A variety of night-sky events welcomed the beginning of November, and more are on the way. Dr. Joseph Jones, associate professor of physics at the University of North Georgia, talks about the significance of these events and where and when to observe some of them.
Why was the Nov. 3 solar eclipse classified as a "hybrid"?
A hybrid eclipse occurs when the tip of the moon's umbral shadow (the darkest part of the shadow) does not reach the surface of the Earth at the beginning and end of the eclipse path. In the middle of the eclipse path the umbral shadow reaches the surface of the Earth, and anyone viewing from that spot will see a total eclipse of the sun. Once the path ends however, since the shadow doesn't quite reach Earth's surface, observers will see the angular size of the moon to be slightly smaller than the angular size of the sun. This type of eclipse is called an annular eclipse because observers see a small "annulus" or ring of light surrounding the moon at maximum eclipse.
What is the Leonid meteor shower, and what is the best way to observe it?
A meteor shower occurs when Earth plows through a steam of dust particles shed from a comet or other minor body whose orbital path comes close to crossing Earth's orbital path. These encounters are predicable because Earth passes through the streams at the same spot in its orbit at the same date each year.
The Leonid shower meteoroids are not evenly distributed along the comet orbit and the density of particles is much higher in certain regions along the orbit. This means that every 33 years or so, the Earth potentially can pass through many more dust particles than normal, resulting in very high rates of meteors during the shower. The last time this happened was November 2001, when we counted more than 600 meteors per hour!
Currently the Leonid shower is quite weak, with less than 20 meteors per hour predicted. This year the peak rate for us should occur in the early morning hours of Nov. 17, but there is an almost full moon, which means even fewer meteors are likely to be seen. We host one of NASA's All Sky Fireball Network cameras at the observatory. Check out the link here to see what meteors the cameras have caught going "flash" in the night.
What is Comet ISON, and why is it gaining so much attention?
Comet ISON (C/2012 S1) is a sun-grazing comet that will make its closest approach to the sun on Nov. 28. As it has approached the inner solar system, hopes have faded that this would be the "comet of the century."
It is currently inside the orbit of Venus and falling rapidly towards its encounter with the sun. It is visible through small telescopes in the early morning sky, and my students and I have imaged the coma (head) of the comet with the North Georgia Astronomical Observatory telescope.
Many scenarios are possible as ISON whips around the sun. The comet could be pulled apart by tidal forces from the sun, leading to its destruction, or better, increasing its dust and gas output such that it becomes a much brighter object in the early December morning sky. We'll have ISON updates at our next few Friday public planetarium shows at 8 p.m., at UNG's Coleman Planetarium.