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21 Pegasi
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Star 21 Pegasi

Blue-white star 21 Pegasi is located 706 light years away from the Sun. It is a single star of spectral class B9.5, that has typically about 500 % of solar mass. For now, there are no known exoplanets in this star system.
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Sun distance
706 light years
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21 Pegasi

Blue-white star
Spectral class: B9.5

Location +

Ascension iconRight ascension: 22h 3m 19.054s
Declination iconDeclination: 11° 23' 11.529'' (equatorial region)
Parallax iconParallax: 4.620
Distance iconSun distance: 705.934 ly | 216.4 pc
Star position
The position of a star tells us where it appears in the sky, similar to how we use coordinates like latitude and longitude on Earth. In astronomy, the three main coordinates are right ascension, declination and distance. .. icon More about Star position in StellarGuide

Basic characteristic

icon weight
Mass: 340 % M Sun
| 3603.6 M Jupiter
 (estimate)
+
Star mass
The mass of the star 21 Pegasi is unknown. Based on its other characteristics, it is estimated to be about 340 % of the Sun's mass.

The mass of a star is the total amount of matter it contains. It is one of the most important properties of a star, as it determines almost everything about how the star lives, changes, and dies. In astronomy, star mass is usually measured in solar masses (M☉) — where 1 solar mass is equal to the mass of our Sun... icon More about Star mass in StellarGuide
radius icon
Size: 270 % R Sun
| 27 R Jupiter
(estimate)
+
Star size
Radius of the star 21 Pegasi is not known. Its estimated value based on other similar stars is about 270 % solar radii.

The size of a star refers to its radius — the distance from its center to its surface. Star size is usually measured in solar radii (R☉), where 1 solar radius equals approximately 696,000 kilometers. Depending on their type and life stage, stars can be much smaller or larger than the Sun... icon More about Star size in StellarGuide
temperature iconTemperature: 11800 K
 (estimate)
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Star temperature
Surface temperature of 21 Pegasi is estimated to be 11768 K, which is 204 % of the temperature on the surface of the Sun.

The temperature of a star refers to the temperature at its surface, also called the photosphere. It is measured in kelvins (K), the standard unit for temperature in astronomy. A star’s temperature tells us a lot about its physical properties and where it stands in its evolutionary stage... icon More about Star temperature in StellarGuide

Photometry

Absolute stellar magnitude in different parts of the electromagnetic spectrum from infrared (K band) to ultraviolet (U band).
5
10
15
20
25
30
35
K
2.1
H
1.6
J
1.2
Grp
0.8
I
0.8
G
0.6
V
0.5
Gbp
0.5
B
0.4
U
0.3
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21 Pegasi system structure

 21 Pegasi

More about 21 Pegasi

Star 21 Pegasi is a main sequence star that fuses hydrogen atoms into helium. 
       21 Pegasi can be found in northern celestial hemisphere, and it is possible to see it with naked eye. The star is easily observable from Northern America, Europe and Asia.
Other designations of this star
21 Peg, Gaia DR3 2728099321601525504
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External sources
icon study
Detectability of deuterium in spectra of early-type stars
Scientific study, Accepted: 16. 06. 2026
gaia icon
Gaia database (Gaia DR3 2728099321601525504)
Archive from the Gaia mission

Frequently Asked Questions

How far is the 21 Pegasi system from the Sun?

The 21 Pegasi system is 706 light years or 216.4 parsecs from the Sun.

What galaxy is the 21 Pegasi star in?

The 21 Pegasi is in the Milky Way galaxy just like the Sun.

How many stars are in the 21 Pegasi system?

The 21 Pegasi is a single star, there are no other known stars in the system.

What type of star is the 21 Pegasi?

The star 21 Pegasi is a Blue-white star star.

What temperature is the 21 Pegasi?

The primary in the 21 Pegasi system has an effective temperature of K ( °C). Find out more about the temperature of stars in Stellar guide
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Estimated values
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