Topic 8 Space Flashcards
(30 cards)
What is the relationship between planets, star systems, galaxies, and the Universe?
Planets orbit stars within a star system (e.g., the Solar System). Multiple star systems form a galaxy (e.g., the Milky Way). Billions of galaxies make up the Universe.
What is the Universe?
The Universe is everything that exists, including all galaxies, star systems, planets, and space itself. It is expanding from the Big Bang.
What is a galaxy?
A galaxy is a massive system of stars, gas, dust, and dark matter held together by gravity. The Milky Way is our galaxy.
What is the Solar System?
The Solar System consists of the Sun, eight planets, their moons, dwarf planets, asteroids, and comets, all held together by the Sun’s gravity.
What is the difference between asteroids and comets?
Asteroids are rocky or metallic objects that orbit the Sun, mostly in the asteroid belt between Mars and Jupiter.
Comets are made of ice, dust, and rock and develop a tail when they approach the Sun due to heating.
What is the difference between natural and artificial satellites?
Natural satellites are celestial bodies that orbit planets (e.g., the Moon orbits Earth).
Artificial satellites are man-made objects launched into orbit for communication, navigation, or research.
What are the four inner planets of the Solar System?
Mercury, Venus, Earth, and Mars – they are rocky, also known as terrestrial planets.
What are the four outer planets of the Solar System?
Jupiter, Saturn, Uranus, and Neptune – they are gas or ice giants.
What is the Big Bang Theory?
The Big Bang Theory states that the Universe started from a single, hot, dense point and has been expanding ever since.
What evidence supports the Big Bang Theory?
The redshift of galaxies (showing expansion) and cosmic microwave background radiation (leftover heat from the early Universe).
What is the first stage in the life cycle of a star?
A nebula – a cloud of gas and dust where gravity causes particles to clump together and form a protostar.
What happens in the protostar stage?
Gravity pulls gas and dust together, increasing temperature and pressure until nuclear fusion begins, forming a main sequence star.
What is a main sequence star?
A star in its stable phase where nuclear fusion of hydrogen into helium provides outward pressure to balance gravitational collapse (e.g., the Sun).
What happens when a main sequence star runs out of hydrogen?
The core contracts, and the outer layers expand and cool, forming either a red giant (small/medium stars) or a red super giant (massive stars).
What happens to a red giant?
It sheds its outer layers, creating a planetary nebula, while the core collapses into a white dwarf.
What is a white dwarf?
A small, hot, dense core left after a red giant loses its outer layers. It cools over time to become a black dwarf (a cold, dead star).
What happens to a red super giant?
It undergoes a supernova, an enormous explosion that releases heavy elements into space.
What are the possible outcomes after a supernova?
A neutron star (if the core is dense but not too massive).
A black hole (if the core is extremely massive, collapsing under its gravity)
What is a black hole?
A region of space where gravity is so strong that nothing, not even light, can escape. Formed from the remains of the most massive stars.
Why do objects orbit each other?
Objects orbit due to gravitational attraction between them. The force of gravity pulls an object toward the larger body, while its forward motion keeps it moving in a curved path.
Why are orbiting objects constantly accelerating even though their speed doesn’t change?
Acceleration is a change in velocity (which includes direction). Since an orbiting object is constantly changing direction due to gravity, it is accelerating even if its speed remains constant.
How is the speed of an object’s orbit related to the size of its orbit?
The smaller the orbit, the faster the object must travel to remain in orbit. Larger orbits require lower speeds because gravity is weaker at greater distances.
What is the difference between a circular and an elliptical orbit?
A circular orbit has a constant distance from the object it orbits, while an elliptical orbit varies in distance, with the object moving faster when closer to the central body due to stronger gravitational pull.
What happens if the speed of an orbiting object changes?
If the object speeds up, its orbit moves into a higher, larger orbit.
If the object slows down, its orbit moves into a lower, smaller orbit.
