Unit 3: Planetary & Stellar Science Flashcards (Complete)

Definition of a planet (according to IAU)

A celestial body that (1) orbits the Sun, (2) has enough mass for a nearly round shape, and (3) has cleared its orbit of other debris.

Difference between terrestrial and Jovian planets

Terrestrial planets are rocky (like Earth), while Jovian planets are gas giants (like Jupiter).

Highest surface temperature planet

Venus.

What is the Kuiper Belt?

A region beyond Neptune with small icy bodies, including Pluto.

Definition of the habitable zone

The region around a star where liquid water can exist on a planet's surface.

Planet tilted on its side (extreme seasons)

Uranus.

Retrograde motion

The apparent backward movement of a planet as Earth overtakes it in orbit.

Significance of Kepler’s Laws

They describe how planets orbit the Sun (elliptically, sweeping equal areas in equal time, and orbital period related to distance).

What is the Titius-Bode Law?

A pattern suggesting regular spacing of planets from the Sun.

Definition of an exoplanet

A planet orbiting a star outside our solar system.

Detection methods for exoplanets

Transit method (dimming of star) and radial velocity (wobble in star's motion).

Main factor determining a star’s lifecycle

Its mass.

Life cycle of a low-mass star (like the Sun)

Nebula → Protostar → Main Sequence → Red Giant → Planetary Nebula → White Dwarf.

What is a supernova?

An explosive death of a massive star, leading to a neutron star or black hole.

Definition of the main sequence phase

Hydrogen fusion into helium.

Nuclear fusion process in stars

Hydrogen atoms fuse into helium, releasing energy.

What is a neutron star?

A dense core left after a supernova, made mostly of neutrons.

Doppler effect in astronomy

A shift in spectral lines due to motion (redshift = away, blueshift = toward).

Galileo's contribution to stellar observation

He used telescopes to observe celestial bodies, supporting the heliocentric model.

Tycho Brahe’s role in stellar science

Provided precise planetary data before telescopes.

What is spectroscopy?

The study of how stars absorb and emit light, revealing their composition.

What is the Hertzsprung-Russell (H-R) Diagram?

A graph that classifies stars by brightness and temperature.

Who introduced computer modeling of stars?

M. Schwarzschild and Fred Hoyle.

Beginning of modern cosmology

Einstein’s General Theory of Relativity (1915).

What model did Copernicus propose?

The Heliocentric Model (Sun-centered).

Observation by Galileo supporting heliocentric model

Moons orbiting Jupiter.

Definition of the main sequence in a star's life

The phase where hydrogen is fused into helium.

Type of star ending life as a white dwarf

Low-mass stars like the Sun.

How mass affects a star’s evolution

Higher mass leads to shorter lifespans and explosive ends (supernovae).

Geocentric Model

The outdated belief that Earth is at the center of the universe and all celestial bodies orbit around it.

Heliocentric Model

The correct model of the solar system where the Sun is at the center, and planets orbit around it.

Retrograde Motion

The apparent backward motion of a planet when Earth passes it in its orbit.

Exoplanets

Planets that orbit stars outside of our solar system.

Habitable Zone

The region around a star where temperatures allow liquid water to exist on a planet's surface, crucial for life.

Main Sequence

The stable phase in a star's life where it fuses hydrogen into helium in its core.

Hertzsprung-Russell (H-R) Diagram

A graph that shows the relationship between a star’s luminosity (brightness) and its temperature (color).

Spectroscopy

A technique that analyzes the light from stars to determine their chemical composition.

Doppler Effect

The change in frequency or wavelength of light from an object moving toward or away from an observer; used to measure star/galaxy motion.

Supernova

A massive explosion marking the end of a large star’s life, often creating neutron stars or black holes.