Astronomy: Planets and The Terrestrial Planets

Astronomy

• Astronomy studies space, celestial objects, and related phenomena.
• Astronomers are scientists researching celestial bodies.
• Astronauts or cosmonauts are trained to travel to space for understanding it better.

The Planets

• Eight planets orbit the sun in the solar system.
• The planets include Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, and Neptune.
• Planets are categorized into terrestrial (inner) and Jovian (outer) planets.
• Terrestrial planets have a hard surface, molten core, volcanoes, craters, and valleys.

The Terrestrial Planets

• Mercury is the closest and smallest planet to the sun, about two-fifths the size of Earth.
• It's named after the Roman god of travel, known for his speed.
• Mercury's diameter measures 4,878 kilometers, and it's 57 million kilometers from the sun.
• Mercury completes one revolution around the sun in 88 Earth days.
• Surface temperatures on Mercury can reach up to 467°C when exposed to direct sunlight
• Mercury can also have very low temperatures, which can sometimes reach as low as -187°C for the parts that cannot retain the heat.
• Mercury has a thin atmosphere that doesn't trap heat effectively.
• Mercury is a dense planet composed mainly of iron and nickel.
• This planet has no moons, and its magnetic field is approximately 1% of Earth's.
• Mercury's surface is dry with craters covered by a thin layer of silicates.
• Scientists discovered evidence of organic compounds, building blocks of life, and water in ice form inside shaded craters.
• Venus is the second planet from the sun, named after the Roman goddess of love and beauty.
• Venus has nearly the same size as Earth, often called the "sister planet".
• Venus lacks moons.
• Venus is approximately 108 million kilometers from the sun and rotates clockwise.
• Venus' atmosphere consists mainly of carbon monoxide and carbon dioxide, making it the hottest planet at 460°C.
• Venus requires 224.7 Earth days for one revolution around the sun.
• As the brightest object in the sky, Venus is known as the "evening star" or "morning star."
• Venus has a surface with volcano marks and deep canyons, with active volcanoes.
• The thick gaseous atmosphere and extreme heat, makes life impossible on the planet.
• Earth is the third planet from the sun and the largest terrestrial planet.
• Earth has a diameter of about 12,756 kilometers and is approximately 150 million kilometers from the sun.
• The earth has a single moon, called Luna.
• The Apollo 11 mission first achieved landing on the moon in July 1969.
• Earth's atmosphere consists of 78% nitrogen, 21% oxygen, and 1% other gases.
• Earth also has an ozone layer protects from harmful UV rays.
• Humans are inducing pollution leading to global warming that damages the ozone layer.
• Earth is the only planet with water, a conductive atmosphere, rocky surfaces, and varying climates, allowing life to survive.
• The fourth planet from the sun is Mars, named after the Roman god of war and known as the "red planet.”
• Mars is reddish due to iron oxide.
• Mars has numerous craters, including about 43,000 craters.
• Olympus Mons, the solar system's highest volcano, is located on Mars, and Valles Marineris is the largest canyon, extending up to 3,000 kilometers.
• The planet's atmosphere is thinner, resulting in temperature fluctuations between 5°C in summer and -82°C in winter.
• Mars has north and south poles with ice.
• Mars rotates on its axis in approximately 24.37 hours and revolves around the sun in about 686.99 days.

Asteroids

• Asteroids or planetoids are bits of rocks floating and scattered on orbits around the sun.
• Asteroids mostly orbit between Mars and Jupiter.
• Those asteroids are called the asteroid belt.

The Jovian Planets

• Jovian planets, also called outer planets, are gas or ice giants without solid surfaces.
• The term "Jovian" comes from Jupiter, the largest outer planet first observed by Galileo Galilei.
• Composed mainly of hydrogen and helium gases, Jovian planets have many moons and ring systems.
• Jupiter, Saturn, Uranus, and Neptune are Jovian planets.
• Jupiter is the solar system's largest planet, named after the king of the Roman gods.
• Jupiter has a diameter of about 142,984 kilometers and is 779.41 million kilometers from the sun.
• Jupiter rotates on its axis in about 10 hours and revolves around the sun in about 11.86 Earth years.
• Jupiter's atmosphere is primarily hydrogen and helium with swirling cloud stripes.
• Liquid hydrogen or even metallic hydrogen may exist inside because of the high temperature and pressure at the core.
• Jupiter has a Great Red Spot, a big storm that has been spinning for hundreds of years.
• Jupiter is surrounded by three rings made of dust particles.
• Jupiter has 79 confirmed moons, four largest moons are Io, Europa, Callisto, and Ganymede.
• Ganymede is the solar system's largest satellite.
• Saturn is the sixth planet known for its magnificent rings made of ice and rocks, named after the Roman god of agriculture.
• Saturn mainly consists of hydrogen and helium, like Jupiter.
• Saturn rotates on its axis in approximately 11 hours.
• One revolution around the sun is equivalent to 29 Earth years.
• Saturn has seven main rings of ice particles with spaces between them and 53 confirmed moons.
• Titan, Calypso, and Atlas are biggest satellites.
• Titan is the second largest satellite in the solar system.
• Uranus is the seventh planet, named after the ancient Greek king of the gods and the Roman god of the sky.
• Being a gas or ice giant, Uranus has water, hydrogen, and helium.
• Methane in Uranus's atmosphere gives it a blue-green color, with ammonia fluids and ice materials over a small rocky center.
• Uranus has a diameter of about 51,118 kilometers and is approximately 2,871 million kilometers away from the sun.
• One day on Uranus takes approximately 17.14 hours, and one year is equivalent to 84 Earth years.
• Uranus has a set of 13 rings with the outer rings appearing faint due to dark dust particles and rocks.
• Uranus spins at nearly a 90-degree angle, appearing to spin on its side and known as the "tilted planet."
• Some of its 27 known moons are called Miranda, Ariel, and Titania.
• Neptune is the eighth and most distant known planet from the sun, named after the Roman god of the sea.
• Neptune is dark and cold, with surface supersonic winds.
• Gas giant Neptune has a diameter of 49,528 kilometers and is 4,498 million kilometers from the sun.
• Neptune has atmospheric features similar to Uranus, and are called twin planets.
• Methane gas gives Neptune its blue color.
• Neptune rotates on its axis for 16 hours.
• One revolution around the sun takes 165 Earth years.
• Neptune has six rings that are difficult to see and 13 known moons.
• Triton, one of Neptune's moons, orbits Neptune in the opposite direction.

The Revolution of Earth

• Earth rotates on its axis which can be measured at 24 hours or one day.
• The rising and setting of the sun starts the day and night cycle.
• Half of Earth is facing the sun=daytime, while the other half experiences nighttime.
• Earth rotations occur smoothly at a constant speed.
• Shadows appear when opaque objects block the source of light.
• Shadow sizes depend on the position of the sun; they are longest in the early morning and late afternoon and shortest at midday.
• The Philippines is located near the equator, resulting in a tropical climate.

The Dwarf Planets

• Pluto was considered the ninth and most distant planet.
• In 2006, Pluto was categorized as a dwarf planet with four other same-sized object
• These dwarf planets are Ceres, Makemake, Haumea, and Eris, all are smaller than the eight main planets.
• Ceres orbits the asteroid belt between Mars and Jupiter.
• Makemake and Pluto are each parts of the Kuiper Belt, containing trillions of icy objects orbiting around Neptune.
• Eris orbits even farther.
• Elliptical, spiral, and irregular galaxies are the three general types of galaxies.
• The Milky Way, a spiral galaxy, is where the solar system is located.
• The sun, planets, and other celestial bodies orbiting the sun make up the solar system.
• Gravity holds everything together in the Milky Way.
• The solar system orbits the center of the Milky Way at 828,000 kilometers per hour.