Greetings from Boulder! I’m at the National Radio Sciences Meeting of URSI, listening to lots of talks on radio astronomy and geosciences, as well as madly finishing my own talk which I gave yesterday.
I just had to share this cool website that was in one of the talks in the education section of the radio astronomy session. The Long Wavelength Array is a telescope in New Mexico that is being developed to study very low frequency radio waves from the cosmos, just a bit lower in frequency than the PAPER project that I work on. They are at a point where they can image the entire sky every few
minutes seconds*, and they are making these images available in real time. Check out what the sky looks like at a few 10s of megahertz right now at LWA TV.
The circle on the left is the entire sky overhead. Note that, as it is late afternoon in winter, the Sun is fairly low in the sky. The color scale ranges from dimmest (blue) to brightest (red). The Sun isn’t all that bright, though that is partly because it is low in the antenna “beam” where it is less sensitive. However, even when it is high in the sky, it does not necessarily dominate. The circle on the right represents the polarized emission from the sky at these frequencies.
Cyg and Cas refer to Cygnus A and Cassiopeia A, the two brightest radio sources in the sky. I love these two, as they are the first things to pop up in our own PAPER images from the Northern Hemisphere. Cygnus A is actually an active galactic nucleus, or a supermassive black hole that is eating up material around it, spewing out jets of high energy material since it’s a very messy eater. If you zoom way in on Cygnus A with something like the Very Large Array, you get this gorgeous image:
Cassiopeia A is a remnant from a supernova, or a massive star that exploded at the end of its lifetime. To the VLA, it looks like this:
And those are just TWO of the THOUSANDS of radio sources in the sky. With more data, more averaging, and improved techniques, radio astronomers are drilling further down to fainter and fainter sources in these low frequency maps. But point sources aren’t the only things to see. That dotted line across the middle represents the Milky Way, our own spiral galaxy. Unlike the starlight that we see in visible wavelengths, however, what we see in the radio is emission from electrons, tiny charged particles, as they spiral through the galaxy’s magnetic fields near the speed of light. Really cool.
With realtime data like this, the LWA and other such projects will open up a new dimension to the radio sky: the time domain. That is, with such an all-sky monitor, we’ll have records of radio sources that flare-up brightly, some of which are still unexplained. The sky is actually a huge area to search, and strange things may be happening when we are not looking. We’ve only seen the tip of the radio flare iceberg, and new tools like LWA-TV will expand our view.
*Whoops! Thanks for the correction, Jake!