July 30, 2010

Hunting for Ceres in the Pipe Nebula

Ceres is the largest asteroid in the solar system, and is usually bright enough to be visible with telescopes and even binoculars (at around a magnitude of 7). However, unlike the brighter planets, it is not so bright to be able to be distinguishable from the stars that may surround it. Normally to do that would require taking multiple exposures of the field to see which one of the dot moves1, or at the very least, looking at charts giving its position in relation to other stars. However in the month of July, due to its special position, identifying became a lot easier.

In July, Ceres passed in front of Barnard 78 (or the Pipe Nebula), a nebula in the Ophiuchus constellation made up of dark dust and gas. This opportune position allows the nebula to block out background stars which may be confused for the asteroid. Since Ceres is in our solar system, it isn't blocked out, allowing it to be made out easily.

When I observed Ceres on July 20 with my 15x70 binoculars, it took me just a few minutes to identify which dot was Ceres. If you have binoculars or a telescope, definitely try and go outside to see this asteroid. This special position won't last for long!

When hunting for the asteroid, using a chart from a computer is immensely helpful. I used charts from the iPhone/iPad app SkyVoyager and the July issue of Astronomy magazine.


1: Since the Earth rotates, stars rise in the east, move across the sky, and set in the west, just like the Sun. Asteroids (and also planets) also move in their orbits, so in addition to rising and setting, they move across the sky not following the other stars [this is why the name planet comes from the Greek work “wanderer”]. When taking multiple exposures and aligning the stars in the pictures, the one that moves is the asteroid, since it is not following the movement of the stars.

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