Full Moon Friday: What You Can See

Talk to most astronomers, and you?ll find that they have a thing about the full moon. The reason is that a full moon is the No. 1 cause of natural light pollution. Its brilliant light floods the night sky, dimming all the stars and nebulae, causing astronomers to pack away their telescopes and watch television instead.

However, to dedicated skywatchers like us, the moon has its own fascination, especially when it is full, as it will be Friday, Sept. 4. After all, this is the only object in the solar system on which we can see a wealth of detail without any optical aid whatsoever.

The full moon is particularly appealing at this time of year when it rises just around sunset and hovers low in the southern sky most of the night.

The first thing to look for is the man in the moon, or perhaps you can more easily see the woman in the moon or even the rabbit in the moon. One way or another, you can probably see a pattern of some sort in the play of bright and dark markings across the moon?s face. The darker areas are known as maria (singular mare, Latin for sea), though they have never seen a drop of water in the last four billion years. The lighter areas are mostly cratered highlands, where relatively recent asteroids have crashed into the moon?s surface, exposing bright rock beneath the surface.

The largest dark area on the moon, on the left side, is actually called an ?ocean?: the Oceanus Procellarum or Ocean of Storms. Just above it, and almost as large, is the Mare Imbrium or Sea of Showers. Opposite Imbrium on the right side of the moon is a triangle of three smaller ?seas?: the Mare Serenitatis (Sea of Serenity), Mare Tranquillitatis (Sea of Tranquility) and Mare Crisium (Sea of Crises).

Although there are smaller seas, most of the rest of the moon?s near side is highlands, covered with hundreds of craters. By far the most prominent of these is Tycho, named for Tycho Brahe, the greatest astronomer of the sixteenth century. This crater is brilliantly white, and is the source of a huge system of rays: bright linear features which encircle the globe of the moon. The Tycho ray system, along with several smaller ray systems, are best seen when the moon is full.

There is a whole set of traditional names for the various full moons throughout the year. The most famous of these ?named? full moons is the harvest moon. Seeing the beautiful big moon rising in the east this week, many people will think it is the harvest moon, but it isn?t. Although the harvest moon usually falls in September, this year is different. Harvest moon is defined as the full moon closest to the fall equinox.

This year the fall equinox occurs on Sept. 22, and the nearest full moon to that date is on October 4. So this full moon on Sept. 4 is properly known as the ?fruit moon? or ?full fruit moon? since it signifies the ripening of fruit.

• Skywatcher's Guide to the Moon
• More Night Sky Features from Starry Night Education
• Moon Image Gallery

This article was provided to SPACE.com by Starry Night Education, the leader in space science curriculum solutions.