Mapping the ecliptic


The ecliptic is formally defined in two different ways: 1) the path of the Sun against the background stars; and 2) the plane generated by Earth’s orbit. The solar system (or at least the system of major planets) is actually rather flat, so the ecliptic can also be called the plane of the solar system and all major planets can be found on or near the ecliptic when they are visible in the sky. On Friday, March 27, 2009 at 9 p.m., Saturn will be about 35° above the east-southeast horizon and just 2° north of the ecliptic.

However, there are objects outside the solar system that can be seen pretty close to the ecliptic plane. Saturn is currently in Leo, the Lion. The brightest star in Leo, Regulus, is an ‘ecliptic star,’ being less than 1° off the ecliptic. Regulus is easy to see as a 1st magnitude star about halfway up the sky from the southeastern horizon, rising about 1 1/2 hours before, and 17° away from, the planet Saturn.

About 20° away from Regulus, and only about 1° off the ecliptic is M44, the Beehive Cluster in Cancer. M44 is a bright, 3rd magnitude, open cluster easily visible on a clear, dark night with the unaided eye, looking like a large cotton ball (better viewed with binoculars). M44 rises about 2 hours before Regulus, and is 2/3 the way up the south-southeast horizon at the designated time.

And if that’s not enough to find the ecliptic, over in the west is M45, the Pleiades, only 3° off the ecliptic. The Pleiades is in Taurus and is an easily visible open cluster often confused with the Little Dipper, because of the distinctive shape of the 6 brightest stars. At the specified time, M45 is about 1/3 the way up from the western horizon.

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2 thoughts on “Mapping the ecliptic

  1. Sorry, no eclipse. A lunar eclipse must coincide with the Full Moon, which was on February 28th, and did not have an eclipse either. There will be a partial lunar eclipse in June and a total lunar eclipse in December.

    Happy Birthday!

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