Guardian

A SOMEWHAT rare planetary configuration is taking shape in the western sky, as Venus, Jupiter and Mercury move into close visual proximity.

There’ll be no alignment, as such. But they are all either entering or emerging from conjunction (to be explained later): And will, on the 26th, converge to form a triangle, just above the setting Sun.

But Dr. Tony Phillips, Science@NASA Production Editor, advises that it’s not necessary to wait till the 26th. There’s enough to make observation worth your while, even now- a claim I can corroborate- having gotten a tantalizing glimpse of what I thought was Mercury on the 8th.

I took great pride in this. After all, Mercury is the most mercurial of all the naked eye planets. In fact, I’ve not seen it more than three or four times since I’ve been sky-watching.

That’s because Mercury appears at twilight and early evening, always just above the rooftops: Where evening clouds and air pollution usually render viewing conditions difficult, if not impossible. This is especially true in Port Harcourt, with its perennial cloud flotillas.

What is more, Mercury is the one planet that has truly earned its Roman-invested cognomen, as the mythical Winged Messenger of the gods: It zips around the Sun at 48 km per second, orbiting once every 88 days, and often darts out of view before the horizon becomes clear.

So you can imagine how my ego deflated, when I started checking for the planets visible on May 8th—only to learn that it was Venus I’d seen! Unwilling to accept reality, I consulted Ian Morrison’s Blog (Jodrell Bank Centre for Astrophysics), EarthSky and the Celestial Calendar.

No relief! They all sang the same refrain, the same disappointing dirge: “The Winged Messenger has eluded you again, my friend!”

But a sky-watcher is nothing, if not persistent. So I’ll try again between May 19th and July 1st when, according to Celestial Calendar, Mercury will indeed be visible.

Venus, on its part, is always accommodating- much like the goddess of Brothels and Bedrooms, whose name the Roman’s gave it (save your tennis puns for Serena, not Venus!). It’ll rise higher and higher in the sky and eventually be visible for two and a half hours after dark.

A geological twin to Earth, Venus has a thick gaseous atmosphere (90 times thicker than our planet) that reflects 70 percent of the Sun’s light back into space. This makes it the brightest object in the night sky, after the Moon.

Consequently, you’ll have no trouble spotting Venus. If it is cloudy for a few days, no need to worry. The Accommodating Lady will still be waiting when the sky clears. You can rendezvous with Venus until the year’s end. It will become brighter and more alluring as time passes.

The third member of the trio is Jupiter, the largest of the four gas/ice giants, whose orbits lie outwards of Earth’s. It appears dimmer now than in past months, because this swirling world of hydrogen and helium (a day is just under 10 hours!) is approaching conjunction.

Getting to terminology at last, “conjunction” is one of several configurations (or “aspects”) that describe the orientation of satellites to the Sun, as viewed from Earth. It occurs, when a planet is positioned at a 180 degree angle (a straight line), on either side of the Sun.

There are two types of conjunctions- inferior and superior. The latter occurs when the Sun lies in the middle, while a satellite that is positioned between Earth and the solar sphere is in inferior conjunction. Jupiter is about to round the Sun. So it is going into superior conjunction.

Position-wise, there are also two types of planets- again, they are inferior and superior. Mars, Jupiter, Saturn, Uranus and Neptune are superior planets, because Earth orbits between them and the Sun.

By contrast, Venus and Mercury are inferior satellites because they orbit closer to the Sun than Earth.  But they can also enter superior conjunction, whereas the outer planets cannot. Presently, Venus and Mercury are rising in the sky, after emerging from inferior conjunction.

In case I’ve gotten you tensed up with this technical jargon, Tony Phillips has a suggestion to relieve your tensions. Go out on these dates, he advises, and face the twilight horizon:

May 24th, when Mercury’s approach to Venus gives shape to the triangle, which materializes fully May 26th; and on the 28th, when Venus passes close to Jupiter.

It’s just what the doctor ordered.