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Q 'n A
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Q. What is the age of starlight?
I was told that the light we see from stars is actually 5,000 years old due to the distance light has to travel to reach us. Is there any validity to this? — Brendan O.
A. No, except when the star is 5,000 lightyears from Earth.
A lightyear is a measure of distance. It's how far light travels in a year at about 186,000 miles per second. That is, about 5.87 trillion miles.
The star nearest our Solar System, Proxima Centauri, is about four lightyears away. The light traveling from Proxima Centauri to Earth takes about four years to get here. Thus, the light is four years old when we see it.
Another nearby star is Barnard's Star, which is six lightyears from Earth. It's light takes six years to get here, so that light is six years old when we see it.
The star Polaris, which we refer to as the North Star or North Pole Star, is 680 lightyears away. The light takes 680 years to travel to Earth, so it is 680 years old when we see it.
Hubble Space Telescope recorded this image in 1995 of the star forming region of the Universe known as the Lagoon Nebula (M8). It is some 5,000 lightyears from Earth. The explosive energy from starbirth in and around the nebula bombards the dusty clouds of cool gas producing the intense starlight seen from Earth. The light that reaches Earth is 5,000 years old. That's one of the hot young stars at lower right.
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Most of the stars we see with the naked eye at night are within a few hundred lightyears, although a handful are as far away as 2,000 lightyears.
We don't see stars 5,000 lightyears away with the naked eye.
Viewing the light from stars more than about 2,000 lightyears away requires the use of a telescope.
The most distant objects seen from Earth are quasars, Telescopes are required to view them. They are 10-15 billion lightyears away. Their light takes 10-15 billion years to reach Earth, so their light is 10-15 billion years old.
An example of an object 5,000 lightyears away from Earth is the Lagoon Nebula, also known as M8. A nebula is a cloud of dust and gas in space, usually illuminated by one or more stars. Nebulae represent the raw material of which stars are made.
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