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ToSeek
2004-May-27, 05:17 PM
Heaviest Stars are Twins (http://www.universetoday.com/am/publish/heaviest_stars_twins.html?2652004)


Astronomers with the Harvard-Smithsonian Center for Astrophysics have found the heaviest star ever seen - 80 times the mass of our Sun - and it's got a twin. Located 20,000 light-years from Earth, the two massive stars in WR 20a go around each other every 3.7 days. These two stars are very young, probably only 2-3 million years old, and highly unstable. It'll only be a few more million years before they explode, one after the other as supernovas.

Kullat Nunu
2004-May-27, 05:54 PM
Astronomers with the Harvard-Smithsonian Center for Astrophysics have found the heaviest star ever seen - 80 times the mass of our Sun - and it's got a twin. Located 20,000 light-years from Earth, the two massive stars in WR 20a go around each other every 3.7 days. These two stars are very young, probably only 2-3 million years old, and highly unstable. It'll only be a few more million years before they explode, one after the other as supernovas.

Should be heaviest stars ever measured. There are several star that are tought to be more massive than these.

cyswxman
2004-May-27, 06:01 PM
Are they unstable because of their close proximity to each other, or just individually unstable?

Dgennero
2004-May-27, 06:12 PM
The intrinsically brightest and most massive star I know is Eta Carinae ( http://www.seds.org/messier/xtra/ngc/etacar.html ) - not a binary AFAIK, but with 100 to 150 solar masses.
It is unstable due to its sheer size.
Can you top that one? 8)

Kullat Nunu
2004-May-27, 07:23 PM
The intrinsically brightest and most massive star I know is Eta Carinae ( http://www.seds.org/messier/xtra/ngc/etacar.html ) - not a binary AFAIK, but with 100 to 150 solar masses.
It is unstable due to its sheer size.
Can you top that one? 8)

The Pistol Star and LBV 1806-20 may be more massive.

Pistol Star may have weighted during its birth over 200 solar masses, but these stars are extremely unstable and quickly lose much of their mass. It has been calculated that Eta Carinae will vanish in a few hundred thousand years just by stellar wind. But of course it will explode as a supernova (or hypernova) before that.

Ut
2004-May-27, 07:26 PM
The intrinsically brightest and most massive star I know is Eta Carinae ( http://www.seds.org/messier/xtra/ngc/etacar.html ) - not a binary AFAIK, but with 100 to 150 solar masses.
It is unstable due to its sheer size.
Can you top that one? 8)

IIRC, the current thinking is that Eta Carinae is a binary system. It seems to be one of the simpler theories for creating the bipolar lobes.

Kullat Nunu
2004-May-27, 07:43 PM
IIRC, the current thinking is that Eta Carinae is a binary system. It seems to be one of the simpler theories for creating the bipolar lobes.

Maybe, maybe not...

Not a long ago the VLTI studied (http://www.eso.org/outreach/press-rel/pr-2003/pr-31-03.html) Eta Carinae and it was found to be very oblate in shape. Its rotational speed was measured to be over 90% of breakup speed. The bipolar lobes originate from the star's polar regions which are much hotter than equator, because they are closer to the core. So stellar winds are more powerful in polar regions than in the equator.

Dgennero
2004-May-27, 08:12 PM
It's a tossup.
LBV 1806-20 http://www.nojum.net/news/newse.asp?newsid=24 is a candidate (as is the pistol star) , but Eta Carinae is listed with 150 solar masses avg. NOW on the websites I visited, and said to have started at at least 200, losing a lot of mass due to instability.

Kaptain K
2004-May-27, 10:35 PM
IIRC - The maximum mass of a star is composition dependent. The more metal rich, the lower the maximum mass. I seem to remember seeing speculation that in the very early universe, when the composition was almost pure H and He, that the maximum may have been closer to 1000 (!!) MS.

Bob
2004-May-27, 11:18 PM
HD 93250? 120 solar masses

http://www.space.com/reference/brit/stars/structure.html

Ilya
2004-Jun-01, 02:32 AM
Are they unstable because of their close proximity to each other, or just individually unstable?

Individually unstable. Stars that big go blowyee whether they are in a binary system or not.

Argos
2004-Jun-01, 02:38 PM
These two stars are very young, probably only 2-3 million years old, and highly unstable. It'll only be a few more million years before they explode

Given their age and their mass, I would say they are exploding right now. In 20,000 years our descendants will see this explosion and the formation of the two black holes that will result.

invinible
2005-Feb-13, 08:42 PM
How much does HD 93250 wiegh in tonnes?

Hamlet
2005-Feb-13, 09:26 PM
How much does HD 93250 wiegh in tonnes?

HD 93250 is thought to have about 120 solar masses.

A solar mass is about 1.989E30 kg, so a 120 solar mass star is about 2.387E32 kg.

Converting this to tonnes gives: 2.387E29 tonnes.

asgromo
2005-Feb-14, 04:12 AM
Ah, but which one makes a better picture, hmm?

http://imgsrc.hubblesite.org/hu/db/1996/23/images/a/formats/web.jpg

(That's Eta Carinae, by the way, compliments of the Hubble.)

Brady Yoon
2005-Feb-14, 06:28 PM
IIRC - The maximum mass of a star is composition dependent. The more metal rich, the lower the maximum mass. I seem to remember seeing speculation that in the very early universe, when the composition was almost pure H and He, that the maximum may have been closer to 1000 (!!) MS.

Yeah me too. Because metals only make up a small part of stars, tiny changes in metal concentration must really affect how massive a star can get.

I wonder how luminous those 1000 solar mass stars were...

Jorge
2005-Feb-14, 09:42 PM
I wonder how luminous those 1000 solar mass stars were...

No idea but i'd imagin something as super nova?(just guessing)

Bob
2005-Feb-15, 12:39 AM
[quote="Brady YoonI wonder how luminous those 1000 solar mass stars were...[/quote]

The luminosity of a main sequence star varies roughly as the third or fourth power of its mass. That would mean that a 1000 solar mass star would have 10^^9 times the sun's luminosity, if that power law relationship is still valid for such an unusual hypothetical star.

jaeger
2005-Feb-15, 12:52 AM
If Eta Carinae went Supernova, what would its magitude be as seen from Earth?

Brady Yoon
2005-Feb-15, 01:41 AM
A supernova has an absolute magnitude of -19. This is how bright the supernova would appear at 10 pc. Because Eta Carinae is 10,000 ly away, or 3070 pc away (10,000/3.26), it would appear 95,000 times dimmer due to the inverse square law. 95,000 times dimmer corresponds to a magnitude change of 12. So it would be around apparent magnitude -7. Much brighter than Venus and close to a crescent moon.

However, Eta Carinae is a star that is massive enough to go hypernova, which can be up to 100 times more powerful than a standard type 1a supernova. 100 times brighter corresponds to 5 magnitudes, so then it would be magnitude -12. As bright as the full moon.

These calculations are probably a little off.

Whatever happens, it will be an awesome sight. An object 5,000 light years away as bright as the moon. Now that's cool. :D

Kaptain K
2005-Feb-15, 10:01 AM
Whatever happens, it will be an awesome sight. An object 5,000 light years away as bright as the moon. Now that's cool.
...and dangerous! Remember, not all (or even most) of a supernova's radiation is in the visible spectrum!

Manchurian Taikonaut
2005-Feb-15, 10:33 AM
its great that they can measure such a massive star

About this Eta Carinae, some say it was 150 times as massive as our Sun and was shown in the Hubble Space Telescope image but it is likely to actually be a system of two stars, as for largest stars I think Alpha Herculis and Mu Cephei are still candidates. Other big ones to see in the sky are AlphaCygni-Deneb R Coronae Borealis, and BetaOrionis-Rigel, there are many large stars in the sky KW Sagitarii, V354 Cephei and KY Cygni but they do not have super-high mass. These large stars have lower mass but the most massive stars may have as much material as 150 suns, the Pistol Star and WR 20a have a very high mass and it is thought most massive stars can be in clusters or are binary twins. I have a feeling that space telescopes like Spitzer, Xeus and Swift may be able to lead us to more of these giants.


A supernova from one of these would be an incredible sight

Parrothead
2005-Feb-15, 01:52 PM
as for largest stars I think Alpha Herculis and Mu Cephei are still candidates. Other big ones to see in the sky are AlphaCygni-Deneb R Coronae Borealis, and BetaOrionis-Rigel, there are many large stars in the sky KW Sagitarii, V354 Cephei and KY Cygni but they do not have super-high mass.

A blurb in the news section of the April issue of Astronomy magazine says the same thing, it lists KW Sagitarii, V354 Cephei and KY Cygni as the "biggest" stars knocking Mu Cephi to 4th. All three have diameters of 1,500 suns, they have size just not the mass.

ngc3314
2005-Feb-15, 02:39 PM
Whatever happens, it will be an awesome sight. An object 5,000 light years away as bright as the moon. Now that's cool.
...and dangerous! Remember, not all (or even most) of a supernova's radiation is in the visible spectrum!

And most of a supernova's energy isn't released in electromagnetic radiation at all. Stan Woosley's quick memory tidbit was that 99% of the energy of a Type II SN is released in neutrinos, 99% of what's left is in the kinetic energy input that blows up the star - and the remaining 0.01% is what can often outshine the entire host galaxy. Of that, the peak often does come in visible light - for 1987A, the peak radiation output stayed in the UV for only a couple of days (just about long enough to get the IUE observatory pointed there) as the fireball cooled.

Some of the really dangerous action sets in later, once the expanding remnant has had time to accelerate some of its particles to very relativistic energies. Don't anybody buy any swamp land near Betelgeuse, or Eta Carinae, or the Pistol Star. I'd even steer clear of Kapteyn's star(s).

Philippe
2005-Feb-15, 05:12 PM
Don't anybody buy any swamp land near Betelgeuse, or Eta Carinae, or the Pistol Star. I'd even steer clear of Kapteyn's star(s).

Define "near", please.
:)

Seriously, if the visible light emission is strong enough to be as bright as the Moon from 5K lightyears, how far out is the "safe zone"?

Bob
2005-Feb-15, 05:39 PM
Define "near", please.

Those darned gamma rays might be lethal at several tens or even several hundreds of parsecs away.

http://www.tass-survey.org/richmond/answers/snrisks.txt