As if you needed an excuse to look up at the night sky, this
Sunday (June 23) the full moon will seem especially big and bright. It will be
most striking when it’s near the horizon.
What causes a Supermoon?
The Moon is an elliptical orbit around the Earth, meaning
that its distance from the Earth can vary from a minimum of 357,000 km to a
maximum of 407,000 km. The average perigee and apogee are 363,300 km and
405,500 km, respectively, and the variation over the course of the year is due
to the Sun's gravitational influence as the Earth and Moon move along their
orbit throughout the year. The coincidence of a full moon and the perigee
(closest distance) is what dictates a Supermoon, which is what will occur on
Sunday.
What to expect:
On Sunday the Moon will be at true perigee at 7:32am, and
will be visible at sunset that evening. The Moon will appear to be about 7%
bigger than an average full moon (14% bigger than when the Moon is at apogee). The
effect will be most noticeable when the Moon is rising/setting as objects on
the horizon lend scale to the night sky.
It should be beautiful if the clouds permit :-)
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Tonight's moon (from my point and shoot camera) is already looking very big an bright!
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For more information about the Moon, this Sunday’s
supermoon, and the Moon Illusion, read out this article from Sky and Telescope's
Blog:
