Saturday, January 24, 2015

What Is The Difference Between the Geocentric and Heliocentric Models of the Solar System?

What Is The Difference Between the Geocentric and Heliocentric Models of the Solar System?:

The Solar System. Image Credit: NASA


The Solar System. Image Credit: NASA
What does our Solar System really look like? If we were to somehow fly ourselves above the plane where the Sun and the planets are, what would we see in the center of the Solar System? The answer took a while for astronomers to figure out, leading to a debate between what is known as the geocentric (Earth-centered) model and the heliocentric (Sun-centered model).

The ancients understood that there were certain bright points that would appear to move among the background stars. While who exactly discovered the “naked-eye” planets (the planets you can see without a telescope) is lost in antiquity, we do know that cultures all over the world spotted them.

The ancient Greeks, for example, considered the planets to include Mercury, Venus, Mars, Jupiter and Saturn — as well as the Moon and the Sun. The Earth was in the center of it all (geocentric), with these planets revolving around it. So important did this become in culture that the days of the week were named after the gods, represented by these seven moving points of light.

All the same, not every Greek believed that the Earth was in the middle. Aristarchus of Samos, according to NASA, was the first known person to say that the Sun was in the center of the universe. He proposed this in the third century BCE. The idea never really caught on, and lay dormant (as far as we can tell) for several centuries.

Earth is at the center of this model of the universe created by Bartolomeu Velho, a Portuguese cartographer, in 1568. Credit: NASA/Bibliothèque Nationale, Paris


Earth is at the center of this model of the universe created by Bartolomeu Velho, a Portuguese cartographer, in 1568. Credit: NASA/Bibliothèque Nationale, Paris
Because European scholars relied on Greek sources for their education, for centuries most people followed the teachings of Aristotle and Ptolemy, according to the Galileo Project at Rice University. But there were some things that didn’t make sense. For example, Mars occasionally appeared to move backward with respect to the stars before moving forward again. Ptolemy and others explained this using a system called epicycles, which had the planets moving in little circles within their greater orbits.

But by the fifteen and sixteenth centuries, astronomers in Europe were facing other problems, the project added. Eclipse tables were becoming inaccurate, sailors needed to keep track of their position when sailing out of sight of land (which led to a new method to measure longitude, based partly on accurate timepieces), and the calendar dating from the time of Julius Caesar (44 BCE) no longer was accurate in describing the equinox — a problem for officials concerned with the timing of religious holidays, primarily Easter. (The timing problem was later solved by resetting the calendar and instituting more scientifically rigorous leap years.)

While two 15th-century astronomers (Georg Peurbach and Johannes Regiomontanus) had already consulted the Greek texts for scientific errors, the project continued, it was Nicolaus Copernicus who took that understanding and applied it to astronomy. His observations would revolutionize our thinking of the world.

Retrograde motion of Mars. Image credit: NASA


Retrograde motion of Mars. Image credit: NASA
Published in 1543, Copernicus’ De Revolutionibus Orbium Coelestium (On the Revolutions of the Heavenly Bodies) outlined the heliocentric universe similar to what we know today. Among his ideas, according to Encyclopedia Britannica, was that the planets’ orbits should be plotted with respect to the “fixed point” Sun, that the Earth itself is a planet that turns on an axis, and that when the axis changes directions with respect to the stars, this causes the North Pole star to change over time (which is now known as the precession of the equinoxes.)

Putting the Sun at the center of our Solar System, other astronomers began to realize, simplified the orbits for the planets. And it helped explain what was so weird about Mars. The reason it backs up in the sky is the Earth has a smaller orbit than Mars. When Earth passes by Mars in its orbit, the planet appears to go backwards. Then when Earth finishes the pass, Mars appears to move forwards again.

Other supports for heliocentrism began to emerge as well. Johannes Kepler’s rules of motions of the planets (based on work from him and Tycho Brahe) are based on the heliocentric model. And in Isaac Newton’s Principia, the scientist described how the motions happen: a force called gravity, which appears to be “inversely proportional to the square of the distance between objects”, according to the University of Wisconsin-Madison.

Artist's conception of the Kepler Space Telescope. Credit: NASA/JPL-Caltech


Artist’s conception of the Kepler Space Telescope. Credit: NASA/JPL-Caltech
Newton’s gravity theory was later supplanted by that of Albert Einstein, who in the early 20th century proposed that gravity is instead a warping of space-time by massive objects. That said, heliocentric calculations guide spacecraft in their orbits today and the model is the best way to describe how the Sun, planets and other objects move.

Universe Today has articles on both the heliocentric model and the geocentric model, and Astronomy Cast has an episode on the center of the universe.



About 

Elizabeth Howell is the senior writer at Universe Today. She also works for Space.com, Space Exploration Network, the NASA Lunar Science Institute, NASA Astrobiology Magazine and LiveScience, among others. Career highlights include watching three shuttle launches, and going on a two-week simulated Mars expedition in rural Utah. You can follow her on Twitter @howellspace or contact her at her website.

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See a Rare Comet-Moon Conjunction Tonight

See a Rare Comet-Moon Conjunction Tonight:



Tonight (Friday, Jan. 23rd) the moon will pass only about 1° (two moon diameters) south of Comet 15P/Finlay as seen from the Americas. This map shows the view from the upper Midwest at 7 p.m. Two 6th magnitude stars in Pisces are labelled. Created with Chris Marriott's SkyMap software


Tonight (Friday, Jan. 23rd) the moon will pass only about 1° (two moon diameters) south of Comet 15P/Finlay as seen from the Americas. This map shows the view from the upper Midwest at 7 p.m. Two 6th magnitude stars in Pisces are labelled. Created with Chris Marriott’s SkyMap software
I want to alert you to a rather unusual event occurring this evening.

Many of you already know about the triple shadow transit of Jupiter’s moons Io, Europa and Callisto. That’s scheduled for late tonight.

Earlier, around nightfall, the crescent moon will lie 1° or less to the south-southwest of comet 15P/Finlay. No doubt lunar glare will hamper the view some, but what a fun opportunity to use the moon to find a comet.(...)
Read the rest of See a Rare Comet-Moon Conjunction Tonight (303 words)

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VIDEO ANIMATION Using Instruments (Wide View) EARTH

Using Instruments (Wide View):






This animation shows NASA's Orbiting Carbon Observatory-2 using its instruments to study Earth and map the global distribution of carbon dioxide.





Original enclosures:
OCO-2_6_Data_Globe-1280.m4v
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Thursday, January 22, 2015

Chandra Celebrates The International Year of Light

Chandra Celebrates The International Year of Light:

IYL*

The year of 2015 has been declared the International Year of Light (IYL) by the United Nations. Organizations, institutions, and individuals involved in the science and applications of light will be joining together for this yearlong celebration to help spread the word about the wonders of light.

In many ways, astronomy uses the science of light. By building telescopes that can detect light in its many forms, from radio waves on one end of the "electromagnetic spectrum" to gamma rays on the other, scientists can get a better understanding of the processes at work in the Universe.

NASA's Chandra X-ray Observatory explores the Universe in X-rays, a high-energy form of light. By studying X-ray data and comparing them with observations in other types of light, scientists can develop a better understanding of objects likes stars and galaxies that generate temperatures of millions of degrees and produce X-rays.

To recognize the start of IYL, the Chandra X-ray Center is releasing a set of images that combine data from telescopes tuned to different wavelengths of light. From a distant galaxy to the relatively nearby debris field of an exploded star, these images demonstrate the myriad ways that information about the Universe is communicated to us through light.

More information at http://chandra.harvard.edu/photo/2015/iyl/index.html

-Megan Watzke, CXC
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Why Is Our Galaxy Called The Milky Way?

Why Is Our Galaxy Called The Milky Way?:

This annotated artist's conception illustrates our current understanding of the structure of the Milky Way galaxy. Image Credit: NASA

This annotated artist’s conception illustrates our current understanding of the structure of the Milky Way galaxy. Image Credit: NASA
We have a lot of crazy informal names for space sights. Sometimes they’re named after how they are shaped, like the Horsehead Nebula. Sometimes they have a name “borrowed” from their constellation, such as the Andromeda Galaxy. But what about our own galaxy, the Milky Way? Why does this band of stars across Earth’s sky have a name associated with food?

First, let’s back up a bit and talk a bit about what the Milky Way actually is. Astronomers believe it is a barred spiral galaxy — a galaxy with a spiral shape that has a line of stars across its middle, as you can see in the picture above. If you were to fly across the galaxy at the speed of light, it would take you an astounding 100,000 years.

The Milky Way is part of a collection of galaxies called the Local Group. We’re on a collision course with the most massive and largest member of that collection, which is the Andromeda Galaxy (also known as M31). The Milky Way is the second-largest galaxy, and the Triangulum Galaxy (M33) the third-largest. There are roughly 30 members of this group all told.

To get a sense of its immense size, you’ll be glad to hear the Earth is nowhere near the Milky Way’s center and its powerful, supermassive black hole. NASA says we’re roughly 165 quadrillion miles from the black hole, which is found in the direction of the constellation Sagittarius.

The magnetic field of our Milky Way Galaxy as seen by ESA’s Planck satellite. Credit: ESA and the Planck Collaboration.


The magnetic field of our Milky Way Galaxy as seen by ESA’s Planck satellite. Credit: ESA and the Planck Collaboration.
As for how our galaxy got its name, it is indeed because of its milky appearance as it stretches across the sky. While spotting the galaxy’s arms is a challenge from our current light-polluted centers, if you get out to a more rural area it really begins to dominate the skies. The ancient Romans called our galaxy the Via Lactea, which literally means “The Road of Milk.”

And according to the Astronomy Picture of the Day website, the Greek word for “galaxy” also derives from the word “milk”. It’s hard to say if it was a coincidence, because the origin of both the Milky Way’s name and the Greek word for galaxy are long lost to prehistory, although some sources say that it was inspired by the Milky Way’s appearance.

It took thousands of years for us to understand the nature of what we were looking at. Back in the time of Aristotle, according to the Library of Congress, the Milky Way was believed to be the spot “where the celestial spheres came into contact with the terrestrial spheres.” Without a telescope, it was hard to say much more, but that began to change in the early 1600s.

Beautiful view of our Milky Way Galaxy. If other alien civilizations are out there, can we find them? Credit: ESO/S. Guisard


Beautiful view of our Milky Way Galaxy. If other alien civilizations are out there, can we find them? Credit: ESO/S. Guisard
One important early observation, the library adds, was from the noted astronomer Galileo Galilei. (He’s best known for being credited for the discovery of four of Jupiter’s moons — Io, Europa, Callisto and Ganymede — which he spotted through a telescope.) In his 1610 volume Sidereus Nuncius, Galileo said his observations showed the Milky Way was not a uniform band, but had certain pockets with more star densities.

But the true nature of the galaxy eluded us for some time yet. Other early observations: the stars were a part of our Solar System (Thomas Wainwright, 1750 — a claim that was later shown as erroneous) and that the stars appeared to be denser on one side of the band than the other (William and John Herschel, in the late 1700s).

It took until the 20th century for astronomers to figure out that the Milky Way is just one of a large number of galaxies in the sky. This came, the library says, through a few steps: doing observations of distant “spiral nebulas” that showed their speeds were receding faster than the escape velocity of our own galaxy (Vesto Slipher, 1912); observations that a “nova” (temporary bright star) in Andromeda was fainter than our own galaxy (Herber Curtis, 1917); and most famously, Edwin Hubble’s observations of galaxies showing that they were very far from Earth indeed (1920ish).

The Hubble Ultra Deep Field seen in ultraviolet, visible, and infrared light. Image Credit: NASA, ESA, H. Teplitz and M. Rafelski (IPAC/Caltech), A. Koekemoer (STScI), R. Windhorst (Arizona State University), and Z. Levay (STScI)


The Hubble Ultra Deep Field seen in ultraviolet, visible, and infrared light. Image Credit: NASA, ESA, H. Teplitz and M. Rafelski (IPAC/Caltech), A. Koekemoer (STScI), R. Windhorst (Arizona State University), and Z. Levay (STScI)
There are in fact more galaxies out there than we could have imagined even a century ago. Using the Hubble Space Telescope, periodically astronomers have used the powerful observatory to gaze at a tiny patch of the sky.

This has produced several “deep fields” of galaxies billions of light-years away. It’s hard to estimate just how many there are “out there”, but estimates seem to say there are at least 100 billion galaxies. That’ll keep astronomers busy observing for a while.

We have written many articles about the Milky Way for Universe Today. Here are some facts about the Milky Way, and here’s an article about the stars in the Milky Way. We’ve also recorded an episode of Astronomy Cast about galaxies. Listen here, Episode 97: Galaxies.



About 

Elizabeth Howell is the senior writer at Universe Today. She also works for Space.com, Space Exploration Network, the NASA Lunar Science Institute, NASA Astrobiology Magazine and LiveScience, among others. Career highlights include watching three shuttle launches, and going on a two-week simulated Mars expedition in rural Utah. You can follow her on Twitter @howellspace or contact her at her website.

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10 Amazing Facts About Black Holes

10 Amazing Facts About Black Holes:

An artists illustration of the central engine of a Quasar. These "Quasi-stellar Objects" QSOs are now recognized as the super massive black holes at the center of emerging galaxies in the early Universe. (Photo Credit: NASA)


An artists illustration of the central engine of a Quasar. These “Quasi-stellar Objects” QSOs are now recognized as the super massive black holes at the center of emerging galaxies in the early Universe. (Photo Credit: NASA)
Imagine matter packed so densely that nothing can escape. Not a moon, not a planet and not even light. That’s what black holes are — a spot where gravity’s pull is huge, ending up being dangerous for anything that accidentally strays by.

But how did black holes come to be, and why are they important? Below we have 10 facts about black holes — just a few tidbits about these fascinating objects.

Fact 1: You can’t directly see a black hole.

Because a black hole is indeed “black” — no light can escape from it — it’s impossible for us to sense the hole directly through our instruments, no matter what kind of electromagnetic radiation you use (light, X-rays, whatever.) The key is to look at the hole’s effects on the nearby environment, points out NASA. Say a star happens to get too close to the black hole, for example. The black hole naturally pulls on the star and rips it to shreds. When the matter from the star begins to bleed toward the black hole, it gets faster, gets hotter and glows brightly in X-rays.

Fact 2: Look out! Our Milky Way likely has a black hole.

A natural next question is given how dangerous a black hole is, is Earth in any imminent danger of getting swallowed? The answer is no, astronomers say, although there is probably a huge supermassive black hole lurking in the middle of our galaxy. Luckily, we’re nowhere near this monster — we are about two-thirds of the way out from the center, relative to the rest of our galaxy — but we can certainly observe its effects from afar. For example: the European Space Agency says it’s four million times more massive than our Sun, and that it’s surrounded by surprisingly hot gas.

Sagittarius A in infrared (red and yellow, from the Hubble Space Telescope) and X-ray (blue, from the Chandra space telescope). Credit: X-ray: NASA/UMass/D.Wang et al., IR: NASA/STScI


Sagittarius A in infrared (red and yellow, from the Hubble Space Telescope) and X-ray (blue, from the Chandra space telescope). Credit: X-ray: NASA/UMass/D.Wang et al., IR: NASA/STScI
Fact 3: Dying stars create stellar black holes.

Say you have a star that’s about 20 times more massive than the Sun. Our Sun is going to end its life quietly; when its nuclear fuel burns out, it’ll slowly fade into a white dwarf. That’s not the case for far more massive stars. When those monsters run out of fuel, gravity will overwhelm the natural pressure the star maintains to keep its shape stable. When the pressure from nuclear reactions collapses, according to the Space Telescope Science Institute, gravity violently overwhelms and collapses the core and other layers are flung into space. This is called a supernova. The remaining core collapses into a singularity — a spot of infinite density and almost no volume. That’s another name for a black hole.

Fact 4: Black holes come in a range of sizes.

There are at least three types of black holes, NASA says, ranging from relative squeakers to those that dominate a galaxy’s center. Primordial black holes are the smallest kinds, and range in size from one atom’s size to a mountain’s mass. Stellar black holes, the most common type, are up to 20 times more massive than our own Sun and are likely sprinkled in the dozens within the Milky Way. And then there are the gargantuan ones in the centers of galaxies, called “supermassive black holes.” They’re each more than one million times more massive than the Sun. How these beasts formed is still being examined.

A binary black hole system, viewed from above. Image Credit: Bohn et al. (see http://arxiv.org/abs/1410.7775)


A binary black hole system, viewed from above. Image Credit: Bohn et al. (see http://arxiv.org/abs/1410.7775)
Fact 5: Weird time stuff happens around black holes.

This is best illustrated by one person (call them Unlucky) falling into a black hole while another person (call them Lucky) watches. From Lucky’s perspective, Unlucky’s time clock appears to be ticking slower and slower. This is in accordance with Einstein’s theory of general relativity, which (simply put) says that time is affected by how fast you go, when you’re at extreme speeds close to light. The black hole warps time and space so much that Unlucky’s time appears to be running slower. From Unlucky’s perspective, however, their clock is running normally and Lucky’s is running fast.

Fact 6: The first black hole wasn’t discovered until X-ray astronomy was used.

Cygnus X-1 was first found during balloon flights in the 1960s, but wasn’t identified as a black hole for about another decade. According to NASA, the black hole is 10 times more massive to the Sun. Nearby is a blue supergiant star that is about 20 times more massive than the Sun, which is bleeding due to the black hole and creating X-ray emissions.

Illustration of Cygnus X-1, another stellar-mass black hole located 6070 ly away. (NASA/CXC/M.Weiss)


Illustration of Cygnus X-1, another stellar-mass black hole located 6070 ly away. (NASA/CXC/M.Weiss)
Fact 7: The nearest black hole is likely not 1,600 light-years away.

An erroneous measurement of V4641 Sagitarii led to a slew of news reports a few years back saying that the nearest black hole to Earth is astoundingly close, just 1,600 light-years away. Not close enough to be considered dangerous, but way closer than thought. Further research, however, shows that the black hole is likely further away than that. Looking at the rotation of its companion star, among other factors, yielded a 2014 result of more than 20,000 light years.

Fact 8: We aren’t sure if wormholes exist.

A popular science-fiction topic concerns what happens if somebody falls into a black hole. Some people believe these objects are a sort of wormhole to other parts of the Universe, making faster-than-light travel possible. But as this Smithsonian Magazine article points out, anything is possible since we still have a lot to figure out about physics. “Since we do not yet have a theory that reliably unifies general relativity with quantum mechanics, we do not know of the entire zoo of possible spacetime structures that could accommodate wormholes,” said Abi Loeb, who is with the Harvard-Smithsonian Center for Astrophysics.

Diagram of a wormhole, or theoretical shortcut path between two locations in the universe. Credit: Wikipedia


Diagram of a wormhole, or theoretical shortcut path between two locations in the universe. Credit: Wikipedia
Fact 9: Black holes are only dangerous if you get too close.

Like creatures behind a cage, it’s okay to observe a black hole if you stay away from its event horizon — think of it like the gravitational field of a planet. This zone is the point of no return, when you’re too close for any hope of rescue. But you can safely observe the black hole from outside of this arena. By extension, this means it’s likely impossible for a black hole to swallow up everything in the Universe (barring some sort of major revision to physics or understanding of our Cosmos, of course.)

Fact 10: Black holes are used all the time in science fiction.

There are so many films and movies using black holes, for example, that it’s impossible to list them all. Interstellar‘s journeys through the universe includes a close-up look at a black hole. Event Horizon explores the phenomenon of artificial black holes — something that is also discussed in the Star Trek universe. Black holes are also talked about in Battlestar: Galactica, Stargate: SG1 and many, many other space shows.

Here on Universe Today we have a great article about a practical use for black holes: as spacecraft engines. No one can get to a black hole without space travel. Astronomy Cast offers a good episode about interstellar travel.



About 

Elizabeth Howell is the senior writer at Universe Today. She also works for Space.com, Space Exploration Network, the NASA Lunar Science Institute, NASA Astrobiology Magazine and LiveScience, among others. Career highlights include watching three shuttle launches, and going on a two-week simulated Mars expedition in rural Utah. You can follow her on Twitter @howellspace or contact her at her website.

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The Entire Milky Way Might Be a Huge Wormhole That’s Stable and Navigable

The Entire Milky Way Might Be a Huge Wormhole That’s Stable and Navigable:

Artist rendering of a wormhole connecting two galaxies. Credit: Davide and Paolo Salucci


Artist rendering of a wormhole connecting two galaxies. Credit: Davide and Paolo Salucci.
Our very own Milky Way could be home to a giant tunnel in spacetime.

At least, that’s what the authors of a new study have proposed. According to the team, a collaboration between Indian, Italian, and North American researchers at the International School for Advanced Studies (SISSA) in Italy, the central halo of our galaxy may harbor enough dark matter to support the creation and sustenance of a “stable and navigable” shortcut to a distant region of spacetime – a phenomenon known as a wormhole.

Wormholes were first conceptualized by Albert Einstein and Nathan Rosen in 1935. Far from being fodder for science fiction, the two scientists instead proposed their idea as a way to get around the idea of black hole singularities. Rather than creating a knot of infinite density, Einstein and Rosen thought, the hefty energy inherent in such a massive body would distort spacetime to such an extent that it bent over on itself, allowing a bridge to form between two distant areas of the Universe. Alas, these wormholes would be extremely unstable and would require enormous amounts of “negative energy” to remain open.

Wormhole diagram. Image credit: NASA


A graphic of the structure of a theorized wormhole (NASA)
But according to the team at SISSA, large amounts of dark matter could provide this fuel. Using a model of dark matter’s abundance that is based on the rotation curves of other spiral galaxies, the researchers found that the distribution of dark matter in the Milky Way produced solutions in general relativity that would, theoretically, allow a stable wormhole to arise.

Paulo Salucci, an astrophysicist on the the team from SISSA, explained: “If we combine the map of the dark matter in the Milky Way with the most recent Big Bang model to explain the universe and we hypothesise the existence of space-time tunnels, what we get is that our galaxy could really contain one of these tunnels, and that the tunnel could even be the size of the galaxy itself.” He continued, “But there’s more. We could even travel through this tunnel, since, based on our calculations, it could be navigable. Just like the one we’ve all seen in the recent film Interstellar.”

Of course, Salucci and the other researchers were working on this project long before Interstellar was released, but their result does lend some theoretical support to the ideas in the film – ideas that were also fact-tested and revised by physics guru Kip Thorne of Caltech.

The authors believe that their result reinforces the importance of discerning the true nature of dark matter. According to Salucci, “Dark matter may be ‘another dimension’, perhaps even a major galactic transport system. In any case, we really need to start asking ourselves what it is”.

It is important to understand that this is purely a mathematical result. Indeed, such a wormhole may be theroretically possible… but that doesn’t mean it’s probable. Salucci ventured, “Obviously we’re not claiming that our galaxy is definitely a wormhole, but simply that, according to theoretical models, this hypothesis is a possibility.”

The researchers went on to explain that their idea could be tested experimentally by comparing our own Milky Way, a spiral galaxy, with a nearby galaxy of a different type. By comparing the dark matter distributions between the two galaxies, scientists would potentially be able to use general relativity to probe differences in their spacetime dynamics.

Realistically, the technology that would allow researchers to do that is a long way off. But never fear, science (and scifi) fans – you can still check out the team’s wormhole simulation in the animation below, watch the movie if you haven’t already, and/or get your hands on a copy of Kip Thorne’s book, The Science of Interstellar.



The team’s research was published in the November 2014 issue of Annals of Physics. A pre-print of the paper is available here.



About 

Vanessa earned her bachelor's degree in Astronomy and Physics in 2009 from Wheaton College in Massachusetts. Her credits in astronomy include observing and analyzing eclipsing binary star systems and taking a walk on the theory side as a NSF REU intern, investigating the expansion of the Universe by analyzing its traces in observations of type 1a supernovae. In her spare time she enjoys writing about astrophysics, cosmology, biology, and medicine, making delicious vegetarian meals, taking adventures with her husband and/or Nikon D50, and saving the world.

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Wednesday, January 21, 2015

Here’s Ceres Compared to All the Other Asteroids We’ve Visited

Here’s Ceres Compared to All the Other Asteroids We’ve Visited:

Ceres compared to asteroids visited to date, including Vesta, Dawn's mapping target in 2011. Image by NASA/ESA/JAXA. Compiled by Paul Schenck.


Ceres compared to asteroids visited to date, including Vesta, Dawn’s mapping target in 2011. Image by NASA/ESA/JAXA. Compiled by Paul Schenck.
When the Dawn mission was in its planning stages, Ceres was considered an asteroid. But in 2006, a year before the mission launched, the International Astronomical Union formed a new class of solar system objects known as dwarf planets, and since by definition a dwarf planet is spherical and travels in an orbit around the Sun, Ceres fit that definition perfectly.

But since it’s located in the Asteroid Belt, we still tend to think of Ceres as an asteroid. So, how does Ceres compare to other asteroids?

Dr. Paul Schenk, who is a participating scientist on the Dawn mission, recently put together some graphics on his website and the one above compares Ceres to other asteroids that we’ve visited with spacecraft.

Of course, Ceres is bigger (it’s the biggest object in the Asteroid Belt) and more spherical than the other asteroids. When it comes right down to it, Ceres doesn’t look much like an asteroid at all!

“Ceres is most similar in size to several of Saturn’s icy moons and may be similar internally as well, being composed of 25% water ice by mass,” Schenk noted on his website.

Comparisons of Ceres with other prominent icy objects. Dione is Ceres' closest twin in size and mass. Image credit: NASA/ESA. Compiled by Paul Schenk.


Comparisons of Ceres with other prominent icy objects. Dione is Ceres’ closest twin in size and mass. Image credit: NASA/ESA. Compiled by Paul Schenk.
And water is one of the most interesting and mysterious aspects of Ceres. A year ago, the Herschel space telescope discovered water vapor around Ceres, and the vapor could be emanating from water plumes — much like those that are on Saturn’s moon Enceladus – or it could be from cryovolcanism from geysers or icy volcano.

“The water vapor question is one of the most interesting things we will look for,” Schenk told Universe Today. “What is its source, what does it indicate about the interior and activity level within Ceres? Is Ceres active, very ancient, or both? Does it go back to the earliest Solar System? Those are the questions we hope to answer with Dawn.”

Some scientists also think Ceres may have an ocean and possibly an atmosphere, which makes Dawn’s arrival at Ceres in March one of the most exciting planetary events of 2015, in addition to New Horizon’s arrival at Pluto.

“Since we don’t know why the water vapor venting has happened, or even if it continues, it’s hard to say much more than that,” Schenk said via email, “but it is theoretically possible that some liquid water still exists within Ceres. Dawn will try to determine if that is true.”

One of the possibilities that has been discussed is that if the water vapor is confirmed, Ceres could potentially host microbial life. I asked Schenk what other factors would have to be present in order for that to have occurred?

“The presence of carbon molecules is often regarded as necessary for life,” he replied, “and we think we see that on the surface spectroscopically in the form of carbonates and clays. So, I think the questions will be, whether there is actually liquid water of any kind, whether the carbon compounds are just a surface coating or in the interior, and whether Ceres has ever been warm. If those are true then some sort of prebiotic or biotic activity is in play.”

Since we do not know the answer to any of these questions yet, Schenk says Dawn’s visit to Ceres should be interesting!

On thing of note is that Dawn is now closing in on Ceres and just today, the team released the best image we have yet of Ceres, which you can see in our article here.

Read more of Schenk’s article, “Year of the ‘Dwarves': Ceres and Pluto Get Their Due.”

Keep tabs on the Dawn mission by following Universe Today, or see the Dawn mission website.

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How Big Is The Milky Way?

How Big Is The Milky Way?:

The summertime Milky Way from Scorpius to Cygnus is broader and brighter than the winter version because we look into the direction of its center. Credit: Stephen Bockhold


The summertime Milky Way from Scorpius to Cygnus is broader and brighter than the winter version because we look into the direction of its center. Credit: Stephen Bockhold
The Milky Way is our home galaxy, the spot where the Earth resides. We are not anywhere near the center — NASA says we’re roughly 165 quadrillion miles from the galaxy’s black hole, for example — which demonstrates just how darn big the galaxy is. So how big is it, and how does it measure up with other neighborhood residents?

The numbers are pretty astounding. NASA estimates the galaxy at 100,000 light-years across. Since one light year is about 9.5 x 1012km, so the diameter of the Milky Way galaxy is about 9.5 x 1017 km in diameter. The thickness of the galaxy ranges depending on how close you are to the center, but it’s tens of thousands of light-years across.

Our galaxy is part of a collection known as the Local Group. Because some of these galaxies are prominent in our sky, the names tend to be familiar. The Milky Way is on a collision course with the most massive member of the group, called M31 or the Andromeda Galaxy. The Milky Way is the second-largest member, with M33 (the Triangulum Galaxy) the third-largest, NASA says. Andromeda appears much brighter in the night sky due to its size and relatively closer distance. There are about 30 members of this group.

The Andromeda Galaxy will collide with the Milky Way in the future. Credit: Adam Evans


The Andromeda Galaxy will collide with the Milky Way in the future. Credit: Adam Evans
Because we are inside the Milky Way’s arms, it appears as a band of stars (or a fuzzy white band) across the Earth’s sky. Casting a pair of binoculars or a telescope across it shows a mix of lighter areas and darker areas; the darker areas are dust that obscures any light from stars, galaxies and other bright objects behind it. From the outside, however, astronomers say the Milky Way is a barred spiral galaxy — a galaxy that has a band of stars across its center as well as the spiral shape.

If you’re looking for the center of the galaxy, gaze at the constellation Sagittarius, which is low on the summer sky horizon for most northern hemisphere residents. The constellation contains a massive radio source known as Sagittarius A*. Astronomers using the Chandra space telescope discovered why this supermassive black hole is relatively weak in X-rays: it’s because hot gas is being pulled inside the nebula, and most of it (99%) gets ejected and diffused.

Sagittarius A in infrared (red and yellow, from the Hubble Space Telescope) and X-ray (blue, from the Chandra space telescope). Credit: X-ray: NASA/UMass/D.Wang et al., IR: NASA/STScI


Sagittarius A in infrared (red and yellow, from the Hubble Space Telescope) and X-ray (blue, from the Chandra space telescope). Credit: X-ray: NASA/UMass/D.Wang et al., IR: NASA/STScI
Based on observing globular clusters (star clusters) in the galaxy, astronomers have estimated the Milky Way’s overall age at 13.5 billion years old — just two million years younger than the rest of the universe.

However, scientists are beginning to think that different parts of the galaxy formed at different times. In 2012, for example, astronomers led by Jason Kalirai of the Space Telescope Science Institute pinned down the age of the Milky Way’s inner halo of stars: 11.5 billion years old. They used white dwarfs, the burned-out remnants of Sun-like stars, to make that measurement.

Kalirai’s group’s research indicates that the Milky Way formed in the following sequence: the halo (including globular star clusters and dwarf galaxies), the inner halo (whose stars were born as a result of this construction) and the outer halo (created when the Milky Way ate up nearby ancient dwarf galaxies).

Artist's impression of the structure of the Milky Way's halo. Credit: NASA, ESA, and A. Feild (STScI)


Artist’s impression of the structure of the Milky Way’s halo. Credit: NASA, ESA, and A. Feild (STScI)
While we’ve been focusing on the parts of the galaxy that you can see, in reality most of its mass is made up of dark matter. NASA estimates that there is about 10 times the mass of dark matter than the visible matter in the universe. (Dark matter is a form of matter that we cannot sense with conventional telescopic instruments, except through its gravitational effect on other things such as galaxies. When masses gather in high enough concentrations, they can bend the light of other objects.)

We have written many articles about the Milky Way for Universe Today. Here’s an article about the rotation of Milky Way, and here are some facts about the Milky Way. We’ve also recorded an episode of Astronomy Cast about galaxies. Listen here, Episode 97: Galaxies.



About 

Elizabeth Howell is the senior writer at Universe Today. She also works for Space.com, Space Exploration Network, the NASA Lunar Science Institute, NASA Astrobiology Magazine and LiveScience, among others. Career highlights include watching three shuttle launches, and going on a two-week simulated Mars expedition in rural Utah. You can follow her on Twitter @howellspace or contact her at her website.

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Rare Triple Transit! There’ll be 3 Moon Shadows on Jupiter on January 24th, 2015

Rare Triple Transit! There’ll be 3 Moon Shadows on Jupiter on January 24th, 2015:

Credit:


The triple shadow transit of October 12th, 2013. Credit & copyright: John Rozakis.
Play the skywatching game long enough, and anything can happen.

Well, nearly anything. One of the more unique clockwork events in our solar system occurs this weekend, when shadows cast by three of Jupiter’s moons can be seen transiting its lofty cloud tops… simultaneously.

How rare is such an event? Well, Jean Meeus calculates 31 triple events involving moons or their shadows occurring over the 60 year span from 1981 to 2040.

But not all are as favorably placed as this weekend’s event. First, Jupiter heads towards opposition just next month. And of the aforementioned 31 events, only 9 are triple shadow transits. Miss this weekend’s event, and you’ll have to wait until March 20th, 2032 for the next triple shadow transit to occur.

Hubble spies a triple shadow transit on March 28th, 2004 . Credit: NASA/JPL/Arizona.


Hubble spies a triple shadow transit on March 28th, 2004 . Credit: NASA/JPL/Arizona.
Of course, double shadow transits are much more common throughout the year, and we included some of the best for North America and Europe in 2015 in our 2015 roundup.

The key times when all three shadows can be seen crossing Jupiter’s 45” wide disk are on the morning of Saturday, January 24th starting at 6:26 Universal Time (UT) as Europa’s shadow ingresses into view, until 6:54 UT when Io’s shadow egresses out of sight. This converts to 1:26 AM EST to 1:54 AM EST. The span of ‘triplicate shadows’ only covers a period of slightly less than 30 minutes, but the action always unfolds fast in the Jovian system with the planet’s 10 hour rotation period.

The view at 6:41 UT/1:41 AM EST. Credit: Created using Starry Night Education software.


The view on January 24th at 6:41 UT/1:41 AM EST. Credit: Created using Starry Night Education software.
Unfortunately, the Great Red Spot is predicted to be just out of view when the triple transit occurs, as it crosses Jupiter’s central meridian over three hours later at 10:28 UT.

The moons involved in this weekend’s event are Io, Callisto and Europa. Now, I know what you’re thinking. Seeing three shadows at once is pretty neat, but can you ever see four?

The short answer is no, and the reason has to do with orbital resonance.

The orbital resonance of the three innermost Galilean moons. (Credit: Wikimedia Commons).


The orbital resonance of the three innermost Galilean moons. (Credit: Wikimedia Commons).
The three innermost Galilean moons of Jupiter (Io, Europa and Ganymede) are locked in a 4:2:1 resonance. Unfortunately, this resonance assures that you’ll always see two of the innermost three crossing the disk of Jupiter, but never all three at once. Either Europa or Ganymede is nearly always the “odd moon out.”

To complete a ‘triple play,’ outermost Callisto must enter the picture. Trouble is, Callisto is the only Galilean moon that can ‘miss’ Jupiter’s disk from our line of sight. We’re lucky to be in an ongoing season of Callisto transits in 2015, a period that ends in July 2016.

Perhaps, on some far off day, a space tourism agency will offer tours to that imaginary vantage point on the surface of one of Jupiter’s moons such as Callisto to watch a triple transit occur from close up. Sign me up!



Jupiter currently rises in late January around 5:30 PM local, and sets after sunrise. It is also well placed for northern hemisphere observers in Leo at a declination 16 degrees north . This weekend’s event favors Europe towards local sunrise and ‘Jupiter-set,’ and finds the gas giant world well-placed high in the sky for all of North America in the early morning hours of the 24th.

2AM local Credit: Stellarium.


Jupiter rides high to the south at 1:45 AM EST for the US East Coast. Credit: Stellarium.
Look closely. Do the shadows of the individual moons appear different to you at the eyepiece? It’s interesting to note during a multiple transit that not all Jovian moon shadows are ‘created equal’. Distant Callisto casts a shadow that’s broad, with a ragged gray and diffuse rim, while the shadow of innermost Io appears as an inky black punch-hole dot. If you didn’t know better, you’d think those alien monoliths were busy consuming Jupiter in a scene straight out of the movie 2010.  Try sketching multiple shadow transits and you’ll soon find that you can actually identify which moon is casting a shadow just from its appearance alone.

The orientation of Earth's nighttime shadow at mid-triple transit. Credit: Created using Orbitron.


The orientation of Earth’s nighttime shadow at mid-triple transit. Credit: Created using Orbitron.
Other mysteries of the Galilean moons persist as well. Why did late 19th century observers describe them as egg-shaped? Can visual observers tease out such elusive phenomena as eruptions on Io by measuring its anomalous brightening? I still think it’s amazing that webcam imagers can now actually pry out surface detail from the Galilean moons!

Photo by author.


The 2004 triple shadow transit. Photo by author.
Observing and imaging a shadow transit is easy using a homemade planetary webcam. We’d love to see someone produce a high quality animation of the upcoming triple shadow transit. I know that such high tech processing abilities — to include field de-rotation and convolution mapping of the Jovian sphere — are indeed out there… its breathtaking to imagine just how quickly the fledgling field of ad hoc planetary webcam imaging has changed in just 10 years.

The moons and Jupiter itself also cast shadows off to one side of the planet or the other depending on our current vantage point. We call the point when Jupiter sits 90 degrees east or west of the Sun quadrature, and the point when it rises and sets opposite to the Sun is known as opposition.  Opposition for Jupiter is coming right up for 2015 on February 6th. During opposition, Jupiter and its moons cast their respective shadows nearly straight back.

Did you know: the speed of light was first deduced by Danish astronomer Ole Rømer in 1671 using the discrepancy he noted while predicting phenomena of the Galilean moons at quadrature versus opposition. There were also early ideas to use the positions of the Galilean moons to tell time at sea, but it turned out to be hard enough to see the moons and their shadows with a small telescope based on land, let alone from the pitching deck of a ship in the middle of the ocean.

And speaking of mutual events, we’re still in the midst of a season where it’s possible to see the moons of Jupiter eclipse and occult one another. Check out the USNO’s table for a complete list of events, coming to a sky near you.

And let’s not forget that NASA’s Juno spacecraft is headed towards Jupiter as well., Juno is set to enter a wide swooping orbit around the largest planet in the solar system in July 2016.

Now is a great time to get out and explore Jove… don’t miss this weekend’s triple shadow transit!

Read Dave Dickinson’s sci-fi tale of astronomical eclipse tourism through time and space titled Exeligmos.



About 

David Dickinson is an Earth science teacher, freelance science writer, retired USAF veteran & backyard astronomer. He currently writes and ponders the universe from Tampa Bay, Florida.

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First Hubble and Now Dawn Have Seen This White Spot on Ceres. What is it?

First Hubble and Now Dawn Have Seen This White Spot on Ceres. What is it?:

Comparison of HST and Dawn FC images of Ceres taken nearly 11 years apart. Credit: NASA.


Comparison of HST and Dawn FC images of Ceres taken nearly 11 years apart. Credit: NASA.
There’s a big white spot on Ceres and we don’t know what it is. We’ve known about the white spot since the Hubble Space Telescope first captured images of it in 2003 and 2004, and in subsequent images taken by Hubble, the spot remains visible. Now, in images released yesterday from the Dawn spacecraft, currently on approach to Ceres, the spot remains. In the animated image, below, the spot almost seems to glint in the sunlight.

What is it?


Animation of Ceres made from Dawn images acquired on Jan. 13, 2015 (Credit: NASA/JPL-Caltech/UCLA/MPS/DLR/IDA/PSI)


Animation of Ceres made from Dawn images acquired on Jan. 13, 2015 (Credit: NASA/JPL-Caltech/UCLA/MPS/DLR/IDA/PSI)
One of the most anticipated aspects the Dawn spacecraft being in orbit around Ceres HAS to be finding out what this spot is. It could be ice, it could be a cryovolcano or geysers, or it could be something else. But we do know fairly certain that it is a real feature and not an image artifact, since it shows up in most of the recent Hubble images and now the Dawn images.

Planetary scientists have long suspected that water ice may be buried under Cere’s crust. A few things point to subsurface ice: the density of Ceres is less than that of the Earth’s crust, and because the surface bears spectral evidence of water-bearing minerals. Scientists estimate that if Ceres were composed of 25 percent water, it may have more water than all the fresh water on Earth. Ceres’ water, unlike Earth’s, would be in the form of water ice and located in the mantle, which wraps around the asteroid’s solid core.

And then last year, the Herschel space telescope discovered water vapor around Ceres, and the vapor could be emanating from water plumes — much like those that are on Saturn’s moon Enceladus – or it could be from cryovolcanism from geysers or icy volcanoes. Without huge a planet or satellite nearby tugging on it, the mechanism for how Ceres is active is also intriguing.

Images from the Hubble Space Telescope in 2004 of Ceres. Credit: NASA/Hubble.


Images from the Hubble Space Telescope in 2004 of Ceres. Credit: NASA/Hubble.
Some scientists also think Ceres may have an ocean and possibly an atmosphere.

As we discussed in our article yesterday, with all that water potentially at Ceres, could it theoretically host microbial life? Some scientists have hinted that Ceres and other icy bodies could be a possible source for life on Earth, another intriguing proposition.

Yesterday, I asked Dawn scientist Paul Schenk what other factors would have to be present in order for microbial life to have arisen on Ceres.

“The presence of carbon molecules is often regarded as necessary for life,” he replied, “and we think we see that on the surface spectroscopically in the form of carbonates and clays. So, I think the questions will be, whether there is actually liquid water of any kind, whether the carbon compounds are just a surface coating or in the interior, and whether Ceres has ever been warm. If those are true then some sort of prebiotic or biotic activity is in play.”

And we’ll soon find out more about this intriguing dwarf planet.

This processed image, taken Jan. 13, 2015, shows the dwarf planet Ceres as seen from the Dawn spacecraft. The image hints at craters on the surface of Ceres. Dawn's framing camera took this image at 238,000 miles (383,000 kilometers) from Ceres. Credit: NASA/JPL-Caltech/UCLA/MPS/DLR/IDA


This processed image, taken Jan. 13, 2015, shows the dwarf planet Ceres as seen from the Dawn spacecraft. The image hints at craters on the surface of Ceres. Dawn’s framing camera took this image at 238,000 miles (383,000 kilometers) from Ceres. Credit:
NASA/JPL-Caltech/UCLA/MPS/DLR/IDA
As the deputy principal investigator for Dawn, Carol Raymond said following the Herschel water vapor discovery, “We’ve got a spacecraft on the way to Ceres, so we don’t have to wait long before getting more context on this intriguing result, right from the source itself.”

NASA says that Dawn’s images will surpass Hubble’s resolution at the next imaging opportunity, which will be at the end of January.

The spacecraft arrives at Ceres on March 6, when it will be captured into orbit. The images will continue to improve as the spacecraft spirals closer to the surface during its 16-month study of the dwarf planet. Dawn will eventually be about 1,000 times closer to Ceres than it was for the images released yesterday and therefore will provide 1,000 times as much detail. Dawn at Ceres is primarily a mapping mission, so it will map the geology and chemistry of the surface in high resolution.

It should reveal the processes that drive the outgassing activity, and it should reveal how much water this dwarf planet holds.

And it should reveal the mystery of that white spot.

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If Earth Had Saturn’s Rings, This is What it Would Look Like

If Earth Had Saturn’s Rings, This is What it Would Look Like:

A graphic depicting Earth and Saturn's rings to scale. Credit: John Brady/Astronomy Central.


A graphic depicting Earth and Saturn’s rings to scale. Credit: John Brady/Astronomy Central.
We Earthlings love to dream, conjure and extrapolate. If you pose a question such as, “What if Earth had Saturn’s rings?” with all the resources available these days someone will not only answer the question but create some beautiful graphics to depict it! Yesterday, we saw this amazing graphic posted on reddit of a to-scale depiction of how Earth would look like with Saturn’s rings, and thanks to those who helped find the original source, the original image was created by John Brady at Astronomy Central. (We apologize… we originally credited the wrong person).


Of course, “What if Earth had Saturn’s rings?” is not a new question. In fact we’ve discussed it previously on Universe Today, and in 2013, illustrator and author Ron Miller put together some incredible visualizations of what Earth’s skies would look like with Saturn’s rings.

Also, last year someone on imgur put together a wonderful set of images of Earth with Saturn’s rings, as it would look from Earth’s Moon:

This video depicts rings around Earth, but the scale of the rings are not the size of Saturn’s:



Phil Plait discussed the problems that might arise for us if there were Earthrings, such as the rings would change the amount of sunlight reaching the Earth, and our view of the night sky would be hampered. And then Earth could potentially be shredded by ring debris.

Oh well, we can dream, can’t we?

See more great size comparisons of things in our Solar System and Universe at John Brady’s post on Astronomy Central, including a look at how many Earth’s would span across Saturn’s rings.

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A Swirling Vortex at Venus’ South Pole

A Swirling Vortex at Venus’ South Pole:

A mass of swirling gas and cloud at Venus’ south pole. Credit: ESA/VIRTIS/INAF-IASF/Obs. de Paris-LESIA/Univ. Oxford.


A mass of swirling gas and cloud at Venus’ south pole. Credit: ESA/VIRTIS/INAF-IASF/Obs. de Paris-LESIA/Univ. Oxford.
Here’s the latest view of the mass of swirling gas and clouds at Venus’ south pole. The Venus Express’s Visible and Infrared Thermal Imaging Spectrometer (VIRTIS) has been keeping an eye on this polar vortex since the spacecraft arrived and discovered this huge storm in 2006. During the mission, VIRTIS has seen the vortex constantly transform, morphing from a double vortex into a squashed shape and into the eye-like structure seen here.



This image was taken in April 2007 but was just released this week.

Venus has a very choppy and fast-moving atmosphere, even though wind speeds are much slower at the planet’s surface. At the cloud tops about 70 km above the surface, winds can reach 400 km/h. At this altitude, Venus’ atmosphere spins about 60 times faster than the planet itself. Compared to Earth, this is a dizzying speed: even Earth’s fastest winds move at most about 30% of our planet’s rotation speed.

These polar vortices form when heated air from equatorial latitudes rises and spirals towards the poles, carried by the fast winds. As the air converges on the pole and then sinks.

High velocity winds spin westwards around the planet, and take just four days to complete a rotation. This ‘super-rotation’, combined with the natural recycling of hot air in the atmosphere, would induce the formation of a vortex structure over each pole.

A video of the vortex, made from 10 images taken over a period of five hours, can be seen here. The vortex rotates with a period of around 44 hours.

Source: ESA

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Monday, January 19, 2015

Comet Finlay Surprise Outburst, Visible in Binoculars … again!

Comet Finlay Surprise Outburst, Visible in Binoculars … again!:

Comet Finlay in outburst on the evening (CST) of January 16th. Credit: Michael Mattiazzo


Comet Finlay’s up to its old shenanigans again. Here we see it in outburst with a bright, compact head and a half-degree-long tail pointing northeast on Friday, January 16th. Credit: Michael Mattiazzo
Lost sleep at night, fingers tapping on the keyboard by day. Darn comets are keeping me busy! But of course that’s a good problem. Comet 15P/Finlay, which had been languishing in the western sky at dusk at magnitude +10, has suddenly come to life … for a second time.

Two nights ago, Australian comet observer Michael Mattiazzo took a routine picture of Finlay and discovered it at magnitude +8. Today it’s a magnitude brighter and now joins Comet Lovejoy as the second binocular comet of 2015. Comet-wise, we’ve gone from zero to 60 and the new year’s fewer than 3 weeks old!

Comet 15P/Finlay tonight through Feb. 1. Positions shown for 7 p.m (CST) and stars depicted to magnitude +8. Tonight the comet will be right next to a 6th mag. star in Aquarius.


Comet 15P/Finlay tonight through Feb. 1. Positions shown for 7 p.m (CST) and stars depicted to magnitude +8. Tonight the comet will be right next to a 6th mag. star in Aquarius low in the southwestern sky at nightfall. Mars and Neptune’s position are for Jan. 17th. Click to enlarge. Source: Chris Marriott’s SkyMap software
Comet Finlay’s threw its first tantrum last December when it reached binocular visibility (faintly) shortly before Christmas.  Discovered by William Henry Finlay from South Africa on September 26, 1886, the comet circles the Sun every 6.5 years. This time around it reached perihelion on December 27th and spent many nights near the planet Mars low in the western sky. Until the new outburst, the comet had returned to its predicted brightness (~10 magnitude) and departed company with the Red Planet.

Even though photographed under poor conditions on Jan. 17th, Alfons Diepvens' image of Comet Finlay's coma and nuclear region reveals interesting details. Credit: Alfons Diepvens


Even though photographed under poor conditions on Jan. 17th, Belgian amateur astronomer Alfons Diepvens’ image of Comet Finlay’s coma and nuclear region reveals interesting details. Credit: Alfons Diepvens
It’s still low in the west, though not quite so much as in December, in the constellation Aquarius. With an orbit inclined only 6.8° to the ecliptic or plane of the Solar System, you’ll find it chugging eastward across the zodiac at the rate of 1° per night. The best time to view the comet is at the end of evening twilight at nightfall when it’s highest —  20° to 25° above the southwestern horizon.

Comet Lovejoy southwest of the beautiful Pleaides star cluster on January 15th. Credit: Bob King


Comet Lovejoy seen in tandem with the beautiful Pleaides star cluster on January 15th. Click for a finder chart. Credit: Bob King
Right now it’s not far from Lambda Aquarii and will soon glide just south of the well-known asterism called the “Circlet” in Pisces. Currently between 7th and 8th magnitude and showing a bright, condensed center, Comet Finlay is easily visible in 10×50 binoculars. Catch it while you can. These outbursts often fade fairly quickly. While we don’t know its exact cause, what likely happened is that a new fissure opened up on the comet’s surface, exposing fresh ice to sunlight. Rapid vaporization of the new material may be behind the eruption.

While Comet Q2 Lovejoy’s been getting all the attention, Finlay’s back in the game and making mid-January nights all that more enjoyable for sky gazing. Lovejoy is presently passing near the Pleiades star cluster in Taurus. This coming week will be the last dark one before the Moon starts to spoil the view. I hope you’re able to spot both at the next opportunity.

5-degree binocular view of Mars as it approaches Neptune in the next few nights. They'll be in close conjunction on the 19th. Mars shines at about 1st magnitude, Neptune at 8. Stars shown to mag. 9. Source: Chris Marriott's SkyMap software


5-degree binocular view of Mars as it approaches Neptune in the next few nights. They’ll be in close conjunction on the 19th. Mars shines at about 1st magnitude, Neptune at 8. Stars shown to mag. 9. Source: Chris Marriott’s SkyMap software
While we’re on the topic, take another look at the finder chart and you’ll see that Mars lies very near Neptune. The two are presently about 2° apart but on Monday Jan. 19th at dusk they’ll be separated by just 12 arc minutes or 1/5 of a degree and easily fit into the same medium-power view of a telescope. Pretty cool – and well worth seeing along with those comets!



About 

I'm a long-time amateur astronomer and member of the American Association of Variable Star Observers (AAVSO). My observing passions include everything from auroras to Z Cam stars. Every day the universe offers up something both beautiful and thought-provoking. I also write a daily astronomy blog called Astro Bob.

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