MESSENGER still looking for Vulcanoids

Thursday, February 12, 2009

Mercury just before sunset when it's about as far away from the Sun from our point of view as it can get. Since Vulcanoids would be tiny and located even closer to the Sun than that, there's pretty much no chance of discovering them from Earth.

MESSENGER is still looking for Vulcanoids, theoretical asteroids that would exist in between Mercury and the Sun but still haven't been discovered. Since there's a gravitationally stable region between Mercury and the Sun that should hold these bodies I expect that we will eventually find some of them, and let's not forget that over the past two decades or so the Solar System has only proven to be more and more interesting as time goes on, so I don't see why this wouldn't be true in regions close to the Sun as well as far away from it.

Here's what MESSENGER is doing:
MESSENGER reaches its orbital perihelion today and passes within 0.31 astronomical units (AU) of the Sun (one AU is nearly 150 million kilometers or 93 million miles). The mission's imaging team is taking advantage of the probe's proximity to the fiery sphere to continue their search for vulcanoids - small, rocky asteroids that have been postulated to circle the Sun in stable orbits inside the orbit of Mercury.
and on the region where they should exist:
The so-called vulcanoid region between the orbit of Mercury and the Sun is the main gravitationally stable region that is not known to be occupied. The region is, however, the most difficult to observe. Any vulcanoids would be difficult to detect from Earth because of the strong glare of the Sun. Previous vulcanoid searches have revealed no bodies larger than 60 kilometers in diameter. But MESSENGER's travels in near-Mercury space enable a search for vulcanoids from a vantage never before attempted, says MESSENGER Science Team Member Clark Chapman, who is spearheading the team's search along with his associate, William Merline.

"With MESSENGER, we can search for vulcanoids as small as 15 kilometers across," said Chapman, a senior scientist at the Southwest Research Institute in Boulder, Colorado. Between February 7 and 11, the wide-angle camera of MESSENGER's Mercury Dual Imaging System will have snapped 256 images in the areas east and west of the Sun. Because of the danger of the Sun's glare, the camera will have to peek just past the probe's sunshade to capture images.
The page on Wikipedia on Vulcanoids reminds us that there are actually a few ways to conduct searches for these asteroids from Earth:
If they exist, the vulcanoids could easily evade detection because they would be very small and drowned out by the bright glare of the nearby Sun. Due to their proximity to the Sun, searches from the ground can only be carried out during twilight or solar eclipses. They are most likely to be between 100 metres and 60 kilometres in diameter and located in nearly circular orbits near the outer edge of the gravitationally stable zone.
And here's another way:
Later attempts to detect the vulcanoids involved taking astronomical equipment above the interference of Earth's atmosphere, to heights where the twilight sky is darker and clearer than on the ground. In 2000, planetary scientist Alan Stern performed surveys of the vulcanoid zone using a Lockheed U-2 spy plane. The flights were conducted at a height of 21,300 metres during twilight. In 2002, he and Dan Durda performed similar observations on an F-18 fighter jet. They made three flights over the Mojave desert at an altitude of 15,000 metres and made observations with the Southwest Universal Imaging System—Airborne (SWUIS-A).
Shouldn't Virgin Galactic be able to conduct similar observations in addition to sending people up into suborbital space?


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