Looking Up column: Venus and Mercury’s evening show
Mid-spring evenings beckon us outside under the canopy of stars. Winter’s chill has receded. Soon, fireflies will add to the delight, acting like stars that dart about, competing for our attention. Grabbing out gaze this May, however, is gloriously bright Venus in the deepening twilight glow.
Just look west-northwest for this brilliant white point of light, the second planet from the sun. Venus started May at peak magnitude of -4.7, far brighter than anything else we normally see in the sky, other than the sun and moon.
It shines so bright because the planet is relatively close to us at this stage, is so near the sun and is shrouded by clouds which serve as a good reflector of sunlight.
If you have even a small telescope, turn it towards Venus this month. All you need is low magnification to quickly see its amazing crescent phase, similar to the crescent moon.
As Venus rounds the sun, between the Earth and sun, from our perspective, we watch it change in phase, depending on the angle the planet makes with the sun. The planet grows in apparent size, as its phase changes to an ever slimming crescent.
This keeps up till Venus is at “inferior conjunction” with the sun, on June 3. That is when the planet is practically right between Earth and the sun.
Because the orbits of the planet are out of sync with each other and not exactly on the same flat plane, Venus ordinarily just misses crossing in front of (transits) the sun. In fact, a transit of Venus occurs in a pattern that generally repeats every 243 years, and then happens in pairs, eight years apart. The last pair of transits happened in 2004 and 2012.
Meanwhile, as we watch the crescent Venus getting closer and closer to the sun in the evening sky, it also appears lower in the sky and sets sooner and sooner.
In early May Venus sets about three and a half hours after sunset; by late May Venus is visible only for a half-hour, low in the twilight glow.
Around May 15, you can start using binoculars, supported on a tripod, to detect the crescent. Some people with very sharp eyesight have claimed to have glimpsed the large crescent without any optical aid.
For an added treat, this month, the planet Mercury, which is yet closer to the sun than Venus, joins the evening show. Around May 11, you can start looking for Mercury in evening twilight, far below Venus. Be sure you have a low view to the west-northwest.
Mercury will be climbing closer and closer to Venus as the planets move in their orbits, and as Earth keeps hurling around the sun as well - like race cars or horses rounding a track.
On May 21, Mercury is closest to Venus, shining at -0.7, not as bright as Venus. Mercury will be right below Venus; the next night, Mercury is to the left.
Mercury will keep separating away and higher in the sky (upper left) as Venus pulls away.
Then on May 23-24, the thin crescent moon enters the evening sky, sliding under and to the upper left of Venus and Mercury.
Binoculars will make the view even more impressive.
Read Sky and Telescope and Astronomy magazines (or their websites) as well as other sources for more information about the spring sky. A couple of comets are also in view, brightening to naked-eye visibility. More on these later!
Last quarter moon is on May 14.
Keep looking up at the sky!
Peter Becker is managing editor at The News Eagle in Hawley, Pennsylvania. Notes are welcome at firstname.lastname@example.org. Please mention in what newspaper or website you read this column.