Outer Solar System Not as Crowded as Astronomers Thought

October 3, 2008

(PhysOrg.com) -- When a treasure hunt comes up empty-handed, the hunters are understandably disappointed. But when astronomers don't find what they are looking for, the defeat can provide as much information as a successful search.

The search in question, the Taiwanese-American Occultation Survey (TAOS), spent two years periodically photographing portions of the sky to look for small chunks of rock and ice orbiting beyond Neptune, in a region of the solar system called the Kuiper Belt. The survey targeted Kuiper Belt objects (KBOs) with sizes between 2 miles (3 km) and 17 miles (28 km).

Since such objects are too small to see directly, the survey watched for stars to dim as KBOs passed in front of and occulted them. After accumulating more than 200 hours of data watching for stellar flickers lasting a second or less, TAOS did not spot any occultations.

The Kuiper Belt contains objects in a range of sizes: a few very large ones (like the dwarf planets Pluto, Eris, Makemake and Haumea) and many more smaller ones. The commonness of a given size tells us information about the history of planet formation and dynamics. In particular, the size distribution of KBOs reflects a history of agglomeration, in which colliding objects tended to stick together, followed by destructive collisions, where collisional velocities were high enough to shatter the rocks involved.

Astronomers questioned whether they would find more and more objects as sizes decreased further, or whether the distribution leveled out. The fact that no occultations were seen sets a stringent upper limit on the number density of KBOs between 2 and 17 miles in diameter. The outer solar system hence appears not as crowded as some theories suggest, perhaps because small KBOs have already stuck together to form larger bodies or frequent collisions have ground down small KBOs into even smaller bits below the threshold of the survey.

The paper announcing this result, co-authored by CfA director Charles Alcock, was published in the October 1 issue of the Astrophysical Journal Letters. The full list of co-authors is available from ApJL.

For more information, see:

taos.asiaa.sinica.edu.tw/
www.astro.ncu.edu.tw/contents/research/taos/shot6_fix-1.wmv

Provided by Harvard-Smithsonian Center for Astrophysics

Explore further: What is the Kuiper Belt?

Related Stories

What is the Kuiper Belt?

June 17, 2015

Dr. Mike Brown is a professor of planetary astronomy at Caltech. He's best known as the man who killed Pluto, thanks to his team's discovery of Eris and other Kuiper Belt Objects. We asked him to help us explain this unusual ...

NASA's New Horizons spacecraft closing in on Pluto

January 19, 2015

The mysterious, distant and yet unexplored by any probe world of Pluto and its moons, located on the edge of our solar system, is about to get visited. NASA's New Horizons spacecraft on July 14 will perform the first ever ...

Hubble to proceed with full search for New Horizons targets

July 2, 2014

(Phys.org) —NASA's Hubble Space Telescope has been given the go-ahead to conduct an intensive search for a suitable outer solar system object that the New Horizons (NH) spacecraft could visit after the probe streaks though ...

Hubble seeks follow-up target for New Horizons after Pluto

June 18, 2014

It's going to be a really busy summer for the New Horizons team. While they're checking out the newly awakened spacecraft to make sure it's working properly for its close encounter with Pluto next year, NASA is already thinking ...

Recommended for you

Image: Hubble sees a youthful cluster

August 31, 2015

Shown here in a new image taken with the Advanced Camera for Surveys (ACS) on board the NASA/ESA Hubble Space Telescope is the globular cluster NGC 1783. This is one of the biggest globular clusters in the Large Magellanic ...

4 comments

Adjust slider to filter visible comments by rank

Display comments: newest first

superhuman
5 / 5 (2) Oct 03, 2008
This is good news!
The less of them up there the lower the chance of one of them paying us a visit.
Adam
5 / 5 (1) Oct 03, 2008
Perhaps something is eating the smaller objects?
DoctorKnowledge
5 / 5 (1) Oct 03, 2008
I think we need a $700 billion bailout for the Kuiper Belt.
Velanarris
5 / 5 (1) Oct 04, 2008
Man made solar system warming has led us to believe that human CO2 emissions have melted KBOs leaving us with the lowest KBO set on record since we began measuring last year.

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.