Planets
Stars
Galaxies
The Universe
Life in the Universe
100

This planet has a day (rotation period) longer than its year.

What is Venus?

100

This diagram classifies stars by luminosity and temperature.

What is the Hertzsprung–Russell diagram?

100

The Milky Way is this general type of galaxy.

What is a spiral galaxy?

100

This theory explains that the universe is expanding from an initial hot, dense state.

What is the Big Bang theory?

100

This NASA telescope was famous for detecting thousands of exoplanets by looking for tiny dips in starlight.

What is Kepler?

200

This planet’s large storm system, known as the Great Red Spot, has lasted for centuries.

What is Jupiter?

200

This is the approximate surface temperature of the Sun.

What is about 5,800 Kelvin?

200

This supermassive black hole lives at the center of the Milky Way Galaxy.

What is Sagittarius A-star?

200

The leftover glow of the early universe, now cooled to just a few Kelvin, is known as this.

What is the cosmic microwave background?

200

This term describes the study of life’s potential beyond Earth.

What is astrobiology?

300

These small rocky bodies orbit between Mars and Jupiter and are leftovers from solar system formation.

What are asteroids?

300

This is the stage in a star’s life cycle when it fuses hydrogen to helium in its core.

What is the main-sequence stage?

300

This relation uses standard candles like Cepheid variables to determine a galaxy’s distance.

What is the period–luminosity relation?

300

This effect stretches the wavelength of light from galaxies moving away from us.

What is redshift?

300

This is the most common molecule in Earth’s atmosphere and crucial for protecting life by scattering harmful UV radiation.

What is nitrogen?

400

This process mimics Italian salad dressing sitting on a shelf, and what is responsible for heavy metals concentrating in the center of an object.

What is differentiation?

400

These two opposing forces determine the size of a stable star.

What are gravity and pressure?

400

These galaxies are thought to form when spirals merge.

What are elliptical galaxies?

400

This mysterious energy component makes up roughly 70% of the universe and accelerates its expansion.

What is dark energy?

400

This principle states that the simplest explanation consistent with the data should be preferred—a key idea when evaluating extraterrestrial signals.  Slice away ASSUMPTIONS.

What is Occam’s Razor?

500

This term describes a planet that orbits a star outside our solar system and is detected when it blocks some of the star’s light.

What is a transiting exoplanet?

500

A star of about 1 solar mass will eventually shed its outer layers to form this glowing shroud of ionized gas.

What is a planetary nebula?

500

The relationship between galaxy rotation curves and mass distribution provided early evidence for this.

What is Dark Matter?

500

This space-time concept says observers moving relative to each other measure time and distance differently.

What is special relativity?

500

This famous equation estimates the number of technologically advanced civilizations in our galaxy.

What is the Drake Equation?