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New Star

valleyman

By valleyman
in The Astro Lounge

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valleyman

valleyman

Posted
Posted

Just hearing on the 9 oclock news that a new star has been found.

250x bigger than the Sun and 100,000 light years away.

I am not going to even try to calculate that into miles.

Oh and it is due to explode in about 1 million years.

The mind boggles

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brianb

brianb

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it is due to explode in about 1 million years.

If it doesn't evaporate first.

IIRC the main sequence lifetime of a star which is not shedding significant amounts of mass is inversely proportional to the cube of the mass ... a 100 solar mass star therefore has a main sequence lifetime of one millionth that of the Sun, i.e. around 10,000 years. OTOH the radiation output is so violent that the mass loss rate is far from insignificant! Again IIRC you can model the end of the main sequence stage of any star initially more massive than 30 solar masses by considering a 30 solar mass object as the excess mass will be lost in stellar wind before the main sequence phase ends.

With exceptionally massive stars (>80 solar masses) you also have to consider that the star may not live long enough to reach the end of, or even the beginning of, the main sequence - if temperatures rise high enough, pair production can cause a core collapse in a core containing only hydrogen & helium, resulting in the production of a black hole and a very violent explosion, much more powerful and longer lasting than an "ordinary" core collapse (type 2) supernova.

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Space Oddity6

Space Oddity6

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It is now something like 265 times bigger than the Sun but they think at some point it was 320 times bigger.

So, this might be a really stupid question, but going from its size and distance from us, if that exploded right now, would that kill us or change life on Earth or our Solar system, or is it too far away? From the amount of stars up there I'm guessing this happens fairly regularly?

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brianb

brianb

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if that exploded right now, would that kill us or change life on Earth or our Solar system, or is it too far away? From the amount of stars up there I'm guessing this happens fairly regularly?

Way too far away! Might be naked eye visible for a couple of months ...

... and, whilst not exactly a common event, not that unusual either.

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EA2007

EA2007

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Made a link to it earlier, they just showed it on the BBC 1 news.

However, they showed a picture of the Sun and a scale (supposedly) version of the new star...tbh it didn't look like it was 250x as big (more like 4x) and also they said it was in a galaxy far far away...forgive me but isn't the LMC right next door!?

I think the BBC needs to do some more research on it. I mean VV Cephei and the Pistol star were meant to be the largest.....and they are massive when you do a scale image next to the sun, kinda like a pea next to a beachball.

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iamjulian

iamjulian

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However, they showed a picture of the Sun and a scale (supposedly) version of the new star...tbh it didn't look like it was 250x as big (more like 4x) ... I mean VV Cephei and the Pistol star were meant to be the largest.....and they are massive when you do a scale image next to the sun, kinda like a pea next to a beachball.

You are getting muddled between mass and size. This new one is 250ish times more massive, but not 250 times the size.

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umberto

umberto

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There is an article in the August S@N magazine on super massive stars (200 X mass of sun) according to the article new theories are needed to explain these stars - the puzzle is that they can get this big before their fusion process kicks in, creates a solar wind and stops them getting any bigger - which should happen before 8x the suns mass has clumped into the same spot. Must be a very impressive bang when they run out of fuel!:eek:

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brianb

brianb

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the puzzle is that they can get this big before their fusion process kicks in, creates a solar wind and stops them getting any bigger - which should happen before 8x the suns mass has clumped into the same spot.

Depending on the amount of dust ... "clean" hydrogen will transmit the radiation rather than being repelled by it, it is supposed that this is how the supermassive stars that MUST have formed in the early universe (to generate the metals we see today) were able to exist. There is still a limit, though. Somewhere around 100 solar masses ... not sure where the "250 solar mass" estimate of this star comes from but I seriously doubt the accuracy - other supposedly supermassive stars have been scaled back drastically after further detailed study.

Stellar formation models include nuclear and gravitational forces together with electromagnetic radiation but not electrostatic forces. I have a suspicion that this may be an important omission. Otherwise we need to look at might be going on in a 200 solar mass "star" i.e. why the radiation doesn't blow the thing apart before it has formed - maybe it is still forming? maybe what we're seeing is not nuclear fusion but intense emission from a black hole which is actively gobbling material dense enough to behave like a stellar envelope when observed from a great distance?

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umberto

umberto

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maybe what we're seeing is not nuclear fusion but intense emission from a black hole which is actively gobbling material dense enough to behave like a stellar envelope when observed from a great distance?

Yeah - I read something in scientific american/new scientist about a theory of formation for the massive black holes at galactic centers - the jist was the earliest stars formed and collapsed to black holes whilst still in the original (denser) hydrogen gas clouds of the early universe and then the black holes grew to 1000's of solar masses by acretion from the gas cloud and this in-fall of gas would generate presure/heat/fusion on its way in to the black hole, i.e. a super massive star like object (blackhole with a star for an atmosphere). Does that have a less spectacular end - when it runs out fuel do the lights just switch off:icon_scratch:

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umberto

umberto

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Well hopefully the scientists will keep finding more and we will get lucky and they find one with only a few years left on the clock, not too far away and not too close so we can all watch the show:D

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yesyes

yesyes

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Well hopefully the scientists will keep finding more and we will get lucky and they find one with only a few years left on the clock, not too far away and not too close so we can all watch the show:D

That one is called Betelgeuse... ;-)

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