General

The Zen of Astrophysics

Speaking in broad generalities, there are two main classes of physicist: those who generate new hypotheses and those who generate new data. The former are called "theorists" and the latter, in most of physics, are called "experimentalists." In astrophysics, we're called "observers" because we can't do experiments in the traditional sense. We have no knobs to turn, no switches to flip; we can't turn the dial to a maximally spinning black hole just to see what happens (oh, what fun that would be!).

Chandra Showcase for Google Sky

The latest version of Sky in Google Earth, released on January 09, 2008 at the American Astronomical Society meeting in Austin, Texas, now contains X-ray images from NASA's Chandra X-ray Observatory. Along with images from other NASA satellites, the addition of Chandra into Sky in Google Earth provides scientists, students, and amateur stargazers new opportunities to explore the Universe across the electromagnetic spectrum. Eli Bressert, Image Processor at the Chandra X-ray Center, discusses the Sky in Google Earth update.

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Do We Live in a Jelly Bean Universe?

Like the jelly beans in this jar, the Universe is mostly dark: 96 percent consists of dark energy (about 70%) and dark matter (about 26%). Only about four percent (the same proportion as the lightly colored jelly beans) of the Universe - including the stars, planets and us -is made of familiar atomic matter. Read about the make up of the Universe

X-Ray Astronomy vs. Medical X-Rays

A doctor's x-ray machine consists of two parts: an x-ray source at one end, and a camera at the other. The arm or mouth or other body part to be examined is placed in between these two parts. X-rays from the source shine through the impeding body part, and the camera records the x-rays that reach the photographic film inside. Bone is denser than muscle tissue and skin, so it stops more of the x-rays (and hence fewer x-rays make it to the region of the film that's behind the bone).

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