Enjoying EarthSky? Subscribe.

231,360 subscribers and counting ...

Moon, Saturn, Antares on July 15

Tonight – July 15, 2016 – the very bright waxing gibbous moon will erase many stars from the slate of night. Will you see the planet Saturn in the moon’s glare? Probably, if you look, and if clouds don’t hide them. If not, try covering the moon with your finger to gaze at nearby Saturn. Although the supergiant red star Antares is not as bright as Saturn, it might be easier to see since it’s a little farther from the moon’s glare. Follow the links below to find out more about the two celestial lights that are closest to the moon on July 15, 2016.

Ringed planet Saturn

Supergiant star Antares

 Watch for the moon to swing close to Mars on July 14 and then Saturn on July 15. Read more.

Watch for the moon to swing close to Saturn and Antares on July 15, and then again on July 16.

Zefri Besar - in Brunei, on island of Borneo - caught moon, Mars, Saturn and Antares on the night of July 15, 2016. Thanks, Zefri!

Zefri Besar – in Brunei, on island of Borneo – caught moon, Mars, Saturn and Antares on the night of July 15, 2016. Thanks, Zefri!

The brightness of Saturn at opposition is partly determined by the orientation of its rings with respect to Earth. In 2016, the rings are wide open, tilted by 26-26.8 degrees, showing their northern face to Earth. Image via Hubble Heritage.

The brightness of Saturn in Earth’s sky is partly determined by the orientation of its rings with respect to Earth. In 2016, the rings are wide open, tilted by 26-26.8 degrees, showing their northern face to Earth. Image via Hubble Heritage.

Saturn, sixth planet out from the sun, is the farthest world you can easily see with your unaided eye. It’s 10 Astronomical Units from the sun (10 times the Earth-sun distance), and, right now, it’s about 9.3 Astronomical Units from Earth. One Astronomical Unit equals about 93 million miles (150 million km).

Saturn is often called the jewel of the solar system because of its gorgeous ring system. Saturn’s rings are enormously expansive and wide, but extremely thin. The main rings extend nearly as far the moon’s distance from Earth, yet are only about one kilometer thick. With even a modest telescope, you should be able to see Saturn’s rings easily in July 2016, as they are inclined at 26o from edge-on.

Saturn, the second-largest planet after Jupiter, has a diameter that’s a good 9 times greater than Earth’s. Like Jupiter, Saturn is a gas giant world, composed of mainly hydrogen and helium.

Unlike the inner rocky planets – Mercury, Venus, Earth and Mars – Saturn and Jupiter have no solid surfaces on which to stand.

Mars, Saturn, Antares and fireflies! From Matt Pollock on May 29, 2016, in upstate New York.

Mars, Saturn, Antares (here with fireflies!) have been near each other on our sky’s dome for months. Photo by Matt Pollock – May 29, 2016 – in upstate New York.

Antares is the brightest star in the constellation Scorpius the Scorpion. It is a red supergiant star. In fact, this star dwarfs the sun to almost nothingness. While the volume of the sun is approximately 1.3 million times that of our planet Earth, Antares has the volume of hundreds of millions of suns. If by some bit of magic Antares were suddenly substituted for our sun, the surface of the star would extend well past the orbit of Mars!

Antares is classified as an M1 supergiant star. The M1 designation says that Antares is reddish in color and cooler than many other stars. Its surface temperature of 3500 kelvins (about 5800 degrees F.) is in contrast to about 10,000 degrees F. for our sun.

Even though Antares’ surface temperature is relatively low, Antares’ tremendous surface area – the surface from which light can escape – makes this star very bright. In fact, Antares approaches 11,000 times the brilliance of our puny sun, a G2 star.

Stellar luminosity: The true brightnesses of stars

But that is just in visible light. When all wavelengths of electromagnetic radiation is considered, Antares pumps out more than 60,000 times the energy of our sun!

Red star Antares, right, and nearby star cluster M4 via StargazerBob.com@aol.com

Red star Antares, right, and nearby star cluster M4 via StargazerBob.com@aol.com

Bottom line: Look at the moon on July 15, 2016, and you’ll likely notice two nearby objects. One is the planet Saturn, and the other is the star Antares.

Help support posts like these at the EarthSky store. Fun astronomy gifts and tools for all ages!

Bruce McClure

MORE ARTICLES