Skip to comments.It Orbits a Star, but Does It Qualify for Planethood?
Posted on 04/05/2005 5:17:35 PM PDT by neverdem
Astronomers have produced what they say could be the first direct image of a planet around another Sun-like star. But the work has touched off intense debate about whether the orbiting object's mass has been determined accurately enough to count as a planet.
At issue is a reddish object that appears to be orbiting GQ Lup, a very young star about 450 light-years from here in the constellation Lupus. In marked contrast to other extrasolar planets that have been detected in recent years racing around in scorching proximity to their home stars, the new planet is 20 times as far from its star as Jupiter is from the Sun, about nine billion very cold miles, and probably takes 1,200 Earth years to complete a single orbit.
Being able to see and dissect the light from a distant object is the key to understanding what it is made of, how hot it is and how it relates to the worlds we know and love. But is the new object really a planet?
In a paper for the journal Astronomy and Astrophysics, posted on the Web last week, the discovery team, led by Dr. Ralph Neuhaeuser of Jena University in Germany, calculated that the object was about twice as massive as Jupiter but refrained from using the loaded word "planet," calling it a "companion." According to some theoretical models, it could be massive enough to be a brown dwarf, which is a kind of failed star.
If the preliminary estimate is anywhere near correct, the new planet will take its place as another landmark in an accelerating cavalcade of discoveries that have left astronomers fumbling for synonyms for "historic."
"It is the first planet shining to us from the sky of another system much like the first stars at dusk," said Dr. Günther Wuchterl, also of Jena.
In the last decade some 150 extrasolar planets have been detected indirectly, and astronomers have been racing for the first direct views of them. Last year a team from the European Southern Observatory reported spotting an object of five Jupiter masses near a brown dwarf in Hydra, but it has not yet been confirmed to be orbiting the dim star. The team says it will report new results soon.
Last month a team using the Spitzer Space Telescope discerned the heat radiation from a Jupiter-mass planet in the blended light of the planet and its star, but did not get a separate image of the planet.
In this case, Dr. Neuhaeuser wrote in a vastly understated e-mail message, "We do have a normal plain image showing the bright star and the faint planet a little bit west of the star."
He and his team had been searching for planets around GQ Lup since 1999. The star is part of a cluster of very young stars, only a million or so years old, so young that whatever planetary progeny they may have created are still forming, giving off excess heat and making them easier to see. That proved to be the case; GQ Lup is only 156 times as bright as the planet.
Dr. Neuhaeuser's group spotted it last year using the European Southern Observatory's Very Large Telescope in Chile and a special camera designed to eliminate atmospheric blurring. They have been tracking it ever since. Later, they were able to discern the planet in previous images, including one from the Hubble Space Telescope in 1999.
From infrared measurements, they infer that the planet is still very hot, about 3,000 degrees Fahrenheit, with water and carbon monoxide in its atmosphere.
"This is a beautiful piece of science," said Dr. Ben Oppenheimer of the American Museum of Natural History and a fellow planet hunter.
Many astronomers, however, urged caution. Besides questions over the mass of the planet, its orbit, so far from its star, presents a challenge to theorists.
A renowned discoverer of planets, Dr. Geoffrey W. Marcy of the University of California, Berkeley, said the uncertain mass and the enormous orbit of the planet were "both cause for puzzlement."
But Dr. Alan Boss, of the Carnegie Institution of Washington, said that even if the models were off by a factor of two or three, the mass of the GQ Lup object would still be comfortably below the cutoff - 13 Jupiters - between planets and brown dwarfs.
He said he thought that the group had done its homework and that it was possible that in the end all the caveats would be met and, as he put it, "Bingo, they've finally gotten what we've all been looking for."
In an e-mail message, Dr. Wuchterl pointed out that the calculations of mass had been buttressed by spectroscopic measurements of the planet's gravitational field, which were consistent with a mass of one or two Jupiters, confirming its likely planethood.
He said the new results indicated that planet formation could be very fast, and they plan to look for more planets around GQ Lup.
"In the last century a bridge of knowledge has been built between the stars and the Sun," Dr. Wuchterl wrote. "That puts our star into context. We will try to do that for the planets. And we got some light now for that purpose."
European Southern Observatory
A Sun-like star (A), called GQ Lupi, is orbited by an object (b) that may be a planet.
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I thought this was going to be a thread about Rosie O'Donnell running laps around Michael Moore.
Thanks. We just had a thread on estra-solar planets, and it didn't get much action, so I think I'll hold off for now on pinging my list for this one.
Bump for later
I suggest we ask the Supreme Court!
If it's inner truth is that it sees itself as a planet, then it is a planet and should be given all the civil rights protection that it's due.
I don't know, but I'll lose a lot of sleep over this. What if the reddish object circling GQ Lup is only a brown dwarf and not an newbie star?! Another MTV commercial?
Hey, I still wonder happened to the planet that used to be between Mars and Jupiter and is now the asteroid belt, and that was a LOT closer to home.
Something like that happened in Star Wars (now Part 4) where the Princess Layla's home planet (whatever Cowpie Ears' planet was named) was zapped by the Death Star.
This could be serious...
This could be serious.
Now my beater is stoned!
That is worse than the Mons that lit my spinster.