You’ve probably heard of a few different types of stars in the night sky, but maybe not all. We’ll start with the ones you’re likely to know and move on to those you may or may not have heard of. We indicate where you are likely to find them, some using your home telescope or binoculars to stargaze.
1. Yellow Dwarf
Our Sun is a yellow dwarf that illuminates our day. (No need for a telescope or sky map here). This is a G V type star, which are all about the size of our Sun or smaller (about 80–100% of the Sun in size). These have a lifespan of about 10 billion years. It’s expected to last another 7 billion years. Temperature ranges between 5,300 and 6,000 Kelvin (K; 9080ºF — 10,340ºF) and their light derives from the fusion of hydrogen into helium.
Other yellow dwarfs include Alpha Centauri, Tau Ceti, and 51 Pegasi.
2. Red Dwarf
These are low mass stars, that are the longest lived and the most common type of star in the Milky Way. But, they are not easily seen. Proxima Centauri is an example of a red dwarf. Temperature wise these are cool by comparison since they reach only 3800 K (6,380ºF).
3. Red Giant Star
Another dying star. Examples: Aldebaran (Alpha Tauri) in the constellation Taurus and Mira (Omicron Ceti) in Cetus, in the northern sky. These ones have run out of hydrogen.
4. White Dwarfs
A white dwarf is a star that has exhausted its nuclear fuel.
Example: In the constellation, Canis Major, the companion star to Sirius, Sirius B is a white dwarf made of mostly carbon and oxygen (generated from helium fusion). The main star, Sirius A, a main sequence star, is the brightest star in the night sky. It can be seen by the naked eye and is a good one for kids to practice using their telescope.
5. Supergiant Star
These are the biggest and most luminous. Their temperature can range from about 3,450 K to over 20,000 K. Although rare and short-lived they are super bright. Examples include Rigel in the constellation Orion and Deneb in Cygnus, both are the brightest stars in each. You can see these with your naked eye.
6. Neutron Stars
You’re not able to see these with the typical instruments. These are very dense small celestial objects with a radius of about 12-18 miles (20-30 km), of mostly packed neutrons. They are thought to be a collapsed center, remnant of a giant star. It’s a stage at the end of the stars existence.
Example: SR J0108-1431 in the constellation Cetus (the Whale), in the northern sky is the closest neutron star to us. This example is a pulsar, which is neutron star that is highly magnetized and rotates, emitting a beam of electromagnetic radiation.
7. T tauri Star
This is a class of variable stars that are relatively young (< 10 million years). The temperature at the core of these is two low for hydrogen fusion. How are they powered? Gravitational energy driven by contraction of the star is their source of power.
The nearest T Tauri stars to us are in the Taurus molecular cloud in the constellations Taurus and Auriga, and the ρ-Ophiuchus (pronounced rho oh-fee-ook-ee) molecular cloud of the constellation Ophiuchus, both about 400 light years away. More than 200 T Tauri stars are estimated in the Rho-Ophiuchus molecular cloud.
8. Main Sequence Star
These stars fuse hydrogen to form helium in their cores. Our sun is a main sequence star, as is Sirius A, and as is 90% of stars known in the Universe.
9. Variable Stars
These stars are so named because they change in brightness (as seen from Earth). The cause can be intrinsic (e.g. the star itself shrinking and expanding) or extrinsic (e.g. another celestial object eclipses it). There are around 42,000 variable stars.
Examples are R And in the constellation Andromeda and T Aqr in the constellation Aquarius.
10. Runaway Stars
A runaway star is one moving at a speed and direction through space abnormal to the surrounding interstellar matter, which includes the gas, dust, and cosmic radiation. An example of a runaway star is GD 50, which is a white dwarf star, smaller than our Earth by with slightly more mass than our sun.
11. Hypervelocity Stars
These are stars that move at high velocities. In 2005, one was recorded that moved at a velocity of 2 million mph. It was coined an ‘Outcast’ star, ejected by the Milky Way. They are associated with black holes.
12. Intergalactic Stars
These are sometimes termed rogue stars because they are not gravitationally bound to any galaxy.
13. Halo Stars
This is a group of globular clusters and field stars. These encircle the outer edge of spiral galaxies including the Milky Way in an area called the ‘halo zone’. They are thought to be the oldest stars in the galaxy.
As the name suggests (proto- meaning first or earliest), it is an early stage — a forming star. It’s basically a gas mass that’s contracting.
There is some much to learn about the Universe. When you wish upon a star, what type will it be?