Radiation astronomy/Wavelength shifts

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Absorption lines in the visible spectrum of a supercluster of distant galaxies (right), are compared to absorption lines in the visible spectrum of the Sun (left). Arrows indicate redshift. Wavelength increases up towards the red and beyond (frequency decreases). Credit: Dr. Schorsch and Kes47.

"Ideally all intrinsic colours should be found from unreddened stars. This is possible for dwarf and giant stars later than about A0 (Johnson, 1964) ... However, it cannot be used for stars of other spectral classes since they are all relatively infrequent in space, and generally reddened."[1]

Redshift happens when light seen coming from an object that is moving away is proportionally increased in wavelength, or shifted to the red end of the visible spectrum. More generally, where an observer detects electromagnetic radiation outside the visible spectrum, "redder" amounts to a technical shorthand for "increase in electromagnetic wavelength" — which also implies lower frequency and photon energy in accord with, respectively, the wave and quantum theories of light. Redshifts are attributable to the Doppler effect, familiar in the changes in the apparent pitches of sirens and frequency of the sound waves emitted by speeding vehicles; an observed redshift due to the Doppler effect occurs whenever a light source moves away from an observer.

Cosmological redshifts[edit | edit source]

Cosmological redshift is seen due to the expansion of the universe, and sufficiently distant light sources (generally more than a few million light years away) show redshift corresponding to the rate of increase of their distance from Earth.

Gravitational redshifts[edit | edit source]

Gravitational redshifts are a relativistic effect observed in electromagnetic radiation moving out of gravitational fields.

Blue shifts[edit | edit source]

A decrease in wavelength is called blueshift and is generally seen when a light-emitting object moves toward an observer or when electromagnetic radiation moves into a gravitational field.

Hypotheses[edit | edit source]

  1. The use of satellites should provide ten times the information as sounding rockets or balloons.

A control group for a radiation satellite would contain

  1. a radiation astronomy telescope,
  2. a two-way communication system,
  3. a positional locator,
  4. an orientation propulsion system, and
  5. power supplies and energy sources for all components.

A control group for radiation astronomy satellites may include an ideal or rigorously stable orbit so that the satellite observes the radiation at or to a much higher resolution than an Earth-based ground-level observatory is capable of.

See also[edit | edit source]

References[edit | edit source]

  1. M. Pim FitzGerald (February 1970). "The Intrinsic Colours of Stars and Two-Colour Reddening Lines". Astronomy and Astrophysics 4 (2): 234-43. 

External links[edit | edit source]

{{Radiation astronomy resources}}{{Repellor vehicle}}