What Radio Astronomers

Insomnia is a valuable affliction for optical astronomers, who need to make good use of the hours of darkness when the sun is on the other side of the earth. But as Karl Jansky discovered so many years ago, the sun is not a particularly bright radio source. In consequence, radio astronomers (and radio telescopes) can work night and day. The VLA, for example, gathers data (or runs tests) 24 hours a day, 363 days a year. Not only is darkness not required, but you can even make radio observations through a cloud-filled sky. The senior author of this book even observed a distant star-forming region in the midst of a storm during which lightning struck near the VLA and disabled it for a few minutes.

As the Dutch astronomer Jan Oort realized after reading Reber's work in the 1940s, radio waves opened new vistas into the Milky Way and beyond. Radio astronomers can observe objects whose visible light doesn't reach the earth because of obscuration by interstellar dust or simply because they emit little or no visible light. The fantastic objects known as quasars, pulsars, and the regions around black holes—all of which we will encounter later in this book—are often faint or invisible optically, but do emit radio waves.

The spiral form of our own Galaxy was first mapped using the 21 cm radio spectral line from neutral (cold) hydrogen atoms, and the discovery of complex molecules between the stars was made at radio frequencies. The very center of our own Milky Way Galaxy is hidden from optical probing, so that most of what we know of our galactic center has come from infrared and radio observation. Since radio interferometers are

Astro Byte

Many people are surprised to learn that VLA stands simply for Very Large Array. But it is nevertheless an apt description for a telescope spanning the Plains of St. Augustine near Socorro and Datil, New Mexico and with the resolution of a telescope some 21.7 miles (35 km) across.

Astro Byte

Many people are surprised to learn that VLA stands simply for Very Large Array. But it is nevertheless an apt description for a telescope spanning the Plains of St. Augustine near Socorro and Datil, New Mexico and with the resolution of a telescope some 21.7 miles (35 km) across.

detecting an interference pattern, radio data has to be processed in ways different from optical data. But the end result is either a radio image, showing the brightness of the source on the sky, or a radio spectrum, showing a spectral line or lines. In Chapter 18, "Stellar Careers," we'll describe how radio spectral lines arise.

Image of our Galaxy, the Milky Way, as seen with the Very Large Array at 90 cm.

SgrOMI A %

SgrDSSR \

Wide-Field Radio Image of the Galactic Center X = 90 cm

Tfirvads

The Cane Baekgn>wnl Galaxy

TTi/vodf

SgrOMI A %

SgrDSSR \

Sen- thread: The Pelican I SgrC Coherent \ structure? ji

SgrE

740 light jvan Tornado (SfiR?)

Telescopes Mastery

Telescopes Mastery

Through this ebook, you are going to learn what you will need to know all about the telescopes that can provide a fun and rewarding hobby for you and your family!

Get My Free Ebook


Post a comment