"Dumb all over, a little ugly on the side." -- Frank Zappa
"Your right to hold an opinion is not being contested. Your expectation that it be taken seriously is." -- Jason Thompson
"This is really very simple, but unfortunately it's very complicated." -- publius
Moderator comments in this color | Get moderator attention using the lower left icon:
Recommended reading: Board Rules * Forum FAQs * Conspiracy Theory Advice * Alternate Theory Advocates Advice
But let me try and work this out:
1. Brown dwarves = greater than 13 Jupiter masses by definition, and burn deuterium - hence, Brown dwarves are stars, not planets
2. An object orbiting a brown dwarf which is less than 13 Jupiter masses and does not burn deuterium is a planet.
An object fitting #3's description has indeed been discovered orbiting an object matching #1's description, so yes:
At least one planet has indeed been discovered orbiting a brown dwarf, which * is * a star according to the IAU definition. It defines an object 13 Jupiter masses or more, deuterium burning, as fitting the description of a star - as that is exactly what a brown dwarf is: between 13 mJ and Red Dwarf in mass, and burning deuterium but not hydrogen and helium.
They are not main-sequence stars but they are indeed stars, IMO and according to the IAU definition you laid out.
A brown dwarf masses between 13 Jupiter masses and 84 Jupiter masses.
Here's a few links on a few brown dwarfs that fit within that mass range.
Kelu 1 is no more than 75 Jupiter masses
Gliese 229 b is between 25 and 65 Jupiter masses
And here's a link on an abstract suggesting that the deuterium burning limit may be used to distinguish brown dwarfs from stars.
As the WGESP position statement says: "Rather than try to construct a detailed definition of a planet which is designed to cover all future possibilities, the WGESP has agreed to restrict itself to developing a working definition applicable to the cases where there already are claimed detections, e.g., the radial velocity surveys of companions to (mostly) solar-type stars, and the imaging surveys for free-floating objects in young star clusters. As new claims are made in the future, the WGESP will weigh their individual merits and circumstances, and will try to fit the new objects into the WGESP definition of a 'planet', revising this definition as necessary."
I assume frank discussion are now taking place!
I suspect something extra has to get the frog out of the pot. In my amateur opinion, I believe Fomalhaut b should be lifted to the proverbial pedestal since it is the first visible exoplanet imaged. This distinction isn't to minimalize the great efforts by others in imaging and infering the others, but I think Fomalhaut b should be given exceptional recognition for the good it should do for astronomy as a whole.
However, it wouldn't shock me if I am missing some points here. Y'all's views are important. I would like to be a part of something special in recognizing this discovery, even if it's just sending flowers or gift certificates to the Fb team.
If this idea has merit in your opinion, we might want to do a thread on what we as supporters can do to help in recognizing such an event.
We know time flies, we just can't see its wings.
I think you may be overestimating the general population. Remember Solid Bismuth's thread? Sadly, most people don't care, and probably won't care until the day a Vulcan drops in to dinner.
<Cynic mode off>
I like your idea of doing something to recognise this achievement George.
Hey, please keep "what is a planet" stuff out of this thread, this is about extrasolar planet discoveries.
PS. It's "dwarfs", not "dwarves". The latter can be found in Tolkien's books.
But, first I want to know if I'm off base on my thinking. From a landmark case perspective, Fomalhaut b may be the most interesting exoplanet to date simply because of the visible imaging (no so much the planet itself).
Either I'm right or wrong, what say thee?
[If I'm right, we can start a new thread. If nothing else, we can send a copy of a congrats thread of all our comments, but I'd love to see something more grand and commencerate to their milestone accomplishment. ]
We know time flies, we just can't see its wings.
And, that's the last thing I'll post about the definition of stars, since we were politely asked to knock if off.
I still disagree, though, with the definition of planets. I think it's more relevant the way an object was formed than what it orbits around. It's silly that you might have two gas giants, formed in exactly the same way, with almost exactly the same composition, with one being classed as a planet (because it orbits, say, a red dwarf) and the other not (because it orbits a brown dwarf). Would Earth suddenly stop being a planet if it were transported to an orbit around a brown dwarf? Would an object around a brown dwarf suddenly become a planet if it were captured a star?
I am a little perplexed though. Is there a reason why everyone is more excited about Fomalhaut b than the three planets around HR8799? Because I thought those images were fantastic. Is it the infrared/visible divide? Becuase that seems like wavelength elitism to me.
It's sort of like suddenly finding out something cool about two people, one an acquaintance, someone you've been sort of aware of for some time, who has a unique name, and who lives close by, and one a virtual stranger who lives a fair distance away and who's name is Bob Jones. It's just easier to be interested in the acquaintance.
Ah. Fair enough.
One of the most exciting things about the area of extrasolar planet research is that these objects throw our definitions of planet vs. star vs. brown dwarf into question.
Trying to find the best possible defintion of what each of those things actually is seems entirely relevant to the discussion of interesting extrasolar planet discoveries.
It probably does boil down to comparing HR8799's to Fomalhaut's exoplanet.
Pros for Fomalhaut b
1) It is the first confirmed directly imaged exoplanet in visible light. [Is it the first direct imaged exoplanet if we go back, since it was imaged in 2004 and I assume even then it was in visible light, right?] This first is unique from the rest and its too late to crank-up the band, I think, for an IR imaged exoplanet.
2) Warmer fuzzies with name familiarity vs. a number designation (as t@nn stated).
2b) "Fomalhaut" is kinda fun to say. [My 3 yr. old niece thought bread pudding made no sense as why make pudding from just bread. Then she said "bread pudding", smiled and said, "That's fun to say!".]
3) The host star is bright and easily visible to the naked eye with mag. of about 1. [HR8799 is not really visible to most naked eyes with its mag. of about 6.]
4) The actual image from Hubble is stunning. Though impressive, the HR8799 image looks like something out of CERN instead of from Keck, at least the few images I've seen.
I still pose the question, repharasing... "Should we wake-up the slumbering cheerleaders and get them to celebrate one of these discoveries, or must we wait till we discover a stargate or something?"
We know time flies, we just can't see its wings.
These discoveries please us, why care how or whether they are reported in the mass media?
Sorry to those who were offended by our little side discussion of when is an exoplanet an exoplanet.
Some papers relevant to the recent discoveries on arxiv today. MMT/AO 5 micron Imaging Constraints on the Existence of Giant Planets Orbiting Fomalhaut at ~13-40 AU constrains the existence of other planets in the Fomalhaut system: our results rule out the existence of planets with masses greater than 2 Jupiter masses, from ~13-40 AU and objects greater than 13 Jupiter masses from ~8-40 AU. The HZ of Formalhaut is about 4-6 AU. Direct Imaging of Multiple Planets Orbiting the Star HR 8799 details the imaging of the HR 8799 system, while A Resolved Ring of Debris Dust Around the Solar Analog HD 107146 describes the discovery of another dust disk with a hole in it, similar to the one that lead astronomers to look for planets around Fomalhaut and HR 8799. Their results may imply the presence of a planet at an orbital radius of ~45-75 AU.
Last edited by timb; 2008-Dec-07 at 09:42 AM. Reason: speling
Consider the frequent use of social words used by scientists George and t@nn (?) above. Fame, cool, acquaintance, warm fuzzies, niece, fun. Also look at the overwhelming popularity of the OTB and F&G fora on BAUT. And consider the fact that we're all scientists here. Even we're hugely interested in other people.
Like I said, I suspect it'll take a Vulcan dropping in for dinner, or maybe one featuring on page 3 of The Sun, to perk us up.
This is not a criticism- just an observation.
Oops, I think this is drifting off-topic again.
I am considering going back to university and doing astronomy, but it's a distant dream at the moment (high school was decades ago and I didn't do all science classes I needed to then, plus lack of funds is a big problem).
First of t@nn, our lives seem somewhat simular. Lack of money, been to collage and want to go back, if i understood you right
Hot enough to burn deterium The current definition is in terms of mass -- which determines density -- not temperature, which is also important in determining whether fusion occurs. By applying some formation model (the use of which the IAU generally rejects in definitions) astrophysicists conclude that a brown dwarf should get hot enough as well as dense enough at its core to support the fusion of deuterium early in its existence. A 13 MJ mass of primordial gas could conceivably form without getting that hot (eg some sort of slow accretion). It is also obvious that masses well below this can support deuterium fusion, if brought together with sufficient violence (that is the basis of terrestrial fusion research). Since whether a body briefly burns deuterium or not makes little difference to its evolution (in contrast, for example, to whether it burns protium), some astronomers question its appropriateness as a threshold.