what is LIGHT YEARS ?
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| An image of the Andromeda galaxy, as seen by NASA's GALEX observatory. Credit: NASA/JPL-Caltech |
The LIGHT- YEAR is
a unit of length used to express astronomical distances and measure about 9.46
trillion kilometres ( 3,00,000 x 60 x 60 x 24 x 365 = 9.46 x 1012
km ) or 5.88 trillion miles ( 5.88 x 1012 mi )
As defined by the International
astronomical union (IAU) ,
“ A Light year is the distance
that light travels in vacuum in one Julian year(365.25 days).”
How many light years away
?
Earth is approximately …..
- 8.3 light-minutes from the sun
- 4.3
light-years away from proxima Centauri, our closest neighbouring star
- 320
light-years from the North star, Polaris
- 26000
light-years away from the centre of our galaxy , milky-way
- 2.5
million light-years from Andromeda , our closest neighbouring galaxy.
- 13.4
billion light-years away from one of the oldest galaxies ever found , called GN-z11
Why use light years?
Measuring in light-years allows
astronomers to determine how far back in time they are viewing .Because light
takes time to travel to our eyes ,everything we view in the night sky has
already happened . In otherwords ,when you observe something 1 light years away
, you see it appeared exactly one years ago.
Read also :
HOW LONG WOULD IT TAKE TO REACH THESE , IF WE TRAVEL IN THE SPEED OF LIGHT ? 👇🏼
source : Wikipedia
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