Astronomers find bounty of failed stars

Oct 11, 2011
Brown dwarfs in the young star cluster NGC 1333. This photograph combines optical and infrared images taken with the Subaru Telescope. Brown dwarfs newly identified by the SONYC Survey are circled in yellow, while previously known brown dwarfs are circled in white. The arrow points to the least massive brown dwarf known in NGC 1333: it is only about six times heftier than Jupiter. Credit: SONYC Team/Subaru Telescope

A University of Toronto-led team of astronomers has discovered over two dozen new free-floating brown dwarfs, including a lightweight youngster only about six times heftier than Jupiter, that reside in two young star clusters. What's more, one cluster contains a surprising surplus of them, harbouring half as many of these astronomical oddballs as normal stars.

"Our findings suggest once again that objects not much bigger than Jupiter could form the same way as do. In other words, nature appears to have more than one trick up its sleeve for producing planetary mass objects," says Professor Ray Jayawardhana, Canada Research Chair in Observational Astrophysics at the University of Toronto and leader of the international team that made the discovery.

straddle the boundary between stars and planets. Sometimes described as failed stars, they glow brightly when young, from the heat of formation, but cool down over time and end up with atmospheres that exhibit planet-like characteristics. Scientists think that most brown dwarfs may have formed like stars, in isolation from contracting , but some of the puniest free-floaters may have formed like planets around a star and later ejected.

The findings come from observations using the in Hawaii and the Very Large Telescope (VLT) in Chile during the Substellar Objects in Nearby Young Clusters (SONYC) survey. Astronomers took extremely deep images of the NGC 1333 and rho Ophiuchi with Subaru at both optical and . Once they identified candidate brown dwarfs from the very red colors, the research team confirmed them with spectra taken at Subaru and the VLT. The team's findings will be reported in two upcoming papers in the and presented this week at a scientific conference in Garching, Germany.

The six-Jupiter-mass brown dwarf found in the NGC 1333 cluster is one of the least massive free-floating objects known. "Its mass is comparable to those of giant planets, yet it doesn't circle a star. How it formed is a mystery," said Aleks Scholz of the Dublin Institute of Advanced Studies in Ireland, lead author of one paper and a former postdoctoral fellow at the University of Toronto.

Several other newly identified brown dwarfs in both NGC 1333 and rho Ophiuchi clusters have masses below 20 times that of Jupiter.

"Brown dwarfs seem to be more common in NGC 1333 than in other young star clusters. That difference may be hinting at how different environmental conditions affect their formation," says University of Toronto's Koraljka Muzic, lead author of the second paper.

"We could not have made these exciting discoveries if not for the remarkable capabilities of Subaru and the VLT. Instruments that can image large patches of the sky and take hundreds of spectra at once are key to our success," said co-author Motohide Tamura of the National Astronomical Observatory of Japan.

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jsa09
3 / 5 (2) Oct 12, 2011
What's more, one cluster contains a surprising surplus of them, harbouring half as many of these astronomical oddballs as normal stars.


I am not surprised at all. I would expect a range in sizes perhaps similar to a bell curve from very small to very large.

The very small may be asteroid size and the very large could be blue giant or perhaps bigger.

The middle of the range may well be smaller than brown dwarf, it will be a decade or more before we have statistics for smaller 'stars' to guess just how many may be out there.
kevinrtrs
1 / 5 (5) Oct 12, 2011
Sometimes described as failed stars, they glow brightly when young, from the heat of formation, but cool down over time and end up with atmospheres that exhibit planet-like characteristics.

Please clarify this: Just how do they know that this process took place? Was it something that was actually observed over say the last 100 years or is this theoretical speculation again? I somehow suspect the latter, in which case they should not state it as if it were fact. Instead they should make it clear that this is their conjecture at this stage.
kevinrtrs
1 / 5 (6) Oct 12, 2011
Its mass is comparable to those of giant planets, yet it doesn't circle a star. How it formed is a mystery,

Truth, honesty and humility leads to great discoveries. It's refreshing to find some of it here. Since this doesn't fit into the accretion model in any shape or form, where does that leave that out-moded failure of a model in the scientific field? Like I said before - it's time to get a new model. The incumbent one is currently being falsified with almost EVERY new observation. One can only hang on to a conjecture for so long before one has to admit that it's not working and something new needs to be thought out. Where are the truly courageous scientists of old - those willing to put some real strong words into the public domain?
aroc91
5 / 5 (1) Oct 12, 2011
Sometimes described as failed stars, they glow brightly when young, from the heat of formation, but cool down over time and end up with atmospheres that exhibit planet-like characteristics.

Please clarify this: Just how do they know that this process took place? Was it something that was actually observed over say the last 100 years or is this theoretical speculation again? I somehow suspect the latter, in which case they should not state it as if it were fact. Instead they should make it clear that this is their conjecture at this stage.


Brown dwarfs aren't as rare as you're making them seem to be. We've observed quite a few.
jsa09
not rated yet Oct 13, 2011
I don't understand the problem that some people have with accretion of stars. What has size got to do with it?

I think in most cases size is considered important because we know that big stars are formed and that that they seem to appear out of dust therefore they accreted. Fine. But since we have equal knowledge of asteroids and comets then there should be no reason why these cannot form in a like manner out of dust clouds. It may turn out that it is slowly growing balls that eventually form stars and that perhaps it is extremely common for balls of matter to stop growing long before getting clouds of matter big enough to form stars.

In other words the smaller objects could perhaps be more common than the larger ones.

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