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[♪ INTRO]
The search for life in the universe is one of the great quests of science.
But for all the decades we’ve spent searching, astronomers still don’t really know where to look,
or what exactly they should be looking for.
After all, Earth is the only place in the cosmos that we know for certain can sustain life.
Hunting for Earth-like planets is the obvious place to start,
but they seem relatively rare in the nearby universe.
So, in a new paper published last week in The Astrophysical Journal,
researchers from the University of Cambridge proposed a new approach.
They suggested that astronomers expand their definition of habitability
to include planets that are vastly different from Earth,
but that share traits with our planet’s most extreme environments.
The researchers call these planets Hycean worlds, and they claim that including them in
the search for life could lead us to evidence of living things in a dramatically shorter time.
Hycean planets are larger and more extreme than Earth-like ones.
While Earth and similar planets have a large, solid core and a moderate temperature,
and an atmosphere of nitrogen, oxygen, and other gases,
Hycean planets don’t have any of that.
They’re closer in size to Neptune, and they trade our solid surface for one dominated by water
and surrounded by an atmosphere of hydrogen.
They also have pressures up to a thousand times higher than our pressure at sea level,
and temperatures as hot as 122 degrees Celsius.
Their atmospheres can even be nearly 80 degrees warmer than that.
These conditions might seem extreme, and sure, they’re not likely to support trees,
dogs, and other macroscopic forms of life as we know it.
But we already know that some forms of life on Earth survive similar conditions,
at hydrothermal vents in the Earth’s oceans.
These vents are places where seawater collides with magma from Earth’s mantle,
superheating it and creating chemical reactions that can sustain life far from any sunlight.
In fact, some scientists even believe that life on Earth actually started in hydrothermal vents.
And now, the study’s authors believe life could potentially
arise in similar environments on Hycean planets.
Now the advantage of looking for life on these planets is that
sub-Neptune-sized planets seem to be the most abundant in the galaxy.
With bigger, brighter atmospheres, they’ll also be easier to probe for
the chemical markers of life, called biosignatures.
The biosignatures visible in a hydrogen-rich atmosphere will be different from those visible on
more Earth-like planets, but the authors found that
several signatures should be easily detectable.
In fact, one tool capable of finding that evidence of life,
NASA’s James Webb Space Telescope, is slated for launch later this year.
So, it’s possible that our first real evidence of life in the universe is closer than we think.
It just probably won’t be calling us up to say “hello.”
While we wait for James Webb to get underway, let’s unpack a surprising,
maybe even disturbing, new discovery: It’s likely that more than a quarter of Sun-like stars
have swallowed at least one planet in their lifetime.
That’s the conclusion drawn by a new paper published this week in the journal
Nature Astronomy, and it could have serious implications
for the study of both stars and the planets that orbit them.
Now, one of the basic principles of modern astrophysics is that the composition of a star
records a snapshot of the environment where it formed.
So, basically, if two stars formed from the same cloud of gas,
they should have virtually identical chemical compositions.
Yet, as telescopes have gotten more sensitive,
astronomers have started to notice that this isn’t always the case.
Instead, they’re finding pairs of stars orbiting each other with distinctly different make-ups.
To take a closer look at this phenomenon, the authors of this new study
examined a sample of 107 pairs of binary stars with Sun-like properties.
In just that one small sample, they identified 33 pairs containing different amounts of iron.
Now, without knowing anything else, astronomers might imagine that those pairs simply formed
from clouds of gas that didn’t have their elements fully mixed.
Like, maybe one star formed out of a clump that had more or less iron than the other one.
But the authors also noticed another clue:
The stars with differing compositions came almost entirely
from the hotter end of the temperature range in their sample.
And that suggested to them that something different was going on.
See, as a planet approaches its star, the star’s gravity will tear it apart,
sprinkling those planetary guts all across its surface.
But, the cooler a star is, the more efficiently it recycles material into its interior,
where it can’t be seen from Earth.
Basically, cooler stars are better at hiding the evidence than the hotter ones,
so if stars are eating planets, you would expect to see
more evidence of that among the hotter ones.
And that’s exactly what researchers were seeing in their sample.
In fact, based on their data, the authors estimated that around a quarter, or maybe even
a third, of Sun-like stars have swallowed one or more planets in their lifetime.
A fraction that high really challenges the idea that astronomers can
uniquely tie stars to their place of birth based on their composition.
But it also brings us back to the search for life.
A star system where planets are being devoured is probably a pretty chaotic place,
which maybe isn’t the best environment for birthing life.
So, identifying these systems could help astronomers focus their limited resources
on places where living things had a better chance at avoiding a fiery plunge to their death.
And with a challenge as important and difficult as finding life in the universe,
we could use all the help we can get.
And finding alien life can be quite a challenge,
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including making sure you eat your breakfast before looking for life on other planets!
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Which also helps us, so thank you.
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