Related topics: galaxies · stars · black holes · nasa · astronomers

Galactic crash may have triggered solar system formation

The formation of the Sun, the Solar System and the subsequent emergence of life on Earth may be a consequence of a collision between our galaxy, the Milky Way, and a smaller galaxy called Sagittarius, discovered in the 1990s ...

Ultra-diffuse galaxy VCC 1287 investigated in detail

Astronomers have probed an ultra-diffuse galaxy (UDG) known as VCC 1287 with the Keck Cosmic Web Imager (KCWI) in order to investigate its nature. The new results provide essential information about the galaxy's mass and ...

Abell 2384: Bending the bridge between two galaxy clusters

Several hundred million years ago, two galaxy clusters collided and then passed through each other. This mighty event released a flood of hot gas from each galaxy cluster that formed an unusual bridge between the two objects. ...

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Light-year

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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