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BT Ursae Majoris
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Star BT Ursae Majoris

Red dwarf BT Ursae Majoris is located 79 light years away from the Sun. It is a single flare star of spectral class M4.05, that has typically about 25 % of solar mass. For now, there are no known exoplanets in this star system.
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Sun distance
79 light years
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BT Ursae Majoris

Red dwarf, flare star
Spectral class: M4.05

Location +

Ascension iconRight ascension: 11h 30m 53.728s
Declination iconDeclination: 44° 14' 37.882'' (northern hemisphere)
Parallax iconParallax: 41.392
Distance iconSun distance: 78.797 ly | 24.2 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: 20 % M Sun
| 251.4 M Jupiter
 (estimate)
+
Star mass
The mass of the star BT Ursae Majoris is unknown. Based on its other characteristics, it is estimated to be about 20 % 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: 40 % R Sun
| 3.9 R Jupiter
(estimate)
+
Star size
Radius of the star BT Ursae Majoris is not known. Its estimated value based on other similar stars is about 40 % 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: 3200 K
 (estimate)
+
Star temperature
Surface temperature of BT Ursae Majoris is estimated to be 3215 K, which is 55 % 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

Magnitude iconApparent magnitude (V): 13.7
Magnitude iconAbsolute magnitude (V): 11.8
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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BT Ursae Majoris system structure

 BT Ursae Majoris

More about BT Ursae Majoris

       BT Ursae Majoris can be found in northern celestial hemisphere, however it is too dim to be seen with the naked eye or even a small telescope.
Other designations of this star
V* BT UMa, Gaia EDR3 772320886023525504
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External sources
simbad icon
Simbad database (V* BT UMa)
Astronomical database SIMBAD (the Set of Identifications, Measurements and Bibliography for Astronomical Data)
gaia icon
Gaia database (Gaia EDR3 772320886023525504)
Archive from the Gaia mission

Frequently Asked Questions

How far is the BT Ursae Majoris system from the Sun?

The BT Ursae Majoris system is 79 light years or 24.2 parsecs from the Sun.

What galaxy is the BT Ursae Majoris star in?

The BT Ursae Majoris is in the Milky Way galaxy just like the Sun.

How many stars are in the BT Ursae Majoris system?

The BT Ursae Majoris is a single star, there are no other known stars in the system.

What type of star is the BT Ursae Majoris?

The star BT Ursae Majoris is a Red dwarf star.

What temperature is the BT Ursae Majoris?

The primary in the BT Ursae Majoris system has an effective temperature of K ( °C). Find out more about the temperature of stars in Stellar guide
Class of stars Red dwarf
Red dwarfs are small, cool stars with surface temperatures of about 2,000–3,800 K, much cooler than the Sun. They usually have 8–50% of the Sun’s mass and shine very faintly, sometimes at just a tiny fraction of the Sun’s brightness. Classified mainly as spectral type M, they are the most common stars in the Milky Way, making up roughly 70–75% of its stellar population.

They fuse hydrogen slowly through the proton–proton chain and are fully convective, which allows them to use their fuel very efficiently. As a result, red dwarfs can live for tens of billions to trillions of years—far longer than the Sun. Many exoplanets orbit red dwarfs, including some in close habitable zones, though strong stellar activity can affect planetary environments.
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