The Gaia satellite is a mission of the European Space Agency in order to map our galaxy. To do this, Gaia completely checks the sky over and over again but, while looking at space to fix the positions of the stars, she is able to detect thousands of transient objects (that is, something in the sky that appears, disappears or changes) so that astronomers can quickly point to other ground and space telescopes to study such objects in detail , which can be phenomena such as supernova explosions and other starbursts.
In the summer of 2016, astronomers saw a star 2,500 light-years away come to life in the constellation The Swan, as if preparing to explode in a colossal supernova. However, the next day, the star regained his normality. There was no explosion. The funny thing is that, after a few weeks, the strange phenomenon happened again: the star suddenly brightened, and then dimmed. This cycle was repeated five times in 500 days. What was this glow?
“This was very unusual behavior. Almost no type of supernova or other star does this,” said Lukasz Wyrzykowski, from the University of Warsaw (Poland) and co-author of the work published in the journal Astronomy & Astrophysics .
Very strange behavior
Follow-up observations made with more than 50 telescopes around the world revealed that the source, since named Gaia16aye , was behaving quite strangely. But it wasn’t due to anything the star was doing; rather to the gravity of an invisible object that deformed the fabric of space-time, magnifying the light of the star as it passed. Experts have discovered that this invisible object is a binary star located 2,544 light years away from Earth, which is so faint that we cannot see it, as if it were invisible. However, based on the way the star’s gravity magnifies the light, astronomers have been able to calculate the mass, distance, and orbit of this pair of red dwarf stars.
“If you have a single lens, caused by a single object, there will be a small constant increase in brightness and then there will be a smooth decrease as the lens passes in front of the distant source and then moves away,” Wyrzykowski clarifies.
The star’s anomalous brightness suggested a binary object that produces what is known as a gravitational microlensing; an effect predicted by Einstein, which occurs when the gravity of a foreground object causes spacetime to bend, magnifying something behind it, something like a field of cosmic magnifying glasses. These lenses amplified the star’s light each time it passed behind them. And those stars were effectively invisible from Earth.
“We received all this data, analyzed it and managed to obtain a very accurate image of this system, which would not normally be seen,” added the expert.
Scientists have used the phenomenon of gravitational microlensing to take a closer look at some of the oldest stars, galaxies and objects in the universe, but the effect can also reveal the properties of much closer and fainter objects and even even rarer cosmic phenomena and Mysterious, like black holes, which are normally only detectable when they are spitting out nearby matter and expelling jets of gaseous light. Wyrzykowski is optimistic and believes that “this year we will have the first black holes.”
Referencia: Ł. Wyrzykowski et al. Full orbital solution for the binary system in the northern Galactic disc microlensing event Gaia16aye, Astronomy & Astrophysics (2019). DOI: 10.1051/0004-6361/201935097
