What Causes a Super Blood Moon?

RED MOON LIVE AT 4:17 GMT ALBUFEIRA MARINA 28 SEPTEMBER 2015.
CARLOS SOUSA | UNITED PHOTO PRESS

A rare astronomical phenomenon Sunday night will produce a moon that will appear slightly bigger than usual and have a reddish hue, an event known as a super blood moon.

It’s a combination of curiosities that hasn’t happened since 1982, and won’t happen again until 2033. A so-called supermoon, which occurs when the moon is closest to earth in its orbit, will coincide with a lunar eclipse, leaving the moon in Earth’s shadow. Individually, the two phenomena are not uncommon, but they do not align often.

Most people are unlikely to detect the larger size of the supermoon. It may appear 14 percent larger and 30 percent brighter, but the difference is subtle to the plain eye. But the reddish tint from the lunar eclipse is likely to be visible throughout much of North America, especially on the East Coast.

“You’re basically seeing all of the sunrises and sunsets across the world, all at once, being reflected off the surface of the moon,” said Dr. Sarah Noble, a program scientist at NASA.Continue reading the main storyNASA | Supermoon Lunar Eclipse Video by NASA Goddard

United Photo Press photographer Carlos Sousa depart from
Albufeira Marina at sailing boat, to catch the best moon.

Stargazers are excited. Though the celestial show will be visible by simply looking toward the sky, the Intrepid Museum in New York will host a free viewing from its perch at Pier 86 on the Hudson River with astronomers and high-powered telescopes on hand. The Amateur Astronomers Association of New York will be holding several free events in the city,including at the High Line, offering telescopes and binoculars for better views.

“People can ask questions, and we can answer the questions right there,” said Marcelo Cabrera, the club’s president.

The eclipse will begin at 9:07 p.m. Eastern time, as the Earth’s shadow moves across the moon, according to the association. At 10:11 p.m., the entire moon should be in the Earth’s shadow, at which point it will adopt the reddish color. It will remain fully in the shadow until 11:23 p.m., and the eclipse will end at 12:27 a.m.

If time or attention spans run short, Mr. Cabrera suggested looking up just before the moon descends fully into the Earth’s shadow at 10:11 p.m., as it turns color.

Dr. Noble said such events tend to get more people interested in astronomy, as it creates an opportunity to take children outside and get them looking up at the sky. “It leads to conversations about what else is up there,” she said.