BINOCULAR HIGHLIGHTS


The Constellation Auriga The Charioteer dominates the center of this sky view above the WNW horizon about an hour after sunset in early May. If you look this same direction in early to mid April, the constellations will be about 8 to 5 degrees higher in the sky. You can see that the winter constellations Orion, Gemini, part of Taurus (in Hyades star cluster), The Pleiades, Auriga, and Perseus are bidding us ado as springtime progresses. We're even leaving Mars behind too as our faster orbiting home planet Earth speeds ahead of the red planet in our merry-go-round called the solar system.
The northern horizon has special treats in store for us through April and May. The constellation Draco The Dragon is in a good position to see its entire undulating shape more like a snake with a dragon's head marked by the oblong trapezoid of stars close to the northeast horizon. Draco is a constellation that has star designations that don't agree with their brightness levels. For example, Thuban is a 3.7 magnitude star which is the Alpha star in Draco. However, there are six other stars in this constellation including Aldhibain (ald-HI-bain) and Eltanin (EL-tah-nin) that are brighter than Thuban. Why is this? Perhaps it's because of the importance of Thuban which used to be the North Star some 5,000 years ago. The constellation Draco got its name in antiquity so it stands to reason that Thuban, which in those times was the near motionless star that all others rotated around, was considered an important or Alpha star. I've drawn a yellow circle depicting how the Earth's true north pole drifts through the millennia through a process called precession (see next image).

If you follow the yellow circle counterclockwise from Thuban, you can see how far Earth's true north pole has moved or precessed over the last 5,000 years. Continuing along the yellow circle, you can see that Vega will eventually become the brightest North Star along the entire circumference in the year 13,727! Earth precesses or wobbles at a very slow rate. It takes about 26,000 years for the Earth's true north pole to scribe this circle once, so don't hold your breath! BTW...Earth's precession is the reason astronomical star charts have to be revised every 50 years for what is called a new "epoch". The star positions on the celestial sphere (Earth's global latitude and longitude lines projected out into space) must be re-indexed each epoch to correct their locations in DEClination (DEC) which is latitude and Right Ascension (RA) which is longitude.
This graphic shows how Earth's polar axis precesses scribing a circle through the heavens. It is also compared to a spinning top which is slowing down and wobbling as it does so. The image of Earth has another line that forms a 23.5 degree arc with its polar axis. What is this? It represents the tilt of Earth's axis relative to the Sun. Here's a good astronomy question: What season is depicted in this graphic? The answer will come in the June issue.
The western horizon is showing the winter constellations setting soon after sunset. Meanwhile, the eastern horizon is showing a "preview" of the summer constellations to come. Bright magnitude 0 Arcturus sits prominently above the eastern horizon and will continue to shine through the rest of Spring and all of Summer. The small but interesting constellation Corona Borealis or Northern Crown contains some interesting overlooked objects. We'll concentrate on the one that we can see well with binoculars. Look at the medium bright (magnitude 2.2) star at the lower left part of the letter "A" in the word "BOREALIS" in the above image. It is Alphecca (al-FECK-ah) which is the brightest star in this constellation and I guess you could say is also the crown jewel! Alphecca is an eclipsing binary that orbit each other every 17 and one third days. The reason Alphecca is not as well known as the famous "Evil Eye" eclipsing binary star, Algol is the brightness change during the Alphecca-A and Alphecca-B eclipse is a barely noticeable magnitude 0.11.