The life of a star is determined by it's initial MASS
The smaller they are the longer they live. The bigger they are.. you get the picture.
The universe is not old enough (13.8 billion years) for any of the smallest stars (red dwarfs) to have reached the end of their lives.
| Spectral Type | Effective temperature (T)* | conventional color description | Mass (in solar masses M☉) | Bolometric Luminosity (L) * | Fraction of all main sequence stars | |
| O | ≥ 30,000 K | blue | ≥ 16 M☉ | ≥ 30,000 L☉ | 0.00003% | |
| B | 10,000–30,000 K | deep blue white | 2.1–16 M☉ |
|
0.13% | |
| A | 7,500–10,000 K | white | 1.4–2.1 M☉ | 5–25 L☉ | 0.6% | |
| F | 6,000–7,500 K | yellow white | 1.04–1.4 M☉ | 1.5–5 L☉ | 3% | |
| G | 5,200–6,000 K | yellow | 0.8–1.04 M☉ | 0.6–1.5 L☉ | 7.6% | |
| K | 3,700–5,200 K | orange | 0.45–0.8 M☉ | 0.08–0.6 L☉ | 12.1% | |
| M | 2,400–3,700 K | red | 0.08–0.45 M☉ | ≤ 0.08 L☉ | 76.45% |
*Effective temperature =Temperature of a blackbody** that would emit the same total amount of radition.
The Stefan–Boltzmann law describes the total energy radiated per unit surface area of a black body across all wavelength per unit time is determined by it's temperature.
F=αT4
The total (bolometric, over all wavlengths) luminosity of a star is then
L = 4πR2αT4 where 4πR2 is the surface area of the star.
**Black body = An idealised collection of matter that absorbs all incident radiation. A black body in thermal equilibrium (constant temperature) is emitted according to Plank's law, meaning that is has a spectrum that is determined by the temperature alone.
STELLAR SPECTRUM (ORANGE) LOOKS LIKE BLACK BODY SPECTRUM (GREY)
AS BLACK BODY GETS HOTTER, SPECTRUM PEAK SHIFTS TO HIGHER WAVELENGTHS
Stars first stage of their life is as a PROTOSTAR
Starts with the gravitational collapse of a giant molecular cloud, typically 100 light-years across and contain up to 6,000,000 times the mass of the sun.
HYDROGEN FUSION BEGINS AT 10 MILLION DEGRESS
This is when a ball of gas becomes a star.
Red Dwarfs are the most common type of star in the Milky Way, but none can be viewed from Earth with the naked eye. Proxima Centauri, the nearest star to the Sun, is a red dwarf.
OTHER GASSY CELESTIAL OBJECTS
Brown Dwarfs
Occupy the space between the lightest stars and heaviest gas giants (like Jupiter and Saturn).
They aren't actually brown, more like magenta or orange/red.
The nearest known brown dwarf, Luhman 16a, is 6.5 light years away, the third closest system to our Solar System. It was discovered in March 2013.
8% the mass of the sun (or 8000 Jupiter masses) down to about 13 Jupiter masses and don't get hot enough to fuse hydrogen, poor things. However, they are thought to fuse deuterium (hydrogen with an extra neutron) and litium (with atomic number 3, after helium (2) and hydrogen (1)).
| Spectral types | |
| M | |
| L | |
| T | |
| Y |