Stargazers: See a double planet and more!


Have you noticed those three bright stars appearing low in the western sky shortly after sunset? Well, I've been waiting all summer to tell you about this, because these aren't stars at all. They're planets.

Elusive Mercury appears very low in the west this week, and above it appear the two brightest planets, Jupiter and Venus. They're gearing up to put on quite a show for stargazers later this week.

The brighter of the two is Venus, a rocky world that is about the same size as our own Earth and shrouded by highly reflective clouds. The fainter (but still quite bright in its own right) is the gas giant planet Jupiter.

Jupiter and Venus appear to be converging from night to night because they orbit the sun along with our Earth, and our constantly changing viewpoint makes them appear to drift against each other and the more distant and "fixed" stars.

On the evening of Saturday, Aug. 27, these two will appear remarkably close together, only about 1/10 of a degree apart, and they will form a bright double star in our western sky at dusk. Depending on sky conditions, your location and your vision, you might even need binoculars to see them as two distinct bodies.

This will be a great time to aim a low-powered telescope in their direction, since both will appear in the same field of view. Stargazers will see not only the disk of cloud-covered Venus but also that of Jupiter with its cloud bands and four Galilean moons, which will all appear that night between the two planets. Unfortunately, Jupiter and Venus are so distant right now that they will not appear very large in your eyepiece.

A few evenings later another solar system body will enter the scene: the moon. On the evening of Friday, Sept. 2, Venus will have moved eastward, and the waxing crescent moon — complete with a full disk of Earthshine, light reflecting back onto the lunar dark side from the Earth itself — will appear between the two. You'll need to get outside about a half-hour after sunset to catch it at its best, though.

Aim binoculars in the direction of the moon-Jupiter pair and you'll be stunned by how three-dimensional the scene appears. Of course, this is purely an illusion because we're unable to perceive true depth in the cosmos. But it sure does produce a pretty picture.

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