Kitt Peak Nightly Observing Program
Splendors of the Universe on YOUR Night!
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The Big Dipper (also known as the Plough) is an asterism consisting of the seven brightest stars of the constellation Ursa Major. Four define a “bowl” or “body” and three define a “handle” or “head”. It is recognized as a distinct grouping in many cultures. The North Star (Polaris), the current northern pole star and the tip of the handle of the Little Dipper, can be located by extending an imaginary line from Big Dipper star Merak (β) through Dubhe (α). This makes it useful in celestial navigation.
Constellation Ursa Minor is colloquially known in the US as the Little Dipper, because its seven brightest stars seem to form the shape of a dipper (ladle or scoop). The star at the end of the dipper handle is Polaris, the North Star. Polaris can also be found by following a line through two stars in Ursa Major—Alpha and Beta Ursae Majoris—that form the end of the ‘bowl’ of the Big Dipper, for 30 degrees (three upright fists at arms’ length) across the night sky.
The Summer Triangle is an asterism involving a triangle drawn on the northern hemisphere’s celestial sphere. Its defining vertices are the stars Altair, Deneb, and Vega, which are the brightest stars in the constellations Aquila, Cygnus, and Lyra, respectively.
The brightest stars in the zodiac constellation Sagittarius form the shape of a teapot, complete with lid, handle, and spout. The plane of the Milky Way runs through Sagittarius, and just over the spout and lid of the teapot, making it look as if steam is rising from the spout of the teapot. The center of our Milky Way galaxy is in the direction of this starry steam.
Boötes has a funny name. Pronounced boh-OH-deez, this constellation’s name means sheepherder, or herdsman. It looks kind of like a kite, or a shoe. Some remember that “Boötes look like a boot” to help pick it out in the sky.
King Cepheus from Greek mythology was husband to Cassiopeia and father of Andromeda. The brightest stars in the constellation Cepheus seem to form a kind of crooked house, with the roof pointing to the North. this constellation is very near the Celestial North Pole, so it’s not visible from the Southern Hemisphere. The star Delta Cephei was the first ever identified cepheid variable star, a very important kind of variable stars that helps astronomers determine distances to nearby galaxies.
Corona Borealis, or “Northern Crown”, is a tiara-shaped, or C-shaped constellation. Its brightest star, called Alphecca, or Gemma, shines like the crown jewel centerpiece of a brilliant celestial tiara. It’s southern counterpart, Corona Australis, or “Southern Crown” lies just south of the ecliptic.
Cygnus is a large constellation, prominent in the Northern Hemisphere. Its name comes from the Greek for “Swan” and can be imagined as a giant, celestial swan, flying overhead, with its wings fully extended. The brightest star in Cygnus is Deneb, which is one of the brightest stars in the sky, and a whopping 800 lightyears away! Deneb is one point of an asterism called the Summer Triangle—three very bright stars that form a large triangle shape prominent in the Northern hemisphere summer skies.
Draco the dragon lies close to the North polar point of the celestial sphere. Thus, it is best viewed from north of the equator. This celestial dragon has a long serpentine shape that winds around the constellation Ursa Minor (better known by the name Little Dipper), which is far fainter than it’s companion, Ursa Major. The tail of Draco separates these two constellations.
Hercules is named for the famous hero of Greek mythology by the same name. It’s one of the larger constellations, but its stars are of only moderate brightness. The Keystone is a well known trapezoid-shaped asterism (association of stars that are not an official constellation) within Hercules. This constellation is host to M13 (Messier 13), a globular star cluster. Otherwise known as the Hercules Globular Cluster, M13 is home to 300,000 stars, and is just over 22,000 light-years away.
Leo is a fairly well known constellation, because the plane of the Solar System runs through it. Such constellations are called Zodiac Constellations. Leo has some notable, bright stars, in it to boot. The brightest of these, Regulus is at the bottom of a series of stars arrayed in the form of a sickle, or a backwards question mark. This constellation does look more or less like the side profile of a lion lying on the ground, with its head up.
Libra is a fainter constellation, but easy enough to spot, once you’re familiar with the shape. It lies along the ecliptic (the plane of the Solar System), so planets pass through now and then. The names of the two brightest stars of Libra, which are Zubeneschamali and Zubenelgenubi, come form Arabic, and mean “the northern claw”, and “the southern claw”, respectively. Libra was once considered to be part of the constellation Scorpius, the scorpion. Zubeneschamali and Zubenelgenubi were seen as the claws of the scorpion.
Lyra is a small, but notable constellation. It is host to Vega—the fifth brightest star in the sky (or sixth, counting the Sun). Not far from Vega is Messier object 57—the Ring Nebula, which is perhaps the best known planetary nebula in our sky. Lyra’s name is Greek for lyre—a kind of harp.
The name Ophiucus comes from Greek and means serpent-bearer. This constellation goes hand-in-hand with the constellation Serpens—a constellation that is uniquely divided into two parts, the head and tail of the serpent, on either side of Ophiucus. The ecliptic actually runs through the very southernmost part of the area of sky defined as this constellation, making it—technically—a zodiac constellation.
Sagittarius, the archer, is often depicted as a centaur wielding a bow and arrow. Within Sagittarius, is a fairly recognizable teapot shape known to many simply as The Teapot (the teapot is not a true constellation, but an asterism). The plane of the Milky Way passes through Sagittarius, and in fact, the center of the Milky Way is in the direction of the westernmost edge of this constellation—just above the spout of The Teapot. With the plane of the Milky Way passing through, there are a plethora of deep sky objects to be found in Sagittarius.
Both the plane of the Solar System (called the ecliptic) and the plane of the Milky Way pass through Scorpius—the scorpion. As a result, you can find both the planets of our Solar System (which move along the ecliptic), and many kinds of deep sky objects in this constellation. Scorpius’s brightest star, Antares, is also known as the Heart of the Scorpion, because of it’s reddish hue and location in the chest of the scorpion. Being both red in color, and near the ecliptic, Antares is a rival of sorts to the planet Mars, which is also reddish in color, and occasionally passes through Scorpius. The name Antares means “opposing Mars”.
Ursa Major, or, the Big Bear, is one of the best known and most well recognized constellations, but you might know it by a different name. Contained within the boundaries of the constellation Ursa Major is the Big Dipper, which is not a true constellation, but an asterism. The Big Dipper is useful for finding both the North Star and the bright star Arcturus. Follow the curve of the handle to “arc to Arcturus” and use to two stars in the dipper opposite the handle to point to the North Star.
Ursa Minor, the Little Bear, is much fainter than it’s companion the Big Bear, Ursa Major. Within Ursa Minor is the well known asterism The Little Dipper. The end of the tail of the bear, or the end of the handle of the dipper, is a star called Polaris—the Pole Star, or the North Star. This special star happens to sit at the point where the Earth’s axis of rotation intersects the sky
Virgo’s brightest star Spica is found by following the curve of the handle of the Big Dipper (“arc to Arcturus, in Boötes, then spike to Spica”).The rest of the constellation isn’t particularly bright, but Virgo lies along the ecliptic—the plane of the Solar System, so bright planets pass through occasionally.
M17 Swan Nebula
M17, also known as the “Swan Nebula,” or the “Omega Nebula” is a vast cloud of gas—mostly hydrogen, in which clumps of gas are contracting to make new stars. The nebula is 15 light-years across, and 5,500 light-years away.
M20 Trifid Nebula
M20, the “Trifid Nebula” gets its nickname from the dark dust lanes that seem to split it into three parts. It is a region of star formation—a giant cloud of gas, roughly 30 light-years across, and about 5,200 light-years away.
M8 Lagoon Nebula
M8: The “Lagoon Nebula.” A huge cloud of gas and dust beside an open cluster of stars (NGC 6530). The Lagoon is a stellar nursery, 4,100 lightyears away, towards the galactic core.
Near the top of the “teapot” in Sagittarius, M22 is one of the brightest globular star clusters in our sky, and therefore, was probably the first globular cluster ever discovered. Its 80,000 stars span a diameter of about 100 light-years.
The ecliptic is a path in the sky, forming a great circle around the Earth, which the Sun and other planets of the Solar System move along. It is formed where the plane of the Solar System intersects with the Earth’s sky.
Quick streaks of light in the sky called meteors, shooting stars, or falling stars are not stars at all: they are small bits of rock or iron that heat up, glow, and vaporize upon entering the Earth’s atmosphere. When the Earth encounters a clump of many of these particles, we see a meteor shower lasting hours or days.
That clumpy band of light is evidence that we live in a disk-shaped galaxy. Its pale glow is light from about 200 billion suns!
Human technology! There are almost 500 of these in Low Earth Orbit (we can’t see the higher ones). We see these little “moving stars” because they reflect sunlight.
The twinkling of star light is a beautiful effect of the Earth’s atmosphere. As light passes through our atmosphere, its path is deviated (refracted) multiple times before reaching the ground. Stars that are near to the horizon will scintillate much more than stars high overhead since you are looking through more air (often the refracted light will display individual colors). In space, stars would not twinkle at all. Astronomers would like it if they could control the effects of this troubling twinkle.
M7 Ptolemy Cluster
M7, also known as the “Ptolemy Cluster” is an open star cluster near the “stinger” of Scorpius. It is a group of suns in a gravitational dance, 25 light-years across and about 1,000 light-years away.
Jupiter is the largest planet in the Solar System, a “gas giant” 11 Earth-diameters across. Its atmosphere contains the Great Red Spot, a long-lived storm 2-3 times the size of the Earth. The 4 large Galilean satellites and at least 63 smaller moons orbit Jupiter.
The same side of the Moon always faces Earth because the lunar periods of rotation and revolution are the same. The surface of the moon is covered with impact craters and lava-filled basins. The Moon is about a fourth of Earth’s diameter and is about 30 Earth-diameters away.
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