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As one of the most anticipated ground-based telescopes ever built, the Vera Rubin Observatory in northern Chile is about to finally see its fruition. Once its wide-field camera sees first scientific light early next year, it will begin searching for telltale optical signatures of supernovae millions or even billions of light years away.
This will help theorists better understand the true nature of both dark energy (the unknown force that is accelerating the expansion of the universe) and the effects of dark matter (the unfortunately perplexing exotic matter that permeates our cosmos at every moment). . level.
Optimized to search for transient celestial phenomena, during the observatory’s estimated ten-year primary operation, its Legacy Survey of Space and Time (LSST) will also identify unusual events that totally challenge our current astrophysical understanding.
What is a transient celestial event?
In the strictest sense of the word, it is something new, David Buckley, principal investigator of SALT transient phenomena, told me at the recent ‘Cosmic Streams in the Era of Rubin’ conference in Puerto Varas, Chile. But a transient is really anything that is variable; something that has suddenly emerged that we didn’t know about before, says Buckley.
Fast blue optical transients (or FBOTs) are just one example.
Fast blue optical transients are incredibly luminous events that don’t last long, Sullivan says. They have been found in surveys and I think they have an explosive origin, she says. A typical supernova, from the explosion of a white dwarf star, might last a few weeks and be about 10 billion times brighter than the Sun, Sullivan says. But FBOTS come and go so quickly that it doesn’t give astronomers much time to study them in detail and figure out what they are, she says.
As for what they might be?
One idea is that a supernova explosion occurs within what is called circumstellar material, Sullivan says. This is material that is shed during the life of the star, but remains close to it, he says. Then, when the supernova explodes, it may encounter this ejected matter; heat it up, making it very hot and creating a very bright transient event, Sullivan says.
The hope is that LSST will find many hundreds of these FBOTs.
But the real trick to understanding what these objects are is being able to identify them in the data stream very quickly and early on, Sullivan says.
Catching red dwarfs in the act
The Rubin Observatory will also help researchers understand how stellar flares, primarily from M-type stellar red dwarfs, perhaps even affect the onset of life in our universe.
The average time scale of these red dwarf flare events is about 30 minutes and it is impossible for us to predict when they will occur, Riley Clarke, a graduate student in physics and astronomy at the University of Delaware in Newark, told me at the conference. . same Puerto Varas conference. That makes them a very challenging target for most astrophysical studies, Clarke says.
The hope is that Clarke and his colleagues can use LSST to extract enough information from the image of a single eruption event to make it useful to researchers studying the stellar physics of these stars.
The way we think we can do this is by using the refractive properties of our atmosphere, to infer the temperature of a stellar flare based on how much the star moves in the sky during that event, Clarke says. Its position in the sky depends on its color, she says.
Just like when you look at an object at the bottom of a pool and it appears distorted from its actual position, differential chromatic refraction (or DCR) is a refractive property of our atmosphere, Clarke says. The atmosphere does the same thing with starlight, so when starlight passes through our atmosphere, it depends on the spectral energy distribution of the source, she says.
If more light is emitted at shorter wavelengths, then the light appears blue, Clarke says.
During its expanded ten-year study, the LSST is expected to detect about three million red dwarf eruptions that heat the star’s surface to about 10,000 degrees Kelvin, or nearly 50 percent hotter than the surface of our own Sun. It is this sudden increase in brightness that the Rubin Observatory should detect.
Understanding the mechanics and frequency of such flare events goes beyond mere astrophysics. Many astrobiologists think that, as the most common stars in the cosmos, red dwarfs may be prime candidates for nearby terrestrial planets that could support life. If a given star is too prone to such flares, it is not likely to be a candidate for hosting habitable planets.
Could these flares trigger life on exoplanets orbiting such stars?
We don’t know for sure whether the ultraviolet energy from the flare can act as a catalyst for prebiotic life; It could simply alter the chemistry enough to start enriching chemical interactions, Riley says.
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