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Astronomers spot giant stream of stars between galaxies

To their surprise, an international team of researchers has discovered a giant and extremely faint stream of stars between galaxies. While streams are already known in our own galaxy and in nearby galaxies, this is the first ...

JWST reveals protoplanetary disks in a nearby star cluster

The Orion Nebula is a favorite among stargazers. It's a giant stellar nebula out of which, hot young stars are forming. Telescopically to the eye it appears as a gray/green haze of wonderment but cameras reveal the true glory ...

Astronomers discover the Milky Way's faintest satellite

By analyzing the images from the Ultraviolet Near Infrared Optical Northern Survey (UNIONS), an international team of astronomers has discovered a new compact satellite of the Milky Way, which received designation Ursa Major ...

FIRST discovery of dozens of new giant radio galaxies

Astronomers from the University of Wisconsin-Madison and elsewhere report the discovery of 63 new giant radio galaxies as part of the Faint Images of the Radio Sky at Twenty cm survey (FIRST). The findings are detailed in ...

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A light-year or light year (symbol: ly) is a unit of length, equal to just under 1013 kilometres. As defined by the International Astronomical Union (IAU), a light-year is the distance that light travels in a vacuum in one Julian year.

The light-year is often used to measure distances to stars and other distances on a galactic scale, especially in non-specialist and popular science publications. The preferred unit in astrometry is the parsec, because it can be more easily derived from, and compared with, observational data. The parsec is defined as the distance at which an object will appear to move one arcsecond of parallax when the observer moves one astronomical unit perpendicular to the line of sight to the observer, and is equal to approximately 3.26 light-years.

The related unit of the light-month, roughly one-twelfth of a light-year, is also used occasionally for approximate measures.

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