UKIRT Astronomers Discover Cool Stars in Nearby Space
An international team, led by British astronomers using the United Kingdom Infrared Telescope (UKIRT) in Hawaii, have discovered what may be the coolest sub-stellar body ever found outside our own Solar System. This object is technically known as a brown dwarf but what has excited astronomers is its very peculiar colours, which actually make it appear either very blue or very red, depending on which part of the spectrum is used to look at it. The object is known as SDSS1416+13B and it is in a wide orbit around a somewhat brighter and warmer brown dwarf, SDSS1416+13A. The brighter member of the pair was detected in visible light by the Sloan Digital Sky Survey. By contrast, SDSS1416+13B is only seen in infrared light. The pair are located between 15 and 50 light years from the Solar System, which is quite close in astronomical terms. "This is the fourth time in three years that UKIRT has made a record breaking discovery of the coolest known brown dwarf, with an estimated temperature not far above 200 degrees Celsius", says Dr Philip Lucas of the University of Hertfordshire's School of Physics, Astronomy and Mathematics. "We have to be a bit careful about this one because its colours are so different than anything seen before, that we don't really understand it yet. The colours are so extreme, that this object will keep a lot of physicists busy trying to explain it."
An international team, led by British astronomers using the United Kingdom Infrared Telescope (UKIRT) in Hawaii, have discovered what may be the coolest sub-stellar body ever found outside our own Solar System.
This object is technically known as a brown dwarf but what has excited astronomers is its very peculiar colours, which actually make it appear either very blue or very red, depending on which part of the spectrum is used to look at it.
The object is known as SDSS1416+13B and it is in a wide orbit around a somewhat brighter and warmer brown dwarf, SDSS1416+13A. The brighter member of the pair was detected in visible light by the Sloan Digital Sky Survey. By contrast, SDSS1416+13B is only seen in infrared light. The pair are located between 15 and 50 light years from the Solar System, which is quite close in astronomical terms.
"This is the fourth time in three years that UKIRT has made a record breaking discovery of the coolest known brown dwarf, with an estimated temperature not far above 200 degrees Celsius", says Dr Philip Lucas of the University of Hertfordshire's School of Physics, Astronomy and Mathematics. "We have to be a bit careful about this one because its colours are so different than anything seen before, that we don't really understand it yet. The colours are so extreme, that this object will keep a lot of physicists busy trying to explain it."
Brown dwarfs are 'failed stars': gas balls that condensed from interstellar clouds but weren't massive enough to ignite hydrogen in their cores. To be more precise: they could ignite deuterium (the rarer isotope of hydrogen with one neutron attached to the one proton in its nucleus), but burnt it off quickly, and have just cooled ever since. This deuterium-burnout can happen between 13 and 80-85 Jupiter masses.
For the naked eye, if we could fly a spaceship near them, most known brown dwarfs would appear in a faint red glow, having temperatures like molten steel or lava. However, these cool brown dwarfs discovered by the UKIRT Infrared Deep Sky Survey would be illuminated only by starlight and polar lights, and possibly have atmospheres with bands and storms like Jupiter. "Otherwordly"...
The quote is from the press release; the abstract also says that they are 10 billion years old -- that explains how this object, estimated at 30 Jupiter masses, could cool down so much. (All brown dwarfs are roughly the same size as Jupiter, only progressively more dense, so heavier ones cool slower.) *Lunatic*, n. One whose delusions are out of fashion.
The astronomers didn't happen to find a black monolith circling SDSS1416+13B as well, did they?
Presently it appears that there is a qualitative difference between gas gas giant planets and brown dwarfs: brown dwarfs form by gas accretion in cloud condensation cores, gas giants however are seeded by dust-to-rock coalescing in discs (the same process forming rocky planets like ours and icy ones like Pluto or Halley's Comet). An evidence is that very few brown dwarfs orbit stars. I don't know if there is a hypothesis explaining the upper mass cutoff for planets; on the other hand, cloud condensation cores under 13 Jupiter masses would be possible theoretically, so there is a terminology gap. *Lunatic*, n. One whose delusions are out of fashion.
I fear I'll have a hard time explaining why it is exciting
EDDIE: Improbability Factor at one to one. Normality is restored. We seem to be in some kind of cave guys. Do you like caves? There's something very strange about this one. ZAPHOD: Caves are cool. Let's get out there and relate to it. EDDIE: This one's very cool. And you know that gives me pause for thought, because the planet Brontitall - which is where I think we are - is meant to have a warm rich atmosphere. FORD: Perhaps we're on a mountain. EDDIE: Nope, no mountains on Brontitall. FORD: Well, let's get out and see. I'm hungry for a little action. ARTHUR: In a cave? EDDIE: On Brontitall? [Sharp intake of breath] FORD: Yeah! In a cave, wherever! You make your own action. ZAPHOD: Sling open the hatch computer. EDDIE: Er, Okay. [The hatch opens] EDDIE: You go out and have a good time and I'm sure that everything will be just hunky-dory.
ZAPHOD: Caves are cool. Let's get out there and relate to it.
EDDIE: This one's very cool. And you know that gives me pause for thought, because the planet Brontitall - which is where I think we are - is meant to have a warm rich atmosphere.
FORD: Perhaps we're on a mountain.
EDDIE: Nope, no mountains on Brontitall.
FORD: Well, let's get out and see. I'm hungry for a little action.
ARTHUR: In a cave?
EDDIE: On Brontitall? [Sharp intake of breath]
FORD: Yeah! In a cave, wherever! You make your own action.
ZAPHOD: Sling open the hatch computer.
EDDIE: Er, Okay.
[The hatch opens]
EDDIE: You go out and have a good time and I'm sure that everything will be just hunky-dory.
How cool is that!
*Lunatic*, n. One whose delusions are out of fashion.
You can see the 140 m wide impacted asteroid at the end of the debris field, the end of which has a strange structure (presumably containing the biggest chunks thrown out by the collision).
The small spot at the lower left end, which is the bright spot in the magnified inset, is the 140 m wide asteroid. The beginning of the comet-like diffuse thing is the debris kicked up, and the 'tail' is light dust, moving further with the help of solar wind, direct radiation pressure and the Yarkovsky effect (anisotropic thermal re-radiation of the absorbed sunlight).
When the object was discovered, it was indeed first thought to be a comet with a completely evaporated core, but a comet looked less likely when its orbit was found to be a regular one in the main asteroid belt. Then a ground-based large telescope discovered the small asteroid next to the tail, and Hubble revealed the X-shaped mark made up by the larger pieces of the derbis. *Lunatic*, n. One whose delusions are out of fashion.
