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| This month’s star chart
shows the southern sky at 9:00 PM on October 5, 2002, the night of our
scheduled star party. Uranus and Neptune are well placed in the southern
sky about 30 deg above the horizon.
Under a good sky, Uranus at mag 5.7 is a naked-eye object, and easy to see in binoculars. The planet is about 2 1/2 deg NE of a 3rd mag star, Deneb Algedi, in one of the horns of Capricornus, the Goat (don’t confuse Deneb Algedi with our more familiar Deneb in the tail of Cygnus, the Swan). Uranus is now about 2 billion miles from the earth. It has an apparent diameter of nearly 4 arcminutes, clearly a little blue-green ball in a scope. Neptune, at mag 7.9, is not a naked eye object. With an apparent diameter of about 2 arcminutes, it is a tiny blue-green object in a scope, but it is more extended than the image of a star. Neptune is now about 2.8 billion miles from the earth. Uranus takes 84 earth years to orbit the sun, and Neptune takes 165 years. Thus, these outer planets move through our sky very slowly. Uranus moves a little more than 4 degrees per year, barely half of the field of view of 7-power binoculars. Neptune moves about 2 deg per year, so these planets will not stray far from their current region of the sky for several years. For comparison, consider how rapidly Venus and Mercury move around. The Teapot in Sagittarius remains well placed this month, with its numerous Messier objects. This is one of the richest areas in the sky in terms of star clusters and nebulae. Have a look at this area before it drops below our western horizon. |
You can print a copy of this star chart so you can take it outside.
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