And I tell people that, when the subject of the Fomalhaut discovery comes up, and they just glaze over. The number of people that are actually fascinated by these discoveries seems to be somewhat low.. or interested, even.Originally Posted by t@nn
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And I tell people that, when the subject of the Fomalhaut discovery comes up, and they just glaze over. The number of people that are actually fascinated by these discoveries seems to be somewhat low.. or interested, even.
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Established Member
Don't know how you came to this conclusion.
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.
Established Member
Do you have a reference for that claim? It contradicts the IAU working definition.
Established Member
Here's one. It's an Internet encyclopedia, but I've seen the same conclusions in many other places on the Internet.
http://www.daviddarling.info/encyclo...rowndwarf.html
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
http://www.eso.org/public/outreach/p.../pr-07-97.html
Gliese 229 b is between 25 and 65 Jupiter masses
http://www.solstation.com/stars/gl229.htm
And here's a link on an abstract suggesting that the deuterium burning limit may be used to distinguish brown dwarfs from stars.
http://gpd.jhuapl.edu/abstracts/abst...d_abstract.pdf
Member
I'm afraid you're reading it incorrectly - it is not an exhaustive definition for extrasolar planets. It says that planetary-mass objects orbiting stars are planets, but does not say that only such objects are planets.
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!
Order of Kilopi
This seems to be the case. I believe there is much more opportunity here to make this a big story, but it's not happening. Perhaps this is another frog in the pot analogy. Over the last decade there have been over 300 discoveries of exoplanets. Fomalhaut b is not the first to be imaged, either, and when it was announced, along came the announcment of three planets imaged, as we know. All of these points has kept the frog leaping up and getting everyone's attention.
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.
Order of Kilopi
<Cynic mode on>
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.
Established Member
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.
Established Member
What does that mean?
Established Member
I don't see the relevance of anything you have posted above to the question of whether objects orbiting brown dwarves are planets.
Order of Kilopi
Agreed, and their apothy is apparent. But, I am not talking of them so much as us -- the ones that really respect what astronomers accomplish. What can we do to express honor?
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. ]
Established Member
Sorry, I misunderstood. I thought you were saying that the definition said that anything over 13 Jupiter masses and burning deuterium was classified, by the definition as being a star. In my own defence, I was suffering from lack of sleep at the time I posted all those links.
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?
Order of Kilopi
You're not wrong George.
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.
Established Member
My guess is partly due to the fame of the star in question and partly because of the distance. Fomalhaut is much better known, and it has a proper name and not a bunch of letters and numbers. I imagine a lot of people hadn't even heard of HR 8799 before this news broke and it has a designation virtually identical to a lot of other stars out there. Fomalhaut is also much closer, being only 25 light years away, as opposed to Hr 8799's 129 light years.You're not wrong George.
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.
Order of Kilopi
Ah. Fair enough.
Established Member
I'm not sure why you are objecting.
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.
Order of Kilopi
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?"
Established Member
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.
Established Member
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
Order of Kilopi
These are great, thanks timb.
It might even take more than a stargate I'm afraid. People like to talk, and most of all, they like to talk about other people.
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.
Established Member
Well we can talk to each other. Fame and warm fuzzies may be nice, but what do you think will happen to the forum if The Sun page three crowd start taking an interest?
I was never a fan, but I imagine the Vulcans would be too flat chested to make page 3. Are they good at sports? The back page probably has the most readers, after page 3.
Oops, I think this is drifting off-topic again.
Established Member
Thanks for the compliment, but I'm not a scientist, just someone who keeps up-to-date with astronomy through popular science books, websites, and magazines.
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.
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).
Established Member
I'd like to keep this thread only for announcing new exciting discoveries. Discussions about taxonomy can be done elsewhere, they tend to expand quickly.
Established Member
Two-planet system around HD 191760 consisting of a hot Jupiter + eccentric super-Jovian.
Established Member
The planet of Beta Pictoris finally imaged? BA has more.
Established Member
Neat. It's a bit funny, mind, how the image is IIUC from 2003 and they choose to publish right now after the Fomalhaut and HR 8799 announcements.
Established Member
I didn't think that was exciting enough to announce. The inner planet is about the mass of Saturn, well sub-Jovian. They're both hot, or hot and very hot.
Established Member
Will there be no end to first images of exoplanets?
Established Member
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
My personal favorite on how to define a star is that it has to be hot enough to burn deterium. And yes, i consider a celestrial body orbiting a brown dwarf (hot enough to burn deterium) a planet and a body oribiting a 12,9 M_jup a moon since this 'planet' probably isn't hot enough to burn deterium. If a 'moon' is captured by a star i would say it is now a planet. Of course things can change - Is a thing the size a stone a planet since it orbits the star and is former in a way that everything hammering into it is smaller than itself - and when it has grow big enough astroids are hammering into it. All the time this stone was the biggest of the two hammering into each other, but was it consider a planet in the first place? Nope, it changed once it has 'cleaned up it neighbourhood' as the IAU defined not long ago. But what is wrong about a moon changing into a planet after finding a new thing to orbit? Are moons not as interesting as planets sometimes? I don't know if it is just me, but Titan is more interesting to me than Mercury, not to say Mercury is boring, but still...
Established Member
Perhaps the posts related to definitional issues could be removed to another thread? For the sake of continuity I will continue to reply to posts on that theme here.
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.
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