The star HD 140283 is a subgiant star with an estimated age of 14.46 billion years. That might raise an eyebrow or two for those of you who remember that the age of the universe is estimated as 13.77 billion years. It would seem that this particular star, sometimes referred to as the Methuselah star is older than the universe.
Black Hole Sun
We know that supermassive black holes exist in the center of most galaxies, and they can become quite massive (upwards of billions of solar masses). What we aren’t sure about is just how they come to be.
Star Seed
One of the big mysteries in cosmology is how supermassive black holes formed in the centers of galaxies. Did they form directly from large concentrations of matter and dark matter, or did they form when early stars collided and accreted into massive black holes? Another idea is that they may have formed from the collapse of supermassive stars. In this idea stars with masses of 10,000 Suns or more could have lived short, violent lives before their core collapsed into a massive black hole. It’s an interesting idea, but new research shows that such supermassive stars might have a different fate.
Take It to the Limit
Yesterday I mentioned that hypernovae (super-supernovae) are the result of the explosion of a star that’s about as massive as a star can be (about 150-200 solar masses). But how exactly do we know that this is an upper limit?
The Coolest Star
One way that stars are categorized is by temperature. Since the temperature of a star can determine its visual color, this category scheme is known as spectral type. The main categories of spectral type are M, K, G, F, A, B, and O. The coolest stars (red dwarfs) being M, and the hottest stars being O. Our own Sun is a G star.
The Great Eruption
Eta Carinae is a star visible in the southern hemisphere with a rather curious history. It was first cataloged in the 1600s as a 4th magnitude star, but by the time it was given the name Eta Carinae in the 1700s it was a 2nd magnitude star. By the early 1900s it had faded to an 8th magnitude star, but then toward the end of the twentieth century it had brightened to a 5th magnitude star. However its biggest change occurred around 1841, and became known as the great eruption.
Mix It Up
When we look at a cluster of stars, we find that they are chemically similar. That is, the ratio of different elements (or metals in astronomy lingo) in various stars are basically the same. This is pretty much what we expect, since these stars all formed in the same stellar nursery, and haven’t drifted apart from each other. Just as human siblings share similarities due to their common genetic origins, sibling stars share chemical similarities due to their common origin. But what about stars with a common origin that scatter across the galaxy? Do they have a common chemical fingerprint?
Doppelganger
Recently in Astrophysical Journal Letters a paper was published on the oldest “solar twin” yet discovered. The star, HIP 102152, is about 250 light years away from us, and about 4 billion years older than our Sun.
Stellar Noise, Stellar Sounds
NASA’s Kepler space telescope has stopped its initial run of collecting data in its search for new planets, but that doesn’t mean there will be no more new discoveries from that data. A good case in point can be seen from a recent article in Nature that demonstrates a clever way to measure the surface gravity of a star.