The length of a day on Earth is about 24 hours. This is true no matter where you are on the Earth. The periods of daylight vary by latitude, but a day from noon to noon is the same everywhere on Earth. The reason for this is that the Earth is solid, so it all rotates at the same rate. …
It’s a Gas
I’ve already discussed how we can look at the relation between the distribution of stellar speeds in a galaxy and the mass of a galaxy’s central black hole. This relationship is useful because measuring stellar motion in galaxies is fairly hard, and there is a limited number of galaxies for which we have good measurements. For many galaxies, the relation …
Bang Goes the Theory
Back in September I wrote about a phenomenon known as a gamma ray burst (GRB). A GRB is an intense emission of gamma rays that occasionally appear in the sky. There are various proposed mechanisms for GRBs, but one of these is the collapse of a large star (a hypernova) that causes the star’s core to collapse into a black hole. …
In a Relationship
One of the more interesting modern findings about galaxies is that most of them have black holes in their centers. We can’t observe these black holes directly, but we can see their effects through things such as high-energy jets streaming away from them. In many cases, we can even get a measurement of their mass by observing the distribution of …
Polarizing Effect
The image above is a visible light image of the star VY Canis Majoris. The rainbow effect you see is not due to false color imaging (though the image has been manipulated a bit to make the colors stand out), but due to the fact that it is a polarized light image of the star. When we think of the properties …
Sonic Rainboom
One of the basic laws of physics is that nothing can travel faster than light. Actually that isn’t quite true. Specifically, nothing can travel faster than light travels in a vacuum. It is possible for things to break the light barrier when traveling through a material. The effect is known as Cherenkov radiation. While the speed of light in a vacuum is …
Sounding it Out
The figure above is the best evidence we have of a planet smaller than Mercury orbiting another star. It is taken from the a paper published in Nature this month. While it might not look that impressive, let me explain why it is. The data from this image represents measurements in brightness of the star known as Kepler 37 over a …
Yop!
Yesterday I mentioned that the IceCube Neutrino observatory doesn’t detect neutrinos directly, but instead detects the flash of light that occurs after a neutrino collides with a water molecule. As you can imagine, the light emitted with a single neutrino collides with a single molecule is pretty faint. So how do we observe such faint light? We use a photomultiplier …
Zoom and Enhance
If you’ve ever watched American detective shows, you’re probably familiar with the infamous “zoom and enhance” trick. A piece of video, usually a surveillance camera, has recorded a critical moment of a crime. Our TV detectives use some clever computer trickery and are able to read the name tag of the assailant reflected in the victim’s eyes. Of course …