Talk about something happening once in a blue moon — Wednesday night’s lunar event won’t be repeated for another 14 years.
The Aug. 30 moon will be the biggest and brightest full moon of the entire year, a so-called super blue moon. Tonight’s moon is an especially rare one for several reasons:
- It’s a full moon, meaning it’s as close as we get to seeing the sun illuminate the entire side of the moon. This happens once or sometimes twice a month.
- It’s also a blue moon, which means two different things. First, it’s a monthly blue moon, or the second full moon of the month, which is how a blue moon is commonly defined. But it’s also a seasonal blue moon, as NASA notes, meaning it’s the third full moon in an astronomical season that has four full moons. But despite the colorful name, the moon itself will not appear blue.
- Finally, this also a supermoon, meaning the moon appears larger — about 14% larger, according to NASA — and brighter than usual, even to the naked eye. This is because its orbit is at its closest point to the Earth — a moment known as its perigee, when the moon is just 226,000 miles from us — at the same time that the moon is full.
Supermoons are slightly more common than blue moons, NASA says. While about 25% of all full moons are supermoons, just 3% of full moons are blue moons. That’s why the phrase “once in a blue moon” is used to describe a rare event. And the length of time between super blue moons is even more irregular. On average it’s 10 years, according to NASA, but it sometimes stretches as long as 20 years. After tonight, we won’t see another until we get a pair of super blue moons in January and March 2037.
Tonight’s super blue moon, NASA adds, also coincides with the Hindu Raksha Bandhan festival, also known as Rakhi or Rakhi Purnima, which celebrates the bond between brothers and sisters. And it falls near the middle of the month for many lunisolar and lunar calendars, such as the Chinese, Islamic and Hebrew calendars, which carries some spiritual significance. It comes during Elul in the Hebrew calendar, for example, which is a time of preparation for the High Holy Days of Rosh Hashanah and Yom Kippur.
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Now that you know what the super blue moon is, how can you catch it?
The super blue moon will be officially full at 9:36 p.m. Eastern time on Wednesday, Aug. 30. That is when the moon will be 180 degrees from the sun, or completely opposite the sun in the sky over the Earth, Space.com explains.
The super blue moon will set on Thursday morning just before the sun rises at around 6:46 a.m. Eastern.
If you want to catch the moon looking especially huge, it’s recommended that you catch the moon either rising in the east in the evening or setting in the west in the early morning. This is because when the moon is nearest to the horizon, a “moon illusion” makes it seem bigger. Photographers can exaggerate this illusion by taking pictures of the moon low on the horizon, using a long lens and having buildings, mountains or trees in the frame, NASA says. If you’re angling for that perfect shot, you can find the rising and setting times for your area using the U.S. Navy’s moonrise calendar.
If the sky is overcast in your area or buildings or other obstacles block your view, you can catch the action online instead. The Virtual Telescope Project will be providing a free livestream of the super blue moon rising over Rome beginning at 11:30 p.m. Eastern on Aug. 30.
In other lunar news, India became the fourth country to successfully land a spacecraft on the moon last week. You can watch the Indian rover explore the moon’s south pole here.