PLANETS
What are terrestrial planets?
Mercury, Venus, Earth, and Mars—small, rocky planets.
What is a dwarf planet? Give an example.
A body that orbits the Sun but hasn’t cleared its orbit of debris; example: Pluto.
What is the Kuiper Belt?
A region beyond Neptune filled with icy bodies, comets, and dwarf planets.
Why is space exploration important for understanding the universe?
It provides direct evidence and data about celestial bodies, their materials, and cosmic phenomena.
What is the corona of the Sun?
The outermost layer of the Sun’s atmosphere, visible during a solar eclipse.
What is an equinox?
When the Sun is directly above the equator, and day and night are equal in length.
What causes the phases of the Moon?
The changing positions of the Moon, Earth, and Sun, altering how much of the Moon’s lit side we see.
What is a lunar eclipse?
When Earth passes between the Sun and the Moon, casting a shadow on the Moon.
What are gas giants?
Jupiter, Saturn, Uranus, and Neptune—large planets made mostly of gas.
What is an asteroid?
A rocky body orbiting the Sun, mostly found in the asteroid belt between Mars and Jupiter.
What is the Oort Cloud?
A distant spherical shell of icy bodies thought to be the source of long-period comets.
What was the first artificial satellite launched into space, and who launched it?
Sputnik 1, launched by the Soviet Union in 1957.
What layer of the Sun produces light?
The photosphere.
What is a solstice?
When the Sun is at its farthest point north or south of the equator, marking the longest or shortest day.
What is the Moon’s surface covered with?
Regolith—dust and rocky debris.
Why don’t solar and lunar eclipses happen every month?
Because the Moon’s orbit is tilted about 5° relative to Earth’s orbit, so the Sun, Earth, and Moon don’t line up perfectly each month.
Which planet has the most moons?
Jupiter
What is a comet made of?
Ice, dust, and rock; sometimes called a “dirty snowball.”
What are the three main shapes of galaxies?
Spiral, elliptical, and irregular.
Who was the first American astronaut to orbit Earth?
John Glenn, in 1962 aboard Friendship 7.
What effect do solar flares have on Earth?
They can disrupt satellites, radio signals, and power grids.
What causes Earth’s seasons?
The tilt of Earth’s axis as it orbits the Sun.
What are impact craters?
Depressions formed when meteoroids strike the Moon’s surface.
What is a solar eclipse?
When the Moon passes between Earth and the Sun, blocking the Sun’s light.
Why does Venus have such high surface temperatures?
It has a thick atmosphere of carbon dioxide, causing a strong greenhouse effect.
What is the difference between a meteoroid, meteor, and meteorite?
Meteoroid: space rock in space; Meteor: burns up in Earth’s atmosphere (“shooting star”); Meteorite: reaches Earth’s surface.
What holds galaxies together?
Gravity, along with the presence of dark matter, which provides additional mass not seen directly.
What U.S. space program was responsible for landing astronauts on the Moon?
The Apollo program.
What is the solar wind?
A stream of charged particles released from the Sun’s corona.
What are neap tides?
Lower high tides and higher low tides caused when the Sun and Moon are at right angles to Earth.
Why does the Moon always show the same face to Earth?
It is tidally locked, rotating once for every orbit around Earth.
During a lunar eclipse, why does the Moon often appear reddish in color?
Earth’s atmosphere bends and filters sunlight, allowing red light to reach and illuminate the Moon.
Why is Mars often called the “Red Planet”?
Because its surface contains iron oxide (rust), which gives it a reddish appearance.
What is Ceres, and where is it located in the solar system?
Ceres is the largest object in the asteroid belt, located between Mars and Jupiter and is classified as a dwarf planet.
What is a supercluster?
A massive group of galaxy clusters bound together by gravity, forming some of the largest structures in the universe.
What was the first space shuttle to fly into orbit?
Columbia, in 1981.
What process produces the Sun’s energy?
Nuclear fusion of hydrogen into helium in the core.
What causes tides on Earth?
The gravitational pull of the Moon and Sun on Earth’s oceans.
What causes the Moon’s surface to have so many craters compared to Earth?
The Moon lacks an atmosphere to burn up meteoroids and has little geologic activity to erase impacts, so craters remain visible.
What is the difference between the umbra and the penumbra during an eclipse?
The umbra is the darkest part of the shadow where the Sun is completely blocked, while the penumbra is the lighter outer shadow where the Sun is only partially blocked.