Hello Space Fans and welcome to another edition of Space Fan News.
In this episode the story this week comes from my alma mater, the University of Colorado
at Boulder with a story that has many good and interesting things about it: it’s from
CU, there may not actually be a Planet 9 that’s causing the strange outer solar system orbits,
and the major work behind this study was done by a CU undergrad - that’s right, and undergraduate
student is shedding light on a difficult problem.
OK, most of have know for a while about the theory that what might be causing the observed
orbits of these strange objects in the outer solar system called ‘detached objects’.
The orbits were so strange that normal planetary motions and theories of solar system formation
could not explain why they orbited the Sun the way they did.
So, astronomers Konstanin Batygin and Mike Brown proposed, after trying to rule out every
other possible explanation, proposed that maybe there is an as yet unseen planet affecting
the orbital dynamics of these bodies.
This idea made a lot of sense, we found the planet Neptune this way, we saw the effects
this planet had on the other planets, namely Uranus, in our solar system and was able to
figure out that there must be a planet there and sure enough, after lots of observing and
looking for it, Neptune was found in 1846.
So doing the same kind of math, Batygin and Brown determined that if the orbits observed
by these strange objects, among them the minor planet known as Sedna, then the planet must
be really far out, around 800 astronomical units or so, be really big, about 2-4 times
the radius of Earth and about 10 times more massive, and orbit the Sun once every 10 to
20 thousand years or so.
OK, so this was a big news and everybody has been trying to find it ever since.
And no one has found it yet.
As I said, Batygin and Brown (whom I’ve had in hangouts before) have said that they
knew this claim would require extraordinary evidence so they worked really hard to eliminate
every other possible explanation before saying this might be due to a planet.
Well they didn’t work hard enough because last week at the summer meeting of the American
Astronomical Society, the CU Boulder team announced another possibility.
The collective gravity of all the strange little objects floating around past the orbit
of Neptune, when you add them all up, could explain the strange orbits seen by Sedna and
the other objects plotted by astronomers.
The outer solar system is a really strange place gravitationally, there a lots of orbits
of lots of things that when you plot them accurately, don’t make any sense.
Sedna for example, a little smaller than Pluto, takes 11 thousand years to go around the Sun
once.
It’s orbit is also circle-shaped and doesn’t go anywhere near big planets like Jupiter
of Neptune.
So, how did Sedna get there?
It remains a mystery and hence the name: detached objects, the closest they ever get to the
Sun is so far away that they aren’t affected by the gravity of the larger planets, the
appear detached from the solar system.
So the outer solar system has lots of things circling the Sun in really strange orbits
that can’t easily be explained, not even with another planet out there.
But if you add up all the gravitational effects of all the detached objects out there, some
really interesting things happen that appear to explain these orbits.
An undergradate student working in the Dept of Planetary and Atmospheric Sciences at CU,
a place I spent way too much time in, wrote some code that calculated the orbits of of
the minor planets, such as Pluto, icy moons and a variety of space debris.
According to the simulations, the orbits of the icy objects beyond Neptune circle like
the hands of a clock, in a very Copernican way.
Some of those orbits, like asteroids moved faster and in tandem, flying in formation.
Other objects, big ones like Sedna, move much more slowly.
So what happens when the fast ones, overtake the slow ones?
It’s a very interesting gravitational problem, one that hasn’t been really considered before.
When this happens, the smaller objects begin to pile up on one side of the sun.
These orbits crash into some of the bigger bodies causing a minor planet like Sedna,
which once had a normal, ellipsoidal orbit, into a detached, circular one.
This simulation was confirmed by predicting another strange thing about detached objects,
the bigger a detached object is, the further away its orbit becomes from the sun.
Another interesting idea that came out of this: as space debris interacts in the outer
solar system, their orbits tighten up and widen in a repeating way.
This cycle could have the effect of altering comet orbits towards the inner solar system
including the Earth, on a predictable timescale.
So let this story be an example to all of you looking for a career in science.
Many people ask if you need a PhD to do astronomy and the answer is a resound NO!
It may come to pass that we will ultimately find Planet 9, but given how hard everyone
is looking, it really should have been found by now, it was not hypothesized to be a small
thing after all.
This research provides another explanation for observations and I’d love to hear what
Batygin and Brown have to say, but they haven’t responded to my emails yet.
I’m sure they are quite busy now but I will try to keep you posted.
That’s it for this episode Space Fans, if you’d like to be notified of all new content
posted by Deep Astronomy but don’t want to rely on YouTube’s rather inconsistent
notification system, please stop by DeepAstronomy dot space to register your email.
You’ll get notified every time we add any new content, regardless of platform, Anchor,
Facebook, twitch whatever.
I promise you email address will only be used for DeepAstronomy business and that your privacy
will always be honored.
Thanks to all Deep Astronomy Patreon patrons who also keep this and other content going.
Thanks to all of your for watching and as always, Keep Looking Up!