What types of stars there are?

Artist's depiction of the Morgan-Keenan spectral diagram, showing how stars differ in colors as well as size. Credit: Wikipedia Commons

 

There are many types of stars in the universe, and they can be classified based on various characteristics such as mass, temperature, size, and luminosity. Here are a few examples:

* Red dwarfs: These are the smallest and coolest stars, with masses ranging from about 0.08 to 0.50 solar masses and temperatures typically below 4,000 K. They are also the most common type of star in the Milky Way, making up about 70% of all stars. Red dwarfs are much less luminous than larger stars, and they are also much fainter and harder to observe. They are often referred to as "M dwarfs" because they fall in the M spectral class, which includes stars with temperatures below 4,000 K. Red dwarfs are also the longest-lived stars, with lifetimes of billions of years. This is because they burn their nuclear fuel much more slowly than larger stars, and they also have much smaller surface areas, which means they lose heat more slowly. Red dwarfs are generally not visible to the naked eye, but they can be observed with telescopes or other instruments. They are often found in binary or multiple star systems, and they are also known to have planets orbiting around them. Some red dwarfs are known to flare or erupt with bursts of radiation, and they can also produce strong magnetic fields that can affect their surroundings.

* Yellow dwarfs: These are stars similar in size and temperature to the Sun, with masses ranging from about 0.8 to 1.2 solar masses and temperatures between 5,500 and 6,000 K. Yellow dwarfs are classified as G-type main-sequence stars, which means that they are in the process of converting hydrogen into helium through nuclear fusion in their cores. This process releases a tremendous amount of energy, which is what makes yellow dwarfs shine so brightly. Yellow dwarfs are relatively common in the universe and are thought to make up about 7% of all stars. They have a surface temperature of around 5,500 to 6,000 degrees Celsius and a luminosity of about 1 to 3 solar luminosities. Yellow dwarfs are generally considered to be stable and long-lived, with a lifespan of several billion years. Yellow dwarfs are also known to have planets orbiting around them. Our own Solar System, for example, is home to eight planets that orbit around the Sun, which is a yellow dwarf. The presence of planets around yellow dwarfs is thought to be common, and many exoplanets (planets outside of our own Solar System) have been discovered orbiting around yellow dwarfs. It's worth noting that the term "yellow dwarf" is a bit of a misnomer, as yellow dwarfs are actually white or blue-white in color. They appear yellow to us because of the way that our eyes perceive light, and because the temperature of their surface is similar to the color of a candle flame.

* Blue dwarfs: These are hot, massive stars with temperatures above 10,000 K and masses ranging from about 3 to 50 solar masses. They are very bright and short-lived, with lifetimes of only a few million years. Blue dwarfs are relatively uncommon in the universe and are thought to make up only about 0.1% of all stars. They have a luminosity of about 0.01 to 0.1 solar luminosities. Because they are smaller and less massive than our Sun, blue dwarfs have a shorter lifespan, with an estimated lifespan of only a few hundred million years.

* Red giants: These are stars that have exhausted the hydrogen fuel in their cores and have swollen in size as they cool and expand. They are much larger and cooler than main-sequence stars, with temperatures typically below 4,000 K. They are much larger than our Sun, with a radius that can be hundreds of times larger. Because they are so large, red giants have a relatively low surface gravity, which means that their outer layers are relatively diffuse and puffed up. Red giants are thought to be relatively common in the universe, and are thought to make up about 10% of all stars. They are known to have planets orbiting around them, although it is not clear how common this is.

* White dwarfs: These are the remnants of stars that have burned through all their nuclear fuel and collapsed. They are very dense, with masses similar to that of the Sun but sizes similar to that of Earth. White dwarfs have a surface temperature of around 5,000 to 30,000 degrees Celsius and a luminosity of about 0.01 to 100 solar luminosities. They are much smaller than our Sun, with a radius that is only a few thousand kilometers across. Despite their small size, white dwarfs are extremely dense, with a mass that is similar to that of our Sun but packed into a much smaller volume. White dwarfs are thought to be relatively common in the universe, and are thought to make up about 85% of all stars. They are known to have planets orbiting around them, although it is not clear how common this is

* Neutron stars: These are extremely dense, compact objects that are formed when a massive star collapses at the end of its life. They are only a few kilometers in size but have masses similar to that of the Sun. They are composed almost entirely of neutrons, which are subatomic particles with no electrical charge. Neutron stars are the remnants of stars that were once much more massive than our Sun, but have collapsed in on themselves at the end of their lives. Neutron stars are incredibly dense, with a surface gravity that is billions of times stronger than that of Earth. They have a surface temperature of around 100,000 degrees Celsius and a luminosity of about 1,000 to 100,000 solar luminosities. Despite their small size, neutron stars are incredibly massive, with a mass that is similar to that of our Sun but packed into a much smaller volume. Neutron stars are thought to be relatively rare in the universe, and are thought to make up only about 1% of all stars. They are known to have planets orbiting around them, although it is not clear how common this is. Neutron stars are also known to emit intense radiation and have extremely powerful magnetic fields, which makes them fascinating objects to study for astronomers.

* Black holes: Black holes are objects in space that are so massive and dense that not even light can escape their gravitational pull. They are created when a star collapses in on itself at the end of its life, and are thought to be some of the most mysterious and intriguing objects in the universe. There are three main types of black holes: stellar black holes, intermediate black holes, and supermassive black holes. Stellar black holes are the smallest type, with a mass that is several times larger than that of our Sun. They are formed when a star that is at least 20 times more massive than the Sun collapses in on itself at the end of its life. Intermediate black holes are slightly larger, with a mass that is hundreds or thousands of times larger than that of the Sun. They are thought to form through the merger of multiple smaller black holes. Supermassive black holes are the largest type, with a mass that is millions or billions of times larger than that of the Sun. They are thought to be at the center of most galaxies, including our own Milky Way. Black holes are incredibly difficult to study, because nothing, not even light, can escape their gravitational pull. However, scientists are able to infer their presence and study them by observing the way that they interact with their surroundings. For example, black holes can pull in gas and dust from their surroundings, creating a disk of material that can be observed using telescopes. Black holes are also thought to be some of the most powerful objects in the universe, and are capable of emitting intense radiation and powerful jets of matter.

Here are a few more types of stars:

* Supergiants: These are the largest and most luminous stars, with diameters up to a few thousand times that of the Sun and luminosities up to a million times that of the Sun. They are also short-lived, with lifetimes of only a few million years. Supergiant stars are a type of star that are much larger and more luminous than our Sun. They are classified as O-type, B-type, or A-type supergiants, depending on their temperature and spectral type. Supergiant stars are in the later stages of their lives and have exhausted most of their hydrogen fuel. As a result, they have begun to fuse heavier elements in their cores, which releases a tremendous amount of energy and makes them shine brightly. Supergiant stars have a surface temperature of around 10,000 to 50,000 degrees Celsius and a luminosity of about 10,000 to 1 million solar luminosities. They are much larger than our Sun, with a radius that can be hundreds or thousands of times larger. Because they are so large, supergiant stars have a relatively low surface gravity, which means that their outer layers are relatively diffuse and puffed up. Supergiant stars are thought to be relatively rare in the universe, and are thought to make up only about 0.1% of all stars.

* Hypergiants: These are even larger and more luminous than supergiants, with diameters up to several hundred thousand times that of the Sun and luminosities up to a billion times that of the Sun. They are extremely rare and short-lived, with lifetimes of only a few hundred thousand years. Hypergiant stars are a type of star that are extremely large and luminous. They are among the most massive and luminous stars in the universe, and are characterized by their enormous size and extremely high luminosity. Hypergiant stars are in the later stages of their lives and have exhausted most of their hydrogen fuel. As a result, they have begun to fuse heavier elements in their cores, which releases a tremendous amount of energy and makes them shine brightly. Hypergiant stars have a surface temperature of around 10,000 to 50,000 degrees Celsius and a luminosity of about 10 million to 1 billion solar luminosities. They are much larger than our Sun, with a radius that can be thousands or even tens of thousands of times larger. Because they are so large, hypergiant stars have a relatively low surface gravity, which means that their outer layers are relatively diffuse and puffed up.

* Wolf-Rayet stars: Wolf-Rayet stars are a type of star that are extremely hot and luminous. They are characterized by their strong emission lines in their spectra, which are caused by the presence of highly ionized helium and nitrogen in their atmospheres. Wolf-Rayet stars are thought to be in the later stages of their lives and are experiencing rapid mass loss through powerful stellar winds. Wolf-Rayet stars are extremely hot, with a surface temperature of around 25,000 to 50,000 degrees Celsius, and extremely luminous, with a luminosity of about 10,000 to 1 million solar luminosities. They are much larger than our Sun, with a radius that can be hundreds or thousands of times larger. Because they are so large, Wolf-Rayet stars have a relatively low surface gravity, which means that their outer layers are relatively diffuse and puffed up. Wolf-Rayet stars are thought to be relatively rare in the universe, and are thought to make up only about 0.1% of all stars.

* Pulsars: These are neutron stars that emit intense beams of electromagnetic radiation from their poles. They rotate rapidly and can be observed as pulsing radio waves or X-rays. Pulsars are a type of neutron star, which are extremely dense, compact objects that are formed when a massive star collapses in on itself at the end of its life. Pulsars are known for their highly regular pulsations, which are caused by the rapid rotation of the neutron star's magnetic field. These pulsations can be observed as radio waves, X-rays, or gamma rays, and are often used to study pulsars and learn more about their properties. Pulsars are extremely dense, with a mass that is similar to that of our Sun but packed into a volume that is only about 20 kilometers across. They have a surface gravity that is billions of times stronger than that of Earth. Pulsars are extremely hot, with a surface temperature of around 100,000 degrees Celsius. Despite their small size, they are incredibly massive, with a mass that is similar to that of our Sun but packed into a much smaller volume. Pulsars are thought to be relatively rare in the universe, and are thought to make up only about 1% of all stars. They are known to have planets orbiting around them, although it is not clear how common this is. Pulsars are also known to emit intense radiation and have extremely powerful magnetic fields, which makes them fascinating objects to study for astronomers. They are thought to be some of the most powerful objects in the universe.

* Quasars: Quasars (short for "quasi-stellar objects") are extremely luminous, active galactic nuclei that are located at the centers of distant galaxies. They are thought to be powered by supermassive black holes, which are located at the centers of most galaxies and have masses that are millions or billions of times larger than that of the Sun. Quasars are among the most luminous objects in the universe, and are often visible even at great distances. They are known for their strong emission lines in their spectra, which are caused by the presence of highly ionized gases in their surroundings. Quasars are also known for their powerful jets of matter, which can extend for hundreds of thousands of light-years and are thought to be powered by the rotating accretion disk of material around the supermassive black hole. Quasars are thought to be relatively rare in the universe, and are thought to make up only a small fraction of all galaxies. They are thought to be among the most distant objects that can be observed with telescopes, with some quasars located billions of light-years away from Earth. It's worth noting that the term "quasar" is a bit of a misnomer, as quasars are not actually stars. They are thought to be powered by supermassive black holes, which are located at the centers of galaxies and are surrounded by a rotating accretion disk of material. Quasars are so luminous because of the tremendous amount of energy that is released as material falls into the black hole and is compressed and heated up.

* Brown dwarfs: Brown dwarfs are a type of star that are too small and cool to sustain hydrogen fusion in their cores. As a result, they are not able to generate the energy needed to shine brightly like a normal star. Instead, they are dim and relatively cool, with a surface temperature of around 1,000 to 2,000 degrees Celsius. Brown dwarfs are classified as M-type or L-type dwarfs, depending on their temperature and spectral type. They are much smaller and less massive than our Sun, with a mass that is typically between 13 and 80 times the mass of Jupiter. Because they are so small and cool, brown dwarfs are difficult to detect, and were not discovered until the late 20th century. Brown dwarfs are thought to be relatively common in the universe, and are thought to make up about 15% of all objects in the Milky Way.