COOL DWARF: This artist's conception illustrates what a "Y dwarf" might look like. Y dwarfs are the coldest star-like bodies known, with temperatures that can be even cooler than the human body.
Image: NASA/JPL-Caltech
Scientists have discovered the coldest type of star-like bodies known, which at times can be cooler than the human body.
Astronomers had unsuccessfully pursued these dark entities, called Y dwarfs, ever since their existence was theorized more than a decade ago. They are nearly impossible to see relying on visible light, but with the infrared vision of NASA's WISE space telescope, researchers finally detected the faint glow of six Y dwarfs relatively close to our sun, within a distance of about 40 light-years.
Y dwarfs are the coldest members of star-like bodies known as brown dwarfs, which are odd objects sometimes known as failed stars.
Brown dwarfs are too puny to force atoms to fuse together and release nuclear energy, and so they have only the little heat they were born with. This heat fades over time until all the light they do emit is at infrared wavelengths. [Photos From NASA's WISE Telescope]
So far, WISE has helped find 100 new brown dwarfs.
The coldest "failed stars"
To see how cool the coldest of these Y dwarfs was, the researchers used NASA's Hubble Space Telescope to analyze its pattern of light. They found this coldest Y dwarf, known as WISE 1828+2650, was colder than 80 degrees Fahrenheit (25 degrees Celsius).
"The brown dwarfs we were turning up before this discovery were more like the temperature of your oven," said astronomer Davy Kirkpatrick, a WISE science team member at the California Institute of Technology in Pasadena, and lead author of a study on the 100 new brown dwarfs. "With the discovery of Y dwarfs, we've moved out of the kitchen and into the cooler parts of the house."
The closest of these Y dwarfs, WISE 1541-2250, is 9 light-years distant. In comparison, the alien star closest to us, Proxima Centauri, is about 4 light-years away. [Video: Getting WISE to Brown Dwarfs]
"Finding brown dwarfs near our sun is like discovering there's a hidden house on your block that you didn't know about," said astronomer Michael Cushing, a WISE team member at NASA's Jet Propulsion Laboratory in Pasadena, Calif., and lead author of the study on the Y dwarfs. "It's thrilling to me to know we've got neighbors out there yet to be discovered. With WISE, we may even find a brown dwarf closer to us than our closest known star."
The coldest brown dwarfs until now were the T dwarfs, which get as cool as about 440 degrees Fahrenheit (225 degrees C). First uncovered in sizable numbers in the late 1990s, the dwarfs led astronomers to ask whether there could be dwarfs even cooler, Kirkpatrick told SPACE.com — for instance, ones that might be older and thus with more time to cool off, or less massive and with less heat to begin with, or both.
Classifying brown dwarfs
Scientists name stars and brown dwarfs based on their temperatures, "with 'O' stars being the hottest, and now 'Y' dwarfs being the coldest,'" Cushing explained.
Most of the letters of the alphabet already have strong associations with other astronomical objects, so "after eliminating these 'used' letters from consideration, there are really only a few left, and those are H, Y, and Z," Cushing added. "Since Y comes after T, we felt it was the appropriate choice. Using Y also leaves room for an additional 'Z' class if astronomers discover even colder objects."
Better understanding Y dwarfs could shed light on how stars and planets form.
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13 Comments
Add CommentSo if it does not support fusion, what is it exactly? Essentially a giant ball of gas?
Reply | Report Abuse | Link to thisMakes you wonder with temperatures that low, if it may be capable of supporting life. That's certainly a rainge in which liquid water can exist, even if perhaps only in cloud form.
Reply | Report Abuse | Link to thisYes they are, although those > 13 * Jupiter's mass (MJ)
Reply | Report Abuse | Link to this"do fuse deuterium and those above ~65 MJ also fuse lithium." Please refer to:
http://en.wikipedia.org/wiki/Brown_dwarf
The wikipedia entry also states:
"A remarkable property of brown dwarfs is that they are all roughly the same radius as Jupiter. At the high end of their mass range (60–90 Jupiter masses), the volume of a brown dwarf is governed primarily by electron degeneracy pressure,[2] as it is in white dwarfs; at the low end of the range (10 Jupiter masses), their volume is governed primarily by Coulomb pressure, as it is in planets. The net result is that the radii of brown dwarfs vary by only 10–15% over the range of possible masses. This can make distinguishing them from planets difficult."
Since they are all about the same diameter as Jupiter and can range up to ~90 Jupiter masses, it seems their principal distinction is the density of their disperse gases and, as discussed in this article, their temperature.
range, I mean...ugh I need to wake up!
Reply | Report Abuse | Link to thisInteresting point, although I think they'd lack the required concentration of complex chemistry necessary to create and sustain life, even if it was delivered by many asteroids...
Reply | Report Abuse | Link to thisIs it really correct to continue calling them dwarfs, likening them to stars at all, when they do not support fusion. We demoted Pluto to a planetoid for less.
Reply | Report Abuse | Link to thisAs I understand, all but the smallest are thought to form just like stars - most are thought to initiate fusion but are unable to sustain it.
Reply | Report Abuse | Link to thisOn the other hand, I have no reason to worry about their official classification - they can call them 'swamp gas' if they like...
This may be true, although some may contain heavier elements leftover from billion year old supernovas of the past. Honestly, I was giving some thought to the idea of possible binary systems containing stars like these that we simply haven't discovered yet. We do know that binary systems don't necessarily require the stars, or "star-like bodies" to be right atop one another. I think it would be very interesting to find a Y brown dwarf interlocked with a cool white dwarf, which would shower it with heaver elements. But who knows, our scientific community would probably just classify it as a gas giant planetoid with an unusual orbit. Who knows, there is so much about our universe(s) that is yet undiscovered. I would like to see the day in which we're able to detect the elusive & hypothetical "dark matter", only to find "dark life" along with it! Alas, that is doubtful in our lifetimes.
Reply | Report Abuse | Link to thisRegarding dark matter, I'm sorry to disappoint you, but no one has yet dissuaded me (and a few physicists) from thinking it was all just a mistake. Please refer to my previous comment for a more complete explanation:
Reply | Report Abuse | Link to thishttp://www.scientificamerican.com/article.cfm?id=ordinary-geniuses-book#comment-01
But jtdwyer, aren't we talking about "dark matter" here? Cooler than the human body? Who's to say objects can't exist at all temperatures down to three degree background radiation, and any mass less than a black hole? Instead of a gas body, why wouldn't it eventually be solid, maybe iron from a used up star? At cosmic distances, why isn't "dark matter" simply something that doesn't glow in a wavelength where we can differentiate it, and isn't close enough to something glowing for us to detect reflected life? What's the big mystery about it?
Reply | Report Abuse | Link to thisConsidering the possible number of very dark bodies out there, is it any wonder that we haven't been visited by ET?
Please copy responses to danrob@efn.org
See? I told you! Nemesis is out there, as cold and invisible as I've been tellin' ya! It's coming to get us, and we won't see it coming! (Do I need to rise the JK sign here?)
Reply | Report Abuse | Link to thisThe formation criteria for brown dwarves vs. gas giants seems confusing (and iffy) to me. But hey, I agree with jtdwyer in that they can call them what they want...
A good point is, how much of "dark matter" is actually cold and unlit "normal" matter that we're just missing? Seems much more likely to me than all this hoccus-poccus with dark particles. After all, we keep finding out that 'There are older and darker things than Orcs in the deep places of the world' and of space, too.
The requirements for dark matter necessary to produce the observed galaxy rotational characteristics, incorrectly presuming that Kepler's laws of planetary motion apply to spiral galaxies, is that an enormous mass extends far beyond the boundaries of the visible galaxy. Please see
Reply | Report Abuse | Link to thishttp://www.eso.org/public/images/eso1217b/
Discrete objects of non-luminous matter in an enormous enveloping halo would each gravitationally interact with ordinary stars at the galactic periphery - an effect that is not observed.
Most critically, an enormous galactic halo of discrete, non-luminous objects of mass would be illuminated by nearby and background energetic EM emissions from supernovae and AGNs, etc. That is why mysterious forms of dark matter are thought to consist of unidentified special particles that, in addition to not emitting EM radiation, for some reason do not interact with EM radiation. Non-luminous object composed of 'ordinary' matter could not meet these requirements.
Also, please refer to my brief commentary:
Reply | Report Abuse | Link to thishttp://www.sciencewithoutfiction.com/uploads/JDwyer.PDF
It includes several (of many) references to supporting research reports produced by qualified physicists.