The constellations are hundreds or thousands of light years away from each other. Constellations are made up of several stars and as they are not in a plane, each star is at a different distance from a fixed point, even if they belong to the same constellation.
The closest star to the Sun is Alpa Centauri, which is at a distance of 4.37 light years, which is equivalent to 41.3 trillion kilometers.
Alpa Centauri belongs to the constellation Centaurus, which is formed by a system of 3 stars linked gravitationally: Alpa Centauri; Alpa Centauri B and Proxima Centauri.
One of the best known constellations is Orion. In Orion there are several of the brightest stars that are observed from the earth. These stars are located at a distance ranging from 243 to 1,360 light years.
Orion's brightest star is Rigel, which is 51,000 times brighter than the Sun, and is 777 light years distant.
For its part, the closest star is Bellatrix, which is 243 light years away and is 6000 times more luminous than the Sun.
Almost all the stars in the constellations are within a radius of no more than 1000 light years from each other.
Organization of the constellations in the sky
In the modern era the galaxy is organized into 88 constellations, the area they cover in the sky is measured in square degrees.
Eugène Delporte was the one who drew the limits with imaginary horizontal and vertical lines using the earth as a reference in 1875.
The definitive limits between the constellations were established in 1930 by the International Astronomical Union, this is how each star is within the limits of a constellation.
Astronomers study well-defined areas in the sky more than the shapes that stars make of one another.
Ways to measure distances in the sky
Space is so large that it tends to be infinite, so it is almost impossible to measure it in miles or kilometers. This has led to the emergence of special systems to measure the distances of the universe.
The metric systems used to calculate distances in the universe are:
- Astronomical unit (ua). Average distance between the Earth and the Sun. 149,600,000 km.
- Light-year. Distance that light travels in a year. 9.46 billion km or 63,235.3 ua.
- Pársec (parallax-second). Distance of a body that has a parallax of 2 arc segments. 30.86 billion km, 3.26 light years or 206,265 ua.
The astronomical unit is only used to measure the distances between the Sun and the Earth. It is not used outside of our solar system.
For its part, the speed of light is calculated at a rate of 300,000 kilometers per second and in parallax the angle formed between the star and the Earth is measured at the two opposite points of their orbit around the Sun.
References
- Payne Nick (2012) Constellations. London, UK: Faber & Faber.
- Delporte Eugéne (1930) Délimitation scientifique des constellations (tables et cartes). Cambridge, UK: At University Press.
- Bakich Michael (1995) The Cambridge Guide to the Constellations. Cambridge, UK: AT University Press
- Constellation Guide (2017) The University of Texas McDonald Observatory retrieved from stardate.org
- Welcome to the Sun's Neighborhood (2014) Jet Propulsion Laboratory retrieved from nasa.gov.