Even stars have salad days.
And researchers under NASA's leadership have spotted a nearby star that looks a lot like our sun when it was young, opening a rare window into how the early sun shaped the atmosphere of Earth and gave rise to life as we know it.
While this could also help us learn what to look for while seeking life on alien worlds, there's more: It could potentially help us decide which nascent worlds beyond the solar system humans may eventually settle.
A Sun-like star is a window into our solar system's salad days
On a long enough lifeline, everyone eventually dreams of meeting a younger version of themselves (although not always for the same reason). You could imagine giving them advice to face the challenges to come, discover when new traits of personality quirks came into being, and workshop what your shared future should look like. Scientists have done the same for the sun, which, at 4.65 billion years old, is already halfway through its life. Much like with a human double, scientists have wondered what properties enabled our sun to give rise to life on Earth in the former's salady days.
Lacking a time machine to jump us back billions of years, it seemed an impossible dream to study the early sun in this way. But the Milky Way galaxy that houses it is vast, and the spiral arm in which we live contains more than 100 billion stars. So many that one in ten is distinctly similar to ours, and a lot of them are still in the early stages of solar development. "Imagine I want to reproduce a baby picture of an adult when they were one or two years old, and all of their pictures were erased or lost," said Senior Astrophysicist Vladimir Airapetian of the Heliophysics Division at NASA's Greenbelt, Maryland-based Goddard Space Flight Center, who is also first author of the recent study, in a Phys.org report. "I would look at a photo of them now, and their close relatives' photos from around that age, and from there, reconstruct their baby photos."
A 'twin' star to our sun is roughly the age the latter was when life developed on Earth
"That's the sort of process we are following here — looking at characteristics of a young star similar to ours, to better understand what our own star was like in its youth, and what allowed it to foster life on one of its nearby planets," added Airapetian, in the report. The star he's following is Kappa 1 Ceti, and it's only 30 light-years away, which is fairly close. The stellar neighbor is roughly 600 to 750 million years old, and is roughly the same age as our sun, back when life first arose on Earth. It's even close to the sun's mass and surface temperature, according to Meng Jin, second author of the study who is also a heliophysicist of the SETI Institute and Lockheed Martin Solar and Astrophysics Laboratory in California.
Presenting us with these key factors of the sun, Kappa 1 Ceti is an ideal "twin" of the sun when its third-orbiting planet, Earth, was beginning to support life for the first time. Jin, Airapetian, and numerous other colleagues have already adapted an existing solar model to project future behavior of Kappa 1 Ceti, in addition to its most obtuse characteristics. They relied on data gathered from several disparate space missions, like NASA's Transiting Exoplanet Survery Satellite, the NASA/ESA Hubble Space Telescope, the ESA's XMM-Newton, and the NICER missions.
Stellar winds can catalyze life on Earth-like planets
The most near-term hope of the researchers is to study the way young sun-like stars like Kappa 1 Ceti release stellar winds, which are colossal waves of superhot gas called plasma are spewn out into the solar system. Plasma is what happens when particles of a gas are split into negatively charged electrons and positively charged ions. The most energy-intensive one can reach the outermost and hottest regions of the star's atmosphere: The corona. And, in an eruption, the stream of plasma can fling out towar nearby planets, "influencing their environments" as stellar wind, explained Jin.
Younger stars have hotter, more aggressive stellar winds, and heavy outbursts can drastically affect the chemistry and atmosphere of nearby planets, potentially transforming or catalyzing the development of organic material, which brings life. This is still preliminary, but with more information on sun-like stars of much younger ages, scientists can more accurately predict what kinds of planetary systems we should pay attention to in the search for life beyond our solar system, in addition to better grasping how it began within.