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 Stars concoct complex molecules

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تاريخ التسجيل : 2010-12-14

PostSubject: Stars concoct complex molecules   Thu Oct 27, 2011 9:14 pm

Relatively complex, carbon-containing molecules have been found in comets and on planets before, thought to have been made elsewhere in our Solar System.

But "unidentified infrared emissions" seen from the cosmos,cheap jerseys free shipping says a new report in Nature, may come from even larger molecules forged near young stars.

They say these "stellar organics" may have been delivered to the early Earth.

Much of the chemistry that happens elsewhere in the cosmos remains mysterious, leaving astronomers to guess how nature assembles molecules.

It has generally been assumed that fairly simple molecules cheap football jerseys could be assembled in the area around young stars, while more complex materials formed later, in cooler conditions.

Adding to the mystery, though, have been unidentified infrared emissions (UIE), emanating from a range of sources in our galaxy and beyond.

This infrared light must come from molecular vibrations - the waggling of one atom relative to another within molecules that absorb light of higher wavelengths from other sources. Light in the infrared is then emitted as the wagglings die out.

Like the strings of a piano, each molecular vibration has its own note,cheap baseball jerseys but the unidentified infrared emissions are a rich, dense "chord" of notes that makes the nature of the emitting molecules extremely difficult to unpick.

Star power
Since the late 1970s, astronomers have been making guesses about what the molecules may be; most recently, they have been assumed to be what are known as polycyclic aromatic hydrocarbons (PAHs) - linked rings of carbon dotted with hydrogen atoms that on Earth are known to be powerful and toxic pollutants.

While these molecules forged near new stars are relatively complex NHL Jerseys Cheap assemblages of atoms, they are not as intricate as molecules that have been spotted elsewhere in the cosmos.

"Complex organics have previously been found in the Solar System - in meteorites, in comets, and on planetary surfaces [such as that of Saturn's moon] Titan," Prof Kwok told BBC News.

"However, the traditional view is that these organics are made in situ in the Solar System."

Prof Kwok and his colleague Yong Zhang looked at the light coming from nascent stars acquired with the Spitzer space telescope, along with light from two novas - explosions of white dwarf stars.

They then devised a theoretical molecule, changing its structure and parts until its molecular vibrational "notes" most closely matched what Spitzer had seen.

Instead of PAHs, the pair's candidate molecule was a rich mixure of the ring-like "aromatic" structures familiar from PAHs and the kinked "aliphatic" chains.

"The implication of our paper is that these Solar System organics cheap nfl jerseys bear resemblance with the organics that are made by stars, or planetary nebulae," Prof Kwok explained, "and it is possible that the Solar System contains remnants of stellar organics."

So it may be that, rather than some rare and yet-to-be-understood chemistry driving the manufacture of such molecules, it may be a far more ubiquitous process that sees complex organic material spewing out from many stars.

But Carey Lisse of Johns Hopkins University's Applied Physics Laboratory said that although young stars may fling complex organic molecules into the "interstellar medium", older, dying stars may be doing the same, and even sweeping up.

He noted a recent work in Astrophysical Journal Letters by Rhonda Stroud of the Naval Research Laboratory in the US, showing how both aromatic and aliphatic molecules could be made in the interstellar medium by passing shock waves from supernovas - and that such shock waves could destroy complex molecules too.

That complicates the picture of how complex organic molecules may end up travelling into other solar systems such as our own.

"The question of whether [complex organics] are made in the Solar System or whether they survive from the interstellar medium is interesting, and it's not clear where the discussion is going - but it is interesting that they have some of this evidence," he told BBC News.

"The role of young stars in 'reseeding' the interstellar medium... is a complicated one; we're not sure how much they destroy versus how much they create. But any evidence we can get of them actually seeding the interstellar medium with complex organics that can for example lead to life is exciting.
http://hell.top-me.com/t24-stars-concoct-complex-molecules
"This [paper in Nature] is a step in the right direction, but it's not the final step."
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