Exotic sediments found beneath the floor of Lake Cuitzeo in central Mexico support theories of a major cosmic impact event 12,900 years ago, report a 16-member international research team. The impact may have caused widespread environmental changes and contributed to the extinctions of many large animal species.
The team found a 13,000-year-old layer of sediment that contains materials associated with impact events, such as soot, impact spherules and atomic-scale structures known as nanodiamonds. The nanodiamonds found at Lake Cuitzeo are of a variety known as lonsdaleite, even harder than “regular” diamond and only found naturally as the result of impact events.
The thin layer of sediment below Cuitzeo corresponds to layers of similar age found throughout North America, Greenland and Western Europe.
It’s thought that a large several-hundred-meter-wide asteroid or comet entered Earth’s atmosphere at a shallow angle 12,900 years ago, melting rocks, burning biomass and, in general, causing widespread chaos and destruction. This hypothesized event would have occurred just before a period of unusually cold climate known as the Younger Dryas.
The Younger Dryas has been associated with the extinction of large North American animals such as mammoths, saber-tooth cats and dire wolves.
“The timing of the impact event coincided with the most extraordinary biotic and environmental changes over Mexico and Central America during the last approximately 20,000 years, as recorded by others in several regional lake deposits,” said James Kennett, professor of earth science at UC Santa Barbara and member of the research team. “These changes were large, abrupt, and unprecedented, and had been recorded and identified by earlier investigators as a ‘time of crisis.’ ”
The exotic materials found in the sediment beneath Cuitzeo could not have been created by any volcanic, terrestrial or man-made process. “These materials form only through cosmic impact,” Kennett said.
The only other widespread sedimentary layer ever found to contain such an abundance of nanodiamonds and soot is found at the K-T boundary, 65 million years ago. This, of course, corresponds to the impact event that led to the extinction of the dinosaurs.
The researchers’ findings appeared March 5 in the Proceedings of the National Academy of Sciences. Read the news release from UC Santa Barbara here.
“Friday, February 10th 2012 just felt like the perfect night for a comet to be discovered by an amateur astronomer,” writes Fred Bruenjes on his astronomy blog. And, this past Friday night, that’s exactly what Fred did.
Here’s how he did it:
Using custom-written software to operate a 14″ Meade LX200GPS telescope in his self-built observatory in Warrensburg, Missouri, Fred set his system up to capture images of the sky on that cold evening, not allowing himself to be chased inside by the low temperatures or the bright, rising moon. After some technical difficulties with his dSLR, Fred managed to acquire some quality images. While making a cursory look through the blink data, Fred was surprised to spot a faint burry object visible moving across three frames. A check of online databases of known objects brought up no positive hits — this was something that hadn’t been seen before.
Fred describes the “eureka” moment on his blog:
A check of known objects in the region had a lot of results in the area, but all were moving eastward while my fuzzy was moving westward. Rocks don’t make U-turns. This was really getting exciting. I had Jen, my better half, an accomplished astro imager, take a look at the images and before I could point out the faint smudge she exclaimed “That’s a comet!”
Still, Fred notes, “it wasn’t a slam-dunk.” The images were faint and there could have been other causes of blurry spots in digital images. But a check of the raw color data revealed a greenish coloration to the object’s glow, which is indicative of cyanogen and carbon emission — typical hallmarks of comets. “Very encouraging,” Fred added.
Another night’s observation was needed. If it was a comet, it would appear again along its expected trajectory. Of course, with an unidentified comet there would be no known orbit, so Fred had to manually extrapolate its position. When he trained his telescope onto his calculated coordinates the following evening and began taking images, there it was… the same faint, fuzzy green blur from the previous night, slowly appearing in the darkening sky right where it should be.
“Oh. Wow. It was dead nuts at where it was supposed to be,” Fred writes. “Wow. This thing is for real! It’s at about this time that it begins to sink in that a lifelong quest has just been fulfilled. I just crossed another thing off the bucket list!”
Fred spent the next hour gathering images to send in to the IAU’s Minor Planet Center, in the hopes of having the object cataloged so that others could locate and observe it. He didn’t have to wait long; within five minutes the object was listed on the Near-Earth Object Confirmation Page, and dubbed C/2012 C2 (Bruenjes), in honor of its discoverer.
Now that’s just got to feel good.
Comet Bruenjes is an NEO currently about 0.555 AU away from Earth. Its exact size and orbital period isn’t known, and it may even be a returning comet or piece from a larger one… the official report isn’t out yet. It appears to have a fairly inclined orbit relative to the ecliptic, based on the current diagram created by JPL’s Small-Body Database.
The comet’s total magnitude is 16.6, so it is dim and not visible to the naked eye. Fred told Universe Today in an email: “it’s in the constellation Aries, about six degrees north of Jupiter. Just after sunset in the Northern hemisphere it’s high in the southwest, nearly overhead.”
Stay tuned for more updated information on this newly-discovered member of our solar system. And congratulations to Fred Bruenjes, comet-hunter extraordinaire!
Yes, it’s coming. Yes, it’s big. Yes, it will be even closer than the Moon. And yes… we’re completely safe.
The 400-meter-wide asteroid 2005 YU55 is currently zipping through the inner Solar System at over 13 km (8 miles) a second. On Tuesday, November 8, at 6:28 p.m. EST, it will pass Earth, coming within 325,000 km (202,000 miles). This is indeed within the Moon’s orbit (although YU55’s trajectory puts it a bit above the exact plane of the Earth-Moon alignment.) Still, it is the closest pass by such a large object since 1976… yet, NASA scientists aren’t concerned. Why?
Because its orbit has been well studied, there’s nothing in its way, and frankly there’s simply nothing it will do to affect Earth.
2005 YU55’s miniscule gravity will not cause earthquakes. It has no magnetic field. It will not strike another object, or the Moon, or the Earth. It will not come into contact with cometary debris, Elenin, a black dwarf, Planet X, or Nibiru. (Not that those last three even exist.) No, YU55 will do exactly what it’s doing right now: passing through the Solar System. It will come, it will go, and hopefully NASA scientists – as well as many amateur astronomers worldwide – will have a chance to get a good look at it as it passes.
Scientists with NASA’s Near-Earth Objects Observation Program will begin tracking YU55 on Friday, November 4 using the 70-meter radar telescope at the Deep Space Network in Goldstone, California , as well as with the Arecibo Planetary Radar Facility in Puerto Rico beginning November 8. These facilities will continue to track it until the 10th.
This close pass will offer a great opportunity to get detailed radar imaging of YU55, an ancient C-type asteroid literally darker than coal. Since these objects can be difficult to observe using visible light, radar mapping can better reveal details about their surface and composition.
To help inform the public about YU55 NASA’s Jet Propulsion Laboratory in Pasadena recently hosted a live Q&A session on Ustream featuring specialists Marina Brozovic, a Goldstone Radar Team scientist, and Don Yeomans, manager of NASA’s Near-Earth Object Program. They fielded questions sent in via chat and Twitter… a recording of the event in its entirety can be seen below:
Undoubtedly there will still be those who continue to spread misinformation about 2005 YU55. After all, they did the same with the now-disintegrated comet Elenin. But the truth is out there… and the truth is that there’s no danger, no cover-ups, no “plots”, and simply no cause for concern.
UPDATE: JPL has released a brief video about YU55 featuring research scientist Lance Benner, who specializes in radar imaging of near-Earth objects:
Although classified as a potentially hazardous object, 2005 YU55 poses no threat of an Earth collision over at least the next 100 years. However, this will be the closest approach to date by an object this large that we know about in advance and an event of this type will not happen again until 2028 when asteroid (153814) 2001 WN5 will pass to within 0.6 lunar distances. – Near-Earth Object Program, JPL
Based on an observation posted on the Near Earth Object confirmation page from an image taken by A. D. Grauer using the mount Lemmon observatory, Faulkes telescope team members Nick Howes, Giovanni Sostero and Ernesto Guido along with University of Glamorgan student Antos Kasprzyk and amateur astronomer Iain Melville, imaged what is potentially some of the first direct evidence for a Trojan Jupiter Comet
Comet P/2010 TO20 (LINEAR-GRAUER) was immediately recognised by the team from looking at the orbit to be a highly unusual object, but it was only when the images came through from the faulkes observations that the true nature of the object became clear
The observations showed a distinct cometary appearance, with a sharp central condensation, compact coma and a wide, fan-shaped tail.
This is no ordinary comet, and supports the theory and initial spectral observation work by a team using the keck telescope in Hawaii. Closer analysis of their object (part of a binary known as the Patroclus pair) showed that it was made of water ice and a thin layer of dust, but at the time of writing, no direct images of a Jupiter Trojan showing evidence of a coma and tail had been taken.
The Faulkes teams above image, combined with the original observations by Grauer clearly show a cometary object, thus confirming the Keck team’s hypothesis.
According to the CBET released today “After two nights of observations of Grauer’s comet had been received at the Minor Planet Center.
Spahr realized that this object was identical with an object discovered a year ago by the LINEAR project (discovery observation tabulated below; cf. MPS 351583) that appeared to be a Jupiter Trojan minor planet.”
The observations have now proved it is not a minor planet, but a comet.
This discovery could provide new clues about the evolution of the Solar System, suggesting that the Gas Giants formed closer to the Sun and as they moved further away, they caused massive perturbations with Kuiper Belt objects, trapping some in their own orbits.
Nick Howes on the Faulkes team said “When we first saw the preliminary orbit, we knew it was a quite remarkable object” Howes also added “To have a University Student also involved is terrific for the degree program at Glamorgan and also for the Faulkes project. We’d like to extend our congratulations to Al Grauer” for his detection of this groundbreaking new comet” and we’re immensely proud to be part of the CBET released by the IAU confirming its nature
Comet Elenin, the supposed “doomsday comet” that has inspired so much confusion and controversy since its discovery in December 2010, may have broken apart completely during its recent pass around the Sun.
Discoverer Leonid Elenin posted the image above earlier today on his website, SpaceObs.org. Taken with the International Scientific Optical Network’s 18″ telescope in New Mexico (ISON-NM), it shows what may be the remnants of Elenin, a faint cloud barely visible after its exit from behind the Sun.
“On the left you can see possible position of this ‘cloud’,” Leonid writes. “Brightness of this object does not exceed 18m, which means what now, magnitude of the comet is lower then predicted on 12m. Hopefully in the near future debris of the comet will be observed on a large telescopes, and perhaps we’ll see some details of this ‘cloud’.”
Ground-based viewing of Elenin’s remains may be hampered over the next few days by the full Moon, he adds.
Although many rumors have been spread about the catastrophic danger Elenin poses to humans, in reality the comet was never a threat. Not expected to come any closer than 22 million miles (35 million km) to Earth, it’s been previously speculated that Elenin would most likely disintegrate during its current orbit.
“I don’t know why fearmongers [chose] my comet,” Leonid Elenin told Universe Today. “I received many letters from scared people. But if they believe in conspiracy theories I can’t help them.”
Hopefully this helps put some of the doomsday nonsense to rest!
It starts out innocently enough: a small speck against a field of background stars, barely noticeable in the image data. But… it’s a speck that wasn’t there before. Subsequent images confirm its existence – there’s something out there. Something bright, something large, and it’s moving through our solar system very quickly. The faint blur indicates that it’s a comet, an icy visitor from the outermost reaches of the solar system. And it’s headed straight toward Earth.
Exhaustive calculations are run and re-run. Computer simulations are executed. All possibilities are taken into consideration, and yet there’s no alternative to be found; our world will face a close encounter with a comet in mere months’ time. Phone calls are made, a flurry of electronic messages fly between computer terminals across the world, consultations are held with top experts in the field. We are unprepared… what can we do? What does this mean for civilization as we know it? What will this speeding icy bullet from outer space do to our planet?
The answer? Nothing.
Nothing at all. In fact, it probably won’t even be very interesting to look at – if you can even find it when it passes by.
(Sorry for the let-down.)
There’s been a lot of buzz in the past several months regarding Comet Elenin, a.k.a. C/2010 X1, which was discovered by Russian astronomer Leonid Elenin on December 10, 2010. Elenin spotted the comet using a telescope in New Mexico remotely from his location in Lyubertsy, Russia. At that time it was about 647 million kilometers (401 million miles) from Earth… in the time since it has closed the distance considerably, and is now around 270 million km away. Elenin is a long-period comet, which means it has a rather large orbit around the Sun… it comes in from a vast distance, swings around the Sun and heads back out to the depths of the solar system – a round trip lasting over 10,000 years. During its current trip it will pass by Earth on October 16, coming as close as 35 million km (22 million miles).
Yes, 22 million miles.
That’s pretty far.
Way too far for us to be affected by anything a comet has to offer. Especially a not-particularly-large comet like Elenin.
Some of the doomy-gloomy internet sites have been mentioning the size of Elenin as being 80,000 km across. This is a scary, exaggerated number that may be referring to the size of Elenin’s coma – a hazy cloud of icy particles that surrounds a much, much smaller nucleus. The coma can be extensive but is insubstantial; it’s akin to icy cigarette smoke. Less than that, in fact… a comet’s coma and tail are even more of a vacuum than can be reproduced in a lab on Earth! In reality most comets have a nucleus smaller than 10km…that’s less than a billionth the mass of Earth (and a far cry from 80,000 km.) We have no reason to think that Elenin is any larger than this – it’s most likely smaller.
Ok, but how about the gravitational and/or magnetic effect of a comet passing by Earth? That’s surely got to do something, right? To Earth’s crust, or the tides? For the answer to that, I will refer to Don Yeomans, a researcher at NASA’s Near-Earth Object Program Office at JPL:
“Comet Elenin will not only be far away, it is also on the small side for comets. And comets are not the most densely-packed objects out there. They usually have the density of something akin to loosely packed icy dirt,” said Yeomans. “So you’ve got a modest-sized icy dirtball that is getting no closer than 35 million kilometers. It will have an immeasurably miniscule influence on our planet. By comparison, my subcompact automobile exerts a greater influence on the ocean’s tides than comet Elenin ever will.”
“It will have an immeasurably miniscule influence on our planet. By comparison, my subcompact automobile exerts a greater influence on the ocean’s tides than comet Elenin ever will.”
– Don Yeomans, NASA / JPL
And as far as the effect from Elenin’s magnetic field goes… well, there is no effect. Elenin, like all comets, doesn’t have a magnetic field. Not much else to say there.
But the claims surrounding Elenin have gone much further toward the absurd. That it’s going to encounter another object and change course to one that will cause it to impact Earth, or that it’s not a comet at all but actually a planet – Nibiru, perhaps? – and is on a collision course with our own. Or (and I particularly like this one) that alien spaceships are trailing Elenin in such a way as to remain undetected until it’s too late and then they’ll take over Earth, stealing our water and natural resources and turning us all into slaves and/or space munchies… or however the stories go. (Of course the government and NASA and Al Gore and Al Gore’s hamster are all in cahoots and are withholding this information from the rest of us. That’s a given.) These stories are all just that – stories – and have not a shred of science to them, other than a heaping dose of science fiction.
“We live in nervous times, and conspiracy theories and predictions of disaster are more popular than ever. I like to use the word cosmophobia for this growing fear of astronomical objects and phenomena, which periodically runs amuck on the Internet. Ironically, in pre-scientific times, comets were often thought to be harbingers of disaster, mostly because they seemed to arrive unpredictably – unlike the movements of the planets and stars, which could be tracked on a daily and yearly basis.”
– David Morrison, planetary astronomer and senior scientist at NASA’s Ames Research Center
The bottom line is this: Comet C/2010 X1 Elenin is coming, and it will pass by Earth at an extremely safe distance – 100 times the distance from Earth to the Moon. It will not be changing direction between now and then, it will not exert any gravitational effect on Earth, its magnetic field is nonexistent and there are no Star Destroyers cruising in its wake. The biggest effect it will have on Earth is what we are able to learn about it as it passes – after all, it is a visitor from the far reaches of our solar system and we won’t be seeing it again for a very, very long time.
I’m sure we’ll have found something else to be worried about long before then.
“This intrepid little traveler will offer astronomers a chance to study a relatively young comet that came here from well beyond our solar system’s planetary region. After a short while, it will be headed back out again, and we will not see or hear from Elenin for thousands of years. That’s pretty cool.”
Ah, Pluto. Seems every time we think we’ve got it figured out, it has a new surprise to throw at us.
First spotted in 1930 by a young Clyde Tombaugh, for 76 years it enjoyed a comfortable position as the solar system’s most distant planet. Then a controversial decision in 2006 by the International Astronomical Union, spurred by suggestions from astronomer (and self-confessed “planet-killer”) Mike Brown*, relegated Pluto to a new class of worlds called “dwarf planets”. Not quite planets and not quite asteroids, dwarf planets cannot entirely clear their orbital path with their own gravitational force and thus miss out on full planetary status. Besides immediately making a lot of science textbooks obsolete and rendering the handy mnemonic “My Very Eager Mother Just Served Us Nine Pies” irrelevant (or at least confusing), the decision angered many people around the world, both in and out of the scientific community. Pluto is a planet, they said, it always has been and always will be! Save Pluto! the schoolkids wrote in crayon to planetarium directors. The world all of a sudden realized how much people liked having Pluto as the “last” planet, and didn’t want to see it demoted by decision, especially a highly contested one.
Yet as it turns out, Pluto really may not be a planet after all.
It may be a comet.
But…that’s getting ahead of ourselves. First things first.
Recent discoveries by a UK team of astronomers points to the presence of carbon monoxide in Pluto’s atmosphere. Yes, Pluto has an atmosphere; astronomers have known about it since 1988. At first assumed to be about 100km thick, it was later estimated to extend out about 1500km and be composed of methane gas and nitrogen. This gas would expand from the planet’s – er, dwarf planet’s – surface as it came closer to the Sun during the course of its eccentric 248-year orbit and then freeze back onto the surface as it moved further away. The new findings from the University of St Andrews team, made by observations with the James Clerk Maxwell telescope in Hawaii, identify an even thicker atmosphere containing carbon monoxide that extends over 3000 km, reaching nearly halfway to Pluto’s largest moon, Charon.
It’s possible that this carbon monoxide atmosphere may have expanded outwards from Pluto, especially in the years since 1989 when it made the closest approach to the Sun in its orbit. Surface heating (and the term “heating” is used scientifically here…remember, at around -240ºC (-400ºF) Pluto would seem anything but balmy to us!) by the Sun’s radiation would have warmed the surface and expelled these gases outwards. This also coincides with observations made by the Hubble Space Telescope over the course of four years, which revealed varying patterns of dark and light areas on Pluto’s surface – possibly caused by the thawing of frozen areas that shift and reveal lighter surface material below.
“Seeing such an example of extra-terrestrial climate-change is fascinating. This cold simple atmosphere that is strongly driven by the heat from the Sun could give us important clues to how some of the basic physics works, and act as a contrasting test-bed to help us better understand the Earth’s atmosphere.”
– Dr. Jane Greaves, Team Leader
In fact, carbon monoxide may be the key to why Pluto even still has an atmosphere. Unlike methane, which is a greenhouse gas, carbon monoxide acts as a coolant; it may be keeping Pluto’s fragile atmosphere from heating up too much and escaping into space entirely! Over the decades and centuries that it takes for Pluto to complete a single year, the balance between these two gases must be extremely precise.
So here we have Pluto exhibiting an expanding atmosphere of thawing expelled gas as it gets closer to the Sun in an elliptical, eccentric orbit. (Sound familiar?) And now there’s another unusual, un-planet-like feature that’s being put on the table: Pluto may have a tail.
Actually this is an elaboration of the research results coming from the same team at the University of St Andrews. The additional element here is a tiny redshift detected in the carbon monoxide signature, indicating that it is moving away from us in an unusual way. It’s possible that this could be caused by the top layers of Pluto’s atmosphere – where the carbon monoxide resides – being blown back by the solar wind into, literally, a tail.
That sounds an awful lot, to this particular astronomy reporter anyway, like a comet.
Anyway, regardless of what Pluto is or isn’t, will be called or used to be called, there’s no denying that it is a fascinating little world that deserves our attention. (And it will be getting plenty of that come July 2015 when the New Horizons spacecraft swings by for a visit!) I’m sure there’s no one here who would argue that fact.
New Horizons’ upcoming visit will surely answer many questions about Pluto – whatever it is – and most likely raise even more.
The new discovery was presented by team leader Dr. Jane Greaves on Wednesday, April 20 at the National Astronomy Meeting in Wales.
[/caption]What are comets made of? Good question! Comet nuclei are loose collections of ice, dust and small rocky particles, ranging from a few kilometers to tens of kilometers across. As a comet approaches the inner solar system, solar radiation causes the volatile materials within the comet to vaporize and stream out of the nucleus, carrying dust away with them. The streams of dust and gas form a huge, extremely tenuous atmosphere around the comet called the coma, and the force exerted on the coma by the radiation pressure of the Sun and solar wind cause a tail to form. The tail always points away from the sun.
In order to understand what are comets made of, we need to break down the three main parts of the comet: the nucleus, coma, and tail. Comet nuclei are known to range from about 100 meters to more than 40 kilometers across. They are composed of rock, dust, ice and frozen gases such as carbon monoxide, carbon dioxide, methane, and ammonia. Sometimes called dirty snowballs, recent studies have shown that the ice of a comet is covered by a crust. Comets also contain a variety of organic compounds as well as the gases already mentioned. Some of these are methanol, hydrogen cyanide, formaldehyde, ethanol, and ethane. More complex molecules such as long-chain hydrocarbons and amino acids may also be in comets. Because of their low mass, comets cannot become spherical under their own gravity, and will thus have irregular shapes.
The coma is the the nebulous envelope around the nucleus of a comet. It is formed when the comet passes close to the Sun on a highly elliptical orbit. As the comet warms, parts of it turn from solid to gas(sublimate). Larger charged dust particles are left along the comet’s orbital path while smaller charged particles are pushed away from the Sun into the comet’s tail by solar wind. This helps astronomers distinguish comets from stars because it creates a fuzzy appearance.
The tail is illuminated by the Sun and may become visible from Earth when a comet passes through the inner solar system, the dust reflecting sunlight directly and the gases glowing from ionization. The streams of dust and gas each form their own distinct tail, pointing in slightly different directions. The tail of dust is left behind in the comet’s orbit in such a manner that it often forms a curved tail called the antitail. At the same time, the ion tail, made of gases, always points directly away from the Sun, as this gas is more strongly affected by the solar wind than is dust, following magnetic field lines rather than an orbital trajectory. Paralax viewing from the Earth may sometimes mean the tails appear to point in opposite direction.
NASA scientists studying the comet samples returned by the Stardust spacecraft have discovered glycine, a fundamental building block of life. Stardust captured the samples from comet Wild 2 in 2004 and returned them to Earth in 2006. “Glycine is an amino acid used by living organisms to make proteins, and this is the first time an amino acid has been found in a comet,” said Dr. Jamie Elsila of NASA’s Goddard Space Flight Center. “Our discovery supports the theory that some of life’s ingredients formed in space and were delivered to Earth long ago by meteorite and comet impacts.”
Proteins are a major component of all living cells, and amino acids are the building blocks of protein. Just as the 26 letters of the alphabet are arranged in limitless combinations to make words, life uses 20 different amino acids in a huge variety of arrangements to build millions of different proteins.
As Stardust passed through dense gas and dust surrounding the icy nucleus of Wild 2 (pronounced “Vilt-2”), special collection grids filled with aerogel – a novel sponge-like material that’s more than 99 percent empty space – gently captured samples of the comet’s gas and dust. The grid was stowed in a capsule which detached from the spacecraft and parachuted to Earth on January 15, 2006. Since then, scientists around the world have been busy analyzing the samples to learn the secrets of comet formation and our solar system’s history.
Earlier, preliminary analysis in the Goddard labs detected glycine in both aluminum foil that lined the collection grids, as well as in a sample of the aerogel. However, since glycine is used by terrestrial life, at first the team was unable to rule out contamination from sources on Earth. “It was possible that the glycine we found originated from handling or manufacture of the Stardust spacecraft itself. We spent two years testing and developing our equipment to make it accurate and sensitive enough to analyze such incredibly tiny samples,” said Elsila. The new research used isotopic analysis of the foil to rule out that possibility.
Isotopes are versions of an element with different weights or masses; for example, the most common carbon atom, Carbon 12, has six protons and six neutrons in its center (nucleus). However, the Carbon 13 isotope is heavier because it has an extra neutron in its nucleus. A glycine molecule from space will tend to have more of the heavier Carbon 13 atoms in it than glycine that’s from Earth. That is what the team found. “We discovered that the Stardust-returned glycine has an extraterrestrial carbon isotope signature, indicating that it originated on the comet,” said Elsila.
Another team member Dr. Daniel Glavin said, “Based on the foil and aerogel results it is highly probable that the entire comet-exposed side of the Stardust sample collection grid is coated with glycine that formed in space.”
The team’s research will be published in the journal Meteoritics and Planetary Science.
Back in 1996, astronomers discovered a strange object in the asteroid belt. They decided it was either a “lost” comet or an icy asteroid, as it ejected dust like a comet but had an orbit like an asteroid. No one had ever seen anything like the object, called 133P. Ever since it was found, astronomers have wondered if it was just an oddity — one of a kind. We now know it is not, and the discovery of more of these half asteroids/half comets means there is a new class of objects in our solar system.
One of these new objecst, 176P/LINEAR is also emitting dust as it orbits in the asteroid belt. It was found by Henry Hsieh at Queen’s University, Belfast in Northern Ireland. Hsieh has been working to figure out the unusual behavior of 133P. He hypothesized that either one of two things could explain the existence of the comet-asteroid: “(1.) 133P is a classical comet from the outer solar system that has evolved onto a main-belt orbit, or (2.) 133P is a dynamically ordinary main-belt asteroid on which subsurface ice has recently been exposed,” Hsieh wrote in his paper. “If (1) is correct, the expected rarity of a dynamical transition onto an asteroidal orbit implies that 133P could be alone in the main belt. In contrast, if (2) is correct, other icy main-belt objects should exist and could also exhibit cometary activity.”
Hsieh thought it was unlikely a comet could have been kicked around enough to end up in orbit in the asteroid belt, so he followed the assumption that 133P was a dynamically ordinary, yet icy main-belt asteroid. He set out to prove the hypothesis that 133P-like objects should be common and could be found by an well-designed observational survey.
Hsieh made 657 observations of 599 asteroids in the asteroid belt and found 176P/LINEAR. He also determined the asteroid is partially made of ice, which is being ejected following a collision with another object, thus the comet-like attributes.
Additionally, since there is evidence for past and even present water in main-belt asteroids, Hsieh says statistically there should be around 100 currently active Main Belt Comets (MBCs) as these objects are called, among the kilometer-scale, low-inclination, outer belt asteroid population.
The Technology Review blog offered suggestions for what to name these new objects that are half comet and half asteroid: “Comsteroids? Asteromets? Hsiehroids?”