Evening Twilight

Venus dominates the evening twilight. Look tonight, a few minutes after sundown, toward the western horizon to spot a bright star.

That’s Venus.

Our sister world continues a slow but steady shift eastward each night. Venus glides toward the southwest moving from Virgo to Libra without gaining altitude. Tonight, look to the left of Venus about 7 ½ degrees as the twilight darkens a bit to spy Spica, the brightest star of Virgo. Venus creeps about a degree per night toward Spica.

On Sept. 1, Venus will be 4 ½ degrees to the right of Spica. Watch on the nights of Sept. 4-6 to see Venus pass within 1 ½ degrees above Spica. By Sept. 7, Venus will have passed Spica by more than 3 degrees.

A skinny crescent Moon joins the widening pair on Sept. 9.

Mercury makes a poor appearance this month. An ultra-thin crescent moon will sit about 3 ½ degrees above Mercury on Sept. 8. Mercury continues hugging the western horizon for about three weeks before it slides into the sunset’s glare.

Saturn, Jupiter and Neptune are up all nightTelescope observers can enjoy a trio of gas giants this month. Saturn is now well placed in the south as the sky darkens. Best viewing for Saturn tonight is just after 11 p.m. By mid-month, observers can enjoy best views of Saturn in the south by 10 p.m.

About an hour later, Jupiter follows Saturn. By Sept. 15, Jupiter is best observed by just after 11 p.m. Telescope observers should circle Sept. 12, 18 and 25 as nights to watch Jupiter’s moon Io creep across the disk of Jupiter. Europa does the same transits on Sept. 19 and 26.

Binocular observers should look at Jupiter on Sept. 6 and 20 to see all of the four Galilean moons lined up on the east and the west side of Jupiter.

Neptune is visible all night on Tuesday, Sept. 14. The most distant gas giant will be more than 2.7 billion miles from Earth and shine at a dim 7.8 magnitude in Aquarius. Look about 30 degrees from bright Jupiter to search for Neptune.

Neptune will be best observed about 2 hours after Jupiter.

Umpqua Astronomers MeetingUmpqua Astronomers and the interested public can join a virtual meeting monthly on Zoom. The meeting time is 7 p.m. Sept. 14.

For more information visit umpquaastronomers.org, bit.ly/2CDXbll, email uastronomers@gmail.com or call 541-673-1081 for details about how to join the meeting.

Paul Morgan is an astronomer at Umpqua Community College.

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