Scientists at the American space agency NASA have predicted that a rare celestial event will take place on September 27. It will be the first time after almost 30 years when a total lunar eclipse will mask the moon for more than an hour.

This rare event occurring on late September 27 will be visible to people in the United States and in much of the world. In this event, the total lunar eclipse will cover a major section of the moon.

Noah Petro, deputy project scientist for the Lunar Reconnaissance Orbiter at NASA's Goddard Space Flight Center in Greenbelt, Maryland, said the orbit of the moon is not a perfect circle and as such, sometimes the moon comes closer to the Earth and other times during its orbit.

“When the moon is farthest away it's known as apogee, and when it's closest it's known as perigee. On Sept. 27, we're going to have a perigee full moon—the closest full moon of the year”, he said.

He said that when at perigee, the moon is about 31,000 miles closer to Earth than at apogee. This makes the moon appear almost 14% larger and 30% brighter in the sky than an apogee full moon.

Petro also said that there is no physical change in the appearance of the moon, but it just appears slightly larger than normal size.

In this total lunar eclipse, earth’s shadow will cover up the moon as the planet will come between the sun and the moon. Lunar eclipses typically occur at least twice a year, and 228 will occur in the 21st century alone.