Astronomers have observed a fast radio burst originating from 5.5 billion light years away.
The Last Mile
Using data from the Cassini spacecraft, we’ve now measured the position of Saturn accurate to within a mile.
Movin’ Right Along
The motion of a star relative to us can be determined by measuring two quantities, radial motion and proper motion. Radial motion is the motion of a star along our line of sight. That is, motion directly toward us or away from us. Proper motion is the change in angular position of the star, from which we can calculate the motion perpendicular to the line of sight (known as transverse motion. You can see how this works by imagining someone walking through a room. If we know the rate at which the person is walking toward us or away from us (radial motion) and their movement relative to the far wall (proper motion), then we can use a bit of simple geometry to calculate their path through the room.
Radio Jupiter
In the visible spectrum, Jupiter is a bright, star-like point in the night sky. Viewing it with the naked eye, it would be easy to confuse it with a star except for the fact that it doesn’t twinkle. At radio frequencies Jupiter appears very different. It doesn’t have a simple round shape, for example, and it is extraordinarily bright. So bright that it can outshine the Sun at some radio frequencies.
DRAGNs in the Sky
A radio galaxy is a galaxy that emits large amounts of radio waves. They were first discovered in the 1950s, but it wasn’t until the 1960s when a technique known as aperture synthesis was developed that we could resolve the distribution of radio emissions within a radio galaxy. It then became clear that many radio galaxies had a double-lobed structure emanating from a galactic core. It was suggested that these Double Radio Sources Associated with Galactic Nuclei be known a DRAGNs, though the term has never really caught on.
Low Down on the Radio
Most radio telescopes have a traditional dish shape, such as Arecibo or Parkes. But there are other forms a radio telescope can take, for example the radio antenna on your car. You might not think of your car radio antenna as a telescope, but in a way it is.
A Distant Noise
A while back I wrote about a phenomena known as fast radio bursts (FRBs). These short bursts of radio energy have been a bit of a puzzle. On the one hand they they have all the appearance of being astronomical in nature. For one thing, the frequencies of the signal are spread out so that higher frequencies arrive before lower ones. This is known as dispersion, and is an indicator having traveled through the interstellar medium. On the other hand, the signals are unusually strong, and their short duration is similar to radio interference from sources on Earth. They’ve also only been detected at one radio telescope (the Parkes radio telescope in Australia). That is, until now.
Mini Me
Because microquasars are physically similar to regular quasars, with a compact massive core, accretion disk and jets, the dynamics of the two are likewise similar. But since the microquasar is stellar mass rather than a million solar masses, the timescale of a microquasar is much smaller. This means we can watch a system change over days rather than centuries.
Wow!
The Big Ear radio telescope was built in 1963 to survey the sky for extragalactic radio sources. It is a type of radio telescope that uses the rotation of the Earth to make observations. The receiver of the radio telescope can be moved north or south, but to view things east and west you have to wait for the Earth to rotate in the right direction. This type of telescope is perfect for making sky surveys, because you can point it in a particular declination (the sky version of latitude), and then let the Earth’s motion move you through a full circle of sky over the course of a day.