Astronomers find extreme and recently erupted young stellar object

YSOs are stars in the early stages of evolution, specifically protostars and pre-main sequence stars.

Recall that a protostar is a star at the initial stage of its evolution and at the final stage of its formation before the occurrence of thermonuclear fusion.The exact boundaries of this concept are blurred, and the protostars themselves can have very different characteristics.In turn, the stars up to the main sequence, unlike theprotostars are already visible in the optical range.Thermonuclear reactions take place, but not enough energy is released in them to compensate for the energy losses due to the radiation of the star.

They are usually found enclosed in dense molecular clumps, in an environment containing large amounts of molecular gas and interstellar dust.

Considering that YSO has occasionalaccretion processes, as a result of this, outbreaks are observed in stars in the early stages of evolution. They occur when the mass of a celestial body grows due to the gravitational attraction of matter to it from the surrounding space. Astronomers usually classify such events as EX Lup (also known as EXors) and FU Ori (or FUors). Exors have several magnitudes in amplitude and last from several months to one or two years; Fuors are more extreme and rare, can have an amplitude of 5 to 6 magnitudes and last from decades to centuries.

However, so far very little is known about the propertiesflares in YSO. The number of such events, which can hardly be attributed to one of the two known classes, is growing. Therefore, the detection of new flares and their detailed study is important for a better understanding of their nature.

A team of astronomers led by Lynn A. Hillenbrand of the California Institute of Technology (Caltech) reportsabout the detection of another YSO flare, designated PGIR 20dci. 

Since its discovery, the brightness of the PGIR 20dcigradually increased. The near-infrared image also showed the existence of an extended, comet-type nebula of scattered light about 14,000 AU in size.

The study, published in the Preprint Library, confirms that PGIR 20dci is associated with the star-forming region NGC 281-W, located in the spiral arm of the Perseus galaxy about 9,130 light-years awayThe study of the linear absorption spectrum of PGIR 20dci in the near-infrared region has provided important information about the nature of this YSO.

Recent Near Infrared Spectroscopyconfirms the similarity between PGIR 20dci and FU Ori sources. As a result, the object was identified as a real extreme and rare star in the early stages of evolution.

As the scientists noted in their article, further research is needed, especially at high spectral dispersion, to better understand the properties of PGIR 20dci.

Discovery rendering sequence showing an area centered on PGIR 20dci. Credit: Hillenbrand et al., 2021

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Main sequence stars, when formed, are composed primarily of hydrogen (about 91% by number of particles) and helium (about 9%).

dimensionless numerical characteristic of the brightness of an object, denoted by the letter m

Astronomical unit - historicallya unit of measurement for distances in astronomy. Initially, it was assumed to be equal to the semi-major axis of the Earth's orbit, which in astronomy is considered the average distance from the Earth to the Sun