Correct: B. 3rd

Earth is the third planet from the Sun and the only astronomical object known to harbor life. It is the densest planet in the Solar System and the largest and most massive of the four terrestrial planets. Earth's lithosphere is divided into several rigid tectonic plates that migrate across the surface over periods of many millions of years. About 71% of Earth's surface is covered with water, mostly by its oceans, while the remaining 29% is land consisting of continents and islands. Earth's atmosphere consists mostly of nitrogen and oxygen, which are vital for life.

Correct: A. Jupiter

Jupiter is the largest planet in our solar system, classified as a gas giant because it is composed mainly of hydrogen and helium. It is so massive that it contains more than twice the mass of all the other planets in the solar system combined. Jupiter is famous for its "Great Red Spot," a giant storm that has been raging for at least 350 years. It also has a very strong magnetic field and at least 95 moons, including Ganymede, the largest moon in the solar system.

Correct: B. Mars

Mars is known as the "Red Planet" because of its reddish appearance, which is caused by the high concentration of iron oxide (rust) on its surface. It is the fourth planet from the Sun and the second-smallest planet in the Solar System. Mars has a thin atmosphere and features such as giant volcanoes and deep canyons that suggest it was once much more like Earth.

Correct: D. D

Vitamin D is unique because it is the only vitamin that the human body can produce on its own, primarily through exposure to ultraviolet (UV) radiation from sunlight. When sunlight hits the skin, it triggers a chemical reaction that converts a form of cholesterol into Vitamin D3. It is essential for bone health because it helps the body absorb calcium.

Correct: B. Mercury

Mercury is the smallest planet in the Solar System and the one closest to the Sun. Because it has almost no atmosphere to trap heat, it experiences the most extreme temperature swings in the solar system, ranging from 430C 800F during the day to -180C -290F at night. It takes only 88 Earth days to orbit the Sun.

Correct: D. Jupiter

Jupiter is the largest planet in our solar system, with a mass more than twice that of all the other planets combined. It is a gas giant primarily made of hydrogen and helium and has at least 95 moons.

Correct: B. Vitamin D

Vitamin D is known as the "sunshine vitamin" because your body synthesizes it when your skin is exposed to ultraviolet B (UVB) rays from the sun. It is essential for the absorption of calcium and phosphorus, which are necessary for maintaining strong bones and teeth.

Correct: A. Revolution

Revolution is the term for the movement of the Earth in its orbit around the Sun. One complete revolution takes approximately 365.25 days, which is why we have a "leap year" every four years to keep our calendar in sync.

Correct: C. Saturn

Saturn has the most extensive and prominent ring system of any planet in our Solar System. These rings are made mostly of billions of tiny particles of water ice, ranging in size from dust grains to the size of mountains.

Correct: D. Milky Way

The Milky Way is the name of the spiral galaxy that contains our Solar System. From Earth, it appears as a hazy band of light in the night sky. It contains between 100 and 400 billion stars and at least that many planets.

Correct: B. A star

The Sun is a nearly perfect sphere of hot plasma at the center of our Solar System. It is a "Yellow Dwarf" star that provides the energy (in the form of light and heat) necessary for life on Earth. Its gravity holds the entire solar system together.

Correct: D. The Sun

The Sun is the closest star to Earth, located at an average distance of about 93 million miles (150 million km). The next closest star system is Proxima Centauri, which is about 4.24 light-years away.

Correct: D. 8

There are currently eight recognized planets in our Solar System: Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, and Neptune. Pluto was reclassified as a "dwarf planet" in 2006.

Correct: C. The Moon

The Moon is Earth's only natural satellite. It is the fifth-largest satellite in the Solar System and is thought to have formed about 4.5 billion years ago, shortly after Earth, likely from the debris of a massive collision between Earth and a Mars-sized body.

Correct: A. Venus

Venus is often called the "Evening Star" (or "Morning Star") because it is the brightest object in the night sky after the Moon. It is often visible just after sunset or just before sunrise.

Correct: D. Sputnik 1

Sputnik 1 was the first human-made satellite to orbit the Earth. It was launched by the Soviet Union on October 4, 1957. It was a polished metal sphere with four external radio antennas that broadcast radio pulses back to Earth.

Correct: D. Astronomy

Astronomy is the scientific study of celestial objects (like stars, planets, and galaxies) and phenomena that originate outside Earth's atmosphere. It is one of the oldest sciences in human history.

Correct: D. Mercury

Mercury is the smallest planet in our Solar System. It is only slightly larger than Earth's Moon and has no atmosphere to speak of.

Correct: A. Hubble

The Hubble Space Telescope was launched into low Earth orbit in 1990 and remains in operation today. It has provided some of the most detailed and iconic images of distant stars, nebulae, and galaxies, fundamentally changing our understanding of the universe.

Correct: B. Meteors

Shooting stars are not actually stars; they are meteors. These are small pieces of space rock or dust (meteoroids) that enter Earth's atmosphere at high speeds and burn up due to friction, creating a bright streak of light.

Correct: D. Venus

Venus is often called "Earth's Twin" because it is very similar to Earth in size, mass, and composition. However, their environments are drastically different, with Venus being a hellish world of extreme heat and toxic clouds.

Correct: D. Saturn

Saturn is the second-largest planet in the Solar System, after Jupiter. Like Jupiter, it is a gas giant primarily made of hydrogen and helium.

Correct: B. Polaris

Polaris is the name of the North Star. It is located almost directly above the Earth's North Pole, so it appears to stay fixed in the sky while all other stars rotate around it.

Correct: C. Solar Eclipse

A solar eclipse occurs when the Moon passes between the Sun and Earth, blocking some or all of the Sun's light from reaching Earth. A "total" solar eclipse is a rare event for any specific location.

Correct: A. Pluto

Pluto was reclassified as a "dwarf planet" by the International Astronomical Union (IAU) in 2006. This was because it had not "cleared its neighborhood" of other debris, which is one of the three requirements to be a full planet.

Correct: D. Venus

Venus is often called the "Morning Star" or the "Evening Star" because it is the brightest object in the night sky after the Moon. Because its orbit is closer to the Sun than Earth's, it is always visible near the horizon shortly before sunrise or after sunset. It is so bright that it can sometimes be seen even during broad daylight if the conditions are perfect.

Correct: C. Mercury

Mercury is the smallest planet in our solar system, having lost that title to Pluto until Pluto was reclassified as a dwarf planet. It is only slightly larger than Earth's moon and is made mostly of rock and metal. Because it is so small, it has very little gravity and almost no atmosphere.

Correct: D. Earth

Earth is known as the "Blue Planet" because of its striking blue appearance when viewed from space. This blue color comes from the vast oceans that cover approximately 71% of Earth's surface, containing about 97% of the planet's water. The oceans play a crucial role in regulating climate, absorbing carbon dioxide, and supporting an incredible diversity of life. No other planet in our solar system has liquid water on its surface.

Correct: C. Mars

Mars is known as the "Red Planet" because of its distinctive reddish appearance, caused by iron oxide (essentially rust) on its surface. Mars is the fourth planet from the Sun and has a thin atmosphere composed primarily of carbon dioxide. It features the largest volcano in the solar system (Olympus Mons) and a canyon system (Valles Marineris) that would stretch across the entire United States.

Correct: B. Mercury

Mercury is the smallest planet in our solar system, with a diameter of only 4,879 kilometers (3,032 miles)just slightly larger than Earth's Moon. It is the closest planet to the Sun and has no moons. Mercury has a heavily cratered surface, resembling our Moon, and a large iron core that makes it exceptionally dense.

Correct: A. Milky Way

The Milky Way is the galaxy that contains our Solar System, including the Sun and Earth. It is a barred spiral galaxy with an estimated 100-400 billion stars and a diameter of about 100,000 light-years. Our Solar System is located in one of its spiral arms, about 26,000 light-years from the galactic center. The name "Milky Way" comes from its appearance as a dim, milky band of light in the night sky.

Correct: C. Gravity

Gravity is the force that keeps planets in orbit around the Sun. It is the natural phenomenon by which all things with mass are brought toward one another. The Sun's enormous mass creates a strong gravitational field that pulls the planets toward it, while their forward motion keeps them from falling into it, creating a stable orbit.

Correct: C. Distance

A light-year is a unit of distance, not time. It represents the distance that light travels in one year through a vacuum. Since light moves at about 300,000 kilometers per second (186,000 miles per second), one light-year is approximately 9.46 trillion kilometers (5.88 trillion miles). This unit is used to measure astronomical distances.

Correct: B. The Sun

The Sun is the star at the center of our Solar System, accounting for 99.86% of the system's total mass. It is a nearly perfect sphere of hot plasma, heated to incandescence by nuclear fusion reactions in its core. The Sun's energy sustains almost all life on Earth through photosynthesis and drives our climate and weather.

Correct: B. Comets

Comets are icy objects that orbit the Sun and develop tails when they approach the inner solar system. They are composed of ice, dust, and rocky particles, often described as "dirty snowballs." As a comet gets closer to the Sun, heat causes its ice to sublimate into gas, releasing dust and creating a glowing coma (atmosphere) around the nucleus and one or two tails pointing away from the Sun.

Correct: B. Phases

The Moon goes through phases-different shapes as seen from Earth-over approximately 29.5 days (a lunar month). These phases are caused by the changing angles of the Sun, Earth, and Moon. The eight main phases are: new moon, waxing crescent, first quarter, waxing gibbous, full moon, waning gibbous, last quarter, and waning crescent.

Correct: C. Orion

Orion is the constellation known as "The Hunter." It is one of the most prominent and recognizable constellations in the night sky, visible throughout the world. Orion is named after a hunter in Greek mythology. Its brightest stars include Betelgeuse (a red supergiant) and Rigel (a blue supergiant), and its famous "belt" consists of three bright stars in a line.

Correct: A. One celestial body blocking another

An eclipse occurs when one celestial body blocks the light from another. A solar eclipse happens when the Moon passes between the Sun and Earth, casting a shadow on Earth. A lunar eclipse happens when Earth passes between the Sun and Moon, casting its shadow on the Moon.