Tag: black hole

  • What if the Sun Became a Black Hole?

    What if the Sun Became a Black Hole?

    It is hard to argue that the sun is incredibly beneficial. It gives us light and warmth, keeps water in a liquid state, and helps plants photosynthesize. It would be extremely sad if something happened to our star—for example, if it turned into a black hole.

    Strictly speaking, in reality, the sun cannot become a black hole because it is not heavy enough. For example, the mass of the smallest known black holes is between 3.66 and 4.97 times the mass of our star. Theoretically, smaller black holes could exist, weighing just about 2.7 times the mass of the Sun. However, astronomers have yet to observe them through their radio telescopes.

    In other words, the sun would need to be at least 2.7 times heavier to turn into a black hole. And even then, it’s not guaranteed that it would succeed.

    However, not only have we imagined the Sun turning into a black hole, but we have also lost it altogether, flown through Jupiter, and experimented on the Moon—so why not try new experiments?

    So, let’s imagine the star suddenly turns into a black hole of equivalent mass—how would this affect our lives?

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    Well, for the first 8 minutes, or more precisely, 499 seconds, we wouldn’t notice anything because light takes time to reach Earth. After that, the sun would simply disappear, and eternal night would fall—only distant stars would illuminate the sky. They would be visible 24 hours a day, which, you have to admit, would significantly simplify astronomical observations.

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    Perhaps you imagine a beautiful, massive black hole appearing in the sky, like Gargantua from Interstellar or Sagittarius A* at the center of our galaxy, which was photographed by astronomers from the European Southern Observatory in 2022.

    But no. Those are supermassive objects surrounded by large accretion disks of matter falling into them. A black hole formed from the sun would have a radius of only 3 kilometers. You wouldn’t even be able to see it through a telescope.

    Moreover, our new system’s black hole wouldn’t have any material to absorb and form an accretion disk—there are no nearby stars or nebulas to consume. As a result, the hole would be dark, unnoticeable, and lacking the beautiful orange special effects.

    But don’t worry; this transformation has many advantages.

    The Earth and all other planets would continue to orbit around our black hole just as they do now. Since its mass remains unchanged, the gravitational influence would stay the same.

    Black holes are stable and last for a very long time. In theory, they slowly lose mass and disappear—this is called Hawking radiation. But this process is slow, and we would no longer need to fear that in 3 billion years, the Sun will boil the oceans, or in 5 billion years, it will turn into a red giant and engulf the Earth.

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    Specialists from McGill University in Montreal calculated the evaporation time for a black hole with the mass of the Sun due to Hawking radiation—10⁶⁷ years. And as you can see, this is far longer than the current age of the universe.

    So, our new system would continue to revolve for an incredibly long time, and the planets wouldn’t collide with one another.

    However, there are some minor drawbacks to this scenario. Due to the lack of sunlight, civilization would need to move underground, closer to the core, build highly efficient nuclear reactors, and melt drinking water using artificial heating. This technological challenge would give an unprecedented boost to scientific development.

    Or we could all just freeze and die.

  • Unusual Star Death at the Black Hole

    Unusual Star Death at the Black Hole

    Astronomers have seen a rare occurrence of stellar death around a black hole, with the star rupturing and sending forth jets of plasma and radiation. A tidal disruption event (TDE) was initially seen in all wavelengths, from radio to gamma rays, because one of these jets was directed straight toward Earth. This is an extremely rare occurrence. These findings provide the first hints as to why black holes only create a jet in roughly 1% of these star deaths.

    The star AT2022cmc’s death is so remarkable.

    When a star approaches too closely to a supermassive black hole, it is “spaghettified” into spaghetti-like strands by the tidal forces of the black hole’s tremendous gravity. Part of the star’s material forms an accretion disk that rotates around the event horizon and is progressively consumed in a “tidal disruption event” (TDE). One percent of the time, extra paired jets are generated, which are clusters of highly accelerated plasma and high-energy radiation that go far into space.

    Very few TDEs (less than one percent) have been seen to have jets.
    Very few TDEs (less than one percent) have been seen to have jets. (Credit: ESO)

    However, it is not understood why these powerful jets manifest themselves in just a subset of TDEs. Since we have only witnessed a few of these jet TDEs, as coauthor Nial Tanvir of the University of Leicester puts it, they remain an exceedingly exotic and poorly known phenomenon.

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    Only a small fraction of the radiation spectrum was able to detect the last such event in 2011, therefore we still don’t know much about the mechanisms behind these stellar deaths.

    An Unexpected Explosion in a Faraway Galaxy

    This may have altered, however, thanks to an example of such a stellar death that is both severe and instructive. A telescope at California’s Zwicky Transient Facility (ZTF) saw it on February 11, 2022. Initially, researchers headed by Igor Andreoni of the University of Maryland assumed a gamma-ray burst was the cause of a sudden, very intense flash of light picked up by the telescope.

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    When a star gets too near a black hole, it is eaten. The AT2022cmc event is the furthest one seen thus far.
    When a star gets too near a black hole, it is eaten. The AT2022cmc event is the furthest one seen thus far. (Credit: Caltech/IPAC, Zwicky Transient Facility/R. Hurt)

    The scientists notified other observatories that saw the radiation burst, which they named AT2022cmc, in all wavebands, from long-wave radio radiation to infrared and optical light to short-wave X-rays and gamma rays, to determine its origin. Initial spectral investigations placed the origin of this radiation at a distance of about 8.5 billion light-years from Earth.

    Odd Characteristics

    However, AT2022cmc’s X-ray, radio, and submillimeter beams are among the brightest ever seen at such a redshift. These high levels of radiation intensity lasted for weeks, unlike a gamma-ray burst. Dheeraj Pasham of the Massachusetts Institute of Technology (MIT) claims that this event was one hundred times brighter than the brightest previously recorded gamma-ray burst afterglow. Furthermore, the X-ray intensity remained wildly changing instead of progressively reducing.

    The visible and ultraviolet light trends were also unexpected. After dramatically varying for days, it finally settled into a plateau where it was still extremely bright but had a slightly blue hue. Andreoni and coworkers note that the AT2022cmc stands out even among the growing list of transient astronomical phenomena due to its very high brightness across all wavelengths and fast spectral and temporal variation.

    A Death Ray From a Star Aimed Right at Humanity

    All of these attributes point to a tidal disruption event involving a distant black hole as the likely cause of the AT2022cmc’s bright appearance. According to researcher Benjamin Gompertz of the University of Birmingham, AT2022cmc’s brightness and duration were so extreme that they suggested the presence of a supermassive black hole. High-energy jets, one of which was pointed straight at Earth, were created when a star similar in size to the Sun exploded near the black hole.

    This is not only one of the very unusual examples of a shattered star with accompanying jets, after all. It’s also the farthest-away event discovered so far, at a staggering distance of 8.5 billion light-years. Coauthor Giorgos Leloudas of the Technical University of Denmark adds that the increased brightness and visibility throughout a larger range of the electromagnetic spectrum is due to the fact that the relativistic jet is pointed in our direction.

    black hole

    At Almost the Speed of Light

    For the first time, astronomers were able to get insight into the circumstances surrounding a star’s death and the jets that resulted. The chain of events started when a star on its deathbed flew dangerously close to the supermassive black hole on a nearly parabolic trajectory, ripping itself apart into a jet of gaseous debris. The accretion ring around the black hole was severely heated and accelerated to almost half the mass of the shattered dwarf star.

    Two polar jets of high-energy particles and radiation were formed as a result of the turbulence and shock waves. Matteo Lucchini, also from MIT, reveals that, based on the calculations, the jet travels at a speed that is 99.9 percent as fast as light. However, contrary to popular belief, the presence of a high magnetic field was not the driving reason behind the massive acceleration necessary for this kind of TDE with a jet. This field was hardly noticeable in AT2022cmc.

    The Role of the Black Hole’s Rotational Axis

    On the contrary, the data point to the black hole’s spin as a key factor in the development of the plasma and jet bundles. This means that such jets might occur whenever the supermassive black hole revolves around itself after ripping away a star. Given that not all black holes exhibit this property, TDEs accompanied by jets are very uncommon.

    More of these occurrences should be observable in the future. Lucchini adds that this would allow us to explain why and how black holes trigger these jets.

    The studies may be found in Nature (2022): 10.1038/s41586-022-05465-8 and Nature Astronomy (2022): 10.1038/s41550-022-01820-x.

  • How Quasars Produce the Brightest Light in the Universe

    How Quasars Produce the Brightest Light in the Universe

    Quasars are cosmic lighthouses, and astronomers have figured out how they produce their powerful radiation that can be detected over billions of light-years. Particles driven by these black holes and then encountering a shock wave and being quickly decelerated create the most intense fraction of this radiation, according to this research. The resulting synchrotron radiation is most prominent in the X-ray spectrum.


    According to their findings published in “Nature,” researchers have shown that longer-wavelength radiation components do not appear until much later in the process.

    Quasars shine brighter than anything else in the universe. Active galactic nuclei emit powerful cones of radiation that may illuminate the surrounding space for billions of light-years, rivaling the brightness of hundreds of trillions of suns. The supermassive black hole at the heart of these distant galaxies is the source of this tremendous radiant power, which it generates by ingesting vast quantities of matter and then releasing this energy in the form of accelerated particles and radiation. Blazars are another name for quasars, whose radiation and particle jets are directed at our planet.

    Extra Energy When They Are Slowed or Diverted

    However, until recently, it remained unclear exactly how quasars generate their radiation. In both observations and simulations, the massive jets of highly accelerated particles have been implicated as the origin of the energetic emissions. It is possible for these particles to radiate extra energy when they are slowed or diverted, much as particles are accelerated in particle accelerators or synchrotron facilities with X-ray lasers.

    Whether the rapid particles in the jet of the quasars are slowed down all at once at a shock wave or more gradually throughout the jet in turbulence is yet unknown. The polarization of the radiation is one way to tell them apart; if the quasar’s radiation is very directed, then the source must be highly concentrated and uniform across the jet.

    However, until recently, the polarization of quasar radiation could only be detected in the radio and optical wavelength ranges, and these measurements looked to reveal relatively dispersed, turbulent source zones. There was a shortage of data like this for high-energy X-rays.

    Blazars

    However, in December 2021, a new space telescope was deployed into orbit, making it possible for the first time to determine the polarization of cosmic X-rays. As a result, the Imaging X-ray Polarimetry Explorer (IXPE) offers a more detailed view of the emission zone of quasars than was previously feasible.

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    The researchers analyzed the radiation from the blazar Markarian 501 using data gathered by the IXPE spacecraft. Since it is “just” 450 million light-years away, the radiation from this active galactic nucleus is unusually strong and may be easily measured. In March of this year, it became the first blazar to be seen using an X-ray polarimeter. Simultaneously, a plethora of additional observatories managed to record this quasar’s light at the remaining wavelengths.

    Particles Driven by the Black Hole’s Magnetic Fields

    IXPE image of Markarian 501 during the March 2022 observation. The dashed black line shows the jet direction. (Credit: Nature)
    IXPE image of Markarian 501 during the March 2022 observation. The dashed black line shows the jet direction. (Credit: Nature)

    According to the results of the tests, the radiation from the quasar is weakly and unevenly polarized at lower energies. But in contrast, the polarimeter detected polarization of more than 10% in the high-energy X-ray band, at an angle that is consistent with the quasar jet’s direction.

    The source of this X-ray emission can be better understood with the use of these data. According to the scientists, this argues for a shock wave as the cause of the particle acceleration. Particles driven by the black hole’s magnetic fields crash with a zone of slower particles in the jet, releasing this high-energy radiation. They suddenly lose speed and the X-rays are discharged in this shock wave.

    After passing through the quasar jet’s shock wave, the particles keep racing, although at a reduced speed. Therefore, as they recede from this zone, they are now releasing radiation of longer and longer wavelengths. Scientists draw the conclusion that the jet is becoming more turbulent in this area from the fact that the polarization of this lower-energy radiation is not uniform.

    Major Step Forward

    Thus, astronomers have learned, for the first time, what drives the most powerful radiation sources in the galaxy. The findings prove that multiwavelength polarimetry provides a novel method of investigating the physical environment close to supermassive black holes. IXPE and other devices’ future measurement data may shed light on the inner workings of these processes.

    When it comes to comprehending these powerful particle accelerators, many astronomers and physicists consider these findings as a major advancement in our knowledge of blazars. With X-ray polarimetry, scientists can find out whether or not these processes are universal to all quasars, and what part electrons and protons play in the jet during beam formation.