Greetings, stargazers.
The most interesting thing in the sky for me last month was seeing the most intense hailstorm with the largest hail I have seen since moving to Durango over twenty-five years ago. I can assure you that my dogs were not fans of this event.
September is the month with the autumnal equinox, which marks the first day of fall. This year it is on the 22nd.
The changing of the seasons is a good time to remind everyone that one of the biggest misconceptions, even among educated people, is that the reason for the seasons is that the Earth gets closer to the sun in summer, and farther away in winter. This is wrong. The reason for the seasons is the tilt of the axis. Nothing else.
Useful links
Blaze Star
https://en.wikipedia.org/wiki/T_Coronae_Borealis
Astronomy picture of the day
An Astronomer’s forecast for Durango
http://www.cleardarksky.com/c/DrngoCOkey.html?1
Old Fort Lewis Observatory
http://www.fortlewis.edu/observatory
hakes_c@fortlewis.edu
The Earth’s axis, the line going through the Earth from the north pole to the south pole, is always (at least for a human lifetime) pointed to the same place in the sky. But this direction is tilted by about 23.5° when compared to the plane of the Earth’s orbit.
With this tilt, half the time the north pole will be pointing slightly toward the sun (the seasons we call spring and summer) and half the time it will be pointing slightly away (fall and winter). The equinoxes are the in between points.
The word equinox literally means “equal night,” so on the equinox the daylight and nighttime are both twelve hours long. And that is true for everywhere on Earth. The fact that the Earth’s axis is pointing at a right angle to the Sun – neither toward it or away from it – is true for the entire planet, not just for dwellers in one hemisphere or another.
If you happen to be standing on the equator at the equinox, it will be one of the two days when the sun will pass directly overhead, or right through your zenith point. Also, only on the equinoxes will the sun rise due east and set due west. This is true for everyone on Earth, so you might go out at sunset to verify this. Before the equinox, the sun will rise to the north of east and set to the north of west, and afterward it will rise and set to the south.
Venus is making its appearance as the evening star, but it is still close to the sun and will set soon after sunset.
Saturn is at opposition tonight. This is when it makes its closest approach to Earth and will be crossing the meridian at our local midnight. Because we are a bit to the west in our time zone and have the unfortunate situation called daylight saving time, this doesn’t happen until almost 1:30 in the morning. If you want to see Saturn earlier in the evening, it will be the brightest thing low in the southeastern sky right after sunset.
Neptune will also be at opposition later this month, but unlike Saturn, which is one of the most impressive objects to see in a small telescope, Neptune will be just a tiny blue dot even in large Earth-based telescopes. The James Webb telescope, however, has taken some impressive infrared images of Neptune that show its faint ring.
Astronomers are still waiting for the expected nova of T Coronae Borealis, the Blaze Star. The constellation Corona Borealis, home of the Blaze Star, is on a straight line between Vega and Arcturus. Vega and Arcturus are still the brightest stars in the sky. Vega is near the zenith, and Arcturus is in the western sky. In the shape of a C, none of the stars of Corona Borealis are particularly bright. If the Blaze Star does erupt this month, it should be brighter than the other stars in the constellation, but likely not as bright as Vega or Arcturus. Keep watching this month to see if there is something “new” visible in the constellation.
Charles Hakes teaches in the physics and engineering department at Fort Lewis College and is the director of the Fort Lewis Observatory.
