SUPERNOVA - Rebel Supernova Formed in 'Heavy Metal' Galaxy

Rebel Supernova Formed in 'Heavy Metal' Galaxy:

An artist's impression of SN 2017egm showing the superluminous supernova's power source. The ultrabright explosion came when a massive star collapsed to form a rapidly-spinning neutron star with an extremely strong magnetic field, called a magnetar. Debris from the supernova is in blue, and the magnetar is in red.

Credit: M. Weiss/CfA

The most powerful exploding stars are popping up in unexpected places, new research indicates. It turns out that these superbright "rebel" supernovas can form in "heavy metal" areas, using elements heavier than hydrogen and helium, scientists said in the new study.

Supernovas happen when huge stars run out of fuel and collapse, creating an explosion that can briefly outshine their host galaxy. Thousands of supernovas have happened in the past decade, but only about 50 of them were "superluminous," meaning they were 100 times brighter than usual supernovas.

New research zeroes in on one supernova, called SN 2017egm, which exploded May 23 within view of the European Space Agency's Gaia satellite, which monitors star positions. If it had exploded in the Milky Way, it would have appeared as bright as the full moon does from Earth, researchers said in a statement. [Supernova Photos: Great Images of Star Explosions]

In fact, SN 2017egm was not only superluminous, but superclose: At just 420 million light-years away, it was three times closer than any other observed supernova of its type.

More strangely, the supernova exploded in a spiral galaxy with a high concentration of elements heavier than hydrogen and helium. (These elements are called "metals" in astronomy.) Before this, researchers had found superluminous supernovas in dwarf galaxies, which have low metal content, according to the statement.

This work marks the first time astronomers have identified a superluminous supernova that exploded in a large spiral galaxy, and in a metal-rich area. So when it comes to forming these explosions, a lack of metals may not be as important as astronomers had thought.

"Superluminous supernovas were already the rock stars of the supernova world," Matt Nicholl, lead author of the study and an astronomer at the Harvard-Smithsonian Center for Astrophysics in Cambridge, Massachusetts, said in the statement. "We now know that some of them like heavy metal, so to speak, and explode in galaxies like our own Milky Way."

The researchers also investigated what makes SN 2017egm so bright. They concluded that the supernova may be powered by a rapidly spinning dead star called a magnetar. Such ultradense, spinning neutron stars created by supernovas could continue to generate magnetic power that would heat up the expanding gas left over from the supernova.

SN 2017egm shares magnetar properties with other superluminous supernovas, but the researchers noted that the newly discovered supernova does have some differences.

For example, SN 2017egm might have ejected less mass than its supernova counterparts because its massive star might have shed mass before exploding. Also, the spin rate of SN 2017egm's magnetar may be slower than usual.

The supernova is currently invisible to astronomers because it is too close to the sun, but it will re-emerge on Sept. 16 after more than two months of obscurity.

"This should break all records for how long a superluminous supernova can be followed," Raffaella Margutti, study co-author and an astronomer at Northwestern University, said in the statement. "I'm excited to see what other surprises this object has in store for us."

The research was accepted for publication in The Astrophysical Journal Letters, and it is available online at arXiv.org. Nicholl's team studied the supernova on June 18 with the 60-inch (152 centimeters) telescope at the Smithsonian Astrophysical Observatory's Fred Lawrence Whipple Observatory in Arizona.

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

Cameras on NASA Exoplanet Spacecraft Slightly Out of Focus

Cameras on NASA Exoplanet Spacecraft Slightly Out of Focus:

NASA's Transiting Exoplanet Survey Satellite will fly in a unique highly-elliptical orbit to search for exoplanets around the nearest and brightest stars.

Credit: NASA

WASHINGTON — Cameras recently installed on a NASA spacecraft designed to look for nearby exoplanets will be slightly out of focus once launched, but the agency said that will not affect the mission's science.

NASA confirmed July 26 that the focus of the four cameras on the Transiting Exoplanet Survey Satellite (TESS) spacecraft will drift when the spacecraft cools to operating temperatures after launch next March. The problem was noticed in recent tests when the cameras were chilled to approximately minus 103 degrees Fahrenheit (minus 75 degrees Celsius).

"Recent tests show the cameras on TESS are slightly out of focus when placed in the cold temperatures of space where it will be operating," NASA spokesperson Felicia Chou said in response to a SpaceNews inquiry. "After a thorough engineering evaluation, NASA has concluded TESS can fully accomplish its science mission with the cameras as they are, and will proceed with current integration activities." [Gallery: The Strangest Alien Planets]

Chou added July 28 that the out-of-focus area is limited to the outer edges of the image, and that "recent testing shows that the camera focus towards the image center is better than originally designed."

The problem with the TESS cameras came up during a July 24 meeting of the NASA Advisory Council science committee in Hampton, Virginia. Alan Boss, an astronomer with the Carnegie Institution, brought up the issue in a summary of a meeting of the Astrophysics Advisory Committee, of which he is a member.

"That could have some big effects on the photometry," he said of the focus problem. "This is certainly a concern for the folks who know a lot about photometry."

TESS will use those cameras to monitor the brightness of the nearest and brightest stars in the sky, an approach similar to that used by Kepler, a NASA spacecraft developed originally to monitor one specific region of the sky. Both spacecraft are designed to look for minute, periodic dips in brightness of those stars as planets pass in front of, or transit, them.

In a photo posted to Twitter July 25, technicians pose with the four cameras that will be installed on the TESS spacecraft.

Credit: NASA



Chou said that since TESS is designed to conduct photometry, measuring the brightness of the stars in its field of view, "resolution is less important compared to imaging missions like Hubble." However, astronomers are concerned that there will be some loss of sensitivity because light from the stars will be spread out onto a slightly larger area of the detector.

"The question is how much science degradation will there be in the results," Boss said. "The TESS team thinks there will be a 10 percent cut in terms of the number of planets that they expect to be able to detect."

Despite the reduction, Boss said TESS scientists believe they will still be able to meet the mission's primary science requirements, and thus there is no need to fix the cameras. The four cameras were attached this week to a plate that will later be installed on the spacecraft, which is being assembled by Orbital ATK.

"There will be some loss of science, and we just want to know more about it," Boss said. That includes anything the project can do in software, or even mechanical fixes to the spacecraft, to compensate for the focus problem.

NASA has not disclosed the cause of the focus problem, but Boss said it may be due to crystallization of the glue used to bond the detector arrays in place. He said project engineers didn't expect the focus to continue to drift after the temperature stabilized.

Chou said the project will continue to monitor the problem. "Should further testing reveal the cameras are unable to complete the mission, NASA will revisit the decision and determine the steps moving forward," she said.

TESS is scheduled to launch no earlier than March 2018 on a SpaceX Falcon 9 rocket. That launch was previously planned for late 2017 but postponed by delays in SpaceX's launch schedule and the NASA launch certification process.

TESS will operate in a unique orbit that takes it between 67,000 miles and 232,000 miles (108,000 and 373,000 kilometers) from Earth. The orbit is particularly stable, thus minimizing the maneuvers the spacecraft has to perform to maintain it.

The spacecraft will have a two-year primary mission, and scientists expect it to detect thousands of exoplanets, including dozens the size of the Earth. Astronomers plan to follow up some of the most promising discoveries with the James Webb Space Telescope and the Wide Field Infrared Survey Telescope.

This story was provided by SpaceNews, dedicated to covering all aspects of the space industry.

ALIENS ? UFOS ? Want to Protect Earth from Aliens? NASA Is Hiring

Want to Protect Earth from Aliens? NASA Is Hiring:

Mars as seen by NASA’s Viking 1 orbiter.

Credit: NASA/JPL

If you've always dreamed of helping keep Earth safe from alien invaders, your ship may have just come in.

NASA is looking to hire a planetary protection officer, a person who will lead the agency's efforts to keep its spacecraft and astronauts from contaminating worlds with life-forms that don't belong there.

NASA officials have stressed that keeping Earth clean — of alien microbes that could arrive here in a sample-return capsule, for example — is the highest priority, but the responsibility applies to all celestial objects that agency spacecraft visit.

"NASA maintains policies for planetary protection applicable to all spaceflight missions that may intentionally or unintentionally carry Earth organisms and organic constituents to the planets or other solar system bodies, and any mission employing spacecraft which are intended to return to Earth and its biosphere with samples from extraterrestrial targets of exploration," NASA officials wrote in a job description. "This policy is based on federal requirements and international treaties and agreements."

So the job checks the making-a-difference box. The pay is good, too; the stated salary range is $124,406 to $187,000. And if you're after a challenge, you'll almost certainly get it.

The topic of planetary protection is generating more and more discussion these days as NASA works on getting (microbe-laden) astronauts to Mars and sending robotic probes to potentially habitable worlds, such as Jupiter's ocean-harboring moon Europa. (The agency is scheduled to launch a Europa flyby mission in the 2020s, and Congress has instructed NASA to put a lander down on the moon's icy surface as well.)

Such plans have spurred debate within the spaceflight community, with some exploration advocates stressing that planetary-protection concerns could hinder the effort to put boots on Mars and hunt for life on the Red Planet.

Still interested? You have until Aug. 14 to apply (which you can do here).

This is not a newly created job; Cassie Conley has been NASA's planetary protection officer for several years now. The new posting is a result of relocating the position to NASA's Office of Safety and Mission Assurance, Conley told Business Insider. She did not indicate whether she plans to reapply, Business Insider reported.

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

Company Loses Contact With Communications Satellite While Changing Orbit

Company Loses Contact With Communications Satellite While Changing Orbit:

AGI's Commercial Space Operations Center (ComSpOC) is tracking EchoStar-3 drifting at a rate of 0.1 degree per day in geostationary orbit.

Credit: AGI

WASHINGTON — A 20-year old satellite in fleet operator EchoStar's constellation is drifting after an anomaly the company said has crippled communications.

Englewood, Colorado-based EchoStar said EchoStar-3 "experienced an anomaly of unknown origin" during a relocation maneuver last week "that has caused communications with the satellite to be interrupted and intermittent."

Built by Lockheed Martin and launched in 1997 on an Atlas 2AS rocket, the satellite was operating five years past its design life, and had been placed in a fuel-saving inclined orbit for the past three-plus years, EchoStar said.

"EchoStar has received FCC authority for its current flight configuration, and we are working in cooperation with the satellite manufacturer to re-establish a reliable link in order to recover and retire the spacecraft," Derek de Bastos, EchoStar Satellite Services chief technology officer, said in an Aug. 2 statement. "In spite of the anomaly, we believe that the current EchoStar III orbit does not present a significant risk to the operating satellites in the geostationary arc."

ComSpOC, a commercial space situational awareness facility run by Exton, Pennsylvania-based Analytical Graphics Inc., has been tracking EchoStar-3 drifting westward along the geostationary arc at a rate of 0.1 degrees per day from 87.2 degrees west. The out-of-commission satellite follows SES's AMC-9 satellite that experienced an anomaly the weekend of June 17 that also set it drifting. AGI's ComSpOC tweeted July 7 that AMC-9 was drifting westward at roughly 0.2 degrees per day.

EchoStar said EchoStar-3 "is a fully depreciated, non-revenue generating asset." The satellite provided broadcast services in Ku-band.

This story was provided by SpaceNews, dedicated to covering all aspects of the space industry.

THE SUN - Sunrise Through the Solar Arrays

Sunrise Through the Solar Arrays: On July 26, 2017, a member of the Expedition 52 crew aboard the International Space Station took this photograph of one of the 16 sunrises they experience every day, as the orbiting laboratory travels around Earth. One of the solar panels that provides power to the station is seen in the upper left.

Original enclosures:

ECLIPSE - A Total Eclipse at the End of the World

A Total Eclipse at the End of the World:

Discover the cosmos! Each day a different image or photograph of our fascinating universe is featured, along with a brief explanation written by a professional astronomer.

2017 July 30

A Total Eclipse at the End of the World

Image Credit & Copyright: Fred Bruenjes (moonglow.net)


Explanation: Would you go to the end of the world to see a total eclipse of the Sun? If you did, would you be surprised to find someone else there already? In 2003, the Sun, the Moon, Antarctica, and two photographers all lined up in Antarctica during an unusual total solar eclipse. Even given the extreme location, a group of enthusiastic eclipse chasers ventured near the bottom of the world to experience the surreal momentary disappearance of the Sun behind the Moon. One of the treasures collected was the featured picture -- a composite of four separate images digitally combined to realistically simulate how the adaptive human eye saw the eclipse. As the image was taken, both the Moon and the Sun peeked together over an Antarctic ridge. In the sudden darkness, the magnificent corona of the Sun became visible around the Moon. Quite by accident, another photographer was caught in one of the images checking his video camera. Visible to his left are an equipment bag and a collapsible chair. A more easily visible solar eclipse will occur in about three weeks and be visible from the USA.

Tomorrow's picture: surfing pluto

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PLUTO - Pluto Flyover from New Horizons

Pluto Flyover from New Horizons:

Discover the cosmos! Each day a different image or photograph of our fascinating universe is featured, along with a brief explanation written by a professional astronomer.

2017 July 31


Pluto Flyover from New Horizons

Credit: NASA, JHUAPL, SwRI, P. Schenk & J. Blackwell (LPI); Music Open Sea Morning by Puddle of Infinity


Explanation: What if you could fly over Pluto -- what might you see? The New Horizons spacecraft did just this in 2015 July as it shot past the distant world at a speed of about 80,000 kilometers per hour. Recently, many images from this spectacular passage have been color enhanced, vertically scaled, and digitally combined into the featured two-minute time-lapse video. As your journey begins, light dawns on mountains thought to be composed of water ice but colored by frozen nitrogen. Soon, to your right, you see a flat sea of mostly solid nitrogen that has segmented into strange polygons that are thought to have bubbled up from a comparatively warm interior. Craters and ice mountains are common sights below. The video dims and ends over terrain dubbed bladed because it shows 500-meter high ridges separated by kilometer-sized gaps. Although the robotic New Horizons spacecraft has too much momentum ever to return to Pluto, it has now been targeted at Kuiper Belt object 2014 MU 69, which it should shoot past on New Year's Day 2019.

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Tomorrow's picture: sand shower

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Authors & editors: Robert Nemiroff (MTU) & Jerry Bonnell (UMCP)
NASA Official: Phillip Newman Specific rights apply.
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A service of: ASD at NASA / GSFC
& Michigan Tech. U.

METEORS IN TURKEY - Perseid Meteors over Turkey

Perseid Meteors over Turkey:

Discover the cosmos! Each day a different image or photograph of our fascinating universe is featured, along with a brief explanation written by a professional astronomer.

2017 August 1

Explanation: The Perseid Meteor Shower, usually the best meteor shower of the year, will peak late next week. A person watching a clear sky from a dark location might see a bright meteor every minute. These meteors are actually specks of rock that have broken off Comet Swift-Tuttle and continued to orbit the Sun until they vaporize in Earth's atmosphere. The featured composite image shows a outburst of Perseids as they appeared over Turkey during last year's meteor shower. Enough meteors were captured to trace the shower's radiant back to the constellation of Perseus on the far left. The tail-end of the Perseids will still be going during the total solar eclipse on August 21, creating a rare opportunity for some lucky astrophotographers to image a Perseid meteor during the day.

LUNAR ECLIPSE - A Partial Lunar Eclipse Ushers in Eclipse Season

A Partial Lunar Eclipse Ushers in Eclipse Season:

The partial lunar eclipse of June 4th, 2012. Credit: Dave Dickinson

Live on the wrong continent to witness the August 21^st total solar eclipse? Well… celestial mechanics has a little consolation prize for Old World observers, with a partial lunar eclipse on the night of Monday into Tuesday, August 7/8^th.

A partial lunar eclipse occurs when the Moon just nicks the inner dark core of the Earth’s shadow, known as the umbra. This eclipse is centered on the Indian Ocean region, with the event occurring at moonrise for the United Kingdom, Europe and western Africa and moonset/sunrise for New Zealand and Japan. Western Australia, southern Asia and eastern Africa will see the entire eclipse.

The path of the Moon through the Earth’s shadow Monday night. Credit: adapted from NASA/GSFC/Fred Espenak

The penumbral phase of the eclipse begins on August 7^th at 15:50 Universal Time (UT), though you probably won’t notice a slight tea colored shading on the face of the Moon until about half an hour in. The partial phases begin at 17:23 UT, when the ragged edge of the umbra becomes apparent on the southeastern limb of the Moon. The deepest partial eclipse occurs at 18:22 UT with 25% of the Moon submerged in the umbra. Partial phase lasts 116 minutes in duration, and the entire eclipse is about five hours long.

The viewing prospects for the partial lunar eclipse. Credit: NASA/GSFC/Fred Espenak.

This also marks the start of the second and final eclipse season for 2017. Four eclipses occur this year: a penumbral lunar eclipse and annular solar eclipse this past February, and this month’s partial lunar and total solar eclipse.

Eclipses always occur in pairs, or very rarely triplets with an alternating lunar-solar pattern. This is because the tilt of the Moon’s orbit is inclined five degrees relative to the ecliptic, the plane of the Earth’s orbit around the Sun. The Moon therefore misses the 30′ wide disk of the Sun and the 80′ – 85′ wide inner shadow of the Earth on most passes.

The partial lunar eclipse of April 26th, 2013. Image credit and copyright: Henna Khan

Fun fact: at the Moon’s 240,000 mile distance from the Earth, the ratio of the apparent size of the Moon and the shadow is approximately equivalent to a basketball and a hoop.

When celestial bodies come into alignment, however, things can get interesting. For an eclipse to occur, the nodes – the point where the Moon’s orbit intersects the ecliptic – need to align with the position of the Moon and the Sun. There are two nodes, one descending with the Moon crossing the ecliptic from north to south, and one ascending. The time it takes for the Moon to return to the same node (27.2 days) is a draconitic month. Moreover, the nodes are moving around the Earth due to drag on the Moon’s orbit mainly by the Sun, and move all the way around the zodiac once every 18.6 years.

Got all that? Let’s put it into practice with this month’s eclipses. First, the Moon crosses its descending node at 10:56 UT on August 8th, just over 16 hours after Monday’s partial eclipse. Two weeks later, however, the Moon crosses ascending node just under eight hours from the central conjunction with the Sun, and a total solar eclipse occurs.

Tales of the Saros

The August 7^th lunar eclipse is member number 62 of the 83 lunar eclipses in saros series 119, which started on October 14^th, 935 AD and will end with a final shallow penumbral eclipse on March 25^th, 2396 AD. If you witnessed the lunar eclipse of July 28^th, 1999, then you saw the last lunar eclipse in the same saros. Saros 119 produced its last total lunar eclipse on June 15^th, 1927.

The next lunar eclipse, a total occurs on January 31^st, 2018, favoring the Pacific rim regions.

Partial lunar eclipses have occasionally work their way into history, usually as bad omens. One famous example is the partial lunar eclipse of May 22^nd, 1453 which preceded the Fall of Constantinople to the Ottoman Turks by a week. Apparently, a long standing legend claimed that a lunar eclipse would be the harbinger of the fall of Byzantium, and the partially eclipsed Moon rising over the besieged city ramparts seemed to fulfill the prophecy.

In our more enlightened age, we can simply enjoy Monday’s partial lunar eclipse as a fine celestial spectacle. You don’t need any special equipment to enjoy a lunar eclipse, just a view from the correct Moonward facing hemisphere of the Earth, and reasonably clear skies.

See the curve of the Earth’s shadow? This is one of the very few times that you can see that the Earth is indeed round (sorry, Flat Earthers) with your own eyes. And this curve is true for observers watching the Moon on the horizon, or high overhead near the zenith.

This month’s lunar eclipse occurs in the astronomical constellation of Capricornus. The Moon will also occult the +5^th magnitude star 29 Capricorni for southern India, Madagascar and South Africa shortly after the eclipse.

The viewing footprint for the 29 Capricorni occultation shortly after the eclipse. Credit: Occult 4.2.

Finally, anyone out there planning on carrying the partial lunar eclipse live, let us know… curiously, even Slooh seems to be sitting this one out.

Update: we have one possible broadcast, via Shahrin Ahmad (@shahgazer on Twitter). Updates to follow!

The final eclipse season for 2017 is now underway, starting Monday night. Nothing is more certain in this Universe than death, taxes and celestial mechanics, as the path of the Moon now sends it headlong to its August 21^st destiny and the Great American Total Solar Eclipse.

-We’ll be posting on Universe Today once more pre-total solar eclipse one week prior, with weather predictions, solar and sunspot activity and prospects for viewing the eclipse from Earth and space and more!

-Read more about this year’s eclipses in our 2017 Guide to 101 Astronomical Events.

-Eclipse… science fiction? Read our original eclipse-fueled tales Exeligmos, Shadowfall, Peak Season and more!

The post A Partial Lunar Eclipse Ushers in Eclipse Season appeared first on Universe Today.

Kepler Spots the First Exomoon Candidate 4000 Light Years From Earth

Kepler Spots the First Exomoon Candidate 4000 Light Years From Earth:

Ever since it was deployed in March of 2009, the Kepler mission has detected thousands of extra-solar planet candidates. In fact, between 2009 and 2012, it detected a total of 4,496 candidates, and confirmed the existence of 2,337 exoplanets. Even after two of its reaction wheels failed, the spacecraft still managed to turn up distant planets as part of its K2 mission, accounting for another 521 candidates and confirming 157.

However, according to a new study conducted by a pair of researches from Columbia University and a citizen scientist, Kepler may also have also found evidence of an extra-solar moon. After sifting through data from hundreds of transits detected by the Kepler mission, the researchers found one instance where a transiting planet showed signs of having a satellite.

Their study – which recently published online under the title “HEK VI: On the Dearth of Galilean Analogs in Kepler and the Exomoon Candidate Kepler-1625b I” – was by led Alex Teachley, a graduate student at Columbia University and a Graduate Research Fellow with the National Science Foundation (NSF). He was joined by David Kippling, an Assistant Professor of Astronomy at Columbia University and the Principal Investigator of The Hunt for Exomoons with Kepler (HEK) project, and Allan Schmitt, a citizen scientist.

Artist’s impression of NASA’s Kepler spacecraft. Credit: NASA

For years, Dr. Kippling has been searching the Kepler database for evidence of exomoons, as part of the HEK. This is not surprising, considering the kinds of opportunities that exomoons present for scientific research. Within our Solar System, the study of natural satellites has revealed important things about the mechanisms that drive early and late planet formation, and moons possess interesting geological features that are commonly found on other bodies.

It is for this reason that extending that research to the hunt for exoplanets is seen as necessary. Already, exoplanet-hunting missions like Kepler have turned up a wealth of planets that challenge conventional ideas about how planet formation and what kinds of planets are possible. The most noteworthy example are gas giants that have observed orbiting very close to their stars (aka. “Hot Jupiters”).

As such, the study of exomoons could yield valuable information about what kinds of satellites are possible, and whether or not our own moons are typical. As Teachey told Universe Today via email:

“Exomoons could tell us a lot about the formation of our Solar System, and other star systems. We see moons in our Solar System, but are they common elsewhere? We tend to think so, but we can’t know for sure until we actually see them. But it’s an important question because, if we find out there aren’t very many moons out there, it suggests maybe something unusual was going on in our Solar System in the early days, and that could have major implications for how life arose on the Earth. In other words, is the history of our Solar System common across the galaxy, or do we have a very unusual origin story? And what does that say about the chances of life arising here? Exomoons stand to offer us clues to answering these questions.”

A montage of some of the potentially-habitable moons in our Solar System. From top to bottom, left to right, these include Europa, Enceladus, TItan and Ceres. Credit: NASA/JPL

What’s more, many moons in the Solar System – including Europa, Ganymede, Enceladus and Titan – are thought to host life in their interiors. This is due to the fact that these bodies have steady supplies of volatiles (such as nitrogen, water, carbon dioxide, ammonia, hydrogen, methane and sulfur dioxide) and possess internal heating mechanisms that could provide the necessary energy to power biological processes.

Here too, the study of exomoons presents interesting possibilities, such as whether or not they may be habitable or even Earth-like. For these and other reasons, astronomers want to see if the planets that have been confirmed in distant star systems have systems of moons and what conditions are like on them. But as Teachey indicated, the search for exomoons presents a number of challenges compared to exoplanet-hunting:

“Moons are difficult to find because 1) we expect them to be quite small most of the time, meaning the transit signal will be quite weak to begin with, and 2) every time a planet transits, the moon will show up in a different place. This makes them more difficult to detect in the data, and modeling the transit events is significantly more computationally expensive. But our work leverages the moons showing up in different places by taking the time-averaged signal across many different transit events, and even across many different exoplanetary systems. If the moons are there, they will in effect carve out a signal on either side of the planetary transit over time. Then it’s a matter of modeling this signal and understanding what it means in terms of moon size and occurrence rate.”

To locate signs of exomoons, Teachey and his colleagues searched through the Kepler database and analyzed the transits of 284 exoplanet candidates in front of their respective stars. These planets ranged in size from being Earth-like to Jupiter-like in diameter, and orbited their stars at a distance of between ~0.1 to 1.0 AU. They then modeled the light curve of the stars using the techniques of phase-folding and stacking.

An artist’s conception of a habitable exomoon. Credit: NASA

These techniques are commonly used by astronomers who monitor stars for dips in luminosity that are caused by the transits of planets (i.e. the transit method). As Headey explained, the process is quite similar:

“Basically we cut up the time-series data into equal pieces, each piece having one transit of the planet in the middle. And when we stack these pieces together we’re able to get a clearer picture of what the transit looks like… For the moon search we do essentially the same thing, only now we’re looking at the data outside the main planetary transit. Once we stack the data, we take the average values of all the data points within a certain time window and, if a moon is present, we ought to see some missing starlight there, which allows us to deduce its presence.”

What they found was a single candidate located in the Kepler-1625 system, a yellow star located about 4000 light years from Earth. Designated Kepler-1625B I, this moon orbits the large gas giant that is located within the star’s habitable zone, is 5.9 to 11.67 times the size of Earth, and orbits its star with a period of 287.4 days. This exomoon candidate, if it should be confirmed, will be the first exomoon ever discovered.

The team’s results (which await peer review) also demonstrated that large moons to be a rare occurrence in the inner regions of star systems (within 1 AU). This was something of a surprise, though Teachey acknowledges that it is consistent with recent theoretical work. According to what some recent studies suggest, large planets like Jupiter could lose their moons as they migrate inward.

If this should prove to be the case, then what Teachey and his colleagues witnessed could be seen as evidence of that process. It could also be an indication our current exoplanet-hunting missions may not be up to the task of detecting exomoons. In the coming years, next-generations missions are expected to provide more detailed analyses of distant stars and their planetary systems.

An artist’s conception of a distance exomoon blocking out a star’s light. Credit: Dan

However, as Teachey indicated, these too could be limited in terms of what they can detect, and new strategies may ultimately be needed:

“The rarity of moons in the inner regions of these star systems suggests that individual moons will remain difficult to find in the Kepler data, and upcoming missions like TESS, which should find lots of very short period planets, will also have a difficult time finding these moons. It’s likely the moons, which we still expect to be out there somewhere, reside in the outer regions of these star systems, much as they do in our Solar System. But these regions are much more difficult to probe, so we will have to get even more clever about how we look for these worlds with present and near-future datasets.”

In the meantime, we can certainly be exited about the fact that the first exomoon appears to have been discovered. While these results await peer review, confirmation of this moon will mean additional research opportunities for Kepler-1625 system. And the fact that this moon orbits within the star’s habitable zone could mean that it might be capable of sustaining life.

Hmm, a habitable moon orbiting a gas giant. Does that sound like something that might have come up in some science fiction movies?

Further Reading: arXiv



The post Kepler Spots the First Exomoon Candidate 4000 Light Years From Earth appeared first on Universe Today.

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MILKY WAY - As Much as Half of the Milky Way Likely Came From Distant Galaxies

As Much as Half of the Milky Way Likely Came From Distant Galaxies:

Credit: Kristin Samuelson/Northwestern University

We're made of star stuff, as Carl Sagan famously put it in his TV series Cosmos. All of the elements that joined together to form our planet and everything on it were set in motion within the hearts of ancient stars. But not only are we star stuff, it appears that we're actually made of alien star stuff.

Astrophysicists who were analyzing galaxy formation recently looked at how intergalactic gas and dust is transported over time and across great distances. They found that up to half of the matter in our Milky Way galaxy likely comes from other galaxies far, far away.

"Given how much of the matter out of which we formed may have come from other galaxies, we could consider ourselves space travelers or extragalactic immigrants," Daniel Anglés-Alcázar, an astrophysics postdoctoral fellow from Northwestern University who led the study, said in a statement. "It is likely that much of the Milky Way's matter was in other galaxies before it was kicked out by a powerful wind, traveled across intergalactic space and eventually found its new home in the Milky Way."

This is a "first-of-its-kind analysis," the team said, with the findings opening a new line of research into understanding galaxy formation. The study appears in the Monthly Notices of the Royal Astronomical Society.

Anglés-Alcázar and his fellow researchers used a supercomputer simulation based on the FIRE (Feedback in Realistic Environments) project, which is co-led by Northwestern physics and astronomy professor Claude-André Faucher-Giguère. FIRE uses numerical simulations that can produce realistic 3D models of galaxies. Anglés-Alcázar developed state-of-the-art algorithms to follow how a galaxy forms over time, from just after the Big Bang to the present day.

Using the equivalent of several million hours of continuous computing time, the team was able to quantify how galaxies acquire matter from the universe over time. They did this by "tracing cosmic inflows, galactic outflows, gas recycling, and merger histories," according to their paper.

The findings on galactic evolution were unexpected, and the researchers coined a new term to explain the phenomenon: intergalactic transfer.

RELATED: Cosmic Blast of X-rays Inexplicably Outshines All of a Galaxy's Stars

The simulations showed that supernova explosions within galaxies eject enormous amounts of gas, which causes atoms to be transported from one galaxy to another via powerful galactic winds. Even though galaxies are far apart from each other, the galactic winds propagate material at several hundred kilometers per second, and over several billion years this process infused new material into galaxies, sparking star formation.

"We show that in situ star formation fueled by fresh accretion dominates the early growth of galaxies of all masses, while the re-accretion of gas previously ejected in galactic winds often dominates the gas supply for a large portion of every galaxy's evolution," the team wrote. "Externally processed material contributes increasingly to the growth of central galaxies at lower redshifts."

By tracking in detail the complex flows of matter in the simulations, the research team found that gas flows from smaller galaxies to larger galaxies, such as the Milky Way, where the gas forms stars. Additionally, even stars formed in one galaxy could be transferred to another. This transfer of mass through galactic winds can account for up to 50 percent of matter in the larger galaxies, the researchers said.

"In our simulations, we were able to trace the origins of stars in Milky Way-like galaxies and determine if the star formed from matter endemic to the galaxy itself or if it formed instead from gas previously contained in another galaxy," said Anglés-Alcázar.

The accepted theory of galactic formation is that shortly after the Big Bang, the hydrogen, helium and other trace elements started to clump together due to small density fluctuations, perhaps from dark matter that that provided the initial gravitational attraction. Matter then bunched together into larger and larger collections, forming the first proto-galaxies.

RELATED: Young Galaxy's Old Stardust Sheds Light on the First Stars

Within these first galaxies, more clumps of material came together to eventually create the first stars. These stars lived short violent lives, ending in powerful supernovae that then seeded the next generations of stars. The first galaxies were gravitationally attracted to one other, and merged together into larger and larger structures, ultimately becoming the large spiral galaxies we know today.

But the intergalactic transfer of gas from other galaxies is "an important but previously under-appreciated growth mode," the researchers said, emphasizing that their study showed that galactic winds are a "primary contributor to the baryonic mass budget of central galaxies."

"This study transforms our understanding of how galaxies formed from the Big Bang," Faucher-Giguère remarked in a statement. "What this new mode implies is that up to one-half of the atoms around us — including in the solar system, on Earth and in each one of us — comes not from our own galaxy but from other galaxies, up to one million light-years away."

"Our origins are much less local than we previously thought," he added. "This study gives us a sense of how things around us are connected to distant objects in the sky."

Originally published on Seeker.

JUPITER - Wow! This Is What Jupiter's Great Red Spot Would Look Like to You

Wow! This Is What Jupiter's Great Red Spot Would Look Like to You:

This true-color image shows what Jupiter’s Great Red Spot would look like to a human observer from the position of NASA’s Juno Jupiter orbiter. Citizen scientist Björn Jónsson created the photo using data from Juno’s JunoCam imager.

Credit: NASA/JPL-Caltech/SwRI/MSSS/Björn Jónsson

If you'd been riding aboard NASA's Juno probe when it zoomed over Jupiter's famous Great Red Spot earlier this month, this is what you would have seen.

A newly released photo gives a dramatic look at that July 10 close pass, capturing Juno's view of the enormous storm from an altitude of just 8,648 miles (13,918 kilometers).

"This true-color image offers a natural-color rendition of what the Great Red Spot and surrounding areas would look like to human eyes from Juno's position," NASA officials wrote in an image description Thursday (July 27). "The tumultuous atmospheric zones in and around the Great Red Spot are clearly visible."

The image was created by citizen scientist Björn Jónsson using data collected by Juno's JunoCam imager. NASA encourages anyone who wishes to process JunoCam raw images to do so; go to www.missionjuno.swri.edu/junocam for more information.

The $1.1 billion Juno mission launched in August 2011 and arrived in orbit around Jupiter on July 4, 2016. The probe is zooming around the huge planet on a highly elliptical path, making close approaches, or "perijoves," once every 53.5 days.

Juno is investigating Jupiter's composition and interior structure, with the aim of helping scientists better understand the gas giant's formation and evolution. The probe collects most of its data during perijove passes like the July 10 event, seven of which it has completed so far (not counting the initial one on July 4 of last year, when Juno's science gear was turned off).

Juno's mission is scheduled to last until at least February 2018.

The Great Red Spot has been raging for centuries. The huge storm is about 10,000 miles (16,000 km) wide, meaning it's bigger than the entire Earth. However, it used to be even bigger; the Great Red Spot has long been shrinking, for reasons that scientists don't entirely understand.

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

BIG BANG ? Curious Kids: What Started the Big Bang?

Curious Kids: What Started the Big Bang?:

In the beginning, the Universe expanded very, very fast.

Credit: Flickr/Jamie, CC BY-SA

This is an article from Curious Kids, a series for children. The Conversation is asking kids to send in questions they'd like an expert to answer. All questions are welcome – serious, weird or wacky! The article was originally published at The Conversation. The publication contributed the article to Space.com's Expert Voices: Op-Ed & Insights.

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What started the Big Bang? – Pippi, 8, Canberra.

This is one of the two questions I get asked a lot (the other one is: do aliens exist?) Both are very good questions! Pippi, the short answer is that we do not know what started the Big Bang. This is a big mystery.

The Big Bang is an idea about the history of the Universe, the history of space and time and matter ("stuff") and energy. The Universe is about 13.8 billion years old and from observations we make using telescopes we can tell that the Universe was very small 13.8 billion years ago.

Observations also suggest that in the first fraction of a second, the Universe seemed to expand very quickly but then slow down. After a few hundred thousand years, the simplest type of atom formed: hydrogen. The hydrogen started to form stars and galaxies.

After billions of years the Earth (and us) formed from the atoms made inside stars - every atom in your body more complicated than hydrogen was made by a star at some point in the last 13.8 billion years. In all that time, the Universe has continued to expand. In fact, observations now tell us that the expansion of the Universe is getting faster.

The idea of the Big Bang agrees with all these observations. So scientists think the Big Bang is an idea that does a good job of describing the history of the Universe.

However, the idea is not perfect. We don't know why the Universe expanded so quickly in the first second and then slowed down. We don't know why the expansion of the Universe is speeding up now. We don't know why we have a certain number of forces that control the Universe. And we don't know what started the Big Bang!

Very large telescopes, like the Murchison Widefield Array can make observations that help us understand how the Universe evolved.

It took hundreds of years to build the idea of the Big Bang, and it may take a long time to improve it or find an idea that is better. Scientists have a lot of ideas about how the Big Bang started. But these ideas must agree with our observations of the Universe.

The future is very exciting for anyone who wants to help figure this out. The advanced technology we have means that we can build machines that smash particles (tiny little bits of stuff even smaller than an atom) together to show what happened right after the Big Bang. We can now build powerful new telescopes to observe the stars and galaxies in the Universe in a lot of detail. We will use these machines and telescopes to see which ideas about the Big Bang are right and which are wrong.

Sometimes new ideas take many years to be worked out. Sometimes new ideas pop into people's heads very quickly. It is very exciting to have a new idea about the Universe. We will need lots of people who are good at puzzles to help us.

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Hello, curious kids! Have you got a question you'd like an expert to answer? Ask an adult to send your question to us. They can:

* Email your question to curiouskids@theconversation.edu.au
* Tell us on Twitter by tagging @ConversationEDU with the hashtag #curiouskids, or
* Tell us on Facebook

Please tell us your name, age, and which city you live in. You can send an audio recording of your question too, if you want. Send as many questions as you like! We won't be able to answer every question but we will do our best.

Steven Tingay, Professor of Radio Astronomy, Curtin University

This article was originally published on The Conversation. Read the original article. Follow all of the Expert Voices issues and debates — and become part of the discussion — on Facebook, Twitter and Google +. The views expressed are those of the author and do not necessarily reflect the views of the publisher. This version of the article was originally published on Space.com.

MARS - Hubble Sees Tiny Phobos Orbiting Mars

Hubble Sees Tiny Phobos Orbiting Mars:

Mars’ moon Phobos is a pretty fascinating customer! Compared to Mars other moon Deimos, Phobos (named after the Greek personification of fear) is the larger and innermost satellite of the Red Planet. Due to its rapid orbital speed, the irregularly-shaped moon orbits Mars once every 7 hours, 39 minutes, and 12 seconds. In other words, it completes over three orbits of Mar within a single Earth day.

It’s not too surprising then that during a recent observation of Mars with the Hubble space telescope,  Phobos chose to photobomb the picture! It all took place in May of 2016, when while Mars was near opposition and Hubble was trained on the Red Planet to take advantage of it making its closest pass to Earth in over a decade. The well-timed sighting also led to the creation of a time-lapse video that shows the moon’s orbital path.

During an opposition, Mars and Earth are at the closest points in their respective orbits to each other. Because Mars and the Sun appear to be on directly opposite sides of Earth, the term “opposition” is used. These occur every 26 months, and once every 15 to 17 years, an opposition will coincide with Mars being at the closest point in its orbit to the Sun (perihelion).

Phobos from NASA’s Mars Reconnaissance Orbiter on March 23, 2008. Credit: NASA

When this happens, Mars is especially close to Earth, which makes it an ideal occasion to photograph it. The last time this occurred was on May 22nd, 2016, when Mars was and Earth were at a distance of about 76,309,874 km (47,416,757 mi or 0.5101 AU) from each other. This would place it closer to Earth than it had been in 11 years, and the Hubble space telescope was trained on Mars to take advantage of this.

A few days before Mars made its closest pass, Hubble took 13 separate exposures of the planet over the course of 22 minutes, allowing astronomers to create a time-lapse video. This worked out well, since Phobos came into view during the exposures, which led the video showing the path of the moon’s orbit. Because of its small size, Phobos looked like a star that was popping out from behind the planet.

This sighting has only served to enhance Phobos’ fascinating nature. As of 2017, astronomers have been aware of the moon’s existence for 140 years. It was discovered in 1877, when Asaph Hall – while searching for Martian moons – observed it from the U.S. Naval Observatory in Washington D.C. A few days later, he also discovered Deimos, the smaller, outer moon of Mars.

In July of 1969, just two weeks before the Apollo landing, the Mariner 7 probe conducted a flyby of Mars and took the first close-up images of the Moon. In 1977, a year after the Viking 1 lander was deployed to the Martian surface, NASA’s Viking 1 orbiter took the first detailed photographs of the moon. These revealed a cratered surface marred by long, shallow grooves and one massive crater – known as the Stickney crater.

The streaked and stained surface of Phobos, with a close-up on the Stickney crater. Credit: NASA

Asaph Hall named this crater after Chloe Angeline Stickney Hall (his wife) after discovering it in 1878, a year after he discovered Phobos and Deimos. Measuring some 10 km in diameter – almost half of the average diameter of Phobos itself – the impact that created Stickney is believed to have been so powerful that it nearly shattered the moon.

The most widely-accepted theory about Phobos origins is that both it and Deimos were once asteroids that were kicked out of the Main Belt by Jupiter’s gravity, and were then acquired by Mars. But unlike Deimos, Phobos’ orbit is unstable. Every century, the moon draws closer to Mars by about 1.98 meters (6.5 feet). At this rate, scientist estimate that within 30 to 50 million years, it will crash into Mars or be torn to pieces to form a ring in orbit.

This viewing is perhaps a reminder that this satellite won’t be with Mars forever. Then again, it will certainly still be there if and when astronauts (and maybe even colonists) begin setting foot on the planet. To these people, looking up at the sky from the surface of Mars, Phobos will be seen regularly eclipsing the Sun. Because of its small size, it does not fully eclipse the Sun, but it does make transits multiple times in a single day.

So there’s still plenty of time to study and enjoy this fearfully-named moon. And while you’re at it, be sure to check out the video below, courtesy of NASA’s Goddard Space Center!

Further Reading: HubbleSite, NASA



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Cassini Finds that Titan is Building the Chemicals that Might Have Led to Life on Earth

Cassini Finds that Titan is Building the Chemicals that Might Have Led to Life on Earth:

Titan, Saturn’s largest moon, has been a source of mystery ever since scientists began studying it over a century ago. These mysteries have only deepened with the arrival of the Cassini-Huygens mission in the system back in 2004. In addition to finding evidence of a methane cycle, prebiotic conditions and organic chemistry, the Cassini-Huygens mission has also discovered that Titan may have the ingredient that help give rise to life.

Such is the argument made in a recent study by an international team of scientists. After examining data obtained by the Cassini space probe, they identified a negatively charged species of molecule in Titan’s atmosphere. Known as “carbon chain anions”, these molecules are thought to be building blocks for more complex molecules, which could played a key role in the emergence of life of Earth.

The study, titled “Carbon Chain Anions and the Growth of Complex Organic Molecules in Titan’s Ionosphere“, recently appeared in The Astrophysical Journal Letters. The team included researchers from University College in London, the University of Grenoble, Uppsalla University, UCL/Birkbeck, the University of Colorado, the Swedish Institute of Space Physics, the Southwest Research Institute (SwRI), and NASA’s Goddard Space Flight Center.

Diagram of the internal structure of Titan according to the fully differentiated dense-ocean model. Credit: Wikipedia Commons/Kelvinsong

As they indicate in their study, these molecules were detected by the Cassini Plasma Spectrometer (CAPS) as the probe flew through Titan’s upper atmosphere at an distance of 950 – 1300 km (590  – 808 mi) from the surface. They also show how the presence of these molecules was rather unexpected, and represent a considerable challenge to current theories about how Titan’s atmosphere works.

For some time, scientists have understood that within Titan’s ionosphere, nitrogen, carbon and hydrogen are subjected to sunlight and energetic particles from Saturn’s magnetosphere. This exposure drives a process where these elements are transformed into more complex prebiotic compounds, which then drift down towards the lower atmosphere and form a thick haze of organic aerosols that are thought to eventually reach the surface.

This has been the subject of much interest, since the process through which simple molecules form complex organic ones has remained something of a mystery to scientists. This could be coming to an end thanks to the detection of carbon chain anions, though their discovery was altogether unexpected. Since these molecules are highly reactive, they are not expected to last long in Titan’s atmosphere before combining with other materials.

However, the data showed that the carbon chains became depleted closer to the moon, while precursors to larger aerosol molecules underwent rapid growth. This suggests that there is a close relationship between the two, with the chains ‘seeding’ the larger molecules. Already, scientists have held that these molecules were an important part of the process that allowed for life to form on Earth, billions of years ago.

A halo of light surrounds Saturn’s moon Titan in this backlit picture, showing its atmosphere. Credit: NASA/JPL/Space Science Institute

However, their discovery on Titan could be an indication of how life begins to emerge throughout the Universe. As Dr. Ravi Desai, University College London and the lead author of the study, explained in an ESA press release:

“We have made the first unambiguous identification of carbon chain anions in a planet-like atmosphere, which we believe are a vital stepping-stone in the production line of growing bigger, and more complex organic molecules, such as the moon’s large haze particles. This is a known process in the interstellar medium, but now we’ve seen it in a completely different environment, meaning it could represent a universal process for producing complex organic molecules.”

Because of its dense nitrogen and methane atmosphere and the presence of some of the most complex chemistry in the Solar System, Titan is thought by many to be similar to Earth’s early atmosphere. Billions of years ago, before the emergence of microorganisms that allowed for subsequent build-up of oxygen, it is likely that Earth had a thick atmosphere composed of nitrogen, carbon dioxide and inert gases.

Therefore, Titan is often viewed as a sort planetary laboratory, where the chemical reactions that may have led to life on Earth could be studied. However, the prospect of finding a universal pathway towards the ingredients for life has implications that go far beyond Earth. In fact, astronomers could start looking for these same molecules on exoplanets, in an attempt to determine which could give rise to life.

This illustration shows Cassini above Saturn’s northern hemisphere prior to one of its 22 Grand Finale dives. Credit: NASA/JPL-Caltech

Closer to home, the findings could also be significant in the search for life in our own Solar System. “The question is, could it also be happening within other nitrogen-methane atmospheres like at Pluto or Triton, or at exoplanets with similar properties?” asked Desia. And Nicolas Altobelli, the Project Scientist for the Cassini-Huygens mission, added:

“These inspiring results from Cassini show the importance of tracing the journey from small to large chemical species in order to understand how complex organic molecules are produced in an early Earth-like atmosphere. While we haven’t detected life itself, finding complex organics not just at Titan, but also in comets and throughout the interstellar medium, we are certainly coming close to finding its precursors.“

Cassini’s “Grande Finale“, the culmination of its 13-year mission around Saturn and its system of moons, is set to end on September 15th, 2017. In fact, as of the penning of this article, the mission will end in about 1 month, 18 days, 16 hours, and 10 minutes. After making its final pass between Saturn’s rings, the probe will be de-orbited into Saturn’s atmosphere to prevent contamination of the system’s moons.

However, future missions like the James Webb Space Telescope, the ESA’s PLATO mission and ground-based telescopes like ALMA are expected to make some significant exoplanet finds in the coming years. Knowing specifically what kinds of molecules are intrinsic in converting common elements into organic molecules will certainly help narrow down the search for habitable (or even inhabited) planets!



Further Reading: ESA, The Astrophysical Journal Letters

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MILKY WAY ? What Is the Name Of Our Galaxy?

What Is the Name Of Our Galaxy?:

Since prehistoric times, human beings have looked up at at the night sky and pondered the mystery of the band of light that stretches across the heavens. And while theories have been advanced since the days of Ancient Greece as to what it could be, it was only with the birth of modern astronomy that scholars have come come to know precisely what it is – i.e. countless stars at considerable distances from Earth.

The term “Milky Way”, a term which emerged in Classical Antiquity to describe the band of light in the night sky, has since gone on to become the name for our galaxy. Like many others in the known Universe, the Milky Way is a barred, spiral galaxy that is part of the Local Group – a collection of 54 galaxies. Measuring 100,000 – 180,000 light-years in diameter, the Milky Way consists of between 100 and 400 billion stars.

Structure:

The Milky Way consists of a Galactic Center that is shaped like a bar and a Galactic Disk made up of spiral arms, all of which is surrounded by the Halo – which is made up of old stars and globular clusters. The Center, also known as “the bulge”,  is a dense concentration of mostly old stars that measures about 10,000 light years in radius. This region is also the rotational center of the Milky Way.

Illustration of the supermassive black hole at the center of the Milky Way. Credit: NRAO/AUI/NSF

The Galactic Center is also home to an intense radio source named Sagittarius A*, which is believed to have a supermassive black hole (SMBH) at its center. The presence of this black hole has been discerned due to the apparent gravitational influence it has on surrounding stars. Astronomers estimate that it has a mass of between 4.1. and 4.5 million Solar masses.

Outside the barred bulge at the Galactic Center is the Galactic Disk of the Milky Way. This consists of stars, gas and dust which is organized into four spiral arms. These arms typically contain a higher density of interstellar gas and dust than the Galactic average, as well as a greater concentration of star formation. While there is no consensus on the exact structure or extent of these spiral arms, they are commonly grouped into two or four different arms.

In the case of four arms, this is based on the traced paths of gas and younger stars in our galaxy, which corresponds to the Perseus Arm, the Norma and Outer Arm, the Scutum-Centaurum Arm, and the Carina-Sagittarius Arm. There are also at least two smaller arms, which include the Cygnus Arm and the Orion Arm. Meanwhile, surveys based on the presence of older stars show only two major spirals arms – the Perseus arm and the Scutum–Centaurus arm.

Beyond the Galactic Disk is the Halo, which is made up of old stars and globular clusters – 90% of which lie within 100,000 light-years (30,000 parsecs) from the Galactic Center. Recent evidence provided by X-ray observatories indicates that in addition to this stellar halo, the Milky way also has a halo of hot gas that extends for hundreds of thousands of light years.

Artist’s conception of the spiral structure of the Milky Way with two major stellar arms and a bar. Credit: NASA/JPL-Caltech/ESO/R. Hurt

Size and Mass:

The Galactic Disk of the Milky Way Galaxy is approximately 100,000 light years in diameter and about 1,000 light years thick. It is estimated to contain between 100 and 400 billion stars, though the exact figure depends on the number of very low-mass M-type (aka. red dwarf) stars. This is difficult to determine because these stars also have low-luminosity compared to other class.

The distance from the Sun to the Galactic Center is estimated to be between 25,000 to 28,000 light years (7,600 to 8,700 parsecs). The Galactic Center’s bar (aka. its “bulge”)  is thought to be about 27,000 light-years in length and is composed primarily of red stars, all of which are thought to be ancient. The bar is surrounded by the ‘5-kpc ring’, a region that contains much of the galaxy’s molecular hydrogen and where star-formation is most intense.

The Galactic Disk has a diameter of between 70,000 and 100,000 light-years. It does not have a sharp edge, a radius beyond which there are no stars. However, the number of stars drops slowly with distance from the center. Beyond a radius of roughly 40,000 light years, the number of stars drops much faster the farther you get from the center.

https://upload.wikimedia.org/wikipedia/commons/transcoded/e/ee/Simulation_of_the_X-shaped_bulge_of_the_Milky_Way.ogv/Simulation_of_the_X-shaped_bulge_of_the_Milky_Way.ogv.480p.webm

Location of the Solar System:

The Solar System is located near the inner rim of the Orion Arm, a minor spiral arm located between the Carina–Sagittarius Arm and the Perseus Arm. This arm measures some 3,500 light-years (1,100 parsecs) across,  approximately 10,000 light-years (3,100 parsecs) in length, and is at a distance of about 25,400 to 27,400 light years (7.78 to 8.4 thousand parsecs) from the Galactic Center.

History of Observation:

Our galaxy was named because of the way the haze it casts in the night sky resembled spilled milk. This name is also quite ancient. It is translation from the Latin “Via Lactea“, which in turn was translated from the Greek for Galaxias, referring to the pale band of light formed by stars in the galactic plane as seen from Earth.

Persian astronomer Nasir al-Din al-Tusi (1201–1274) even spelled it out in his book Tadhkira: “The Milky Way, i.e. the Galaxy, is made up of a very large number of small, tightly clustered stars, which, on account of their concentration and smallness, seem to be cloudy patches. Because of this, it was likened to milk in color.”

Astronomers had long suspected the Milky Way was made up of stars, but it wasn’t proven until 1610, when Galileo Galilei turned his rudimentary telescope towards the heavens and resolved individual stars in the band across the sky. With the help of telescopes, astronomers realized that there were many, many more stars in the sky, and that all of the ones that we can see are a part of the Milky Way.



In 1755, Immanuel Kant proposed that the Milky Way was a large collection of stars held together by mutual gravity. Just like the Solar System, this collection would be rotating and flattened out as a disk, with the Solar System embedded within it. Astronomer William Herschel (discoverer of Uranus) tried to map its shape in 1785, but he didn’t realize that large portions of the galaxy are obscured by gas and dust, which hide its true shape.

It wasn’t until the 1920s, when Edwin Hubble provided conclusive evidence that the spiral nebulae in the sky were actually whole other galaxies, that the true shape of our galaxy was known. Thenceforth, astronomers came to understand that the Milky Way is a barred, spiral galaxy, and also came to appreciate how big the Universe truly is.

The Milky Way is appropriately named, being the vast and cloudy mass of stars, dust and gas it is. Like all galaxies, ours is believed to have formed from many smaller galaxies colliding and combining in the past. And in 3 to 4 billion years, it will collide with the Andromeda Galaxy to form an even larger mass of stars, gas and dust. Assuming humanity still exists by then (and survives the process) it should make for some interesting viewing!

We have written many interesting articles about the Milky Way here at Universe Today. Here’s 10 Interesting Facts About the Milky Way, How Big is the Milky Way?, Why is our Galaxy Called the Milky Way?, What is the Closest Galaxy to the Milky Way?, Where is the Earth in the Milky Way?, The Milky Way has Only Two Spiral Arms, and It’s Inevitable: Milky Way, Andromeda Galaxy Heading for Collision.

If you’d like more info on galaxies, check out Hubblesite’s News Releases on Galaxies, and here’s NASA’s Science Page on Galaxies.

We’ve also recorded an episode of Astronomy Cast about the Milky Way. Listen here, Episode 99: The Milky Way.

Sources:

• NASA – Milky Way Galaxy
• NASA – Charting the Milky Way from the Inside Out
• Wikipedia – Milky Way
• SEDS – The Milky Way Galaxy

The post What Is the Name Of Our Galaxy? appeared first on Universe Today.