By Larry Klaes
Tau Zero journalist Larry Klaes now looks at recent activity in near-Earth space, where a variety of objects have turned up just this year to remind us of the potential danger of impacts on our planet. With good connections at Cornell University, Larry is our point man for Arecibo information, the more of which the better as we assess the near-Earth asteroid issue and what can be done if one of these rogue objects is found to be on a collision course.
The last two months have seen a fair number of objects from space making rather close encounters with the terrestrial worlds of our Solar System.
In late January, a small planetoid designated 2007 WD5 made a relatively close pass of the planet Mars. Astronomers had earlier projected the planetoid might actually strike the Red Planet and hoped that one of the robotic spacecraft currently in Mars orbit would be able to record the 164-foot wide rock’s impact on the planet’s surface. However, as the scientists made refinements to their information on 2007 WD5’s solar orbit, the odds of such a collision dropped from 1 in 75 to 1 in 10,000.
While there is still a chance that the space rock did hit the Red Planet, more than likely it is now circling the Sun again. 2007 WD5 is currently too small and remote for Earth-based astronomers to monitor for now, nor does this Near Earth Object (NEO) have any chance of impacting our planet in the next century or so, based on the best understanding of its solar orbit.
Had 2007 WD5 struck either world, however, it would have impacted in a manner similar to the object that struck in what is now Winslow, Arizona some 50,000 years ago. Known as Meteor Crater (though it should be more properly called Meteorite Crater), the impactor made a ground scar one mile across that is still visible today and remains a significant tourist attraction. The shock waves from the impact would have killed any living creature within twenty miles of ground zero.
Just a few days before planetoid 2007 WD5 flew by Mars, another somewhat larger object named 2007 TU24 passed by Earth just a bit further than the distance of our Moon. Despite some early concerns about a possible impact with our planet and several inaccurate and deceptive commentaries about this planetoid causing havoc with our world, 2007 TU24 proved not to be a threat. The space rock did, however, prove a boon to science with its close flyby, allowing the Arecibo Observatory in Puerto Rico to bounce radar signals off its surface in late January and early February and return images three times better than the next best radar telescope.
“We have good images of a couple dozen objects like this, and for about one in ten, we see something we’ve never seen before,” said Mike Nolan, a senior research associate at Cornell, to the Cornell Chronicle. “We really haven’t sampled the population enough to know what’s out there.”
Image: The largest single-dish telescope in the world, Arecibo proves uncommonly effective at detecting and tracking the kind of objects that in the past may have caused mass extinctions. Keeping its planetary radar in operation is crucial to planetary security. Credit: National Astronomy and Ionosphere Center/Cornell University/NSF.
One week later, another space rock labeled 2008 CT1 came within 84,000 miles of Earth, just two days after its discovery by the Lincoln Near Earth Asteroid Research (LINEAR) project at New Mexico’s White Sands Missile Range. Although 2008 CT1 is only the size of a large pickup truck and not likely to return to our neck of the Solar System until 2041, recent studies indicate that even relatively small objects impacting from space can cause major damage. The celestial body that caused the Tunguska Event, flattening many square miles of Siberian forest one hundred years ago this June, was recently determined to be smaller than previously predicted at just over 100 feet across.
In early February, Arecibo radar imaged another planetoid — 2001 SN263 — making a 7 million mile pass at Earth. Though little was known about this 1.5-mile wide space rock since its discovery by LINEAR in 2001, the planetoid turned out to be holding a major surprise: It was a triple system, the first such NEO ever discovered.
“We did not have much information about 2001 SN263 until we started observing it,” explained Nolan, who is also the head of the Solar System group at Arecibo and the assistant director for technical services at the observatory. “We chose it because it was fairly large (~2.5 kilometers in diameter) and well placed in the sky for us to be able to observe it over a relatively long interval (about 10 days). Many NEOs are visible for only a few days at Arecibo.”
To obtain the image of 2001 SN263, Arecibo transmitted a 500,000 watt radar beam towards the planetoid. The radar echo power received with Arecibo’s ultra-sensitive detectors and processed into these images totals less than a billionth of a billionth of a billionth of a watt.
The radar images depict a spherical main body surrounded by two smaller elongated companions. Nolan suspects that these two “satellites”, one of which is roughly the size of the Arecibo radio telescope, orbit the larger body, but more data is required to be certain of this. As for the composition of 2001 SN263, Nolan says that “from recent spectroscopy done by coworkers, it appears to be ‘primitive’, meaning rock and organic material that has not been heated very much.”
While Nolan and his team do not yet know how this triple NEO came to be, they do know that the planetoid will not cross Earth’s solar orbit for at least the next one thousand years. This discovery will certainly help in science’s understanding of other planetoid and cometary bodies which are also part of multiple systems and the formation and behaviors of NEOs in general.
Although certain planetoids and comets are a threat to organisms on Earth, their potential impact may also ironically save some of our planet’s lower life forms by reseeding our world or another such as Mars with terrestrial microbes.
In a new paper in the Spring, 2008 issue of the journal Astrobiology, Gerda Horneck and colleagues report on their experiments with a variety of simple organisms in surviving the shock of a celestial impact and the subsequent catapulting into space with the debris flung upwards from the collision. Their tests show that certain creatures could indeed survive such an event and reach other worlds, or return to a damaged Earth to begin a new evolution of life. Centauri Dreams‘ story on this work is here.
Hi Paul;
It is interesting that the rock in the Tunguska Event was smaller than 100 feet accross. To be able to detect such small rocks would be very useful also.
I am amazed at the sensitivity of the Arecibo Dish’s electronics. 10 EXP -27 watts is tiny, about (10 EXP – 8) eV/second. This corresponds to the equivalent of one optical light photon every 3 years.
Thanks for this fascinating article!
Jim
PS sorry for that goof-up. A yellow smiley face showed up instead of the exponent of -8 in my previous posting.
Jim, you’ve run into a limitation of our software, which occasionally does the unexpected — not to worry about the exponent problem, and as soon as I figure out what causes it, I’ll post the answer here.
anyone know if the 500k watt radar beam from arecibo would be detectable from another solar system assuming they were “listening” at the right time?
would it be possible with a system like SETIs ATA?
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anyone know if the 500k watt radar beam from arecibo would be detectable from another solar system…
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Something I’ve also wondered about. Also wondering how the gravitational lens of another star might affect the signal. If such a lens would affect the signal then I imagine being boosted by ten to the eighth power would allow the signal to be detected from a fair distance.
500 kW from Arecibo at 1+ GHz? That would be detectable out to quite a distance – many l.y. There are a variety of factors and assumptions to calculate how far (which I won’t bother to calculate), in particular on the receiving end.
According to Spaceweather.com:
NEO ALERT: Discovered just yesterday, small asteroid 2008 EZ7 will fly past Earth tonight at a distance of only ~100,000 miles. Using an ephemeris from the Minor Planet Center, advanced amateur astronomers may be able to find and photograph the space rock racing among the stars. Submit your images here.
http://cfa-www.harvard.edu/mpec/K08/K08E67.html
ASTEROID FLYBY: Newly-discovered asteroid 2008 EZ7 flew past Earth last night at a distance of only ~100,000 miles. Amateur astronomers Ivan Majchrovic and Tomas Maruska photographed the 18-meter wide space rock racing across the starry skies of Slovakia:
http://www.spaceweather.com/swpod2008/09mar08/maruska1.gif
The video consists of ten 4s exposures taken through a 2.5-inch refractor. They used this ephemeris to guide their telescope.
Normally, an asteroid as small as 2008 EZ7 would attract minimal attention. Even if it hit Earth, the result would be little more than a bright fireball and a sprinkling of meteorites across some uninhabited stretch of our planet. 2008 EZ7 may prove to be more interesting, however; rumor has it that a second space rock provisionally named “BJ19377” is following 2008 EZ7 in a similar orbit and will soon make its own close approach. Could this be a twin asteroid flyby? Stay tuned for updates.
Black holes could bump asteroids our way
NewScientist news service Mar. 10, 2008
*************************
A physicist at Lebedev Institute in
Moscow suggests that if all dark
matter is black holes, they would
likely pass through the asteroid
belts in our galactic backyard.
Since a meter-sized primordial black
hole can have the mass of the Earth,
it would need only to pass near an
asteroid to knock it out of a safe
orbit and towards our planet….
http://www.kurzweilai.net/email/newsRedirect.html?newsID=8162&m=25748
The search for Primordial Quark Nuggets among Near Earth Asteroids
Authors: J.E. Horvath (IAG-Usp, Brazil)
(Submitted on 12 Mar 2008)
Abstract: Primordial Quark Nuggets, remnants of the quark-hadron phase transition, may be hiding most of the baryon number in superdense chunks have been discussed for years always from the theoretical point of view.
While they seemed originally fragile at intermediate cosmological temperatures, it became increasingly clear that they may survive due to a variety of effects affecting their evaporation (surface and volume) rates. A search of these objects have never been attempted to elucidate their existence.
We discuss in this note how to search directly for cosmological fossil nuggets among the small asteroids approaching the Earth. “Asteroids” with a high visible-to-infrared flux ratio, constant lightcurves and devoid of spectral features are signals of an actual possible nugget nature. A viable search of very definite primordial quark nugget features can be conducted as a spinoff of the ongoing/forthcoming NEAs observation programmes.
Comments: 4 pp., no figures, to appear in A&SS
Subjects: Astrophysics (astro-ph)
Cite as: arXiv:0803.1795v1 [astro-ph]
Submission history
From: J. E. Horvath [view email]
[v1] Wed, 12 Mar 2008 15:08:45 GMT (15kb)
http://arxiv.org/abs/0803.1795
Huge Meteorite Impact Found In UK — Britain’s Largest
Science Daily 3/31/08
Evidence of the biggest meteorite ever to hit the British Isles has been
found by scientists from the University of Oxford and the University of
Aberdeen. The scientists believe that a large meteorite hit northwest
Scotland about 1.2 billion years ago near the Scottish town of Ullapool.
Previously it was thought that unusual rock formations in the area had been
formed by volcanic activity. But the team report in the journal Geology that
they found evidence buried in a layer of rock which they now believe is the
ejected material thrown out during the formation of a meteorite crater.
Ejected material from the huge meteorite strike is scattered over an area
about 50 kilometres across, roughly centred on the northern Scottish town of
Ullapool.
Full article here:
http://www.sciencedaily.com/releases/2008/03/080330190410.htm
Canadian satellite to detect Earth hits
http://www.spacedaily.com/reports/Canadian_satellite_to_detect_Earth_hits_999.html
by Staff Writers
Ottawa (UPI) May 2, 2008
Canadian researchers are working on a tiny satellite that will
alert the world to the potential of asteroid strikes.
“This is the first space-based asteroid-searching telescope,” said
Alan Hildebrand of the University of Calgary (Alberta), one of two
principal scientists for the satellite.
He told the Canwest News Service the Near Earth Object Surveillance Satellite, set to be launched within two years is “the first space-based asteroid-searching telescope.”
Once completed, the NEOSSat device will weigh only 135 pounds,
and will be the size of a small suitcase, the report said.
“I think the most exciting thing about this mission is we are going
to find asteroids that are accessible from our planet,” Hildebrand said.
He said the mini-satellite would also help define celestial origins.
“We’ve been to the moon. There’s always more you can do (there),
but asteroids have so much more to teach us about the origins of
the solar system,” Hildebrand told the news agency.