November is the perfect time for stargazing.
Although temperatures are dropping, the early sunset and later sunrise give us almost fifteen hours of darkness to observe the nocturnal splendors. Plus, there are some interesting events that light up the skies throughout the month.
Why not take some time this month to contemplate these heavenly splendors?
The Andromeda Galaxy
There are many interesting objects to see in the November skies. Perhaps the most interesting of all is the Andromeda galaxy.
In the October issue we talked about the Molinillo galaxy – M33. It is a close cousin of the much larger Andromeda galaxy, or M31.
The Andromeda Galaxy is one of the most distant objects and is easily visible to observers from very dark skies, such as those in our parks.
Distant stars, like Deneb, are 2,500 light years away (that’s the distance light travels in a year, or about 9.6 trillion kilometers). The Andromeda galaxy, on the other hand, is about 2,540,000 light years away.
The Andromeda Galaxy is a spiral galaxy with active H2 regions. These are the reddish areas where active star formation occurs.
It is so large that the best views for the average person are not through a telescope, but with a good pair of binoculars. With a telescope, there is too much magnification, which scatters the light and makes it difficult to see.
Galaxies are giant organizations of gas, dust, stars, planets, and other interesting objects. The Andromeda galaxy is the largest member of our local group of galaxies, which includes our Milky Way, the Pinwheel, and about 20 other galaxies of various sizes.
Almost all galaxies are perceived to be moving away from us due to the cosmic expansion of the universe. However, the Andromeda galaxy is approaching us and we expect a collision to occur in the future.
But don’t worry, the expected date of this collision is about 4.5 billion years in the future!
A variable star is a star whose brightness changes over time.
There are many reasons why a star may appear to change brightness. Sometimes a bright star may be in orbit around a fainter star. When the fainter star passes in front of the brighter one, we see that the overall brightness of the stars decreases. Sometimes a star enters a phase in its life where it goes through a period of changing amounts of energy production.
In the fall skies we have three prominent variable stars that are quite interesting.
Algol, in Perseus, is an eclipsing binary star. It is a fainter star passing in front of a brighter one. As a result, it loses half of its shine in just under 3 days. This star is also known as the Demon star and, perhaps appropriately, marks the head of Medusa.
See, on Cetus, it’s a slow-period variable star that varies in just under a year. Its brightness change is significant. It varies from being visible in a light-polluted urban sky to being too faint to see even with binoculars in a very dark sky site. Mira is a red giant star that is losing mass to a nearby white dwarf star.
In this photograph (below left) taken by NASA’s Chandra X-ray Observatory, we can see the red giant on the right and gas swirling around the white dwarf on the left (as shown on the right).
Chandra Observatory: NASA
Delta Cephei is a reasonably bright variable star in Cepheus. It is another variable star that experiences instabilities in its outer atmosphere. Delta Cephei represents a class of variable stars, the Cepheid Variables, which are extremely important to astronomers in determining distances. Cepheid variables are very bright stars and the period of their variability is directly related to their maximum energy production.
To measure the distance to a galaxy, all an astronomer has to do is find some Cepheid variables and measure their periods. They then compare the maximum observed brightness of those stars with that of Delta Cephei. They can use a simple equation to calculate the distance to the galaxy.
This is exactly what Edwin Hubble and his team did to determine the distance to Andromeda in the 1920s.
The Leonid meteor shower peaks on the morning of November 17-18. Right now, viewers in dark skies can see 15 to 20 meteors per hour.
While not constant, the Leonids can sometimes provide extraordinary rainfall. This year’s shower doesn’t seem to be as exciting, however, in the past viewers have seen up to 70,000 meteors per hour. This truly remarkable sight is known as a meteor storm rather than a shower.
The best time to observe this shower is after 1:00 am, when the view of the night sky begins to orient itself in the same direction as the Earth rotates around the sun.
For a detailed explanation of meteor showers, see this link.
For more details on November skies, see our Eyes on the Skies post.