The brightest and youngest: what science knows about red supergiants

What are red supergiants?

The red supergiant is a massive and very large star. Refers to

spectral type K or M and luminosity class I. Typical representatives of red supergiants are the stars Antares and Betelgeuse.

Description of red supergiants

  • Specifications

Red supergiants are the largest in sizestars. They have a very low effective temperature (3,000–5,000 K) and a radius 200–1,500 times the radius of the Sun. The energy flux per unit area of ​​their surface is small - 2–10 times less than that of the Sun. The luminosity of red supergiants is 500 thousand higher than the luminosity of the Sun.

The red supergiant stage is characteristic of massive (over 10 solar masses) stars and lasts from 10 to 100 million years. Stars of this type are often located in clusters.

The traditional division of stars into red giants andred supergiants is conditional, since it reflects only the difference in the radii and luminosities of stars with a similar internal structure: they all have a hot dense core and a very rarefied extended envelope.

According to the modern theory of stellar evolution, the star falls into the region of the Hertzsprung-Russell diagram, occupied by red giants and red supergiants twice.

  • Properties

Surface temperature of red supergiantsranges from 3,500 to 4,500 Kelvin. Due to their size, they require an incredible amount of energy, which results in a short (relative to other stages of stars) life cycle, which lasts from 10-100 million years.

Comparison with the Sun

Compared to the Sun, Betelgeuse is many times larger. If it is placed in the solar system, then it will take the distance to Jupiter. With a decrease in its diameter, it will border on the orbit of Mars.

The brightness of Betelgeuse is 100,000 times greater than that of the Earth. And the age is 10 billion years. While the Sun is only about 5 billion.

Scientists are increasingly thinking about behaviorBetelgeuse, because the red giant behaves just like the sun. It has localized points where the temperature is higher than another surface and places where the temperature is lower.

Despite the fact that the shape of the sun is spherical, and the red supergiant is in the form of a potato, this is puzzling in scientific circles.

Representatives of red supergiants

In terms of brightness, the red supergiant Betelgeuse ranks 9th in the night sky. Its brightness from 0.2 to 1.9 stellar magnitude changes during 2070 days. Belongs to the spectral class m1-2 la lab.

Star size:

  • The radius of the star is 600 times the diameter of the Sun.
  • And the mass is equal to 20 solar masses.
  • The volume is 300 million times the volume of the Sun.

The atmosphere of the star is rarefied, and the density is much lower than the Sun. Its angular diameter is 0.050 arc seconds. It changes depending on the luminosity of the giant.

The astronomers measured the radius using a spatial IR interferometer. The rotation period of the star was calculated, which is 18 years.

The appearance of the stars

Red supergiants are part of lifecycle of high-mass stars. When the core of a massive star begins to collapse, the temperature rises, causing helium to coalesce. The rapid fusion of helium destabilizes the massive star.

A huge amount of energy pushes out externallayers of a star, which leads to a new life stage - transformation into a red supergiant. At this point, the star's gravitational force is balanced again, and the star loses most of its mass.

Red supergiants are considered the largest stars, but not the most massive, with age they will continue to lose mass.

Explosion of red supergiants

The red giant is in the final stages of burning carbon. Knowing what processes are taking place inside the star, scientists can tell the future of Betelgeuse.

For example, with a rapid explosion, iron, nickel, and gold are formed inside it. A slow explosion produces gases such as carbon, oxygen, barium.

Scientists believe the red supergiant is readygo supernova. A few more thousand years, and maybe even earlier, and this star will explode, unleashing the discarded energy on nearby space objects, since it will release as much energy as the Sun has emitted in its entire life.

When a supergiant runs out of fuel that sustains life. Gravity wins and the core begins to collapse. Ultimately, these stars end their lives as Type II supernovae.

First of all, such an amount of energy released from Betelgeuse can disrupt the operation of satellites, mobile communications and the Internet on the planet. The aurora will become even brighter.

Moreover, the explosion can lead to adverse effects on nature, which will lead to the extinction of some species of animals and a slight cold snap. But these are all assumptions.

A neutron star can form from the remnants of a star's core or, in the case of massive stars, a black hole can be created.

Temperature of red supergiants

Daisuke Taniguchi of the University of Tokyo in Japan and his colleagues have accurately measured the temperature of the photosphere of red supergiants for the first time.

Until recently, scientists could not determine the exact temperature of the photosphere of these stars - the lower layer of their atmosphere, in which most of the star's radiation is formed.

To measure the temperature of a red supergiant,it is necessary to find clearly visible areas of the stellar photosphere, the emission spectrum of which was not influenced by the upper layers of their atmosphere. In addition, there is no one specific absorption line that would unambiguously indicate the surface temperature of such stars.

This is how astronomers determined the temperaturethe photosphere of ten nearby red supergiants. In particular, for Betelgeuse it is 3344.85 degrees Celsius, which is about 1.68 times less than the temperature of the Sun's photosphere.

These newest changes, astrophysicists are sure,will help to understand what processes occur in the bowels of such luminaries, as well as to make the first full-fledged predictions on how close Betelgeuse is to becoming a supernova.

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