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Sunday, 11 January 2015

Astronomy Essay. Observing the night sky. Splendors of the Universe. Reasons to like astronomy.

The constellation Orion. December 28, 2013.

Astronomy Essay. Part two.

When I was a kid, I used to always wonder observing the three stars that were in the same straight line distances in the night sky (Orion's belt). Because of this incidence, my curiosity grew day by day and after a certain period of time, I came to learn that they are called Orion's Belt, which is the ancient Greek warrior, Orion, but still did not understand why they are in such order with the same distance between them. And my final conclusion was that outer space is a crazy and infinite place, and is beyond imagination!

In the previous article, we've discussed a few things you can observe the night sky with the naked eye, ie planets, our galaxy, our Moon in an unusual way, satellites and the International Space Station, and conjunctions of the planets.

Comet Hale-Bopp, April 4, 1997. Credit: Johannes Kepler Observatory.


Another reason to like astronomy, is the observation of comets. Some can be seen with the naked eye, others through binoculars or a telescope. A bright comet was seen with the naked eye in 1997, Hale-Bopp. They can be discovered early, while they are at long distances from us, with their exact location in the sky, so is not difficult to be observed by us (see calendar of comets in 2015), but for other comets we do not receive early warning, if they are discovered later.

What is a comet? A comet is a ball of dirty ice and dust coming from the edge of the solar system, which they approach the Sun. The ice evaporates from solar radiation, which push those particles away from the comet, forming a tail.

Total lunar eclipse, June 15, 2011. Credit: Victor Lupu.

Another reason to like to observe the sky are eclipses.
Moon eclipses for example, can be seen once in a year or two. You can be lucky to see a total lunar eclipse, or a partial one.

Moon eclipses occur due to the fact that the shadow of Earth comrs over the lunar disc, and and the Moon transforms in a reddish colour. So our planet blocks the light of the Sun from reaching the lunar surface. If you were on the Moon at that time, you would see an Earth eclipse that would take several hours from start to finish. In other words, you would see how Earth is overlapping and move slowly across the Sun's disk.

Fron the Earth, you will see that even though the Moon is in the shadow of the Earth, the Moon is not completely dark or black, like the sun when it is eclipsed by the Moon. This is because the sun's rays are bent through Earth's atmosphere before reaching the Moon. But when are reaching it, they have a red-orange colour.

Stars at long exposure. Credit: ESO / A.Santerne.

A more fun way for those who have passion of astronomy, is photographing stars with "tails" or stars trails. The most known and most common methods is the orientation of the camera mounted on a tripod, with the Pole star in the center, then set the device to a very long exposure time, say for a few minutes, during which it the shutter. remains open What you see as a result, will be star in "streaks" after them in a circle, and in the center of this circle lies the North Star. In other words you will see stars that were rotated during shooting around the North Celestial Pole due to Earth rotation. You will see that on the edge of the image, the stripes are longer, and the closer you get to the North Pole, they are shorter.

On the long exposure images, it is possible to catch a "shooting star", ie a meteor, and meteor showers are another reason to like astronomy and observing the sky.

A meteor is actually a bit of dust in our Solar System, which is going to intercept the Earth's atmosphere through which goes in a speed so great that burn and disappear. In this way this phenomenon appears bright, and is just one of thousands of meteors which intersects the Earth's atmosphere during meteor showers such as Perseids, Orionids, Leonids etc. showers are eagerly awaited by observers from all over the Earth, because they gives us a fascinating show in their most intense moments.

It is important to know that are not meteors which are coming to Earth, but the Earth passes through the remains of disintegrated comets long time ago. These remnants of cometary dust remained suspended in space, and Earth, while travelling around the Sun every year, passes through these areas. Therefore the meteor showers occur around the same time of the year, every year.

Because of the angle at which the debris enters our atmosphere, from our perspective we see that each meteor shower radiates from a certain area of the sky, namely in the area of constellations. Therefore, to each meteor shower was given a name. Perseids radiates from the constellation Perseus, Leonids from Leo, Orionids from Orion. These names were given to be more easely observed, because knowing what meteor shower occurs on that date, you will gaze directed toward that area, and thus you will increase your chances of seeing much more shooting stars.

Photo: Lupu Victor. Date:29.10.2010.

What else you can see in the sky, is our Moon. I also wrote the past article about some aspects of it that can be seen without binoculars or a telescope, but to be able to enjoy the beauty of the Moon, it is recommended to have one of these instruments.

What can you see on the Moon with binoculars or a small telescope? The first thing that will attract attention are the dark patches called "maria" or seas, translated from Latin, but also you can observa the largest size craters on the Moon, or the brightest ones, even if they are not large, because from these are starting rays from the impact which produced those craters (eg Tycho), and these rays are actually excavated material from the body which impacted the Moon, thousands or millions of years ago.



Video of the Moon - Jupiter occultation of 15 July 2012. The image is upside down.

Also only through binoculars or a telescope, it is possible to observe occultations, when the Moon hides slowly behind it a distant body as a planet, star and why not even a comet.

Moon rises from east to west due to Earth's rotation, but the Moon it also has an orbit around our planet, and this is exactly the reverse orbit viewed from Earth, from west to east. So when the Moon occults a planet for example, it shall forward slowly in its orbit to the planet from left to right and hide it even for few hours. It is a time when you simply see not only the effect of the earth's rotation, but also as the Moon orbits Earth, something that I consider fascinating.

In the next article, I will write about more things that you can observe through binoculars or a telescope, especially the planets.

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