“The phenomena of nature, especially those that fall under the inspection of the astronomer, are to be viewed, not only with the usual attention to facts as they occur, but with the eye of reason and experience.” -William Herschel

We live in the most plentiful of scientific times, where the full extent of both our experience and understanding has expanded tremendously since the time of Herschel. You must remember that to Herschel, living in the 18^th century, there were but six known planets (including Earth) in the Solar System: Mercury through Saturn.

Image credit: Daniel Dendy.

While each of these classical, wandering objects can easily be seen with the naked eye under the right conditions, the seventh planet, Uranus, was not discovered until 1781, by William Herschel himself. Under the right dark sky conditions, Uranus is just barely visible to the naked eye, right at the limit of human vision. Unless you know where to look at any given time, it’s very unlikely you’ll see it.

But if you take a look at the sky just after sunset, tonight, you’ll be in for a remarkable treat. Particularly if you live in the Americas.

Image credit: Stellarium.

As you may have noticed, looking towards the southwest portion of the sky just after sunset, there are two very bright objects hovering above the horizon. Venus, the brightest object (other than the Moon) in the night sky, follows the Sun into the west, while Jupiter (the second brightest) lags behind by a few hours.

Up at my latitude (about 45 degrees North), this is what clear skies will look like around 6:00 PM. But wait just a bit longer — maybe a half-hour — and darkness sets in, allowing the light from those distant orbs in the night sky to dominate.

To your naked eye, Venus will still shine more brightly than any other object. It will be a few hours before the Moon comes up and a few hours before Venus falls down below the horizon. But coming closer to Venus than any other time this year is the planet Uranus, and those of you in the Americas will get to see it near its closest approach, right around 7:00 PM Pacific time.

Have a pair of binoculars languishing somewhere at home? Break them out, and point it towards Venus. If you let your eyes get adapted to the dark, even if you have relatively urban skies, here’s what you’re likely to see.

In addition to the bright disk of Venus, you’re likely to see a small point of light a small distance away from it. While it may appear to be a faint star or a small moon, it’s neither. Venus has no moons of its own, and there are no stars anywhere near that magnitude in this region of the sky. What you’re seeing, billions of miles away, is the planet Uranus!

Image credit: Bob King, retrieved from Astro Bob.

The bright, consistent disk of the planets make this a sight visible to many even in light-polluted regions. Unlike looking for a galaxy, nebula, or other extended object, everyone should give this a try. And for those of you with even a small telescope, you are in for a treat. Normally, Uranus is very difficult to find. But tonight, it will be separated from Venus by less than the angular size of the Full Moon! If you can find Venus in your telescope, you’re not only likely to find Uranus, too, but to see that it is a disc, not just a point!

For a size comparison — how big are these disks relative to the full Moon — I give you this chart, modified from Peter Freiman’s original.

The planet Uranus is a sight that most people never get to see in their lifetimes, but if you’ve got clear skies and you’re in the Americas, don’t miss your chance to hunt for it tonight!

And I should make this clear: this is one night only!!!

Venus moves somewhat rapidly across the sky, at least in astronomical terms. While tonight, it will be separated from Uranus by maybe half the size of the full Moon (around 0.3 degrees), by tomorrow at the same time, it will be more than two full Moons away!

Venus and Uranus' separation, at 6:09 PM on February 10, 2012 from Portland, OR.

This close dance of Venus and Uranus is a rare one, and it’s rarer still that they occur when both planets are in prime viewing location in the early evening.

Tonight: one night only, it’s Venus and Uranus, together in the sky. Don’t miss it!