Author Topic: Dwarf planet discovery hints at a hidden Super Earth in solar system  (Read 175278 times)

Offline Star One

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https://twitter.com/Tom_Ruen/status/994638035915563008?s=20

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Replying to @dAArkEnergy and @theDESurvey
#2015BP519 has an amazingly inclined orbit, and heading north with perihelion in 2058 at 35AU. It may be large enough (~400–700 km) to qualify as a dwarf planet!
(link: http://web.gps.caltech.edu/~mbrown/dps.html) web.gps.caltech.edu/~mbrown/dps.ht…
Likely: Anything icy larger than 500 km is highly likely to be round.
« Last Edit: 05/11/2018 07:21 AM by Star One »

Offline Archibald

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So what is general consensus as of today ? I've heard of a Mars- or Earth size planet, and a Neptune-size planet farther away. Also, there might be a lot of pluto-sized planet.
...you have been found guilty by the elders of the forum of a (imaginary) vendetta against Saint Elon - BLAAASPHEMER !

Offline Bynaus

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The consensus is that the search is going on and that all these putative worlds are just that until they have been found.
More thoughts: www.final-frontier.ch (in German)

Offline 192

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So what is general consensus as of today ? I've heard of a Mars- or Earth size planet, and a Neptune-size planet farther away. Also, there might be a lot of pluto-sized planet.

Planet Nine is hypothesised to be between 5 and 15 Earth Masses. If you're interested in more detail I'd suggest checking out http://www.findplanetnine.com/.

If you're interested in Dwarf Planets in the outer Solar System, http://web.gps.caltech.edu/~mbrown/dps.html#table has a nice table of the known dwarf planets and most likely candidates discovered so far.

Offline Star One

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A New World’s Extraordinary Orbit Points to Planet Nine

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Astronomers argue that there’s an undiscovered giant planet far beyond the orbit of Neptune. A newly discovered rocky body has added evidence to the circumstantial case for it.

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What’s more, Batygin and Brown also predicted that over time, Planet Nine’s gravity would push these Kuiper belt objects out of their current plane and into ever-higher orbital inclinations. Although astronomers have already spotted a bizarre population of worlds that orbit the sun perpendicularly to the plane of the solar system, they had never caught an object transitioning between the two populations. “There’s no real way to put something on an orbit like that — except that it’s exactly what we predicted from Planet Nine,” Brown said. Batygin notes that the new object fits so perfectly with their model that it almost looks like one of the data points in their simulations. “A good theory reproduces data — but a great theory predicts new data,” he said.

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“There is no other reasonable way to populate the Kuiper belt with such highly inclined bodies,” Batygin said. “I think the case for the existence of Planet Nine is now genuinely excellent.”

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Other astronomers aren’t so certain — in part because the early solar system remains a mystery. Scientists suspect that the sun was born within a cluster of stars, meaning that the early planets might have had many close encounters with other stars that sent them on paths that seem impossible today. And even once the stars dispersed, the early solar system likely contained tens of thousands of dwarf planets that could have provided the gravitational nudges needed to push 2015 BP519, as the new object is called, into such an odd orbit. “To me, Planet Nine is one of a number of ways that the solar system could have unfolded,” said Michele Bannister, an astronomer at Queen’s University Belfast who was not involved in the study. “It’s a potential idea.” But at the moment it is just that — an idea.

https://www.quantamagazine.org/a-new-worlds-extraordinary-orbit-points-to-planet-nine-20180515/

Offline jebbo

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There's been some discussion on twitter that the orbit of 2015 BP519 is explicable using Neptune alone ...

--- Tony

Offline Star One

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There's been some discussion on twitter that the orbit of 2015 BP519 is explicable using Neptune alone ...

--- Tony

It’s more accurate to state that’s it is hard but not impossible for Neptune to have created this object alone, but it is towards the ‘edge’ of Neptune’s influence.
« Last Edit: 05/17/2018 06:38 AM by Star One »

Online hop

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It’s more accurate to state that’s it is hard but not impossible for Neptune to have created this object alone, but it is towards the ‘edge’ of Neptune’s influence.
The paper looked at Neptune's current orbit, but doesn't examine migration in the early solar system. They do mention it as a possible alternative (along with stellar encounters), but don't analyze the probabilities:
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Although it is unclear how an object with a semi-major axis as high as that of 2015 BP519 would be generated in this process, we cannot exclude the idea that 2015 BP519's currently observed orbital inclination may come from a period of violent instability in the early history of the solar system.
This is totally reasonable, one paper can't cover everything. However, it does leave significant room for non-P9 explanations. Some of the twitter discussion suggests previous simulations of migration do put things in this kind of orbit.
« Last Edit: 05/17/2018 05:49 PM by hop »

Offline Star One

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It’s more accurate to state that’s it is hard but not impossible for Neptune to have created this object alone, but it is towards the ‘edge’ of Neptune’s influence.
The paper looked at Neptune's current orbit, but doesn't examine migration in the early solar system. They do mention it as a possible alternative (along with stellar encounters), but don't analyze the probabilities:
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Although it is unclear how an object with a semi-major axis as high as that of 2015 BP519 would be generated in this process, we cannot exclude the idea that 2015 BP519's currently observed orbital inclination may come from a period of violent instability in the early history of the solar system.
This is totally reasonable, one paper can't cover everything. However, it does leave significant room for non-P9 explanations. Some of the twitter discussion suggests previous simulations of migration do put things in this kind of orbit.

Some of the Twitter discussions I saw around this topic would have been more constructive if certain participants hadn’t worn their pro & anti P9 biases so clearly on their sleeves.

Isn’t it just better to say the origin of this object at the present time is ambiguous.
« Last Edit: 05/17/2018 07:36 PM by Star One »

Offline Star One

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On the detectability of Planet X with LSST

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Two planetary mass objects in the far outer Solar System --- collectively referred to here as Planet X --- have recently been hypothesized to explain the orbital distribution of distant Kuiper Belt Objects. Neither planet is thought to be exceptionally faint, but the sky locations of these putative planets are poorly constrained. Therefore, a wide area survey is needed to detect these possible planets. The Large Synoptic Survey Telescope (LSST) will carry out an unbiased, large area (around 18,000 deg2), deep (limiting magnitude of individual frames of 24.5) survey (the "wide-fast-deep" survey) of the southern sky beginning in 2022, and is therefore an important tool to search for these hypothesized planets. Here we explore the effectiveness of LSST as a search platform for these possible planets. Assuming the current baseline cadence (which includes the wide-fast-deep survey plus additional coverage) we estimate that LSST will confidently detect or rule out the existence of Planet X in 61\% of the entire sky. At orbital distances up to ∼75 au, Planet X could simply be found in the normal nightly moving object processing; at larger distances, it will require custom data processing. We also discuss the implications of a non-detection of Planet X in LSST data.

https://arxiv.org/abs/1804.07713

Online hop

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On the detectability of Planet X with LSST
Previously posted and discussed up-thread https://forum.nasaspaceflight.com/index.php?topic=34329.msg1813564#msg1813564

Not complaining, just pointing back to earlier discussion. These papers tend to come around once when they are first posted and hit the media after they are published.

Offline Torbjorn Larsson, OM

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Unless an existing P9 is really faint, the LSST should come online too late to be of interest if I have understood Brown and Batygin correctly. They referenced a maximum 5 year seek time, that covered most of the parameter space with current resources, two years ago.

It’s more accurate to state that’s it is hard but not impossible for Neptune to have created this object alone, but it is towards the ‘edge’ of Neptune’s influence.
The paper looked at Neptune's current orbit, but doesn't examine migration in the early solar system. They do mention it as a possible alternative (along with stellar encounters), but don't analyze the probabilities:
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Although it is unclear how an object with a semi-major axis as high as that of 2015 BP519 would be generated in this process, we cannot exclude the idea that 2015 BP519's currently observed orbital inclination may come from a period of violent instability in the early history of the solar system.
This is totally reasonable, one paper can't cover everything. However, it does leave significant room for non-P9 explanations. Some of the twitter discussion suggests previous simulations of migration do put things in this kind of orbit.

Some of the Twitter discussions I saw around this topic would have been more constructive if certain participants hadn’t worn their pro & anti P9 biases so clearly on their sleeves.

Isn’t it just better to say the origin of this object at the present time is ambiguous.

I think people can have constructive discussions despite being biased, as long as the bias is based on the available evidence. (But of course I am biased to think that.)

There is not much of an ambiguity theory wise. If P9 has migrated during "a period of violent instability in the early history of the solar system", which is likely, that event is passed when 2015 BP519 is constrained by P9. So you lose a lot of predictions in one swoop, making P9 the preferred model in some likelihood ratio test. (That should be quantified to be valid and not argumentative of course, but it looks iffy of you aren't a modeler and have lots of time on your hand.)

Speaking of predictions, the excitement does not come from adding an ad hoc hypothesis to the rest, but as I understand it Batygin has pressed that it is the first unexpected prediction that passed a test ('not only a good theory, but a great theory').

Offline Star One

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On the detectability of Planet X with LSST
Previously posted and discussed up-thread https://forum.nasaspaceflight.com/index.php?topic=34329.msg1813564#msg1813564

Not complaining, just pointing back to earlier discussion. These papers tend to come around once when they are first posted and hit the media after they are published.

Apologies I didn’t notice the date on the paper.
« Last Edit: 06/02/2018 07:04 AM by Star One »

Offline Star One

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Collective gravity, not Planet Nine, may explain the orbits of 'detached objects'

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Bumper car-like interactions at the edges of our solar system—and not a mysterious ninth planet—may explain the the dynamics of strange bodies called “detached objects,” according to a new study.

CU Boulder Assistant Professor Ann-Marie Madigan and a team of researchers have offered up a new theory for the existence of planetary oddities like Sedna—an icy minor planet that circles the sun at a distance of nearly 8 billion miles. Scientists have struggled to explain why Sedna and a handful of other bodies at that distance look separated from the rest of the solar system.

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The findings may provide clues around another phenomenon: the extinction of the dinosaurs. As space debris interacts in the outer solar system, the orbits of these objects tighten and widen in a repeating cycle. This cycle could wind up shooting comets toward the inner solar system—including in the direction of Earth—on a predictable timescale.

“While we’re not able to say that this pattern killed the dinosaurs,” Fleisig said, “it’s tantalizing.”

https://www.colorado.edu/today/2018/06/04/collective-gravity

Offline Star One

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Looks like Mike Brown is closing in on the elusive planet nine. He can’t directly observe it he goes onto say as it is not yet up in the sky.

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New Planet Nine paper just submitted to a scientific journal. When do you get to see it? First, it goes to a scientific editor who sends it out for peer review. Finding someone to do timely peer review the month of August is never easy, but with luck we might get review ...

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back in a month. We then respond to reviewers comments and, depending on how critical the comments were, it might go back to the reviewers. So best case is that maybe it is accepted for publication mid-September. Worst is, I don't know, December? It can be a long process ...

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but, with luck, it will lead to a paper even better than the one originally submitted.

Sometimes people post papers before they have been through review, but, in most cases, I prefer to wait until after review. But then it will be posted for all to see....

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I'll give the teaser though: the paper is super cool. It helps us both confirm that Planet Nine is almost certainly out there, and it helps us to pinpoint the orbital path of Planet Nine, so we will know where to look this fall. Stay tuned!

https://mobile.twitter.com/plutokiller/status/1024323434107437056
« Last Edit: 08/03/2018 08:14 PM by Star One »

Offline CuddlyRocket

The Influence of Planet 9 on the Orbits of Distant TNOs: The Case for a Low Perihelion Planet (arXiv)

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(Abstract)
The hypothesis of an additional planet in the outer Solar System has gained new support as a result of the confinement noted in the angular orbital elements of distant trans-Neptunian objects. Orbital parameters proposed for the external perturber suggest semimajor axes between 500 and 1000 au, perihelion distances between 200 and 400 au for masses between 10 and 20 M⊕. In this paper we study the possibility that lower perihelion distances for the additional planet can lead to angular confinements as observed in the population of objects with semimajor axes greater than 250 au and perihelion distances higher than 40 au. We performed numerical integrations of a set of particles subjected to the influence of the known planets and the putative perturber during the age of the Solar System and compared our outputs with the observed population through a statistical analysis. Our investigations showed that lower perihelion distances from the outer planet usually lead to more substantial confinements than higher ones, while retaining the Classical Kuiper Belt as well as the ratio of the number of detached with perihelion distances higher than 42 au to scattering objects in the range of semimajor axes from 100 au to 200 au.
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(Conclusions)
... we concluded that planets with perihelion distances as small as 90 au should not be discarded in principle. They produce better confinements while preserving the Classical Kuiper Belt and the ratio between the number of detached to scattering objects in the region 100 au < a < 200 au.

Offline Star One

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Discovery and Dynamical Analysis of an Extreme Trans-Neptunian Object with a High Orbital Inclination


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We report the discovery and dynamical analysis of 2015 BP519, an extreme Trans-Neptunian Object detected detected by the Dark Energy Survey at a heliocentric distance of 55 AU and absolute magnitude Hr= 4.3. The current orbit, determined from a 1110-day observational arc, has semi-major axis a≈ 450 AU, eccentricity e≈ 0.92 and inclination i≈ 54 degrees. With these orbital elements, 2015 BP519 is the most extreme TNO discovered to date, as quantified by the reduced Kozai action, which is is a conserved quantity at fixed semi-major axis a for axisymmetric perturbations. We discuss the orbital stability and evolution of this object in the context of the known Solar System, and find that 2015 BP519 displays rich dynamical behavior, including rapid diffusion in semi-major axis and more constrained variations in eccentricity and inclination. We also consider the long term orbital stability and evolutionary behavior within the context of the Planet Nine Hypothesis, and find that BP519 adds to the circumstantial evidence for the existence of this proposed new member of the Solar System, as it would represent the first member of the population of high-i, ϖ-shepherded TNOs.

https://arxiv.org/abs/1805.05355

Offline Bynaus

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In an interview with Sean Carroll, Mike Brown says a few very interesting things about P9:

https://www.preposterousuniverse.com/podcast/2018/08/27/episode-11-mike-brown-on-killing-pluto-and-replacing-it-with-planet-9/

1) They now have a very good estimate for the orbit - but they don't know where along the orbit it is
2) Semimajor axis is about 500 AU, with significant eccentricity and inclination
3) The mass is about 7+-2 Earth masses
4) After accounting for all biases, he estimates that the probability of a chance alignment of the nodes of the far-flung Kuiper belt objects is about 0.1%. Which makes him 99.9% confident that P9 exists.

The new mass estimate is excitingly low... P9 might really be the first "exoplanet" (a representative of the most abundantly found type of exoplanet so far: a super-Earth/sub-Neptune), right at our door-step!

Go hear it - its quite an interesting interview anyway!
More thoughts: www.final-frontier.ch (in German)

Online Alpha_Centauri

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The shorter semi-major axis is also interesting as it may be a bit brighter at aphelion than first expected.

I’m tentative about equivalences between outer planets in our solar system and sub-Neptunes formed largely in-situ on tight orbits wind-sculpted by their star. For a start at 7 earth masses you have to think this thing must have got chucked out very early, it’s evolutionary history is likely quite different and that may be reflected in its composition. Less a gassy rockball and more a slightly rocky gasball.
« Last Edit: 08/30/2018 07:44 AM by Alpha_Centauri »

Offline Bynaus

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7 Earth masses, according to Mike Brown, fits very well with the suggested mass of the ejected "fifth gas giant".

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Less a gassy rockball and more a slightly rocky gasball.

Don't you mean the other way around? The rocky core would contribute a major portion of the total mass, with a lot of volatiles on top and only a little bit of H + He, as the planet didn't have much time to accrete these elements from the disk.
More thoughts: www.final-frontier.ch (in German)

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