The Sun had sisters
when it was born, according to new research, hundreds to thousands of them.
And at least one was a supernova, providing further
support for the idea that there could be lots of planets around other stars since our solar system emerged in such
an explosive
environment.
"We know that the majority of stars in our galaxy were born in star
clusters," said Leslie Looney, who arrived at the solar sibling finding
along with his colleagues at the University of Illinois at Urbana-Champaign.
"Now we also know that the newborn solar system not only arose in such a
cluster, but also survived the impact of an exploding star. This suggests that
planetary systems are impressively rugged and may be common in even the most
tumultuous stellar nurseries."
The evidence for the solar sisters was found in
daughters--such as decayed particles from radioactive isotopes of iron--trapped
in meteorites, which can be studied as fossil remnants of the early solar
system.
These daughter species allowed Looney and his colleagues to
discern that a supernova with the mass of about 20 suns exploded relatively
near the early Sun when it formed 4.6 billion years ago; and where there are
supernovas or any massive star, you also see hundreds to thousands of sun-like
stars, he said.
The cluster of thousands of stars dispersed billions of
years ago due to a lack of gravitational pull, Looney said, leaving the sisters
"lost in space" and our Sun looking like an only child ever since, he
said.
The research will be detailed in the Astrophysical
Journal.
The finding also has exciting implications for life in other
solar systems, Looney said, since most stars are born in clusters.
"If our favorite planet, Earth, was born in the nasty environment
of a cluster, with the increased radiation and gravitational effects, then the
majority of stars could also have planets," Looney told SPACE.com.
"Not only have planets, but have planets where terrestrial life can
occur."
Astronomers now should focus more attention on how planets
form in clusters, he said. "It may be easier to form planets than we
expected," he said.
Isotopes and supernovas
When massive stars explode and go
supernova, they create radioactive isotopes that are blown outward and mix
with nebular gas and dust as they
condense into stars and planets. In the case of our solar system, that means
some of the isotopes were trapped in the rocks that hardened to form the early
solar system. Meteorites are remnants of those rocks, so they contain the
radioactive offspring, or daughter species, of the isotopes created by the
supernova.
Looney and his colleagues used measured abundances of the
daughter species to calculate that the supernova sibling was about 0.32 to 5.22
light-years from the Sun. The closest star system to the Sun today is Alpha
Centauri at 4.36 light-years.
"The supernova was stunningly close," said
Looney's co-author Brian Fields. "Our solar system was still in the
process of forming when the supernova occurred."
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