The first of August’s two full moons occurred on August 1st as a preview for a so-called “blue moon” rising on Aug. 31. The next time we see two full moons in a single month will be July 2015.

High levels of dust or ash in the atmosphere can make the moon take on various hues, like the orange “harvest” Moon, but “blue” moons aren’t named for their color– they usually look like any other full moon in the sky. Astronomers refer to the second full moon in a single month as a “blue moon.”

The term “once in a blue moon” has long been used to denote rare occurrences, as blue moons appear on average once every 2.7 years.

The existence of blue moons is a result of the fact that lunar months don’t exactly match our calendar months.

It takes 29.5 days for the moon to travel around the Earth, during which time we see the satellite go through all of its phases. But all calendar months (except for February) have 30 or 31 days, so it’s possible to squeeze two full moons into a month every now and again.

Here’s a lunar fact for you: in 1999 sky watchers saw two blue moons in the span of just three months!

NLSI Associate Director Doris Daou clearly explains the Phases of the Moon in this ‘Ask an Astronomer’ episode.

Posted by: Soderman/NLSI Staff

Share →

SSERVI Science Teams

  • NLSI’s LUNAR team tests Kapton film for radio telescopes


    The Dark Ages Lunar Interferometer (DALI) with polyimide foil and embedded low frequency dipoles will study the early Universe.NLSI’s LUNAR team is testing of a piece of Kapton film at the University of Colorado at Boulder under a vacuum of about 10^-7 torr. The objective of this month long test is to simulate the lunar conditions that the Kapton film will experience during a year on the moon. The vacuum chamber will be cycled between -150 and 100 degrees Celscius with each hot or cold cycle lasting 24 hours.

Inspiration Room

NLSI Inspiration Room

Did you know?

The moon is not round, but slightly egg shaped with the large end pointed towards earth.

Read More