Two short-lived sky phenomena are on tap in the near future, one taking place only tens of miles above us, the other millions of miles away.
Geminid meteor shower:
Each December we are treated to one of the better meteor showers of the year. The Geminids (so named because they appear to originate from the constellation of Gemini) promise rates as high as one meteor per minute at their peak. They are well situated for early evening viewing, and they come at a time of year when sunset comes very early. Rising at 3 am is not necessary! And this year there will be no moon in the sky to spoil the view. The peak of the shower will be the evening of Sunday, December 13, but there are meteors visible for a week before and after this date.
A few basic reminders are in order. Although meteors belonging to a single shower appear to originate from a specific point called the radiant, you can see them all over the sky. Their apparent paths are a matter of perspective; their paths appear to converge for the same reason parallel railroad tracks appear to converge in the distance.
Although the stuff of meteors (bits of cometary dust and particles generally no bigger than a grain of sand) comes from far away, the incandescent streak that marks their demise is generally between 50 and 75 miles above us. Find a site as far away from artificial lights as you can, lie on a blanket or a reclining lawn chair, and look up. No need for binoculars or a telescope–they are useless for viewing meteors. If you want to look in any particular direction, the radiant will rise above the northeast horizon around 7 pm and gradually move across the southern sky. It reaches its highest point around 2 am, but meteors will be visible all night long.
Happy viewing!
Comet Catalina:
Comets come in two somewhat arbitrary categories: short period ones that complete a single orbit of the sun in less than 200 years, and long period ones that take, well, longer. Comet Catalina falls into the latter category. It comes from a vast region of icy objects far from the sun called the Oort Cloud. Inferred by tracing back the paths of these first-time visitors to the inner solar system but never actually directly observed, the Oort Cloud surrounds the sun in a spherical distribution, with its members not confined to the flat plane occupied by the planets.
Occasionally some gravitational perturbation will start one of these iceballs on a long, slow drop into the sun’s gravity well. With orbital periods in the tens of thousands of years, these are one-time visitors for all practical human purposes. They are pristine in the sense that the volatile materials that are frozen solid in the Oort Cloud have never—or at least seldom–been vaporized by a close passage to the sun, and represent well the primordial composition of these 4.5 billion year old relics.
Comet Catalina (its formal designation is C/2013 US10) is typical of a long period comet in that its orbit is highly inclined to the ecliptic plane in which planets orbit, and retrograde—clockwise from above the north pole as opposed to the counter clockwise orbits of all the planets.
Catalina will require binoculars to see it. Right now it is in the early morning sky close to Venus (the brightest object in the east before sunrise). Here is a finder chart for you.
And here is the comet in all its glory.
The ion tail (blue) points directly away from the sun; the dust tail (yellow) trails behind as its heavier and slower-moving components are pushed away from the comet’s nucleus by the solar wind.
Get those binoculars out!
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