10 Champions among the stars

 

To paraphrase the famous classic, we can say that all the lucky stars like one another, and the most incredible of them and problem is unique. The universe is full of stars. But even amidst all this indescribable variety of cloth pieces worthy of attention.

Star-centenarians

How long may a star live? First, let's define: lifetime of a star we mean its ability to carry out nuclear fusion. Because the "corpse star" may be a long time hanging and after synthesis.

As a rule, the less massive the star, the longer it will live. Stars with the lowest mass red dwarfs. They can be ground from 7.5 to 50 percent of the sun. All that is less massive, can't do nuclear fusion — and there will be a star. Modern models suggest that the smallest red dwarfs can Shine up to 10 trillion years. Compare this with our Sun, the synthesis of which will last approximately 10 billion years — a thousand times less. After synthesis, the most part of hydrogen, according to the theory, light red dwarf becomes a blue dwarf, and when the remnants of the hydrogen will be exhausted, fusion in the core stops, and the dwarf will become a white.

The oldest stars

The oldest stars are, it turns out, those that formed just after the Big Bang (about 13.8 billion years ago). Astronomers can estimate the age of stars by looking at their starlight — it tells them how much of each element is in a star (e.g., hydrogen, helium, lithium). The oldest stars usually consist mainly of hydrogen and helium, and very small part of the mass reserved to the heavier elements.

The oldest observed star is SMSS J031300.36-670839.3. Its opening was announced in February 2014. Its age is estimated at 13.6 billion years old and it's still not one of the first stars. Such stars have not been discovered, but they certainly can be. Red dwarfs, as we have noted, live trillions of years, but they are very difficult to detect. In any case, even if those stars are, to find them — like needle in a haystack.

The most faint stars

Which stars the most dull? Before we answer this question, let's understand what "dull". The farther you are from the star, the dimmer it looks, so we just need to take distance as a factor and measure its brightness, or the total amount of energy radiated by the star in the form of photons, particles of light.

If we limit ourselves to stars that are still in the process of synthesis, low luminosity red dwarfs. The coolest star with the lowest luminosity is currently the red dwarf 2MASS J0523-1403. A little less light — and we get into the realm of brown dwarfs, which are stars.

Another may be the remains of stars: white dwarfs, neutron stars and black holes. How dim can they be? White dwarfs a little lighter, but cool for a long time. After some time they turn into cold pieces of coal, almost not emitting light, become "black dwarfs". To cool off, white dwarfs need a lot of time, so their is simply no.

Astrophysicists do not yet know what happens to the substance of neutron stars when they cool down. Observing supernovae in other galaxies, they can assume that in our galaxy should have been formed several hundred million neutron stars, however, there has so far been only a small part of that number. Others had to cool down so that they became invisible.

What about black holes in deep intergalactic space, in orbit with nothing? They still emit a bit of radiation, known as Hawking radiation, but not so much. These single black holes probably glow less than the remaining stars. Do they exist? Possible.

The brightest stars

The brightest stars also tend to be very massive. They also have the custom to be stars, wolf-Rayet, which means they are hot and drained a lot of mass in a strong stellar wind. The brightest stars also do not live very long: "live fast, die young".

The most brightest star (and most massive) is considered a luminary R136a1. Its discovery was announced in 2010. This is the star wolf-Rayet with a luminosity of approximately 8 700 000 solar and a mass 265 times greater than our home star. Once her weight was 320 Sunny.

R136a1 is actually part of a dense cluster of stars called R136. According to Paul Crowther, one of the discoverers, "the planets need more time to form than a star — to live and die. Even if there were planets, no astronomers on them would not be, because the night sky was as bright as day.

The largest stars

Despite the huge mass, R136a1 is not the largest star (in size). There are many stars bigger and they are red supergiants — stars that life was a lot less, until run out of hydrogen, began to synthesize helium, not the increase in temperature and expansion. Our Sun eventually expects the same fate. Hydrogen will end and light will expand, becoming a red giant. To become a red supergiant, a star need to be 10 times more massive than our Sun. The red supergiant phase is usually short, lasting only from a few thousand to billion years. It's a little on an astronomical scale.

The most well-known red supergiants — alpha Antares and Betelgeuse, but they are quite small compared to the largest. Find the largest red supergiant — a very fruitless undertaking, because the exact sizes of such stars is very difficult to assess for sure. The largest should be 1,500 times wider than the Sun, and maybe more.

Star with the brightest explosions

High-energy photons called gamma rays. They are born as a result of nuclear explosions, so individual countries are launching special satellites to search for gamma rays caused by nuclear tests. In July 1967, these satellites for authorship, the U.S. found a gamma-ray burst, which was not caused by a nuclear explosion. Since it was discovered many more such explosions. They are generally of short duration, lasting from several milliseconds to several minutes. But very bright, much brighter than the brightest stars. The source is not on Earth.

What causes explosions gamma rays? Guesswork mass. Today most of the theories boils down to the explosions of massive stars (supernova or Hypernova) in the process of becoming a neutron star or black hole. Some gamma-ray bursts are caused by magnetherapy, a kind of neutron stars with very strong magnetic field. Other gamma-ray bursts may be the result of the merger of two neutron stars or one star falling into the black hole.

The coolest former star

Black holes are not stars, but their remains — but it's fun to compare with the stars because such comparisons show just how incredible you can be and those and others.

A black hole is what occurs when the gravity of the star is strong enough to overcome all other forces and cause the star to collapse to itself to the point of singularity. With non-zero mass, but zero volume is a point in the theory will have infinite density. However, infinity in our world are rare, so we have no good explanation of what is happening in the center of a black hole.

Black holes are extremely massive. The black holes found in the centers of the individual galaxies may be tens of billions of solar masses. Moreover, the matter orbiting supermassive black holes can be very bright, brighter than all the stars of galaxies. Near a black hole can also be powerful jets moving at nearly the speed of light.

The fast-moving stars

In 2005, Warren brown and other astronomers from the Harvard-Smithsonian center for astrophysics announced the discovery of a so fast moving stars that she flew out of the milky Way and never come back. Its official name is SDSS J090745.0+024507 but brown called it "a star-an outcast.

Was discovered swift and other stars. They are known as hypervelocity stars hypervelocity stars), or a super-fast stars. As of mid-2014 was found 20 such stars. Most of them seem to come from the galactic center. According to one hypothesis, a pair of closely bound stars (a binary system) passed close to a black hole in the center of the galaxy, one star was captured by a black hole, and the other is ejected at high speed.

There are stars that are moving faster. In fact, generally speaking, the farther a star is from our galaxy, the faster it is removed from us. This is due to the expansion of the Universe, and not the movement of stars in space.

The most variable stars

The brightness of many stars varies greatly, if you look at them from the Ground. They are known as variable stars. A lot of them: in the milky Way galaxy numbered about 45,000 of these.

According to the Professor of astrophysics Coelho, Hale, the most variable of these stars are cataclysmic or explosive variable stars. Their brightness may increase by a factor of 100 during the day, decrease, increase again and so on. Such stars are popular with Amateur astronomers.

Today we have a good understanding of what is happening with the cataclysmic variable stars. They constitute binary systems where one star is normal and the other is a white dwarf. Matter from the ordinary star falls into the accretion disk that rotates around a white dwarf. After the mass of the disc is high enough, the synthesis begins, resulting in an increase of brightness. The synthesis of gradually dries up and the process begins again. Sometimes the white dwarf collapses. Development options enough.

The most unusual stars

Some types of stars is quite unusual. They need not be different extreme characteristics like luminosity or mass, they're just weird.

As, for example, the objects of Thorne-Zhitkov. They are named in honor of physicist Kip Thorne and Anna Zhitkov, who first suggested their existence. Their idea was that a neutron star can become the core of a red giant or supergiant. The idea is incredible, but... such object was recently discovered.

Sometimes two large yellow stars circling so close to each other that regardless of the matter, which is between them, like a giant space peanuts. Known only two such systems.

Star Przybylski sometimes given as an example of an unusual star because her star light is different from light of any other star. Astronomers measure the intensity of each wavelength to find out what is in the star. Usually it is not so difficult, but scientists are still trying to understand the spectrum of Przybylski stars.

Source: planetologia.ru/