Astronomy Archives

November 4, 2014December 23, 2015 by Nancy Atkinson

Mysterious Object “G2” at Galactic Center is Actually Binary Star

An image from W. M. Keck Observatory near infrared data shows that G2 survived its closest approach to the black hole and continues happily on its orbit. The green circle just to its right depicts the location of the invisible supermassive black hole. Credit: Andrea Ghez, Gunther Witzel/UCLA Galactic Center Group/W. M. Keck Observatory

A mysterious object swinging around the supermassive black hole in the center our galaxy has surprised astronomers by actually surviving what many thought would be a devastating encounter. And with its survival, researchers have finally been able to solve the conundrum of what the object – known as G2 — actually is. Since G2 was discovered in 2011, there was a debate whether it was a huge cloud of hydrogen gas or a star surrounded by gas. Turns out, it was neither … or actually, all of the above, and more.

Astronomers now say that G2 is most likely a pair of binary stars that had been orbiting the black hole in tandem and merged together into an extremely large star, cloaked in gas and dust.

“G2 survived and continued happily on its orbit; a simple gas cloud would not have done that,” said Andrea Ghez from UCLA, who has led the observations of G2. “G2 was basically unaffected by the black hole. There were no fireworks.”

This was one of the “most watched” recent events in astronomy, since it was the first time astronomers have been able to view an encounter with a black hole like this in “real time.” The thought was that watching G2’s demise would not only reveal what this object was, but also provide more information on how matter behaves near black holes and how supermassive black holes “eat” and evolve.

The two Keck 10-meter domes atop Mauna Kea. (Rick Peterson/WMKO)

Using the Keck Observatory, Ghez and her team have been able to keep an eye on G2’s movements and how the black hole’s powerful gravitational field affected it.

While some researchers initially thought G2 was a gas cloud, others argued that they weren’t seeing the amount of stretching or “spaghettification” that would be expected if this was just a cloud of gas.

As Ghez told Universe Today earlier this year, she thought it was a star. “Its orbit looks so much like the orbits of other stars,” she said. “There’s clearly some phenomenon that is happening, and there is some layer of gas that’s interacting because you see the tidal stretching, but that doesn’t prevent a star being in the center.”

Now, after watching the object the past few months, Ghez said G2 appears to be just one of an emerging class of stars near the black hole that are created because the black hole’s powerful gravity drives binary stars to merge into one. She also noted that, in our galaxy, massive stars primarily come in pairs. She says the star suffered an abrasion to its outer layer but otherwise will be fine.

Ghez explained in a UCLA press release that when two stars near the black hole merge into one, the star expands for more than 1 million years before it settles back down.

“This may be happening more than we thought. The stars at the center of the galaxy are massive and mostly binaries,” she said. “It’s possible that many of the stars we’ve been watching and not understanding may be the end product of mergers that are calm now.”

Ghez and her colleagues also determined that G2 appears to be in that inflated stage now and is still undergoing some spaghettification, where it is being elongated. At the same time, the gas at G2’s surface is being heated by stars around it, creating an enormous cloud of gas and dust that has shrouded most of the massive star.

Usually in astrophysics, timescales of events taking place are very long — not over the course of several months. But it’s important to note that G2 actually made this journey around the galactic center around 25,000 years ago. Because of the amount of time it takes light to travel, we can only now observe this event which happened long ago.

“We are seeing phenomena about black holes that you can’t watch anywhere else in the universe,” Ghez added. “We are starting to understand the physics of black holes in a way that has never been possible before.”

The research has been published in the journal Astrophysical Journal Letters.

Observing Challenge: Catch a Series of Mutual Eclipses by Jupiter’s Moons

Missing the planets this month? With Mars receding slowly to the west behind the Sun at dusk, the early evening sky is nearly devoid of planetary action in the month of November 2014. Stay up until about midnight local, however, and brilliant Jupiter can be seen rising to the east. Well placed for northern hemisphere viewers in the constellation Leo, Jupiter is about to become a common fixture in the late evening sky as it heads towards opposition next year in early February.

The line-up during the November 25th eclipse event (see chart below). Note that Jupiter’s moons are in 1-2-3-4 order! Credit: Stellarium.

An interesting phenomenon also reaches its climax, as we make the first of a series of passes through the ring plane of Jupiter’s moons this week on November 8^th, 2014. This means that we’re currently in a season where Jupiter’s major moons not only pass in front of each other, but actually eclipse and occult one another on occasion as they cast their shadows out across space.

These types of events are challenging but tough to see, owing to the relatively tiny size of Jupiter’s moons. Followers of the giant planet are familiar with the ballet performed by the four large Jovian moons of Io, Europa, Ganymede, and Callisto. This was one of the first things that Galileo documented when he turned his crude telescope towards Jupiter in late 1609. The shadows the moons cast back on the Jovian cloud tops are a familiar sight, easily visible in a small telescope. Errors in the predictions for such passages provided 17^th century Danish astronomer Ole Rømer with a way to measure the speed of light, and handy predictions of the phenomena for Jupiter’s moons can be found here.

A look at selected upcoming occultation events. Credit: Starry Night.

Credit and copyright Christoper Go, used with permission.

Mutual occultations and eclipses of the Jovian moons are much tougher to see. The moons range in size from 3,121 km (Europa) to 5,262 km (Ganymede), which translates to 0.8”-1.7” in apparent diameter as seen from the Earth. This means that the moons only look like tiny +6^th magnitude stars even at high magnification, though sophisticated webcam imagers such as Michael Phillips and Christopher Go have managed to actually capture disks and tease out detail on the tiny moons.

Author — A double shadow transit from 2013. Photo by author.

What is most apparent during these mutual events is a slow but steady drop in combined magnitude, akin to that of an eclipsing variable star such as Algol. Running video, Australian astronomer David Herald has managed to document this drop during the 2009 season (see the video above) and produce an effective light curve using LiMovie.

Such events occur as we cross through the orbital planes of Jupiter’s moons. The paths of the moons do not stray more than one-half of a degree in inclination from Jupiter’s equatorial plane, which itself is tilted 3.1 degrees relative to the giant planet’s orbit. Finally, Jupiter’s orbit is tilted 1.3 degrees relative to the ecliptic. Plane crossings as seen from the Earth occur once every 5-6 years, with the last series transpiring in 2009, and the next set due to begin around 2020. Incidentally, the slight tilt described above also means that the outermost moon Callisto is the only moon that can ‘miss’ Jupiter’s shadow on in-between years. Callisto begins to so once again in July 2016.

Mutual events for the four Galilean moons come in six different flavors:

This month, Jupiter reaches western quadrature on November 14th, meaning that Jupiter and its moons sit 90 degrees from the Sun and cast their shadows far off to the side as seen from the Earth. This margin slims as the world heads towards opposition on February 6^th, 2015, and Jupiter once again joins the evening lineup of planets.

Early November sees Jupiter rising around 1:00 AM local, about six hours prior to sunrise. Jupiter is also currently well placed for northern hemisphere viewers crossing the constellation Leo.

The Institut de Mécanique Céleste et de Calcul des Éphémérides (IMCCEE) based in France maintains an extensive page following the science and the circumstances for the previous 2009 campaign and the ongoing 2015 season.

We also distilled down a table of key events for North America coming up through November and December:

Fun fact: we also discovered during our research for this piece that these events can also produce a total solar eclipse very similar to the near perfect circumstances enjoyed on the Earth via our Moon:

Note that this season also produces another triple shadow transit on January 24^th, 2015.

Observing and recording these fascinating events is as simple as running video at key times. If you’ve imaged Jupiter and its moons via our handy homemade webcam method, you also possess the means to capture and analyze the eclipses and occultations of Jupiter’s moons.

Credit NASA/JPL — A view never seen from the Earth… Io (upper left) paired with a crescent Europa during New Horizons’ 2007 flyby. Credit: NASA/JPL.

Good luck, and let us know of your tales of astronomical tribulation and triumph!

November 3, 2014December 23, 2015 by Shannon Hall

Hubble Spots the Ghostly Light From Dead Galaxies

Hubble Frontier Fields observing programme, which is using the magnifying power of enormous galaxy clusters to peer deep into the distant Universe. Credit: NASA.

In a patch of sky 3.5 billion light-years away there are hazy elliptical galaxies, colorful spirals, blue arcs and distorted shapes seen clumping together. It’s the result of a vast cosmic collision that took place over the course of 350 million years.

The mess is a treasure trove of information for astronomers, allowing them to piece together the history of a cosmic pile-up of multiple galaxy clusters.

But now astronomers are digging through the nearby darkness. They’re eyeing the remnant stars that were cast adrift in intergalactic space. These stars should emit a faint glow known as intracluster light that — until now — has mostly remained a subject of speculation.

Mireia Montes and Ignacio Trujillo, both from the University of La Laguna, Spain, have used the Hubble Space Telescope to observe the aforementioned cluster, Abel 2744, in exquisite detail. The cluster has already earned the nickname Pandora’s Cluster for its violent past.

The team looked at both visible and near-infrared color images of the cluster, and then split these color images by brightness. This allowed Montes and Trujillo to pinpoint the color of the cluster’s faintest glow and therefore glean the ghost stars’ age, chemical content, and total mass.

Compared to stars within the cluster’s galaxies, the ghost stars emit bluer light and are therefore rich in heavier elements like oxygen, carbon, and nitrogen. So the scattered stars must be second- or third-generation stars enriched by previous supernovae. But they’re still between three and nine billion years younger than the stars within the cluster’s galaxies.

The team estimates that the combined light of about 100 billion outcast stars contributes approximately six percent of the cluster’s brightness.

But how did the stars get thrown from their respective galaxies in the first place? This new forensic evidence suggests that violent collisions tore apart between four and six Milky Way-size galaxies, scattering their stars into intergalactic space.

“The Hubble data revealing the ghost light are important steps forward in understanding the evolution of galaxy clusters,” said Trujillo in a news release. “It is also amazingly beautiful in that we found the telltale glow by utilizing Hubble’s unique capabilities.”

Abell 2744 is only one target in Hubble’s Frontier Fields program, which will map five more galaxy clusters in superb detail.

The results have been published in the Astrophysical Journal and are available online.

October 31, 2014December 23, 2015 by Bob King

Earth Dodges a Bullet — New Radar Images of Asteroid 2014 SC324

Goldstone delay-Doppler images of 2014 SC324 obtained on October 25. The images span an interval of about 45 minutes and show considerable rotation by this object, which has an irregular and elongated shape. Credit: NASA/JPL

Looks like we dodged a bullet. A bullet-shaped asteroid that is. The 70-meter Goldstone radar dish, part of NASA’s Deep Space Network, grabbed a collage of photos of Earth-approaching asteroid 2014 SC324 during its close flyby last Friday October 24. These are the first-ever photos of the space rock which was discovered September 30 this year by the Mt. Lemmon Survey. The level of detail is amazing considering that the object is only about 197 feet (60-meters) across. You can also see how incredibly fast it’s rotating – about 30-45 minutes for a one spin.

A cropped version of the photo to more clearly see the asteroid's shape. 2014 SC324 passed just 1.5 lunar distances from Earth last week. Credit: NASA/JPL — A cropped version of the photo to more clearly see the asteroid’s shape. 2014 SC324 passed just 1.5 lunar distances from Earth last week. Credit: NASA/JPL

In the cropped version, the shape is somewhat clearer with the asteroid appearing some four times longer than wide. 2014 SC324 belongs to the Apollo asteroid class, named for 1862 Apollo discovered in 1932 by German astronomer Karl Reinmuth. Apollo asteroids follow orbits that occasionally cross that of Earth’s, making them a potential threat to our planet. The famed February 15, 2013 Chelyabinsk fireball, with an approximate pre-atmospheric entry size of 59 feet (18-m), belonged to the Apollo class.

Three classes of asteroids that pass near Earth or cross its orbit are named for the first member discovered — Apollo, Aten and Amor. Apollo asteroids like 2014 SC324 routinely cross Earth’s orbit, Atens also cross but have different orbital characteristics and Amors cross Mars’ orbit but miss Earth’s. Credit: ESA

Lance Benner and colleagues at Goldstone also imaged another Apollo asteroid that passed through our neighborhood on October 19 called 2014 SM143. This larger object, estimated at around 650 feet (200-m) across, was discovered with the Pan-STARRS 1 telescope on Mt. Haleakala in Hawaii on September 17. Tell me we’re not some shiny ball on a solar system-sized pool table where the players fortunately miss their shot … most of the time.

October 30, 2014December 23, 2015 by Bob King

Possible Bright Supernova Lights Up Spiral Galaxy M61

An animation showing a comparison between the confirmation image (at top) and an archive photo. Credit: Ernesto Guido, Martino Nicolini, Nick Howes

I sat straight up in my seat when I learned of the discovery of a possible new supernova in the bright Virgo galaxy M61. Since bright usually means close, this newly exploding star may soon become visible in smaller telescopes. It was discovered at magnitude +13.6 on October 29th by Koichi Itagaki of Japan, a prolific hunter of supernovae with 94 discoveries or co-discoveries to his credit. Itagaki used a CCD camera and 19.6-inch (0.50-m) reflector to spy the new star within one of the galaxy’s prominent spiral arms. Comparison with earlier photos showed no star at the position. Itagaki also nabbed not one but two earlier supernovae in M61 in December 2008 and November 2006.

The possible supernova in the bright galaxy M61 in Virgo is located 40" east and 7" south of the galaxy's core at right ascension (RA) 12 h 22', declination (Dec) +4º 28' It's currently magnitude +13.4 and visible in the morning sky before dawn in 8-inch and larger telescopes. Credit: Ernesto Guido, Martino Nicolini, Nick Howes — The possible supernova in the bright galaxy M61 in Virgo is located 40″ east and 7″ south of the galaxy’s core at right ascension (RA) 12 h 22′, declination (Dec) +4º 28′. It’s currently magnitude +13.4 and visible in the morning sky before dawn in 8-inch and larger telescopes. Credit: Ernesto Guido, Martino Nicolini, Nick Howes

Overnight, Ernesto Guido and crew used a remote telescope in New Mexico to confirm the new object. We’re still waiting for a spectrum to be absolutely sure this is the real deal and also to determine what type of explosion occurred. In the meantime, it may well brighten in the coming mornings.

M61 is a beautiful barred spiral galaxy located about 55 million light years from Earth in the constellation Virgo. It's one of the few galaxies to show spiral structure in smaller telescopes. Credit: Hunter Wilson — M61 is a beautiful barred spiral galaxy located about 55 million light years from Earth in the constellation Virgo. It’s one of the few galaxies to show spiral structure in smaller telescopes. Credit: Hunter Wilson

Supernovae are divided into two broad categories – Type Ia and Type II. In a Type Ia event, a planet-sized white dwarf star in close orbit around a normal star siphons off matter from its companion which builds up on the surface of the dwarf until it reaches critical mass at which point the core ignites and consumes itself and the star in one titanic nuclear fusion reaction. A cataclysmic explosion ensues as the star self-destructs in blaze of glory.

Evolution of a Type Ia supernova. Credit: NASA/ESA/A. Feild

Type Ia explosions can become 5 billion times brighter than the Sun – the reason we can see them across so many light years – and eject matter into space at 5,000 – 20,000 km/second. Type II events mark the end of the life of a massive supergiant star. As these behemoths age, they burn by fusing heavier and heavier elements in their cores from hydrogen to carbon to silicon and finally, iron-nickel. Iron is inert and can’t be cooked or fused to create more energy. The star’s internal heat source, which has been staving back the force of gravity all these millions of years, shuts down. Gravity takes hold with a vengeance, the star quickly collapses then rebounds in a titanic explosion. Ka-boom!

Artist's impression of a Type II supernova explosion which involves the destruction of a massive supergiant star. Credit: ESO — Artist’s impression of a Type II supernova explosion which involves the destruction of a massive supergiant star. Credit: ESO

Like the Type Ia event, a Type II supernova grows to fantastic brilliance. Besides a legacy of radiant light, star debris, the creation of heavy elements like gold and lead, a Type II event will sometimes leave behind a tiny, city-sized, rapidly-spinning neutron star – the much compressed core of the original star – or even a black hole. So yes, life can continue for a giant star after a supernova event. But like seeing a former classmate at your 40th high school reunion, you’d hardly recognize it.

The "Y" or cup of Virgo rises into good view shortly before the start of dawn or about 2 hours before sunrise. This map shows the sky facing east around 6 a.m. local time (DST) and 5 a.m. starting Sunday when Daylight Saving Time is done. Source: Stellarium — The “Y” or “cup” of Virgo rises into good view shortly before the start of dawn or about 2 hours before sunrise. This map shows the sky facing east around 6 a.m. local time (DST) tomorrow October 31 and 5 a.m. standard time starting Sunday when Daylight Saving Time ends. Source: Stellarium

Are you itching to see this new supernova for yourself? Here are a couple maps to help you find it. M61 is located in the middle of the “Y” of Virgo not far from the familiar bright double star Gamma Virginis. From many locations, the galaxy climbs to 15-20° altitude in the east-southeast sky just before the start of dawn, just high enough for a good view. Once you find the galaxy, look for a small “star” superimposed on its eastern spiral arm as shown in the photo at the top of this article.

In this close up view, stars are shown to magnitude +7.5. M61 is right between 16 and 17 Virginis (magnitudes 5 and 6.5 respectively). Source: Stellarium — In this close up view, stars are shown to magnitude +7.5. M61 is right between 16 and 17 Virginis (magnitudes 5 and 6.5 respectively). Click to enlarge. Source: Stellarium

I’ll be out there with my scope watching and will report back once it’s established what type of supernova happens to be blowing up in our eyepieces. More information about the new object can be found anytime at David Bishop’s Latest Supernovae site. Good luck, clear skies!

** Update Nov. 1 : M61’s supernova now has a name and type! SN 2014dt is a Type Ia (exploding white dwarf) with some peculiarities in its spectrum. It’s also little brighter at magnitude +13.2.

October 30, 2014December 23, 2015 by David Dickinson

Mercury Pierces the Zodiacal Light at Dawn this Weekend

Psst! Ever spy the planet Mercury? The most bashful of all the naked eye planets makes its best dawn appearance of 2014 this weekend for northern hemisphere observers. And not only will Mercury be worth getting up for, but you’ll also stand a chance at nabbing that most elusive of astronomical phenomena — the zodiacal light — from a good dark sky sight.

DST note: This post was written whilst we we’re visiting Arizona, a land that, we’re happy to report, does not for the most part observe the archaic practice of Daylight Saving Time. Life goes on, zombies do not arise, and trains still run on time. In the surrounding world of North America, however, don’t forget to “fall back” one hour on Sunday morning, November 2^nd. I know, I know. Trust me, we didn’t design the wacky system we’re stuck with today. All times noted below post-shift reflect this change, but it also means that you’ll have to awaken an hour earlier Sunday November 2^nd onwards to begin your astronomical vigil for Mercury!

Oct21 to Nov14. Created using Starry Night Education Software. — The apparent daily path of Mercury as seen from 30 degrees north from October 21st to November 14th. Created using Starry Night Education Software.

Mercury starts the month of November reaching greatest elongation on Saturday, November 1^st at 18.7 degrees west of the Sun at 13:00 Universal Time UT/09:00 EDT. Look for Mercury about 10 degrees above the eastern horizon 40 minutes before sunrise. The planet Jupiter and the stars Denebola and Regulus make good morning guideposts to trace the line of the ecliptic down to the horizon to find -0.3 magnitude Mercury.

Mars, Mercury and the International Space Station. — Mars, Mercury and the International Space Station caught during an evening apparition in 2013. (Photo by author)

Sweeping along the horizon with binoculars, you may just be able to spy +0.2 magnitude Arcturus at a similar elevation to the northwest. The +1st magnitude star Spica also sits to Mercury’s lower right. Mercury passes 4.2 degrees north of Spica on November 4^th while both are still about 18 degrees from the Sun, making for a good study in contrast.

Later in the month, the old waning crescent Moon will present a challenge as it passes 2.1 degrees north of Mercury on November 21^st, though both will only be 9 degrees from the Sun on this date.

Mercury also passes 1.6 degrees south of Saturn November 26^th, but both are only 7 degrees from the Sun and unobservable at this point. But don’t despair, as you can always watch all of the planetary conjunction action via SOHO’s sunward staring LASCO C3 camera, which has a generous 15 degree field of view.

Mercury (the bright ‘star’ with spikes) transits SOHO’s LASCO C3 camera. Credit: NASA/ESA/SOHO.

At the eyepiece, Mercury starts off the month of November as a 57% illuminated gibbous disk about 7” in diameter. This will change to a 92% illuminated disk 5″ across on November 15^th, as the planet races towards superior conjunction on the far side of the Sun on December 8th. As with Venus, Mercury always emerges in the dawn sky as a crescent headed towards full phase, and the cycle reverses for both planets when they emerge in the dusk sky.

Why aren’t all appearances of Mercury the same? Mercury orbits the Sun once every 88 days, making greatest elongations of Mercury far from uncommon: on average, we get three dawn and three dusk apparitions of the innermost world per year, with a maximum of seven total possible. Two main factors come into play to assure that not all appearances of Mercury are created equal.

A depiction of the evening motion of Mercury and Venus as seen from Earth. Credit: NASA.

One is the angle of the ecliptic, which is the imaginary plane of our solar system that planets roughly follow traced out by the Earth’s orbit. In northern hemisphere Fall, this angle is at its closest to perpendicular at dawn, and the dusk angle is most favorable in the Spring. In the southern hemisphere, the situation is reversed. This serves to place Mercury as high as possible out of the atmospheric murk during favorable times, and shove it down into near invisibility during others.

The second factor is Mercury’s orbit. Mercury has the most elliptical orbit of any planet in our solar system at a value of 20.5% (0.205), with an aphelion of 69.8 million kilometres and perihelion 46 million kilometres from the Sun. This plays a more complicated role, as an elongation near perihelion only sees the planet venture 18.0 degrees from the Sun, while aphelion can see the planet range up to 27.8 degrees away. However, this distance variation also leads to noticeable changes in brightness that works to the advantage of Mercury spotters in the opposite direction. Mercury shines as bright as magnitude -0.3 at closer apparitions, to a full magnitude fainter at more distant ones at +0.7.

In the case of this weekend, greatest elongation for Mercury occurs just a week after perihelion, which transpired on October 25^th.

earlier 2014 Curiousity — Mercury transits the Sun earlier this year as captured by the Curiosity rover on Mars. Credit: NASA/JPL.

Mercury is also worth keeping an eye on in coming years, as it will also transit the Sun for the first time since 2006 on May 9^th, 2016. This will be visible for Europe and North America. We always thought it a bit strange that while rarer transits of Venus have yet to make their sci-fi theatrical debut, a transit of Mercury does crop up in the film Sunshine.

The first week of November is also a fine time to try and spy the zodiacal light. This is a cone-shaped glow following the plane of the ecliptic, resulting from sunlight backscattered across a dispersed layer of interplanetary dust. The zodiacal light was a common sight for us from the dark skies of Arizona, often rivaling the distant glow of Tucson over the mountains. The zodiacal light vanished from our view after moving to the humid and often light polluted U.S. East Coast, though we’re happy to report that we can once again spy it as we continue to traverse the U.S. southwest this Fall.

The zodiacal light captured by Cory Schmitz over the Drakensberg Mountains in South Africa. (Used with permission).

None other than rock legend Brian May of Queen fame wrote his PhD dissertation on the zodiacal light and the distribution and relative velocity of dust particles along the plane of the solar system. Having a dark site and a clear flat horizon is key to nabbing this bonus to your quest to cross Mercury off your life list this weekend!

October 29, 2014December 23, 2015 by Tammy Plotner

Double Disc Found Feeding Each Other In Binary Star System

This wide-field view shows the sky around the young multiple star system GG Tauri, which appears very close to the centre of this picture. This view also shows a dust cloud and evidence of star formation near the top of the picture. Credit: ESO/Digitized Sky Survey 2. Acknowledgement: Davide De Martin

Deep within the Taurus Dark Cloud complex, one of the closest star-forming regions to Earth has just revealed one of its secrets – an umbilical cord of gas flowing from the expansive outer disc toward the interior of a binary star system known as GG Tau-A. According to the ESO press release, this never-before-seen feature may be responsible for sustaining a second, smaller disc of planet-forming material that otherwise would have disappeared long ago.

A research group led by Anne Dutrey from the Laboratory of Astrophysics of Bordeaux, France and CNRS used the Atacama Large
Millimeter/submillimeter Array (ALMA) to observe the distribution of
dust and gas in the unusual GG Tau-A system. Since at least half of
Sun-like stars are the product of binary star systems, these type of
findings may produce even more fertile grounds for discovering
exoplanets. However, the 450 light year distant GG Tau system is even more complex than previously thought. Through observations taken with the VLTI, astronomers have discovered its primary star – home to the inner disc – is part of a more involved multiple-star system. The secondary star is also a close binary!

“We may be witnessing these types of exoplanetary systems in the midst of formation,” said Jeffrey Bary, an astronomer at Colgate University in Hamilton, N.Y., and co-author of the paper. “In a sense, we are learning why these seemingly strange systems exist.”

Let’s take a look…

This artist’s impression shows the dust and gas around the double star system GG Tauri-A. Researchers using ALMA have detected gas in the region between two discs in this binary system. This may allow planets to form in the gravitationally perturbed environment of the binary. Half of Sun-like stars are born in binary systems, meaning that these findings will have major consequences for the hunt for exoplanets.

“Like a wheel in a wheel, GG Tau-A contains a large, outer disc
encircling the entire system as well as an inner disc around the main central star. This second inner disc has a mass roughly equivalent to that of Jupiter.” says the research team. “Its presence has been an intriguing mystery for astronomers since it is losing material to its central star at a rate that should have depleted it long ago.”

Thanks to studies done with ALMA, the researchers made an exciting discovery in these disc structures… gas clumps located between the two. This observation could mean that material is being fed from the outer disc to feed the inner. Previously observations done with ALMA show that a single star pulls its materials inward from the outer disc. Is it possible these gas pockets in the double disc GG Tau-A system are creating a sustaining lifeline between the two?

“Material flowing through the cavity was predicted by computer
simulations but has not been imaged before. Detecting these clumps
indicates that material is moving between the discs, allowing one to
feed off the other,” explains Dutrey. “These observations demonstrate that material from the outer disc can sustain the inner disc for a long time. This has major consequences for potential planet formation.”

As we know, planets are created from the materials leftover from
stellar ignition. However, the creation of a solar system occurs at a snail’s pace, meaning that a debris disc with longevity is required for planet formation. Thanks to these new “disc feeding” observations from ALMA, researchers can surmise that other multiple-star systems behave in a similar manner… creating even more possibilities for exoplanet formation.

“This means that multiple star systems have a way to form planets, despite their complicated dynamics. Given that we continue to find interesting planetary systems, our observations provide a glimpse of the mechanisms that enable such systems to form,” concludes Bary.

During the initial phase of planetary searches, the emphasis was placed on Sun-like, single-host stars. Later on, binary systems gave rise to giant Jupiter-sized planets – nearly large enough to be stars on their own. Now the focus has turned to pointing our planetary discovery efforts towards individual members of multiple-systems.

Emmanuel Di Folco, co-author of the paper, concludes: “Almost half the Sun-like stars were born in binary systems. This means that we have found a mechanism to sustain planet formation that applies to a significant number of stars in the Milky Way. Our observations are a big step forward in truly understanding planet formation.”

Original Story Source: Planet-forming Lifeline Discovered in a Binary Star System ALMA Examines Ezekiel-like “Wheel in a Wheel” of Dust and Gas – ESO Science News Release.

October 28, 2014January 15, 2019 by Matt Williams

Just In Time for Halloween: Jupiter Gets a Giant Cyclops Eye!

Jupiter's Great Red Spot and Ganymede's Shadow. Image Credit: NASA/ESA/A. Simon (Goddard Space Flight Center)

Halloween is just around the corner. And in what appears to be an act of cosmic convergence, Hubble captured a spooky image of Jupiter staring back at us with a cyclops eye!

While this is merely a convenient illusion caused by the passage of Ganymede in front of Jupiter – something it does on a regular basis – the timing and appearance are perfect.

Continue reading “Just In Time for Halloween: Jupiter Gets a Giant Cyclops Eye!”

October 28, 2014January 15, 2019 by Matt Williams

100,000 Ice Blocks Mapped Out at the South Pole … of Enceladus

Cassini's view down into a jetting "tiger stripe" in August 2010. Credit: NASA

Ever since the Cassini space probe conducted its first flyby of Enceladus in 2005, the strange Saturnian moon has provided us with a treasure trove of images and scientific wonders. These include the jets of icy water vapor periodically bursting from its south pole, the possibility of an interior ocean – which may even harbor life – and the strange green-blue stripes located around the south pole.

Continue reading “100,000 Ice Blocks Mapped Out at the South Pole … of Enceladus”

October 28, 2014December 23, 2015 by David Dickinson

Comet K1 PanSTARRS: See It Now Before it Heads South

Comet C/2012 K1 PanSTARRS, one of the most dependable comets of 2014, may put on its encore performance over the coming weeks for southern hemisphere observers.

First, the story thus far. Discovered as a +19th magnitude smudge along the borders of the constellations Ophiuchus and Hercules in mid-May 2012 courtesy of the Panoramic Survey Telescope And Rapid Response System (PanSTARRS) based atop Haleakala on the Hawaiian island of Maui, astronomers soon realized that comet C/2012 K1 PanSTARRS would be something special.

The comet broke +10^th magnitude to become a visible binocular object in early 2014, and wowed northern hemisphere observers as it vaulted across the constellations of Boötes and Ursa Major this past spring.

NASA’s NEOWISE mission spies K1 PanSTARRS on May 20th as it slides by the galaxy NGC 3726 (blue). Credit: NASA/JPL.

The comet is approaching the inner solar system on a retrograde, highly-inclined orbit tilted 142 degrees relative the ecliptic. This bizarre orbit also assures that the comet will actually reach opposition twice in 2014 as seen from our earthly vantage point: once on April 15^th, and another opposition coming right up on November 7^th.

As was the case with comet Hale-Bopp way back in 1997, had C/2012 K1 PanSTARRS arrived six months earlier or later, we would’ve been in for a truly spectacular show, as the comet reached perihelion on August 27^th, 2014, only 0.05 A.U.s (4.6 million miles or 7.7 million kilometres) outside the orbit of the Earth! But such a spectacle was not to be… back in ’97, Hale-Bopp’s enormous size — featuring a nucleus estimated 40 to 60 kilometres across — made for a grand show regardless… fast forward to 2014, and the tinier nucleus of K1 PanSTARRS has been relegated to binocular status only.

From here on out, K1 PanSTARRS is headed south “with a bullet” and into memory for most northern hemisphere observers. We spied the comet this morning low to the south near +3^rd magnitude Nu Puppis in the pre-dawn sky with our trusty 15×45 binocs from Yuma, Arizona, for what will probably be our last time. This also means that the time to catch a last glimpse of K1 PanSTARRS for northern hemisphere viewers is now. This week sees the comet transiting just 20 degrees above the southern horizon at 3:00 to 4:00 AM local for observers based from latitude 30 degrees north as it crosses the constellation Puppis. The bright star Sirius nearly shares the same position as the comet in right ascension this week, and K1 PanSTARRS sits about 24 degrees south of the Dog Star.

K1 PanSTARRS jaicoa — Comet K1 PanSTARRS imaged on June 14th. Credit: Efrain Morales.

Halloween sees the comet even lower, crossing the southern meridian at only 13 degrees elevation as seen from latitude 30 degrees north. Draw a straight line from Sirius to the south celestial pole around this date to find the comet just 5 degrees to the north of Canopus.

But the show is just beginning for southern hemisphere residents. Observing from the town of Bright Australia, Robert Kaufmann recently noted in a posting on the Yahoo Groups Comet Observer’s message board that the comet currently exhibits a 4’ wide coma shining at about magnitude +7.3 with an elevation of 28 degrees above the horizon on October 25^th.

And if the comet holds steady in brightness, it may break the visual threshold and become a naked eye object as seen from a dark sky site in early November.

Light curve — The projected light curve of K1 PanSTARRS with brightness observations (black dots). The vertical pink line marks the comet’s perihelion passage in late August. Credit: Seiichi Yoshida’s *Weekly Information on Bright Comets*.

The comet will be literally “hauling tail” across the constellation Dorado as it nears its second opposition of the year on November 7^th, moving about 1.5 degrees a day – 3 times the apparent diameter of the Full Moon – on closest approach.

Currently, the comet has been observed to have an estimated magnitude holding steady at+7 and is predicted to peak at perhaps magnitude +6 early next month. And while it would’ve been great had it arrived 6 months earlier or later, the aforementioned high retrograde inclination of its orbit assured that K1 PanSTARRS was a top performer for both hemispheres in 2014.

Perihelion passage occurred two months ago, but to paraphrase a famous Monty Python skit, Comet K1 PanSTARRS is “not dead yet.” Here are some key observing dates coming right up as the comet gains prominence in the southern hemisphere sky:

(Note that close passages of less than one degree near stars +4^th magnitude or brighter only are mentioned).

Oct 31^st: Passes closest to Earth, at 0.953 A.U.s distant.

Nov 1^st: Crosses into the constellation Pictor.

Nov 2^nd: Passes near the +3.8 magnitude star Beta Pictoris.

Nov 6^th: Crosses into the constellation Dorado.

Nov 6^th: Full Moon occurs, marking the beginning of an unfavorable week for comet hunting.

Nov 7^th: The second opposition of the comet for 2014 occurs at 3:00 UT.

Nov 8^th: Passes near the +3.3 magnitude star Alpha Doradus.

Nov 11^th: Crosses into the constellation Reticulum.

Nov 13^th: Crosses into the constellation Horologium.

Nov 14^th: Passes 34 degrees from the South Celestial Pole.

Nov 20^th:Crosses into the constellation Eridanus.

Nov 22^nd: New Moon occurs, marking a week long span optimal for comet-hunting.

Nov 25^th: Crosses into the constellation Phoenix.

The path of K1 PanSTARRS from October 27th through December 1st. Created by the author using Starry Night Education Software.

Dec 6^th: Full Moon occurs.

Dec 12^th: Passes near the +2.8 magnitude star Alpha Phoenicis (Ankaa).

Dec 18^th: Crosses into the constellation Sculptor.

Dec 22^nd: New Moon occurs.

Looking at 2015, K1 PanSTARRS will probably fall back below +10^th magnitude by late January. The comet will then head back out into the depths of the outer solar system, its multi-million year orbit only slightly altered by its inner solar system passage down into the ~700,000 year range. What will Earth be like on that far off date? Will human eyes greet the comet once again, and will anyone remember its appearance way back in the mists of time in 2014? All thoughts to ponder as we bid fair well to Comet C/2012 K1 PanSTARRS, a fine binocular comet indeed.