Diagram of Venus and Jupiter Venus can never be more than 47 degrees from the sun, whereas Jupiter can have any angle from the sun. Thus in last month’s puzzle, Planet A at 90 degrees from the sun can only be Jupiter and by elimination Planet B can only be Venus. Diagram by Frank Sanders.[/caption]

Last month, we asked how Jupiter and Venus, looking almost alike as the two brightest planets in the sky, can be distinguished from each other based purely on their sky positions. An example picture was provided, showing them as unknown planets A and B in early-February Nederland evening skies.

The answer is: Venus, orbiting between the earth and the sun, can never be more than 47 angular degrees (about half of a right angle) from the sun, as shown in the accompanying diagram. You can test that angle with your outstretched arms: point one arm toward the sun’s position below the horizon and the other toward a bright planet that might be Venus. If your arms are spread more than half of a right angle, then Venus is eliminated and the planet in question can only be Jupiter.

Jupiter, orbiting further from the sun than us, can conversely appear at any angle from the sun, all the way out to 180 degrees opposite the sun (called opposition).

So, as pictured in last month’s diagram, if Planet A is 90 degrees from the sun it can only be Jupiter. That leaves Planet B, at about 40 degrees from the sun, as necessarily being Venus.

This angle trick only works when Jupiter is more than 47 degrees from the sun. If both planets are within that angle from the sun (as they are this month), then the only way to visually guess their identities is to figure that the brighter one is probably Venus. Positive identification then depends on looking at them with binoculars or a telescope. Jupiter will be a full disk with its four largest moons while Venus will be solitary (no moons) and will generally show a crescent or gibbous shaped phase like our moon.

Speaking of a side-by-side arrangement, at the beginning of this month, on March 1 and 2, Jupiter and Venus will be right next to each other (at conjunction) low in the sunset sky. They will be separated by only about the width of a full moon. Venus will be to the right, Jupiter to the left, with the pair setting by 8:20 p.m.

Backyard Astronomy Lecture Series: This columnist will conduct a four-part lecture series, called Backyard Astronomy, at the Nederland Public Library on the first Wednesday evenings of April through July, with a bonus talk, How Far is That Star, on the first Wednesday of August. Find details and get registered at https://nederland.colibraries.org/backyard astronomy/.

Also in March skies:

The sun begins the month in Aquarius, entering Pisces on March 11. The equinox falls on Monday, March 20 at 1:46 p.m. in Nederland. At this moment, the sun enters the northern hemisphere; days equal nights at 12 hours each; and astronomical spring begins. Throughout March, days lengthen and nights shorten at the fastest rate of the year, the maximal rate of daylight growth being on the equinox itself.

Daylight Saving Time (DST), when we set our clocks forward an hour, begins at 2 a.m. on Sunday, March 12.

The moon’s dates are: Full (Worm Moon) March 7; Last Quarter March 14; New March 21; First Quarter March 28.

March Meteor Showers: The Gamma Normids, a weak shower, will peak on March 15 between 4 a.m. to sunrise.

Best Sky Viewing Nights (Minimal Moon): March 14-28.

Sunset (Mid-Month): Mars is directly overhead, next to bright Elnath and close to brilliant Capella. Orion is due south, with Sirius and Canis Major at south-southeast. The Twins, Castor and Pollux, are very high in the east. The Great Square of Pegasus is low in the west.

Midnight (Mid-Month): Vega rises in the northeast with the Big Dipper high in the north. Follow the Dipper’s arm as you Arc to Arcturus (in Bootes), then continue moving on the same arc until you hit

bright-white Spica (in Virgo). The twin stars Zebeneschemali and Zubenelgenubi, in Libra, rise in the southeast. The trapezoid of Corvus is high in the south. Pretty, reddish Alphard (The One Who Stands Alone) is isolated in the southern sky.

Sunrise (Mid-Month): Bright red Altair, in Aquila (the Eagle) is high in the southeast, forming the Navigator’s Triangle with Deneb to its left and Vega practically overhead. Scorpius with burning red Antares is due south.

Mercury is lost in the sun’s glare.

Venus is in the western sky at sunset, climbing higher through the month. It sets around 10 p.m. DST.

Mars is nearly overhead in the early evening, dropping westward and setting around 2:45 a.m DST.

Jupiter is low in the west at sunset, dropping rapidly through the month and setting soon after sunset. It passes Venus on March 1 and 2.

Saturn rises barely before the sun; it is hard to spot this month.

Notable Space Missions: An Advanced Orion (aka Mentor) signals intelligence spy satellite is scheduled to launch from Cape Canaveral. Orion satellites, with colossally sized 300 foot wide antennas, fly in geostationary orbits where they hover above fixed places on the earth. (That’s how the Big Kids do it.) An uncrewed resupply mission launches to the International Space Station on March 11. Space X’s 33-engine Starship, a nearly 400 foot tall booster in the class of a Saturn V moon rocket, might fly its first orbital mission from a launch site near Brownsville, Texas this month. Space X has released no additional information. The FAA has not cleared Starship for flight as of press time.

Frank Sanders, a spectrum scientist at the U.S. Department of Commerce in Boulder, takes astronomy-related inquiries at backyardastronomy1@gmail.com.