Monster Hypergiant Star Discovered 94
astroengine writes "A gargantuan star, measuring 1,300 times the size of our sun, has been uncovered 12,000 light-years from Earth — it is one of the ten biggest stars known to exist in our galaxy. The yellow hypergiant even dwarfs the famous stellar heavyweight Betelgeuse by 50 percent. While its hulking mass may be impressive, astronomers have also realized that HR 5171 is a double star with a smaller stellar sibling physically touching the surface of the larger star as they orbit one another. 'The new observations also showed that this star has a very close binary partner, which was a real surprise,' said Olivier Chesneau, of the Observatoire de la Côte d'Azur in Nice, France. 'The two stars are so close that they touch and the whole system resembles a gigantic peanut.'"
Better info at ESO (Score:3, Informative)
Re:It's mere gas (Score:5, Informative)
The photosphere is a pretty clearly defined boundary.
If you want to go all "stellar windy" on the sun, it extends out beyond Pluto.
Re:size? (Score:5, Informative)
> 1300 times as massive.
No. Original paper says ~39 Msun. Radius is ~1300. A star massing 1300 Msun couldn't hold itself together, both in terms of gravitational and outward radiation pressure.
Source: http://arxiv.org/pdf/1401.2628... [arxiv.org]
Re:It's mere gas (Score:4, Informative)
Like all proper planets (ie, Pluto and the ilk excluded), Jupiter consists of a ball of rock and some atmosphere. It just happens that Jupiter's atmosphere is extreme, consisting of 86-96% of the planet's mass. Yet, being gas, you can't tell where it starts and ends.
Re:When I hear about an object like this (Score:4, Informative)
Re:Awesome!! (Score:5, Informative)
That binary system is going to make one heck of a supernova at some point in the distant future.
Maybe, probably not, but there is not enough data to know. It's been over four hundred years since the last recorded supernova in the Milky Way, and telescopes weren't that great in 1604. (Also the standard note about time and distance in astronomy, the star's light we see today is from about 12,000 years in our past. We cannot see today, we see the past.)
There is not enough data to say what will happen, and there are only a few major options for a star that size: partial collapse, full collapse, or ablation.
It might go through a series of partial collapses, with many small contractions end up ejecting huge chunks of the star, then re-expanding, and themselves re-exploding on their way out. This seems to be a fairly normal end-of-life pattern. Basically the core works like a fireworks launch platform as we see in summertime displays. Eventually the remaining core might be collapsed or not, but the show will be enjoyable. The result is a small nebula.
It might collapse into a neutron star. It might even collapse to a black hole. Either of these collapses MIGHT lead to a supernova, or maybe even a hypernova, or have a bunch of gamma bursts, or, most boring, nothing much at all; it just collapses with a (relatively mild compared to supernova) explosion and the outer layers blow away. Modern astronomers never seen it happen up close, so everything is a guess. Now that the partner is known people might be able to make a better guess, but it is still a guess. Depending on when it explodes, if ever, it will likely form a big nebula.
The actual article says the larger star is rapidly shedding mass. If it is throwing enough mass out fast enough (which will be affected by its binary partner) it will shrink enough to avoid a core collapse. In that case it will throw out a bunch of mass and in a few centuries appear as a small nebula.
But again we don't know what will happen because there are no similar data points. If you are looking for nearby stars to go supernova, there is a short list of known supernova candidates [wikipedia.org] that we can watch. Otherwise the supernova we see are from distant galaxies where we can only speculate about.
Re:size? (Score:5, Informative)
The 22 and 40 look like lower and upper bounds. In section 6.1 of the paper, it says, "we infer the lowest current mass of the system to be 22±5 [solar masses]" . They mention this value comes from a calculation based on Kepler's 3rd law. So it looks like the lower bound comes from orbital mechanics based on the orbit of the companion star and the upper bound of 40 comes from their interferometry observations and modeling of that data, but they consider it more likely that the true value is closer to the higher value.