A view of Sgr A* and the supermassive black hole located 26,000 light years from Earth in the center of the Milky Way. Credit: Chandra Telescope, NASA.
How do supermassive black holes form, and what role do they play in shaping galaxies and galaxy clusters? On Wednesday, September 11, 2013 at 19:00 UTC (12:00 p.m. PDT, 3:00 pm EDT) the Kavli Foundation is hosting a live Google+ Hangout to answer your questions about black holes. Participants in the Hangout will be Roger Blandford from the Kavli Institute for Particle Astrophysics and Cosmology at Stanford University, Priyamvada Natarajan from Yale University, and John Wise from the Georgia Institute of Technology.
You can watch live below. To submit questions ahead of time or during the webcast, email to [email protected] or post on Twitter with hashtag #KavliLive.
You can see more information about the webcast at the Kavli Foundation website. There will also be a followup Hangout on September 25 that will focus on black holes and the “firewall paradox” that made news in recent weeks, featuring noted researcher Leonard Susskind. We’ll post a new article with that webcast as the day approaches.
Spitzer image of an asteroid's surprise coma and tail (NASA/JPL-Caltech/DLR/NAU)
It’s a case of mistaken identity: a near-Earth asteroid with a peculiar orbit turns out not to be an asteroid at all, but a comet… and not some Sun-dried burnt-out briquette either but an actual active comet containing rock and dust as well as CO2 and water ice. The discovery not only realizes the true nature of one particular NEO but could also shed new light on the origins of water here on Earth.
JPL Near-Earth Object database map of 3552 Don Quixote’s orbit
Designated 3552 Don Quixote, the 19-km-wide object is the third largest near-Earth object — mostly rocky asteroids that orbit the Sun in the vicinity of Earth.
According to the IAU, an asteroid is coined a near-Earth object (NEO) when its trajectory brings it within 1.3 AU from the Sun and within 0.3 AU of Earth’s orbit.
About 5 percent of near-Earth asteroids are thought to actually be dead comets. Today an international team including Joshua Emery, assistant professor of earth and planetary sciences at the University of Tennessee, have announced that Don Quixote is neither.
An asteroid is coined a near-Earth object (NEO) when its trajectory brings it within 1.3 AU from the Sun and within 0.3 AU of Earth’s orbit. (IAU)
“Don Quixote has always been recognized as an oddball,” said Emery. “Its orbit brings it close to Earth, but also takes it way out past Jupiter. Such a vast orbit is similar to a comet’s, not an asteroid’s, which tend to be more circular — so people thought it was one that had shed all its ice deposits.”
Using the NASA/JPL Spitzer Space Telescope, the team — led by Michael Mommert of Northern Arizona University — reexamined images of Don Quixote from 2009 when it was at perihelion and found it had a coma and a faint tail.
Emery also reexamined images from 2004, when Quixote was at its farthest distance from the Sun, and determined that the surface is composed of silicate dust, which is similar to comet dust. He also determined that Don Quixote did not have a coma or tail at this distance, which is common for comets because they need the sun’s radiation to form the coma and the sun’s charged particles to form the tail.
The researchers also confirmed Don Quixote’s size and the low, comet-like reflectivity of its surface.
“The power of the Spitzer telescope allowed us to spot the coma and tail, which was not possible using optical telescopes on the ground,” said Emery. “We now think this body contains a lot of ice, including carbon dioxide and/or carbon monoxide ice, rather than just being rocky.”
This discovery implies that carbon dioxide and water ice might be present within other near-Earth asteroids and may also have implications for the origins of water on Earth, as comets are thought to be the source of at least some of it.
The amount of water on Don Quixote is estimated to be about 100 billion tons — roughly the same amount in Lake Tahoe.
“Our observations clearly show the presence of a coma and a tail which we identify as molecular line emission from CO2 and thermal emission from dust. Our discovery indicates that more NEOs may harbor volatiles than previously expected.”
– Mommert et al., “Cometary Activity in Near–Earth Asteroid (3552) Don Quixote “
The findings were presented Sept. 10 at the European Planetary Science Congress 2013 in London.
3552 Quixote isn’t the only asteroid found to exhibit comet-like behavior either — check out Elizabeth Howell’s recent article, “Asteroid vs. Comet: What the Heck is 3200 Phaethon?” for a look at another NEA with cometary aspirations.
We have another great giveaway lined up for all of our loyal readers. This one is quite cool. The Australian Amateur Astronomy group, “Ice in Space” created a contest for their members to submit their best astro photographs. The best images out of the 250 submitted were made into two calendars.
They are available for purchase if you are not feeling lucky enough to win one in this Universe Today giveaway.
Universe Today and Ice in Space would like to give away 5 free copies of each
calendar to 10 lucky winners. Here is how:
In order to be entered into the giveaway drawing, just put your email address into the box at the bottom of this post (where it says “Enter the Giveaway”) before Tuesday, September 17, 2013. We’ll send you a confirmation email, so you’ll need to click that to be entered into the drawing.
IceInSpace is a community website dedicated to promoting amateur astronomy in the southern hemisphere – including Australia, New Zealand, South America, Southern Africa and parts of Asia. We aim to help stargazers from around the world discover, discuss and enjoy the beauty of our night sky.
Artist's conception of the alien planet system orbiting Gliese 581. Credit: ESO/L. Calçada
One big challenge in astronomy is everything is so darn far away. This makes it hard to see the signs of life in planets, which are usually but tiny dots of light using the telescope technology we have today.
There are signs in Earth’s atmosphere that life is on the surface — methane from microbes, for example — and already scientists have years of research concerning ideas to find “biomarkers” on other planets. A new model focuses on a theoretical Earth-sized planet orbiting a red dwarf star, where it is believed biomarkers would be easier to find because these stars are smaller and fainter than that of the sun.
“We developed computer models of exoplanets which simulate the abundances of different biomarkers and the way they affect the light shining through a planet’s atmosphere,” stated Lee Grenfell, who is with the German Aerospace Center (DLR) institute of planetary science.
Preliminary work has already been done to find chemicals in the planet’s atmosphere (by looking at how they affect light that pass through the chemicals) particularly on large exoplanets that are close to their star (sometimes called “hot Jupiters“). Signs of life would be found through a similar process, but would be much fainter.
Artist’s impression of a red dwarf (courtesy NASA)
The research team constructed a model of a planet similar to Earth, at different orbits and distances from a red dwarf stars. Their work shows a sort of “Goldilocks” effect (or, a condition that is “just right”) to find ozone when the ultraviolet radiation falls into the medium of a given range. If it is too high, the UV heats the middle atmosphere and obliterates the biomarker signal. Too low UV makes the signal very hard to find.
“We find that variations in the UV emissions of red-dwarf stars have a potentially large impact on atmospheric biosignatures in simulations of Earth-like exoplanets. Our work emphasizes the need for future missions to characterise the UV emissions of this type of star,” said Grenfell.
The research has plenty of limitations, he added. We don’t know what alien life would look like, we don’t know if planets near red dwarfs are a good place to search, and even if we found a signal that looked like life, it could have come from another process. Still, Grenfell’s team expects the model is a good basis on which to continue asking the question: is life really out there?
The research has been submitted to the journal Planetary and Space Science.
A very zoomed-in image of Phaethon from NASA's STEREO spacecraft, showing a comet-like extension. Credit: Jewitt, Li, Agarwal /NASA/STEREO
Sometimes, putting things into categories difficult. Witness how many members of the general public are still unhappy that Pluto was reclassified as a dwarf planet, a decision made by the International Astronomical Union more than seven years ago.
And now we have 3200 Phaethon, an asteroid that is actually behaving like a comet. Scientists found dust that is streaming from this space rock as it gets close to the sun — similarly to how ices melt and form a tail as comets zoom by our closest stellar neighbor.
Phaethon’s orbit puts it in the same originating region as other asteroids (between Mars and Jupiter), but its dust stream is much closer to actions performed by a comet — an object that typically comes from an icy region way beyond Neptune. So far, therefore, the research team is calling Phaethon a “rock comet.” And after first proposing a theory a few years ago, they now have observations as to what may be going on.
Phaethon is not only an asteroid, but also a source of a prominent meteor shower called the Geminids. This shower happens every year around December when the Earth plows into the cloud of debris that Phaethon leaves in its wake. Astronomers have known about the Geminids’ source for a generation, but for decades could not catch the asteroid in the act of shedding its stuff.
That finally came with images of NASA’s twin sun-gazing Solar TErrestrial RElations Observatory (STEREO) spacecraft that were taken between 2009 and 2012. The researchers saw a “comet-like tail” extending from the 3.1-mile (five kilometer) asteroid. “The tail gives incontrovertible evidence that Phaethon ejects dust,” stated David Jewitt, an astronomer at the University of California, Los Angeles who led the research. “That still leaves the question: why?”
Time lapse-photo showing geminids over Pendleton, OR. Credit: Thomas W. Earle
The answer lies in just how close Phaethon whizzes past the sun. At perihelion, its closest approach to the sun, it only appears eight degrees (16 solar diameters) away from the sun in Earth’s sky. This close distance makes it all but impossible to study the asteroid without special equipment, which is why STEREO came in so handy.
When Phaethon reaches its closest approach of 0.14 Earth-sun distances, surface temperatures rise above an estimated 1,300 degrees Fahrenheit (700 degrees Celsius). It’ s way too hot for ice, as what happens with a comet. In fact, it’s probably hot enough to make the rocks crack and break apart. The researchers publicly hypothesized this was happening at least as far back as 2010, but this finding provided more evidence to support that theory.
“The team believes that thermal fracture and desiccation fracture (formed like mud cracks in a dry lake bed) may be launching small dust particles that are then picked up by sunlight and pushed into the tail,” a statement from the research team read.
“While this is the first time that thermal disintegration has been found to play an important role in the solar system,” they added, “astronomers have already detected unexpected amounts of hot dust around some nearby stars that might have been similarly produced.”
The results were presented at the European Planetary Science Congress on Tuesday. By the way, STEREO also caught Mercury behaving somewhat like a comet in results released in 2010, although that find was related to the planet’s escaping sodium atmosphere.
Read more about the research in the June 26 issue of Astrophysical Letters. A preprint version is also available on Arxiv.
The MESSENGER team celebrates 1,000 featured images of the innermost planet!
It’s been nearly two and a half years since the NASA-sponsored MESSENGER mission entered orbit around Mercury — the first spacecraft ever to do so — and today the MESSENGER team celebrated the 1,000th featured image on the mission site with a mosaic of discovery highlights, seen above.
“I thought it sensible to produce a collage for the 1,000th web image because of the sheer volume of images the team has already posted, as no single picture could encompass the enormous breadth of Mercury science covered in these postings,” explained MESSENGER Fellow Paul Byrne, of the Carnegie Institution of Washington. “Some of the images represent aspects of Mercury’s geological characteristics, and others are fun extras, such as the U.S. Postal Service’s Mercury stamp. The ‘1,000’ superimposed on the collage is a reminder of the major milestone the team has reached in posting 1,000 featured images — and even a motivation to post 1,000 more.”
See the very first image MESSENGER obtained from orbit below:
The Mercury Dual Imaging System (MDIS) team has posted a new image to the MESSENGER website approximately once per business day since March 29, 2011, when this first image of Mercury’s surface obtained from orbit was made public.
“During this two-year period, MESSENGER’s daily web image has been a successful mechanism for sharing results from the mission with the public at large,” said Nancy Chabot, MDIS Instrument Scientist at the Johns Hopkins University Applied Physics Laboratory (APL). Chabot has been leading the release of web images since MESSENGER’s first flyby of Mercury in January 2008.
“The first image I released was this one, as MESSENGER approached Mercury for the mission’s first Mercury flyby,” said Chabot. “Mercury was just a small crescent in the image, but it was still very exciting for me. We were obtaining the first spacecraft images of Mercury since Mariner 10 transmitted its final image in 1975, and this was just the beginning of the flood of images that followed.”
One of the first spacecraft images of Mercury since Mariner 10 transmitted its final image in 1975
The herculean effort involved in posting a new image every business day was made possible by a small team of scientists in addition to Chabot and Byrne, including APL’s David Blewett, Brett Denevi, Carolyn Ernst, Rachel Klima, Nori Laslo, and Heather Meyer.
“Creating images and captions for the MESSENGER Image Gallery has been fun and interesting,” Blewett said. “Working on a Gallery release gives me a chance take a break from my regular research and look all around Mercury’s surface for an image that the general public might find to be engaging from a scientific, artistic, or humorous perspective (and sometimes all three!).”
“The posting of the 1,000th image of Mercury on our web gallery is a wonderful benchmark, but there’s much more to come,” adds MESSENGER Principal Investigator Sean Solomon of Columbia University’s Lamont-Doherty Earth Observatory. “MESSENGER’s altitude at closest approach is steadily decreasing, and in a little more than six months our spacecraft will be able to view Mercury at closer range than ever before with each orbit. Stay tuned!”
Image credits: NASA/Johns Hopkins University Applied Physics Laboratory/Carnegie Institution of Washington
MESSENGER (MErcury Surface, Space ENvironment, GEochemistry, and Ranging) is a NASA-sponsored scientific investigation of the planet Mercury and the first space mission designed to orbit the planet closest to the Sun. The MESSENGER spacecraft launched on August 3, 2004, and entered orbit about Mercury on March 17, 2011 (March 18, 2011 UTC).
A while back we introduced you to Zogg the alien from Betelgeuse. Zogg has been busy helping aliens understand bizarre human concepts like “rituals” and “vision”, but he took a side journey to help everyone understand the geometry of the Universe. What does it mean to have a flat, finite Universe? How could you travel in one direction and return to your starting point?
The first episode was fantastic, and now serves as my favorite link to send people when they’re having trouble wrapping their head around the concept of a finite Universe. How the Universe can be expanding, without expanding into anything. Seriously, if you haven’t seen Part 1, stop and go watch it now.
True to his word, Zogg released this second episode, detailing the geometries of the Universe. What do cosmologists mean when they say the Universe is “curved” or “flat”. What could the curvature look like.
The crescent Moon and Venus as seen from São Paulo, Brazil on September 8, 2013. Credit and copyright: Ednilson Oliveira
Did you notice a bright “star” close to the Moon last night (September 8, 2013)? People around the world had the treat of seeing the waxing crescent Moon have the planet Venus snuggle up close… or in some places, the Moon actually passed in front of Venus, in what is known as an occultation. Also, on Saturday, the bright star Spica added to the scene.
Thanks to our readers from around the world for sharing their images and videos!
Moon and Venus conjunction over the Eternal Flame of the 9/11 Memorial located here in San Antonio, Texas. Credit and copyright: Adrian New.The Moon and Venus on September 8, 2013. Credit and copyright: Wes Schulstad.The waxing crescent Moon near Venus on the evening of Sunday, September 8, 2013, as seen from southern Alberta, Canada. Credit and copyright: Alan Dyer/Amazing Sky Photography.
Here’s a video showing the occultation of Venus by the Moon, photographed by Fabian Gonzalez.
The 12% waxing crescenet Moon and Venus on September 8, 2013 as seen from Shot in Kennesaw, Georgia. Credit and copyright: Stephen Rahn.The new Moon with Venus on its right. Taken from the dark sky preserve at the Nutwood Observatory in central Ontario, Cananda. Credit and copyright: Brian McGaffney.A close-up of September’s waxing crescent Moon with Venus on September 8, 2013. Credit and copyright: Tavi Greiner.A calm and peaceful moment on a beautiful beach, with a planetary alignment between planets, Saturn (in the top left corner), Venus and Spica star (in the center image), and the crescent Moon above the horizon, as seen on September 7, 2013. Credit and copyright: Miguel Claro.Conjunction of Saturn, Venus, and the 2.5 day old Moon on Saturday, September 7, 2013. Spica sneaks into the photo beneath Venus. Taken from Salem, Missouri. Credit and copyright: Joe Shuster, Lake County Astronomical Society.
Video of the occultation of Spica by the Moon on September 7, 2013 from Israel, taken by Gadi Eidelheit. Read more about at his website, VenusTransit.
Beautiful Moon & Venus as seen from Mumbai on 8th September 2013. Credit and copyright: Henna Khan.The crescent Moon and Venus as seen from central Illinois. Credit: Nancy Atkinson.
Want to get your astrophoto featured on Universe Today? Join our Flickr group or send us your images by email (this means you’re giving us permission to post them). Please explain what’s in the picture, when you took it, the equipment you used, etc.
The night sky just wouldn’t feel right without the Moon. Where did our our friendly, familiar satellite come from?
Scientists and philosophers have been wondering about this for centuries.
Once Copernicus gave us our current model of the Solar System, with the Earth as just another planet and the Sun at the centre of the Solar System, this gave us a new way of looking at the Moon.
The first modern idea about the formation of the Moon was called the fission theory, and it came from George Darwin, the son of Charles Darwin.
He reasoned the Moon must have broken away from our planet, when the Earth was still a rapidly rotating ball of molten rock.
His theory lasted from the 1800s right up until the space age.
Another idea is that the Earth captured the Moon after its formation.
Usually, these kinds of gravitational interactions don’t go well.
Models predict that either the Moon would collide with the Earth, or get flung out into a different orbit.
It’s possible that the early Earth’s atmosphere was much larger and thicker, and acted like a brake, modifying the Moon’s trajectory into a stable orbit around the Earth.
Or the Earth and Moon formed together in their current positions as a binary object, with Earth taking most of the mass and the Moon forming from the leftovers.
Artist’s impression of the impact that caused the formation of the Moon. Credit: NASA/GSFC
The most widely accepted theory is that the Moon was formed when a Mars-sized object slammed into the Earth, billions of years ago.
This collision turned the newly formed Earth into a molten ball of rock again, and ejected material into orbit.
Most of the material crashed back into the Earth, but some collected together from mutual gravity to form the Moon we have today.
This theory was first conceived in 1946 by Reginald Aldworth Daly from Harvard University. He challenged Darwin’s theory, calculating that just a piece of Earth breaking off couldn’t actually allow the Moon to get to its current position. He suggested an impact could do the trick though.
This idea wasn’t given much thought until a 1974 paper by Dr. William K. Hartmann and Dr. Donald R. Davis was published in the Journal Icarus. They suggested that the early Solar System was still filled with leftover moon-sized objects which were colliding with the planets.
The impact theory explained many of the challenges about the formation of the Moon. For example, one question was: why do the Earth and Moon have very different-sized cores.
After an impact from a Mars-sized planet, the lighter outer layers of the Earth would have been ejected into orbit and coalesced into the Moon, while the denser elements collected back together into the Earth.
It also helps explain how the Moon is on an inclined plane to the Earth. If the Earth and Moon formed together, they’d be perfectly lined up with the Sun.
But an impactor could come from any direction and carve out a moon. One surprising idea is that the impact actually created two moons for the Earth.
The two sides of the Moon. Image credit: LRO
The second, smaller object would have been unstable and eventually slammed into the far side of the Moon, explaining why the surface on the far side of the Moon is so different from the near side.
Even though we don’t know for sure how the Moon formed, the giant impact theory holds the most promise, and you can bet that scientists are continuing to look for clues to tell us more.
This week offers a fine chance to catch sight of a unique asteroid.
324 Bamberga reaches opposition this week in the constellation Pisces on (friggatriskaidekaphobics take note) Friday the 13th at 7AM EDT/11:00 Universal Time.
About 230 kilometres in size, 324 Bamberga reaches 0.81 astronomical units from the Earth this week. No other asteroid so large gets so close.
Discovered on February 25th, 1892 by Johann Palisa, 324 Bamberga only reaches a favorable opposition once every 22 years.
Shining at magnitude +8.1, 324 Bamberga is also one of the highest numbered asteroids visible with binoculars. Earth-crossing asteroids 433 Eros, which made a close pass last year, and 4179 Toutatis are two of the very few asteroids that possess a larger number designations that can regularly reach +10th magnitude.
Look east in mid-September about an hour after sunset. The inset covers the region that 324 Bamberga is currently traversing in the introductory graphic. (Created by the author using Stellarium).
So, why did it take so long for 324 Bamberga to be uncovered? One factor is its high orbital eccentricity of 0.34. This means that most of the oppositions of the asteroid aren’t favorable. 324 Bamberga orbits the Sun once every 4.395 years and only comes around to an opposition that lands near perihelion once every 22 Earth years. Perihelion this year occurs only 45 days after opposition on October 27th.
The resonance between 324 Bamberga and Earth is nearly five Earth orbits for every one circuit of the Sun for the asteroid and is offset by only 9 days, meaning that the 22 year window to see the asteroid will actually become less favorable in centuries to come. 324 Bamberga made its last favorable appearance on September 15th, 1991 and won’t surpass +10th magnitude again until September 2035.
Observing asteroids requires patience and the ability to pick out a slowly moving object amidst the starry background. 324 Bamberga spends September west of the circlet of Pisces, drifting two degrees a week, or just over 17’ a day, to cross over into the constellation Pegasus in early October.
324 Bamberga will be moving too slow to pick up any motion in real time, but you can spy it by either sketching the field on successive nights or photographing the region and noting if the asteroid can be seen changing position against the background of fixed stars. Start hunting for 324 Bamberga tonight, as the Full Harvest Moon will be visiting Pisces later next week on the 19th.
A closeup of the path of 324 Bamberga for the week of September 10-17th. Decimal points for comparison stars are omitted. (Created by the author using Starry Night Education software).
324 Bamberga is also unique as the brightest C-type asteroid that is ever visible from Earth. The runner up in this category is asteroid 10 Hygiea, which can shine a full magnitude fainter at opposition.
It’s also remarkable that Palisa actually managed to discover 324 Bamberga while it was at 12th magnitude! Palisa was one of the most prolific visual hunters of asteroids ever, discovering 121 asteroids from 1874 to 1923. He accomplished this feat first with the use of a 6” refractor while based at the Austrian Naval Observatory in Pola (now the Croatian town of Pula) and later using the Vienna observatory’s 27” inch refractor.
The Great Refractor of the University of Vienna used to discover asteroid 324 Bamberga. (Credit: Prof. Franz Kerschbaum, Wikimedia Commons image under an Attribution-Share Alike 3.0 Unported license).
324 Bamberga itself takes its name from the town of Bamberg in Bavaria, the site of the 1896 meeting of the Astronomische Gesellschraft.
An occultation of a star by 324 Bamberga on December 8th, 1987 allowed astronomers to pin down its approximate size. Searches have also been carried out during occultations for any possible moons of this asteroid, though thus far, none have been discovered.
It’s interesting to note that 324 Bamberga will also actually occult the star 2UCAC 3361042 tonight in the early morning hours at 8:59-9:10 UT for observers spanning a path from Florida to Oregon. The magnitude drop will, however, be very slight, as the star is actually 3 full magnitudes fainter than the asteroid itself. Dave Gee caught a fine occultation of a 7.4 magnitude star in the constellation Corvus by 324 Bamberga in 2007.
There’s also something special about this time of year and the region that 324 Bamberga is crossing. More visual discoveries of asteroids have been historically made in the month of September than any other calendar month. In fact, 344 of the first 1,940 numbered asteroids were found in September, more than twice the average. Palisa’s own track record bears this out, though 324 Bamberga was discovered in February.
One of the primary reasons for a September surge in discoveries is viewing direction. Astronomers of yore typically hunted for asteroids approaching opposition in the anti-sunward direction, which in September lies in the relatively star poor fields of Pisces. In December and June —the months with the lowest numbers of visual discoveries at only 75 and 65 for the “first 1,940” respectively —the anti-sunward point lies in the star-rich regions of Sagittarius and Gemini. And by the way, the meteor that exploded over the city of Chelyabinsk on February 15th was sneaking up on the Earth from the sunward direction.
Be sure to catch a glimpse of this unique asteroid through either binoculars or a telescope over the coming weeks. The next chance to observe 324 Bamberga won’t roll around again until September 2035… it’ll be great to compare notes of the 2013 apparition on that far off date!
