In the constellation Sculptor is the smallest star in the Universe known today. Its radius is only slightly larger than that of Saturn, and its mass is only 85 times greater than that of Jupiter.
“Our discovery is a clear demonstration of the minimum size stars can reach. If the mass of EBLM J0555-57Ab had been a little less, then the thermonuclear reactions in its core simply would not have started, and it would have turned into a brown dwarf,” says Alexander Boettischer (Alexander Boetticher) from the University of Cambridge (UK).
Bottisher and his colleagues discovered the first example of a star located at the very border between brown dwarfs and the faintest and smallest red dwarfs by observing close pairs of stars, one of which is noticeably smaller in size than its companion.
When such a small and dim star passes across the disk of a larger star, its brightness drops sharply, which allows astronomers to very accurately measure the diameter and mass of both “halves” of the binary system. Guided by a similar principle, experts have been observing the night sky of the southern hemisphere for several years, trying to find the smallest and faintest stars.
These searches were crowned with complete success: Bottischer's team managed to discover the record small star EBLM J0555-57Ab, located 600 light years from Earth. It revolves around an almost complete twin of the Sun, making one revolution around it every seven days, RIA Novosti reports.
This Saturn-sized star, with just 8% the mass of the Sun, is incredibly dense for a star and attracts matter about 300 times stronger than Earth. As observations show, it is distinguished by an unusually calm character for small-sized stars, which, coupled with the very long lifespans of such luminaries, creates.
“The smallest stars are optimal for searching for Earth twins and studying their atmospheres. On the other hand, before we can begin such searches, we must first comprehensively study and understand the star around which they orbit or may orbit,” concludes the Emory Trio (
In about 3-4 billion years, as astronomers say, the depths of our native star will begin to run out of hydrogen. The thermonuclear reaction of helium fusion supported by it will no longer be able to restrain gravitational compression. With a sharp decrease in the size of the star's core, the pressure and temperature there will reach such values at which the second step in the evolution of the star - the synthesis of carbon from helium - will become possible. Then the Sun, having increased its diameter from the current 1.4 million km to 355 million km, will simply “swallow” our Earth, which will burn and evaporate in the sizzling atmosphere of the newly born red giant.
But even with this, the Sun will be far from the real ones. So Antares (α Scorpio) has a diameter of 1.2 billion km, Betelgeuse (α Orion) - almost 1.7 billion km. The largest star today is considered to be UY of the Scutum constellation with a diameter of about three billion km. So? It turns out that all the stars that surround us are larger than our Sun? Not certainly in that way.
Our star belongs to the class of yellow dwarfs. Yellow dwarfs are stars whose mass makes it possible to maintain conditions in the core for the thermonuclear reaction of helium fusion from all types of hydrogen, including (which is important) ordinary, light hydrogen. The mass of this class of celestial bodies varies from 0.81 to 1.22 solar masses, and the surface is heated to 5-6 thousand Kelvin (the same scale as Celsius, only zero Kelvin is −273 ° C, or absolute zero) .
Objects that “received” less than 8% of the solar mass at the birth of matter are not destined to become stars in the usual sense of the word. This is a kind of transitional link between the giant planets and stars. Their mass allows only the combustion of heavy hydrogen isotopes - deuterium and tritium - to be maintained in the depths. The surface temperature of such “understars” sometimes does not exceed a thousand Kelvin. According to most researchers, such a star will externally resemble our Jupiter - the same equatorially oriented stripes of clouds, only illuminated from the inside with a reddish-brown light.
But between the class of stars to which our Sun belongs and brown dwarfs there is a most interesting type of luminary - red dwarfs. Although the pressure and temperature of their cores support the conditions for full thermonuclear fusion, it proceeds extremely slowly. It is to this group that the smallest star in the Universe known today belongs, bearing the complex name: OGLE-TR-122b.
Opening
It was possible to get acquainted with OGLE-TR-122b thanks to hunters for mysterious and elusive dark matter. How can we find an object located hundreds and thousands of light years away from us that does not emit anything? As part of the Polish-American project OGLE (the name of the project served as the name of the objects discovered during its course), a solution was proposed based on the gravitational effect that such an object would have on the light coming to the Earth from stars or galaxies located further away. Modern science has technical means capable of recording such a slight deviation.
OGLE-TR-122b is the smallest star discovered
A side result, so to speak, of the program was the discovery of many objects, such as brown or red dwarfs, invisible from Earth due to their small mass and extremely low luminosity. Similarly, in 2005, the smallest star in the Universe was discovered - the red dwarf OGLE-TR-122b. This is the second star of a binary system. OGLE-TR-122a is its neighbor, more massive, similar to our Sun, but the “younger brother” is a typical representative of red dwarfs. The diameter of the baby is only about 160 thousand kilometers. The phrase “only” is appropriate, since the diameter of our Jupiter is not much smaller - 140 thousand km. The mass of OGLE-TR-122b is about one hundred Jupiter masses or 9% solar. But the smallest star in the Universe is 50 times denser than our star.
Mysterious babies
Red dwarfs are truly unique stars. Their special distinguishing characteristic is their simply unrealistically long life span. 4.5 billion years ago, when our solar system was still a whirlwind of dust and gas, and the Proto-Sun flared hesitantly at its center, many red dwarfs had already formed and had planets. Our star will turn over time (in about 5 billion years) into a red giant, “welding” Mercury, Venus and Earth in its crown. And then, after 7...8 billion years, it will become a dying stellar “cinder” - a white dwarf, and the same red dwarfs will practically not grow old during this time and will shine for another billions of years (and according to some assumptions - up to a trillion years) and shine...
Such a long lifespan of a star creates favorable conditions for the emergence and development of life on its planets. Just imagine - billions and billions of years of stable, unchanged meteorological conditions on the planet. Most astrobiologists are confident that it is the satellite planets of red dwarfs that are the main candidates for the presence of extraterrestrial life.
Another interesting fact about the life of red dwarfs is their number. If we could see all celestial bodies of this type with the naked eye, just as we see brighter stars, then the sky would become five times brighter for us. Despite the fact that red dwarfs are so difficult for discoverers, they, according to some assumptions, account for up to 80% (!!!) of the entire stellar mass of the universe.
How to see
Unfortunately, it’s not easy to see the system (a-b) OGLE-TR-122. The luminosity of this pair is about 16 (remember, the naked eye is capable of distinguishing stars up to 6 stars inclusive). But this is not the biggest obstacle to observations: OGLE-TR-122 is a star in the southern hemisphere and the best place to observe it would be, for example, Australia.
Its coordinates for trained astronomy lovers who are ready to go there and owners of good optics with the ability to point in azimuth:
- right ascension: 11h 06m 51.99s
- list marked: -60° 51′ 45.7″
Happy observing!
>The smallest star in the Universe
2MASS J0523-1403 – smallest known star: description and characteristics with photos, comparison with other stars and the Sun, list of nearby small stars.
Among the huge star array you can find both huge monsters and very tiny ones. Who are they? And what the smallest star in the Universe accessible to our lens?
Which star is the smallest star in the Universe
This will make you smile, but astronomers are huge fans of size. They are always interested in finding the largest planet, nebula, comet, galaxy, etc. Let's not forget about balance and talk about little stars. Which star is the smallest?
Large specimens are born in places with huge accumulations of hydrogen. Small ones appear where there is little of it. This prevents the required temperature and pressure from being achieved to activate nuclear fusion.
A star is a celestial body whose mass and pressure allow it to fuse hydrogen into helium. In this process, energy is released that attracts everything to itself. This prevents the star from collapsing. Since it was the best studied, scientists decided to use its size for comparison.
Fusion reactions occur if an object reaches 7.5% solar mass. These are red dwarfs, the closest of which is Proxima Centauri (12.3% solar mass and 200,000 km wide). That is, the smallest possible dwarf will be only half the size.
But here lies an important difference. This star will be only 8 times the mass of Jupiter. Yes, more hydrogen does not make the star larger. It simply becomes denser due to increased gravity.
Proxima Centauri is too dim to be seen without the use of technology. The tiny one that can be seen with the naked eye is 61 Cygnus. This is a binary pair whose star reaches 66% solar size. Located 11.4 light years away. Next comes Epsilon Eridani (74%) and Alpha Centauri B (87%). It turns out that the Sun is the fourth smallest star that can be seen without the use of technology.
Latest news about the smallest star in the Universe
Not long ago, scientists stumbled upon a small star 2MASS J0523-1403 in the constellation Hare, 40 light years away. It is especially important because it may not only be the smallest modern star, but also rank first in terms of tinyness throughout the entire existence of the Universe. Her research makes us wonder again: where does a star begin, and where does a brown dwarf begin?
Stars are hot balls of gas fueled by the fusion of hydrogen and helium in the core. They vary in size and type. The smallest are red dwarfs, reaching only 10% of the solar mass. Agree that this is a small part, because large representatives can exceed their mass by 100 times. But this raises a logical question: How tiny can an object be to still be considered a star?
Previously, it was assumed that objects that do not reach the specified minimum threshold cannot activate fusion in the core, and therefore act as brown dwarfs. This is an intermediate link between gas giants and low-mass stars (red dwarfs). Most often, they reach the size of , but lack the massiveness to become a star (they lack an internal source of energy).
There is another important difference: they have opposite mass to size ratios. The more hydrogen you add to a star, the wider its radius. But if you do the same thing with a brown dwarf, it will become smaller due to electron degeneracy.
How to calculate the boundary? To do this, the researchers studied areas of the sky and located objects that could be located near the boundary between brown dwarfs and stars. Next, they started calculating luminosity, temperature indicators and radii. It turned out that as the temperature decreases, the radius also decreases. But after the 2100 K mark, a gap occurs until the radius begins to increase with decreasing heating. This is typical for brown dwarfs. Scientists can now calculate the ideal parameters at which the main sequence ends.
2MASS J0523-1403 is located on this boundary, but from the side of the star. Its temperature reaches 2074 K. This is the tiniest and smallest object. If the mass were even smaller, it would go into the category of brown dwarfs. In theory, there is an even lower probability of finding the object, but this has not happened yet.
Researchers believe this will help with the search for life on other planets. Brown dwarfs cool much faster, so their planets will not be able to host life. Being aware of temperatures at the border will help you find candidates faster. Now you know which star is the smallest in the Universe.
There are trillions of stars in the Universe. We don't even see most of them, and those that are visible to our eyes can be bright or very dim, depending on their size and other properties. What do we know about them? Which star is the smallest? Which one 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 force of their own gravity helps them maintain balance. Like all cosmic bodies, they move in space, but due to the great distance it is difficult to notice.
Thermonuclear reactions occur inside stars, causing them to emit energy and light. Their brightness varies considerably and is measured in magnitudes. In astronomy, each quantity corresponds to a certain number, and the lower it is, the lower the brightness of the star. The smallest star in size is called a dwarf; there are also normal stars, giants and supergiants.
In addition to brightness, they also have a temperature, due to which stars emit a different spectrum. The hottest are blue, followed (in descending order) by blue, white, yellow, orange and red. Stars that do not fit into any of these parameters are called peculiar.
The hottest stars
When we talk about the temperature of stars, we mean the surface characteristics of their atmospheres. The internal temperature can only be determined through calculations. How hot a star is can be judged by its color or spectral class, which is usually designated by the letters O, B, A, F, G, K, M. Each of them is divided into ten subclasses, which are designated by numbers from 0 to 9.
Class O is among the hottest. Their temperature ranges from 50 to 100 thousand degrees Celsius. However, scientists recently dubbed the Butterfly Nebula, the temperature of which reaches 200 thousand degrees, the hottest star.
Other hot stars are blue supergiants, for example, Rigel Orionis, Alpha Giraffe, Gamma. Cool stars are M-class dwarfs. WISE J085510.83-071442 is considered the coldest in the Universe. The temperature of the star reaches -48 degrees.
Dwarf stars
A dwarf is the direct opposite of a supergiant, the smallest star in size. They are small in size and luminosity, and may even be smaller than the Earth. Dwarfs make up 90% of the stars in our galaxy. They are significantly smaller than the Sun, however, they are superior to the naked eye; they are almost impossible to see in the night sky.
Red dwarfs are considered the smallest. They have a modest mass and are cool compared to other stars. Their spectral class is designated by the letters M and K. Temperatures can reach from 1,500 to 1,800 degrees Celsius.
Star 61 in the constellation Cygnus is the smallest star that can be seen without professional optics. It emits a dim light and is located 11.5 light years away. Slightly larger in size is an orange dwarf located at a distance of ten light years.
The closest to us is Proxima; a person could reach it only after 18 thousand years. It is a red dwarf that is 1.5 times larger than Jupiter. It is located only 4.2 light years from the Sun. The luminary is surrounded by other small stars, but they have not been studied due to their low brightness.
Which star is the smallest?
Not all stars are familiar to us. 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 is a double star, meaning it is connected by a gravitational field to another star. Their mutual rotation around each other's masses lasts seven and a half days. The system was discovered in 2005 during the Optical Gravitational Lens Experiment, from the English abbreviation of which it was named.
The smallest star is a red dwarf in the southern hemisphere sky. Its radius is 0.12 that 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 can be slightly larger than the average planet if its mass is at least ten times less than the Sun. Most likely, there are smaller stars in the Universe, but modern technology does not allow them to be seen.
It is assumed that the smallest star in the Universe is EBLM J0555−57Ab, reports RIA FAN. According to British scientists, the radius of this celestial body is slightly larger than that of Saturn, but at the same time its mass is 85 times that of Jupiter. In order to become a star, the mass of a cosmic object must be at least 7% solar, reports Astronomy & Astrophysics.
ON THIS TOPIC
It is noteworthy that the dimensions of EBLM J0555−57Ab are actually on the boundary between active red dwarfs and extinct brown dwarfs. Astronomers noted that cosmic bodies of even smaller radius can no longer activate internal thermonuclear reactions between hydrogen atoms, which prevents them from turning into a star.
Note that EBLM J0555−57Ab is located only 600 light years from Earth. Together with two other stars - EBLM J0555-57A and EBLM J0555-57B - they form a triple system that orbits an almost complete twin of the Sun. One revolution of a star around a luminary lasts only seven Earth days.
Earlier, Portuguese and British astronomers calculated the number of brown dwarfs in the Milky Way. Experts said the galaxy contains at least 25 billion to one hundred billion brown dwarfs. At the same time, according to scientists, there may be much more of them due to the many dim stars.
