Forum: Space / Science

on Thu 22 of July, 2010 22:15 PDT, by Nick H

http://www.theage.com.au/world/giant-star-takes-scientists-by-surprise-20100722-10n0d.html?autostart=1 (external link)

Quote:

ASTRONOMERS say they have discovered the most colossal star on record, in a region of space known as the Tarantula nebula in a neighbouring galaxy to our own.

The record-breaking star weighs 265 times as much as the sun and is millions of times brighter, they said.

The discovery has astonished scientists who thought it was impossible for stars to exceed more than 150 times the mass of the sun.

on Thu 22 of July, 2010 22:39 PDT, by RobVG

How do you weigh a star?

Why is it's mass less than its weight?

on Fri 23 of July, 2010 00:25 PDT, by Nick H

Read the article carefully. The reporter uses Mass and Weight interchangeably, and notes that THIS star weighs 265 SOLs compared to the expected top limit of 150 Sols.

How do you weigh (or determine the mass of) a Star in general:-

if it's got a planet or a binary star, from Kepler's laws of motion (or Newtonian/Einsteinian gravity) you can determine the total mass of the system.

For stars where the binary is too big, or not available, there is a well-established Colour-Luminosity relationship for main sequence stars derived from the Hertzsprung-Russell Diagram

http://en.wikipedia.org/wiki/Hertzsprung%E2%80%93Russell_diagram (external link)

The mass is not directly determined from thjis diagram but for Main Sequence stars an adequate calibration exists from numerous other methods

http://en.wikipedia.org/wiki/Main_Sequence (external link)

http://en.wikipedia.org/wiki/Mass%E2%80%93luminosity_relation (external link)

on Fri 23 of July, 2010 07:39 PDT, by TB

It might be useful to find out what method was used to estimate the mass. I'm no professional astronomer, but is it possible that if they're relying on Main Sequence precedent, the freakishness of the star is not its mass, but a different odd departure from Main Sequence averages?

on Fri 23 of July, 2010 15:33 PDT, by Nick H

http://en.wikipedia.org/wiki/R136a1 (external link)

From Wiki I found a useful link:-

Abstract of published paper here. probably links to full paper.

Looks like they've done the thinking and that a single massive star is the most likely situation.

http://arxiv.org/abs/1007.3284 (external link)

One thing about the 150 Msol limit - every limit has its caveats, for example the Eddington Limit where solar radiation pressure theoretically exceeds gravity at the surface of the star - the result is that there is high mass loss from the outer shell of the star, but the core mass can still be exceed the "limit"

http://en.wikipedia.org/wiki/Eddington_limit (external link)

Forum: Space / Science

That's not a star - THIS is a STAR!

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