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back to article Room-temperature brown dwarf spied just 9 light-years off

Scientists perusing data collected by NASA's Wide-field Infrared Survey Explorer (WISE) have spotted some really cool stars – brown dwarfs with an atmospheric temperature as low as an agreeable 25°C. Dubbed "Y dwarfs", these objects have hitherto eluded astronomers hunting them at visible wavelengths, although WISE has finally …

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Boffin

Can anyone enlighten me?

What is it that distinguishes a brown dwarf from a large gas-giant planet?

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Ru
Boffin

Easy.

Giants are a lot smaller than Dwarfs.

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Boffin

Re: Can anyone enlighten me?

Size, and whether or not hydrogen fusion occurs within it.

Taking some figures from our favourite on-line encyclopaedia, a stellar body needs to have a mass of approximately 8% of that of our Sun for the core pressure and temperature to get high enough for gravity-induced hydrogen fusion to occur; this also tends to "burn" lithium as well.

However, the mass of a sub-stellar body may yet be high enough for other forms of fusion to occur, using "heavy" isotopes of hydrogen - primarily deuterium (hydrogen-2) - and also possibly "burning" lithium, usually when the it is younger and hotter (from gravitation condensation/contraction).

If anyone can correct any mistakes I've made, please do so! :)

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Mushroom

Re: Can anyone enlighten me?

I think there's some debate over whether or not there is a continuum with stars at one end and gas giants at the other. The key definition of a star, though, is presumably that it has sustained fusion in its core at some stage. Deuterium fusion (D +p -> 3He + gamma) requires objects of around 15 Jovian masses, IIRC.

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Boffin

Not a lot

A Brown Dwarf is basically a gas giant large enough that fusion can be sustained at the centre, though it's not really a star either on account of being quite dark and distinctly tepid.

IIRC.

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Facepalm

Might have something to do with....

Don't planets need a star to orbit to be classed as a planet!

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Boffin

yup

mainly based on mass.

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Mushroom

I was

Thinking the exact same thing when I read this. So I did some research (not a lot I admit)

http://atramateria.com/the-coolest-neither-planet-nor-star-brown-dwarf/

and

http://en.wikipedia.org/wiki/Brown_dwarf#Distinguishing_low-mass_brown_dwarfs_from_high-mass_planets

Should help explain a bit.

Explosion: because brown dwarfs would like to start a reaction.

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Boffin

difference

I'd say that it's either mass or the fact it doesn't orbit other celestial body in close proximity (as all stars orbit galactic center).

The difference is as significant as the stuff that makes Pluto an ex-planet.

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Alien

Fiat Lux!

The classification originates from those smarty pants at Harvard:

http://en.wikipedia.org/wiki/Stellar_classification

It's been extended over the years and, like many classification schemes in astronomy (in my experience), it's a living thing as more objects are discovered that don't quite fit.

http://en.wikipedia.org/wiki/Brown_dwarf

Covers your very question - it suggests (although no reference given) that an object must have sustained fusion at some point to be counted as a star - seems reasonable.

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Silver badge

doesn't orbit other celestial body in close proximity

<cough>Binaries<cough>

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Alien

homeless planets

@ cynical git: apparently not all of them, some are homeless!

http://news.sciencemag.org/sciencenow/2011/05/homeless-planets-may-be-common.html?ref=hp

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Not just proximity to a star or...

...what would that make a Brown-Dwarf binary system them? Two planety yet starry things orbiting one another...?

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Anonymous Coward

That brings up the question

what's the surface gravity of those things?

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Surface?

It's gas all the way down.

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Um

It either gets dense enough to form a liquid/solid core like Jupiter or gets so hot it's plasma. So no.

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Anonymous Coward

Pointless picture?

"NASA explains the purple hue shown in its artist's impression of a Y dwarf was chosen mainly for artistic reasons".

In other words, here is a picture illustrating something that noone knows what it looks like.

Oh, hum, wait, what?

If people are rewarded according to their imagination, the guy in charge of the budget is on a 7 figures salary.

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Meh

True true

Based on that way of thinking never again should a dinasour be depicted as noone knows what colour they were.

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Joke

What about

Dinasweets?

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Windows

Purple hue?

Obvious.

If it'd been coloured as a "Brown Dwarf", people would've mistaken it for a turd.

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Anonymous Coward

RE: true true

Sorry to hear that you need the help of a NASA artist to grab the concept of a star being a sphere. If it helps, you can create your own explanatory star picture by choosing the "circle" tool from Paintbrush.

In addition to shape, the point of dinosaurs illustration is to convey a sense of scale, which this pictures also fails to convey.

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Re:- sense of scale (Cricri - wayback when).

. <----- Uranus

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WTF?

Near...

"Finding brown dwarfs near our sun is like discovering there's a....."

For very extremely large values of "Near"...

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Thumb Up

Titties? We dont neeed no stinkin' titties!

In space terms 9 light years is next door. Just because you dont own a car doesnt mean the next town over isnt relatively close.

For large values of close.

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Yag
Trollface

very extremely large values of "Near"...

...are still ok for a mind-bogging ludicrously large universe :)

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Paris Hilton

Re: Near

I dunno....

A pencil 3 desks away is not near.

A cinema 1 street away is near, despite it being further away than the pencil.

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Coffee/keyboard

y.a.f.t.

Please see Ru @ 13:29 for the definitive explanation of this phenomenon. A work of genius.

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Pint

Obligatory quote

Space is big. Really big. You just won't believe how vastly, hugely, mindbogglingly big it is. I mean, you may think it's a long way down the road to the chemist's, but that's just peanuts to space.

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FAIL

Really?

"With WISE, we may even find a brown dwarf closer to us than our closest known star."

Since our "closest known star" is the one we are in orbit around, I seriously doubt the accuracy of this statement....!

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There's one in my back pocket.

Can't have it though - go find your own.

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Anonymous Coward

Sumerians already spotted it...

... And named it Nibiru!

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Joke

Point of order...

Finding a brown dwarf closer than our closest star would be quite a coup considering the closest known star is only 1 AU away from us. One would think that an even closer brown dwarf would have already been detected as a consequence of its gravitational influence. (Such as hurling the Earth out if its nice stable orbit into the deep cold of interstellar space.)

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Huh?

"With WISE, we may even find a brown dwarf closer to us than our closest known star"

What, closer than the Sun?

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Holmes

great minds

And petty people all think alike look at the three posts all together pointing out the obvious.

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Holmes

You get a better class...

of pedant here at the Reg.

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Silver badge

Last refuge of life?

Interesting to note that such a "failed star" might become the last refuge of life in a dying universe, tens or hundreds of billions of years from now. Like the sun, they stay warm by nuclear fusion, but at such a low rate that they'll probably be the last places left where liquid water (and therefore life as we know it) can exist.

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as we know it?

I find it incredibly hard to believe that life will be anything like it is now by the point we're approaching the heat death of the universe. In just 3.5 billion years we've gone from a single anaerobic bacteria to the duck-billed platypus*, discarding countless other forms, and possibly many different basic biochemistries, along the way, and we're not even halfway through the life of this single planet.

* platypus = obviously the most complex form of life on the planet. Unnecessarily complex.

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Silver badge

Water ...

We don't know much about what was on the surface of the earth before large parts of it got covered with liquid water, but there's no evidence that life can exist without water.

All terrestrial life still extant shares a common basic biochemistry, with features such as RNA coding for proteins built from a common set of amino-acids, ATP energy-transport, lipid membranes, and an aqueous support medium. There must have been simpler life-systems leading up to this system (think scaffolding), but we have no evidence of what it might have been. I think it extremely unlikely that whatever it was, it did not require liquid water to function. Water is a lowest-common-requirement for all the more complex subsystems.

I'm guessing that complex organisms find it hard or impossible to evolve in the atmospheres of gas giants or cool brown dwarfs. So they might remain at the single-celled stage "forever" until the brown dwarf no longer provides liquid water. Or until some exceptionally unlikely event happens, and multicellular or even intelligent life arises in the dark cold tail-end of a dying universe.

BTW if you envisage galaxies as having been "mined-out" by interstellar-scale intelligences, then think of a brown dwarf ejected from its galaxy and drifting forever alone and undetectable through one of the voids in intergalactic space. That would, in fact, be a more stable environment than one stil in a chaotic orbit around the centre of a galaxy.

The most complex form of life on the planet is surely some sort of insect. Butterfly: Egg, caterpillar, chrysalis ... complete dissolution of the caterpillar to a sort of living soup, and re-birth as a butterfly. Or spider-hunting solitary wasp. Somewhere in the egg is a program which allows it to hunt and paralyze spiders without becoming prey, dig a burrow, install the spider, lay an egg. I wish someone could tell me where and how.

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Boffin

they changed it !

Thats just mean - the categories used to be Wow Oh Be A Fine Girl Kiss Me Right Now Sweetie

(hmm, maybe the best way to find these things is to "look out the corner of your eye").

brown dwarf star => nuclear reactions started upon gravitational collapse but then ran out of oomph

gas giant planet => not big enough for collapse to initiate nuclear reactions

e.g. jupiter ~ 1 order of magnitude too small to be any kind of star

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Mnemonic

Only Big And Famous Guys Know More Love Than You?

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Thumb Up

Fish sticks and custard

(hmm, maybe the best way to find these things is to "look out the corner of your eye").

Nice!

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Or as my lecturers would say...

Oh Bugger, A Fucking Goat Kicked Me

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Unhappy

When I were a lad

and in my own experience, the S stood for Smack

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Anonymous Coward

Re: Fish sticks and custard

Are you a gay fish? With a custard/gunge fetish?

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Silver badge

Jupiter is a very dark brown dwarf

Jupiter emits more radiation than it recieves from the sun. Fusion at a very low rate is the probable source of the excess heat. Jupiter's core is believed to be mostly hydrogen in its theoretically predicted high-pressure metallic form.

The Earth also emits more heat than it receives. In this case we have good reason to believe that the sources are radioactivity and tidal friction, and possibly also ongoing crystallisation of the Earth's solid inner core from its liquid outer core.

For the Earth, the excees heat may have been the difference between a living planet and a snowball, in the early days when the sun was somewhat cooler and the moon was a lot closer.

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Anonymous Coward

Room-temperature brown dwarf

that's not enough fibre, that is

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Anonymous Coward

whereas

a gas giant clearly has quantities of Ruby Murray in its immediate prehistory. They are often differently hued and, it goes without saying, they are often substantially above room temperature.

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Colour

I believe the NASA's artist should know very well what visible colour will Y-Dwarf be @25C surface temperature - black.

As to the colour of reflected light if someone will shine a flashlight on it - that's a different matter.

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Missing mass

Is it possible that the "missing mass" in the universe could also be room temperature or lower and hence not previously visible? (I've always suspected something like this)

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Boffin

isnt?

Most of the missing mass actually vacuum energy of space itself? Virtual particles are particles too.

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