astrolesson

What Are Constellations?

So just what are these constellations you keep hearing about?

People have used constellations for many different reasons. And these reasons have changed throughout history.

Astronomy is the oldest science. This is because even the earliest cavemen would look up at the sky and wonder about what makes it run. People saw that the motions of the stars were regular and predictable.

The first use for Constellations was probably religious. People thought that the Gods lived in the heavens and that they created them. Many cultures believed that the positions of the stars were their God's way of telling stories. So it seemed natural to recognize patterns in the sky, give them names, and tell stories about them. We inherited the names for our constellations from the Greeks. And they named the constellations after their mythological heroes and legends. So behind every constellation there is a story. For example, to the ancient Greeks, Orion was a great hunter. He was the son of Neptune (god of the sea). But the same stars were considered to depict Osiris by the Egyptians. Each different culture developed their own interpretation.

A more practical use for constellations was agriculture. Before there were proper calendars people had no way of determining when to sow, or harvest except by the stars. Constellations made the patterns of the stars easy to remember. The ancient peoples knew for example that when the constellation Orion started to be fully visible winter was coming soon. Or they could look at the Summer Triangle to know when Summer or Spring were coming as well. The stars allowed farmers to plan ahead and form agriculture, and constellations made it easier to recognize and interpret the patterns in the sky.

The constellations also helped with navigation. It is fairly easy to spot Polaris (The North Star) once you've found Ursa Minor (Little Dipper constellation). One can figure out his/her latitude (North/South) just by looking at how high Polaris appears in the night sky. This allowed for ships to travel across the globe. It allowed for the discovery of America, the spread of European culture, and civilization as we know it today.

astronews

August 15, 2007 - Mercury in superior conjunction

August 17, 2007 - Venus in inferior conjunction

[Conjunction is a term used in positional astronomy and astrology. It means that, as seen from some place (usually the Earth), two celestial bodies appear near one another in the sky. The event is also sometimes known as an appulse.]

astroevents

August 11, 2007 - Perseid meteors

August 12, 2007 - New Moon
7:03 P.M.

August 13, 2007 - Neptune at opposition
[ Opposition occurs when a body farther from the Sun than Earth appears opposite the Sun in the sky. It is the best time to observe a planet. ]


Some extra infos about Perseids:
======================
The Perseids are a prolific meteor shower associated with the comet Swift-Tuttle. The Perseids are so called because the point they appear to come from, called the radiant, lies in the constellation Perseus. However, they can be seen all across the sky. Because of the path of Swift-Tuttle's orbit, Perseids are mostly visible on the northern hemisphere.

The shower is visible from mid-July each year, with the greatest activity between August 8 and 14, peaking about August 12. During the peak, the rate of meteors reaches 60 or more per hour.

Meteor showers occur when Earth moves through a meteor stream. The stream in this case is called the Perseid cloud and it stretches along the orbit of the Comet Swift-Tuttle. The cloud consists of particles ejected by the comet as it passed by the Sun. Most of the dust in the cloud today is approximately a thousand years old.

However, there is also a relatively young filament of dust in the stream that boiled off the comet in 1862. The approximate rate of meteors originating from this filament is much higher than normal.

The famous Perseid meteor shower has been observed for about 2000 years, with the first known information on these meteors coming from the Far East. In early Europe, the Perseids came to be known as the "tears of St. Lawrence."


[deci poate va vad pe net la noapte...AFARA!!! toata lumea afara la noapte....si maine noapte..tot afara adica]

Astronomy - Orion's belt

Orion's belt

The tight linear grouping of the prominent white stars Alnitak, Alnilam, Mintaka in the constellation of Orion. The names of all three refer to the set: the outer two are named after the "belt" of the Arabs' "Central One" (a mysterious female figure), while Alnilam comes from an Arabic word that aptly means "the string of pearls." The proximity of the three in the sky is an illusion. In fact, the stars at either end of the Belt, Alnitak and Mintaka, are the closest together in space, Alnitak being a little over 800 light-years away, and Mintaka 100 light-years farther off. The central star, Alnilam, is much more distant than either of these, lying on the edge of the Orion Molecular Cloud, more than 1,300 light-years from the Sun. Alnilam is also easily the most massive and luminous of the three stars, so that despite its greater distance it still shines more brightly than its two companions.

Like much of its parent constellation, Orion's Belt is a highly nebulous region of the sky. This is especially true in the direction of Alnitak, where numerous nebular structures are found. The most famous of these is the Horsehead Nebula, a dark cloud that blots out the light from the red-pink streak of IC 424.

Mythology

Greek mythology has several versions of the history of Orion, the gigantic hunter of primordial times. These end in different versions of his death: He challenged the gods, either by attempting to rape Artemis or by claiming that he could kill every wild animal on Earth. Some versions then say Artemis shot him with her arrows; but others say that Artemis or Earth produced a great Scorpion whom he could not defeat and which killed him. The gods raised him and the Scorpion to the skies, as Scorpio/Scorpius. Yet other stories say Orion was chasing the Pleiades.

Sirius, the Dog Star, constitutes Orion's left leg. It is part of Canis Major and has its own mythology. In some myths, it is Orion's hunting dog.

astroevents

August 10, 2007 - Moon near Pollux [at 22h UT, morning sky]

August 11, 2007 - Perseid meteors

August 12,2007 - New Moon at 22:30 UT. Start of lunation 1047.
[A lunation is the cycle of phases in one synodic month, starting and ending with a "new moon". This is slightly longer than the sidereal lunar month, in which the Moon revolves once around the Earth, because of the additional effect of the Earth's revolution around the Sun.]

astroinfo

July 30, 2007 - Neptune 1.3° north of Moon, occultation
August 1, 2007 - Mercury 6° south of Pollux
August 1, 2007 - Uranus 2° south of Moon
August 2, 2007 - Venus 6° south of Regulus
August 3, 2007 - Moon at perigee

[ perigee = the point in the moon's orbit when it is closest from earth ]

astronews

July 30, 2007 - Neptune 1.3° north of Moon, occultation

[ An occultation is an event that occurs when one object is hidden by another object that passes between it and the observer ]

astroevents

July 27, 2007 - Delta Aquarid meteors

July 29, 2007 - Full Moon

astroevents

July 27, 2007 - Delta Aquarid meteors

astroevents

25.July.2007 - Venus stationary [ The body appears motionless in the sky due to the turning point between its direct and retrograde motion ]

25.July.2007 - Antares 0.6° north of Moon, occultation

25.July.2007 - Jupiter 6° north of Moon

25.July.2007 - Delta Aquarid meteors