| Observation data Epoch J2000.0 Equinox J2000.0 | |
|---|---|
| Constellation | Andromeda |
| Right ascension | 01h 09m 43.91s |
| Declination | +35° 37′ 13.8″ |
| Apparent magnitude (V) | 2.01 to 2.10 |
| Characteristics | |
| Evolutionary stage | Red giant |
| Spectral type | M0 III |
| Variable type | Semiregular variable |
| Astrometry | |
| Parallax (π) | 16.52 ± 0.56 mas |
| Distance | 197 ± 7 ly (61 ± 2 pc) |
| Details | |
| Mass | 2.49 M☉ |
| Radius | 86.4 R☉ |
| Luminosity | 1,675 L☉ |
| Temperature | 3,762 ± 40 K |
| Age | 500 million-1 billion years |
| Other designations | |
Mirach, Beta Andromedae, Beta And, β And, 43 Andromedae, 43 And, HD 6860, HIP 5447, HR 337 | |
Beta Andromedae (β And), also called Mirach, is a star in the constellation of Andromeda. It is the second-brightest star in the constellation and is easy to see without using a telescope. People often use it as a guide star to find the Andromeda Galaxy. Its brightness changes slightly over time. It is a semiregular variable star, with an apparent magnitude that shifts between 2.01 and 2.10. It is located at around 197 light-years away from the Solar System.
Mirach is a red giant star, with a radius 86.4 times that of the Sun. It was once a star like the Sun, but it depleted the hydrogen fuel in its core. Even though the star's surface is cooler than the Sun, it shines 1,675 times more brighter because of its size.
In 2023, astronomers found out that this star has a substellar companion (likely a brown dwarf) orbiting it, using the radial velocity method. It orbits the star every 4.3 years.
