X-ray astronomy
A scope named Chandra
Black holes revealed
Dark matter detailed
Neutron stars


Two views of NGC 253 -- a typical spiral galaxy when seen in optical wavelengths. Move the mouse over the optical image to see giant outflows of hot gas as observed through the prism of X-rays.

(Visible light) Space Telescope Science Institute. (X-ray): Rosat archive, Laboratory for High Energy Astrophysics at NASA/Goddard Space Flight Center.


Things that go bump in space
6 Aug 1999. When the space shuttle Columbia roared into space on July 23, she made lots of headlines. Columbia was the first shuttle commanded by a woman. An ominous fuel leak during the launch did not cause an explosion, but may explain the shuttle's slightly shrunken orbit.

And Columbia carried the heaviest payload in shuttle history. Some newspapers even mentioned that the payload was an X-ray telescope, but judging from the headlines, the world will little note nor long remember the Chandra X-ray Observatory. Two views of NGC 253 -- a typical spiral galaxy

Not so for astrophysicists -- scientists who observe physics "experiments" in space that cannot be performed on Earth. For them, the check-out period of the new telescope is fingernail-biting time. If this masterpiece of engineering works as planned, it could reveal a great deal about exactly what is the universe. It could reveal unprecedented detail about the menagerie of galactic oddities that seem to hearken from science fiction, not science fact:

  • Neutron stars are small and so immensely dense that one teaspoonful weighs more than a fully loaded sports-utility vehicle.

  • Pulsars are neutron stars that pulse with a regular drumbeat of intense, enigmatic radiation. The beats could not arrive more accurately if they were timed by an atomic clock.

  • Black holes are the true heavyweights of the universe, with more or less infinite density and gravitation so intense that not even light can escape. Black holes cannot be seen directly, but the matter they gobble up leaves tracks in the X-ray spectrum.

  • Active galactic nuclei are apparently powered by gargantuan black holes that contain the mass of between one million and one billion suns. The variety called quasars, formed early in the universe, radiate as much energy as 1,000 normal galaxies, and are visible 10 billion light years distant.

  • Dark matter makes up most of the universe, but that's about all we know about it. Chandra should give a better picture of its location. Cosmologists trying to figure out the fate of the universe want more clues about this bizarre substance.
All these weirdnesses have two things in common. First, their existence, although accepted, seems barely credible, as they are just too dense, energetic or just plain strange. Second, they emit huge amounts of X-rays -- an energetic form of electromagnetic radiation that is blocked by our atmosphere. Although that's handy for us, it means X-ray astronomy must occur in space.

Like the sparks and twisted metal of a collision derby? Love the fireworks of a July 4th? Then you'll crave the study of X-rays coming from the immense ruckuses wracking distant corners of the universe.

The pause that reminds
If you're wondering whether we're talking about the same X-rays that dentists use to find rot in your teeth, you're right.

But let's get formal for a second. X-rays, like visible light and radio waves, are a part of the electromagnetic spectrum, which is defined as waves that can carry energy through space. The key thing about electromagnetic waves is that as wavelength gets shorter, the wave carries more energy.

The hottest part of a candle flame is the blue part, not the yellow: Blue light has a shorter wavelength than yellow. A traffic cop bathes your Porsche 911 GT3 in radio-frequency waves (radar) to determine how badly you're busting the speed limit ("I know I was doing 180, but it's only kilometers per hour, officer, honest...") Cops don't use x-rays, because they would fry you, be blocked by the atmosphere, or go right through your car.

This is helpful, if not exactly rocket science.

But since physics tells us that energy is conserved -- neither gained nor lost, except in nuclear reactions -- we can figure that more energetic (shorter-wavelength) electromagnetic radiation comes from more energetic sources. Chandra, therefore, will be taking measurements from some awfully strange stuff. More specifically, it will use a spectrograph to measure the exact wavelength of the incoming rays, and an imaging device -- a camera -- to make X-ray pictures.

If X-rays go in one side and out the other, how can this new telescope "catch" them?

The Why Files
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