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The Most Distant Dwarf Planet Yet

Back in the days when Clyde Tombaugh was using a blink comparator to search for ‘Planet X,’ finding a new object in the outer Solar System was highly unusual. Uranus had been found in 1781, Neptune in 1846, and I suppose I should add Ceres in 1801, although it’s a good deal closer than the other two. The real point is that the Solar System seemed straightforward in Clyde Tombaugh’s day. There were eight planets and an asteroid belt. It wouldn’t be until 1943 that Kenneth Edgeworth argued that the outer system might have ‘a very large number of comparatively small bodies,’ with Gerard Kuiper publishing his own speculations in 1951.

Estonian astronomer Ernst Öpik first described what we now know as the Oort Cloud in 1932, with Jan Oort, a Dutch astronomer, reviving the idea in 1950. The Oort Cloud was a way to explain why comets behave the way they do. Oort believed that there must be a cometary ‘reservoir’ far away from the Sun — he chose 20,000 AU as a likely range because of the number of long period comets with aphelia at approximately that distance. Moreover, long-period comets seemed to come from all directions of the sky. As we’ve refined the idea and the numbers, we’ve begun to see just how vast the Solar System really is.

None of this is to take anything away from the discovery of the small world called V774104, announced yesterday at the Division for Planetary Sciences meeting in Washington, DC. Astronomer Scott Sheppard (Carnegie Institution for Science) and Chad Trujillo (Gemini Observatory, HI) have found a world 15.4 billion kilometers out, which works out to 103 AU and makes V774104 the most distant dwarf planet known, fully three times further from the Sun than Pluto. In Tombaugh’s day, such a discovery would have been front page news. Today we’ve come to assume that there are a lot of dwarf worlds out there, and expectations are that as our equipment improves, we’ll find plenty more.

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Image: A dot moving (slowly) across background stars, V774104 was found about 15 degrees off the ecliptic. Credit: Subaru Telescope by Scott Sheppard, Chad Trujillo, and David Tholen.

V774104 is currently estimated to be between 500 and 1000 kilometers in diameter, less than half Pluto’s size. Just how significant it is in the larger scheme of things has yet to be determined because we’re not yet sure about the parameters of its orbit. Is it, at 103 AU, close to aphelion, and will it eventually swing back toward Neptune, making its orbit the likely result of a gravitational encounter with that planet? Or is V774104 actually something far more unusual, a world similar to Sedna and VP113 in being a possible member of the inner Oort Cloud?

Neither Sedna nor VP113 comes close enough to the Sun to experience gravitational effects from the giant planets. In fact, both stay outside 50 AU, thought to be the outer edge of the Kuiper Belt, and have aphelia as distant as 1000 AU. Colin at the Armagh Planetarium site notes the problem in V774104: Could a Dark World Put a New Light on Solar System History?:

…the current highly elliptical orbits of Sednoids cannot be their original orbits, the chance of smaller bodies in such eccentric paths accreting into objects hundreds of kilometres across is fantastically low. Sednoids must have originally formed in relatively circular orbits, possibly in the Oort Cloud.

So how did they get where they are today? One possibility to explain their orbits is that they reflect conditions in the Solar System’s infancy, when the young Sun was in a local environment rich in nearby stars. The other possibility is one that Percival Lowell would have loved. There may be a large, rocky planet out there that has elongated previously circular orbits.

The data from the 8-meter Subaru instrument in Hawaii that produced V774104 have also yielded a number of other objects roughly 80 to 90 AU from the Sun, all of which will need lengthy follow-up study to clarify the nature of their orbits. Like V774104, any of these might join Sedna and VP113 in never coming closer to the Sun than 50 AU. We may be about to see a surge in the numbers of dwarf worlds in this unusual category. Explaining why a region once thought to be empty is not should occupy astronomers and theorists for years to come.

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  • Al Jackson November 12, 2015, 11:39

    I would be curious to know how Öpik predicted the ‘Oort Cloud’.
    Oort did it by using the comet catalog. Oort noticed all the Long Period Comets had an isotropic distribution in the sky and suggested they come from a spherical reservoir a long ways out.
    Not sure how Öpik arrived at the idea.
    Öpik reminds me of Fritz Zwicky, a cantankerous scientist with an uncanny intuition. Zwicky was a piece of work!

  • RobFlores November 12, 2015, 13:13

    Does astrobiology, posit any slow chemistry life forms that might
    arise near the cores of these cold dwarf planets? Would the pressure of
    gravity be enough to keep the central of such a body liquid.? Would
    most of the heavier ‘metals’ and therefor nutrients sink towards the
    center too?
    I think it is safe to say that the number of Icy dwarf worlds is much
    larger than the warmer terrestrial planets in most stellar systems. Going by our local example perhaps by as much as 4 to 5 times as numerous.
    Since there is nothing to prevent terrestrials from seeding other
    terrestrials with life. Something similar might spread the cold weather
    life forms in a similar manner.

  • Joseph Langford November 12, 2015, 21:09

    Rob, there are many things that prevent terrestrials seeding other terrestrials. These include terrestrial gravity, gravity from the star, heat from the impact, radiation from the star, heat from re-entry & impact, climate/atmosphere/chemistry of the impacted planet. I have no problem with life forming on Mars or the Moons of Jupiter/Saturn and being transferred to Earth, but not the other way.

  • ljk November 13, 2015, 10:02
  • Michael November 13, 2015, 15:18

    There must be somewhere out there small icy bodies that are around 550 Au from the Sun so we could take advantage of the solar focus lensing effect. If we had them and could place them to observe the galactic central black hole in the photon spectrum and if we used the water, purified, the neutrino spectrum we could learn an enormous amount about black holes. We could learn much about the beginning of time and look into the end of time in a small region.

  • Adam November 13, 2015, 17:22

    Michael,
    The neutrino gravitational focus distance is somewhere near the orbit of Uranus. Thus we don’t need to head into the Oort to visit it.

  • Adam November 13, 2015, 17:28

    Al Jackson,
    Many of Öpik’s op-eds in the Irish Journal of Astronomy are available through the NASA ADS and he comes across as quite the contrarian. For example, he dismissed the greenhouse effect as the cause of Venus’s hot surface conditions, instead contending that it was due to all the dust in the atmosphere (the cause of the clouds in his opinion.)

  • Michael November 13, 2015, 21:45

    @Adam November 13, 2015 at 17:22

    ‘Michael,
    The neutrino gravitational focus distance is somewhere near the orbit of Uranus. Thus we don’t need to head into the Oort to visit it.’

    The neutrino focus of the Suns core is around 3.5 billion km just past Uranus

    http://www.sciencedirect.com/science/article/pii/0375960188905713

    I wanted to use the 550 Au focus point as we can then use the gamma and x-ray spectrum coupled with neutrinos to give greater detail of the event horizon. Perhaps two systems would be better engineering wise but ideally both together at the same spot would be better.

  • Adam November 14, 2015, 4:22

    Hi Michael

    A more recent reference: Insights on neutrino lensing …which computes it as ~20 AU.

    One rather fascinating possibility is that binary systems, with one object a powerful neutrino source, can produce a neutrino “lighthouse beam” thanks to the focusing by the companion. A slightly more terrifying version has the companion explode as a supernove, producing a neutrino “death beam”.

  • Michael November 15, 2015, 7:17

    @Adam

    ‘One rather fascinating possibility is that binary systems, with one object a powerful neutrino source, can produce a neutrino “lighthouse beam” thanks to the focusing by the companion. A slightly more terrifying version has the companion explode as a supernove, producing a neutrino “death beam”.’

    Even though an enormous number of neutrinos will be focused they are very unlikely to interact with matter, the cross section is very,very small! Now due to their very low chance of interactions nothing stops a black hole forming with these neutrinos IF the focus point is small enough and we can get ENOUGH in region quickly enough, if you like a Kugelblitz or Geon but with neutrinos.

  • ljk November 16, 2015, 9:23

    A review of a book on the small worlds of our celestial neighborhood:

    http://www.universetoday.com/123396/book-review-dawn-of-small-worlds/

  • david lewis November 16, 2015, 14:37

    I’ve often wondered what it would be like to turn such an object into a star ship. With tens of millions of cubic kilometers to dig into, and with which to establish an infrastructure, it could support a population of tens to hundreds of billions.

    Getting it up to speed, even 1/1000th that of light, would take some doing, but it would essentially be a planet onto it self, and could survive a multi-thousand year journey. Close approaches with other systems could be used as a gravitational boost so getting to another star would be quicker with each one it visited.

    It wouldn’t stop in each system, but would rather study it in depth, and leave behind colonists.

  • ljk November 18, 2015, 9:45

    david lewis said on November 16, 2015 at 14:37:

    “I’ve often wondered what it would be like to turn such an object into a star ship. With tens of millions of cubic kilometers to dig into, and with which to establish an infrastructure, it could support a population of tens to hundreds of billions.”

    The first people to make such a Worldship and launch it into the void will be some super rich man or woman (or a group of them) wanting to avoid paying terrestrial taxes or being apprehended for some other crime. They might also be the head of a cult who want their “religious freedom”. They could also be some other form of religious or politically oppressed group wanting to escape terrestrial oppression. And just as with Europeans aiming for the New World, others may just want to start a new life and find new fortunes beyond the confines of the Sol system.

    Noble astronauts on a scientific expedition to another star system will not be motivation enough for someone or some organization to shell out the very large amount of funds and resources required to turn a planetoid or comet into a multigenerational starship. Just look at Project Apollo.

    Using a planetoid or comet as a starship is smart in any event, as you not only will have resources to take from but they will also serve as good radiation and debris shields. Just remember to keep reminding the crew they are on a ship in space, that this is not the entire Universe. Windows, people, windows!

  • Hop David November 18, 2015, 10:07

    I was hoping WISE would find some large outer system bodies capable of tossing long period comets to the inner solar system. Reflected sunlight isn’t much help in searching for low albedo and/or distant objects. I would like to see more orbital infrared scopes.

    David Lewis might be correct that a dwarf planet KBOs or Oort object could sustain a population of many billions. IF we develop non-stellar fusion power. If this comes to pass, what would be our incentive for interstellar travel?

    Humanity repeatedly bumps against our logistic growth ceiling. Time and time again as we settle one frontier after another. Opening the outer system frontier would give us plenty of room to grow for many thousands of years.

    There are likely many Oort objects just barely within Sol’s Hill Sphere. So some outer Oort colonies would drift into interstellar space. But drifting away from Sol doesn’t get us to another star system. Most of our neighboring stars are moving anywhere from tens to hundreds of kilometers/second with regard to our sun.