Find the “Dwarf Planets”

Ceres
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S&T: Gregg Dinderman
The smoke has cleared. Pluto, Ceres, and 2003 UB313 are officially "dwarf planets." And they are all visible to amateurs tonight — if you have the right equipment. Grab your gear and try to catch these challenge objects!

The closest body on the list is Ceres, the largest object in the asteroid belt. It was originally bestowed planetary status when first spotted in 1801, but was soon downgraded as more asteroids became known. Right now Ceres is in the constellation Piscis Austrinus. It reached its peak brightness (magnitude 7.6) last week, and will slowly be fading past magnitude 8.6 throughout September. To find it, just use the chart on this page (click on the image for a printable larger view), and grab a pair of binoculars or a small telescope. Neptune isn't too far from Ceres, and as a fun coincidence, these two bodies are currently the same brightness. So while you're searching this section of sky, why not grab both?

Pluto and Charon
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S&T: Gregg Dinderman
Pluto and its companion, Charon, will be a much tricker find. You'll need a 10-inch telescope (or larger) and some pretty dark skies. Using the chart on this page as your guide, first track down Xi (ξ) Serpentis. Then go hunting for the elusive 13.9-magnitude spot. If you're using just your eyeball at the eyepiece, itshould be challenging — but possible — to see Pluto. To be absolutely sure, observe it on two successive nights and see if has moved.

Charon, at magnitude 15.7, is too faint to be seen in backyard scopes without the aid of a CCD camera. But if you're so equipped, give it a go. You'll need nearly perfect conditions and rock-steady seeing — Charon is around 0.7 arcsecond from Pluto so it will be tough to separate the pair. For more tips on imaging Charon, check out the article we published in September 2000 (available for purchase from our magazine archive).

Though fainter than Charon, 2003 UB313 isn't nearly as hard as to image, because it's not hidden in the glow of a brighter object. However, you'll still need a pretty big scope equipped with a CCD camera — unless your scope's mirror is 2 meters or bigger, in which case you might be able to detect it visually. Right now 2003 UB313 is magnitude 18.8, in Cetus, and it's high in the south during early-morning hours. Use the following table to help locate it, or visit the JPL Solar System Dynamics Web page to find its up-to-date location. As with Pluto, the only way to be absolutely sure you've captured 2003 UB313 is to image it on successive nights and see if its position has changed.

2003 UB 313
Date (0:00 Universal Time) RA Dec.
Aug. 21 1h 39.6m –5° 08'
Sep. 1 1h 39.4m –5° 10'
Sep. 11 1h 39.1m –5° 13'
Sep. 21 1h 38.6m –5° 15'
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