Digital Universe Guide - Hayden Planetarium

Appendix D
Electromagnetic Spectrum
The entirety of light, or radiation, in the Universe spans more than just the light we see with our eyes.
This continuous range of light is called the electromagnetic (EM) spectrum and includes radiation at
every frequency or wavelength. The EM spectrum has been broken into regions (see Table D.1) ranging
from the highest-energy gamma rays to the lowest-energy radio waves.
Table D.1 – Regions of the electromagnetic spectrum. Ranges are expressed
as wavelengths (in meters) and frequencies (in Hertz). The corresponding
blackbody temperature is the average over the range
(or the upper or lower limit) and is in Kelvin.
Region Wavelengths (m) Frequencies (Hz) Temperature (K)
Radio > 1 × 10 −1 < 3 × 10 9 < 0.029
Microwave 1 × 10 −3 to 1 × 10 −1
3 × 10 9 to 3 × 10 11
2.9 − 0.029
Infrared 7 × 10 −7 to 1 × 10 −3
3 × 10 11 to 4 × 10 14
4,140 − 2.9
Visible 4 × 10 −7 to 7 × 10 −7
4 × 10 14 to 7 × 10 14
7,245 − 4,140
Ultraviolet 1 × 10 −8 to 4 × 10 −7
7 × 10 14 to 3 × 10 16
290,000 − 7,245
X-ray 1 × 10 −11 to 1 × 10 −8
3 × 10 16 to 3 × 10 19
290,000,000 − 290,000
Gamma-ray < 1 × 10 −11 > 3 × 10 19 > 290,000,000
In addition to its usefulness in astronomy, each region of the EM spectrum is important for everyday
uses as well. On the high-energy side of the EM spectrum, we use gamma rays to power nuclear
reactors and for medical testing involving radioactive isotopes. In space we observe gamma-ray bursts.
These result from a collision between a black hole and a neutron star and produce enough energy that
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