Cosmology and Solar System Review Flashcards

Vocabulary practice flashcards covering Astronomy, Cosmology, Theories on the Origin of the Universe and Solar System, Solar Physics, Planets, Moon, Space Missions, Dwarf Planets, and Astrophysical Phenomena based on the lecture notes.

Cosmology

The study of the Universe.

Astronomy

The branch of science that deals with celestial bodies.

Big Bang Theory

A theory given by Georges Lema#3tre in 1927 (published in 1931) stating that the universe originated from an explosion of concentrated matter $13.8\text{ billion years ago}$.

Edwin Hubble Theory (1929)

The expanding universe hypothesis demonstrating that distant galaxies move away from Earth with velocities proportional to their distances, known as Hubble's Law.

Steady State Theory (1948)

Theory proposed by Fred Hoyle, Hermann Bondi, and Thomas Gold proposing that the universe is constantly expanding while its average properties remain unchanged.

Galaxy

A massive collection of stars, gas, dust, and dark matter held together by gravity.

Andromeda / M-31

The nearest galaxy to the Milky Way Galaxy.

Orion Spur

A small spiral arm of the Milky Way Galaxy located between the Sagittarius and Perseus arms where our solar system lies.

Copernicus Theory

The Heliocentric theory presented by Nicolaus Copernicus in 1543 in De revolutionibus orbium coelestium, predicting that the Sun is at the center of the universe.

Nebular Hypothesis

The most widely accepted solar system origin hypothesis, first proposed by Immanuel Kant in 1755 and expanded upon by Pierre-Simon Laplace in 1796, where a collapsing cloud of gas and dust formed the solar nebula.

Planetesimal Theory

A binary theory concluded by Thomas Chrowder Chamberlin and Forest Ray Moulton in 1905 proposing that matter was drawn out from the Sun by a passing star's gravitational attraction to form planets.

Binary Star Hypothesis

Theory proposed by H.N. Russell in 1937 proposing that planets formed from debris left behind when the Sun's companion star exploded.

Celestial Bodies

Objects in space that glow in the night sky, such as planets, stars, moons, asteroids, comets, and galaxies.

Stellar Nebula

Clouds of gas and dust that serve as the birthplace of stars.

Layers of the Sun

Ordered from inside out: Core, Radiative Zone, Convective Zone, Photosphere, Chromosphere, and Corona.

Photosphere

The outermost visible part of the Sun.

Corona

The outermost layer of the Sun, which is extremely hot and not visible to the naked eye except during solar eclipses.

Solar Flares

Short-lived, powerful bursts of radiation energy caused by magnetic activity on the Sun.

Solar Wind

The steady, ongoing continuous flow of charged particles streaming from the Sun's corona.

Sunspots

Temporary, planet-sized darker regions on the Sun's surface caused by intense magnetic activity that inhibits heat transfer, making them cooler than the surrounding photosphere.

Van Allen Radiation Belt

Two concentric rings around Earth that trap charged particles when solar flares and solar winds interact with Earth's magnetic field.

Coronal Mass Ejections (CMEs)

Expulsions of physical material from the Sun caused by magnetic reconnection, distinct from solar flares which are primarily bursts of light and high-energy particles.

Aurora

A atmospheric light phenomenon created at Earth's poles when solar flares hit the atmosphere, called Aurora Borealis at the north pole and Aurora Australis at the south pole.

Terrestrial Planets

Small, solid, rocky planets nearer to the Sun with few or no moons and no rings (Mercury, Venus, Earth, Mars).

Jovian Planets

Immense gaseous planets far from the Sun with multiple moons and ring systems (Jupiter, Saturn, Uranus, Neptune).

Mercury

The closest and smallest planet to the Sun ($4900\,km$ diameter), fastest in revolution ($172500\,km/h$ or $47\,km/s$ in $88\text{ days}$), having no atmosphere and second highest density.

Venus

The hottest and brightest planet in the solar system, known as 'Earth's Twin' and 'Lucifer', covered with thick clouds of Sulfuric acid ($H_2SO_4$) with the slowest rotation of $243\text{ Earth days}$.

Earth

The 'Blue Planet' with $70\%$ water cover, having the highest planetary density of $5.51\,g/cm^3$ and supporting life with its atmosphere.

Olympus Mons

The largest volcano and tallest mountain in the solar system, measuring $22-25\,km$ in height, located on Mars.

Asteroid Belt

A region containing asteroids, rocks, and comets located between the orbits of Mars and Jupiter.

Jupiter

The largest planet in the solar system with the shortest rotation of $9\text{ hours } 55\text{ minutes}$, containing the storm known as the Great Red Spot.

Galilean Moons

Jupiter's four largest moons discovered by Galileo: Io, Europa, Ganymede (the largest moon in the solar system), and Callisto (which shows evidence of an ozone layer).

Saturn

The second largest planet, known for bright concentric rings of ice/rocks, $274\text{ moons}$ (largest being Titan), and the lowest density ($0.69\,g/cm^3$) that allows it to float in water.

Uranus

The 'Green Planet' containing atmospheric Methane ($CH_4$), discovered by William Herschel in 1781, titled 'Rolling Lopsided Planet' due to its $98^\circ$ axial tilt.

Neptune

The farthest and windiest planet, discovered by Johann Galle and Urbain Le Verrier in 1846 via mathematical predictions, with a revolution time of $165\text{ years}$ and famous moon Triton.

Lunar Exosphere

The thin orbit envelope surrounding the Moon.

Mons Huygens (Mt. Leibniz)

The highest point on the Moon.

Aditya-L1 Mission

India's first solar observatory mission launched by ISRO to study the Sun from the first Lagrange Point ($L_1$).

Lagrange Points

Positions where the gravitational pull of two large masses precisely equals the centripetal force required for a small object to move with them.

Chandrayaan-3

ISRO's third lunar exploration mission that landed the Vikram lander and Pragyaan rover at Shiv Shakti Point near the Lunar South Pole on August 23rd.

LUPEX Mission (Chandrayaan-5)

Lunar Polar Exploration mission planned by ISRO (lander) and JAXA (rover) to explore the lunar south pole for an extended duration.

Mars Orbiter Mission (MOM / Mangalyaan)

ISRO probe orbiting Mars since September 24, 2014, making ISRO the first space agency in the world to successfully reach Mars orbit on its first attempt.

Kuiper Belt

A ring of bodies beyond Neptune containing asteroids, rocks, comets, and dwarf planets.

Pluto

Discovered by Clyde Tombaugh, this former planet was reclassified as a Kuiper Belt dwarf planet by the IAU in 2006 because it could not clear its orbit of debris.

Dwarf Planets

Celestial bodies sized between planets and asteroids; includes Pluto, Eris (second largest), Makemake (third largest), Haumea (fastest rotating in Kuiper Belt), and Ceres (in Asteroid Belt).

International Space Station (ISS)

The largest man-made object in space, built by 5 space agencies (NASA, Roscosmos, JAXA, ESA, CSA), orbiting Earth at an altitude of $\sim 400\,km$ every $90\text{ minutes}$.

Chandrasekhar Limit

Proposed by Subrahmanyan Chandrasekhar in 1930, the maximum mass a white dwarf star can hold before gravitational collapse, equal to about $1.44$ times the mass of the Sun.

Pulsar

A rapidly rotating neutron star.

Supernova

A fierce explosion of a star.

Black Hole

A place in space with immense gravity from which nothing can escape.