The existence of a third star in the Fomalhaut system

It is the 18th brightest star in our night sky and one of the few stars possess an extended circumstellar disk of gas and dust. Of course, it is the main star in the constellation Piscis Austrinus and it is out of the ground about 25 light years.  Let’s talk about Fomalhaut, at the center of a recent and interesting discovery.


So far it has always been thought that Fomalhaut was a binary star system, which moves in tandem with the nearby star TW Piscis Austrinus, also known as Fomalhaut B (not to be confused with Fomalhaut b, with the tiny exoplanet, which is a candidate that seems to be part of the system).  Now, researchers at the University of Rochester have shown that in fact it is a system consisting of three stars.  In a study published in the Astronomical Journal, astronomers have shown that a nearby star is much smaller and it is part of the system.  Researchers led by Eric Mamajek had to work a lot to find Fomalhaut C.  “I noticed this third star about two years ago when I was studying the movements of stars near Fomalhaut to another study,” said Mamajek.  “I had to still collect more data and combine it with other observations to determine the characteristics of this star”.  In addition to a series of specific observations, the researchers have argued that the discovery was entrusted to the case.  What until that moment was known as LP-10 876 proved then, thanks to the simple calculation of Parallax, the Fomalhaut system.  “Fomalhaut C looks pretty distant from the bigger star (Fomalhaut) if you look into the sky from the Earth,” affirms Mamajek.



There are, in fact, about 5.5 degrees between the two stars, and that is why until now it had never been suggested a link between the two.  It is very likely that the two stars move in unison.  “Fomalhaut is a massive star, twice the mass of the Sun, and thus can exert enough gravitational attraction to keep connected with this small which is at 158 miles far more distant from her than the Earth is from the Sun”. Many of the comments have been made thanks to the SMARTS telescope from 0.9 meters to Cerro Tololo in Chile.  There are other 11 multiples stellar systems much closer to the Sun than Fomalhaut, such as Alpha Centauri, but analyzed by Mamajek is the largest and massive ever studied so far.  One of the mysteries that have always fascinated scholars of this star system is the circumstellar disk of gas and dust that surrounds it, very similar to that of exoplanets.  In 2006, Alice Quillen, Mamajek’s colleague, she predicted the existence of a planet near Fomalhaut, studying the debris in the disk and its orbit.  But doubts remain: Fomalhaut b, the planet in question would have in fact a very eccentric orbit and the debris do not seem to be centered on Fomalhaut.  All this probably is due to the effect of the orbits of the three stars.  While Fomalhaut C is a red dwarf – the most common type of star in the universe – Fomalhaut B is an orange dwarf star approximately three quarters the mass of our Sun. The trio’s age is around 440 million years – about a tenth of the age of our solar system.

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