Located about 1,360 light-years from the solar system, FU Orionis, also called FU Ori, is a variable star that mysteriously became 1,000 times brighter 88 years ago. Astrophysicists have been trying to figure out why for a long time, especially for more than a decade, using ALMA's network of radio telescopes. The hypothesis that was once proposed has gained more weight.
Press release from National Radio Astronomy Observatory doordoor On the work done withAtacama Large Millimeter/Submillimeter Array (Alma) from ESO which was published in an article by Astrophysical Journal. It is about observations that confirm a hypothesis put forward to solve an 80-year-old mystery related to a star in the Milky Way capable of producing the equivalent of solar flares, but a thousand billion times more powerful than in the case of the Sun.
It all started in 1936 when the star FU Orionis was located in Orion constellationinside nebulanebula Dark Bernard 35 (A cloudsclouds Molecular cold and dust) suddenly increased brightnessbrightness Hundreds of times, making it pass in less than 200 days Clear sizeClear size From 16.5 to 9.6. in the beginning, Astronomy scientistsAstronomy scientists They thought they were witnessing some kind of nova, but a more in-depth study of the phenomenon, especially with spectroscopic signatures, showed that this was not the case.
to'Atacama Large Millimeter/Submillimeter Array (abbreviated ALMA) FU Orionis was first observed in 2012, during the first science operations. Even with her initiation ability, Alma was able to confirm that FU Orionis was in fact a binary system. © Sebastian Pérez
Fu ori double protostar?
For decades, FU Orionis remained a unique case, but in 1970 a similar star was discovered – V1057 Cygni. We now know that ten stars showed the same behavior and were grouped into a new class of starsVariable starsVariable stars The FU type is called Orionis. FUors, as they are called, are now well known to amateur variable star astronomers who are members of the famous American Society of Variable Star Observers (in English, American Association of Variable Star Observers (AAVSO).).
We also now know that FU Orionis is actually a Binary systemBinary system Young stars and in particular the star responsible for its individual behavior is actually a protostar of the type Te TauriTe Tauri Not yet famous Main sequenceMain sequenceThat is, he draws it energyenergy Of processAccumulationAccumulation Gravitational contraction is still ongoing and not ignition of hydrogen fusion reactions according to the proton-proton chain or CNO cycle. In fact, all FUors seem to be associated with this type of young star.
The current model for understanding sudden changes in luminosity of FUors was mainly developed by AstrophysicistsAstrophysicists United State Lee Hartman And Scott Jay Kenyon He links the eruption of FU Orionis to a transfer MassMass suddenly Accumulation diskAccumulation disk Towards a young, low-mass T Tauri star. But that still needs to be proven.
A cumulative stream betrayed by carbon monoxide emissions
In the press release for National Radio Astronomy Observatory, Antonio Halesdeputy director of the ALMA North America Regional Center and lead author of the article published inAstrophysical Journal, Today he explains that ” Devour Fu Ori ThemeTheme For nearly 100 years to maintain its eruption. We've finally found an answer to how these bright young stars replenish their mass. For the first time we have direct observational evidence of explosions feeding material “.
Alma's observations actually revealed a long, thin stream of… Carbon MonoxideCarbon Monoxide Carbon dioxide falls on FU Orionis. However, this flow of matter does not appear to contain enough to explain the brightness of FU Ori, but according to Hales: “ It is possible to interact with the flow GasGas Larger in the past made the system unstable and led to increased brightness.
By understanding how these FU stars are made, we confirm what we know about how different stars and planets form. We believe that all stars undergo explosions. These explosions are important because they affect the chemical composition of the accretion disks around budding stars and the planets they eventually form. We've been studying FU Orionis since the first observations of Alma in 2012. It's great to finally have answers “.
