Last week, astronomers were talking about some pretty extreme planets.
So let’s start with one that sounds like it comes straight out of Greek mythology:
Like a god eating his children, there’s a star that seems to be eating a huge gas
planet that orbits it.
The star is called PTFO 8-8695, and it’s about eleven hundred light-years away from
Earth.
Its planet, PTFO 8-8695 b, was first suggested by data from a survey done back in 2012, but
astronomers needed more evidence before they could be confident that a planet was actually
there.
They were especially skeptical because the star is only about two or three million years
old – around a thousandth the age of our Sun.
Planets around such young stars are pretty rare, and when they /are/ found, they’re
usually far away from the star.
But /this/ planet is an example of a “hot Jupiter:” a gas giant orbiting very close
to its home star, that can be anywhere from the size and mass of Saturn to more than ten
times as massive as Jupiter.
This planet, for example, is probably around two times Jupiter’s mass, and seems to complete
an orbit once every /eleven hours/.
So its /year/ is half as long as our /day/.
That’s /really/ short, and it puts the planet incredibly close to its star – close enough
that PTFO 8-8695 might actually be able to steal gas from the atmosphere of the planet,
according to one group of astronomers whose study was accepted by The Astrophysical Journal
last week.
They came to this surprising conclusion after using telescopes in Texas and Arizona to study
the light emitted by the planet and the star.
When hydrogen gas is really energized, one of the wavelengths of light it can emit is
in the red visible spectrum – also called H-alpha emissions.
And the astronomers found that the H-alpha emissions from the planet’s outer atmosphere
were almost as bright as the emissions from the star itself!
Now, hot Jupiters can typically get as hot as a couple thousand Kelvin, but the hydrogen
atoms in their atmospheres shouldn’t have as much energy as the atoms in a huge nearby
star.
So, the astronomers think that the gas in the planet’s atmosphere could be interacting
with the star’s stellar wind – the stream of charged particles constantly flowing off
of its surface.
And because of this, the gas could be escaping the planet’s gravity – and get trapped
by PTFO 8-8695’s gravity and pulled to the star’s surface.
It’s possible that the /entire atmosphere/ could get stripped off like this, leaving
a sad remnant of a world.
Or maybe an equilibrium will be reached someday – only time will tell.
The astronomers admit that there are other explanations for some of their data: like,
extreme sunspots or a ring of dust around the star.
But they do think that planet-eating is the most likely cause.
And, now, let’s turn from killing planets to forming them.
Our Sun is thought to be a third-generation star – meaning that it formed from the ashes
of the stars, that formed from the ashes of the first stars, that coalesced after the
Big Bang created the universe.
By the time the Sun was born, there were lots of heavier elements in the cosmos – elements
like aluminum and silicon and iron, which make up a lot of the Earth’s crust.
But in a lot of second-generation stars, there weren’t as many of these heavier elements,
since they’re made in the cores of dying stars, and only one generation of stars had
come and gone.
Some of these stars without many heavy elements are called carbon-enhanced metal-poor, or
CEMP, stars.
As their names suggest, CEMP stars also have a pretty high percentage of carbon.
And last week, a pair of researchers at Harvard showed for the first time that planets /can/
and probably /did/ form around these CEMP stars – and these could’ve been some of
the /first/ planets to form in the universe.
Because of all the carbon around, these planets would’ve been like gigantic lumps of graphite
or diamond, depending on the conditions when they formed.
There are still some CEMP stars around the Milky Way that we can study, so we can look
for these carbon-rich, elusive remnants of the very early universe.
And here’s the thing: interspersed with all that carbon in CEMP stars are elements
like oxygen and hydrogen.
And /those/ elements are also some of the most important elements for all life on Earth.
So that raises the exciting possibility that these planets might not have /just/ been the
first planets in the universe, but they could’ve been the first places in the entire universe
where life formed.
Now all we have to do is find some to study.
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