Cool Star Lab Alumna Jackie Faherty Talks Supermoon on NPR

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Cool Star Lab alumna Dr. Jackie Faherty, now a Senior Scientist at the American Museum of Natural History, spoke to NPR today about tonight’s “Supermoon” phenomenon.

The Moon’s orbit is an ellipse with an average eccentricity of 0.05, and therefore varies between 363,000 km (perigee) and 405,000 km (apogee) from Earth.  When the Moon is close to perigee at Full Moon (a “perigee syzygy”), it can appear 10% wider and thus 22% brighter than a Full Moon near apogee.

Image of the full moon from NASA

However, the gravitational tugs of the Sun, Jupiter and Venus actually perturb the orbit of the Moon enough to drive the eccentricity to a range of values, typically between 0.026 and 0.077.  So tonight’s Moon is just a little bit closer (357,000 km), and is estimated to be about 30% brighter than an apogee Full Moon. This makes it the brightest supermoon since 1948, and the next closer one won’t be until 2034.

You can hear more details about the Supermoon from Jackie’s NPR segment at http://n.pr/2eV1omg.