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Alcor
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Star Alcor

Binary star Alcor is located 81 light years away from the Sun. It consists of a white-blue star and a red dwarf. For now, there are no known exoplanets in this star system.
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Sun distance
81 light years
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Alcor A

White-Blue star
Spectral class: A5V

Location +

Ascension iconRight ascension: 13h 25m 13.756s
Declination iconDeclination: 54° 59' 16.243'' (northern hemisphere)
Parallax iconParallax: 40.465
Distance iconSun distance: 80.602 ly | 24.7 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: 184 % M Sun
| 1928 M Jupiter
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Star mass
Mass of the star Alcor A is 1.84 solar masses.

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: 185 % R Sun
| 18.4 R Jupiter
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Star size
Radius of the star Alcor A is 1.846 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 icon
Temperature: 8221 K | 1.42 T Sun
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Star temperature
Surface temperature of Alcor A is 8221 K, which is 142 % 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
luminosity icon
Luminosity: 14.03 L Sun
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Star luminosity
Luminosity is the total amount of energy a star gives off every second. Think of it as the star’s true brightness — not just how bright it looks from Earth. This is important because some stars may appear dim simply because they are far away, not because they’re actually faint... icon More about Star luminosity in StellarGuide

Photometry

Magnitude iconApparent magnitude (V): 4
Magnitude iconAbsolute magnitude (V): 2
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

Alcor B

Red dwarf
Spectral class: M3-4V

Basic characteristic

icon weight
Mass: 25 % M Sun
| 262 M Jupiter
+
Star mass
Mass of the star Alcor B is 1.84 solar masses.

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: 30 % R Sun
| 2.8 R Jupiter
(estimate)
+
Star size
Radius of the star Alcor B is not known. Its estimated value based on other similar stars is about 30 % 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: 3300 K
 (estimate)
+
Star temperature
Surface temperature of Alcor B is estimated to be 3341 K, which is 57 % 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
time icon
Age: 0.5 billions years | 0.11 Sun
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Star age
Star Alcor B is 0.5 billion years old, which is about 0.11 of the Sun's age.

The age of a star tells us how long it has been shining since it formed. Knowing a star’s age helps astronomers understand its life stage, how it has changed over time, and what will happen to it in the future... icon More about Star age 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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Alcor system structure

 Alcor A
Alcor B

More about Alcor

       Alcor 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
g UMa, g Ursae Majoris, 80 Ursae Majoris, BD+55 1603, CCDM J13240+5456D, GC 18155, HD 116842, HIP 65477, HR 5062, PPM 34021, SAO 28751, WDS J13239+5456C, Gaia EDR3 1565090003967879424
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Frequently Asked Questions

How far is the Alcor system from the Sun?

The Alcor system is 81 light years or 24.7 parsecs from the Sun.

What galaxy is the Alcor star in?

The Alcor is in the Milky Way galaxy just like the Sun.

How many stars are in the Alcor system?

The Alcor system contains 2 stars.

What type of star is the Alcor?

The primary in the Alcor system is a White-Blue star star.

What temperature is star Alcor?

The primary in the Alcor system has a temperature of 8221 K. Find out more about the temperature of stars in Stellar guide
Closest stars

 Zeta1 Ursae Majoris Aa
 2.2 M☉ 0.6 ly

HD 115043
 - 3.7 ly

HD 119332
 - 4.7 ly

G 199-69
 - 4.8 ly

PG 1344+573
 - 5.1 ly
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