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A New Meaning for 'Star FM'
Observing >
There is a whole unsung branch of astronomy filled with men and women who just love radio; they can't get enough of it. I'm not talking about Top 40 or news radio or talk radio. The "radio" I refer to are waves from the cosmos itself and their message is changing the way we look at our universe.
By far the biggest chunk of glory in astronomy has gone to those who have studied what we can see in the visible wavelengths of light. Great telescopes, like at Palomar and Keck, have given us, to be sure, many stunning images of the visible worlds beyond.
But they show us only a small fraction of what is out there.
There are other unseen wavelengths of light, beyond what our eyes are sensitive to, which are trying to show us more of the Big Show. These photons have wavelengths thousands of times longer than the light we see, but can be picked up by special instruments. These are radio waves.
Because radio waves have such long wavelengths, the laws of physics tell us that they can only be efficiently bounced off and focused from huge surfaces like the radio dishes we often see in "alien” movies. Not huge as in a couple feet across. No, huge as in hundreds of feet end to end. Some radio telescopes are so big that several football games could be played on them simultaneously.
Their sole purpose is to collect radio waves from space and reflect them into an antennae suspended high above the dish. Computers can then translate the signals into information that we can "see,” thus telling us even more about the great beyond.
"Looking” at those radio waves we see, for example, our galaxy swimming in a sort of glowing hydrogen gas, pocketed all around in great clumps, future factories of stars.
In the radio we've discovered the center of our galaxy. It couldn't be pinpointed before because its visible radiation gets absorbed by all the dust and crud choking it there. But long radio waves can pass through dust and clouds like they're not even there. Which explains why radio telescopes can work under just about any weather condition here on this planet, even during pouring rain.
Radio astronomy has also revealed great jets of material spewing fast and furiously from the centers of other galaxies, jets which dwarf their entire parent galaxy, jets which are evidence for supermassive blackholes at the centers of those galaxies.
All this is an amazing feat given that the amount of energy we get at the radio end of the spectrum is less than miniscule at best. The entire surface of the Earth gets only a grand total of about a trillionth of a watt of it. Compare that to the 10 million watts we get in the infrared and visible from a single average star!
Moreover, radio astronomers must contend with all the radio radiation coming from ... us! We spew out so much radio energy for communications and other fun things that we actually get interference from our own radio waves bouncing off the Moon!
Which is why, when you see those gargantuan dishes, they are far away, often in valleys, hidden from much of our own interference.
In future articles we'll discuss the importance of the other invisible wavelengths, such as X-ray and ultraviolet and infrared, all of which put a new and different facet on this gem of a universe we live in.
Until next time, clear skies!
Have a question or comment? Write Mark Ritter here.
Posted by Administrator at 2002.09.14 02:32 PM | Comments (0)
