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Welcome to the World of Multiwavelength Astronomy!

The Multiwavelength Universe

Optical Image of the cosmos

Radio Image

Gamma Image

The night sky has always served as a source of wonder and mystery to people. However, it has only been in the past few decades that we have truly begun to 'see' the Universe in all its glory. This is because we have only recently been able to look at the Universe over the entire electromagnetic spectrum. Our Universe contains objects which produce a vast range of radiation with wavelengths either too short or too long for our eyes to see.

Instruments which examine all parts of the electromagnetic (EM) spectrum have been available to us only in the 20th century, since the rocket age was required to get instruments sensitive to the infrared, ultraviolet, X-rays, and gamma-ray wavelengths above the Earth. (This "view from space" is extremely important since radiation in these wavelengths is absorbed by the Earth's atmosphere).

Some astronomical objects emit mostly infrared radiation, others mostly visible light, and still others mostly ultraviolet radiation. What determines the type of electromagnetic radiation emitted by astronomical objects? The simple answer is TEMPERATURE!

A solid contains molecules and atoms that are in continuous vibration. Inside a gas are molecules that are flying about freely at high rates, continually bumping into each other and surrounding matter. That energy of motion is called HEAT. The hotter the solid or gas, the more rapid the motion of the molecules. And temperature is just a measure of the average energy of those particles.

The optical image of the cosmos seen on the left (top) is courtesy of the Lund Observatory; the radio image (at 408 MHz; center) is courtesy of The Max Planck Institute for Radio Astronomy (generated by Glyn Haslam); the gamma-ray image (bottom) is from the EGRET experiment on-board the Compton Gamma-Ray Observatory.

What Kinds of Objects Typically Emit What Kinds of Radiation?

Do you want to understand in more detail the relationship between temperature and electromagnetic radiation (and typical sources that emit both)? Look at the chart below.

Type Of Radiation Radiated By Objects At This Temperature Typical Sources
Gamma-rays more than 108 Kelvin (K)accretion disks around black holes
X-rays 106-108 K gas in clusters of galaxies; supernova remnants; stellar corona
Ultraviolet 104-106 K supernova remnants; very hot stars
Visible 103-104 K planets, stars, some satellites
Infrared 10-103 K cool clouds of dust and gas; planets
Microwave 1-10 K cool clouds of gas, including those around newly formed stars; the cosmic microwave background
Radio less than 1 K radio emission produced by electrons moving in magnetic fields

Imagine the Universe is a service of the High Energy Astrophysics Science Archive Research Center (HEASARC), Dr. Alan Smale (Director), within the Astrophysics Science Division (ASD) at NASA's Goddard Space Flight Center.

The Imagine Team
Acting Project Leader: Dr. Barbara Mattson
All material on this site has been created and updated between 1997-2012.

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