Enjoying EarthSky? Subscribe.

115,459 subscribers and counting ...

Moon near Saturn, heading toward star Antares on June 10

Moon near Saturn, heading toward star Antares on June 10 Read more

Tonight for June 10, 2014

The bright waxing gibbous moon shines quite close to the planet Saturn, and above the star Antares, as darkness falls on June 10, 2014. How close the moon and Saturn appear together depends on where you live worldwide. In Europe and Asia, the moon will appear closer to Saturn than it does in North America.

However, no matter where you are on Earth, at least one thing remains constant. The moon always moves eastward relative to the backdrop stars and planets. As we speak, the moon is creeping closer to Antares, the brightest star in the constellation Scorpius. The moon moves about one-half degree closer to Antares every hour. For reference, the diameter of the moon equals about one-half degree.

The diameter of the moon is some 2160 miles (3476 kilometers) wide. Since we know the moon more or less travels its own diameter every hour, we can assume that the moon revolves around Earth at somewhere close to 2160 miles (3476 kilometers) per hour.

We can also figure out how fast the moon travels in one minute and one second. Since there are 60 minutes in one hour, the moon must travel approximately 36 miles (58 kilometers) per minute; and since there are 60 seconds in one minute, the moon must travel around 0.6 miles (one kilometer) per second. For ready reference, the moon travels one kilometer per second.

In a period of 24 hours, the moon covers about 52,000 miles (84,000 kilometers). That’s farther than two trips around the Earth’s equator in just one day.

Bottom line: Watch the moon on June 10, near the planet Saturn. Then keep watching, as the moon speeds past the star Antares in the next several days.

A planisphere is virtually indispensable for beginning stargazers. Order your EarthSky planisphere today.

Help support EarthSky! Check out the EarthSky store for fun astronomy gifts and tools for all ages!

What is the ecliptic?