February 19, 2019

AstroEvent(s): A Conjunction, a Perihelion, a Meteor Shower & an Eclipse…

2011 is here; let the astronomy events begin! And a what a busy first week of January it is; right out the gate, we have no less than four significant events to talk about;

January 2nd sees a close conjunction of the planets Jupiter and Uranus, both well placed to the south for northern hemisphere observers after dusk. This is the last of a series of three apparent passes made by the two worlds over the past few years; at their closest, Uranus will be 31’ minutes north of Jupiter at about 14:00 UT and both will fit well into a low power field.

Next up, the Earth will reach perihelion, or its closest point to the Sun on January 3rd at about 19:00 UT/or 14:00 EST. We’re about 5 million km closer to the Sun now than at aphelion in July; can you feel it? Unfortunately, much misinformation in the form of Woo has already permeated the Internet about the perihelion, “alignment of Sirius”(!) and a certain other event to follow…

But first, another unique event is in the offing; the Quadrantids, everyone’s favorite meteor shower named after an obsolete and defunct constellation, peaks the morning of January 4th. An exact maximum zenithal hourly rate of 120 is predicted for 1:00 UT, which would favor eastern European to middle Asian longitudes. Still, the peak can arrive early or late, and mornings surrounding this date are worth watching from all longitudes. Another reason for this cold winter vigil is the fact that this particular meteor shower occurs on the same day as the New Moon, one of the very few good meteor showers in 2011 to not suffer from lunar interference.

Finally, a partial solar eclipse occurs on the 4th, visible from Northern Africa, Europe and the Middle East. Viewers will see a maximum of 86% of the Sun covered by the Moon. Interestingly, viewers across Western & Northern Europe will have a shot at a rising partial eclipse, an excellent photo op! In fact, the shadow of the Moon misses the Earth by a scant 510 km, approaching the view of polar orbiting satellites in Low Earth Orbit!

The astro-word for this week is Gamma. When describing a solar eclipse, the gamma refers to the centrality of the eclipse; think of the radius of the Earth constituting a value of 1.0, and the gamma being the fraction of the radius described from the path of the umbra along the Earth’s surface to the center point as viewed from the Moon. Along the center of the path, the eclipse will be central and total; areas beyond the path will experience a partial eclipse. The gamma must be below a value of 0.9972 for a total eclipse to occur on the surface of the Earth; the threshold value is not exactly 1.0 due to the oblate shape of our planet. Note that this month’s partial has a gamma of 1.0626, just missing touch down on the surface of the Earth!

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