There’s a minor traffic jam in the sky Friday morning (June 12). The last quarter moon will shine less that a fist (about 8°) to the right of bright Mars at the same time Mars passes just 1.75° south of Neptune. If you haven’t been up at dawn in a while Mars has really brightened up. Now at magnitude –0.2 it’s brighter than Saturn and only bested by Jupiter.
If you’re out a little earlier when the sky is still dark you can use a pair of 50mm binoculars or a small telescope to easily find the planet Neptune. It’s in conjunction with Mars tomorrow when the tiny Red Planet slides just a few moon diameters below the distant giant. Point your binoculars at Mars, and Neptune will already be in your field of view. The map will help you pick it out starting Friday morning, June 12 through Tuesday, June 16. Color-wise, these two lie at either end of the rainbow. Neptune appears pale blue because methane in its atmosphere absorbs red light and reflects back blue. Mars looks reddish-orange because of iron oxide (rust) in its soil.
They also lie at vastly different distances: 88 million miles (1.4 million km) for Mars vs. Neptune’s 2.8 billion miles (4.5 billion km). For that reason Neptune appears so much fainter despite being seven times larger and much more reflective.
Mars will be closest to the Earth in early October and shine as brightly as Jupiter, but you don’t have to wait until then to start observing it in a telescope. Begin now. I know the hour is early which means you’ll lose a little little sleep but if you get to know the planet now, when it’s still on the small side, you’ll train your eye for the time when Mars is big and close and see that much more. Teasing out of delicate details from a quavering image of a small planet like Mars is a great skill and takes time to learn. The more you look the more you’ll see.
I looked at Mars in my 10-inch telescope a week ago and got my first clear view of the planet’s South Polar Cap at around 150x. It’s one of my favorite sights because it looks so earth-like. Earths’ cap is composed of water ice while the Martian cap is primarily frozen carbon dioxide (dry ice). North of the cap I made out several vague dark markings created by wind-blown dust. Some of them mark the locations of ancient volcanoes. As Mars and Earth move closer, I’ll provide maps and a more detailed guide to identify these and other features.
I start at low magnification and then crank it up until the image looks too shaky or blurry. This is caused by the turbulence in the atmosphere. Then I back it down. 76x is my low power while around 350x is high. I usually observe Mars between 150x and 250x for the best views. A 6-inch telescope magnifying around 100x or 150x should show the cap right now as long as turbulence isn’t too bad. The key is keep observing until the image settles down and sharpens up. That may only happen now and then so you must be ready to take full advantage of those calm spells.
Besides the polar cap the thing you’ll most likely to notice is Mars’s shape. It’s not circular! Not even close. Instead it shows a phase.
In June Mars looks like an 85-percent-illuminated waning gibbous moon. My eyes see a pink Easter egg with a dab of white (polar cap) on top. Mars reached western quadrature on June 7 when it was exactly 90° from the sun in the sky. On that date Mars stood due south at sunrise. Next February 1st the planet will lie 90° east of the sun and stand due south at sunset at eastern quadrature.
Mars’s phase is very noticeable around quadrature (75x will show it) because we’re looking at the planet almost from the side. Our viewing angle from Earth (see diagram above) encompasses much of the sunlit hemisphere as well as a portion of the night-side, too. That’s why the planet looks like a gibbous instead of full. Not until the time of opposition, when Mars is directly lined up with the sun, does it face the sun directly (from our perspective) and appear fully illuminated and circular — a Full Mars!
However you enjoy the sight of Mars, whether paired with Neptune in binoculars, or spotting the polar cap (before much of it vaporizes later this summer) and weird phase in your telescope, the important thing is to spend time outside enjoying the natural world. For more about the Red Planet’s upcoming close opposition see this excellent primer.