Giant Star Discovered...but???

One of those little news clips on Yahoo mentions the discovery of an absolutely massive star but i'm sure there must be some editorial mistakes in the information provided; heres what it says:

A huge star a staggering 320 times the size of the Sun has been found by scientists - and quickly labelled the biggest ever discovered. The UK-led team behind the incredible discovery - headed by Professor Paul Crowther - has also said the giant star is around 10 million times brighter than the Sun.
Using the European Southern Observatory's aptly-named Very Large Telescope and Nasa's Hubble Space Telescope, the find was made during a study of two clusters of stars in a galaxy next to our own solar system called the Large Magellanic Cloud.
If the enormous star replaced the Sun in our galaxy, it would outshine it to the same degree as the Sun outshines the full Moon and reduce the Earth's year to just three weeks, the scientists claim.
Until now, experts had accepted that stars could be a maximum of 150 times the mass of the Sun.
Within the cluster, several stars were found to be larger than that but one - R136a1 - stood out.
Bizarrely, stars lose weight during their life.
Describing it as "middle-aged", Professor Crowther believes R136a1 has shed around a fifth of its mass since its birth just over a million years ago - but it is still currently a mind-boggling 265 times larger than the Sun.
The University of Sheffield academic said: "Owing to the rarity of these monsters, it is unlikely that this new record will be broken any time soon."
The findings are published in the journal Monthly Notices of the Royal Astronomical Society.

Now admittedly i'm no expert on these things but 320 times bigger yet 10 million times brighter seems a little bit of a stretch...though i'm willing to accept there theres some astronomical physics that i'm not to grips with going on there but then to say the star is 'middle aged' having been born just over a million years ago??


So the life expectancy of this giant of the cosmos is 2million years???


That doesn't sound right to me...saying that it is Yahoo so its probably not exactly been intensively researched.

DrFroggies wrote: »

One of those little news clips on Yahoo mentions the discovery of an absolutely massive star but i'm sure there must be some editorial mistakes in the information provided; heres what it says:
Now admittedly i'm no expert on these things but 320 times bigger yet 10 million times brighter seems a little bit of a stretch...though i'm willing to accept there theres some astronomical physics that i'm not to grips with going on there but then to say the star is 'middle aged' having been born just over a million years ago??


So the life expectancy of this giant of the cosmos is 2million years???


That doesn't sound right to me...saying that it is Yahoo so its probably not exactly been intensively researched.

Yeah, thats right, The bigger the star, the shorter its life. Betelgeuse in Orion is a red supergiant, only a few million years old which could go supernova at any point due to having used up all its hydrogen and is now fusing heavier elements. When it tries to fuse iron, it's game over. The star you mentioned above is much bigger than Betelgeuse. The flip side to this are red dwarfs, stars who take hundreds of billions to trillions of years to convert all their hydrogen to helium.

Here's a link with an image showing the sizes of stars, showing our sun as a yellow dwarf, much bigger than the red dwarf stars but nothing in comparison to the new discovery.

http://www.physorg.com/news198924098.html?

Hi

In theory, it is thought that the maximum limit to the mass of a star that can form is determined (among other things) by the radiative pressure (energy release) of the star verses the gravity of the star that is pulling in material from the surrounding nebula.

There comes a point when this pressure is greater then the gravity of the star. Then material cannot fall onto the star any more and the star stops growing and settles down to main sequence life.

One of the big factors which determines when this will happen is the actual mix of elements in the nebula the star forms out of. In particular, the percentage of "metals" in the nebula. In terms of astrophysics "metals" are elements heavier then Helium as opposed to the chemistry definition of metals.

In the early universe where there was only Hydrogen and Helium, extremely massive stars formed called blue supergiants which were hundreds of times more massive then the sun. These stars formed out of pristine big bang material which included nothing heavier then Helium and a small amount of lithium. Because there was no "metals" in the mixture which formed these stars, it was somehow more difficult for the star to radiate away its energy. This allowed more and more material to be able to fall unto the star before pressure of radiation and shear sunlight eventually forced the material to stop falling inwards.

Today, there is a lot more dust and other "metals" about in the universe and in stellar nebula. This has the effect of somehow making it easier for stars to radiate light and pressure outwards into the stellar nebula. The effect in turn is that today once the star reaches only about 40 solar masses, the radiative pressure is usually strong enough to stop further material from continuing to accrete onto the star.

Therefore in essence it is very hard for stars of this size to form today, although it was much easier in the past.

I would imagine that there still must be some nebula in the galaxy even today that have remained thermally stable since the birth of the universe and have never had any star formation activity in them. Therefore they would still be relatively unpolluted and metal poor. We can also see that there is a lot of gas between the galaxies. This is constantly being pulled into the galaxy to form new stars and is by its nature pristine, unpolluted and metal poor. I suspect that this large star formed out of such a cloud and that is why it got to be so large.

It will be interesting to see when the star's spectrum is taken to see if it is metal rich or metal poor.

I am not a physics guy just an avid amateur astronomer who has always been fascinated by all this stuff.


Dbran

Hi

I understand that the mass of a star verses its volume are two independant things of each other. The volume depends to a large extent on the stage in the life cycle that the star is. If it is the red giant, it may have a huge diameter but in actual fact the outer layers of the largest stars themseves would be very tenous and low density and therfore not a true reflection of it's mass.

Some of the most massive stars do not actually stay around long enough to go into their supergiant phase and just explode as supernova when they are still on the main sequence.

The last supernove that they found back in 1987 in the magellanic cloud when it was eventually tracked down was actually found to be a blue main sequence star ie it was compact and not a large bloated behemoth supergiant like betelgeise.

But I remember hearing at a talk/podcast that the largest theoretical size would be out to about the orbit of Saturn which I believe is the actual size of VY Cannis Major?


Dbran

ynotdu wrote: »

I am all set!

Wouldn't you rather have this: