When the Moon is between the Earth and the Sun, it is called the new moon. The new moon rises and sets about the same time as the Sun does, but we can’t see it because the side that is being lit by the Sun is the side we cannot see from Earth.
After about one week after the new moon, the moon looks like a half-circle, and it is called the first quarter because the moon has completed one-quarter of its orbit around the Earth. Half of the Moon’s sunlit side is now visible from Earth. The first quarter moon rises at about noon and sets at about midnight.
One week after the first quarter moon, the Moon has moved to a point where the Earth is between the Moon and the Sun. We can now see the entire sunlit side of the Moon. The full moon rises as the Sun sets and sets as the Sun rises.
One week after the full moon, the Moon again looks like a half-circle, and it is called the last quarter because the Moon has completed all but the last quarter of its orbit around the Earth. Half of the Moon’s sunlit side is again visible from Earth. The last quarter moon rises at about midnight and sets at about noon.
The Fission Theory: The Moon was once part of the Earth and somehow separated from the Earth early in the history of the Solar System. The present Pacific Ocean basin is the most popular site for the part of the Earth from which the Moon came.
The Capture Theory: The Moon was formed somewhere else, and was later captured by the gravitational field of the Earth.
The Condensation Theory: The Moon and the Earth condensed together from the original nebula that formed the Solar System.
The Colliding Planetesimals Theory: The interaction of earth-orbiting and Sun-orbiting planetesimals (very large chunks of rocks like asteroids) early in the history of the Solar System led to their breakup. The Moon condensed from this debris.
The Ejected Ring Theory: A planetesimal the size of Mars struck the earth, ejecting large volumes of matter. A disk of orbiting material was formed, and this matter eventually condensed to form the Moon in orbit around the Earth.
Venus is known as the Earth's "twin" because the two planets are so similar in size.
As seen from the Earth, Venus is brighter than any other planet or even any star. When Venus is near its brightest point, it can be seen in daylight.
They named Venus in honor of the Roman goddess of love and beauty.
Geologists have had difficulty learning about the surface of Venus because the planet is always surrounded by thick clouds of sulfuric acid. They have used radar, radio astronomy equipment, and space probes to "explore" Venus.
Until recently, much of what geologists knew about the surface of Venus came from ground-based radar observations, the Soviet Union's Venera space probes, and United States Pioneer probes. In 1990, the U.S. space probe Magellan began orbiting Venus, using radar to map the planet's surface.
The surface of Venus is extremely hot and dry. There is no liquid water on the planet's surface because the high temperature would cause any liquid to boil away.
Mars is the fourth planet from the sun. The planet is one of Earth's "next-door neighbors" in space.
Mars is named for the ancient Roman god of war. Viewed from Earth, Mars is a bright reddish-orange. It owes its color to iron-rich minerals in its soil.
Scientists have found strong evidence that water once flowed on the surface of Mars. A space probe has also discovered vast amounts of ice beneath the surface, most of it near the south pole.
The Martian surface has many spectacular features, including a canyon system that is much deeper and much longer than the Grand Canyon in the United States. Mars also has mountains that are much higher than Mount Everest, Earth's highest peak.
Jupiter is the largest planet in the solar system. It would take more than 1,000 Earths to fill up the volume of the giant planet. When viewed from Earth, Jupiter appears brighter than most stars. It is usually the second brightest planet -- after Venus.
Jupiter is the fifth planet from the sun. Ancient astronomers named Jupiter after the king of the Roman gods.
Jupiter has 16 satellites that measure at least 6 miles (10 kilometers) in diameter. It also has many smaller satellites. Jupiter's four largest satellites, in order of their distance from Jupiter, are Io, Europa, Ganymede, and Callisto. These four moons are called the Galilean satellites. The Italian astronomer Galileo discovered them in 1610 with one of the earliest telescopes.
Io has many active volcanoes, which produce gases containing sulfur. The yellow-orange surface of Io probably consists largely of solid sulfur that was deposited by the eruptions. Europa ranks as the smallest of the Galilean satellites. Europa has a smooth, cracked, icy surface.
The largest Galilean satellite is Ganymede. Ganymede is larger than the planet Mercury. Callisto, is slightly smaller than Mercury. Ganymede and Callisto appear to consist of ice and some rocky material. The two satellites have many craters.
Jupiter has three thin rings around its equator. They are much fainter than the rings of Saturn. Jupiter's rings appear to consist mostly of fine dust particles.
Saturn is the second largest planet. Saturn has seven thin, flat rings around it. The rings consist of numerous narrow ringlets, which are made up of ice particles that travel around the planet. The gleaming rings make Saturn one of the most beautiful objects in the solar system.
They named it for the Roman god of agriculture.
Saturn travels around the sun in an elliptical (oval-shaped) orbit. The planet takes about 10,759 Earth days, or about 29 1/2 Earth years, to go around the sun, compared with 365 days, or one year, for Earth.
In addition to its rings, Saturn has 25 satellites that measure at least 6 miles (10 kilometers) in diameter, and several smaller satellites. The largest of Saturn's satellites, Titan, has a diameter of about 3,200 miles (5,150 kilometers) -- larger than the planets Mercury and Pluto. Titan is one of the few satellites in the solar system known to have an atmosphere. Its atmosphere consists largely of nitrogen.
Many of Saturn's satellites have large craters. For example, Mimas has a crater that covers about one-third the diameter of the satellite. Another satellite, Iapetus, has a bright side and a dark side.
Uranus is the seventh planet from the sun. Uranus is the farthest planet that can be seen without a telescope. Uranus is a giant ball of gas and liquid. The surface of Uranus consists of blue-green clouds made up of tiny crystals of methane. The crystals have frozen out of the planet's atmosphere.
Uranus was the first planet discovered since ancient times. British astronomer William Herschel discovered it in 1781. Johann E. Bode, a German astronomer, named it Uranus after a sky god in Greek mythology. Most of our information about Uranus comes from the flight of the United States spacecraft Voyager 2. In 1986, that craft flew within about 50,000 miles (80,000 kilometers) of the planet's cloud tops.
Uranus is tilted so far on its side that its axis lies nearly level with its path around the sun. Many astronomers think that a collision with an Earth-sized planet may have knocked Uranus on its side soon after it was formed.
Neptune cannot be seen without a telescope. Neptune is about 30 times as far from the sun as is Earth.
Every 248 years Pluto moves inside Neptune's orbit for about a 20-year period, during which it is closer to the sun than Neptune. Pluto last crossed Neptune's orbit on Jan. 23, 1979, and remained within it until Feb. 11, 1999.
Neptune's diameter at the equator is 30,775 miles (49,528 kilometers), or almost 4 times that of Earth. It is about 17 times as massive (heavy) as Earth, but is not so dense as Earth. Neptune has 11 satellites (moons) and several rings around it.
Neptune has 11 known satellites. Triton, Neptune's largest satellite. It is the only major satellite in the solar system that orbits in a direction opposite to that of its planet. Triton may once have been a large comet that traveled around the sun. Scientists have discovered evidence that volcanoes on Triton once spewed a slushy mixture of water and ammonia. This mixture is now frozen on Triton's surface. Triton has a surface temperature of -390 degrees F (-235 degrees C), the coldest known temperature in the solar system. Some volcanoes on Triton remain active, shooting crystals of nitrogen ice as high as 6 miles (10 kilometers) above the moon's surface.
Dwarf Planets The dwarf planets - Ceres, Pluto, & Eris Pluto, a Kuiper object, was demoted to the status of dwarf planet in 2006 when the International Astronomical Union (IAU) reviewed Pluto's status in light of the recently discovered Eris, also a Kuiper object, but somewhat larger than Pluto. At the same time the former asteroid Ceres was promoted to dwarf planet. The IAU defines a dwarf plant as a celestial body that, within the Solar System: is in orbit around the Sun; has sufficient mass for its self-gravity to overcome rigid body forces so that it assumes a hydrostatic equilibrium (near-spherical) shape; has not cleared the neighborhood around its orbit; and is not a satellite Point 3 is what distinguishes the dwarf planets from the remaining eight planets. In this image, from left to right are the dwarf planets Ceres, Pluto, and Eris. Eris was discovered in 2003 and is now the largest of the known dwarf planets. It is believed to be slightly more massive than Pluto and follows a highly eccentric orbit that alternately brings it as close as the orbits of Neptune and Pluto and as far as over twice Pluto's furthest distance from the Sun.
Pluto, (PLOO toh), is a dwarf planet that orbits far from the sun. It shares the region of its orbit, known as the Kuiper belt, with a collection of similar icy bodies called Kuiper belt objects (KBO’s). From its discovery in 1930, people widely considered Pluto to be the ninth planet of our solar system. However, because of its small size and irregular orbit, many astronomers questioned whether Pluto should be grouped with worlds like Earth and Jupiter. Pluto seemed to share more similarities with KBO’s. In 2006, this debate led the International Astronomical Union, the recognized authority in naming heavenly objects, to formally classify Pluto as a dwarf planet. Pluto cannot be seen without a telescope.
As it orbits the sun, Pluto spins on its axis, an imaginary line through its center. It spins around once in about six Earth days.
Astronomers know little about Pluto's size or surface conditions because it is so far from Earth. Pluto has an estimated diameter of about 1,400 miles (2,300 kilometers), less than a fifth that of Earth. Pluto's surface is one of the coldest places in our solar system. Astronomers believe the temperature on Pluto may be about –375 °F (–225 °C).
Pluto is mostly brown. The planet appears to be partly covered with frozen methane gas and to have a thin atmosphere composed mostly of methane. Because Pluto's density is low, astronomers think Pluto is mainly icy. Scientists doubt Pluto has any form of life.
In 1905, Percival Lowell, an American astronomer, found that the force of gravity of some unknown object seemed to be affecting the orbits of Neptune and Uranus. In 1915, he predicted the location of a new planet and began searching for it from his observatory in Flagstaff, Arizona. He used a telescope to photograph the area of the sky where he thought the planet would be found. He died in 1916 without finding it. In 1929, Clyde W. Tombaugh, an assistant at the Lowell Observatory, used predictions made by Lowell and other astronomers and photographed the sky with a more powerful, wide-angle telescope. In 1930, Tombaugh found Pluto's image on three photographs. The planet was named after the Roman god of the dead. The name also honors Percival Lowell, whose initials are the first two letters of Pluto.
In 1978, astronomers at the U.S. Naval Observatory substation in Flagstaff detected a satellite of Pluto. They named it Charon.
14. A solar system is a group of objects that orbit a star in the center, plus the star itself. 15. A plane t is a large object that orbits a star. 16. These mostly lie in an orbit between Mars and Jupiter and are made of rock and metal: asteroids . 17. A come t is a ball of rock, ice, and frozen gases. 18. The Inner Planets are made mostly ofrock. 19. The Outer Planets are mostly made of gas. Lesson 3 Answers Mercury Closest planet to the sun. Surface appears much like the moon. Venus Earth’s “twin”, the surface is covered with thick clouds of sulfuric acid. Earth 2/3 of the surface is covered with water. It only has 1 natural satellite. Takes 1 day to spin on its axis. Mars Named for the God of War. Also nicknamed “the Red Planet” because it looks fiery red from Earth Jupiter Largest planet of the solar system. Has the “Great Red Spot.” Named for the king of the gods. Saturn Well-known for its beautiful ring system. Can be seen with the unaided eye. Uranus First planet discovered by modern scientists. Tilted onto its side. Neptune Cannot be seen with the naked eye. Farthest planet from the sun.
Elliptical galaxies have very little gas or dust and no stars have recently formed within them. They can range from a near perfect sphere or a flattened disc.
Galaxies of a third kind, irregular galaxies , lack a simple shape. Some consist mostly of blue stars and puffy clouds of gas, but little dust. The Magellanic Clouds are irregular galaxies of this type. Others are made up mostly of bright young stars along with gas and dust.
In astronomy, the geocentric model or the Ptolemaic worldview of the universe is the theory that the Earth is the center of the universe and other objects go around it. Belief in this system was common in ancient Greece.
It was embraced by both Aristotle and Ptolemy, and most, but not all, Ancient Greek philosophers assumed that the Sun, Moon, stars, and naked eye planets circle the Earth. Similar ideas were held in ancient China.
Nicolaus Copernicus (19 February 1473 – 24 May 1543) was the first astronomer to formulate a comprehensive heliocentric cosmology, which displaced the Earth from the center of the universe.
Galileo Galilei (15 February 1564 – 8 January 1642) was an Italian physicist, mathematician, astronomer, and philosopher who played a major role in the Scientific Revolution. His achievements include improvements to the telescope and consequent astronomical observations. He discovered the 4 major moons of Jupiter.
On October 4, 1957, the Soviet Union sent Sputnik 1 into orbit. It was the first artificial satellite.
On April 12, 1961 the first human to go into space. In the spaceship Vostok 1, Senior Lieutenant Yuri Alexeyevich Gagarin orbited earth one time at an altitude of 187 3/4 miles (302 kilometers) for 108 minutes at 18,000 miles an hour.