Polaris and the Big and Little Dippers
6 comentarios Imprimir Enviar a un amigoEl Cielo Esta Noche 10 sep, 2007
Tonight’s chart shows the evening sky with the Big Dipper low in the northwestern sky. Notice that a line from the two outermost stars in the bowl of the Big Dipper point to Polaris, the North Star. And notice that Polaris marks the tip of the handle of the Little Dipper.
Compare this chart to the chart from August 2, and note that the Big Dipper is lower in the northwest in the evening now than it was a month ago. A month from now at this time, the Big Dipper will be due north, but directly below Polaris, the North Star.
This constant motion from night to night, circling Polaris, is a bit like a bear circling its prey, looking for a way to attack. It may be just this fact that caused several ancient cultures from the Greek and Romans to some American Indians to liken these stars to a bear. The Big Dipper asterism represents the bright central stars of the constellation Ursa Major, the Great Bear.
You can also compare the northern sky to a large clock, with Polaris at its center. The hour hand is a line drawn through Dubhe and Merak, the two pointer stars of the Big Dipper. Because the stars make a full circle in 23 hours 56 minutes instead of exactly 24 hours, this star clock is not exactly the same as the one on the wall, but with a little practice you can learn to read it well.
I love looking at the little dipper through the telescope,that is the best way to see it. There are just so many stars together. It’s very beautiful and cool.
Hi, Esperansa. A telescope brings out details and somes allows you to see color. You are absolutely right that it can help you see more of the beauty of the sky. And often a pair of good binoculars is even better, in part because it can show a wider area of sky at a time. However, in general the Little Dipper is qutie faint, except for Polaris, and by your description I am wondering if you may be looking at something else. I think you might be looking at the Pleiades or "The Seven Sisters" (http://www.earthsky.org/faq/pleiades-seven-sisters). Right now it rises at about 11 p.m. and is high overheard by dawn for most locations in North America.
Larry Sessions
My telescope doesnt see color. Why is that? I looked at Jupiter and all I saw was a blurry blob and a white dot next to it which was probably one of its moons. I mean I did see color on Jupiter but if I look at a star there all the same color.
Bob, ordinary telescopes do handle color. However, rarely does anything look in a small telescope the way they appear in photos in books, magazines or online. Often photos from space are manipulated to make them show different levels of detail, and this often involves intensifying the colors so that they are brighter and more evident. Sometimes it means that colors show up in the photo that aren’t even visible to the human eye. Also, most photos from space are taken with highly sensitive instruments and over sometimes long periods of time. (Some of the Hubble Space Telescope exposures have been more than two weeks!). This also causes the colors to be intensified.
Now as for Jupiter specifically, it frankly just isn’t too colorful in small telescopes or to the human eye. There are shades of yellow, brown and maybe even blue, along with the great Red Spot (and “Red Spot Junior”), but most of this is hard to discern. As a result, through a small scope, Jupiter usually appears a yellowish offwhite or gray.
LS
Would Polaris still be visible at 5:00 in the morning? I’ve been seeing a fairly bright star in the west/northwest and have been wondering what it is.
Laura
Laura,
Polaris would likely be visible at 5 a.m., but it is not particularly bright and it does not appear in the west-northwest sky. Polaris is as I recall the 56th or 57th brigthest star in the sky, nowhere near the brightest. It is the Pole Star or the North Star, and as such is always due north. Right now there is a bright star called Vega — the 5th brightest star in all the sky — very near the west-northwestern horizon for most of us in North America. At 5 a.m. it is very low, however, so I can’t be sure that is what you are seeing. I can only say with some confidence that Polaris is not to the west-northwest, so you likely are seeing something else.
LS