The upcoming supermoon will be completing a trifecta of moons presenting it larger and brighter than all regular full moons.
Thanks to the closest approach to the Earth on its elliptical orbit, the lunar disk will appear as largest. December will be the third consecutive month when the moon appears as a "supermoon."
A webcast featuring live views of the supermoon will be online from Virtual Telescope Project at 11 a.m. EST (1600 GMT) on Dec. 13.
Peak fullness of the moon will be reached at 7:05 p.m. EST on Dec 13, Tuesday, according to experts. The beauty of supermoon will be the perigee-syzygy of the Earth-moon-sun system making the moon appear brighter and larger than a normal full moon.
Mark The Time
The full moon is said to reach its closest point to Earth at 222,738 miles at 1:25 p.m. Eastern Time (ET) (18:27 UTC on Dec. 12 and reach the full phase at 2:06 p.m. ET (19:06 UTC) on Dec. 13.
The supermoon will be clashing with the Geminid meteor shower that will peak around 2 a.m. With supermoon out all night, it is likely that Geminids shower that produces an average 120 meteors per hour will be subdued by "five to ten-fold, according to NASA.
However, the upcoming meteor "Ursids Peaking" of Thursday, Dec. 22 may compensate that loss as it produces five to 10 meteors in an hour. Ursids is a fall out of the dust grains left by the comet Tuttle.
One more thing to expect on the supermoon is the arrival of red giant star Aldebaran of Taurus constellation that will be visible to binoculars and telescopes.
Aldebaran, however, will also be briefly eclipsed by the moon at 11:13 p.m. ET (4:05 UTC) and can be seen by skywatchers of North America and Western Europe.
Bigger, Brighter Moon
The last supermoon that took place in the middle of November was deemed the biggest in 70 years, as it was the first time a completely full moon had come closer to Earth since 1948.
The supermoon is caused by the elliptical nature of moon's orbit of which one side is about 30,000 miles (50,000 km) closer to Earth (perigee) compared to the other side (apogee).
Syzygy is the phase when the Earth, the sun, and moon line up when the moon orbits Earth. During the perigee-syzygy of the Earth-moon-sun system, supermoon follows as soon as the moon comes on the opposite side of the Earth from the sun.
In terms of appearance, supermoon or perigee full moon will look 14 percent bigger and 30 percent brighter than an apogee full moon. The next supermoon is expected in 2034.
The Royal Observatory Greenwich said the moon will "appear full to the casual observer" the night before and after the main event.
Astronomy expert Daniel Brown of Nottingham Trent University has advised that looking out for the supermoon will be best when it is low in the sky just after sunset or before sunrise.