On July 23, 2018, you’ll find the waxing gibbous moon between two objects that look like stars. One is, and one isn’t. The two are the planet Saturn and the star Antares, which is the brightest light in the constellation Scorpius the Scorpion. Will they look to you as they do on our chart at top? Only if you happen to be in the central U.S. From other locations around the globe, you might see the moon closer to Antares, or closer to Saturn. Or you might see the trio oriented differently in the sky. All of us, though, will see Saturn and Antares near the July 23 moon, assuming clear skies.
On either side of this scene – outside the boundaries of our chart – there are two even brighter objects. They are the planets Jupiter and Mars. The moon is in the process moving past Jupiter, then Saturn, then Mars in our sky, as shown on the chart below:
What’s exciting is that the moon is waxing toward a total lunar eclipse – the longest total lunar eclipse of the 21st century – on the night of July 27.
And, meanwhile, Earth is pulling up behind the planet Mars in our smaller, faster orbit around the sun. Remember, Earth is the third planet, and Mars is the fourth. Also on July 27, Earth will catch up to Mars and pass (more or less) between Mars and the sun. Our movement in orbit will bring Mars opposite the sun in our sky, at the place known as opposition to astronomers. Mars will be rising in the east as the sun sets in the west, and it’ll be brighter than it’s been since 2003.
A full moon – the only sort of moon that can undergo a total lunar eclipse – also rises in the east as the sun sets in the west. So, on the night of the eclipse, the moon will be near Mars!
At present, all three planets – Saturn, Mars and Jupiter – shine more brilliantly than a 1st-magnitude star. Mars is brighter than Saturn or Jupiter. Saturn is the faintest of the three planets.
Bottom line: It’s getting exciting up there! We’re headed for a brightest Mars, and a long lunar eclipse, on July 27. Get in the mood by identifying Saturn and red star Antares near tonight’s moon.
Deborah Byrd created the EarthSky radio series in 1991 and founded EarthSky.org in 1994. Today, she serves as Editor-in-Chief of this website. She has won a galaxy of awards from the broadcasting and science communities, including having an asteroid named 3505 Byrd in her honor. A science communicator and educator since 1976, Byrd believes in science as a force for good in the world and a vital tool for the 21st century. "Being an EarthSky editor is like hosting a big global party for cool nature-lovers," she says.