Bright Stars in the Sky
January 19, 2014
Though this blog mainly focuses on comets, asteroids and meteors, the blog postings which seem to get the most hits are those referring to bright stars visible in the sky. This shouldn’t be too surprising since the most frequent (and often times most obvious) sites in the sky are bright stars low near the horizon during the hours most people are out and about (just after sunset and right before sunrise).
This post will provide a quick sweep of the early evening and early morning sky to highlight some of the brighter objects in the sky.
Most of the bright star action as soon as it gets dark in the evening is located in the southeastern sky. Not only do we have the usual Winter Sky suspects, but Jupiter joins them this year. Located in the middle of Gemini to the right of the pair of bright Gemini stars, Castor and Pollux, Jupiter outshines every star and planet in the evening sky. A few recent high-resolution images of Jupiter can be seen in this post.
The brightest star in the sky (though still half the brightness of Jupiter) is Sirius. This time of the year Sirius gets a lot of attention because of its location close to the horizon near sunset. When so low Sirius may appear to not only change brightness but also to vary in color if the air is turbulent.
Sirius is a blue star but can appear to change color rapidly. The reason for this is due to the Earth‘s atmosphere. Turbulence in the atmosphere causes the star’s light to be “bounced” all over the place. The light of the star is made up of many different colors which all “bounce” around differently. As a result, normally blue Sirius can appear to rapidly switch between many different colors when it is close to the horizon (meaning its light is passing through more atmosphere than usual). All stars experience this effect, it is just that Sirius‘ brightness makes it more evident. Watching Sirius when low in the sky with a telescope or just your eyes can be one of the best sights in the night sky.
Why does Sirius twinkle and change colors while brighter Jupiter does not? Check out Phil Plait’s explanation on his Bad Astronomy site.
More on Sirius can be found here.
Some early risers may notice brilliant Venus low in the southeast. Only a few weeks ago Venus was a brilliant evening object in the southwest right after sunset. After passing roughly between the Earth and Sun, the brightest planet is now beginning a long stint as the ‘Queen of the Morning Sky’.
Before leaving the morning sky, Robert Lunsford was able to image Venus through his 9.25″ telescope. At that time the planet was a very slender crescent. Venus shows a similar phase at this time as well.