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What Makes a Supermoon?

Even invisible, it tugs our tides mightily

Look for the waning crescent moon in the southeast before dawn Friday. Golden Saturn is just a couple degrees above, while fiery Antares is less than 10 degrees below. The trio rises around 4am, and by 6am they are well placed above the southeast horizon.
    Tuesday marks new moon — the first of January’s two Supermoons. What? How can new moon be a Supermoon? The criteria for the relatively new term Supermoon isn’t that we can see it, but rather that the moon, sun and earth are all three aligned in conjunction with the moon’s closest point to earth in its monthly orbit, called perigee. This can happen during both full moon and new moon. There will be six Supermoons in 2015, with January, February and March coinciding with new moon and July, August and September with full moon.
    New or full, a Supermoon can create super tides. The alignment of earth, sun and moon at new and full moon creates a gravitational tug resulting in strong spring tides. High tide is higher than normal, and low tide is lower. A Supermoon’s closer proximity to earth adds to the pull, creating even greater swings in what are called perigean spring tides.
    Look for the nascent crescent moon to reappear low in the west just after sunset Wednesday, with Venus just a few degrees to the moon’s left and Mercury between the moon and the horizon.
    Mercury and Venus were one degree apart last week, but now the innermost planet is sinking back toward the western horizon and the glare of the sun. They are still within three degrees of one another Friday, but by Wednesday the gap will have grown to almost 10 degrees.
    Mars is above and to the left of Venus and Mercury at sunset, visible until 8pm. Monday the red planet appears within 15 arc minutes — one-quarter degree — of distant Neptune in a rare planetary conjunction. At magnitude 8, Neptune demands binoculars or better yet a telescope. Start at Mars and scan above and to the left.
    Keep the binoculars handy, and look for Comet Lovejoy Saturday eight degrees west-southwest of the Pleiades star cluster, high overhead above Taurus the bull after dark.