- Voie lactée, le 2017-07-25 à Ulverton (Québec)
- Aurora borealis (2016-10-13)
- The moon (2016-11-16)
Introduction to astronomy
Contrary to popular belief, you don't have to be a science nerd or have costly equipment to enjoy astronomy. All you have to do is look up to the stars and be filled with the wonder that we are part of this vast and silent splendor. Who hasn't already spent a night admiring the Milky Way, the stars slipping by, the Aurora Borealis and all the other treasures that are only waiting to be discovered? It's precisely that wonder of the universe that motivates amateur and professional astronomers.
The following photo is a great example of what the universe beholds. Without paying a fortune on equipment, this photo was taken with a 35mm camera and a 28 mm lens. Let's see what it tells us.
Taken with a five minute exposure, the pictures shows the rotation of the Earth during that time. Notice that at the center of the rotation we see the North Star. The further we move out from that point, the longer the trails of the other stars become. This same principal can be seen in ice skating. When a group of ice skaters form a line and turn in a circle, those towards the end have to use more energy to skate around, while those in the middle have slighter movements.
While this photo makes it appear as though the North Star is not moving, if the same picture were taken in 10,000 years, Vega would have replaced the North Star at the center of the rotation. This phenomenon is due to precession , or the movement of the Earth's axis in a circle, comparable to the motion of a spinning top. It will take 26,000 years for the Earth to come full circle. And once again, in 26,000 years the North Star will be at the center of the rotation. For those interested in learning more about precession, there is much information contained in astronomy dictionaries.
As its name suggests, the North Star is always facing north. What's more, the number of degrees between the horizon and the North Star tells those in the Northern Hemisphere their latitude (the North Star cannot be seen in the Southern Hemisphere). For example, in Montreal, the North Star is 45 degrees above the horizon (halfway between the horizon and zenith).
Here's a question for you. At what latitude is the North Star when seen from the North Pole? Answer-it is at the zenith, directly above, at a latitude of 90 degrees. Contrary to popular belief, the North Star is not the brightest star in the sky. That honor is bestowed on the star Sirius. In fact, the North Star's rate of luminosity is medium.
Being able to locate the North Star in the sky will lead you to a host of constellations nearby. Ursa Major (better known as the Big Dipper) draws a straight line to the North Star. Once you locate the Big Dipper, draw a straight line from the two stars that make up the end of the "dipper" (directly opposite to the handle). Continuing five times their length in the direction of the open end of the "dipper" will lead you directly to the North Pole. If you continue that line even further, you will find the constellation Cassiopeia.
Speaking of Cassiopeia, can you find it on the photo? To help you, try and find the constellation in the shape of a "W" (opening towards the North Star). It is near the center of the picture, a bit to the right.
As you can see, pictures can tell us much more about the sky than the naked eye. Not just for the number of stars, but also for the richness of visible hues. To the naked eye, the majority of stars look white. Looking at the picture we can see many hues: white, yellow, orange, green, blue, etc. Those colors indicate the various temperatures on the surface of the star. For example, our sun is yellow, which corresponds to stars with a surface temperature of around 6000 Celsius. Already that seems hot, but it is nothing compared to its internal temperature that totals around 100 million degree Celsius. Such a hot temperature is necessary to maintain the nuclear reactor which, without it, would make life impossible on Earth.
Lastly, the white band on the picture, which goes from top to bottom, is the Milky Way. That's one slice of our galaxy seen towards its center. To better situate ourselves, understand that Earth is two-thirds the distance between the center of our galaxy and the outer edge. Our little planet turns around the sun in one year while our sun turns around the center of our galaxy over 200 million years. Our own galaxy is moderately sized, with 100 billion stars. This is similar to our sister, the galaxy Andromeda, which is about 2 million light years from us. It is both very far and very near to us in astronomical terms. In fact, Andromeda is our neighboring galaxy. She is even visible to the naked eye. It appears as a white blur when the sky is very dark and clear (impossible to see in the city). It is interesting to realize that the light we see from Andromeda (the furthest object visible to the naked eye) took 2 million years to travel to us at the speed of light (300,000 km/second). Therefore, if one day Andromeda is destroyed, it will take 2 million years before news hits Earth.
How to find Andromeda galaxy ?
Click on the picture below and you'll see a larger map to find Andromeda galaxy.
And now, some photos...
The moon (click on the image...):
Venus transit of June 8, 2004 (click on the image...):