Star Cooler Than Venus Found

crossconnects writes to mention that Discovery is reporting that astronomers have found a nearby star with a mild surface temperature of 660 degrees fahrenheit. "The spectacularly unspectacular object is of special interest because it falls right smack in the middle of the final frontier that divides mega-planets from the puniest stars. Stars in that realm theoretically qualify as an entirely new stellar type -- what's called a Y class dwarf."

Comments

Not that hard

[0racle]

Venus never was that hip.

Re:Not that hard

[riskeetee]

Agree, Serena's hotter.

Publication at arXiv.org

[Jugalator]

Here's the actual publication on the discovery:
http://arxiv.org/abs/0802.4387

... or straight to the PDF:
http://arxiv.org/pdf/0802.4387v2

Nuclear fusion?

[smolloy]

I thought the definition for a star was that there had to be fusion occurring at its core. TFA doesn't mention it, but I'm amazed that this object can be this cool, yet still have a nuclear furnace at its heart.

Fascinating stuff indeed.

Re:Nuclear fusion?

[Tenebrousedge]

Stars above about 13 jupiter masses fuse deuterium and above 65 jupiter masses also fuse lithium, according to Wikipedia. Below 13 jupiter masses, well, it's hard to say...

Re:Nuclear fusion?

[Sique]

If you don't have much fusion, and not very much convection within the star, then the heat gets to the surface very slowly (it can take up to billions of years!), and distributed along the while surface the energy stream is low.

Re:Nuclear fusion?

[Ironsides]

TFA doesn't mention it, but I'm amazed that this object can be this cool, yet still have a nuclear furnace at its heart.

Perhaps it's using cold fusion? (ba dump dum)

Re:Nuclear fusion?

[g0dsp33d]

Or physicists can do what they usually do and discover "dark" fission.

Sigh, Bad English / Hmm - Biosphere?

[TexVex]

FTA: That means any water in there atmospheres will condense into droplets of water vapor

Aside from the bad English, the quoted bit is actually the most interesting part of the article. Does that mean that a particularly low-temp one of this newly discovered kind of dwarf star could be a self-contained biosphere, with a source of heat in the center surrounded by a life-sustaining atmosphere with liquid water in it?

Dyson Sphere is to Ringworld as Cool Dwarf is to Smoke Ring! :)

Re:Sigh, Bad English / Hmm - Biosphere?

[IndustrialComplex]

While the conditions are almost there for life similar to that of Earth to develop, the problem is that there are a lot of 'almosts', and I'm willing to bet that almost won't cut it in this case.

Just two of the things that would probably cause problems is that it is likely a very turbulent atmosphere when compared to that of Earth, and of course, there is also the likely high amount of radiation that is bouncing around (it is a star after all).

If we are thinking DNA/RNA based life, the radiation involved would make it very hard to reproduce.

As I type this more and more obstacles are coming to light, but I couldn't imagine a situation in which life could occur on a star.

Re:Sigh, Bad English / Hmm - Biosphere?

[strack]

Radiation? The only radiation source is fusion at the core of the star, The only thing this star radiates is Infrared. i.e. Heat. to get any ionizing radiation, youd prolly have to be near the core. It probably looks like a particularly active really big gas giant.

Re:Sigh, Bad English / Hmm - Biosphere?

[IndustrialComplex]

That is a good point, I forgot that it is mostly infrared radiation. However, just because there is no visible light, does that mean it is generating no radiation above the visible spectrum? I'm assuming that this star is fusing Deuterium and Tritium, which I believe does produce Gamma Rays.

Brown dwarfs have been observed to produce X-rays and Gamma rays. So just because this one produces no visible light does not mean it isn't producing a large amount of high energy radiation.

I'm one of Venus' best friends...

[Anonymous Coward]

... and I have a hard time believing there are many stars out there that are even "as cool" as Venus. Venus is so fucking awesome that it's just absurd for anybody to claim they've found a star cooler than her.

Re:Fahrenheit

[amRadioHed]

No, not when audience is the American public.

Re:Fahrenheit

[treeves]

What, they should have used Rankine?

Re:Fahrenheit

[servognome]

Even with an American audience at the temperatures discussed Fahrenheit has no real meaning.
The usefulness of Fahrenheit is how the range of 0 - 100 reflects weather temperatures people have experienced.
Temperatures beyond common experience are better expressed in Celsius.

Re:Fahrenheit

[Jugalator]

Even if it's the scientific American public?

Re:Fahrenheit

[duffel]

Then we should use Degrees Delisle, which has the added bonus of going backwards. Body temperature is at 95 Delisle. The sun (ours, that is) is at negative several thousand degrees Delisle.

Re:Fahrenheit

[duffel]

What, they should have used Rankine? Well, in the context, it makes about as much sense as the Kelvin scale... an arbitrary step size with absolute zero being the zero point. Sounds sensible to me! Probably would be better than Celsius or Fahrenheit. Alas, Kelvin got there ten years earlier, so it's the Celsius scale's step size for the accepted absolute scale. Still a bit arbitrary. Perhaps we should come up with a new scale that encompasses absolute zero and a very well defined temperature that makes sense on an absolute/astronomical level? Perhaps a logarithmic scale? Any ideas?

Re:Fahrenheit

[Jonathunder]

In a scientific article, I would expect stellar temperatures to be given in Kelvins.

In a popular article, Celsius or Fahrenheit (depending on country) are probably expected and more understandable to a general audience.

Ideally, any good article would give the measurement or estimate in the original units first (and with the original degree of precision), followed by a conversion if needed for the expected audience.

Re:Fahrenheit

[jd]

The "temperature" of the Big Bang is the theoretical hottest you can ever get, since at that point all mass was in the form of energy, and therefore you had the maximum energy at the maximum density. Nothing can ever exceed that. Thus, if you knew what that was, you could assign it a fixed value as your upper end of the scale. The ideal would be to then have a set of functions (linear, logarithmic, whatever), where a given function was selected for a specific type of application, with the exception of some specific function chosen as the 'standard'.

Discovery Channel's Target Audience != Scientists

[GradiusCVK]

To some degree, you are correct; American scientists, the target audience of the original publication, would prefer the Kelvin unit, which was indeed used in the original publication. However, I don't think the Discovery channel's target audience is primarily scientists but rather the American public, which prefers Farenheit - hence the use of that unit on the Discovery channel's website (the location of TFA).

Re:Fahrenheit

[amRadioHed]

600 F has no meaning? The dial on my oven goes up to 600 degrees. It's also the temperature gasoline ignites at. We are hardly talking about astronomical temperatures beyond our comprehension.

Re:Fahrenheit

[ultranova]

The "temperature" of the Big Bang is the theoretical hottest you can ever get, since at that point all mass was in the form of energy, and therefore you had the maximum energy at the maximum density. Nothing can ever exceed that.

Since the volume of space at t=0 was zero, but the energy content was not, the temperature at t=0 is infinite. That isn't useful for determining a scale. Alternatively, if the energy content was zero, then the temperature is lim(x->0) x/x, which is 0. If energy is zero but volume is nonzero, then temperature is 0/x (x>0), which is also 0. And if both volume and energy are nonzero, then you get a very large but finite amount, which is exceeded by classical black holes, where singularity has zero volume but nonzero energy content.

This is, of course, all assuming that neither volume nor energy can be (were not) negative, since if they are, you get all kinds of extra nastiness.

Thus, if you knew what that was, you could assign it a fixed value as your upper end of the scale.

How do you define this numerical value ? How are you going to make such a scale any less arbitrary than Kelvin scale ?

I propose an alternative: since temperature is determined by the average kinetic energy of a particle, use that as a gauge: at the temperature of 1 base unit, the average kinetic energy per particle is 1 Joule.

Alternatively, use the blackbody radiation: the base unit corresponds to the temperature of a blackbody object who's peak of radiation has wavelength of 1 meter.