The Sky This Week from May 29 to June 5 – Astronomy Magazine

Wednesday, June 3Venus is in inferior conjunction at 2 P.M. EDT. When this occurs, Venus and Earth are on the same side of the Sun. Such geometry is only possible with the inferior planets Mercury and Venus, as well as any small solar system bodies, such as asteroids or comets, whose orbits take them inside the orbit of Earth.

Today also marks the 50th anniversary of the first American spacewalk, completed by Ed White during the Gemini 4 mission. Shortly after sunset tonight, you can spot the constellation with the same name Gemini the Twins in the west-northwest. Its two brightest stars, Castor and Pollux, appear side by side above the horizon, roughly 20 high an hour after sunset. These stars represent the heads of the twins, with their stick figure-like bodies beneath them, standing upright in the sky. Castor, the slightly fainter white star to the right of brighter and orange-hued Pollux, is a multiple-star system whose brightest components A and B are easy to split. Theyre about 5" apart in even a small telescope.

Beneath Gemini is Mercury, still visible after sunset. Well return here tomorrow, when the speedy planet reaches greatest eastern elongation.

Thursday, June 4Mercury is at greatest eastern elongation (24) at 9 A.M. EDT, but the best time to view it is this evening. The planet wont set until two hours after sunset, but it may be challenging to catch at only 7 above the horizon (for observers near 40 north) one hour after the Sun sets. Its magnitude is 0.4. Youll find the planet about 15 below Castor and Pollux, again sinking in the west-northwest as twilight darkens the sky. Through a telescope, youll see Mercurys 8"-wide disk is 36 percent lit.

The small planet will continue to both wane and set earlier each day, fading in brightness even as its disk grows in apparent size over the next two weeks.

Friday, June 5Full Moon occurs at 3:12 P.M. EDT. A penumbral lunar eclipse will also occur today, although it isnt visible for observers in the U.S. or Canada, nor much of South America. The eastern portion of South America, as well as Africa, Australia, Europe, and much of Russia, will be able to view all or part of the event. A penumbral eclipse occurs when the Moon passes through the lighter portion of Earths shadow, called the penumbra, causing a shading effect, although none of the Moon will go completely dark.

North American observers can still get in on the Moon action, however, by swinging binoculars or scopes to the Full Moon to enjoy the sprawling lunar landscape on display. Be aware that the Full Moon can be exceptionally bright through optical aid, however, and will put a serious damper on your night vision. If you have one, use a Moon filter in your scope; alternatively, crank up the power, which will spread out the light and make viewing more comfortable.

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The Sky This Week from May 29 to June 5 - Astronomy Magazine