Four of the planets in our solar system are visible in the early morning light — Venus, Mercury, Neptune and Uranus. Venus is easy to spot, but the others can be more challenging, particularly Neptune and Uranus.

OK, it's time for an astronomical challenge for you and it's waiting for you in the early morning Pennsylvania sky. The initial challenge is to get you out of the sack early enough in the morning, say around 5:30 a.m.

Grab your coffee, binoculars and your best carrot-fed eyesight and you may see four planets of the solar system; the two closest to the sun and two of the farthest from our home star.

In one shot you can see Mercury, Venus, Uranus and Neptune waking up in the southeastern sky in nearly a straight line not more than about three fist-widths at arm's length. Let the challenge begin!

OK, we'll start out easy with the planet Venus. It's by far the easiest of the planetary gang of four to see and in fact it's the brightest star-like object in the sky. Just look for that bright light in the low southeast sky in the pre-dawn sky. At first you may think it's an airline coming in for a landing.

Now normally planets don't twinkle but Venus might be simply because it'll be low in the sky and its light will have to cut through a lot of our turbulent atmosphere. As with all these planets there really isn't much more you can see with binoculars or a telescope.

Venus is heavily shrouded with a thick, poisonous and highly reflective atmosphere and bounces a lot of sunlight our way. However, since Venus' orbit around the sun lies inside the Earth's orbit, and since Venus is at a right angle between us and the sun, all we see is half of Venus.

Now the challenge really begins! The next planet you should attempt to find is Mercury, the second brightest of the planetary gang of four. It's not going to be easy since it'll be just barely above the horizon. Be sure you look for it with a low flat horizon. Clench your fist at arm's length and look just shy of two fist-widths at arm's length to the lower left of Venus. It'll be much fainter than Venus but it is seeable.

Now the challenge really gets tough. The planet Uranus is usually mission impossible to find but, because you can use Venus as a starting point, it's not impossible. It'll be about halfway between Venus and Mercury or about one fist-width to the lower left of Venus.

If it's really dark where you are, you may see it with the naked eye — but you'll probably need binoculars. Since it's close to the horizon it'll probably have an orange-ish hue to it but you may see a little bit of its true greenish-blueish hue.

Uranus wasn't always the name of this planet. It used to be called George. Sir William Herschel, the flameout English astronomer who discovered the seventh planet out from the sun in 1781, named the new planet after King George III. The name Herschel assigned to it stuck around for a little while but other astronomers eventually got together and gave it a traditional Greek mythology name, Uranus, the god of the sky.

Now the ultimate challenge for you, the planet Neptune, the eighth planet from the sun, and presently more than 2.8 billion miles from Earth.

Forget about seeing this with the naked eye. You need a telescope and a lot of luck to see this one. Neptune is just short of a fist-width and half (at arm's length) to the upper right of Venus. It'll also have an orange predawn tint but it may show a little bit of its bluish green color.

There it is — your astronomical challenge. It's not too often that four planets are in such close proximity in the sky with a chance to find outer planets like Uranus and Neptune. But even if you just find Venus and Mercury, that's pretty good planet hunting. But if you can go four for four, you've got a great set of eyes and lot of patience.