The closest star to the Earth, which we call the Sun, is far from the largest. Despite the fact that humanity at the moment was able to explore only a small part of the Universe, exactly as many stars and other space objects as modern equipment allows us to record and study, it is already known for certain that there are much larger luminaries, in comparison with which the Sun looks like space speck of dust. The ten largest stars are known to every person interested in astronomy.
Despite their remoteness, for the most part they are perfectly visible in the night sky, because a powerful stream of light from them is able to overcome great distances. So, what are they - the largest stars known to man Universe?
Super giant of the constellation Scorpio Antares
Starting a story about the largest stars, it is necessary to pay attention to the supergiant from the constellation Scorpio - the red star has a radius approximately equal to 1200-1500, or a little more, solar radii. More accurate data is not yet available. The distance of this object from the Earth is approximately 12 thousand sv. years. The object is visible in the sky with the naked eye.
Bright star in the constellation Cygnus
KY Cygnus is also the largest star known to modern mankind in terms of size. The distance from this object to the Earth is approximately 5 thousand light years. The star has its own oddities - its mass exceeds the solar mass only 25 times, and its equatorial radius is 1420 solar. This object emits a million times more light than the Sun, which also makes it very visible on the horizon.
In our galaxy. This is associated with huge distances in space and the complexity of observations with subsequent analysis of the data obtained. To date, scientists have managed to detect and register about 50 billion luminaries. A more advanced technique allows us to explore the distant corners of space and obtain new information about objects.
Estimation and search for supergiants in space
Modern astrophysics in the process of space exploration is constantly faced with a large number of questions. The reason for this is the gigantic size of the visible universe, about fourteen billion light years. Sometimes, when observing a star, it is quite difficult to estimate the distance to it. Therefore, before setting out on a journey in search of determining which is the largest star in our galaxy, it is necessary to understand the level of difficulty in observing space objects.
Previously, until the beginning of the twentieth century, it was believed that our galaxy is one. Visible other galaxies were classified as nebulae. But Edwin Hubble dealt a crushing blow to the ideas of the scientific world. He argued that there are a large number of galaxies, and ours is not the largest.
Space is incredibly huge
The distances to the nearest galaxies are enormous. reach hundreds of millions of years. It is quite problematic for astrophysicists to determine which is the largest star in our galaxy.
Therefore, it is even more difficult to talk about other galaxies with trillions of stars, at a distance of a hundred or more million light years. In the process of research, new objects are opened. The discovered stars are compared and the most unique and largest are determined.
Supergiant in the constellation Scutum
The name of the largest star in our galaxy is UY Scuti, a red supergiant. This is a variable which varies from 1700 to 2000 solar diameters.
Our brain is not capable of representing such quantities. Therefore, for a complete idea of what size is the largest star in the galaxy, it is necessary to compare with the values \u200b\u200bthat are understandable to us. Our solar system is suitable for comparison. The size of the star is so large that if it is placed in the place of our Sun, then the boundary of the supergiant will be in the orbit of Saturn.
And our planet and Mars will be inside the star. The distance to this "monster" of space is about 9600 light years.
The largest star in the galaxy - UY Shield - can only be conditionally considered a "king". The reasons are obvious. One of them is the huge cosmic distances and cosmic dust, which make it difficult to obtain accurate data. Another problem is directly related to physical properties supergiants. With a diameter 1700 times larger than our celestial body, the largest star in our galaxy is only 7-10 times as massive as it is. It turns out that the density of the supergiant is millions of times less than the air around us. Its density is comparable to the Earth's atmosphere at an altitude of about a hundred kilometers above sea level. Therefore, it is rather problematic to determine exactly where the boundaries of a star end and its “wind” begins.
At the moment, the largest star in our galaxy is at the end of its development cycle. It expanded (the same process will happen with our Sun at the end of evolution) and began to actively burn helium and a number of other elements heavier than hydrogen. After a few million years, the largest star in the galaxy - UY Scuti - will turn into a yellow supergiant. And in the future - into a bright blue variable, and possibly into a Wolf-Rayet star.
Along with the "king" - the supergiant UY Scuti - about ten stars with similar sizes can be noted. They include VY Big Dog, Cepheus A, NML Cygnus, WOH G64 VV and several others.
It is known that all the largest stars are short-lived and very unstable. Such stars can exist both for millions of years and for several millennia, ending their life cycle in the form of a supernova or a black hole.
The largest star in the galaxy: the search continues
Observing serious changes over the past twenty years, it is worth assuming that over time our understanding of the possible parameters of supergiants will differ from previously known ones. And it is quite possible that in the coming years another supergiant will be discovered, with a larger mass or size. And new discoveries will prompt scientists to revise previously accepted dogmas and definitions.
Life on our entire planet depends on the Sun, and sometimes we do not realize that in fact there are many other galaxies in the Universe and within them. And our almighty Sun is just a small star among billions of other luminaries. Our article will tell you the name of the largest star in the world, which can still be covered by the human mind. Perhaps, beyond its borders, in hitherto unexplored worlds, there are even more gigantic stars of immense size ...
Measure stars in suns
Before talking about the name of the largest star, we clarify that the size of stars is usually measured in solar radii, its size is 696,392 kilometers. Many of the stars in our galaxy are larger than the Sun in many ways. Most of them belong to the class of red supergiants - large massive stars with a dense hot core and a sparse shell. Their temperature is noticeably lower than the temperature of blue and - 8000-30,000 K (on the Kelvin scale) and 2000-5000 K, respectively. Red stars are called cold, although in fact their temperature is slightly less than the maximum in the core of our Earth (6000 K).
Most celestial objects do not have constant parameters (including size), but rather are in constant change. Such stars are called variable - their sizes change regularly. This can happen for various reasons. Some variable stars are in fact a system of several bodies exchanging masses, others are pulsating due to internal physical processes, shrinking and growing again.
What is the name of the largest star in the universe?
At a distance of 9.5 thousand light years from the Sun, it appeared on star maps at the end of the 17th century, thanks to the Polish astronomer Jan Hevelius. And two hundred years later, German astronomers from the Bonn Observatory added the star UY Shield (U-Ygrek) to the catalog. And already in our time, in 2012, it was found that UY Scuti is the largest of the known stars within the studied Universe.
The radius of the UY Scutum is about 1700 times greater than the radius of the Sun. This red hypergiant is a variable star, which means that its dimensions can reach even larger values. During periods of maximum expansion, the radius of the UY Shield is 1900 solar radii. The volume of this star can be compared with a sphere, the radius of which would be the distance from the center of the solar system to Jupiter.
Giants of Space: what are the names of the largest stars
In the neighboring galaxy, the Large Magellanic Cloud, is the second largest star within the studied space. Its name cannot be called particularly memorable - WOH G64, but you can take note that it is located in the constellation Dorado, a constant visible in the southern hemisphere. In size, it is slightly smaller than UY Scutum - about 1500 solar radii. But it has an interesting shape - the accumulation of a rarefied shell around the nucleus forms a spherical shape, but rather resembles a donut or bagel. Scientifically, this shape is called a torus.
According to another version, what is the name of the largest star after UY Shield, the leader is VY Canis Major. It is believed that its radius is equal to 1420 solar. But the surface of VY Canis Majoris is too rarefied - the Earth's atmosphere exceeds it in density by several thousand times. Due to the difficulty in determining what is the actual surface of the star, and what is already its companion shell, scientists still cannot come to a final conclusion regarding the size of VY Canis Major.
The heaviest stars
If we consider not the radius, but the mass of the celestial body, then the largest star is called as a set of letters and numbers in encryption - R136a1. It is also located in the Large Magellanic Cloud, but it belongs to the type of blue stars. Its mass corresponds to 315 solar masses. For comparison, the mass of the UY Shield is only 7-10 solar masses.
Another massive formation is called Eta Carina, a double giant star in the 19th century, as a result of an outburst, a nebula formed around this system, named Homunculus because of its strange shape. The mass of Eta Carina is 150-250 solar masses.
The biggest stars in the night sky
The giant stars hiding in the depths of space are inaccessible to the eye of a simple layman - most often they can only be seen through a telescope. At night, in the starry sky, the brightest and closest objects to the Earth will seem large to us - be it stars or planets.
What is the name of the largest star in the sky and at the same time the brightest? This is Sirius, which is one of the closest stars to the Earth. In fact, it is not much larger than the Sun in size and mass - only one and a half to two times. But its brightness is really much greater - 22 times greater than that of the Sun.
Another bright and therefore seemingly large object in the night sky is actually not a star, but a planet. We are talking about Venus, the brightness of which in many respects exceeds the rest of the stars. Its brilliance is visible closer to sunrise or some time after sunset.
Modern astronomy defines stars as huge plasma balls, consisting of an incandescent mass. Mankind has always been interested in the question of what is the largest star in the universe and what are its dimensions. This rating includes the TOP 10 largest such objects known to mankind. However, it has a certain amount of conventionality - there are probably even larger luminaries in space, but we don’t know about them yet, and some of them are variable stars that can contract and expand.
10. Mu Cephei
One of the largest and most powerful stars in our Galaxy with a luminosity 350,000 times greater than the sun is rightfully included in the TOP-ten stars of our rating. It is approximately 650-1420 larger than our luminary, and by its size it becomes clear which is the largest huge star. Mu Cephei is capable of accommodating up to 1 billion Suns and 2.7 quadrillion objects such as the Earth on its area. If we imagine our planet as an ordinary golf ball with a diameter of 4.3 cm, the width of this star on this scale would be equal to 5500 meters, which is twice the corresponding dimensions of the Golden Gate Bridge. Mu Cephei is 60,000 brighter than the Sun, and its bolometric luminosity is 350 times that of the Sun. At the same time, it belongs to the category of dying, since scientists have recorded irreversible processes of carbon synthesis on it.
9. V766 Centauri
In the ranking of the largest stars, yellow supergiants are also represented. The radius of V766 Centauri is 1490 times larger than the Sun. The object has one distinguishing feature- in fact, it is a double star along with HR 5171. Its "companion" is much smaller and is so close that it practically touches a more massive star. They are located in the constellation of the same name at a distance of about 12 thousand light years from the Sun.
8. AN Scorpio
Being a red supergiant with a radius of approximately 1411 solar, the object confirms the assumption of what the largest star looks like and what size it is. It is separated from the Earth by 7.4 thousand light years. The star is surrounded by a dust shell, among the sources of its microwave radiation are water and silicon oxide. During the observation period, they were approaching AN Scorpii at a speed of 13 km/s, which confirmed the ongoing process of the giant's compression.
7. KY Cygnus
A hypergiant, thanks to a radius of 1420 solar, rightfully ranked in the TOP 10 largest stars in the Universe. This is an asterisk of the boundary type, and if it had a lower luminosity, it would no longer belong to supergiants. It is located 5 thousand light years from Earth. KY Cygnus is a very bright object that surpasses our luminary in this indicator by at least 138 thousand times.
6. VX Sagittarius
Another red supergiant that made the list of the largest. It belongs to the group of semi-regular variable stars, according to scientists, it gradually loses mass due to the influence of the stellar wind. Large stars in the Universe, as a rule, are located at a great distance from the Earth and VX Sagittarius was no exception - about 5250 light years share it with our planet. The radius of the giant star ranges from 850-1940 solar, and its diameter probably exceeds that of the asteroid belt of the solar system.
5. Westerland 1-26
Red hypergiant, located in the constellation of the Altar. Discovered by the Swedish astronomer B. Westerlund in the Westerlund 1 star cluster system. Anyone who wonders what the largest star is called needs to know that the luminosity of Westerland 1-26 exceeds the solar one by 380 thousand times, and its surface temperature exceeds 3000 K. In the ESO photo Westerlund 1 appears to be one of the most massive open clusters in the galaxy.
4. RW Cephei
A red hypergiant named after the constellation Cepheus. It is located at a distance of 11.5 thousand light years from our planet. It is not by chance that it is included in the TOP 10 largest stars, since its radius is 1535 times greater than the solar one. The luminosity of this large object is 625 thousand times greater than that of the Sun. At the end of its existence, it can become a hypernova, and its core transforms into a black hole.
3. WON G64
The red supergiant of the constellation Dorado, the second largest star in the Universe. Its estimated radius can reach at least 1540 solar. According to astrophysicists, this large object, included in the TOP of the largest stars, has lost up to 1/3 of its mass due to the stellar wind. Using the Very Large Telescope complex in Chile, it was possible to obtain an image that helps to understand that dust and gas around WON G64 forms a torus, reducing its luminosity to 280 thousand solar.
2. VY Canis Major
The hypergiant well-known to astronomers, which is named after the constellation of the same name, reaches 1600 solar radii in size. At the same time, the mass of the object included in the list of the largest stars has only 17-fold superiority over the Sun, which confirms its extremely low density. The volume of the giant is 7 10 15 times larger than the Earth's. Astrophysicists studying the star with the Hubble Space Telescope say it will explode as a hypernova in 100,000 years. The VY photo of Canis Major shows the star expelling large volumes of gas during the outburst.
36 2Seemingly inconspicuous UY Shield
Modern astrophysics in terms of stars seems to be re-experiencing its infancy. Observations of the stars give more questions than answers. Therefore, when asking which star is the largest in the Universe, you need to be immediately ready for answers. Are you asking about the largest star known to science, or about what limits science limits a star to? As is usually the case, in both cases you will not get a definitive answer. The most likely candidate for the largest star quite equally shares the palm with his "neighbors". As for how much it can be less than the real "king of the star" also remains open.
Comparison of the sizes of the Sun and the star UY Scuti. The sun is an almost invisible pixel to the left of UY Shield.
The supergiant UY Scutum, with some reservation, can be called the largest star observed today. Why "with reservation" will be said below. UY Scuti is 9500 light-years away and is seen as a dim variable star visible through a small telescope. According to astronomers, its radius exceeds 1700 radii of the Sun, and during the pulsation period this size can increase to as much as 2000.
It turns out that if such a star were placed in the place of the Sun, the current orbits of a terrestrial planet would be in the bowels of a supergiant, and the boundaries of its photosphere would sometimes rest against the orbit. If we imagine our Earth as a grain of buckwheat, and the Sun as a watermelon, then the diameter of the UY Shield will be comparable to the height of the Ostankino television tower.
To fly around such a star at the speed of light will take as much as 7-8 hours. Recall that the light emitted by the Sun reaches our planet in just 8 minutes. If you fly at the same speed with which it makes one revolution around the Earth in an hour and a half, then the flight around the UY Shield will last about 36 years. Now imagine these scales, given that the ISS flies 20 times faster than a bullet and tens of times faster than passenger airliners.
Mass and Luminosity of UY Shield
It is worth noting that such a monstrous size of the UY Shield is completely incomparable with its other parameters. This star is "only" 7-10 times more massive than the sun. It turns out that the average density of this supergiant is almost a million times lower than the density of the air surrounding us! For comparison, the density of the Sun is one and a half times the density of water, and a grain of matter even “weighs” millions of tons. Roughly speaking, the averaged matter of such a star is similar in density to the layer of the atmosphere located at an altitude of about one hundred kilometers above sea level. This layer, also called the Karman line, is a conditional boundary between the earth's atmosphere and space. It turns out that the density of the UY Shield is only a little short of the vacuum of space!
Also UY Shield is not the brightest. With its own luminosity of 340,000 solar, it is ten times dimmer than the brightest stars. A good example is the star R136, which, being the most massive star known today (265 solar masses), is almost nine million times brighter than the Sun. At the same time, the star is only 36 times larger than the Sun. It turns out that R136 is 25 times brighter and about the same times more massive than UY Shield, despite the fact that it is 50 times smaller than the giant.
Physical parameters of the UY Shield
In general, UY Scuti is a pulsating variable red supergiant of spectral type M4Ia. That is, on the Hertzsprung-Russell spectrum-luminosity diagram, UY Scutum is located in the upper right corner.
At the moment, the star is approaching the final stages of its evolution. Like all supergiants, she began to actively burn helium and some other heavier elements. According to modern models, in a matter of millions of years UY Scutum will successively transform into a yellow supergiant, then into a bright blue variable or a Wolf-Rayet star. The final stages of its evolution will be a supernova explosion, during which the star will shed its shell, most likely leaving behind a neutron star.
Already now UY Scutum shows its activity in the form of semi-regular variability with an approximate pulsation period of 740 days. Given that a star can change its radius from 1700 to 2000 solar radii, the rate of its expansion and contraction is comparable to the speed of spaceships! Its mass loss is an impressive rate of 58 millionth solar masses per year (or 19 Earth masses per year). This is almost one and a half earth masses per month. So, being on the main sequence millions of years ago, UY Scutum could have had a mass of 25 to 40 solar masses.
Giants among the stars
Returning to the reservation mentioned above, we note that the primacy of UY Shield as the largest known star cannot be called unequivocal. The fact is that astronomers still cannot determine the distance to most stars with a sufficient degree of accuracy, and therefore estimate their size. In addition, large stars tend to be very unstable (recall the UY Scutum pulsation). Similarly, they have a rather blurry structure. They may have a rather extended atmosphere, opaque gas and dust shells, disks, or a large companion star (an example is VV Cephei, see below). It is impossible to say exactly where the boundary of such stars passes. In the end, the well-established concept of the boundary of stars as the radius of their photosphere is already extremely arbitrary.
Therefore, this number can include about a dozen stars, which include NML Cygnus, VV Cepheus A, VY Canis Major, WOH G64 and some others. All these stars are located in the vicinity of our galaxy (including its satellites) and are in many ways similar to each other. All of them are red supergiants or hypergiants (see below for the difference between super and hyper). Each of them in a matter of millions, or even thousands of years, will turn into a supernova. They are also similar in size, ranging from 1400-2000 solar.
Each of these stars has its own peculiarity. So in UY Shield, this feature is the previously discussed variability. WOH G64 has a toroidal gas and dust envelope. Extremely interesting is the double eclipsing variable star VV Cephei. It is a close system of two stars, consisting of the red hypergiant VV Cephei A and the blue main sequence star VV Cephei B. The centers of these stars are located from each other in some 17-34 . Considering that the VV radius of Cepheus B can reach 9 AU. (1900 solar radii), the stars are located at "arm's length" from each other. Their tandem is so close that whole pieces of the hypergiant flow with great speeds to the “little neighbor”, which is almost 200 times smaller than it.
Looking for a leader
Under such conditions, estimating the size of stars is already problematic. How can one talk about the size of a star if its atmosphere flows into another star, or smoothly passes into a gas and dust disk? This is despite the fact that the star itself consists of a very rarefied gas.
Moreover, all the largest stars are extremely unstable and short-lived. Such stars can live for a few millions, or even hundreds of thousands of years. Therefore, observing a giant star in another galaxy, you can be sure that a neutron star is now pulsating in its place or a black hole is warping space, surrounded by the remnants of a supernova explosion. If such a star is even thousands of light years away from us, one cannot be completely sure that it still exists or has remained the same giant.
Add to this the imperfection of modern methods for determining the distance to stars and a number of unspecified problems. It turns out that even among the ten largest known stars, it is impossible to single out a certain leader and arrange them in ascending order of size. In this case, Shield's UY was cited as the most likely candidate to lead the Big Ten. This does not mean at all that its leadership is undeniable and that, for example, NML Cygnus or VY Canis Major cannot be larger than her. Therefore, different sources can answer the question about the largest known star in different ways. This speaks rather not about their incompetence, but about the fact that science cannot give unambiguous answers even to such direct questions.
The largest in the universe
If science does not undertake to single out the largest among the discovered stars, how can we say which star is the largest in the Universe? According to scientists, the number of stars even within the boundaries of the observable universe is ten times greater than the number of grains of sand on all the beaches of the world. Of course, even the most powerful modern telescopes can see an unimaginably smaller part of them. The fact that the largest stars can be distinguished by their luminosity will not help in the search for a “stellar leader”. Whatever their brightness is, it will fade when observing distant galaxies. Moreover, as noted earlier, the brightest stars are not the largest (an example is R136).
Also remember that when observing a large star in a distant galaxy, we will actually see its "ghost". Therefore, it is not easy to find the largest star in the Universe, its searches will be simply meaningless.
Hypergiants
If a largest star impossible to find in practice, maybe it is worth developing it theoretically? That is, to find a certain limit, after which the existence of a star can no longer be a star. Even here, however, modern science faces a problem. The current theoretical model of the evolution and physics of stars does not explain much of what actually exists and is observed in telescopes. An example of this is the hypergiants.
Astronomers have repeatedly had to raise the bar for the limit of stellar mass. This limit was first introduced in 1924 by the English astrophysicist Arthur Eddington. Having obtained the cubic dependence of the luminosity of stars on their mass. Eddington realized that a star cannot accumulate mass indefinitely. The brightness increases faster than the mass, and sooner or later this will lead to a violation of hydrostatic equilibrium. The light pressure of the increasing brightness will literally blow away the outer layers of the star. The limit calculated by Eddington was 65 solar masses. Subsequently, astrophysicists refined his calculations by adding unaccounted components to them and using powerful computers. So the modern theoretical limit for the mass of stars is 150 solar masses. Now remember that the mass of R136a1 is 265 solar masses, which is almost twice the theoretical limit!
R136a1 is the most massive star known today. In addition to it, several more stars have significant masses, the number of which in our galaxy can be counted on the fingers. Such stars are called hypergiants. Note that R136a1 is much smaller than the stars that, it would seem, should be below it in class - for example, the supergiant UY Shield. This is because hypergiants are called not the largest, but the most massive stars. For such stars, a separate class was created on the spectrum-luminosity diagram (O), located above the class of supergiants (Ia). The exact initial bar for the mass of a hypergiant has not been established, but, as a rule, their mass exceeds 100 solar masses. None of the biggest stars of the "Big Ten" falls short of these limits.
Theoretical impasse
Modern science cannot explain the nature of the existence of stars whose mass exceeds 150 solar masses. This raises the question of how a theoretical limit to the size of stars can be determined if the radius of a star, unlike mass, is itself a vague concept.
Let's take into account the fact that it is not known exactly what the stars of the first generation were, and what they will be in the course of the further evolution of the Universe. Changes in the composition, metallicity of stars can lead to radical changes in their structure. Astrophysicists have only to comprehend the surprises that will be presented to them by further observations and theoretical research. It is quite possible that UY Shield may turn out to be a real crumb against the background of a hypothetical "king-star" that shines somewhere or will shine in the farthest corners of our Universe.
