The bizarre case of meteors with two identities

Dec 20, 2011

(PhysOrg.com) -- Astronomers have discovered why we see meteors flash through the night sky while they seemingly rain down on us gently at the same time. In a paper published in the December 20 issue of the Astrophysical Journal, models of the zodiacal cloud are reconciled with radar observations, revealing a game of hide and seek and an interesting identity switcheroo.

“This detective story was much a case of meteors you can see and those you can’t”, says lead author and planetary astronomer David Nesvorny of the Southwest Research Institute in Boulder, Colorado.

Meteors are caused by that hit the Earth’s upper atmosphere at astronomical speeds, although some hit slower than others. Out in space, those meteoroids move feverishly between the planets. They are seen as a diffuse glow of scattered sunlight in the , called the zodiacal cloud.

While zodiacal cloud models predict that meteoroids should hit Earth relatively gently, raining down the micro-meteorites that lace the Antarctic snow, of meteors consistently see the sky filled with rapidly speeding ones, too fast for anything to survive.

“How is that possible?”, asked Nesvorny and his collaborators. “To reconcile things, we improved our model to predict meteor rates and took into account how radars are able to see meteors. And things worked!”

The new model showed that radars are nearly blind to slow meteors, but pick up just the right collection of fast meteors to explain what they see in nature.

One bizarre observation remained unexplained. Radars sensitive to small 100 micron sized sporadic meteors see the same speeds and approach directions as those sensitive to meteoroids ten times as big.

“That was a conundrum”, says meteor astronomer and co-author Peter Jenniskens of the SETI Institute and NASA Ames Research Center. “Bigger particles should disappear more quickly. Instead, they seem to survive for about the same time.”

In their new paper, Nesvorny and Jenniskens explain why: Meteoroids in the zodiacal cloud are born one way, and then turn into another after shedding most of their plumage.

Meteoroids are born from comets in a fragile form, prone to rapid destruction, most likely from heating and cooling in day-night cycles. These large centimeter-sized meteoroids cause the meteor showers we see at night. “Meteoroid streams don’t seem to survive for more than a few thousand years”, says Jenniskens.

They are broken into pieces a tenth to one millimeter in size that are observed as sporadic by radar and as the diffuse zodiacal cloud in the night sky. It is those meteoroids that survive for almost 100,000 years before they are destroyed by collisions among themselves. “The radar data show that small and big ones are destroyed in this way at much the same rate”, concludes Nesvorny.

Explore further: Telescopes hint at neutrino beacon at the heart of the Milky Way

More information: Preprint on ArXiv: arxiv.org/abs/1109.2983

Related Stories

Source of zodiac glow identified

Apr 15, 2010

(PhysOrg.com) -- The eerie glow that straddles the night time zodiac in the eastern sky is no longer a mystery. First explained by Joshua Childrey in 1661 as sunlight scattered in our direction by dust particles ...

Comet collision to come?

Aug 11, 2011

New research shows that the Earth was impacted for a few hours by a stream of dust from a potentially dangerous comet on February 4, 2011.

New app helps NASA keep track of meteoroids

Dec 15, 2011

Surprising but true: Every day, on average, more than 40 tons of meteoroids strike our planet. Most are tiny specks of comet dust that disintegrate harmlessly high up in Earth's atmosphere, producing a slow ...

Geminid meteor shower 2011

Dec 07, 2011

Its the finale of this year’s meteor showers: The Geminids will start appearing on Dec. 7 and should reach peak activity around the 13th and 14th. This shower could put on a display of up to 100+ meteors ...

Exploding Lunar Eclipse

Aug 27, 2007

Most people appreciate lunar eclipses for their silent midnight beauty. NASA astronomer Bill Cooke is different: he loves the explosions.

Recommended for you

A colorful gathering of middle-aged stars

Nov 26, 2014

NGC 3532 is a bright open cluster located some 1300 light-years away in the constellation of Carina(The Keel of the ship Argo). It is informally known as the Wishing Well Cluster, as it resembles scattered ...

User comments : 1

Adjust slider to filter visible comments by rank

Display comments: newest first

kevinrtrs
1 / 5 (3) Dec 21, 2011
This article is as clear as mud - to me anyway. Maybe my English has deteriorated.
Bigger particles should disappear more quickly. Instead, they seem to survive for about the same time
Why? Not explained, but one can begin to put it together with the following:
These large centimeter-sized meteoroids cause the meteor showers we see at night. Meteoroid streams dont seem to survive for more than a few thousand years

This then begins to ask why we should be seeing them at all because they should have disappeared over the billions of years of the existence of the solar system. Since it is assumed they come from comets, it presents another problem-comets don't last that long either - and on top of it the Oord cloud is a myth. Hence the conundrum. At least this is how I read this enigma.

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.