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Zeta1 Ursae Majoris Aa
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Star Zeta1 Ursae Majoris Aa

Multiple star system Zeta1 Ursae Majoris Aa is located 81 light years away from the Sun. It is a system with 4 stars. For now, there are no known exoplanets in this star system.
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Sun distance
81 light years
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Zeta1 Ursae Majoris Aa

White-Blue star, Spectroscopic binary
Spectral class: A1.5Vas

Location +

Ascension iconRight ascension: 13h 23m 55.779s
Declination iconDeclination: 54° 55' 30.933'' (northern hemisphere)
Parallax iconParallax: 40.213
Distance iconSun distance: 81.107 ly | 24.9 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: 222.2 % M Sun
| 2328 M Jupiter
+
Star mass
Mass of the star Zeta1 Ursae Majoris Aa is 2.2224 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: 240 % R Sun
| 23.9 R Jupiter
+
Star size
Radius of the star Zeta1 Ursae Majoris Aa is 2.4 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: 9000 K | 1.56 T Sun
+
Star temperature
Surface temperature of Zeta1 Ursae Majoris Aa is 9000 K, which is 156 % 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: 0.370 billions years | 0.08 Sun
+
Star age
Star Zeta1 Ursae Majoris Aa is 0.370 billion years old, which is about 0.08 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
luminosity icon
Luminosity: 33.3 L Sun
+
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): 2.2
Magnitude iconAbsolute magnitude (V): 0.2
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

Zeta1 Ursae Majoris Ab

White-Blue star, , Spectroscopic binary
Spectral class: A2Vp

Basic characteristic

icon weight
Mass: 223.8 % M Sun
| 2345 M Jupiter
+
Star mass
Mass of the star Zeta1 Ursae Majoris Ab is 2.2224 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: 240 % R Sun
| 23.9 R Jupiter
+
Star size
Radius of the star Zeta1 Ursae Majoris Ab is 2.4 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: 9000 K | 1.56 T Sun
+
Star temperature
Surface temperature of Zeta1 Ursae Majoris Ab is 9000 K, which is 156 % 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: 33.3 L Sun
+
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

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

Zeta2 Ursae Majoris A

White-Blue star, Spectroscopic binary
Spectral class: kA1h(eA)mA7IV-V

Basic characteristic

icon weight
Mass: 210 % M Sun
| 2199.9 M Jupiter
 (estimate)
+
Star mass
The mass of the star Zeta2 Ursae Majoris A is unknown. Based on its other characteristics, it is estimated to be about 210 % 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: 470 % R Sun
| 46.3 R Jupiter
(estimate)
+
Star size
Radius of the star Zeta2 Ursae Majoris A is not known. Its estimated value based on other similar stars is about 470 % 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: 8425 K | 1.46 T Sun
+
Star temperature
Surface temperature of Zeta2 Ursae Majoris A is 8425 K, which is 146 % 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): 3.9
Magnitude iconAbsolute magnitude (V): 1.9
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

Zeta2 Ursae Majoris B

Orange star, , Spectroscopic binary

Basic characteristic

temperature iconTemperature: 8100 K
 (estimate)
+
Star temperature
Surface temperature of Zeta2 Ursae Majoris B is estimated to be 8113 K, which is 140 % 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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Zeta1 Ursae Majoris Aa system structure

 Zeta1 Ursae Majoris Aa
Zeta1 Ursae Majoris Ab
Zeta2 Ursae Majoris A
Zeta2 Ursae Majoris B

More about Zeta1 Ursae Majoris Aa

       Zeta1 Ursae Majoris Aa 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
Mizar, ζ Ursae Majoris, ζ UMa, Zeta UMa, 79 Ursae Majoris, BD+55 1598, CCDM J13240+5456, HIP 65378, WDS J13239+5456, ζ1 UMa, GC 18133, HD 116656, HR 5054, PPM 34007, SAO 28737, ζ2 Ursae Majoris, GC 18134, HD 116657, HR 5055, SAO 28738, Gaia EDR3 1563590579347125632
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Frequently Asked Questions

How far is the Zeta1 Ursae Majoris Aa system from the Sun?

The Zeta1 Ursae Majoris Aa system is 81 light years or 24.9 parsecs from the Sun.

What galaxy is the Zeta1 Ursae Majoris Aa star in?

The Zeta1 Ursae Majoris Aa is in the Milky Way galaxy just like the Sun.

How many stars are in the Zeta1 Ursae Majoris Aa system?

The Zeta1 Ursae Majoris Aa system contains 4 stars.

What type of star is the Zeta1 Ursae Majoris Aa?

The primary in the Zeta1 Ursae Majoris Aa system is a White-Blue star star.

What temperature is star Zeta1 Ursae Majoris Aa?

The primary in the Zeta1 Ursae Majoris Aa system has a temperature of 9000 K. Find out more about the temperature of stars in Stellar guide
Closest stars

 Alcor
 1.8 M☉ 2.3 ly

HD 115043
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 - 4.4 ly

HD 238224
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UPM J1344+5528
 - 5 ly
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28. 10. 2026
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WISE J1517+05 flashes powerful radio bursts every 1.149 hours, making it one of the fastest-spinning ultracool dwarfs detected in radio waves. The latest reports also explore how transit changes can reveal a hidden planet in Kepler-88 and map a possible hotspot on WD 1202-024 B. Other findings track helium in V1298 Tau b’s atmosphere and a warped dust ring around CQ Tau.
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