While many astrobiologists follow the water, some are following the dirt. SETI Institute astronomer Peter Jenniskens is hot on the trail of an elusive comet whose last visit was in 1976, and whose lingering debris may help scientists warn us about the imminent return of a mysterious class of Near Earth Objects (NEOs).
We believe that prediction models tested on the Leonid showers can also be used to predict when these dust trails are steered in the Earths path by the gravitational influence of planets, and we are about to travel to South Africa to observe a new meteor shower thus predicted.
When Comet C/1976 D1 Bradfield passed uncomfortably close to Earths orbit on its sweep through the inner solar system, it was a faint +8 magnitude binocular object in the Southern hemisphere. Its passing was poorly communicated by observers who lacked todays connectivity. The best determination astronomers can make of the comet orbit places a return visit about 1,000 years into the future.
Before we all heave a sigh of relief, thousands of such comets remain undetected. A similarly sized comet in such a fast moving orbit in another solar system may long ago have wiped out a civilization before it could be detected in our SETI searches.
The key to finding the approaching comets is to recognize the new meteor shower when Earth hits its dust trail.
In a paper soon to be published in the journal Icarus, Finnish colleague Esko Lyytinen and I predict a number of such showers, first on the list is the trail of C/1976 D1.
Joining members of the Astronomical Society of South Africa - Meteor section just outside of Cape Town in South Africa, we hope to witness the meteor outburst, which peaks at 21:54 GMT (give or take 20 minutes) on March 1 and will last for approximately half an hour (14 minutes, full-width at half-maximum). The showers radiant will be in the southern constellation Tucana, the Toucan, and will become known as the "Beta Tucanids."
The dust trails stretch far in front of and behind the comet, but that only when the planets cooperate can we observe a meteor shower. Jupiter and the other large outer planets in our solar system tug upon the path of comet dust particles. The tugging perturbs the orbits of the dust trails such that they are moved into Earths path about once or twice every sixty years, through the combined effects of Jupiter and Saturn planets with 12 and 30-year rotation periods.
A successful observation will help read other such showers for useful information regarding their parent comet. These encounters offer a chance to study the comets debris and infer properties such as comet size, surface composition, and orbit. Repeated observations can in principal reveal whether a long period comet is approaching us, or returning back to the dark frontier of the solar system far beyond the outer planets.
The viewing location is not idealunfortunately, the best seats in the house are found in hard to get to locations in Antarctica. Are we disappointed that we may never see this elusive comet again? Not at all. Whats left behind after the comet has departed can provide as important information and were learning to read the playbill.
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