Five Planets to Be Visible; Abrams Offers Viewing

Above: The moon and Venus, as seen from East Lansing a few months ago

This Friday and Saturday, July 15 and 16, mark the start of a five-week interval when all five bright planets or our solar system can be observed during evening twilight in East Lansing.

Three of the planets are now easily visible to the unaided eye by an hour after sunset, when the sky becomes sufficiently dark. By 10:15 p.m. this weekend, in the East Lansing area, bright Jupiter is in the west, about 16 degrees above the horizon, while Mars is between south and south-southwest, about 25 degrees up. At that time, these two planets are brighter than any stars in the summer evening sky, so they will be easy to find even from brightly lit areas. Mars has an apricot-colored tinge, distinctly redder than yellow-white Jupiter.

The third planet easy for unaided eye is Saturn, some 16 degrees left of Mars and almost due south an hour after sunset.

Except when they’re very low in the sky, planets can usually be identified by their steady light, unlike the twinkling or flickering light of the distant stars. Compare Saturn to the reddish twinkling star Antares, just 6 degrees to Saturn’s lower right. The twinkling of stars is caused by the Earth’s atmosphere.

To see the other two planets in mid-July, you must look quite early during evening twilight, before the planets set; binoculars will help pick out the close pair in bright twilight.

On July 15 and 16, using binoculars, start searching very low in the west-northwest about 15 minutes after sunset. If the sky is very clear, you’ll spot Venus only about 3 degrees above the horizon, so you’ll need to observe from a place with an unobstructed view, such as the top of the Parking Ramp behind Abrams Planetarium, where we’ll have free public viewing sessions.

On Friday, July 15, fainter Mercury will appear only 0.8 degree to the right of Venus. On Saturday, Mercury will appear just 0.5 degree to the upper right of Venus. On both evenings, these two innermost planets of our solar system will easily fit within the low-power field of view of a telescope.

In coming weeks, the planets will change their arrangements in the sky. Moving to the upper left, Mercury will be higher than Venus from July 16 through August 16. Mercury will still be within a degree to upper left of Venus on July 17, moving out to 4 degrees by July 22, out to 7 degrees by July 29, and out to 9 degrees upper left of Venus during August 4-16.

Venus will gradually set longer after sunset and become easy for unaided eye as this summer progresses, but Mercury may require binoculars throughout its July-August unfavorable evening apparition because it remains low in bright twilight. Fading Mercury will pass within 4 degrees lower left of Jupiter on August 19.

In August, Jupiter will move lower into the western twilight glow (because of the Earth’s faster revolution around the Sun), and on August 27, it will be in a spectacular close pairing with Venus. Just keep track of Jupiter with unaided eye and binoculars until then, and you’ll be sure to catch it.

A few days earlier, in a very eye-catching arrangement on August 23 and 24, Mars passes below Saturn and just 1.8 degrees above the reddish twinkling Antares, heart of the Scorpion. On the two evenings, the three bodies will lie in a nearly straight line just over 6 degrees long, in the south-southwest at dusk.

The Moon will be visible in the early evening sky again during August 4-17. On August 4, the thin crescent will appear very low in the west near Mercury and to upper left of Venus. On the next evening the lunar crescent will appear near Jupiter, and on August 11, a gibbous Moon will appear in a beautiful diamond-shaped arrangement with Mars, Saturn, and Antares.

On August 17, Venus is 10 degrees to the lower right of Jupiter and appears one degree closer each day. On the same date, the Moon is in the east-southeast at dusk and is full overnight.

Abrams Planetarium at Michigan State University has scheduled special sky watching sessions this weekend after its 8:00 p.m. public programs. The Moon and planet-watching sessions will be held, if skies are clear, on July 15 and 16 from 9:20 p.m. until 10:30 p.m. on the top level of the Parking Ramp immediately behind the Planetarium. Access to the top level is by elevator at the southwest corner of the Ramp, or by stairway at the southwest or northwest corner.

For illustrations of gatherings of Moon and planets, we recommend the Sky Calendar, available by subscription for $12 per year from Abrams Planetarium or online.

Robert C. Victor was Staff Astronomer at Abrams Planetarium, Michigan State University. He is now retired and enjoys providing skywatching opportunities for school children and the general public.