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.
Super Luminous
A supernova is a stellar explosion. They can occur when a large star exhausts its ability to fuse hydrogen into higher elements, and its core collapses. The resulting rebound rips apart the outer layers of the star, creating a supernova while the remains of the core collapses into a neutron star. Another type of supernova, known as a thermal runaway or type Ia, occurs when a white dwarf is a close companion with another star. As outer layers of the companion are captured by the white dwarf, it can trigger a runaway nuclear reaction that rips apart the white dwarf. This latter form always has about the same absolute brightness, which is why they are used to measure the distances of far galaxies.
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.
Fault In Our Stars
Type Ia supernovae are brilliant stellar explosions that can outshine an entire galaxy. They also have the useful property of always exploding with a similar brightness. This makes them useful in determining the distances of galaxies. By comparing the observed brightness of a type Ia supernova to its standard brightness, we can calculate the distance of the supernova, and the galaxy in which it resides. But while we know type Ia supernovae have a consistent brightness, we aren’t entirely sure why.
Bubble Pop
Between the vast expanse of stars in our galaxy there is diffuse gas, dust and plasma known as the interstellar medium. It has been known for quite some time through its effects on radio waves and other light sources. But making a detailed map of this medium has been difficult.
Even Odds
In the early moments of the universe, hydrogen and helium were formed through a process known as baryogenesis. Trace amounts of other elements such as lithium were also produced, but none of the heavier elements. This means that the first generation of stars were composed of hydrogen and helium, and it is only through fusion in their cores that the heavier elements we see today were created. The carbon, oxygen and iron in our bodies was produced through that process, which is why it is often said that we are star stuff.
Zombie Jamboree
Type Ia supernovae have property that is very useful for astronomers. When they explode, they have a maximum brightness that is fairly consistent. This means they can be used as “standard candles” to determine the distance of galaxies billions of light years away. One challenge we have with this type of supernova is that we haven’t confirmed what causes them.
The Sleeper Awakens
The image above was taken by the Spitzer infrared space telescope in 2004. It shows what appears to be a red supergiant star in the galaxy known as M74, about 30 million light years away. It isn’t a particularly good image, because in 2004 it was just a red supergiant in a typical galaxy. There are billions of such stars in the universe, and its image was only captured because we do survey images of galaxies and such.
Dust to Dust
We are the dust of stars, as Carl Sagan so famously said. The elements in our bodies (with the exception of hydrogen) were formed within stars, and then cast out to the universe when large stars explode as supernovae. Of course simply creating elements by nuclear fusion and sending them flying into the cosmos isn’t quite enough to make stardust. The elements also have to clump into dust particulates. Understanding that process has posed a bit of a challenge, but now a new paper in Nature has observed it happening in real time.