Stars are very important objects. They give light, warmth, and also give life. Our planet, people and everything around us is created from stardust (97 percent to be precise). And stars are a constant source of new scientific knowledge, since they are sometimes able to demonstrate such unusual behavior that it would be impossible to imagine if we did not see it. Today you will find "ten" of the most unusual such phenomena.
Future supernovae may shed
Supernova fading usually occurs in just a few weeks or months, but scientists have been able to study in detail another mechanism of cosmic explosions known as fast-evolving luminous transient (FELT). These explosions have been known for a long time, but they occur so quickly that it was not possible to study them in detail for a long time. At their peak luminosity, these flares are comparable to type Ia supernovae, but they proceed much faster. They reach their maximum brightness in less than ten days, and in less than a month they completely disappear from view.
The Kepler space telescope helped to study the phenomenon. FELT, which happened 1.3 billion light years away and received the designation KSN 2015K, was extremely short even by the standards of these fleeting flares. It took just 2.2 days for the brilliance to build up, and in just 6.8 days, the brightness exceeded half its maximum. Scientists have found that this intensity and transience of the glow is not caused by the decay of radioactive elements, a magnetar or a black hole that might be nearby. It turned out that we are talking about a supernova explosion in a "cocoon".
In the later stages of life, stars can shed their outer layers. Usually, not too massive luminaries, which are not threatened by the prospect of exploding, part with their substance in this way. But with future supernovae, apparently, an episode of such a "molt" can occur. These last stages of stellar life are not yet well understood. Scientists explain that when a shock wave from a supernova explosion collides with the material of the ejected shell, a FELT occurs.
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Magnetars are capable of producing extremely long gamma-ray bursts
In the early 90s, astronomers discovered a very bright and long-lasting emission of radio emission, which in strength could rival the most powerful known source of gamma radiation in the Universe at that time. He was nicknamed "the ghost". The very slowly decaying signal has been observed by scientists for almost 25 years!
Normal gamma ray emissions last no more than a minute. And their sources, as a rule, are neutron stars or black holes, colliding with each other or sucking in "gaping" neighboring stars. However, such a prolonged emission of radio emission showed scientists that our knowledge of these phenomena is practically minimal.
As a result, astronomers still found out that the "ghost" is located inside a small galaxy at a distance of 284 million light years. Stars continue to form in this system. Scientists consider this area a special environment. Previously, it was associated with fast radio flares and the formation of magnetars. The researchers suggest that one of the magnetars, which is the remnant of a star that, during its lifetime, was 40 times the mass of our Sun, was the source of this super-long gamma-ray burst.
A neutron star with a rotation speed of 716 revolutions per second
About 28,000 light-years away in the constellation of Sagittarius is the globular cluster Terzan, where one of the main local attractions is the neutron star PSR J1748-2446ad, which rotates at 716 revolutions per second. In other words, a piece with the mass of two of our Suns, but with a diameter of about 32 kilometers, rotates twice as fast as your home blender.
If this object were a little larger and rotated even a little faster, then, due to the speed of rotation, its pieces would be scattered throughout the surrounding space of the system.
White dwarf, "resurrecting" itself at the expense of a companion star
Cosmic X-rays can be soft or hard. For soft, only gas heated to several hundred thousand degrees is required. The hard one requires real space "ovens" heated to tens of millions of degrees.
It turns out that there is also "super soft" X-ray radiation. It can be created by white dwarfs, or at least one, which will now be discussed. This object is ASASSN-16oh. Having studied its spectrum, scientists discovered the presence of low-energy photons in the soft X-ray range. Scientists first hypothesized that this was due to fickle thermonuclear reactions that could be triggered on the surface of a white dwarf, fueled by hydrogen and helium pulled from a companion star. Such reactions should begin suddenly, briefly covering the entire surface of the dwarf, and then subside again. However, further observations of ASASSN-16oh led scientists to a different assumption.
According to the proposed model, the partner of the white dwarf in ASASSN-16oh is a loose red giant, from which it intensively pulls matter. This substance approaches the surface of the dwarf, spiraling around it and heating up. It was his X-ray radiation that was recorded by scientists. Mass transfer in the system is unstable and extremely fast. Ultimately, the white dwarf will "eat" and light up a supernova, destroying its companion star in the process.
A pulsar burning out its companion star
Usually, the mass of neutron stars (it is believed that pulsars are neutron stars) is on the order of 1.3-1.5 solar masses. Previously, the most massive neutron star was PSR J0348 + 0432. Scientists have found that its mass is 2.01 times that of the sun.
The neutron star PSR J2215 + 5135, discovered in 2011, is a millisecond pulsar with a mass approximately 2.3 times the mass of the Sun, making it one of the most massive neutron stars of more than 2,000 known so far.
PSR J2215 + 5135 is part of a binary system in which two gravitationally bound stars revolve around a common center of mass. Astronomers also found that objects revolve around the center of mass in this system at a speed of 412 kilometers per second, making a complete revolution in just 4.14 hours. The companion star of the pulsar has a mass of only 0.33 solar, but is several hundred times larger in size than its dwarf neighbor. True, this does not in any way prevent the latter from literally burning out with its radiation that side of the companion that is facing the neutron star, leaving its far side in the shadow.
The star who gave birth to a companion
The discovery was made when scientists were observing the star MM 1a. The star is surrounded by a protoplalent disk and scientists hoped to see in it the rudiments of the first planets. But what was their surprise when, instead of planets, they saw in him the birth of a new star - MM 1b. This was observed by scientists for the first time.
The described case, according to the researchers, is unique. Stars usually grow in "cocoons" of gas and dust. Under the influence of the force of gravity, this "cocoon" is gradually destroyed and turns into a dense disk of gas and dust, from which the planets are formed. However, the MM 1a disk turned out to be so massive that instead of planets, another star was born in it - MM 1b. Experts were also surprised by the huge difference in the mass of the two luminaries: for MM 1a it is 40 solar masses, and MM 1b is almost twice lighter than ours.
Scientists note that stars as massive as MM 1a only live for about a million years and then explode like supernovae. Therefore, even if MM 1b manages to acquire its own planetary system, this system will not last long.
Stars with bright comet-like tails
With the ALMA telescope, scientists have discovered comet-like stars in the young but very massive star cluster Westerlund 1, located about 12,000 light-years away in the direction of the southern constellation of Ara.
The cluster contains about 200,000 stars and is relatively young by astronomical standards - about 3 million years, which is very small even in comparison with our own Sun, which is about 4.6 billion years old.
While examining these luminaries, scientists noted that some of them have very lush comet-like "tails" of charged particles. Scientists believe these tails are created by powerful stellar winds generated by the most massive stars in the cluster's central region. These massive structures cover significant distances and demonstrate the effect that the environment can have on the formation and evolution of stars.
Mysterious pulsating stars
Scientists have discovered a new class of variable stars called Blue Large-Amplitude Pulsators (BLAPs). They are distinguished by a very bright blue glow (temperature 30,000K) and very fast (20-40 minutes), as well as very strong (0.2-0.4 magnitudes) pulsations.
The class of these objects is still poorly understood. Using the technique of gravitational lensing, scientists, among about 1 billion studied stars, were able to detect only 12 such luminaries. As they pulsate, their brightness can change by up to 45 percent.
There is speculation that these objects are evolved low-mass stars with helium shells, but the exact evolutionary status of the objects remains unknown. According to another assumption, these objects may be strange "merged" binary stars.
Dead star with halo
Around the radio quiet pulsar RX J0806.4-4123, scientists have discovered a mysterious source of infrared radiation stretching about 200 astronomical units from the central region (which is about five times farther than the distance between the Sun and Pluto). What is it? According to astronomers, it could be an accretion disk or nebula.
Scientists have considered various possible explanations. The source cannot be an accumulation of hot gas and dust in the interstellar medium, since in this case the circumstellar matter should have been scattered due to intense X-ray radiation. It also ruled out the possibility that this source is actually a background object like a galaxy and is not located near RX J0806.4-4123.
According to the most likely explanation, this object may be a cluster of stellar matter that was ejected into space by a supernova explosion, but was then pulled back to the dead star, forming a relatively wide halo around the latter. Experts believe that all these options can be tested using the James Webb Space Telescope, which is still under construction.
Supernovae can destroy entire star clusters
Stars and star clusters form when a cloud of interstellar gas collapses (contracts). Within these increasingly dense clouds, separate "clumps" appear, which, under the influence of gravity, are attracted closer and closer to each other and, finally, become stars. After that, the stars "blow out" powerful streams of charged particles, similar to the "solar wind". These streams literally sweep the remaining interstellar gas out of the cluster. In the future, the stars forming the cluster can gradually move away from each other, and then the cluster disintegrates. All this is happening rather slowly and relatively calmly.
More recently, astronomers have discovered that supernova explosions and the appearance of neutron stars, which create very powerful shock waves that eject star-forming matter from the cluster at a speed of several hundred kilometers per second, can contribute to the decay of star clusters, thereby depleting it even faster.
Despite the fact that neutron stars usually account for no more than 2 percent of the mass of the total mass of star clusters, the shock waves they create, as shown by computer simulations, can quadruple the decay rate of star clusters.
Nikolay Khizhnyak
