Since the end of November, when Saturn and Mercury sunk into twilight, the evening sky has been devoid of bright planets. But that’s about to change, dramatically.
The brightest of the planets is Venus, alternating between its roles as the Morning and Evening “Star.” It spent most of 2017 as the Morning Star, finally sinking into pre-dawn glow just before Thanksgiving.
Having passed behind the sun (“superior conjunction”) on January 9th, it will be chasing the slower-moving earth throughout most of this year, as the Evening Star.
Venus splits its morning and evening duties equally, but enters and exits differently. Morning apparitions begin after Venus passes between the earth and sun (“inferior conjunction”), when its daily motion is fastest (much like a race car that moves across your field of view faster on the near side of the track than on the far side).
It’s also at its brightest, being close. Morning apparitions end with Venus on the far side of the sun, at its least bright, sinking slowly into morning twilight. Evening apparitions see a distant, less bright Venus creeping out of twilight, and end with a blazing Venus diving rapidly sunward.
While Venus completes an orbit every 225 days, it only laps earth every 585 days. So, it’s nineteen months since Venus began its last evening excursion.
This evening apparition will begin a little sooner after inferior conjunction than most, because it’s happening close to the Vernal Equinox, when the plane of the solar system stands almost vertically to the western horizon after sunset.
When will you first see Venus this year? Start looking very low in the west-southwest right after sunset. When you spot it, it will resemble a bright star, flickering against a backdrop of bright twilight.
Next column: Rebranding the supermoon.
Sky calendar through March 8th:
One hour after sunset:
Venus: W, extremely low (after 3/2)
One hour before sunrise:
Saturn: SSE, low.
Mars: SSE, low.
Jupiter: SSW, low.
Moon: First quarter 1:09 a.m. 2/23. Full moon 5:51 p.m. 3/1. Close to Jupiter 3/7.
Chris Anderson manages the College of Southern Idaho’s Centennial Observatory in Twin Falls. He can be reached at 208-732-6663 or firstname.lastname@example.org.