Last year there was a new nova in the night sky, now officially named Nova Delphini 2013. From Earth, it looked like a fairly dim new star in the constellation Delphinus. Novae such as this one are similar to the more popular supernovae. The popular view of a supernova is that of an exploding star. A large star runs out of hydrogen to fuel, and as a result collapses upon itself. This “core collapse” causes intense nuclear reactions which rip the star apart in a huge explosion, which is why this type of supernova is known as a core-collapse supernova.
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.
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.
Standard Variables
In the late 1800s Henrietta Leavitt was hired by Edward Pickering of the Harvard College Observatory. “Hired” in this case being a loose term, since Leavitt was not initially paid for her work. She was assigned the task of cataloging the brightness of variable stars from photographic plates. This is a tedious process, which is why it was done by women (known as Pickering’s Harem).
Stars Like Dust
When Carl Sagan said we are all stardust, that knowledge was derived from a long sequence of observations and applied physics. We can see the composition of stars by their starlight. We know that fusion occurs in their cores, and we know that the atoms in our body largely come from stars.
Disappearing Act
R Coronae Borealis is a dim star in the Northern Crown constellation. It is a yellow supergiant about 6,000 light years away. Normally it is a 6th magnitude star, just on the edge of visibility with the naked eye under a dark, clear sky. But in 2007 the star quickly faded from view, dimming to a magnitude 15 star by 2009. Magnitude is a logarithmic scale, so this is a huge difference in brightness. The star was nearly 4,000 times brighter in 2007 than 2009. Just how a star could fade so drastically in such a short time is a bit of a mystery.
Three is a Magic Number
Yesterday I talked about the star T Tauri, a red star that is transitioning into a main sequence star. The image yesterday was a composite of visible and near infrared images. The image below is a high resolution image at an infrared wavelength known as the K-band. You can see the visible star labeled as T Tau N (T Tauri North). You can also see two smaller stars, labeled Sa and Sb. These two stars don’t emit much light in the visible, so they can only be observed in the infrared. Earlier images didn’t resolve the binary pair, and instead only saw it as a single star (T Tauri South). It has only been in the past few years that we’ve seen them as a binary.
Hybrid
Sometimes in astronomy a weird idea can actually pan out. Suppose you have a neutron star that is absorbed by a red giant. Maybe the two happened to have a chance collision. More likely the neutron star was a close binary with a regular star, and as the star died it swelled to a red giant which engulfed the neutron star. What would happen? Back in the 1970s Kip Thorne and Anna Żytkow studied this hypothetical object, which is why they are now known as Thorne-Żytkow objects, or TZOs.
Winds of Change
The image above is of a star known as T Tauri. T Tauri is the prototype (primary example) of T Tauri type stars. In many ways T Tauri is a star in the making. Not quite a main sequence star, but more than a protostar.