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

Center of the Coma cluster explored with AstroSat

Using India's AstroSat spacecraft, astronomers have investigated a central field of a cluster of galaxies known as the Coma cluster. Results of the study, presented in a paper published September 13 on, deliver ...

It's a planet: New evidence of baby planet in the making

Astronomers agree that planets are born in protoplanetary disks—rings of dust and gas that surround young, newborn stars. While hundreds of these disks have been spotted throughout the universe, observations of actual planetary ...

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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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