Astronomy Picture of the Day 9-28-02

NASA ^ | 9-28-02 | Robert Nemiroff and Jerry Bonnell

[petuniasevan]

Astronomy Picture of the Day

Discover the cosmos! Each day a different image or photograph of our fascinating universe is featured, along with a brief explanation written by a professional astronomer.

2002 September 28

X-Ray Rainbows
Credit: J. McClintock et al. (CfA), CXC, NASA

Explanation: A drop of water or prism of glass can spread out visible sunlight into a rainbow of colors. In order of increasing energy, the well known spectrum of colors in a rainbow runs red, orange, yellow, green, blue, indigo, violet. X-ray light too can be spread out into a spectrum ordered by energy ... but not by drops of water or glass. Instead, the orbiting Chandra X-ray Observatory uses a set of 540 finely ruled, gold gratings to spread out the x-rays, recording the results with digital detectors. The resulting x-ray spectrum reveals much about the compositions, temperatures, and motions within cosmic x-ray sources. This false color Chandra image shows the x-ray spectrum of a star system in Ursa Major cataloged as XTE J1118+480 and thought to consist of a sun-like star orbiting a black hole. Unlike the familiar appearance of a prism's visible light rainbow, the energies here are ordered along radial lines with the highest energy x-rays near the center and lowest energies near the upper left and lower right edges of the image. The central spiky region itself is created by x-rays from the source which are not spread out by the array of gratings.

[petuniasevan]

Astronomy Fun Fact:

XTE J1118+480 is known as an "X-ray nova" because it undergoes occasional eruptions followed by long periods of dormancy. The above image was obtained in an exposure of 7 1/2 hours.

[petuniasevan]

[BossyRoofer]

WOW! X-ray rainbows. Good job APOD!

[RightWhale]

The grating of the spectrometer is round rather than a series of parallel straight lines. It's a mechanical device of metal rather than glass and the framework is aluminum and the optical parts are gold.

[firewalk]

Thanks!

[aomagrat]

That looks like one of those velvet black light posters I had on my wall back in the early '70's.

[sleavelessinseattle]

Fascinating...I presume the denser the material that the "optical" part of the spectrometer, the greater the distinctions that would show up between different frequencies of X-rays... I wonder why they didn't go with an even heavier metal??? Perhaps corrosion resistance...APOD Allways delivers the good stuff!!!