For the entire week, stargazers are going to be treated to a dusk spectacular: 4 planets and bright star Regulus at dusk. No need for a telescope, just binoculars and a good Western horizon.
The sky at 9:30pm on July 20.
With our sky map set for this week, let’s examine each of our celestial targets.
First up: Mercury, first planet from the Sun. Of all the objects, Mercury (like young/old Moons) will be the tough to spot for several reasons. First, it’s low and requires a excellent horizon. If you live East of Cleveland where the lake is your Western horizon, you are in great shape. Second, Mercury is not overly bright (magnitude -.25) and will be setting just behind the Sun. Those final rays can be a killer. Third, and the variable that will be an unknown until sunset: haze, which is quite insidious on these hot summer days. At any time of the year, but especially now, one can have a crystal-clear day all day and then, come sunset, see a thick, planet-obscuring layer of haze develop on the horizon. Yuck! Because of its placement, Mercury will almost certainly require binoculars (and luck) to spot.
Next: Regulus. Dimmer than Mercury but higher in the sky is blue Regulus, the Little King Star and alpha Leo. Regulus gets its nickname because of the fact that it is the brightest (alpha) star of Leo the Lion, king of the cosmic zoo. Like Mercury, Regulus will require binoculars and a bit of luck as it is still in the haze zone. Another negative is that Regulus, shining at magnitude +1.3, is about 4 times dimmer than Mercury. However, the horizon does not need to be quite as good. Go to the top of a hill or bridge to get a good vantage point. A quick drive out to open country will improve odds, too.
Anchoring the cosmic line up is blazing bright Venus, second planet from the Sun and, at around 900 degrees Fahrenheit, the hottest planet in the solar system. Venus is absolutely impossible to miss, shining away at around magnitude -4, which makes it the third brightest object in the sky behind only the Sun and Moon. Eat that, haze! No binoculars are needed here. However, should you choose to turn your extra set of Mercury/Regulus-hunting eyes on Venus, you may notice that it is not round, but gibbeous in shape, the same as the Moon between half and full. It was Galileo’s observation of the phases of Venus that finally ended the dominance of the Earth-centered geocentric solar system that had been overwhelmingly favored before that.
Next up in line is the fourth planet from the Sun, Mars, also known as the Red Planet. The bad news is that Mars is only about as bright as Regulus. The good news is that it is about 12 degrees higher in the sky: much farther away from the Sun’s final light of the day. Binoculars, by virtue of the planet’s height, may or may not be needed as sky conditions, artificial lighting, and your own eyes, all combine to determine whether you can see something naked eye or not. Even if you don’t need the binoculars, it can be fun to turn them on Mars, anyway. Can you see the red color that gives the planet its name?
Last up on the cosmic itinerary is Saturn, sixth planet from the Sun, the last classical planet, and perhaps the most beautiful of them all. While one needs a telescope to see the rings that make Saturn the celestial splendor that it is, one can probably get away without binoculars, though, as Saturn is about 25 degrees up from the horizon at half an hour past sunset and is slightly brighter than Mars, too. While not much to see without a scope, should you own one, be sure to get a look as Saturn’s rings are, for the moment, almost edge-on. No, the planet is not trying out a new look, but is merely going through a cycle during which the angle of the rings as seen from Earth appears to change. As an interesting piece of trivia, Saturn in the least dense of all the planets. So light is Saturn that, if there were a bathtub big enough, the planet would float!
So there it is, the featured sight for the week. As of now, the weather is looking a bit iffy to say the least. The good news is that Venus, Mars, and Saturn aren’t going anywhere overly fast, but pay attention to them anyway, as these three planets are headed for conjunction in early August. Mercury and Regulus, on the other hand, are rapidly dropping from sight and are headed for a series of close passes from July 26-28. So be sure to catch these two before they say goodbye to the evening sky.
Clear skies to all!