...is a Diamond... Planet?
55 Cancri-e was discovered in 2004,
circling a star not that far from us. It was called a “super-Earth”, because it
was rocky like the Earth and larger. Its radius is twice Earth’s, making its
mass about 8 times ours, while it speeds around its star in only 18 hours. To
do that, it has to be so close to the star’s surface that the planet’s surface
reaches temperatures around 3,900° F (2,100° C). {Just a little warmer than
Nebraska in August.}
{By the way, the ‘e’ of 55 Cancri-e
means this was the 4th planet found in orbit around this star. (The star itself
is designated A.)The other 3 reside even closer. Where does the star end and planet(s)
begin? More recently, a 5th planet - ‘f’ - has been discovered, with a year
lasting about 261 Earth days.}
If 55 Cancri-e had a planetary
chemistry similar to Earth’s, the temperature and mass might mean it was
covered with oozing ‘supercritical fluids’ (gases at such a high pressure they
would act more like liquids). So it was imagined, at one time. But further
study has revealed that it has a planetary chemistry far different.
For one thing, it apparently has no
water on it at all.
Astronomers felt 55 Cancri-e was
probably composed almost exclusively of carbon (diamond & graphite), iron,
silicon carbide and possibly silicates. More than 1/3 of its mass could be pure
diamond, which would be more than the entire Earth. Try sticking that into an
engagement ring!
However, the diamond part was
probably not just one big chunk. They thought the planet’s surface was covered
in graphite and diamond rock, rather than our familiar water and granite.
Actually, the Earth has far, far less carbon in comparison. So they tried to
figure out what that difference meant. This different planetary chemistry could
mean 55 Cancre-e could have had a very different thermal evolution than Earth
and strange plate tectonic processes, which would mean bizarre types of
volcanism, mountain formation and seismic activity.
But a new analysis indicated that 55
CancriA (the star in question) had more oxygen than previously thought. That
might mean 55 Cancri-e might not have quite as much carbon as they had thought.
Or it might mean nothing. The processes of star and planet formation are not
fully understood, but it is known that the composition of a planet does not
always match that of its parent. So the studies continued.
In 2016, observers detected
hydrogen, helium and possibly hydrogen cyanide in ‘e’s atmosphere. In 2017,
they decided there might be a global ocean... made of lava, so no skinny
dipping. And that e’s atmospheric pressure was about 1.4 bar, so a slightly
thicker atmosphere than ours.
If all this sounds familiar, well...
We visited the 55 Cancri system on or about 6Sept2017, in the 2nd episode of my
‘Weird Planets’ series of blogs. But I think I found more details this time, so
hope you enjoyed ‘catching up’.
Oh, yes, in July 2014, the
International Astronomical Union launched a process for giving ‘proper’ names
to some exoplanets and their host stars. The name selected for 55 CancriA was
Copernicus, and e was named Janssen. (Yes, all his known siblings got named,
too.)
https://www.space.com/18011-super-earth-planet-diamond-world.html
https://www.space.com/23138-diamond-planet-super-earth-discovery.html
https://en.wikipedia.org/wiki/55_Cancri_e
https://news.nationalgeographic.com/news/2012/10/121011-diamond-planet-space-solar-system-astronomy-science/
https://www.cnet.com/news/hubble-probes-atmosphere-on-diamond-planet/
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