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Tau Boötis
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Star Tau Boötis

Binary star Tau Boötis is located 51 light years away from the Sun. It consists of a subgiant and a red dwarf. There is at least one exoplanet in this system.
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Sun distance
51 light years
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Tau Boötis A

Subgiant, Rotating Variable
Spectral class: F7IV-V

Location +

Ascension iconRight ascension: 13h 47m 15.216s
Declination iconDeclination: 17° 27' 25.825'' (equatorial region)
Parallax iconParallax: 64.047
Distance iconSun distance: 50.924 ly | 15.6 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: 139 % M Sun
| 1456 M Jupiter
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Star mass
Mass of the star Tau Boötis A is 1.39 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: 142 % R Sun
| 14.1 R Jupiter
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Star size
Radius of the star Tau Boötis A is 1.42 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: 6399 K | 1.11 T Sun
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Star temperature
Surface temperature of Tau Boötis A is 6399 K, which is 111 % 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: 2 billions years | 0.43 Sun
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Star age
Star Tau Boötis A is 2 billion years old, which is about 0.43 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: 3.06 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): 4.5
Magnitude iconAbsolute magnitude (V): 3.5
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

Tau Boötis B

Red dwarf, , Rotating Variable
Spectral class: M3V

Basic characteristic

icon weight
Mass: 49 % M Sun
| 513 M Jupiter
+
Star mass
Mass of the star Tau Boötis B is 1.39 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: 48 % R Sun
| 4.8 R Jupiter
+
Star size
Radius of the star Tau Boötis B is 0.48 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: 3400 K
 (estimate)
+
Star temperature
Surface temperature of Tau Boötis B is estimated to be 3433 K, which is 59 % 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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Tau Boötis system structure

 Tau Boötis A
Tau Boötis A b 0.05 AU 1907.4 M⊕ 3.3 days
Tau Boötis B

More about Tau Boötis

       Tau Boötis 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
* tau Boo B, τ Boo, 4 Boötis, NSV 6444, BD+18°2782, FK5 507, GC 18637, GJ 527, HD 120136, HIP 67275, HR 5185, SAO 100706, ADS 9025, CCDM 13473+1727, LTT 14021, Gaia EDR3 1244571953471006720
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Frequently Asked Questions

How far is the Tau Boötis system from the Sun?

The Tau Boötis system is 51 light years or 15.6 parsecs from the Sun.

What galaxy is the Tau Boötis star in?

The Tau Boötis is in the Milky Way galaxy just like the Sun.

How many stars are in the Tau Boötis system?

The Tau Boötis system contains 2 stars.

What type of star is the Tau Boötis?

The primary in the Tau Boötis system is a Subgiant star.

What temperature is star Tau Boötis?

The primary in the Tau Boötis system has a temperature of 6399 K. Find out more about the temperature of stars in Stellar guide
Closest stars

 G 149-94
 - 4.3 ly

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HD 122742
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LP 497-33
 - 8.5 ly

BD+18 2776
 - 8.8 ly
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