Ascertaining distances for supernovae that struck the Earth 3 million and 7 million years ago

A study, published on the preprint server arXiv, examines how Earth was impacted by supernova explosions (plural form of supernova (SN)) that occurred 3 million years ago (Mya) and 7 million years ago for the purpose of determining the distance about the origin of these explosions.

Using the living (non-decaying) radioactive isotope 60Fe, produced in supernovae, a team of researchers at the University of Illinois was able to determine the approximate astronomical distance of the explosions that they called the Pliocene supernova (SN Plio, 3 Mya) and the Miocene supernova (SN Mio, 7 Mya).

“Supernovae are spectacular examples of the fact that stars have life cycles,” Dr. Brian Fields, professor of astronomy at the University of Illinois and co-author of the study, told Universe Today . “Supernova explosions mark the spectacular deaths of the most massive stars, those with at least eight times the mass of the sun. They play a central role in astrophysics and cosmology for many reasons. »

For this study, the researchers performed laboratory analyzes of the live (non-decaying) radioactive iron isotope 60Fe, building on several previous studies, in Meanwhile, 60Fe samples were taken from the earth’s crust, deep-sea sediments, and lunar regolith. Although the ages of these samples were determined based on 60Fe’s half-life of 2.62 million years and were determined to come from two supernova explosions, the goal of this recent study was to determine distance to the two explosions.

Research results indicate that SN Plio appeared between 20 and 140 parsecs (pc), or between 65 and 457 light years (ly), from Earth, but within vi is most likely from 50 to 65 pc, or 163 to 212 cups.For SN Mio, the team determined the approximate distance to be 110 pc, or 359 ly. For context, 1 pc is 3.26 cups. Although these distances may be considered relatively “safe” compared to Earth, how could such explosions affect the development of our solar system?

“If a supernova explodes too close to Earth or another Earth-like planet, the consequences could be devastating for life,” Dr John said. Fields told Universe Today.

“Supernova explosions produce high-energy radiation – gamma rays – which will irradiate Earth’s atmosphere for months after the explosion. Our atmosphere will protect us from direct exposure to these gamma rays, but at a cost: the upper layer of ozone. The atmosphere will decrease significantly, leaving Earth vulnerable to ultraviolet (UV) rays from the sun, which could harm most life on Earth. It will take the Earth several years to regenerate the ozone layer“. supernovae are among the most dramatic sights observed in the universe, with the oldest supernova on record, now named RCW 86 or SN 185, occurring on December 7 185 AD and recorded by Chinese astronomers. They call this event a “guest star”. ” and noted that its light remained in the sky until June 186 AD before disappearing.Astronomers now consider the event to be a transient astronomical event and attribute RCW 86, located approximately 2,800 parsecs (pc) (9,100 light-years (ly)) from Earth with an estimated diameter of 85 mm, likely a type A supernova.

Dr. Fields explained to Universe Today: “Supernova explosions are rare: there are about one to three such events every century across the galaxy ours, the Milky Way. Therefore, most of them explode far away and are harmless to Earthlings. over a period of millions of years, it is very likely that one of them will explode close to Earth, even too close for comfort.”

Dr. Fields noted that although the mass extinction that occurred at the end of the Devonian period about 360 million years ago was the result of one or more supernovae, he told Universe Today that there are currently “no candidates threatening supernovae”, since “none are near their destruction zones.” .

One of the most famous (future) supernovae is the star Betelgeuse, a supernova red is located about 550 ly from Earth and is the second brightest star in the universe. Orion constellation Betelgeuse made headlines in late 2019 when astronomers observed the star dimming, some think it’s about to go supernova.

However, follow-up observations suggested in August 2020 that the dimming was due to a dust cloud that formed from superhot material ejected by the massive star, which was later confirmed in an August 2022 study. While Betelgeuse is known for its brightness variances due changes in its temperature and size, some might still ask when it’s going to explode?

Dr. Fields tells Universe Today, “It is unknown when [Betelgeuse] will explode, because as far as we know, the late phases of a massive star’s life do not cause noticeable changes in the surface region of the star. Thus, Betelgeuse could be the next supernova in our galaxy, but it could also explode 100,000 years from now. But its eventual death is certain, so enjoy it in Orion now while you still can.”