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Alpha Ophiuchi
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Star Alpha Ophiuchi

Binary star Alpha Ophiuchi is located 49 light years away from the Sun. It consists of a subgiant and a orange star. For now, there are no known exoplanets in this star system.
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Sun distance
49 light years
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Alpha Ophiuchi A

Subgiant
Spectral class: A5IVnn

Location +

Ascension iconRight ascension: 17h 34m 56.078s
Declination iconDeclination: 12° 33' 36.135'' (equatorial region)
Parallax iconParallax: 67.130
Distance iconSun distance: 48.586 ly | 14.9 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: 240 % M Sun
| 2514 M Jupiter
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Star mass
Mass of the star Alpha Ophiuchi A is 2.40 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: 260 % R Sun
| 25.9 R Jupiter
+
Star size
Radius of the star Alpha Ophiuchi A is 2.6 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: 7900 K | 1.37 T Sun
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Star temperature
Surface temperature of Alpha Ophiuchi A is 7900 K, which is 137 % 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: 0.7 billions years | 0.15 Sun
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Star age
Star Alpha Ophiuchi A is 0.7 billion years old, which is about 0.15 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: 25.4 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): 2.1
Magnitude iconAbsolute magnitude (V): 1.2
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

Alpha Ophiuchi B

Orange star
Spectral class: K5-7V

Basic characteristic

icon weight
Mass: 85 % M Sun
| 890 M Jupiter
+
Star mass
Mass of the star Alpha Ophiuchi B is 2.40 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: 90 % R Sun
| 8.6 R Jupiter
(estimate)
+
Star size
Radius of the star Alpha Ophiuchi B is not known. Its estimated value based on other similar stars is about 90 % 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: 4400 K
 (estimate)
+
Star temperature
Surface temperature of Alpha Ophiuchi B is estimated to be 4434 K, which is 76 % 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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Alpha Ophiuchi system structure

 Alpha Ophiuchi A
Alpha Ophiuchi B

More about Alpha Ophiuchi

       Alpha Ophiuchi 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
alf Oph, Ras Alhague, Rasalhague, 55 Ophiuchi, BD+12° 3252, FK5 656, HD 159561, HIP 86032, HR 6556, SAO 102932
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Frequently Asked Questions

How far is the Alpha Ophiuchi system from the Sun?

The Alpha Ophiuchi system is 49 light years or 14.9 parsecs from the Sun.

What galaxy is the Alpha Ophiuchi star in?

The Alpha Ophiuchi is in the Milky Way galaxy just like the Sun.

How many stars are in the Alpha Ophiuchi system?

The Alpha Ophiuchi system contains 2 stars.

What type of star is the Alpha Ophiuchi?

The primary in the Alpha Ophiuchi system is a Subgiant star.

What temperature is star Alpha Ophiuchi?

The primary in the Alpha Ophiuchi system has a temperature of 7900 K. Find out more about the temperature of stars in Stellar guide
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