Eyes to the Sky: Earth at aphelion today, New Moon Monday


Today at 11 a.m., Earth will be at aphelion, the point in our orbit farthest from the sun. Earth's orbit around the sun is elliptical, or oval. If the orbit were a circle, with the planet in the center, Earth would be the same distance from our star all year. At aphelion -- from the Greek apo meaning "away" and heli(os), sun -- we are 94.5 million miles from the sun. Perihelion, when Earth was closest to the sun at 91.4 million miles distant, occurred on Jan. 1. The average distance is 93 million miles.

Although slightly less solar energy is reaching us at aphelion, summer's warmth results from, among other significant factors, the tilt of the northern hemisphere toward the sun: the sun's rays are more direct and potent.

Our star still lingers at its northernmost reaches, setting tonight at 8:33, just a minute earlier than its latest of the year. During these shortest nights, less than 9 hours from sunset to sunrise, stargazing for keen eyes begins at about 9 o'clock even though complete darkness, astronomical twilight, does not begin until 10:44.

Stargazing is best this week, since there's the charm of the moon without the overwhelming light. New Moon, when the moon is dark, occurs on Monday at 3:14 a.m. A waning early morning crescent in the east precedes the dark moon; a waxing early evening crescent appears in the west in the days following New Moon.

Planet Venus is the first celestial body to shine through the sunset glow this week. On Wednesday and Thursday, look for a wisp of a crescent moon near Venus and Leo's Regulus, low in the west-northwest. Moonset Wednesday is 9:36; Thursday 10:05.

To contact Judy Isacoff, M.A. go to www.naturesturn.org



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