An illustration of R136a1, the most massive star known to date. Credit & Copyright: Sephirohq / Wikipedia.
Look at the night sky - it is filled with stars. However, only a microscopic part of them is visible to the naked eye. In fact, scientists estimate that there are 10,000 billion galaxies in the visible universe, each with more than a hundred billion stars. And this is neither more nor less than 10 24 stars. These spectacular thermal stations come in a variety of colors and sizes – and many of them make our Sun look tiny. However, which star is a true cosmic giant? First, we need to define the concept of a giant star: should it have the largest radius or the largest mass?
To date, the star with the largest radius is recognized as the star UY Scuti (Scuti), a variable red supergiant in the constellation Scutum. It is more than 9,500 light-years distant from us, and consists mostly of hydrogen and helium, as well as a number of other heavier elements. In terms of chemical composition, UY Scutum resembles our Sun, but has a radius 1708 (± 192) times greater than that of our star. That is almost 1,200,000,000 km, making its circumference more than 7.5 billion kilometers. To make it easier to understand such dimensions, one can imagine an aircraft that would take 950 years to fly around UY Scutum - and even if the aircraft could travel at the speed of light, its journey would last 6 hours and 55 minutes.
If we place UY Scutum in place of our Sun, then its surface will pass somewhere between the orbits of Jupiter and Saturn - it goes without saying that the Earth in this case will be swallowed up. Given the huge size and mass of 20 to 40 solar masses, one can calculate that the density of the UY Shield is only 7×10 -6 kg/m 3 . In other words, it is more than a billion times less than the density of water. Indeed, if we could put this star in a pool, then theoretically it would float. Being over a million times less dense than Earth's atmosphere, UY Shield would float like a balloon in the air.
But if these crazy facts didn't surprise you, then let's move on to the heaviest star. The heavyweight star R136a1 is located in the Large Magellanic Cloud, approximately 165,000 light-years away. This star is only 35 times the size of our Sun, yet it is 265 times as massive as our Sun - which is really amazing given the fact that it has already lost 55 solar masses in its 1.6 million years of life.
R136a1 is a highly unstable Wolf-Rayet star. It appears as a blue ball with an indistinct surface, which constantly generates extremely powerful stellar winds. These winds move at speeds up to 2600 km/s. Due to such high activity, R136a1 loses 3.21×10 18 kg/s of its mass, which is about one Earth every 22 days. Stars of this type shine brightly and die quickly. R136a1 radiates nine million times more energy than our Sun. Its brightness is 94,000 times the brightness of the Sun. In fact, it is the brightest star ever found. The temperature on its surface is more than 53,000 Kelvin, and it has only two million years to live, after which it will explode as a supernova.
Of course, against such giants, our Sun seems like a dwarf, but over time it will also increase in size. In about seven and a half billion years, it will reach its largest size and become a red giant.
The science
Of course, the oceans are vast, and the mountains are incredibly high. What's more, the 7 billion people that the Earth is home to is also an incredibly large number. But, living in this world, with a diameter of 12,742 kilometers, it is easy to forget that this is, in essence, a trifle for such a thing as space. When we look into the night sky, we realize that we are just a grain of sand in a vast infinite universe. We invite you to learn about the largest objects in space, the size of some of them is difficult for us to imagine.
1) Jupiter
The largest planet in the solar system (142,984 kilometers in diameter)
Jupiter is the largest planet in our star system. Ancient astronomers named this planet after Jupiter, the father of the Roman gods. Jupiter is the fifth planet from the Sun. The planet's atmosphere is 84 percent hydrogen and 15 percent helium. Everything else is acetylene, ammonia, ethane, methane, phosphine and water vapor.
The mass of Jupiter is 318 times the mass of the Earth, and the diameter is 11 times greater. The mass of this giant is 70 percent of the mass of all the planets in the solar system. Jupiter's volume is large enough to contain 1,300 Earth-like planets. Jupiter has 63 known moons, but most of them are incredibly small and fuzzy.
2) Sun
The largest object in the solar system (1,391,980 kilometers in diameter)
Our Sun is a yellow dwarf star, the largest object in the star system in which we exist. The Sun contains 99.8 percent of the mass of this entire system, most of the rest of the mass is Jupiter. The Sun is currently 70 percent hydrogen and 28 percent helium, with the remaining matter accounting for just 2 percent of its mass.
Over time, the hydrogen in the Sun's core turns into helium. Conditions in the Sun's core, which is 25 percent of its diameter, are extreme. The temperature is 15.6 million Kelvin and the pressure is 250 billion atmospheres. The energy of the Sun is achieved through nuclear fusion reactions. Every second, approximately 700,000,000 tons of hydrogen are converted into 695,000,000 tons of helium and 5,000,000 tons of energy in the form of gamma rays.
3) Our solar system
15*10 12 kilometers in diameter
Our solar system includes just one star, which is the central object, and nine major planets: Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, Neptune and Pluto, as well as many satellites, millions of solid asteroids and billions of icy comets.
4) Star VY Canis Major
The largest star in the universe (3 billion kilometers in diameter)
VY Canis Majoris is the largest known star and one of the brightest stars in the sky. It is a red hypergiant located in the constellation Canis Major. The radius of this star is about 1800-2200 times greater than the radius of our Sun, its diameter is about 3 billion kilometers.
If this star were placed in our solar system, it would close the orbit of Saturn. Some astronomers believe that VY is actually smaller—about 600 times the size of the Sun—and therefore would only reach the orbit of Mars.
5) Huge deposits of water
Astronomers have discovered the largest and most massive reservoir of water ever found in the universe. The giant cloud, about 12 billion years old, contains 140 trillion times more water than all of Earth's oceans combined.
A cloud of gaseous water surrounds a supermassive black hole located 12 billion light-years from Earth. This discovery shows that water has dominated the universe for almost its entire existence, the researchers said.
6) Extremely large and massive black holes
21 billion solar masses
Supermassive black holes are the largest black holes in the galaxy, weighing hundreds or even thousands of millions of solar masses. Most, if not all, galaxies, including the Milky Way, are believed to contain supermassive black holes at their centers.
One such monster, 21 million times the mass of the Sun, is an egg-shaped funnel of stars in NGC 4889, the brightest galaxy in the stretched cloud of thousands of galaxies. The hole is located about 336 million light-years away in the constellation Coma Berenices. This black hole is so huge that it is 12 times larger than our solar system in diameter.
7) Milky Way
100-120 thousand light years in diameter
The Milky Way is a broken spiral galaxy that contains 200-400 billion stars. There are many planets revolving around each of these stars.
According to some estimates, 10 billion planets are in the habitable zone, revolving around their parent stars, that is, in zones where there are all conditions for the origin of life like Earth.
8) El Gordo
The largest cluster of galaxies (2 * 10 15 solar masses)
El Gordo is located more than 7 billion light-years from Earth, so what we are seeing today is just an early stage of it. According to the researchers who have studied this galaxy cluster, it is the largest, hottest and emits the most radiation than any other known cluster at the same distance or further.
The central galaxy at the center of El Gordo is incredibly bright and has an unusual blue glow. The authors of the studies suggest that this extreme galaxy is the result of a collision and merger of two galaxies.
Using the Spitzer Space Telescope and optical imaging, scientists estimate that 1 percent of the cluster's total mass is stars, and the rest is hot gas that fills the space between the stars. This ratio of stars to gas is similar to the ratio in other massive clusters.
9) Our Universe
Size - 156 billion light years
Of course, no one could ever name the exact dimensions of the Universe, but, according to some estimates, its diameter is 1.5 * 10 24 kilometers. In general, it is difficult for us to imagine that there is an end somewhere, because the Universe includes incredibly gigantic objects:
Earth Diameter: 1.27*104km
Sun diameter: 1.39*106 km
Solar system: 2.99 * 10 10 km or 0.0032 sv. l.
Distance from the Sun to the nearest star: 4.5 sv. l.
Milky Way: 1.51*10 18 km or 160,000 sv. l.
Local group of galaxies: 3.1 * 10 19 km or 6.5 million sv. l.
Local supercluster: 1.2 * 10 21 km or 130 million sv. l.
10) Multiverse
One can try to imagine not one, but many Universes that exist at the same time. The Multiverse (or Multiple Universe) is a feasible collection of many possible Universes, including our own, which collectively encapsulate everything that exists or can exist: the integrity of space, time, material matter and energy, and the physical laws and constants that govern it all. describe.
However, the existence of other Universes besides ours has not been proven, so it is very likely that our Universe is the only one of its kind.
Stars are huge balls of burning plasma. But, with the exception of the Sun, they look like tiny dots of light in the night sky. At the same time, our Sun is not the smallest or largest star. There are many much more massive and larger stars than the Sun. Some of them have evolved since their inception. Others grow as they "age".
To answer the question about what is the largest star in the universe, we "sorted" the stars according to such a feature as size. The equatorial radius of the Sun, which is 696,392 kilometers, was taken as the unit for measuring the stellar radius.
This celestial body, also known under a different name (HR 5171 A), belongs to the yellow hypergiants and is a double star. Its smaller "partner" HR 5171 B revolves around V766 Centauri in 1300 Earth days.
This star is located in the direction of the constellation Cepheus, about 5 thousand light years from Earth. A red hypergiant with a radius approximately equal to 1050-1900 solar radii is part of a binary star system. Its companion is the small blue star VV Cephei B, which revolves around its "big brother" in an elliptical orbit. The name of the star is given in honor of the largest of the pair, and now it is known as one of the largest double stars in the Milky Way.
To get to know this red supergiant from the constellation Scorpius, people would have to travel a distance of 7400 light years. The AH radius of Scorpio is 1411 times that of the sun.
7. VY Canis Major
A heated debate among astronomers is associated with this star. According to estimates updated in 2012, its radius exceeds the radius of the Sun by 1420 times. However, according to the initial estimate of Robert Humphreys, the radius of VY Canis Majoris is 1800 - 2200 times greater than the solar one. The exact radius of the stellar giant has not yet been established. When you can find out about him for sure, the leader in the ranking of the biggest stars may change.
The radius of this hypergiant star is at least 1420 times the radius of the Sun, and the brightness level is as much as 300,000 times higher than the sun. It is located in the constellation Cygnus, at a distance of about 5 thousand light years from Earth.
This star belongs to the class of hypergiants - the most powerful and bright, the heaviest, and at the same time the rarest and shortest-lived supergiants. Its radius exceeds the solar one by about 1520 times.
VX Sagittarius is located in the constellation Cepheus, 9000 light years from our planet. It is so huge that it could easily cover the orbital path of Saturn if it were in place of the Sun. The star's red color indicates that its temperature range is between 3,000 and 4,000 Kelvin. Hotter stars are yellow in color, while very hot ones take on a bluish tint.
At a distance of 11,500 light-years from our planet, in the star cluster Westerland 1, is the fourth largest star in the galaxy. In terms of luminosity, it is 380 thousand times greater than the Sun, and being placed in the place of our yellow star with its photosphere, it would absorb the orbit of Jupiter. The photosphere is where a star becomes transparent to light, and where photons—that is, light particles—can disappear. The photosphere allows astronomers to approximate the "edges" of a star.
Here is another star known to science from the constellation Cepheus was included in the list of the largest. The radius of this red supergiant is about 1600 solar radii. If RW Cephei were in place of the Sun, the radiating layer of its stellar atmosphere (photosphere) would extend beyond the orbit of Jupiter.
The second largest star in space is located in the constellation Dorado, 160 thousand light years from our world. Despite the fact that this star has lost up to a third of its original mass due to the stellar wind, a long-term thick annular layer of gas and dust torus has formed around it. The "dimensions" of the star have been adjusted to account for all the mass present in its ring. It is expected to go supernova in a couple of thousand years.
1. UY Scuti - the largest star in the universe
At a distance of 9500 light years from the Sun, in the constellation of the Shield, is the largest star in the world. Its approximate size is almost eight astronomical units, where one astronomical unit is the distance between the Earth and the Sun. This is enough to propagate the UY Scutum photosphere into the orbit of Jupiter.
UY Shield is so gigantic and so bright that you can see it with powerful binoculars on a dark night. It is visible along the stars of the Milky Way, and looks like a reddish star with a faint spot.
Exploring a supergiant
In the summer of 2012, astronomers, using the Very Large Telescope complex located in the Atacama Desert in Chile, measured the parameters of three red supergiants near the Galactic Center region. The objects of study were UY Shield, AH Scorpio and KW Sagittarius.
Scientists have determined that all three stars are 1,000 times larger and more than 100,000 times brighter than the Sun. They also discovered that UY Scutum is the largest, brightest of the three stars. From the radius and luminosity, the effective temperature was obtained - 3665 ± 134 K.
Mass and dimensions of the UY Shield compared to the Sun
The exact mass of this star is unknown, primarily because it has no visible companion star, thanks to which its mass can be measured using the study of gravitational interference. According to stellar evolutionary models, the initial mass of a star (at its formation) corresponding to a red supergiant stage, such as that of UY Scuti, would be around 25M☉ (perhaps up to 40M☉ for a non-rotating star) and constantly burning up. Presumably, its current mass is 7-10 M☉ and continues to decrease. UY Scuti is not only the largest, but also the fastest burning star known to science today.
The mass of UY Scutum is just over 30 times the mass of our Sun, which doesn't even come close to the top of the list of most massive stars. This honor belongs to the star R136a1, which is 265 times the mass of the Sun, but only 30 times the radius of the Sun in radius.
The mass and physical dimensions do not always correlate for celestial bodies, especially for giant stars. Thus, although UY Scutum is only 30 times more massive than the Sun, it has a radius somewhere in the region of 1700 times the radius of our daylight. The error of this measurement is about 192 solar radii.
Is life possible near UY Scuti
A habitable zone or an orbital zone with the highest probability of life is a complex thing, the possibility of which depends on several factors. The planet on which life originated should not be too far or too close to the star. According to astronomers' calculations, the habitable zone around UY Scutum will be between 700 and 1300 astronomical units (AU). It's an insanely long distance. The number in kilometers is simply incomprehensible - it is about 149,597,870,700 km. For comparison: the habitable zone in the solar system is located at a distance of 0.95 to 1.37 AU from the Sun.
If a living planet is at a safe distance, say 923 astronomical units from UY Scutum, a year on it would be 9612 Earth years. That's almost 2500 years of winter! And 2500 years of summer. That is, many generations will change who know only one season.
UY Scutum may indeed have a planetary system in this zone, but if it does, it won't exist for very long. You, the reader, may reasonably ask, “Why?” Because the future of the star is too bright.
What awaits the star in the future
Based on current models of stellar evolution, scientists speculate that UY Scutum began fusing helium into a shell around the core. As helium runs out, the star will begin to fuse heavier elements such as lithium, carbon, oxygen, neon, and silicon. The location of the star in the depths of the Milky Way suggests that it is rich in metal. After the fusion of heavy elements, its core will begin to produce iron, upsetting the balance of gravity and radiation, which will lead to the appearance of a supernova. This will happen in a million years - not very long by astronomical standards, but humanity has time to prepare for such an enchanting spectacle.
After a supernova, UY Scuti is likely to turn into a yellow hypergiant, a blue variable star, or even a Wolf-Rayet star with a very high temperature and luminosity. In the latter case, it will “give birth” to many new stars after its supernova.
In fact, this question is not as simple as it seems. It is very difficult to determine the exact sizes of stars, it is calculated on the basis of a lot of indirect data, because we cannot see their disks directly. Direct observation of the stellar disk has so far been carried out only for some large and nearby supergiants, and there are millions of stars in the sky. Therefore, it is not so easy to determine which is the largest star in the Universe - you have to rely mainly on calculated data.
In addition, for some stars, the boundary between the surface and the huge atmosphere is very blurred, and it is difficult to understand where one ends and the other begins. But this is an error not for some hundreds, but for millions of kilometers.
Many stars do not have a strictly defined diameter, they pulsate, and become either larger or smaller. And they can change their diameter very significantly.
In addition, science does not stand still. More and more accurate measurements are being made, distances and other parameters are being refined, and some stars suddenly turn out to be much more interesting than they seemed. This also applies to sizes. Therefore, we consider several candidates that are among the largest stars in the universe. Note that all of them are located not too far in space terms, and they are also the largest stars in the Galaxy.
A red hypergiant that claims to be the largest star in the universe. Alas, it is not, but very close. It is in third place in terms of size.
VV Cephei - that is, double, and the giant in this system is component A, which will be discussed. The second component is an unremarkable blue star, 8 times the size of the Sun. But the red hypergiant is also a pulsating star, with a period of 150 days. Its dimensions can vary from 1050 to 1900 solar diameters, and at its maximum it shines 575,000 times brighter than our star!
This star is located 5000 light-years away from us, and at the same time it has a brightness of 5.18 m in the sky, that is, with a clear sky and good eyesight, it can be found, and even with binoculars it’s generally easy.
UY Shield
This red hypergiant is also striking in its size. Some sites mention it as the largest star in the universe. Refers to semi-regular variables and pulsates, so the diameter can vary - from 1708 to 1900 solar diameters. Just imagine a star, 1900 times larger than our Sun! If you place it in the center of the solar system, then all the planets, up to Jupiter, will be inside it.
Sun, Sirius, Pollux, Arcturus, against UY Shield. It is probably the largest star in the universe.
In numbers, the diameter of this one of the largest stars in space is 2.4 billion kilometers, or 15.9 astronomical units. 5 billion suns could fit inside it. It shines 340,000 times stronger than the Sun, although the surface temperature is much lower due to its larger area.
At its peak, UY Scutum is visible as a faint reddish star with a brightness of 11.2 m, which means that it can be seen in a small telescope, but it is not visible to the naked eye. The fact is that the distance to this large star is 9500 light years - we would not see another on it at all. In addition, there are clouds of dust between us - if they were not there, UY Scutum would be one of the brightest stars in our sky, despite the huge distance to it.
UY Scutum is a huge star. It can be compared with the previous candidate - VV Cephei. They are about the same at the maximum, and it is not even clear which one is larger. However, there is definitely an even bigger star!
VY Canis Major
The diameter of VY, however, according to some sources, is estimated at 1800-2100 solar, that is, this is a clear champion among all other red hypergiants. If it were at the center of the solar system, it would swallow up all the planets, along with Saturn. Previous candidates for the title of the largest stars in the universe would also fit into it completely.
It only takes 14.5 seconds for light to circle our Sun completely. To go around VY Canis Major, the light would have to fly 8.5 hours! If you dared to make such a flyby along the surface in a fighter jet, at a speed of 4500 km/h, then such a non-stop journey would take 220 years.
Size comparison of the Sun and VY Canis Major.
This star still raises a lot of questions, since its exact size is difficult to establish due to the diffuse corona, which has a much lower density than the sun. And the star itself has a density thousands of times less than the density of the air we breathe.
In addition, VY Canis Majoris is losing its substance and has formed a noticeable nebula around itself. This nebula may now contain even more matter than the star itself. In addition, it is unstable, and in the next 100 thousand years it will explode in a hypernova. Fortunately, it is 3900 light years away, and this terrible explosion does not threaten the Earth.
This star can be found in the sky with binoculars or a small telescope - its brightness varies from 6.5 to 9.6 m.
What is the largest star in the universe?
We looked at some of the largest stars in the universe known to scientists today. Their size is amazing. All of them are candidates for this title, but the data is constantly changing - science does not stand still. According to some reports, the UY of the Shield can also "swell" up to 2200 solar diameters, that is, become even larger than VY Canis Major. On the other hand, there is too much controversy about the size of VY Canis Majoris. So these two stars are almost equal candidates for the title of the largest stars in the universe.
Which of them will turn out to be more in fact, will be shown by further research and clarification. While the majority is in favor of UY Shield, and you can safely call this star the largest in the Universe, it will be difficult to refute this statement.
Of course, it is not very correct to speak about the entire Universe. Perhaps this is the largest star in our Milky Way galaxy known to scientists today. But since even larger ones have not yet been discovered, it is still the largest in the Universe.
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