Print from Airliners.net discussion forum
http://www.airliners.net/aviation-forums/non_aviation/read.main/2423222/

Topic: Brown Dwarf Stars, What Would You Call Them?
Username: 2707200X
Posted 2012-05-08 22:55:28 and read 1175 times.

By now, most of us know have herd of brown dwarfs. From what we know, brown dwarfs fill the gap between the largest or most massive of the gas planets and the smallest or least massive of the "M-class" red dwarf stars. The mas varies between 90 times the mass of Jupiter and 10 times the mass of Jupiter. Like stars they glow "dimly" and they are orbited by planets but like planets, they have no fusion in the core. NASA's WISE mission has discovered over 100 brown dwarfs.

What do you think about the brown dwarfs and what would call these stars?

Topic: RE: Brown Dwarf Stars, What Would You Call Them?
Username: Mir
Posted 2012-05-08 23:16:35 and read 1167 times.

Is something wrong with "brown dwarf stars"?   

I'm kind of on the "if it's not broken, don't fix it" bandwagon here....

-Mir

Topic: RE: Brown Dwarf Stars, What Would You Call Them?
Username: seb146
Posted 2012-05-08 23:40:59 and read 1156 times.

Quoting 2707200X (Thread starter):
"M-class"
Quoting 2707200X (Thread starter):
red dwarf

I thought M-Class were planets most close to Earth and red dwarf was a mining ship...

Topic: RE: Brown Dwarf Stars, What Would You Call Them?
Username: connies4ever
Posted 2012-05-09 00:54:20 and read 1141 times.

Quoting Mir (Reply 1):
Is something wrong with "brown dwarf stars"?
Quoting seb146 (Reply 2):
I thought M-Class were planets most close to Earth and red dwarf was a mining ship...

Yes, M-class planets are the rocky ones like Earth (Venus, Mercury, Mars). The rest are gas giants except for Pluto which looks like it might be a comet that wandered in from the Kuiper belt and got trapped. Interestingly, Pluto itself has a satellite system (Charon, Nix, Hydra, and the dramatically named S1/2011).

Charon is larger in proportion to it's primary than any satellite in the Solar System.

There are still more hunks of ice/rock further out: Quaoar, Eris, and Santa to name a few. Many more will be discovered, of that I am quite sure. Be frickin' cold out there, that's for sure. And dark:the Sun wouLd be a mere point at 40-60 AU.

Topic: RE: Brown Dwarf Stars, What Would You Call Them?
Username: vikkyvik
Posted 2012-05-09 01:11:18 and read 1126 times.

Quoting 2707200X (Thread starter):
What do you think about the brown dwarfs and what would call these stars?

I typically call them brown dwarfs....

Quoting connies4ever (Reply 3):
Quoting seb146 (Reply 2):
I thought M-Class were planets most close to Earth and red dwarf was a mining ship...

Yes, M-class planets are the rocky ones like Earth (Venus, Mercury, Mars). The rest are gas giants except for Pluto which looks like it might be a comet that wandered in from the Kuiper belt and got trapped. Interestingly, Pluto itself has a satellite system (Charon, Nix, Hydra, and the dramatically named S1/2011).

You may have missed the joke there....

Topic: RE: Brown Dwarf Stars, What Would You Call Them?
Username: Aesma
Posted 2012-05-09 02:33:44 and read 1095 times.

Apparently they were called black dwarfs at one point, and other name contenders are planetar and substar.

Topic: RE: Brown Dwarf Stars, What Would You Call Them?
Username: connies4ever
Posted 2012-05-09 03:23:34 and read 1087 times.

Quoting vikkyvik (Reply 4):
Quoting connies4ever (Reply 3):
Quoting seb146 (Reply 2):
I thought M-Class were planets most close to Earth and red dwarf was a mining ship...

Yes, M-class planets are the rocky ones like Earth (Venus, Mercury, Mars). The rest are gas giants except for Pluto which looks like it might be a comet that wandered in from the Kuiper belt and got trapped. Interestingly, Pluto itself has a satellite system (Charon, Nix, Hydra, and the dramatically named S1/2011).

You may have missed the joke there....

Not really, I got the joke. Here's a joke: Santa has been determined to have it''s own satellite, informally called Rudolph. Both names I believe still have not been offically adopted by the IAU.

Topic: RE: Brown Dwarf Stars, What Would You Call Them?
Username: Aloha717200
Posted 2012-05-09 10:36:48 and read 1022 times.

Quoting connies4ever (Reply 3):
Pluto which looks like it might be a comet

I don't know if a body large enough to have achieved hydro-static equilibrium can still be considered a "comet". It'll be interesting once New Horizons reaches pluto and gives us a better understanding of its true composition versus what we can infer from telescope imagery.

As for brown dwarfs...the name seems to work for me. It'd be interesting to find one that's a mere 1 jupiter mass away from becoming a star.

Topic: RE: Brown Dwarf Stars, What Would You Call Them?
Username: connies4ever
Posted 2012-05-09 11:10:49 and read 1014 times.

Quoting Aloha717200 (Reply 7):
I don't know if a body large enough to have achieved hydro-static equilibrium can still be considered a "comet". It'll be interesting once New Horizons reaches pluto and gives us a better understanding of its true composition versus what we can infer from telescope imagery.

Yes it will be fascinating to see what New Horizons discovers. 3 years to go now. As for hydrostatic equilibrium, not forget that smaller objects such as the asteroids Ceres and Vesta (more or less) have done so, as has the Moon and several satelllites of the gas giants.

Quoting Aloha717200 (Reply 7):
As for brown dwarfs...the name seems to work for me. It'd be interesting to find one that's a mere 1 jupiter mass away from becoming a star.

Jupiter is already almost a brown dwarf. It radiates at radio frequency.

Topic: RE: Brown Dwarf Stars, What Would You Call Them?
Username: GrahamHill
Posted 2012-05-09 11:31:38 and read 1009 times.

Quoting Mir (Reply 1):
Is something wrong with "brown dwarf stars"?

Absolutely not!

Quoting connies4ever (Reply 8):
As for hydrostatic equilibrium, not forget that smaller objects such as the asteroids Ceres and Vesta (more or less) have done so, as has the Moon and several satelllites of the gas giants.

But what is the parameter for a small object to be called dwarf planet or asteroid? To me, Ceres and Pluto are dwarf planets because, on top of gravitating around the sun, they could achieve hydrostatic equilibrium. But since Vesta has not achieved hydrostatic equilibrium, I can't really call it a dwarf planet.

Am I wrong?

Topic: RE: Brown Dwarf Stars, What Would You Call Them?
Username: Aloha717200
Posted 2012-05-09 11:36:48 and read 1008 times.

Quoting connies4ever (Reply 8):
smaller objects such as the asteroids Ceres and Vesta (more or less) have done so, as has the Moon and several satelllites of the gas giants.

I believe that Ceres is now classified as a Dwarf Planet, wheras Vesta is still considered an asteroid. The difference, it appears, lies in the hydrostatic equillibrium. Vesta just about got there, Ceres got all the way there. But I believe that composition plays a big role in whether a body qualifies as a comet. If Ceres was a ball of ice and managed to get close enough to the sun to develop a tail, I bet it could be considered a comet. But Ceres is quite a bit smaller than Pluto. I wouldn't think that Pluto would technically qualify.

But. Semantics.

Topic: RE: Brown Dwarf Stars, What Would You Call Them?
Username: DarkSnowyNight
Posted 2012-05-09 12:02:21 and read 990 times.

Quoting connies4ever (Reply 8):
as has the Moon and several satelllites of the gas giants.

The moon would be a planet of not for its orbiting of ours. The same can be said for Titan and a few others.

Quoting connies4ever (Reply 8):
Jupiter is already almost a brown dwarf. It radiates at radio frequency.

Jupiter is less than ten percent the size a body needs to be to be classified as a dwarf star of any kind. I think it's a myth to say it was "almost a star." Several exo-planets have also been discovered that a quite larger than Jupiter and still not stars either.

Topic: RE: Brown Dwarf Stars, What Would You Call Them?
Username: 2707200X
Posted 2012-05-09 13:13:07 and read 970 times.

I have no problem with calling brown dwarf stars brown dwarfs, I actually like that term. One thing is fore sure, the spacing between the what makes a large gaseous planets and and the smallest of sub-brown dwarfs is almost nil if even that. Look at TrES-4b it's diameter, twice as wide as Jupiter clearly exceeds Gliese 229b which is about the same size as Jupiter and look at WISE 1828+2650, only 300K or 80F and Venus is how much? The defining factor is of course mass when determining what makes a planet and a star. We know that physics tells us that red dwarf star Ross 154 will never be a red giant, the Sun will never end up as a black hole but nature is not going to stop a 8, 10, 12 or 17 Jupiter mass body from forming. That's really the mystery and fun of Astronomy in all of this.

Topic: RE: Brown Dwarf Stars, What Would You Call Them?
Username: connies4ever
Posted 2012-05-09 15:37:31 and read 948 times.

Quoting GrahamHill (Reply 9):
But what is the parameter for a small object to be called dwarf planet or asteroid? To me, Ceres and Pluto are dwarf planets because, on top of gravitating around the sun, they could achieve hydrostatic equilibrium. But since Vesta has not achieved hydrostatic equilibrium, I can't really call it a dwarf planet.

Am I wrong?

Not really, but Vesta's unusual shape more likely comes from a catastrophic collision with another asteroid millions of years ago, not inability to achieve equilibrium. Don't know if you''ve seen any photos from Dawn, currently orbiting Vesta, but the scar on that body is HUGE (and deep).

http://dawn.jpl.nasa.gov/multimedia/images/PIA15602-700.jpg
http://dawn.jpl.nasa.gov/multimedia/images/632419main_pia15493-700.jpg
http://dawn.jpl.nasa.gov/multimedia/images/RC3_color_05-full.jpg (looks reasonably spherical)

Quoting Aloha717200 (Reply 10):
I believe that Ceres is now classified as a Dwarf Planet, wheras Vesta is still considered an asteroid.

Correct to my knowledge, but...
http://en.wikipedia.org/wiki/Dwarf_p....22nearly_certain.22_dwarf_planets

Quoting DarkSnowyNight (Reply 11):
The moon would be a planet of not for its orbiting of ours. The same can be said for Titan and a few others.

Some have called Earth-Moon a twin planet. The Moon doesn't exactly orbit the Earth, the two bodies rotate around the centre of mass of the joint system. Which is below the Earth's surface, but not that far, and definitely not at the geometric centre. Titan and others do orbit because of the huge mass disparity between the secondary and the primary. The centre of mass for Saturn-Titan or Jupiter-Ganymede is not far from the geometric centre.

Quoting DarkSnowyNight (Reply 11):
Jupiter is less than ten percent the size a body needs to be to be classified as a dwarf star of any kind. I think it's a myth to say it was "almost a star."

Topic: RE: Brown Dwarf Stars, What Would You Call Them?
Username: DocLightning
Posted 2012-05-09 17:59:46 and read 918 times.

Quoting Mir (Reply 1):
Is something wrong with "brown dwarf stars"?

Yes. Stars have nuclear fusion at their cores. Brown Dwarfs do not. I think simpy "Brown Dwarfs" is sufficient.

Topic: RE: Brown Dwarf Stars, What Would You Call Them?
Username: flyboyseven
Posted 2012-05-09 18:51:16 and read 905 times.

Quoting DarkSnowyNight (Reply 11):
The moon would be a planet of not for its orbiting of ours. The same can be said for Titan and a few others.

The moon would only be a planet if it satisfied the three criteria for being a planet. The first is to be massive enough to form into a spheroid which it has satisfied. The other two are that it has to orbit the sun, and that it must have cleared out its orbit around the sun.

If there were no earth, then it would satisfy the second also, but it would fail on the third count. It would be kicked out for the same reason that pluto was. Its gravity would not be enough to clear out its orbit out debris.

Quoting connies4ever (Reply 13):
Some have called Earth-Moon a twin planet. The Moon doesn't exactly orbit the Earth, the two bodies rotate around the centre of mass of the joint system. Which is below the Earth's surface, but not that far, and definitely not at the geometric centre. Titan and others do orbit because of the huge mass disparity between the secondary and the primary. The centre of mass for Saturn-Titan or Jupiter-Ganymede is not far from the geometric centre.

While it is true that the earth and moon orbit around the systems center of mass, and that it happens to be just inside the earths surface, the same is true of all orbiting bodies. On the larger planets it is just a lot less apparent, but the same thing is going on. The earth and all the the other planets have the same relationship with the sun, as do other planets around other stars. This effect is actually one of the leading ways of discovering exo-planets. You can see the spectra of the star show small variations in its red or blue shift and that can tell you about the planets orbiting them.

The reason the earth moon system is dubbed a twin planet is because the relative size of the moon is so great. The same is not true of its mass however which is several orders of magnitude below that of the earth.

Quoting 2707200X (Thread starter):
What do you think about the brown dwarfs and what would call these stars?

I would simply call them brown dwarfs for simplicity, but they are not stars per-se. They occupy the grey area between star and planet, and are not really one or the other. Given that the first brown dwarf to be verified as such was in 1995, there is a lot more study needed to fully figure out what they are, and how exactly to define them. It was not until 2006 that there was a formal definition for a planet, so don't hold your breath for one about brown dwarfs!

Cheers!

Graham

Topic: RE: Brown Dwarf Stars, What Would You Call Them?
Username: prebennorholm
Posted 2012-05-09 19:03:13 and read 902 times.

Quoting DocLightning (Reply 14):
Stars have nuclear fusion at their cores. Brown Dwarfs do not.

That's not entirely true. They have, however, no hydrogen fusion.

Brown Dwarfs greater than roughly 13 Jupiter masses have deuterium fusion. If greater than some 65 Jupiter masses they have lithium fusion as well.

Real main sequence stars all have hydrogen fusion. The minimum size for hydrogen fusion is normally considered to be 75-80 Jupiter masses. The upper limit varies with the lithium contents. The more lithium, the more a brown dwarf "balloons", and the more mass is needed to reach the critical core pressure to start hydrogen fusion.

Due to the always low deuterium (and lithium) contents compared to hydrogen, and due to the lower mass, the energy creation in a brown dwarf is extremely low compared to a hydrogen burning star.

Topic: RE: Brown Dwarf Stars, What Would You Call Them?
Username: connies4ever
Posted 2012-05-09 20:52:04 and read 888 times.

Quoting flyboyseven (Reply 15):
While it is true that the earth and moon orbit around the systems center of mass, and that it happens to be just inside the earths surface, the same is true of all orbiting bodies. On the larger planets it is just a lot less apparent, but the same thing is going on.
Quoting flyboyseven (Reply 15):
The reason the earth moon system is dubbed a twin planet is because the relative size of the moon is so great. The same is not true of its mass however which is several orders of magnitude below that of the earth.

I believe I said that. Perhaps not clearly enough. Lunar volume is about 1/64-th of the Earth (I think, but it's late), density is lower, so a rough mass estimate is about 1% of the Earth, or perhaps a little less. I'm sure you can look it up.

Quoting prebennorholm (Reply 16):
Brown Dwarfs greater than roughly 13 Jupiter masses have deuterium fusion. If greater than some 65 Jupiter masses they have lithium fusion as well.

Indeed. Jupiter's emissions of radio noise doesn't have a nuclear source, it's magnetic:
http://science.nasa.gov/science-news...ce-at-nasa/2004/20feb_radiostorms/

Topic: RE: Brown Dwarf Stars, What Would You Call Them?
Username: DarkSnowyNight
Posted 2012-05-09 21:47:08 and read 873 times.

Quoting connies4ever (Reply 13):
The Moon doesn't exactly orbit the Earth, the two bodies rotate around the centre of mass of the joint system. Which is below the Earth's surface,

About 1700km into the Earth IIRC, yes. But I don't think that makes us co-orbital with it. This brings a question then of what is needed for it to be considered to orbit in the truest sense. I've always been satisfied that this means that center of mass is below the surface of the larger (by mass), inner body.

As for the others I mentioned, I was really going by all-up mass rather than positioning and orbit. Since they have hydrostatic equalibrium, their size would class them as planets were they on track without any others and not orbiting (or co-orbiting) any other.

Quoting flyboyseven (Reply 15):
Its gravity would not be enough to clear out its orbit out debris.

Depends on what you mean by debris, but at its mass, it is more than sufficient to clear out anything that Mercury could. If we were talking about being placed in the Asteroid Belt or somewhere in the Oort cloud, there may be enough Ceres sized objects to pose a problem, but here it's hard to fathom something that the moon couldn't clear out without dramatically altering its own orbital mechanics.

Topic: RE: Brown Dwarf Stars, What Would You Call Them?
Username: connies4ever
Posted 2012-05-10 00:19:14 and read 857 times.

Many of you may appreciate this link for possibilities beyond Pluto: going all the way out to the Kuiper Belt:

http://www.spacedaily.com/reports/Be...Exploring_the_Kuiper_Belt_999.html

Topic: RE: Brown Dwarf Stars, What Would You Call Them?
Username: KaiGywer
Posted 2012-05-10 03:07:18 and read 830 times.

Please tell me I wasn't the only one that didn't think of anything to do with space when I saw the thread title.....   

Topic: RE: Brown Dwarf Stars, What Would You Call Them?
Username: connies4ever
Posted 2012-05-17 07:48:18 and read 647 times.

Quoting connies4ever (Reply 13):
Not really, but Vesta's unusual shape more likely comes from a catastrophic collision with another asteroid millions of years ago, not inability to achieve equilibrium. Don't know if you''ve seen any photos from Dawn, currently orbiting Vesta, but the scar on that body is HUGE (and deep).

A little bit more about Vesta, an interesting discovery courtesy Dawn:

http://www.aviationnow.com/Article.a...l/asd_05_17_2012_p04-02-458339.xml

So it appears as though Vesta had a molten core at one point. And that there were two, not one, massive collisions that caused the South Pole crater to be formed.

The Dawn mission, hopefully, will continue for some time. Supposed to leave Vesta in August for Ceres, perhaps this can be extended to another body like Eros, which is definitely not a protoplanet.

Topic: RE: Brown Dwarf Stars, What Would You Call Them?
Username: N1120A
Posted 2012-05-17 14:52:51 and read 612 times.

Quoting connies4ever (Reply 3):
The rest are gas giants except for Pluto which looks like it might be a comet that wandered in from the Kuiper belt and got trapped. Interestingly, Pluto itself has a satellite system (Charon, Nix, Hydra, and the dramatically named S1/2011).

Pluto is a planet, damn it!  

Topic: RE: Brown Dwarf Stars, What Would You Call Them?
Username: tugger
Posted 2012-05-17 15:01:48 and read 609 times.

Quoting 2707200X (Thread starter):
Brown Dwarf Stars, What Would You Call Them?

How about "Hispanic (or Latino) little-people entertainers"?

Quoting KaiGywer (Reply 20):
Please tell me I wasn't the only one that didn't think of anything to do with space when I saw the thread title.....

Nope you weren't..... 

Tugg

Topic: RE: Brown Dwarf Stars, What Would You Call Them?
Username: connies4ever
Posted 2012-05-17 16:00:41 and read 603 times.

Quoting N1120A (Reply 22):
Pluto is a planet, damn it!

   With you on that one, bro. I was totally against the decision by the IAU. Pluto was initially identified as a planet. Even if it does not meet the (new) criteria, I believe it should be grandfathered.

The size and characteristics of some of the recently-discovered dwarf planets is interesting, though. Eris, for example, seems to be larger than Pluto, and probably more massive. But it is really a long way out, about 67 AU, with a period of ~550 yrs. Not a KBO, but seems to be part of the original accretion disc that formed around the Sun.

There is talk of extending New Horizons beyond Pluto/Charon (see Reply 19). The question uppermost is which one to aim for ? Which depends on orbital characteristics, fuel on board, etc. Not sure if Eris could be reached, particularly due to it's extreme orbital inclination, but since it is really "out there", it would be interesting on that basis alone.


The messages in this discussion express the views of the author of the message, not necessarily the views of Airliners.net or any entity associated with Airliners.net.

Copyright © Lundgren Aerospace. All rights reserved.
http://www.airliners.net/