About Stars
Stars are the building blocks of galaxies. They are massive spheres of plasma held together by gravity, powered by nuclear fusion in their cores. Understanding them means understanding the universe itself.
The Life Cycle of a Star
All stars follow a similar journey from birth to death, but their path depends on how massive they are. Hover over each stage to learn more.
Protostar
A baby star forming from a collapsing cloud of gas and dust. Gravity pulls material inward, heating the core.
Main Sequence
A stable adult star fusing hydrogen into helium in its core. The Sun is here - 90% of a star's life is spent in this phase.
Red Giant
When hydrogen runs low, the star swells up enormously. Its surface cools and reddens as the core shrinks.
Supernova
A massive star's core collapses in seconds, triggering a titanic explosion that can outshine entire galaxies.
Neutron Star
The impossibly dense corpse of a massive star. A teaspoon weighs billions of tons. Some spin hundreds of times per second.
Black Hole
Gravity so intense that not even light can escape. Formed when the most massive stars collapse beyond a neutron star.
Types of Stars by Classification
Astronomers classify stars by their spectral type - a system that sorts stars by temperature and color. The mnemonic "Oh Be A Fine Guy/Girl, Kiss Me" helps remember the order.
| Class | Temperature | Color | Example |
|---|---|---|---|
| O | 30,000K - 50,000K | Blue | Zeta Ophiuchi |
| B | 10,000K - 30,000K | Blue-white | Rigel |
| A | 7,500K - 10,000K | White | Sirius |
| F | 6,000K - 7,500K | Yellow-white | Procyon |
| G | 5,200K - 6,000K | Yellow | Sun |
| K | 3,700K - 5,200K | Orange | Arcturus |
| M | 2,400K - 3,700K | Red | Betelgeuse |
Notable Stars
From the brightest to the most extreme, these are some of the most fascinating stars in our galaxy.
Sirius
The brightest star in Earth's night sky. Its name means 'glowing' in Greek. It has a faint white dwarf companion called Sirius B.
Betelgeuse
A massive red supergiant nearing the end of its life. If placed at the center of our solar system, its surface would reach past Jupiter.
Rigel
A blue supergiant 21 times more massive than the Sun. It shines with the brilliance of 120,000 Suns.
Proxima Centauri
The closest star to Earth (after the Sun). It hosts at least two planets, one of which is Earth-sized.
Polaris
The North Star. It sits nearly directly above Earth's north pole, making it a fixed point in the sky as other stars appear to rotate.
VY Canis Majoris
One of the largest known stars. If it replaced the Sun, its surface would extend beyond the orbit of Saturn.
Did you know?
The Sun is classified as a G-type main-sequence star (G2V). It contains 99.86% of all mass in our solar system and converts 600 million tons of hydrogen into helium every second.