X-Ray Vision

In the sky, there are things that glow. In fact, they radiate. For a very long time, astronomers were limited to observations made the light visible to the human eye, which occupies only a tiny fraction of the electromagnetic spectrum.

Early X-Ray Astronomy: Something hot in the region of Scorpius.

With the prediction and discovery of radio waves in the mid 19th century, suddenly there was more than meets/is detected by the eye. X-Rays, discovered by Wilhelm Rontgen in 1895, were even more mysterious.

As the Earth's atmosphere blocks x-rays, looking for x-ray sources in the rest of the universe had to wait until the 50s and 60s, when rockets and satellites could go beyond the protective blanket. This BBC audio slideshow, in the news this morning briefly covers the 50 years since the start of x-ray astronomy.

Something in the Wikipedia article linked above caught my eye, although it's discussed on in the slideshow too.

Unlike visible light, which is a relatively stable view of the universe, the X-ray universe is unstable. It features stars being torn apart by black holes, galactic collisions and novas or neutron stars that build up layers of plasma that then explode into space.

The visible light universe-- the one we and astronomers from much of human history see when we go out in the back garden or peer through a telescope-- is a relatively calm place, almost the unchanging heavens of the pre-Galileo era. The x-ray universe is violent, dramatic, in constant turmoil. What a totally different picture we get of the same places when we change the instruments we are able to use to observe things around us.

V.