Lovers of stargazing and reading delightful stories about distant planets must have paid attention to the distance to them, expressed either in parsecs or in light years.
How many kilometers is it? Why did such units of measurement appear and how are they calculated?
Entertaining astronomy The distance from our planet to the Moon is 384 thousand km, to the Sun – 150 million km, to Neptune – 4.6 billion km.
Within our solar system, such numbers are relatively understandable and readable. However, what if you look further?
The distance from Earth to Betelgeuse, a bright star in the constellation Orion, which intends to explode, reaches 8 quadrillion km. This is a digit followed by 15 zeros.
The farthest galaxy from us is UDFj. She was discovered in 2011. The distance to it is impossible to imagine. It is 13 billion times farther than Betelgeuse. It is practically impossible to write such a figure on paper and try to carry out mathematical calculations.
Therefore, scientists have come up with 3 quantities – an astronomical unit, a light year and a parsec. They express cosmic distances more clearly and are more convenient in calculations.
Astronomical unit (AU) The value is equal to the radius of the Earth’s orbit around the Sun.
Given that our orbit is elliptical, and not perfectly round, then the average distance from the planet’s surface to the surface of the star is taken. These are the same 150 million km. A more accurate value is 149,597,870,700 meters.
This unit is used when considering relatively small astronomical distances.
Light year This is the distance traveled by a ray of light in a year.
In a second, the light travels 300 thousand km (exactly 299 792 km). This is an absolute value. Nobody and nothing can move faster.
In kilometers, the light year is 9,460,730,472,580. In astronomical units – 63241.
For comparison, the distance to the nearest star Proxima Centauri is 4.2 light years – 39,735,067,984,836 km.
The further the distance to the star, the older it is for us. We see every star in the night sky in the form in which it was many thousands of years ago.
Parsecs Distance to an object, equal to the annual trigonometric parallax (displacement of the object) per arc second.
If we imagine a right-angled triangle, where one leg is equal to one astronomical unit, and the opposite angle is equal to one arc second (1 ° divided by 3600), then the second leg will just be equal to one parsec.
One parsec is equal to about 3.2 light years, 206 thousand AU. or 30,274,337,512,256 km.