Uranus and Planet Nine: Exploring Two Planets for the Price of One

~ J.S. Pailly

Hello, friends!

I don’t like to go out shopping.  My time is valuable.  Traffic is frustrating.  Fuel is expensive.  So if I do need to go out for some reason, I plan my route carefully and try to combine multiple errands into one trip.  Believe it or not, this is a lifeskill that I learned from NASA.  When NASA plans missions into outer space, they too plan carefully and try to double, triple, or quadruple up science objectives for a single mission.

In April of 2022, the U.S. National Academy of Sciences advised NASA to send a mission to the planet Uranus, with a launch date in the early 2030’s.  This mission has not been officially approved yet, nor has it officially been named.  As a placeholder name, it’s often called the Uranus Orbiter and Probe mission, or U.O.P.  As this placeholder name implies, the mission would include two spacecraft: an orbiter, to orbit Uranus, and a probe, which would be dropped into the atmosphere to probe Uranus’s interior.

No spacecraft from Earth has visited Uranus since the 1980’s, so a mission like this is long overdue.  The orbiter will spend four to five years orbiting the planet, studying the planet’s rings, measuring the planet’s weird and wonky magnetic field, and visiting all of the planet’s major moons—several of which may contain subsurface oceans of liquid water.  Oh, and if NASA does launch in the early 2030’s, U.O.P. should arrive in time to observe the changing of seasons on Uranus (something which only happens once ever 42 years).

As for the atmospheric probe, it will spend maybe an hour or so plummeting through the planet’s atmosphere before being crushed by the increasing atmospheric pressure.  Right now, scientists can only make educated guesses about Uranus’s interior structure and chemical composition.  The uppermost layer of the Uranian atmosphere is an opaque haze of hydrocarbons.  Neither ground-based nor space-based telescopes can see through that haze, so an atmospheric probe is the only way to find out what the deeper layers of Uranus’s atmosphere are really like.

But as I said at the beginning of this post, NASA likes to double, triple, and quadruple up science objectives whenever they can, and I just read about a really interesting and exciting side quest U.O.P. may be able to complete while on route to Uranus.  For about a decade now, scientists have suspected that we might have nine planets in our Solar System after all.

According to the Planet Nine hypothesis, something very massive—massive enough to be a large planet or, perhaps, a small black hole—is lurking in the outer reaches of the Solar System, somewhere far beyond the orbit of Neptune.  You see, the orbits of many of trans-Neptunian objects (comets, dwarf planets, etc.) seem to be clustered together in a rather peculiar way.  It’s almost as if a very big, very massive something has been pushing all those trans-Neptunian objects around, corralling them together with the power of its gravity.

As of yet, no one has been able to pinpoint the exact location of the mysterious Planet Nine.  But U.O.P. may be able to help!  Remember that Uranus is very, very far away.  The flight from Earth to Uranus will take a very, very long time.  During that long journey through space, U.O.P. will feel the gravitational influence of all the planets in the Solar System—including the gravitational influence of any planets we don’t currently know about.  So by keeping close tabs on U.O.P.’s exact location in space, astronomers should be able to notice any unexpected gravitational forces that may start tugging on U.O.P.

Even a slight gravitational tug should, over the course of the long journey to Uranus, be enough to point us in the direction of Planet Nine, or at least help us zero in on Planet Nine’s most probable location.

WANT TO LEARN MORE?

Here’s a write-up from the Planetary Society about NASA’s most recent “decadal survey” for planetary science, which includes (among other recommendations) the proposed Uranus Orbiter and Probe Mission.

And here’s the research paper I read pitching the idea of using U.O.P. to help search for Planet Nine.

And lastly, here’s an article from Inverse explaining the above mentioned research paper in layperson’s terms.

22 thoughts on “Uranus and Planet Nine: Exploring Two Planets for the Price of One”

      1. No worries! WordPress has been weird for a while now, I think. It’s made me slightly paranoid whenever I comment, double and triple checking to make sure I’m actually signed in.

        From what I read, it sounds like Ariel is the most likely ocean world out there, due to tidal forces. Oberon and Titania might also have oceans inside, but they’d have to be really salty oceans. But Ariel (as I understand it) may be getting enough heat from tidal forces to stay liquid inside with only a minimal amount of saltiness.

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  2. I heard about the proposal and my first thought was “finally, a mission to Uranus is seriously overdue!” I thought it would be nice to also collect data on Neptune while they’re there, but turns out Neptune’s not in a great place for that. Planet Nine could be a good side-mission though!

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    1. I really had my fingers crossed for a Neptune mission. I thought getting a closer look at Triton might make the longer travel time worth it. But I’m still glad we’re getting a mission to Uranus. There’s plenty of weird stuff we need to figure out there as well.

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    1. If it is a black hole, at least it’s in a stable orbit well away from us. Could be a hazard for space adventurers leaving the Solar System one day, though.

      As for the atmosphere, I was surprised about that too. I think it’s not just the density but the chemical composition that makes it so hard to see through it. It sounds a bit like the hydrocarbon haze surrounding Titan, except on Titan the haze is orange and on Uranus its blue.

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  4. The UOP / Planet Nine idea is interesting. But I wonder if data from past missions could be used this way. Probably not the Voyagers with their old 1970s / 80s telemetry, but maybe New Horizon’s data? Or is it just not precise enough?

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    1. I was wondering the same thing, but apparently somebody already tried that using data from Cassini, Juno, and some Mars orbiters. I’m not sure if New Horizons was included. I thought it was, but just now when I went back and double checked, the paper didn’t actually say that it was.

      Anyway, yeah, it sounds like the data we have isn’t precise enough. The paper I read is basically advocating for taking more precise and more frequent measurements of U.O.P.’s trajectory, once it clears the orbit of Jupiter.

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  5. could it even be a disappearing black hole? I watched the other day a programme speaking of black holes forming when a star implodes…? Then following that line of thought, would eventually these black holes also gradually disappear… ?

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    1. Black holes do gradually disappear. That’s one of the discoveries that made Stephen Hawking famous. But the process takes hundreds of billions of years, so if Planet Nine is actually a black hole, it’s not going to disappear anytime soon.

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      1. of course not and the probe you were talking about will not have a wasted journey in this respect. What I wanted to say is that by ‘disappearing’ – it is not getting stronger in that to pose a threat to us…, as some of the other people commenting mentioned…. if I read it right…

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      2. Oh no, it’s not getting stronger, or closer, or anything like that. In the distant future, spacecraft entering or leaving the Solar System would want to steer clear of it, but otherwise it’s not a threat.

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