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Exoplanets (formerly known as Extrasolar Planets)
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punychicken
PostPosted: 16-04-2002 18:34    Post subject: Exoplanets (formerly known as Extrasolar Planets) Reply with quote

Found this site about extrasolar planets . Its got maps of the sky too so you can plot the stars, or at least stare at a relative section of the sky and wonder!! Very Happy

Here is the chart for the northern hemisphere .

SO! now we know where... how we going to get there?
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eljubbo
PostPosted: 13-03-2003 12:16    Post subject: Hubble discovers new planet Reply with quote

Science article from NY Times

Scientists Find Extrasolar Planet With Atmosphere Much Like Jupiter
By JOHN NOBLE WILFORD


The Hubble Space Telescope has detected an extensive atmosphere of hydrogen enveloping and escaping from a newfound planet of a distant star, scientists reported yesterday.

The discovery comes as no surprise, astronomers say, but is important nonetheless as apparent confirmation that the extrasolar planets observed so far not only are much like the solar system's Jupiter in size but also are similarly huge gaseous bodies.

In an announcement by the European Space Agency and NASA, a French-led research team said three separate observations by the Hubble telescope in 2001 revealed a hot and puffed-up hydrogen atmosphere surrounding a planet orbiting the star HD 209458, in the constellation Pegasus 150 light-years from Earth. Details are described in today's issue of the journal Nature.

The most astonishing aspect, said the team leader, Dr. Alfred Vidal-Madjar of the Astrophysics Institute of Paris, is that the planet is so close to the searing heat of its parent star that the dense atmosphere reaches temperatures of about 18,000 degrees Fahrenheit and is boiling off and evaporating at a rate of perhaps 10,000 tons a second. The escaping hydrogen was detected extending across 125,000 miles, trailing the planet like a comet's tail.

The scientists said analysis of the observations showed that hydrogen atoms in the extended atmosphere had large velocities relative to the planet. Thus, they concluded, the hydrogen "must be escaping the planetary atmosphere."

As a result, astronomers said, the planet may already have lost a considerable amount of its mass. Much of it may eventually disappear, leaving only a dense core about 10 times the mass of Earth.

"The implication is that planets initially located even closer to their stars would not survive long," Dr. David Charbonneau of the California Institute of Technology said in an accompanying article. That, he added, "agrees with the observed paucity of extrasolar planets in such orbits."

The newfound planet, designated HD 209458b, is one of more than 100 extrasolar planets detected since 1995. Like several other of these planets, HD 209458b is known as a "hot Jupiter," an object that orbits precariously close to its star. These objects presumably formed in the cold outer reaches of the star system and then spiraled into their close orbits.

This particular planet — with a diameter 1.3 times that of Jupiter, and two-thirds its mass — orbits its star at a distance of only four million miles, so close that it makes a complete circuit every 3.5 days. By comparison, Mercury, the planet closest to the Sun, orbits at a distance of 36 million miles, completing the orbit in 88 days. Jupiter, the closest gas giant in the solar system, is almost half a billion miles from the Sun.

The atmosphere study was based on observations by the Hubble telescope's imaging spectrograph. As the planet passed across the face of its star, causing a slight dimming of the star's light, the spectrograph measured how the planet's atmosphere filters that light. During such a transit, the starlight is scattered and acquires a signature from the intervening atmospheric atoms.

The remarkable strength of the light-dimming signals, the basis for inferring a correspondingly extensive atmosphere, surprised some scientists. They advised caution in interpretations until any possible contamination from other light sources could be ruled out.

Besides Dr. Vidal-Madjar, the team included other scientists from the Astrophysics Institute of Paris as well as researchers from the Geneva Observatory in Switzerland and the University of Arizona.

website here
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Anonymous
PostPosted: 13-03-2003 15:23    Post subject: Reply with quote

This planet must have been pretty large to begin with... and if it is losing atmosphere at this rate, eventually it will be stripped down to the rocky core-
this might be only a few times the size of the Earth but will probably be much more massive- so you would have a red hot high gravity world.
However the jupiter-sized-planet-next-to-the-star scenario is quite common- it happens at 51 Pegasi and 55 Cancri as well - and these hot jupiters do not show much sign of evaporating- so it is likely that an equilibrium can be reached with a hot gaseous atmosphere covering a hot rocky core...
the rate of spontaneous fusion might be higher in such a world, making it an honorary brown dwarf.
And Brown dwarfs last for a very long time, quietly fusing away for 60-100 billion years.
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eljubbo
PostPosted: 13-03-2003 16:58    Post subject: Reply with quote

You the man Eburacum45:D
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Anonymous
PostPosted: 12-04-2003 17:55    Post subject: planets Reply with quote

am i correct in thinking that the current veiw of the formation of our solar system is that the planets formed from debris orbiting around our sun
this being true why is the,IIRC van allen belt not forming into a planet or at least becoming lumpy,if the suns gravity is afecting it surly it would become lumpy at some point if the suns gravity isnt afecting it why isnt it drifting out into the void i would think that if the universe is expanding we would move away from these asteriods debris whatever they are.
why do they remain in orbit?
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Anonymous
PostPosted: 12-04-2003 19:00    Post subject: Reply with quote

The things in the asteroid belt are too cool to stick togetherany more, perhaps? Our planets were formed while everything was still hot, were they not?
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Anonymous
PostPosted: 12-04-2003 19:19    Post subject: Reply with quote

em pluto and the rest of the outer planets seemed to do ok
that still dosnt explain why they arnt drifting away or becoming lumpy
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Anonymous
PostPosted: 13-04-2003 10:45    Post subject: Reply with quote

The planets were supposedly formed by a process of accretion: 2 objects collide and the larger one goes away with a little more mass, collides again, gains more mass and so on.

When the solar system was first forming I assume all the bits that eventually formed into planets were scattered in a totally un-ordered manner and therefore these collisions were frequent. There were also, of course, many, many more objects out there than there are today.

Nowadays everthing is fixed in nice little orbits and despite sci-fi depictions of spacecraft dodging around asteroids, there's actually thousands of miles between them. So collisions are extremely rare and only likely to happen if a passing comet perturbs an object's orbit.

I think.
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Anonymous
PostPosted: 13-04-2003 12:21    Post subject: size Reply with quote

wouldnt two objects colliding just make lots of little objects scattering debis in all directions deminishing the size of the original two objects not somehow enlarging one of them this would only happen if a small object hit a large object with gravity to hold down the pieces
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DerekH16Offline
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PostPosted: 13-04-2003 12:51    Post subject: Reply with quote

Two objects, no matter their size, will stick together due to gravity if the 'collision' is soft enough. A violent collision would cause bits to fly off in all directions, but, given time, they will end up 'sticking' to other bits'n'pieces in similar orbits.

The asteroids don't get the chance to stick together because their orbits are always being affected by Jupiter.

The objects beyond the gas giant planets just don't meet up often enough to start accreting [sp?] - Pluto, although nominally a planet, is actually pretty small.

(PS Tin Finger: the occasional attempt at punctuation would make your posts more readable Very Happy )
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Anonymous
PostPosted: 13-04-2003 13:32    Post subject: Reply with quote

I was under the impression that the plantes formed while all this matter was still molten and whanging around the sun while it was a baby. Including the outer ones, unless they are magic planets of some description?

Pluto's just wobbling on the line that divides 'planets' from 'junk' anyway.
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caroleaswasOffline
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PostPosted: 13-04-2003 18:12    Post subject: Reply with quote

And how many planets are there in our solar system these days? Wasn't there talk of another planet beyond Pluto? Has it been officially recognised? What's its name?

Carole
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caroleaswasOffline
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PostPosted: 13-04-2003 22:02    Post subject: Reply with quote

If there's something bigger than Jupiter, surely it would have been detected by now?

Carole
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Anome_Offline
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PostPosted: 14-04-2003 07:22    Post subject: Reply with quote

Indeed. A brown dwarf could lurk out there, invisible amongst the comets and other debris. We would have to look for its pull on Pluto or other massive objects, which could be tricky to detect.

I believe the move to reclassify Pluto as a Kuiper Belt objecct was largely a beat up, and dropped fairly quickly after the backlash.

Still, they have identified an object of similar mass in the Kuiper belt.
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Anonymous
PostPosted: 18-05-2003 17:17    Post subject: Reply with quote

carole wrote:

If there's something bigger than Jupiter, surely it would have been detected by now?

Carole

they should have if there is anything nearby that large. Gravity bends light, any massive object would cause this. They have discovered several extrasolar planets, I think the count is past 100 so far, if they can detect them, I'm sure they'd have no problem finding large, nearby planets or objects. As for brown dwarfs, they don't exist yet. the oldest stars in the universe are still white dwarves, to have a brown dwarf would imply that the star is older than the universe and that can't be possible.
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