Cyprus Astronomy Organisation

Believe it or not, this is the most asked question that astronomers encounter. Many people do not understand the difference. In ancient times, they were considered one and the same. But the two disciplines were separated during the Age of Reason in the 17th century. Astrology is a practice of using the locations of the planets to look into a person's personality or predict the future. It is not a science and is considered a form of divination. By contrast, astronomy is the scientific study of the universe. Astronomers observe the objects in the night sky to try to determine their composition and learn more about the origin and structure of the universe.

Many people hesitate to get involved with astronomy because they believe it requires expensive equipment. The only thing you really need to enjoy the night sky is your eyes, a dark viewing location, and some patience. To get a better look at things, a pair of binoculars can provide a really good view. Many people will be surprised how many more stars and objects they can see with a decent pair of 10X binoculars. They collect much more light than the human eye and will bring much dimmer objects into view. You can even see Jupiter’s moons with binoculars. A simple camera tripod to steady the binoculars is also a good idea, since your arms can get tired very quickly.

If you live near a big city, you may not be able to see a lot of stars. The reason for this is light pollution. Dust and water vapor in the atmosphere reflects the bright city lights back down towards the ground. This “light pollution” tends to be brighter than some of the dim stars and other deep sky objects, essentially hiding them from view. To truly appreciate the night sky, you must get as far away from city lights as possible. There is no more beautiful sight then the band of the Milky Way stretching across a dark sky. We can all help to combat light pollution by convincing our local authorities to use more efficient light fixtures that shine the light on the ground and block it from going up into the sky.

The primary purposes of a telescope are to gather light and magnify an image. The aperture (opening) of a telescope is larger than that of the human eye and therefore, can gather much more light. This enables us to see dim objects that are too faint to see with the naked eye. The larger the aperture of the telescope, the more light it can gather. Telescopes also use a series of lenses and/or mirrors to magnify the image, enabling us to see more detail.

Light travels at a constant speed of 186,262 miles per second (299,792,458 meters per second). Since the speed of light is constant, it can also be used to measure vast distances. Distances between objects in space are measured in light years. One light year is equal to the distance light travels in a year, which is just under 6 trillion miles (10 trillion kilometers). The speed of light is considered to be the ultimate speed limit in the universe. Scientists believe that it is impossible to travel faster than light because any object traveling at the speed of light would have to achieve infinite mass.

The distance between the Moon and the Earth averages 238,857 miles (384,403 kilometers). Since the Moon’s orbit is not a perfect circle, its distance varies. At its farthest point, known as apogee, it is 252,080 miles (405,686 km) away. At its closest point, known as perigee, it is 225,621 miles (363,104 km) away.

Astronomers believe that the Moon was formed billions of years ago when a small planet the size of Mars collided with the Earth. The foreign planet hit with a glancing blow and ejected a large part of the Earth’s molten mantle into space. Over time, this material coalesced and cooled to form the Moon.

Although the Moon looks much larger when it is low in the sky near the horizon, this is actually just an optical illusion. It is actually the same size as when it is directly over head. This illusion has been known since ancient times and also happens with the Sun and the constellations. This same illusion works on mountains and tall buildings as well. They appear larger at long distances than they do at closer distances. The reasons for this are complex, but they have something to do with how our brains interpret the sizes of large objects on the horizon. If you don't believe this is only an illusion, you can compare the size of the Moon near the horizon to the size directly over head by holding your finger out at arm's length and comparing the sizes of the Moon with your finger.

This is a question that astronomers get asked a lot. Unfortunately, the equipment left behind by the Apollo missions is tiny in comparison to the size of the Moon. Ground-based telescopes, especially those owned by amateur observers, are not capable of resolving objects this small at such extreme distances. Extremely large telescopes could theoretically catch a bright spot of sunlight reflecting from some of the moon landing equipment, although they would not be able to observe the equipment directly.

The average distance from the Sun to the Earth is 93 million miles (149 million kilometers). Because the Earth’s orbit around the Sun is not a perfect circle, it varies. At its closest point to the Sun, known as perihelion, the distance is 91 million miles (146 million km). At is farthest point, known as aphelion, the distance is 94.5 million miles (152 million km).

The Sun is an average-sized star that is 865,000 miles (1,392,000 kilometers) in diameter. It is so large that you could fit the planet Earth inside it well over a million times. The Sun actually makes up about 99% of the entire mass of the Solar System. The remaining objects, including all of the planets, moons, comets, and asteroids compose the other 1% of the Solar System.

The core of the Sun is extremely hot at about 27 million degrees Fahrenheit (15 million degrees Celsius). The surface of the Sun is much cooler than the core, at about 9,900 degrees F (5,500 degrees C). For some strange reason, not yet completely understood by scientists, the Sun’s outer atmosphere is hotter than its surface. Known as the corona, its temperature reaches 5 million degrees F (2.7 million degrees C).

The light from the Sun travels at the speed of light, 186,282 miles per second. Since the Sun is about 93 million miles from Earth, it takes the light about 8.4 minutes to reach us. This means that when you look up at the Sun, you are actually seeing it the way it looked 8.4 minutes ago. To give you an idea just how close we are to the Sun, the light from the next nearest star, Proxima Centauri, takes 4.3 years to reach the Earth.