Blueshift

blue shiftblue-shiftedblue-shiftblueshiftedBlue-shiftedvioletviolet-shifted
A blueshift is any decrease in wavelength, with a corresponding increase in frequency, of an electromagnetic wave; the opposite effect is referred to as redshift.wikipedia
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Redshift

red shiftzred-shift
A blueshift is any decrease in wavelength, with a corresponding increase in frequency, of an electromagnetic wave; the opposite effect is referred to as redshift.
The opposite of a redshift is a blueshift, where wavelengths shorten and energy increases.

Doppler effect

Dopplerdoppler shiftDoppler shifts
Doppler blueshift is caused by movement of a source towards the observer.
The Doppler effect for electromagnetic waves such as light is of great use in astronomy and results in either a so-called redshift or blueshift.

Barnard's Star

Barnard’s Starextrasolar planets
Nearby stars such as Barnard's Star are moving toward us, resulting in a very small blueshift.
The radial velocity of Barnard's Star towards the Sun is measured from its blueshift to be −110 km/s.

Andromeda Galaxy

AndromedaM31Andromeda Nebula
The Andromeda Galaxy is moving toward our own Milky Way galaxy within the Local Group; thus, when observed from Earth, its light is undergoing a blueshift.
This makes the Andromeda Galaxy one of about 100 observable blueshifted galaxies.

Visible spectrum

visiblevisible lightspectrum
The term applies to any decrease in wavelength and increase in frequency caused by relative motion, even outside the visible spectrum.
The shifting of spectral lines can be used to measure the Doppler shift (red shift or blue shift) of distant objects.

Relativistic Doppler effect

transverse Doppler effectDoppler effectDoppler effect for electromagnetic waves
Relativistic Doppler effect
Astronomers know of three sources of redshift/blueshift: Doppler shifts; gravitational redshifts (due to light exiting a gravitational field); and cosmological expansion (where space itself stretches).

Mass–energy equivalence

mass-energy equivalencemass-energymass–energy
It is a natural consequence of conservation of energy and mass–energy equivalence, and was confirmed experimentally in 1959 with the Pound–Rebka experiment.
to the left, the pulse moving to the left is redshifted, while the pulse moving to the right is blue shifted.

Wavelength

wavelengthsperiodsubwavelength
A blueshift is any decrease in wavelength, with a corresponding increase in frequency, of an electromagnetic wave; the opposite effect is referred to as redshift.

Electromagnetic radiation

electromagnetic waveelectromagnetic waveselectromagnetic
A blueshift is any decrease in wavelength, with a corresponding increase in frequency, of an electromagnetic wave; the opposite effect is referred to as redshift.

Light

visible lightvisiblelight source
In visible light, this shifts the color from the red end of the spectrum to the blue end.

Naked eye

naked-eyeunaided eyenaked human eye
Only objects moving at near-relativistic speeds toward the observer are noticeably bluer to the naked eye, but the wavelength of any reflected or emitted photon or other particle is shortened in the direction of travel.

Astronomy

astronomicalastronomerastronomers
Doppler blueshift is used in astronomy to determine relative motion:

Milky Way

galaxyMilky Way Galaxyour galaxy
The Andromeda Galaxy is moving toward our own Milky Way galaxy within the Local Group; thus, when observed from Earth, its light is undergoing a blueshift.

Galaxy

galaxiesgalacticgalactic nuclei
The Andromeda Galaxy is moving toward our own Milky Way galaxy within the Local Group; thus, when observed from Earth, its light is undergoing a blueshift.

Local Group

LGList of galaxies in the Local Grouplocal galactic neighborhood
The Andromeda Galaxy is moving toward our own Milky Way galaxy within the Local Group; thus, when observed from Earth, its light is undergoing a blueshift.

Binary star

spectroscopic binaryeclipsing binarybinary
Components of a binary star system will be blueshifted when moving towards Earth

Tully–Fisher relation

TF relationTully-Fisher RelationTully–Fisher
When observing spiral galaxies, the side spinning toward us will have a slight blueshift relative to the side spinning away from us (see Tully–Fisher relation).

Blazar

blazars
Blazars are known to propel relativistic jets toward us, emitting synchrotron radiation and bremsstrahlung that appears blueshifted.

Astrophysical jet

relativistic jetjetsjet
Blazars are known to propel relativistic jets toward us, emitting synchrotron radiation and bremsstrahlung that appears blueshifted.

Synchrotron radiation

synchrotron lightsynchrotron emissionsynchrotron
Blazars are known to propel relativistic jets toward us, emitting synchrotron radiation and bremsstrahlung that appears blueshifted.

Bremsstrahlung

bremsstrahlung radiationfree-free emissionbraking radiation
Blazars are known to propel relativistic jets toward us, emitting synchrotron radiation and bremsstrahlung that appears blueshifted.

Conservation of energy

law of conservation of energyenergyenergy conservation law
It is a natural consequence of conservation of energy and mass–energy equivalence, and was confirmed experimentally in 1959 with the Pound–Rebka experiment.

Pound–Rebka experiment

first successful laboratory measurementPound & Rebka (1959)Pound and Rebka
It is a natural consequence of conservation of energy and mass–energy equivalence, and was confirmed experimentally in 1959 with the Pound–Rebka experiment.

Cosmic microwave background

cosmic microwave background radiationmicrowave background radiationCMB
Gravitational blueshift contributes to cosmic microwave background (CMB) anisotropy via the Sachs–Wolfe effect: when a gravitational well evolves while a photon is passing, the amount of blueshift on approach will differ from the amount of gravitational redshift as it leaves the region.

Sachs–Wolfe effect

integrated Sachs–Wolfe effectIntegrated Sachs–Wolfe effect (ISW)Rees-Sciama effect
Gravitational blueshift contributes to cosmic microwave background (CMB) anisotropy via the Sachs–Wolfe effect: when a gravitational well evolves while a photon is passing, the amount of blueshift on approach will differ from the amount of gravitational redshift as it leaves the region.