Tonight – July 6, 2017 – the very bright waxing gibbous moon will erase many stars from the slate of night. Will you see the planet Saturn just south of tonight’s moon? 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 farther from the moon’s glare. Follow the links below to find out more about the two celestial lights that are in the moon’s vicinity on July 6, 2017.
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 9.1 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 2017, as they are inclined at nearly 27o 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.
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.
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!
Bottom line: Look at the moon on July 6, 2017, and you’ll likely notice two nearby objects. The closer object to tonight’s moon is the planet Saturn, and the other is the star Antares.
Bruce McClure has served as lead writer for EarthSky's popular Tonight pages since 2004. He's a sundial aficionado, whose love for the heavens has taken him to Lake Titicaca in Bolivia and sailing in the North Atlantic, where he earned his celestial navigation certificate through the School of Ocean Sailing and Navigation. He also writes and hosts public astronomy programs and planetarium programs in and around his home in upstate New York.