Star System Surrounded by Destruction

A nearby star system is currently going through hell, as hinted at by NASA's Spitzer Space Telescope. Through its infrared eye, Spitzer has detected the dusty remains of comet impacts around the star Eta Corvi -- reminding us what it must have been like during the early evolution of our own solar system.

During our solar system's "Late Heavy Bombardment" (LHB) some four billion years ago, the inner planets were constantly peppered with massive comets impacting their surfaces. Earth would have been unrecognizable -- the planet's surface was a burning, molten mess; young atmosphere constantly punctuated by incoming cometary fragments.

Devoid of any eroding atmosphere, the moon's surface bears the scars of this epic cometary onslaught -- huge impact craters providing a reminder of how violent the "early years" of our solar system really was.

Despite the continuous cycle of cataclysmic impact events generating a hellish cauldron on Earth, the LHB has been linked with the genesis of life -- evidence points to a cometary source for the organic ingredients. Needless to say, the growing pains inflicted by the LHB on our planet is of huge importance to scientists.

Therefore, to spot the signs of similar cometary bombardments in other star systems would be pretty awesome. Not only would that help us understand the evolution of planetary systems orbiting other stars, it would provide a "time capsule" for us to have a glimpse of the early life of our own solar system. Of course, it would also give us an idea of how many other stars could be "ripe" for life (as we know it).

Now, scientists using observations by Spitzer have detected cometary Armageddon around Eta Corvi, a star some 50 light-years away in the constellation Corvus. 

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A ring of warm dust closely surrounds Eta Corvi, and after analysis of the dust, it appears to have the same chemistry as pulverized comets -- water ice, rock and organics. This provides the hint that the star may be going through a similar phase as the early solar system -- comets are careening inward, colliding with as-yet to be detected planetary bodies.

The star is approximately a billion years old, an age that scientists estimate is "just right" for a cometary hailstorm to occur.

"We believe we have direct evidence for an ongoing Late Heavy Bombardment in the nearby star system Eta Corvi, occurring about the same time as in our solar system," said Carey Lisse, senior research scientist at the Johns Hopkins University Applied Physics Laboratory in Laurel, Md. 

Not only does the chemical fingerprint of the debris surrounding Eta Corvi demonstrate active impacts from a huge reservoir of comets, the dust's chemistry resembles that of the Almahata Sitta meteorite, fragments of which fell to Earth in Sudan in 2008. This suggests ancient material floating around in the solar system may have a common formation process as the material getting bashed up in Eta Corvi.

The similarities don't end there. There is evidence of another, cooler dusty ring further away from the star than the cometary impact debris, approximately 150 AU (150 times the Earth-sun distance) from Eta Corvi. The ring was detected in 2005 and could be the location of cometary nuclei, asteroids and other debris. The solar system has a region at roughly the same distance -- the Kuiper Belt.

Could this outer, cool ring be the source of the comets currently smashing through the inner Eta Corvi system? Possibly.

This is a fascinating study as Spitzer has gleaned an insight to the nature of a star system, possibly containing several planetary bodies -- after all, it was the migration of Jupiter and Saturn in the early history of the solar system that kick-started the LHB in the first place. Perhaps Eta Corvi is currently undergoing a similar process.

"We think the Eta Corvi system should be studied in detail to learn more about the rain of impacting comets and other objects that may have started life on our own planet," said Lisse.

These findings have been accepted for publication in The Astrophysical Journal and were presented at the Signposts of Planets meeting at NASA's Goddard Space Flight Center in Greenbelt, Md.
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Posted in: asteroids,comet,cometary,Eta Corvi,nasa,solar system,space,star system,Star System Surrounded by Destruction

First Comet Found with Ocean-Like Water

New evidence supports the theory that comets delivered a significant portion of Earth's oceans, which scientists believe formed about 8 million years after the planet itself.

Astronomers have found a new cosmic source for the same kind of water that appeared on Earth billions of years ago and created the oceans. The findings may help explain how Earth's surface ended up covered in water. 

New measurements from the Herschel Space Observatory show that comet Hartley 2, which comes from the distant Kuiper Belt, contains water with the same chemical signature as Earth's oceans. This remote region of the solar system, some 30 to 50 times as far away as the distance between Earth and the sun, is home to icy, rocky bodies including Pluto, other dwarf planets and innumerable comets. 

"Our results with Herschel suggest that comets could have played a major role in bringing vast amounts of water to an early Earth," said Dariusz Lis, senior research associate in physics at the California Institute of Technology in Pasadena and co-author of a new paper in the journal Nature, published online today, Oct. 5. "This finding substantially expands the reservoir of Earth ocean-like water in the solar system to now include icy bodies originating in the Kuiper Belt."

Scientists theorize Earth started out hot and dry, so that water critical for life must have been delivered millions of years later by asteroid and comet impacts. Until now, none of the comets previously studied contained water like Earth's. However, Herschel's observations of Hartley 2, the first in-depth look at water in a comet from the Kuiper Belt, paint a different picture. 

This illustration shows the locations of various classes of comets in the Solar System, relative to the orbits of the planets. The left panel shows the inner Solar System along with the orbit of Jupiter-Family comet Hartley 2. The central panel shows a larger portion of the Solar System beyond the orbit of Jupiter, as well as the Kuiper Belt, one of the two main reservoirs of comets in the solar system. The right panel shows the Oort Cloud, the other main reservoir of comets located well beyond the outer solar system. Credit: ESA/AOES Medialab 

Herschel peered into the comet's coma, or thin, gaseous atmosphere. The coma develops as frozen materials inside a comet vaporize while on approach to the sun. This glowing envelope surrounds the comet's "icy dirtball"-like core and streams behind the object in a characteristic tail. Herschel detected the signature of vaporized water in this coma and, to the surprise of the scientists, Hartley 2 possessed half as much "heavy water" as other comets analyzed to date. In heavy water, one of the two normal hydrogen atoms has been replaced by the heavy hydrogen isotope known as deuterium. The ratio between heavy water and light, or regular, water in Hartley 2 is the same as the water on Earth's surface. The amount of heavy water in a comet is related to the environment where the comet formed.

By tracking the path of Hartley 2 as it swoops into Earth's neighborhood in the inner solar system every six-and-a-`half years, astronomers know that it comes from the Kuiper Belt. The five comets besides Hartley 2 whose heavy-water-to-regular-water ratios have been obtained all come from an even more distant region in the solar system called the Oort Cloud. This swarm of bodies, 10,000 times farther afield than the Kuiper Belt, is the wellspring for most documented comets.  

Using the Herschel Space Observatory, astronomers have discovered that comet Hartley 2 possesses a ratio of "heavy water" to light, or normal, water that matches what's found in Earth's oceans. Image credit: NASA/JPL-Caltech

Given the higher ratios of heavy water seen in Oort Cloud comets compared to Earth's oceans, astronomers had concluded that the contribution by comets to Earth's total water volume stood at approximately 10 percent. Asteroids, which are found mostly in a band between Mars and Jupiter but occasionally stray into Earth's vicinity, looked like the major depositors. The new results, however, point to Kuiper Belt comets having performed a previously underappreciated service in bearing water to Earth. 

How these objects ever came to possess the telltale oceanic water is puzzling. Astronomers had expected Kuiper Belt comets to have even more heavy water than Oort Cloud comets because the latter are thought to have formed closer to the sun than those in the Kuiper Belt. Therefore, Oort Cloud bodies should have had less frozen heavy water locked in them prior to their ejection to the fringes as the solar system evolved.

"Our study indicates that our understanding of the distribution of the lightest elements and their isotopes, as well as the dynamics of the early solar system, is incomplete," said co-author Geoffrey Blake, professor of planetary science and chemistry at Caltech. "In the early solar system, comets and asteroids must have been moving all over the place, and it appears that some of them crash-landed on our planet and made our oceans."

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Posted in: comet,ocean,Oort cloud,space,sun

Draconid Meteors 8 oct. 2011

For the next few nights, Draco the Dragon will be spitting out “shooting stars,” also known as meteors. The Draconid shower is predicted to produce the greatest number of meteors on the night of October 8, 2011. Watch for them starting at nightfall. Unfortunately, the waxing gibbous moon will wipe many of these meteors from view, and oftentimes the hard-to-predict shower doesn’t offer much more than a handful of languid meteors per hour.

However, this shower produced major displays in 1933 and 1946 – with thousands of meteors per hour seen in those years – but since then has been so spotty that the tried-and-true Observer’s Handbook – source of so much wonderful sky info – lists a “?” for the rate of meteors expected at the peak of the Draconids. This year, however, some astronomers are calling for a Draconid meteor shower to burst into storm in 2011, with rates of 1,000 meteors per hour.

The forecast calls for the peak to occur between 17:00 and 18:00 Universal Time on October 8, 2001. If the prediction holds true, that means Europe, northern Africa and the Middle East will get to watch the Draconids at their peak. But keep in mind that meteor showers are notorious for defying predictions, either surpassing or falling shy of expectation, so you never know for sure. Even if the storm materializes, the bright moon will undoubtedy wash away many of these meteors. 

If you live at middle and far northern latitudes, though, it’s well worth a try. Unlike many major showers, the radiant for the Draconids is highest up at nightfall, so watch for these meteors as soon as darkness falls. 

Most meteor showers are named for the constellation from which the meteors radiate on the sky dome. The Draconids, however, are sometimes also called the Giacobinids, to honor the man who first sighted the comet that spawned this meteor shower. 

Michel Giacobini discovered this comet on December 20, 1900. Another sighting in 1913 added Zinner to the name of the comet, 21P Giacobini-Zinner. It is a periodic comet, which returns every 6 years and 4 months. Tracking this comet, and noting this October meteor shower, helped astronomers figure out how to predict meteor showers in 1915. The great Draconid/Giacobinid meteor storms occurred in 1933 and 1946. The comet returned in 1998 as well, and the Draconids picked up that year, but only to a rate of about 100 per hour.

Coming up in our lifetimes, in the year 2013 – approximately two years after the comet approaches perihelion (closest approach to the sun) – there might be another meteor storm around the time of this shower’s peak. Or there might not be.

There might be a meteor storm this year, in 2011. Perhaps the rates could go up to hundreds of meteors per hour in North America. Or we might see only a handful of meteors per hour. Under normal conditions, when astronomers speak of a meteor shower peaking, it is similar to a weather forecaster saying, “The heaviest rain/snow is predicted for such-and-such hour.” In other words, the prediction might not be precise, since nature is always unpredictable to a degree. But the rate of the meteors is higher during the peak of a meteor shower than on any other night.

For a taste of history related to this shower, go to the Astronomy Abstract Service from the Smithsonian and NASA and find a 1934 article called “The Meteors from Giacobini’s Comet” by C.C. Wylie. It is an account of the famed meteor storm of 1933.

If you want to try your luck, lie down on a reclining chair with your feet pointing northward. Find as much open sky as possible. How many Draconid meteors will be seen in the moonlit skies these next few evenings?

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Posted in: comet,draconid meteors,draconides,europe,meteor shower,shooting stars,space

Comets Elenin & Garradd Now In Night Sky

Skywatchers often ask "When's the next comet?" In fact, if you’re prepared to do a bit of searching, there are always several comets visible in the night sky, including two right now.

Some comets are like old friends, they keep coming back at regular intervals to visit. These are called periodic comets; Comet Halley was the first such comet to be identified, by Edmond Halley back in 1705. It returns to the inner solar system every 75 to 76 years; its last appearance was in 1986 and its next will be in 2061. At present Halley is out just beyond Neptune;s orbit.

Other comets are one-time visitors: they come in to visit us from the Oort Cloud, warm themselves for a few months by the sun, and then head back out to the farthest reaches of the solar system.

There are two comets currently visiting the inner solar system — comet Elenin and comet Garradd — so the next two months will provide some excellent opportunities to observe these unusual visitors. The sky map of the two comets here shows they locations over the next few weeks.

All comets share one characteristic: they are like "dirty snowballs" in their makeup. Their nucleus of rock and ice, when warmed by the sun, sheds its ice which forms a graceful tail as it’s swept away by the solar wind. Because it’s the solar wind that drives the gas and vapor away, comet’s tails always point away from the sun.

In the sky, many comets appear like ghostly fingers pointing down towards Earth. That is one reason why comets have traditionally been viewed as harbingers of death and disaster. To astronomers, on the contrary, they are objects of great beauty and attract close scientific scrutiny for the information they reveal about the ancient history of the solar system and its farthest reaches.

Comet Elenin now showing.

The first comet visitor in the sky we'll review is comet Elenin (C2010 X1). You may have heard about, because it’s become a popular item for the gloom and doom crowd, who see portents of disaster in ordinary astronomical objects.
The truth about Comet Elenin is that it is a quite ordinary, fairly small comet discovered on Dec. 10, 2010 by Russian amateur astronomer Leonid Elenin using a remote controlled telescope in Arizona.

This comet will pass closest to the sun on Sept. 10 (45 million miles or 72 million kilometers) and closest to Earth on Oct. 16 at a distance of 22 million miles (35 million km.)
Despite the fact that this is a really tiny body, 3 or 4 km. in diameter which will miss the Earth by 22 million miles, the purveyors of gloom and doom have seized upon it as bringing disaster upon the Earth. Please don’t take them seriously, instead try to spot this interesting little object.

At present, comet Elenin is too close to the sun to be viewed from the Northern Hemisphere, though observers south of the equator may catch it low in the western sky after sunset. Northern observers' turn will come after the comet passes the sun and starts back out towards the Oort Cloud.
In the last few days of September, Elenin will separate from the sun in our morning sky. It will be visible in binoculars in the morning sky for all of October, and we will publish finder maps then.

There is an unusual opportunity to “observe” this comet when it is very close to the sun during the last week of September. To do this, you won’t be able to use your eyes or any optical aid; instead you will use your computer.
Several times every day, the SOHO satellite returns images of the sun, including ones from the observatory's LASCO C3 camera which has a field of view of about 15 degrees. This has an occulting disk which blocks the Sun itself but lets the background stars appear.

If you take a look at it right now, you'll see Venus off to the left of the sun and the star Regulus to the right. During the last week of September, you will be able to see Comet Elenin pass through the field of view.
Comet Garradd graces the sky
The other bright comet in the night sky hasn't received the publicity of comet Elenin but is actually a better opportunity for skywatchers. This is comet Garradd (C2009 P1), which was discovered on Aug. 13, 2009 by Australian astronomer G. J. Garradd.

Comet Garradd is very easy for any experienced skywatcher to locate and observe with binoculars. Currently it is just south of the small but well-known constellation of Sagitta, the arrow. This arrow-shaped constellation is right in the middle of the summer triangle formed by the bright stars Vega, Deneb, and Altair. On Wednesday (Aug. 24), Garradd was right under the tip of the arrow.

Tonight (Friday, Aug. 26), Garradd it will be impaled by the shaft of the arrow, and one week later (Friday, Sept. 2) it will be right by the "hook" of the popular Coathanger Cluster, also known as Brocchi’s Cluster. During that time it should increase in brightness slowly from about magnitude 8.2 to about magnitude 8.1, an easy object with binoculars.

The comet will continue moving westward and brightening, reaching magnitude 7.0 on Feb. 12. Astronomers measure the brightness of a night sky object using a reverse scale of magnitude. The lower the number of an object's magnitude, the brighter the object appears.
The sky map in this story shows the position of comet Garradd at 11 p.m. EDT each night from through Sept 2.

A reminder: All of the magnitudes given here for comets are estimates; comet brightness is notoriously hard to predict. The comets may be fainter than predicted or we may get lucky and get a couple of really bright comets.

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Posted in: comet,eart,elenin,garradd,sky,space

Meteors...Perseids Are Coming

The Perseid meteor shower is one of the most dazzling astronomical events of the year. The meteors originate from the dusty debris of Comet Swift-Tuttle. Sadly, the bright full moon may obscure the fainter meteors from view. 

            At a distance of around 8 billion kilometers (5 billion miles, or 54 AU -- a little beyond Pluto's orbit), an icy space rock silently hurtles toward the inner solar system steadily gaining speed. 

           This piece of space debris -- composed of primordial rock and ice -- measures no more than 26 kilometers (16 miles) in diameter, and as it plunges sunward, it will pass the orbits of Pluto, Neptune, Uranus, Saturn, Jupiter, Mars and even power through our neighborhood before being flung back into the depths of interplanetary space.

          You'd think that's all we would see of Comet Swift-Tuttle until it returns in about 133 years time, but you couldn't be more wrong. Every year we are reminded of its fleeting presence as the Earth intercepts the comet's orbit and sweeps up some of the fragments it left behind. Like a celestial vacuum cleaner, Earth collects everything in its path and treats us to one of the greatest shows the Universe has to offer: the Perseid meteor shower.

           Through the year, there are around 30 decent meteor showers and the Perseids are some of the finest meteor examples around mid-August every year.

           As the countless pieces of dust slam into our atmosphere at over 100,000 kilometers per hour (17 miles per second!), they compress the air to such a degree that the gas heats up, generating light. We see this as the characteristic shooting star effect. The smaller pieces of dust will burn up high in the atmosphere and we call them "meteors." (Larger pieces of debris that survive the fiery plunge and hit the ground are called "meteorites" -- but these are rare and it is highly unlikely any Perseid will fall into this category.)

           It's possible to see meteors any time of year, we call them "sporadic" and they are not associated with any shower. If you study the meteors from a particular shower though, you will see that they all come from one point in the sky. This point is known as the "radiant" and it's the location of the radiant that determines the name of the shower. In the case of the Perseids, the radiant lies in the constellation Perseus.

          The Earth has already started to enter the fragments -- or "meteoroids" -- from the Swift-Tuttle stream, and Perseid meteors can be seen in our skies right now. Activity is picking up so it's worth going outside over the next few nights to see how many you can spot.

          The peak of activity is predicted to be in the early hours of Saturday (Aug. 13), but unfortunately the light of the full moon will block many of the fainter meteors.

          The best time to catch the Perseids is in the early hours after midnight when you will be on the "forward" facing side of the Earth's orbit. So, wrap up warm, find a dark spot away from lights, lie back on a comfy chair and gaze skyward.

 

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Posted in: comet,earth,meteors,perseids