2023 Author: Bryan Walter | [email protected]. Last modified: 2023-05-21 22:24
Looking at the dome of the starry sky on a clear night, it is easy to believe in its inviolability and immobility, but even ancient people noticed that not only the Sun and the Moon move in the sky. Watching night after night, the first astronomers discovered planets, which means "wandering," and that was just the beginning. In fact, the entire Universe is in motion, and only our short human age does not allow us to see the full scale and grandeur of this process. While the observation of motion in space is available to us within the solar system, but the successes of astronomy allow us to look further.
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Starburst light echo
In January 2002, a nondescript variable star in our Galaxy, V838 Unicorn, flared up and became 600,000 times brighter than the Sun. For some time it even became the brightest in the Galaxy, but it quickly faded away. We have witnessed an unusual phenomenon called "light echo". Although we think that a bubble of glowing gas is spreading from the star, what we actually see is different. This flash light leaves the star at the speed of light and illuminates clouds of dust that existed previously, but were invisible in the dark. We can observe the "leisurely" procession of the light wave thanks to the distance of 20 thousand light years.
Supernova explosion charges a ring of gas
The closest to us, during the existence of modern astronomy, supernova 1987A in the Large Magellanic Cloud exploded 30 years ago (more precisely, observations of the explosion became possible in 1987, and it exploded 170 thousand years earlier). At closer distances, for example in our Galaxy, supernova explosions have not been recorded for four centuries, so 1987A is of great interest to science and is being closely monitored. The material of the exploded star travels at a speed of 7 thousand kilometers per second, and in several Earth years it reached the ring of material that encircles the star at a distance of half a light year. This ring appeared much earlier - about 20 thousand years ago, when an exploding star was formed by the merger of two stars. The "fall" of one star into another gave rise to an ejection of matter, which turned into a "diamond necklace" when powerful streams of matter from the 1987 explosion reached it. Now the ring is already fading and should return to its former dull existence in 15-25 years.
In 1995, 2001, and 2008, the Hubble Space Telescope observed the Homunculus Reflection Nebula around the star Eta Carinae. The explosion that gave birth to the nebula occurred in 1841 (excluding the distance of 7,500 light years from the star) and has been the subject of observation ever since. Given the nebula's small age, it remains possible to see its actual growth.
Alien solar system, full face
Seeing planets in alien solar systems is not an easy task. The problem is the brightness of the star around which the planets revolve. The planets themselves practically do not emit, but only reflect light, so they are very dim and their own sun illuminates our telescopes. The odds are better if the planets are gas giants like Jupiter or more. It also helps if the planet rotates far enough from its star. And the ability to observe alien planets is improving with the increasing capabilities of modern telescopes like Keck and data processing algorithms. Result: The visible rotation of the planetary system was recorded near the star HR 8799 Pegasus from a distance of 129 light years. Each of the planets is larger than Jupiter and is located at a greater distance from its star than it is from the Sun. The nearest one describes the annual circle in 40 Earth years, the distant one in four hundred. We see the result of observations over seven years.
Space Robbery Live
The eclipsing binary star Sheliak (Beta Lyrae) demonstrates the interaction of a close system of two stars. Moreover, the process of overflow of matter from one to another is currently observed. The donor star, with a mass of three solar masses, looks brighter and has an elongated shape due to tidal deformations. The robber star has a mass of 13 solar masses. The intensity of the flow of matter from one to another is approximately one mass of the Sun every 50 thousand years. The orbital period of the system is 13 days, the distance to the pair is 960 light years.
Pulsar in Sails
A neutron star in the constellation Vela Pulsar is about a thousand light-years from Earth. It is a bright source of pulsations in the optical, X-ray, gamma and radio ranges of electromagnetic radiation. It appeared about 11 thousand years ago as a result of a type II supernova explosion.
The pulsar has a diameter of about 20 kilometers (it would fit within the Moscow Ring Road) and rotates at a speed of 11 revolutions per second. A series of eight images taken from June to September 2008 from the Chandra space X-ray telescope allowed us to look deep into the gas and dust nebula and see the pulsar jet. A jet is a stream of high-energy particles ejected from the polar regions of a neutron star. The speed of the stream in the jet reaches half the speed of light and extends for half a light year. The frequency of the "beat" of the jet has three periods of 122, 73 and 91 days, which can be explained by the precession of the pulsar.
Barnard's star is one of the closest to us (the distance to it is less than six light years), but it is more interesting because it moves very quickly, by stellar standards, in the earth's sky. For viewers from Earth, this is the "fastest" star after the Sun. It would have crossed the disk of the moon in 174 years, however, even amateur astronomers are able to register its movement relative to other stars in a few years.
Once upon a time, Barnard's Star attracted the attention of astronomers as the owner of the nearest exoplanets. To achieve them, they even proposed a separate spaceship project, but long-term observations did not allow identifying any significant satellites of the star, so now it is in flight and is of interest only to amateurs.
The heartbeat of the Milky Way
Just thirty years ago, the existence of a supermassive black hole at the center of the Milky Way galaxy was not obvious. Hypotheses of a simple star cluster were considered. Progress in optics has made it possible to confirm the presence of a black hole in the center of the Galaxy (or at least an object that meets all of its attributes). The development of adaptive optics and infrared observation of the galactic center has made it possible to see the actual movement of stars around an invisible central object. Although it emits no light at all, this object is a bright source of radio waves known as Sagittarius_A * (Sagittarius A *).
By studying the orbits of nearby stars, it was possible to estimate the mass and size of the object: about four million solar masses, enclosed in a diameter comparable to the orbit of Pluto. Currently, Sagittarius A * is one of the most convincing experimental evidence for the existence of black holes.
The above animation shows the result of astrometric and spectrometric observations from 1992 to 2008. Blue stars are young, red stars are old.
Actual observations are not so clear, but picturesque in their own way:
The original text in the Live Journal of the Green Cat