Outer Solar System Not as Crowded as Astronomers Thought

Oct 03, 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/… taos/shot6_fix-1.wmv

Provided by Harvard-Smithsonian Center for Astrophysics

Explore further: Can astronomy explain the biblical Star of Bethlehem?

add to favorites email to friend print save as pdf

Related Stories

Some planet-like Kuiper belt objects don't play "nice"

Jan 17, 2014

The Kuiper belt—the region beyond the orbit of Neptune inhabited by a number of small bodies of rock and ice—hides many clues about the early days of the Solar System. According to the standard picture ...

The Kuiper Belt at 20

Sep 03, 2012

Planetary science is celebrating the 20th anniversary of the discovery of the Kuiper Belt. That came in 1992, when the first Kuiper Belt Object (KBO) was discovered.

Recommended for you

Can astronomy explain the biblical Star of Bethlehem?

22 hours ago

Bright stars top Christmas trees in Christian homes around much of the world. The faithful sing about the Star of Wonder that guided the wise men to a manger in the little town of Bethlehem, where Jesus was ...

Hubbles spies the beautiful galaxy IC 335

23 hours ago

This new NASA/ESA Hubble Space Telescope image shows the galaxy IC 335 in front of a backdrop of distant galaxies. IC 335 is part of a galaxy group containing three other galaxies, and located in the Fornax ...

Image: Multicoloured view of supernova remnant

Dec 22, 2014

Most celestial events unfold over thousands of years or more, making it impossible to follow their evolution on human timescales. Supernovas are notable exceptions, the powerful stellar explosions that make ...

Ultra-luminous X-ray sources in starburst galaxies

Dec 22, 2014

Ultra-luminous X-ray sources (ULXs) are point sources in the sky that are so bright in X-rays that each emits more radiation than a million suns emit at all wavelengths. ULXs are rare. Most galaxies (including ...

When a bright light fades

Dec 22, 2014

Astronomer Charles Telesco is primarily interested in the creation of planets and stars. So, when the University of Florida's giant telescope was pointed at a star undergoing a magnificent and explosive death, ...

User comments : 4

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.