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Pluto's Neighborhood

Pluto shares its part of the solar system with more than 1500 other icy worlds that we know about and countless ones that have, so far, evaded our detection. The shapes of their orbits are clues to a tumultuous history that hinges on the motion of Neptune.

Neptune formed in a location much closer to the Sun than it is now, but migrated outward from the Sun over time. As it moved, it herded and scattered the objects in the Kuiper belt. Neptune trapped some of them -- like Pluto, Orcus, Haumea, and Makemake -- in orbital resonances, locked in motion synchronized to the giant planet's. Others -- like Eris and 2007 OR10 -- it scattered to extremely elliptical or highly inclined orbits. Others, it tossed inward into the solar system, to bombard the other planets or to orbit among them as Trojans, centaurs, or irregular moons. And one -- Triton -- it captured as its own moon.  There is a belt of objects so far unaffected by Neptune's motion -- like Quaoar -- called the cold classical belt. Finally, there is Sedna, whose orbit is so distant from Neptune's that it may represent the first-discovered member of a wholly unexplored part of the solar system.

Eris, Orcus, Haumea, Makemake, 2007 OR10, Quaoar, Sedna, and Triton are the largest worlds in Pluto's neighborhood, and the little that we have learned to far about their surfaces proves that each is unique. More than a hundred others are probably large enough to be called "dwarf planets." And there may yet be even larger, Mars or even Earth-sized worlds beyond these, awaiting discovery.

There is only one mission that has ever been launched to study Pluto: New Horizons.

Recent Blog Articles About Pluto and Its Neighbors

Where are the big Kuiper belt objects?

Posted by Emily Lakdawalla on 2012/02/16 05:35 CST | 8 comments

Earlier today I wrote a post about how to calculate the position of a body in space from its orbital elements. I'm trying to get a big-picture view of what's going on in trans-Neptunian space.

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When will New Horizons have better views of Pluto than Hubble does?

Posted by Emily Lakdawalla on 2013/02/18 04:22 CST | 7 comments

Last week, I posted an explainer on why Hubble's images of galaxies show so much more detail than its images of Pluto. Then I set you all a homework problem: when will New Horizons be able to see Pluto better than Hubble does? Here's the answer.

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Visiting the San Diego SpaceUp Unconference

Posted by Mat Kaplan on 2012/02/14 08:38 CST

Emily Lakdawalla and I drove down to the 3rd annual San Diego SpaceUp Unconference on February 4. We had great fun hanging out with the other space geeks.

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The scale of our solar system

Posted by Emily Lakdawalla on 2011/05/02 11:26 CDT

Space.com has taken advantage of the infinitely scrollable nature of Web pages to produce a really cool infographic on the scales of orbital distances in the solar system.

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The most exciting citizen science project ever (to me, anyway)

Posted by Emily Lakdawalla on 2011/06/21 08:23 CDT

A guest blogger here recently rounded up the large number of participatory research projects that are collectively known as citizen science. I think these are all very cool and I encourage you to check them out but none of them has yet inspired me to spend my precious time as grunt labor on a gigantic collective project. Until now.

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The Discovery of a Planet, Part 6: From Pluto to Sedna

Posted by Amir Alexander on 2005/02/17 11:00 CST

74 years after Clyde Tombaugh discovered Pluto as a faint dot on a pair of photographic plates, a modern group of astronomers made another remarkable discovery. On March 15, 2004, Michael Brown of Caltech, Chad Trujillo of the Gemini Observatory, and David Rabinowitz of Yale announced the discovery of Sedna – the furthest object ever detected in the Solar System.

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The Discovery of a Planet, Part 5: The Aftermath

Posted by Amir Alexander on 2005/02/16 11:00 CST

The discovery of Planet X was announced to the world on March 13, 1930, which marked the anniversary of William Herschel’s discovery of Uranus in 1781 as well as Percival Lowell’s birthday. The observatory’s communiqué emphasized that the discovery was no coincidence, but the vindication of Lowell’s predictions made years before.

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The Discovery of a Planet, Part 4: Clyde's Search

Posted by Amir Alexander on 2005/02/15 11:00 CST

Since his teenage years Clyde Tombaugh had been an avid amateur astronomer and a gifted telescope builder. Based on instructions contained in an article from a boy’s Sunday school paper, he built a series of telescopes of increasing power and quality on the family farm.

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The Discovery of a Planet, Part 3: Planet X

Posted by Amir Alexander on 2005/02/14 11:00 CST

The discovery of Neptune accounted for nearly all the unexplained motions of the outer planets of the Solar System. Nevertheless, several astronomers insisted that some unexplained residual motions remained, pointing to the presence of a ninth planet beyond the orbit of Neptune.

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The Discovery of a Planet, Part 2: Out of the Six-Planet World

Posted by Amir Alexander on 2005/02/13 11:00 CST

Since humans first set their eyes to the stars, they noticed that a few of these bright objects behaved differently from the others. Whereas all the stars moved together, revolving around the Earth once every 24 hours, five appeared to move within the firmament among the other stars. Accordingly, they were named “planets,” meaning “wanderers” in Greek.

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The Discovery of a Planet, Part 1: The Blinking Image

Posted by Amir Alexander on 2005/02/12 11:00 CST

February 18, 1930, was a cloudy day at the Lowell Observatory, on top of Mars Hill in Flagstaff, Arizona. 22 year old Clyde Tombaugh was hard at work, peering through the lens of an ancient-looking brass-colored device. The instrument, known as a “blink comparator,” mounted two large photographic plates.

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Ted Stryk: Report from New Horizons science team meeting

Posted by Ted Stryk on 2010/01/19 07:55 CST

The New Horizons science team is meeting this week. Ted Stryk was invited to attend the meeting, and he sent the following notes from the first day.

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Ted Stryk: Report #2 from New Horizons science team meeting

Posted by Ted Stryk on 2010/01/20 06:33 CST

Second report by Ted Stryk from New Horizons science team meeting. Major topic was the search for Kuiper belt object (KBO) targets.

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Take My Free Online College Introduction to Planetary Science and Astronomy CSUDH Class

Posted by Bruce Betts on 2014/02/05 05:02 CST | 7 comments

Our own Dr. Bruce Betts is once again teaching his Introduction to Planetary Science and Astronomy college course online. Come join him.

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South of the Border

Posted by Meg Schwamb on 2011/05/25 08:30 CDT

The last decade has seen an explosion in our understanding of the solar system with the discovery of the largest Kuiper belt objects (KBOs) of comparable size to Pluto.

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Snow balls in space

Posted by Mike Brown on 2013/12/29 02:45 CST | 4 comments

I don’t get much snow in southern California, but I do spend a lot of my time thinking about college snowball experiences and about the snowball fights that have made the objects of the outer solar system.

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Salacia: As big as Ceres, but much farther away

Posted by Emily Lakdawalla on 2012/06/26 12:27 CDT | 10 comments

A newly published paper shows trans-Neptunian object Salacia to be unexpectedly large; it's somewhere around the tenth largest known thing beyond Neptune. It has a companion one-third its size, making it appear similar to Orcus and Vanth.

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Remembering the Pluto Campaign: A Success Story

Posted by Casey Dreier on 2013/07/22 02:11 CDT | 3 comments

The New Horizons mission to Pluto survived many near-death encounters with cancellation during its development. The Planetary Society worked the whole time to ensure it would launch.

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Predicting Pluto's moons and moondust

Posted by Emily Lakdawalla on 2014/02/19 01:39 CST | 2 comments

Why didn't we discover Pluto's moons until more than a decade after Hubble launched? Mark Showalter helps me answer this question.

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Postcards from Pluto

Posted by Amanda Zangari on 2014/03/12 03:26 CDT | 2 comments

Amanda Zangari shares what it's like to be a scientist on New Horizons, and explains some of the day-to-day workings of the mission behind the scenes.

Read More »

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