The longest total lunar eclipse of the 21st century takes place this Friday, July 27. The total phase of the “blood moon” eclipse of July 27 will last one hour and 43 minutes, during which Earth's natural satellite will turn a spectacular red or ruddy-brown color. From start to finish, the entire celestial event will last nearly 4 hours.
The eclipse won't be visible to viewers in North America, except via webcasts. But observers in much of Africa, the Middle East, southern Asia and the Indian Ocean region will get an eyeful, given cooperative weather, according to lunar scientist Noah Petro, of NASA's Goddard Space Flight Center in Greenbelt, Maryland.
July's total lunar eclipse occurs on the same day the planet Mars reaches its opposition, when it will shine at its best in the night sky. This month, Mars will be at its closest to Earth since 2003.
After opposition, when Mars will be brightest, it will reach that closest point on July 31.
Unlike with solar eclipses, no special equipment is needed to observe lunar eclipses. These latter events, which occur when the moon passes into Earth's shadow, are safe to view directly with the naked eye, telescopes or binoculars.
The moon turns deep red or reddish brown during eclipses, instead of going completely dark. That's because some of the sunlight going through Earth's atmosphere is bent around the edge of our planet and falls onto the moon's surface. Earth's air also scatters more shorter-wavelength light (in colors such as green or blue); what's left is the longer-wavelength, redder end of the spectrum.
The entire eclipse will be visible from Africa, the Middle East and countries in central Asia. The eclipse will be visible from eastern South America as it is ending, and from Australia as it is beginning.
The time of greatest eclipse will be 2021 GMT on July 27. The total eclipse will last from 19:30 to 21:13 GMT. There will also be some time before and after when the moon is in the lighter part of Earth's shadow, which is called the penumbra. Including that penumbral time, the eclipse will last for 3 hours and 55 minutes.