There are trillions of stars in the universe. Most of them we can't even see, and those that are visible to our eyes can be bright or very dim, depending on size and other properties. What do we know about them? What is the smallest star? Which is the hottest?
Stars and their varieties
Our Universe is full of interesting objects: planets, stars, nebulae, asteroids, comets. Stars are massive balls of gases. The balance helps them to keep the force of their own gravity. Like all cosmic bodies, they move in space, but due to the large distance it is difficult to notice.
Fusion reactions occur inside stars, making them radiate energy and light. Their brightness varies considerably and is measured in star magnitudes. In astronomy, each value corresponds to a certain number, and the smaller it is, the lower the brightness of the star. The smallest star in size is called a dwarf, and there are also normal stars, giants, and supergiants.
In addition to brightness, they also havetemperature, due to which stars emit a different spectrum. The hottest colors are blue, followed (in descending order) by blues, whites, yellows, oranges, and reds. Stars that do not fit into any of these parameters are called peculiar.
Hottest Stars
When we talk about the temperature of stars, we mean the surface characteristics of their atmospheres. The internal temperature can only be known through calculations. How hot a star is can be judged by its color or spectral type, which is usually denoted by the letters O, B, A, F, G, K, M. Each of them is divided into ten subclasses, which are indicated by numbers from 0 to 9.
Class O is one of the hottest. Their temperature ranges from 50 to 100 thousand degrees Celsius. However, scientists have recently dubbed the Butterfly Nebula as the hottest star, with temperatures reaching 200,000 degrees.
Other hot stars are blue supergiants, such as Orion's Rigel, Alpha Giraffa, Gamma of the constellation Parus. Cold stars are class M dwarfs. WISE J085510.83-071442 is considered the coldest in the Universe. The temperature of the star reaches -48 degrees.
Dwarf stars
Dwarf - the exact opposite of supergiants, the smallest star in size. They are small in size and luminosity, maybe even smaller than the Earth. Dwarfs make up 90% of the stars in our galaxy. They are much smaller than the Sun, however, they are larger than Jupiter. naked eyethey are almost impossible to see in the night sky.
Red dwarfs are considered the smallest. They have a modest mass and are cold compared to other stars. Their spectral type is denoted by the letters M and K. The temperature can reach from 1500 to 1800 degrees Celsius.
Star 61 in the constellation Cygnus is the smallest star that can be seen without professional optics. It emits dim light and is 11.5 light-years away. Slightly larger is the orange dwarf Epsilon Eridani. Located at a distance of ten light years.
Closest to us is Proxima in the constellation Centaurus, a person could reach it only after 18 thousand years. It is a red dwarf that is 1.5 times the size of Jupiter. It is located only 4.2 light years from the Sun. The luminary is also surrounded by other small stars, but they have not been studied due to their low brightness.
Which star is the smallest?
We are not familiar with all the stars. There are hundreds of billions of them in the Milky Way galaxy alone. Of course, scientists have studied only a small part of them. The smallest star known to date in the universe is called OGLE-TR-122b.
It belongs to a binary star system, that is, it is connected by a gravitational field with another star. Their mutual rotation around each other's masses is seven and a half days. The system was discovered in 2005 during the Opticalgravitational lensing experiment, from the English abbreviation of which it was named.
The smallest star is a red dwarf in the constellation Carina in the southern hemisphere of the sky. Its radius is 0.12 of the Sun, and its mass is 0.09. It is 100 times more massive than Jupiter, and 50 times more dense than the Sun.
The discovery of this star system confirmed scientists' theory that a star could be slightly larger than an average planet if its mass were at least ten times less than the sun's. Most likely, smaller stars exist in the Universe, but modern technology does not allow us to see them.
