6.1 Constellations

Constellations األبراج

• Patterns of stars in the sky.• 88 constellations (1930).• Served as a calendar.• Some imagination.• No physical relation between members of any constellation.

االبراج الشمسية

1. Aries = الحمل ( March 21 - April 20) برج2. Taurus = الثور (April 21 - May 21) برج3. Gemini = الجوزاء ( May 22 - June 21) برج4. Cancer = السرطان ( June 22 - July 22) برج5. Leo = األسد ( July 23 -August 21) برج6. Vigro = العذراء ( August 22 - September 23) برج7. Libra = الميزان (September 24 - October 23) برج8. Scorpio = العقرب ( October 24 - November 22) برج9. Sagittarius = القوس (November 23 - December 22) برج10. Capricorn = الجدي ( December 23 - January 20 ) برج11. Aquarius = الدلو ( January 21 - February 19) برج12. Pisces = الحوت (February 20- March 20)برج

Zodiac: circle of animals البروج دائرةa band in which planets move.

Orion, the Hunter

• Orion is one of the most beautiful of all constellations, and one of the easiest to find. It looks like a large rectangle high in winter's south-southeastern sky.

• Two of the brightest stars in the evening sky lie at opposite corners of the rectangle: bright red Betelgeuse at the northeastern corner and even brighter Rigel at the southwest.

• Near the center of the rectangle, look for a short diagonal line of three stars — Orion's belt. And extending south from the belt, you'll see another, fainter line of stars that forms Orion's sword.

• One of the objects in Orion's sword isn't a star at all. It's a nebula — a cloud of gas and dust that's like a giant fluorescent bulb. Hot young stars inside the nebula pump energy into its gas, causing the gas to glow.

Naming• is the brightest star in a constellation.• is the 2nd brightest.• And so on …• Example: Betelgeuse is of the Orion.

»Rigel is of the Orion.

Ursa Major, the Great Bear

• Ursa Major — the great bear — is always above the horizon in the northern latitudes, but the best time to see it is in the spring when its high above the northeastern horizon. Ursa Major is best known as the home of the Big Dipper.

• Of all the star patterns in the sky, the Big Dipper is the most universally recognized. The dipper's seven bright stars form a portion of the great bear. It's hard to see the rest of the bear, especially from light-polluted cities.

• After you locate the dipper, look at the two stars that mark the outer edge of its bowl. Now connect these two stars, then extend the line above the dipper's bowl. Polaris, the north star, lies along this line, about five times the distance between the two pointers. No matter where the Big Dipper is in our sky, those two stars always point to Polaris.

Canis Major, the Great Dog

• Canis Major loyally follows its mythical master, Orion, across the southern skies of winter.

• he brightest star in Canis Major also is the brightest in the entire night sky — brilliant Sirius, which is just 8.6 light-years away. That's only twice as far as our closest stellar neighbor.

Gemini, the Twins

• Gemini is easy to find as it glides high overhead in mid-winter, above and to the left of Orion. It's two brightest stars — Castor and Pollux — represent the mythological twins brothers of Helen of Troy.

• Many cultures have seen two humans in this star pattern — marked by two roughly parallel lines of stars capped by two of the brightest stars in our night sky. But the legend that endures is that of Castor and Pollux. Gemini's two brightest stars bear the names of the twins.

• Pollux is the brighter of the twins. It's an orange-giant star that's about 35 light-years from Earth. Castor consists of six stars — a cosmic sextet locked in a gravitational ballet. This crowded system lies about 50 light-years from Earth.

Leo, the Lion

• The zodiacal constellation Leo, the lion, is one of a handful of constellations that really does look like its namesake. Look for Leo high in south in April and May.

• Leo's brightest star is blue-white Regulus, one of the brightest stars in the night sky. Regulus rises almost due east, with the body of the lion following it into the sky over the next couple of hours. Once Regulus climbs into the sky, look to its left — toward the north — for a group of stars forming a backward question mark. These stars outline Leo's head and mane.

• About two hours later, look low in the east for Leo's tail — a white star named Denebola — an Arabic name that, appropriately enough, means "tail of the lion."

Sagittarius, the Archer

• Sagittarius, the archer — whose brightest stars form the shape of a teapot — slides low across the southern sky of summer. Sagittarius is a centaur — a mythological half-man, half-horse — who has drawn his bow. His arrow is pointing at Antares, the bright red heart of Scorpius, the scorpion. The archer is avenging Orion, who was slain by the scorpion's sting. However, to modern eyes, the brightest stars of Sagittarius appear to outline a teapot. Steam pours from the spout — the hazy starclouds of the Milky Way.

• The center of our Milky Way galaxy lies inside Sagittarius, about 27,000 light-years away. It is immersed in the glow of the starclouds a little above the "spout" of Sagittarius' teapot. The constellation also contains several globular clusters — tightly packed collections of hundreds of thousands of stars.

Scorpius, the Scorpion

• Three bright stars form the "head" of Scorpius, the celestial scorpion, while its tail curves away below it in the southern sky of summer.

• The brightest star in Scorpius is Antares, which is in the middle of the scorpion's curving body. This brilliant red star is one of the behemoths of our stellar neighborhood. If you placed it at the center of our own solar system, it would swallow Mercury, Venus, Earth, and Mars, and almost reach Jupiter.

Taurus, the Bull

• Taurus, the bull, is marked by a V-shaped pattern of stars that outlines the bull's face. Bright red Aldebaran, the "eye" of the bull, stands at one point of the V. This pattern is part of a cluster of stars called the Hyades — the second-closest star cluster to Earth. It consists of several hundred stars that lie about 130 light-years away.

• Aldebaran outshines all the other stars that outline the bull's face. But Aldebaran isn't a member of the Hyades cluster — it just lies in the same direction. It's about 70 light-years away, half as far as the stars of the Hyades. Aldebaran is a red-giant — an old, bloated star that's used up most of its nuclear fuel. It's much larger and much brighter than our own middle-aged Sun.

Perseus, the Hero

• Perseus, the hero, arcs high overhead in fall and early winter. Many of its stars are immersed in the faint glow of our galaxy, the Milky Way. In fact, if you look at Perseus under dark skies, you may be able to see three of the spiral arms that enfold the Milky Way.

• One of the brightest and most interesting stars in Perseus is Algol. The name Algol means "demon star." Ancient skywatchers thought it was cursed because its brightness changes. That's because Algol — which is about 75 light-years from Earth — is the most famous "eclipsing binary" star. Today, astronomers know that Algol is two separate stars. About once every three days, the fainter member of the pair passes in front of the brighter one, and Algol grows fainter.

• A faint star cluster in Perseus, called M34 is visible with binoculars.

Aquila, the Eagle

• Aquila glides on outstretched wings through the glowing band of the Milky Way. Look for it high in the south in late summer.

• The brightest star in Aquila is a white star about 16 light-years from Earth called Altair, the Arabic word for eagle. Altair is the southern point of a pattern of three bright stars called the Summer Triangle. Deneb, in the constellation Cygnus, forms the triangle's northeastern point. Vega, in Lyra, the harp, is in the northwest. Altair is nice and bright and easy to find right up to the beginning of winter.

Auriga, the Charioteer

• Auriga, the celestial charioteer, has neither chariot nor horse. Instead, he's drawn as a man holding the reins in his right hand, with a goat on his left shoulder — the star Capella — and two baby goats in his left arm. Look for him cruising high across the southern sky in January and February.

• The constellation has an uncertain origin. It might represent Neptune rising from the sea in a chariot. Or it might honor a legendary king of Athens; according to this tale, he invented a chariot that was drawn by four horses.

• Capella is one of the few bright stars that is yellow, like our Sun. Both Capella and the Sun are yellow because they have roughly the same surface temperature.

• But the light from Capella actually comes from two separate stars. Both are yellow, and both lie about 43 light-years from Earth. Each star emits dozens of times more light than the Sun. In fact, any residents of the Capella system probably would take little notice of our Sun, which at Capella's distance would barely be visible to human eyes

Lyra, the Harp

• It's easy to find Lyra, the harp, by first finding Vega — one of the brightest stars in Earth's night sky. Look for Vega high overhead in mid-summer. Lyra looks like a small, lopsided square, with Vega just beside one of the corners of the square.

Pegasus, the Flying Horse• Pegasus is a large pattern of stars marked by a great square

— four bright stars that form the body of the winged horse.• The brightest star in the Great Square — Alpheratz — isn't

in the constellation Pegasus. It's in Andromeda, which is just northeast of Pegasus. It's part of the ancient sky picture that we know as Pegasus. But when astronomers drew the official boundaries for the constellations, this star was placed just across the line in Andromeda.

• The brightest star in the constellation Pegasus is called Markab, which means "the saddle." It's at the southwestern corner of the Great Square.

Boötes, the Herdsman• The brightest stars of Boötes form a cone shape,

with brilliant yellow-orange Arcturus at the base of the cone. Arcturus, the fourth-brightest star in Earth's night sky, is about 20 times larger than the Sun, and it produces about a hundred times as much energy.

• But Arcturus is nearing the end of its life. In astronomical parlance, Arcturus has moved off the main sequence and entered the "giant" phase of its life. At a distance of about 35 light-years, it's closer to us than any other stellar giant.

• The name Boötes comes from a Sumerian word that means "Man Who Drove the Great Cart." The "Great Cart" was the Big Dipper. Boötes trails the Big Dipper as it wheels around the North Star.

Capricornus, the Sea-Goat

• Capricornus, the sea goat, bounds low across the southern sky in late summer and fall. Like all the constellations of the zodiac, Capricornus has as many mythological tales as it has stars. Capricornus gets its name from a Greek myth that says the god Pan was transformed into a half-goat, half-fish when he dived into the Nile River to escape the giant Typhon.

• Capricornus looks like a large triangle of fairly bright stars. The brightest stars are side-by-side at the triangle's western tip. Farthest west is Giedi — the goat. Binoculars reveal that this is really two stars. Although the stars appear near each other, they're really separated by a thousand light-years. The closer of the two is about 115 light-years from Earth, while the other is 10 times farther. Just southeast of Giedi is Dabih — the slaughterer — a name that refers to sacrifices made by ancient Arabs when Capricornus rose at the same time as the Sun. It, too, consists of more than one star.

Cassiopeia, the Queen

• The mythological queen Cassiopeia floats overhead in fall and winter.

• The best time to see her is in November, high in the northeastern sky. Cassiopeia looks like a flattened "W" against the frothy background of our home galaxy, the Milky Way. The "W" consists of five bright stars. It's surrounded by fainter stars, so it's fairly easy to pick out.

Cygnus, the Swan

• The brightest stars of Cygnus form a cross, so the swan is also known as the Northern Cross. Find it soaring high overhead during late summer evenings.

• The constellation's brightest star is Deneb — an Arabic word that means "the tail." Deneb — the tail of the swan — marks the top of the cross. The swan's outstretched wings form the horizontal bar of the cross, while the head of the swan — a double star called Albireo — is the bottom of the cross.

• Although it lies about 1,500 light-years from Earth, Deneb shines brightly in our night sky because it's a white supergiant — a star that's much larger, hotter, and brighter than the Sun. Deneb is the northeastern point of a star pattern called the Summer Triangle.

• If you use binoculars to scan the area between the two bright stars that define the swan's eastern wing, you'll see the remnant of a supernova — a faint, incomplete ring of light called the Cygnus Loop.