As a Sun-like star nears the end of its life, it expands from 100 to 1,000 times its original size, eventually engulfing the planets that make up its system. The fate, which will inevitably overtake Earth one day, was first witnessed by astronomers in a wide international study.
By studying countless stars, at different stages of evolution, researchers have accumulated knowledge about the life cycle and how they interact with planetary systems as they age.
It is estimated that such ultimate events as this one occur only a few times a year in the entire Milky Way, the galaxy we belong to. While previous observations have confirmed the consequences for planets of the end of a star, astronomers have not witnessed the phenomenon – until now.
Astronomers watched the expansion of an end-of-life star engulf one of the planets in its system using the Gemini South telescope in Chile. Evidence revealing the phenomenon was detected by the team from a “long low energy” explosion from a star in the Milky Way about 13,000 light-years from Earth.
For astronomers at the National Research Laboratory in Optical Infrared Astronomy (NOIRLab), the event is an omen of the final fate of Mercury, Venus and Earth when our Sun begins to die in about five billion years.
“These observations provide a new perspective for finding and studying billions of stars in our Milky Way that have already consumed their planets,” says Ryan Lau, NOIRLab astronomer and co-author of the study, published in the journal Nature, in a statement.
For most of its life, a Sun-like star fuses hydrogen into helium in its hot, dense core, which allows the star to withstand the crushing weight of its outer layers. When the hydrogen in the core runs out, the star begins fusing helium into carbon, and the hydrogen fusion migrates to the outer layers of the star, causing them to expand and transforming the Sun-like star into a red giant.
However, the impacts of this transformation jeopardize the existence of the planets that make up the star’s inner system. When its surface eventually expands to envelop one of its planets, their interaction would trigger a huge explosion of energy and material. This whole process affects the speed of the planet’s orbit, the end of which is a last “dive” into the star.
The first hints of this event were uncovered by optical imaging from a public-private partnership project called the Zwicky Transient Facility. The confirmation came from analysis of the infrared coverage of NASA’s Wide Field Infrared Research Explorer (Neowise), capable of investigating environments in search of explosions and other transitory events.
“Our team’s custom reanalysis of NeoWise’s full-sky infrared maps exemplifies the vast discovery potential of archival research datasets,” NOIRLab astronomer Aaron Meisner, another co-author of the paper, said in a statement.
Distinguishing a planetary absorption burst from other types, such as solar flare events and mass ejections, is difficult and requires high-resolution observations to pinpoint the event’s location and long-term measurements of its brightness without “contamination” from nearby stars. The researchers explain that the data was obtained due to the high-tech optical resources of the Gemini South telescope.
“Gemini South continues to expand our understanding of the Universe and these new observations support predictions for the future of our own planet,” said Martin Still, program director at the Gemini Observatory. “This discovery is a wonderful example of the feats we can accomplish when we combine world-class telescope operations and cutting-edge scientific collaboration.”
The explosion that led to the absorption of the planet lasted approximately 100 days. Features like the light curve and ejected material have given astronomers a look at the mass of the star and its “devoured” planet. The ejected material consisted of about 33 Earth masses of hydrogen and about 0.33 Earth masses of dust.
From that analysis, the team estimated that the star is about 0.8 to 1.5 times the mass of our Sun and the “swallowed” planet was 1 to 10 times the mass of Jupiter.
Source: CNN Brasil
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