Yellow dwarf . Star belonging to the main sequence of spectral type G and weighing between 0.7 and 1 times the mass of the sun .
Summary
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- 1 Properties
- 2 Stages
- 3 Some existing dwarfs
- 4 Sources
Properties
A yellow dwarf is a yellow main sequence star with a mass between 1 and 1.4 solar masses. Of luminosity class V, it is in the process of converting hydrogen into helium through nuclear fusion in its nucleus . Our Sun is the best known example of a yellow dwarf.
It is estimated that the life of a yellow dwarf is about 10 billion years, the time it takes to consume its reserves of hydrogen, the main fuel during this stage. When this element is finished, the star expands several times its previous size and becomes a red giant. Eventually, the red giant expels its outer layers to become a planetary nebula . Its center, on the contrary, collapses and becomes a dense white dwarf.
About 10% of the stars in the Milky Way are yellow dwarfs. They have a surface temperature of about 6000 ° C and the brightness of a bright yellow, almost white. At the end of its life, a yellow dwarf star turns into a red giant and a white dwarf .
The Sun is a typical yellow dwarf. The red giant phase indicates the end of a yellow dwarf’s life.
Stages
Stars reach this stage when the heart has stopped its main fuel, hydrogen . The helium’s fusion reactions then travel, and as the center of the star contracts, its outer layers swell, redden and cool.
Transformed into carbon and oxygen , the helium has been depleted, in turn and dies from the star.
The star then sheds its outer layers and the center contracts into a planet- sized white dwarf .
Some existing dwarfs
Among the yellow dwarfs found, Alpha Centauri A , Tau Ceti and 51 Pegasi .
See the following table:
| Star | Spectral type | Apparent magnitude | Absolute magnitude | Right ascension (J2000). | Declination (J2000). | Distance ( light years ). |
| Sun | G2V | – 26.73 | – 4.8 | __ | __ | 1.6×10-5 |
| α Centauri A | G2V | -0.01 | 4.34 | 14h 39m.50s | 60º 50 ‘02.3 | 4.39 |
| t Ceti | G8Vp | 3.49 | 5.68 | 01h 44m 04.08s | -15º 58 ‘14.9 | 11.9 |
| Achird A | G3V | 3.46 | 4.59 | 00h 49m 06.29s | + 57º 48 ‘54.7 | 19.4 |
| 82 Eridani | G5V | 4.26 | 5.35 | 03h 19m 55.65s | -43º 04 ‘11.2 | 19.8 |
| δ Pavonis | G8V | 3.55 | 4.62 | 20h 08m 42.61s | -66º 10 ‘55.4 | 19.9 |
| ζ Boötis A | G8Ve | 4.72 | 5.59 | 14h 52m 23.38s | + 19º 06 ‘01.7 | 21.9 |
| Alula Australis A | GOV | 4.41 | 4.25 | 11h 18m 11s | + 31º 31 ’45 | 27.2 |
| Alula Australis B | G5V | 4.87 | 5.07 | 11h 18m 11s | + 31º 31 ’45 | 27.2 |
| Asterion | GOV | 4.24 | 4.63 | 12h 33m 44.54s | + 41º 21 ‘26.9 | 27.3 |
| 61 Virginis | G5V | 4.74 | 5.09 | 13h 18m 24.31s | 18º 18 ‘40.3 | 27.8 |
| X1 Orionis A | GOV | 4.39 | 4.70 | 05h 54m 22.98s | + 20º 16 ‘34.2 | 28.3 |
| 41 Arae A | G8V | 5.55 | 5.83 | 17h 19m 03.83s | -46º 38 ‘10.4 | 28.7 |
| Beta Comae Berenices | GOV | 4.23 | 4.42 | 13h 11m 52.39s | + 27º 52 ‘41.5 | 29.9 |
| K1 Ceti | G5V | 4.84 | 5.03 | 03h 19m 21,70s | + 03º 22 ‘12.7 | 29.9 |
| HR 4523 A | G3V | 4.89 | 5.06 | 11h 46m 31.07s | -40º 30 ‘01.3 | 30.1 |
| 61 Ursae Majoris | G8V | 5.31 | 5.41 | 11h 41m 03.02s | + 34º 12 ‘05.9 | 31.1 |