What is a star?
A star is a huge, self-luminous ball of gas in whose core hydrogen fuses into helium. Our Sun is a star, too. The colour reveals the temperature: bluish stars are hotter than 10,000 °C, reddish ones “only” around 3,000 °C.
Star knowledge
Star knowledge
A few basics to help you understand your star better – and find it in the sky.
Apparent brightness (magnitude)
Astronomers measure brightness in magnitudes (mag). The smaller the number, the brighter the star: Sirius is −1.4 mag; the faintest stars still visible to the naked eye under a dark sky are about 6.5 mag. All stars at Sternschenker are within this visible range.
Constellations
The IAU divides the sky into 88 constellations with fixed borders. Every star belongs to exactly one of them. The twelve classical constellations along the Sun’s path form the zodiac – that’s where the zodiac signs come from. In fact, the Sun also passes through a thirteenth, Ophiuchus.
Coordinates in the sky
Much like longitude and latitude on Earth, the sky uses right ascension (RA) and declination (Dec). With these two values every star can be located precisely.
Catalogue numbers
From 1989 to 1993 ESA’s Hipparcos satellite measured more than 118,000 stars. The Hipparcos number (HIP) on your certificate identifies your star unambiguously.
Light years
A light year is the distance light travels in one year – about 9.46 trillion kilometres. The light of your star may have set off hundreds of years ago.
Constellations
Zodiac signs
Brightest stars
Glossary