Help Shape the Future of Space Exploration

Join The Planetary Society Now  arrow.png

Join our eNewsletter for updates & action alerts

    Please leave this field empty

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

Zooming in to Pluto and Charon

Posted by Emily Lakdawalla on 2015/07/12 07:31 CDT | 9 comments

In the span of a few days, Pluto and Charon have turned from spots into worlds. The latest images from New Horizons are showing Pluto and Charon to have unique faces, distinct from any other icy worlds in the solar system.

Read More »

Yet another active world: Charon

Posted by Emily Lakdawalla on 2007/07/18 05:14 CDT

I've just posted a news story on a recently published paper that suggests that Pluto's moon Charon may have active ice volcanoes.

Read More »

Year of the 'Dwarves': Ceres and Pluto Get Their Due

Posted by Paul Schenk on 2015/01/15 12:18 CST | 1 comment

This year we achieve the first exploration of these curious but fascinating objects. Paul Schenk explains what we may learn about them.

Read More »

With New Horizons Ready to Wake Up, Scientists Prepare for Pluto Encounter

Posted by Jason Davis on 2014/11/14 03:08 CST | 2 comments

When New Horizons wakes up for the final time on Dec. 6, scientists will spend six weeks preparing for the start of the spacecraft's Pluto encounter.

Read More »

Will we find signs of tectonics on Pluto? And what would that mean?

Posted by Joseph O'Rourke on 2014/05/26 09:45 CDT | 1 comment

Joseph O’Rourke summarizes a recently submitted paper on tectonic activity on Pluto after the Charon-forming impact.

Read More »

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.

Read More »

When will we know which is bigger, Pluto or Eris?

Posted by Emily Lakdawalla on 2014/04/30 12:11 CDT | 7 comments

We don't currently know whether Pluto is the biggest thing in the Kuiper belt or not. When will New Horizons give us the answer?

Read More »

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

Posted by Emily Lakdawalla on 2013/02/18 04:22 CST | 8 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.

Read More »

What to expect when you're expecting a flyby: Planning your July around New Horizons' Pluto Pictures (version 2)

Posted by Emily Lakdawalla on 2015/06/24 07:57 CDT | 22 comments

Three months ago, I posted an article explaining what to expect during the flyby. This is a revised version of the same post, with some errors corrected, the expected sizes of Nix and Hydra updated, and times of press briefings added.

Read More »

What to expect when you're expecting a flyby: Planning your July around New Horizons' Pluto pictures

Posted by Emily Lakdawalla on 2015/03/10 07:06 CDT | 18 comments

As New Horizons approaches Pluto, when will the images get good? In this explainer, I tell you what images will be coming down from Pluto, when. Mark your calendars!

Read More »

What in the world(s) are tholins?

Posted by Sarah Hörst on 2015/07/22 07:00 CDT | 9 comments

The question “why is Pluto red” has been answered with a word that most people have never heard of and perhaps even fewer people can actually define—“tholins”.

Read More »

What Color Does the Internet Think Pluto Is?

Posted by Alex Parker on 2015/04/20 03:08 CDT | 2 comments

Astronomers have known for a long time that Pluto’s surface is reddish, so where did the common idea that Pluto is blue come from?

Read More »

Welcome to the Solar System, Makemake

Posted by Emily Lakdawalla on 2008/07/15 09:45 CDT

The trans-Neptunian object formerly known as 2005 FY9 now has a name: "Makemake."

Read More »

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.

Read More »

Two Months from Pluto!

Posted by Paul Schenk on 2015/05/19 06:12 CDT | 5 comments

Two months. Eight and half weeks. 58 days. It's a concept almost too difficult to grasp: we are on Pluto's doorstep.

Read More »

Twinkling worlds in motion: New Horizons' first optical navigation images of Pluto and Charon

Posted by Emily Lakdawalla on 2014/08/07 02:31 CDT | 15 comments

What's that in the distance? A binary star? Those are two little round worlds dancing in circles, whirling around a point in space located between the two of them. It's Pluto and Charon, clearly separated by New Horizons' camera.

Read More »

Three space fan visualizations of New Horizons' Pluto-Charon flyby

Posted by Emily Lakdawalla on 2015/08/25 01:42 CDT | 4 comments

It has been a difficult wait for new New Horizons images, but the wait is almost over; Alan Stern announced at today's Outer Planets Advisory Group meeting that image downlink will resume September 5. In the meantime, a few space fans are making the most of the small amount of data that has been returned to date.

Read More »

This is the post where you can comment about the IAU planet definition

Posted by Emily Lakdawalla on 2014/04/30 12:09 CDT | 23 comments

An attempt to corral the discussion of the IAU planet definition in one place on, so that we may be free to actually discuss Kuiper belt observations and scientific results on posts elsewhere on this site.

Read More »

The scale of our solar system

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

Read More »

The not-planets

Posted by Emily Lakdawalla on 2015/07/14 12:48 CDT | 37 comments

Now that I have a reasonable-resolution global color view of Pluto, I can drop it into one of my trademark scale image montages, to show you how it fits in with the rest of the similar-sized worlds in the solar system: the major moons and the biggest asteroids.

Read More »

Facebook Twitter Email RSS AddThis


Advocate for Space!

Fifteen years ago, Society members and passionate space advocates like you helped save the Pluto mission. Now we can do the same for missions to Europa and Mars.

Join over 27,600 people who have completed their petition and consider a donation to support advocacy efforts.

Sign Our Petition


Our Curiosity Knows No Bounds!

Become a member of The Planetary Society and together we will create the future of space exploration.

Join Us

Fly to an Asteroid!

Send your name and message on Hayabusa-2.

Send your name

Selfies to Space!

Take flight with a selfie on LightSail™ in 2016!

Send a Selfie Now

Connect With Us

Facebook! Twitter! Google+ and more…
Continue the conversation with our online community!