By: Joe Rao
Published: 04/13/2012 08:36 PM EDT on SPACE.com
The planet Venus is now at its peak of visibility in the evening sky this weekend, making now a prime time to spot the bright planet.
This weekend, Venus should appear in the western sky at sunset, weather permitting, and should be visible as a dazzling skywatching target nearly all night long. The planet can easily be spotted by the unaided, though small telescopes or binoculars can reveal its disc and, at times, phases.
The Venus sky map associated with this guide shows where to look in the western sky to see bright planet this weekend. The planet Jupiter can also be seen below Venus in early evening, with bright red Mars shining high up in the eastern sky.
Venus's weekend display follows months of eye-popping views of the planet since Aug. 16, when it officially became an "evening star" on Aug. 16. At that time, Venus appeared from our Earthly vantage point to be situated on the far side of its orbit, and was invisible due to its proximity to the sun in our sky. It took the rest of the northern summer and on into the first part of autumn before Venus finally began to make itself evident, low in the western sky soon after sunset.
As the northern winter began, Venus seemed to almost vault upwards, appearing progressively higher and more prominent in the sky at sunset, and setting a bit later each night.
On March 27, Venus arrived at its greatest elongation, which is the planet's greatest angular distance in the sky to the east of the sun (an angle of about 46 degrees). And while Venus has since begun to creep back toward the sun, it still has been setting progressively later. [Photos: Spectacular Venus Views by Skywatchers]
That brings us to this week. Currently, Venus is arriving at that point where it will set at its absolute latest time of the year.
Venus's nightly view
Some astronomy guidebooks will tell you that because Venus is a so-called "inferior" planet — a world that is closer to the sun than Earth — that you can never see it in the middle of the night. But this week, for many locations, Venus will be visible at the witching hour and for some localities well beyond the stroke of midnight!
The reason that this is possible is two-fold:
First, although Venus has started its march back toward the sun's vicinity, this process initially is rather slow. Indeed, this week Venus' elongation from the sun measures 44 degrees; just 2 degrees shy of its greatest elongation that it attained about three weeks ago. (Your closed fist held at arm's length covers about 10 degrees of the sky).
In the interim, Venus has been progressing eastward along the ecliptic and in the process also moving northward through that part of the sky that the sun itself will be traversing during May and June. In other words, Venus has been describing a high arc across the sky, which is why at sunset it appears from mid-northern latitudes to be nearly halfway from the horizon to the point directly overhead (the zenith).
This also means that Venus remains visible after sunset for between three-and-a-half hours (at 30 degrees North) and five-and-a-half hours (at 60 degrees North)!
The other reason is that because the length of daylight is increasing, the sun is setting progressively later. But a more important factor came into play on the second Sunday in March (the 11th) when most places in North America observed the start of Daylight Saving Time.
Indeed, pushing the clock ahead forestalled (for an hour) the setting of the sun, as well as the setting of Venus. So, for example, from New York City, this week Venus would appear to set at 10:36 p.m. Eastern Standard Time, but adding the extra hour delays Venus’ setting until 11:36 p.m. Eastern Daylight Time (EDT).
I work as an on-camera meteorologist at News 12 Westchester in New York and head home for work after our 10 p.m. newscast. In recent nights, traveling home, I've had Venus for a companion, shining brilliantly near the west-northwest horizon. Fantastically odd, since usually when I head home Venus is long gone from the sky, having already set some hours before.
And for those places located near or along the western flank of a particular time zone, Venus will appear to set even later, in some cases after midnight.
Let me use two locations to drive home this point: Eastport, Maine, and Indianapolis, Ind. Both are located in the Eastern time zone. Each time zone is generally 15 degrees in width, but Eastport is near the eastern flank of the zone and Indianapolis at the western flank.
Because the Earth is a sphere and rotates from west to east, the setting of a particular celestial object will be seen to set at a particular moment from Eastport, but that same object will not set for Indianapolis until about an hour has passed; it will take that long for the Earth's rotation to turn enough to bring that celestial object down to the western horizon as seen from Indiana.
And yet for both locations, the clock reads the same because they are both in the same time zone! As a consequence, this week, Venus will set from Eastport at 11:22 p.m. EDT. But for Indianapolis, Venus will not set until 12:22 a.m. EDT.
Venus will continue to stay up late for a while longer to offer a spring skywatching treat, but after this week it slowly begin to set earlier and this will really begin to accelerate after May 15, when it becomes stationary against the background stars and begins turning directly back to the west toward the sun. By then, if you watch for it at dusk it will appear noticeably lower with each passing evening.
But the close to this great evening show will come on June 5 when Venus passes across the face of the sun — an exceedingly rare event astronomers call a transit. The Venus transit of 2012 is the last of its kind until 2117. More on this in the coming weeks, so stay tuned!
If you snap an amazing photo Venus or any other skywatching target and you'd like to share it for a possible story or image gallery, please contact managing editor Tariq Malik at email@example.com.
Joe Rao serves as an instructor and guest lecturer at New York's Hayden Planetarium. He writes about astronomy for The New York Times and other publications, and he is also an on-camera meteorologist for News 12 Westchester, N.Y.