Posted on 06/15/2006 2:26:20 PM PDT by blam
New Trojan asteroid hints at huge Neptunian cloud
19:00 15 June 2006
NewScientist.com news service
Kelly Young
The four known Neptune Trojans are shown in their position 60 degrees ahead of Neptune. The known clusters of Trojan asteroids on either side of Jupiter are also shown (Illustration: Scott Sheppard) A newly discovered asteroid in Neptune's orbit indicates the existence of a much larger, but as-yet-unseen, cloud of rocks in that region. The asteroids in Neptune's orbit might even outnumber those in the main asteroid belt between Mars and Jupiter, the new research suggests."
The asteroid was discovered by Scott Sheppard of the Carnegie Institution of Washington, and Chadwick Trujillo of the Gemini Observatory in Hawaii, both in the US. They used Carnegie's Magellan-Baade 6.5-metre telescope in Chile and the 8.2-metre Gemini Telescope.
It is one of four known Neptunian "Trojan" asteroids, which orbit in lockstep with the planet. Two of the Trojans were discovered by Sheppard and Trujillo in 2004 and 2005.
The asteroids orbit 60°, or about 5 billion kilometres, ahead of Neptune on its circular orbit around the Sun, which is a gravitationally stable location called a Lagrange point. But the newly-found asteroid is unique in that its orbit is tilted 25° relative to the plane of the solar system.
Asteroids with such tilts are only rarely in the particular regions surveyed by the astronomers. So such a sighting means observers can make a statistical inference that there must be many more. "This finding strongly supports the idea that Neptune Trojans fill a thick disc with a population comparable to, or even larger than, that of [the 2000 known] Jupiter Trojans," says Francesco Marzari, at the University of Padova, Italy, in a commentary on the paper in the journal Science.
Trojan zone
How planets acquire their Trojans has been much discussed by researchers but the high tilt in this case favours a theory called "freeze-in" capture, which is thought to have also allowed Jupiter to acquire its asteroids.
During the evolution of the gas planets, their orbits were erratic and small bodies in the solar system moved about chaotically. But as the planets' orbits stabilised, the strength of gravitationally stable regions in front of and behind the planet's orbit grew.
"At that moment, whatever objects were at the right place at the right time – in the Trojan zone – were frozen," says Eugene Chiang, at the University of California Berkeley, who discovered the first Neptune Trojan.
Another unique feature is that all four Neptune Trojans appear relatively red, suggesting they all have a similar origin. The tint is similar to Jupiter Trojans, irregular satellites and maybe even comets, but is distinct from some of the farther-flung Kuiper Belt Objects.
Tens of thousands
The known Neptune Trojans are estimated to measure between 60 and 140 kilometres in diameter. From the statistical analysis based on the 25° tilt, the researchers infer that Neptune may have between five and 20 times more of these large objects than Jupiter. Jupiter only has one known Trojan in this upper size range. Based on this difference, astronomers estimate that Neptune's smaller Trojans also outnumber Jupiter's.
Other research implies that Jupiter may have about the same number of asteroids as the main asteroid belt, so astronomers indirectly conclude that Neptune Trojans may outnumber the tens of thousands of asteroids in the main asteroid belt.
However, because Neptune is farther away, spotting these rocky objects is difficult. A cloud of asteroids stalking Neptune from behind, in a corresponding Lagrange point, has not yet been spotted but is predicted to exist.
"Everyone believes there should be another cloud," Chiang told New Scientist. "The reason why people haven't found them there is you're looking right at the Milky Way in that direction." The large number of stars in the background makes spotting faint asteroids difficult. However, planetary motions will make for a better view of any trailing Trojans in about 30 years.
If astronomers prefer not to wait, it may be possible to send the Pluto-bound New Horizons mission through the predicted asteroid clumping (see New Horizons blasts off for Pluto).
Journal reference: Science express (DOI: 10.1126/science.1127173)
"How planets acquire their Trojans has been much discussed by researchers"
I got mine at Walgreens right by the Pharmacy counter.
Awesome comment!
Good find. Thanks for the post.
"$1.04"
"Why does it say 99 cents?"
"It's 99 cents for the condom and 5 cents for the tax."
"Oh...I wondered what held it in place...."
That comment came directly out of Uranus.
"A cloud of asteroids stalking Neptune from behind."
Where else would they be stalking, lol? And, I'm glad this is Neptune, instead of another, unfortunately named planet, that is often the butt of scatalogical humor.
So how does this affect their football team?
Plans are afoot to name the next planet discovered after the Roman god Splinkter.
You mean they're not circling Uranus?
The last time I took that Trojan out of my wallet there
WAS a kind of Neptunian cloud. Yep just checked again,
it's still as good as new even though I bought it in 1965.
"Plans are afoot to name the next planet discovered after the Roman god Splinkter."
Well, let's just hope Splinkter doesn't have a cloud of asteroids stalking behind. We already have enough trouble maintaining a serious level of discussion about Uranus as it is.
Saw the headline for the tread and just had to post. Problem is others have beat me to the punch with condom comments.
No Thanks on these ones!!!
bookmark
Tiny Tim originally sang "Tiptoe Thru the Neptune with me"...but it did not sell. So he switched to Tulips!
another version:
http://msnbc.msn.com/id/13352543/
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