they look like flames or jets of this really beautiful hot-pink magenta gas that are extending out beyond the silhouette of the moon," he said.

None of these features will be visible to viewers wearing eclipse glasses.

Fienberg is an eclipse chaser; he has traveled all over the world to see total solar eclipses. On his very first eclipse-viewing trip, before seeing the event, he met a man who hosted a music radio show in the city where Fienberg lives. The radio host was an eclipse chaser, and Fienberg said he'd never heard the host talk about astronomy on his show.

"I'm not interested in astronomy," the man told Fienberg. "I'm interested in beauty."

"That that told me right then on my first trip, this isn't just about astronomy," Fienberg said. "This is about beauty. This about being out in nature and being one with the universe — I mean it sounds silly! But you really feel like you're just part of it all and you're privileged to be able to see such a beautiful thing."

The unified message from Fienberg, NASA, the AAS and many other sources regarding the upcoming eclipse: Observe safely, and get to the path of totality on Aug. 21, 2017!

Follow Calla Cofield @callacofield. Follow us @Spacedotcom, Facebook and Google+. Original article on Space.com.

NASA's Parker Probe Will Explore The Sun's Hellish Atmosphere in 2018

NASA's Parker Probe Will Explore The Sun's Hellish Atmosphere in 2018:

NASA's Parker Solar Probe will fly closer to the sun than any spacecraft in history, and help scientists unlock secrets of our nearest star.

Credit: Johns Hopkins University Applied Physics Laboratory

Paul Sutter is an astrophysicist at The Ohio State University and the chief scientist at COSI Science Center. Sutter leads science-themed tours around the world at AstroTouring.com. 

By now, with so little time left until a total solar eclipse crosses the U.S. from coast to coast on Monday (Aug. 21), skywatchers planning to attend the event should understand that it's dangerous to look directly at the sun with the unaided eye, even if it's almost entirely covered by the moon. Seriously, don't do it.

The intense radiation emitted by the sun at multiple wavelengths, from the infrared through the ultraviolet, heats and warms our little world, but even at a distance of 93 million miles (149 million kilometers) and through our thick atmosphere, it can damage our skin and eyes. And occasionally make it possible to cook eggs on the sidewalk, if you're the adventurous sort.

So, NASA is going to send a spacecraft closer than ever before, and hope to capture useful data before the probe…well, melts.

The Parker Solar Probe was named after astrophysicist Eugene Parker (and let me interrupt myself and take this opportunity to castigate NASA for missing the golden opportunity to christen it the Icarus). The mission is set to launch in the summer of 2018. The craft won't take long to start taking dips near the sun, coming within 3.7 million miles (6 million km) of the surface. That sounds like a pretty large distance, which might lead some people to think the probe isn't getting that close to the sun — but the spacecraft will experience the sun's inferno at a scale 520 times greater than us here on Earth.

That mission design will continuously dip the probe in and out of the danger zone, coming seven times closer to the sun than any spacecraft before it. That puts poor Parker squarely within the sun's corona, the poorly understood wispy outer layer of our star. The hope is that this Evel Knievel-inspired plan will help us unlock the mysteries of that outer layer.

How does the corona reach temperatures exceeding 3 million degrees Fahrenheit (6 million Celsius), despite extending so far from the relatively cool surface? How do charged particles emanating from the sun get accelerated to near-light speed before spilling out into the system as a continuous solar wind? How do magnetic fields twist and tangle to transfer such tremendous energies?

We currently just have fuzzy half-answers to the above questions, and it's only by taking direct measurements as close to the furnace as possible that we can make more progress in answering them.

If you're lucky enough to see totality during the upcoming eclipse, you'll get to witness the sun's corona for yourself. And starting next year, plucky little Parker will be soon swimming in that sweltering soup, bravely collecting data before it, too, succumbs to the flames.

Follow us @Spacedotcom, Facebook and Google+. Original article on Space.com.

NASA's Epic Voyager Mission at 40: Q&A with Lead Scientist Ed Stone

NASA's Epic Voyager Mission at 40: Q&A with Lead Scientist Ed Stone:

Voyager 1 image of Jupiter's volcanic moon Io, showing the active plume of a volcano called Loki. 

Credit: NASA/JPL/USGS

NASA's historic Voyager mission has now been exploring the heavens for four decades.

The Voyager 2 spacecraft launched on Aug. 20, 1977, a few weeks before its twin, Voyager 1. Together, the two probes conducted an unprecedented "Grand Tour" of the outer solar system, beaming home up-close looks at Jupiter, Saturn, Uranus, Neptune and many of the moons of these giant planets.

This work revealed a jaw-dropping diversity of worlds, fundamentally reshaping scientists' understanding of the solar system. And then the Voyagers kept on flying. In August 2012, Voyager 1 became the first spacecraft ever to reach interstellar space — and Voyager 2 is expected to arrive in this exotic realm soon as well. [Voyager at 40: 40 Photos from NASA's Epic 'Grand Tour' Mission]

Ed Stone has served as Voyager project scientist since the mission's inception back in 1972. Space.com recently caught up with Stone, who talked about the 40-year anniversary, Voyager's greatest accomplishments and the mission's legacy.

Space.com: How does this 40-year milestone make you feel? What are your biggest impressions?

Voyager project scientist Ed Stone discusses the mission at NASA Headquarters in Washington, D.C., in April 2011.

Credit: NASA/Carla Cioffi


Ed Stone: It's amazing that the two spacecraft are still working after 40 years. When we launched, the Space Age itself was only 20 years old, so this is an unparalleled journey, and we're still in the process of discovering what's out there. Voyager 1 is out there in interstellar space; Voyager 2 is still inside, and we're seeing what's happening to the solar wind as it approaches interstellar space.

Space.com: Do you have an idea of when Voyager 2 will pop free into interstellar space?

Stone: Voyager 1 actually left the heliosphere in the nose region — that is, the region that faces into the interstellar wind, so that's the shortest way out. Voyager 2 is off to the flank of where the wind direction is, so the distance will be different. We don't know exactly how much different, because the models are not accurate enough to tell us that. But we can kind of estimate it from what Voyager 1 saw as it was approaching the boundary, the heliopause, and that suggests maybe several [more] years.

Space.com: What has Voyager 1 taught us about interstellar space so far?

Stone: It's really telling us how the interstellar wind interacts with the solar wind. Each star has wind blowing radially out from it. In the case of the sun, it's called the solar wind; it's the atmosphere of the sun speeding away in a million-mile-per-hour wind, which creates a bubble around the heliosphere. The bubble's size is determined by how much pressure there is from the interstellar wind outside, which came from explosive supernovae.

So there's a big difference between being inside, where the wind is from the sun and the magnetic field is from the sun, and being outside, where the wind is from the explosion over millions of years of supernovae, and where the magnetic field is the magnetic field of the Milky Way galaxy itself. [Voyager 1's Road to Interstellar Space: A Photo Timeline]

Another thing we've learned is how intense the cosmic radiation is out there. Cosmic rays are the nuclei of atoms that were accelerated by supernova explosions to nearly the speed of light. The fastest ones can easily get in to Earth; they were discovered here over 100 years ago. But the slower ones, the ones that are moving only 5 percent the speed of light or less, can't get in. And so we had no idea what the intensity of the cosmic radiation was outside the bubble.

We now know. The amount that gets in depends on the solar cycle, but we can say that less than a quarter of what's outside gets in. So the heliosphere is basically a radiation shield for all the planets, because it can exclude three-quarters of what's outside from getting in. We'll continue to monitor those cosmic rays now that we're out there, and we expect that Voyager 2 will find exactly the same story. If it doesn't, that will be a major surprise, because we think it's a pretty uniform environment now that we're outside.

Space.com: That was one of the mission's biggest accomplishments, obviously — reaching interstellar space and studying the environment there. Which of Voyager's other achievements stand out to you? Do you have any favorites?

Stone: Yes, I have a lot of favorites, actually! But I always like to think of Io, because it really set the stage for what was ahead. Io is a moon of Jupiter, and it's about the size of our moon. Before Voyager, the only known active volcanoes were here on Earth. And then we flew by Io with Voyager 1 and discovered eight erupting volcanoes — 10 times the volcanic activity of Earth, on this small moon. And it really set the stage for the fact that we were on a mission of discovery; we hadn't imagined the sorts of things we would be seeing.

Another one: In orbit around the same planet is Europa, which has an icy crust. It's again about the size of our moon. There are no volcanoes on Europa, but it has an icy crust which is cracked and certainly suggested that there could be a liquid-water ocean beneath. And again, before Voyager, the only oceans that were known were right here on Earth. It turned out, when [NASA's] Galileo [spacecraft] returned some years later and orbited [Jupiter] a number of times — it was able to show there was indeed a water ocean beneath the icy crust. [Photos: Europa, Mysterious Icy Moon of Jupiter]

Those are sort of two that kicked off the journey. Then we flew by Saturn, and its [biggest] moon Titan. Again, the only nitrogen atmosphere that we'd found in the solar system up until then was here on Earth. And yet, when we got to Titan, it has an atmosphere which is 1.5 times the pressure of the atmosphere on Earth — higher pressure, denser and much colder, of course. It may in some important ways resemble what the Earth's atmosphere was like before life evolved and created the oxygen that we all breathe.

Space.com: Are there any other surprises that really jumped out at you?

Stone: Well, before Voyager, all the magnetic fields seen at planets were like the Earth's magnetic field. That is, the magnetic pole is near the rotational pole of a planet. That was, we thought, because the magnetic field is created by the rotation of the liquid material beneath a planet's surface; therefore, the alignment seemed quite reasonable. And then we flew by Uranus and found its magnetic pole was nearer the equator than it was to the pole of rotation. And the same came true at Neptune. So this was not just an accident; in fact, these giant planets can have magnetic fields quite distinctly different in their orientation than what we had found at Jupiter and Saturn and Earth and Mercury.

Space.com: So, we're at 40 years now. How much longer will the Voyagers be able to keep gathering data and beaming it home to Earth?

Stone: The power supply is the natural radioactive decay of plutonium-238, which creates heat, and that is converted to electricity with thermocouples. So we can predict fairly accurately how much power we have, and how much less power we'll have each year, because of radioactive decay — it's decaying away. Every year now, we're in a mode where we have to turn off something that uses 4 watts, because we will have 4 watts less next year than we have this year. We have about 10 years or so of power remaining until we have only enough to power the spacecraft itself, without any of the instruments. That's on the order of 10 years from now.

But even after we no longer have power to send any data back to Earth, the two Voyager spacecraft will continue their orbit around the Milky Way, around the center of the galaxy with all the stars. Every 225 million years, they will complete another orbit around the Milky Way. And they will be doing that for billions of years, long after the Earth has been enveloped by the red giant sun. They'll be our silent ambassadors, with messages about where the place was that sent them so many billions of years earlier. [Photos from NASA's Voyager 1 and 2 Probes]

Credit: Karl Tate, SPACE.com


Space.com: Can you imagine life without Voyager at this point? Or is it just such a part of you that it's impossible to place yourself in an existence that doesn't involve Voyager?

Stone: Voyager's been at the center of my career, that is for sure. And it has allowed me to work on other projects, other missions. We've just finished and delivered an instrument for the Parker Solar Probe, which will launch in July of next year. That's the probe that will drop in near the sun, step by step, getting closer and closer. It's really exciting — that's what I call the inner frontier. It's where the solar wind begins.

Space.com: How do you think future generations will remember Voyager? What will the mission's main legacy be?

Stone: I think what Voyager has done is reveal how diverse the planets and the moons and the rings, and the magnetic fields of the planets, are. Our terracentric view was just much narrower than, in fact, reality. And now, of course, we know about planetary systems around other stars. There are many of them out there, and we have not found any that look like this one. So once again, it even expands the variability and diversity of what there is to be learned.

I'm hoping that, although it's not clear that we can ever send a spacecraft to one of these other systems, we can certainly improve our capabilities to observe them and study them and search for any evidence that perhaps at least microbial life has evolved on at least some of those planets, as it has here on Earth.

Follow Mike Wall on Twitter @michaeldwall and Google+. Follow us @Spacedotcom, Facebook or Google+. Originally published on Space.com.