Astronomy is special to the entire humanity because of the ultimate truths which are concealed by its baffling beauty. The subject which creates the initial spark of curiosity in the human mind. This beautiful field of science makes us to look beyond our limits and to unravel the cause of many inexplicable miracles.
You might have heard many stories related to the formation of the Earth, moon, and many of our planets. But We cannot look into the past to prove or disprove them. What we can do is just to observe another young growing stellar system that is comparable to our own. We can learn our past by observing the various events through which that stellar system going on. And we are lucky to have few of them..yeah, the stellar system named AU Microscopii. Nice and funny name isn’t it? Right now you might have got a clue about the constellation to which this star belongs. Yep, the Microscopium. This M-type dwarf star is actually not that much funny and calm as you might have thought at the first.
AU Mic (AU Microscopii) is a very young star about 150 times younger than our Sun. This star posses a big disk of debris. It is only 31.9 light-years away from us. This star has very powerful stellar flares because of its strong magnetic field and the resulting starspots. Never judge this young dwarf by its size; because in July 2018, NASA’s TESS (Transiting Exoplanet Survey Satellite) witnessed many huge gigantic stellar flares that are more powerful than the ever recorded flare on our Sun. Majority of the heat generated on this young dwarf is due to the compression occurring at the interior of the star due to its gravity. Only 10% of its energy is coming from fusion at its core.
Due to its powerful magnetic nature and frequently occurring stellar flares scientist was struggling to find an exoplanet around this dwarf using the normal transit method. In the transit method, we are observing the dip in the brightness of the star when a planet passes in front of it. But then comes its stellar flares as the mask to trick us and confuse us. TESS was not lazy to leave the mission. It continuously observed this elusive object. The team behind the observation collected the data and removed the effects of stellar flares from the brightness graph. At last, they find the one which they were looking for. Yeah, an exoplanet. They named it as AU Mic b.
Even though we found planets around its nearby star called Beta Pictoris (hotter A-type star that harbors two planets and is likewise surrounded by a debris disk.), this planet has many peculiarities and could explain the formation of our solar system very well. AU Mic b is almost similar to our Neptune. This new exoplanet has a mass less than 58 times that of our Earth. But Beta Pictoris b and c, are 50 times or more massive than our Earth. Another interesting thing found was that AU Mic b can complete its orbit within 8.5 days. Yeah, this planet is almost very closer to its host star.
TESS has also done an important observation about the origin of AU Mic b. This planet is believed to be formed far away from the star and later migrated towards the star due to its gravitational interaction with the gas disk or with other planets. This is not the case of Beta Pictoris b and c. Those planets haven’t migrated that much from its birthplace. And also these planets take 21 and 3.3 years, respectively, to complete one orbit around its host star.
In order to confirm the presence of this new exoplanet around the star, TESS required to observe 2 more transit. But at the time of second transit TESS was downlinking the data stored inside. So it couldn’t do its observation. Then comes our veteran Space Telescope, Spitzer. Spitzer got this task at the time when it was counting its last days of life. It did the job very well for its young companion telescope, TESS. Spitzer observed the 2 additional transit and hence proved that the object TESS found was an exoplanet. The detailed observations done by both of these two telescopes and observatories on Earth, scientist calculated the exact size of the planet and its mass. As per the observation, this new exoplanet is 8% larger than our Neptune.
With the help of these two space telescopes, we got many important data that can explain the formation of our Solar System and how the planets evolved and their future. We can soon expect many more important observation from TESS. Recently, TESS got a clue for the presence of another planet around AU Mic. So we can hopefully wait for the discovery of more planets around AU Microscopii.
Reference : NASA
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