An article published in the journal “Monthly Notices of the Royal Astronomical Society” reports the detection of a powerful stellar flare generated by the young star cataloged as NGTS J121939.5-355557 or more simply as NGTS J1219-3555. A team of astronomers used the Next-Generation Transit Survey (NGTS) telescope array in Chile to observe a rare event that could be important for exoplanet formation in a system that is still in formation.
About 685 light years from Earth, the star NGTS J121939.5-355557 is a bit smaller than the Sun and has an estimated age of about 2 million years. This means that it’s so young that it hasn’t yet completed its formation and that’s why it is defined as pre-main sequence since it hasn’t yet entered its life’s main phase, which will probably last several billion years. In this situation, even a small star can have very violent flares, really explosive phenomena that follow its magnetic field’s rearrenging and the result is what in jargon is called a coronal mass ejection accompanied by strong electromagnetic radiation.
James Jackman, PhD student at the British University of Warwick, used the NGTS in a project to search for explosive phenomena in stars other than the Sun. This array was designed to look for exoplanets but the observations of hundreds of thousands of stars can also be useful for other purposes, such as the one that led to this discovery.
The data used for this research were detected between November 28, 2015 and August 4, 2016. The star NGTS J121939.5-355557’s flare was detected on January 31, 2016. For several hours the star became up to seven times brighter than normal. For the analysis of these observations, data from other sources were also used, such as ESA’s Gaia space probe’s Data Release 2 (DR2) published in April 2018.
Solar flares are not much if compared with the one coming from the star NGTS J121939.5-355557 so this research allowed to gather new information on extreme flares. One of the interesting characteristics that were detected is in multimode quasi-periodic pulsations, structures consisting of oscillation of flare intensity that are common in solar flares but relatively rare in the studied stars.
Understanding stellar flares will provide a better understanding of the solar ones but in the case of a newborn star surrounded by a protoplanetary disk such a violent phenomenon could have an important influence on the birth of new planets. In particular, the X rays emitted in the flare can influence the formation of “chondrules”, melted grains with calcium-aluminum-rich dust, present in that type of disk. They coalesce into asteroids that eventually form the planets.
The problem is to understand whether a flare of such violence can be beneficial for planetary formation or disrupting. The observation of such a young star, which still has no formed planets, could help provide answers even if that process lasts for millions of years. Professor Peter Wheatley, James Jackman’s Phd supervisor and among the authors of the research, stressed the fact that this type of activity should be taken into account by astronomers in the study of planet formation. He also mentioned ultraviolet radiation, needed for some chemical reactions at the base of the birth of life forms.
The researchers stressed the importance of a wide-range research to study these phenomena, even if the most common flares are far less violent than that came from the star NGTS J121939.5-355557. Understanding their mechanisms could, among other things, help find star systems where there are more chances that rocky planets host life forms.
