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

Solved: The mystery of the expansion of the universe

The Earth, solar system, the entire Milky Way and the few thousand galaxies closest to us move in a vast "bubble" that is 250 million light years in diameter, where the average density of matter is half as high as for the ...

A new Einstein cross is discovered

This study, which has combined images from the Hubble Space Telescope with spectroscopic observations from the GTC, has confirmed the existence of a new example of a gravitational lens, a phenomenon predicted by Albert Einstein's ...

How big is the universe?

Our brains struggle to comprehend how big the universe is because everything here on Earth, and even the Earth itself, is very small when compared to the immense scale of the universe.

Black hole fails to do its job

Astronomers have discovered what can happen when a giant black hole does not intervene in the life of a galaxy cluster. Using NASA's Chandra X-ray Observatory and other telescopes they have shown that passive black hole behavior ...

Astronomers detect galactic space laser

A powerful radio-wave laser, called a "megamaser", has been observed by the MeerKAT telescope in South Africa. The record-breaking find is the most distant megamaser of its kind ever detected, at about five billion light ...

Where is the closest black hole?

You know that saying, "keep your friends close, but keep your enemies closer?" That advice needs to go right out the window when we're talking black holes. They're the worst enemies you could have and you want them as far ...

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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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