by Robert Victor and Robert D. Miller

In evening twilight in June 2013, the brilliant evening “star” Venus gleams very low in the west-northwest, while Mercury lingers nearby during the first three weeks. Saturn glows yellowish and steadily well up in the south-southeast to south, contrasting with the twinkling blue-white star Spica just 13° to 12° to Saturn’s west (right).

On our evening all-sky chart, planets are plotted for each day when the Sun has sunk to 9° below the horizon, which we call “mid-twilight”. We have chosen that time, because we have found that by then, planets and stars of first magnitude or brighter are easily visible to the unaided eye, except those of lesser brightness low in the western twilight glow. In June, from Palm Springs, Los Angeles and other places near lat. 34° N, it takes until 46-47 minutes after sunset to reach mid-twilight. From northernmost California (lat. 42° N) this month, it takes about 9 minutes longer for the sky brightness to diminish to the same level. (more…)

by Robert C. Victor

Two difficult observations on Wednesday, December 12:

(1) Just over an hour before sunrise, try to see four planets simultaneously. It’s harder than it was two weeks earlier. Beginning with Venus, note Saturn 18° to its upper right, and Mercury just risen in ESE 6.5° to Venus’ lower left. When Mercury is 4° up, Jupiter is also 4° up, but in the opposite direction, WNW. If mountains don’t block your view, you might see all four of these planets at once. Note: Saturn-Venus-Mercury lie in a straight line. (2) Next, even more difficult, wait until about 30 minutes before sunrise, then extend the Mercury to Venus line 9° lower left of Mercury, and, using binoculars, there you may find a very thin crescent old Moon less than 3° above the horizon. From the Coachella Valley near Palm Springs, the Moon is just 18.5 hours before New. (New Moon occurs on Thursday, Dec. 13 at 12:42 a.m. PST).  (more…)

by Robert C. Victor

Saturn emerges in morning twilight to the lower left of Venus and the star Spica by the second week of November. Venus will pass within 4 degrees north of Spica on Nov. 17, and will appear less than a degree from Saturn on the mornings of Nov. 26 and 27. These close pairings will be very interesting to follow for several consecutive mornings around those dates. Mercury will have a fine morning twilight apparition low in ESE to SE sky during Nov. 24-Dec. 28. Look for our solar system’s innermost planet to the lower left of Venus, within 10 degrees Nov. 29-Dec. 28, and within 6.5 degrees Dec. 5-12. During Mercury’s morning apparition, four of the five naked-eye planets will be visible simultaneously! (more…)

by Robert Victor

These are great months for viewing bright planets in the early evening! Students will enjoy following brilliant Venus and Jupiter through their closest pairing on March 13, and viewing four planets simultaneously in late February and early March. During Feb. 22-Mar. 7, the moon forms attractive early evening groupings with four of the five bright planets and three of the five bright zodiacal stars. After returning to the early evening sky on Mar. 23, the moon sweeps past four bright planets during Mar. 25-Apr. 6. (more…)

by Robert Victor

Several bright stars of April evenings will depart by the end of the school year. Watch them go! The April Sky Calendar and Evening Skies star map are available at www.pa.msu.edu/abrams/ABDNHAMar-AprSkies/.

Each year in the April evening sky, a large oval of bright stars, called the Winter Ellipse, or Winter Hexagon, heads toward the western horizon. Rigel, in the foot of Orion, the Hunter, will be the first of these stars to depart near the end of April. Next, in order of disappearance from mid-northern latitudes, are: (more…)

by Robert Victor

All-sky evening star charts and sky calendars for March and April 2011, illustrating events mentioned in this article, such as the moon passing planets and bright stars, and the Mercury-Jupiter pairing low in the west at dusk around March 15, can be found on the web at www.pa.msu.edu/abrams/ABDNHAMar-AprSkies/.

Follow the Moon!

The moon’s orbit stands nearly vertical in the sky soon after sunset each year in late winter/early spring for observers at mid-northern latitudes. In 2011, dates to follow the moon’s progress at dusk from thin crescent to Full are March 6-19 and April 4-17. On the first evening of each interval, the moon is not far above the horizon and the very thin crescent may be difficult to spot, especially if you have mountains to your west. Challenge your students to observe the young very thin crescent moon on Saturday, March 5, within 30 hours after new. About 25 minutes after sunset, the crescent sliver will be just 7 degrees up in the west and 13 degrees lower right of Jupiter. Notice its horns, pointing away from the sun, are pointing straight up!

For the next week, the moon climbs much higher each evening as it passes the bright stars of the zodiac. Encourage your students to face west about half an hour after sunset on Sunday March 6. Those who do so will be rewarded by the sight of a beautiful crescent moon not far to the right of Jupiter. On that date and on the next few evenings, as the sky darkens, alert your students to look for the faint bluish glow of earthshine on the moon’s dark, non-sunlit side.

By the latter half of the week of March 6-12, students may also begin to notice the planet Mercury a few degrees to the lower right of bright Jupiter. On each successive evening, Jupiter appears lower, owing to Earth’s faster revolution around the sun, and Mercury appears higher, owing to the innermost planet’s even faster revolution, until on March 15, the two planets appear to pass each other. That evening, some 45 minutes after sunset, Mercury and Jupiter are just two degrees apart, with fainter Mercury to the right of Jupiter. This will be the best conjunction, or pairing, of bright planets in the evening sky this year! (more…)