Title: Astronomy Cosmos — LearnCoachAssist

Q: What is astronomy?
A: The scientific study of celestial objects, space, and the physical universe.

Q: What is cosmology?
A: The study of the universe's origin, evolution, and large-scale structure.

Q: What is the Solar System?
A: The Sun and the gravitationally bound system of planets, moons, and other bodies.

Q: How many planets are in our Solar System?
A: Eight (since Pluto's reclassification in 2006).

Q: What are the inner rocky planets?
A: Mercury, Venus, Earth, Mars.

Q: What are the gas giants?
A: Jupiter and Saturn.

Q: What are the ice giants?
A: Uranus and Neptune.

Q: What is the asteroid belt?
A: A region between Mars and Jupiter populated by small rocky bodies.

Q: What is the Kuiper Belt?
A: A disk-shaped region beyond Neptune containing icy bodies, including Pluto.

Q: What is the Oort Cloud?
A: A spherical shell of icy objects at the outer edge of the Solar System.

Q: What is the Sun?
A: A G-type main-sequence yellow dwarf star at the center of our Solar System.

Q: How old is the Sun?
A: About 4.6 billion years.

Q: What fuels the Sun?
A: Nuclear fusion of hydrogen into helium in its core.

Q: What is the Sun's surface temperature?
A: About 5,500 °C (5,778 K).

Q: What is the corona?
A: The Sun's outermost atmosphere, far hotter than the surface.

Q: What are sunspots?
A: Cooler, darker regions on the Sun's surface caused by magnetic activity.

Q: What is a solar flare?
A: A sudden, intense burst of radiation from the Sun.

Q: What is the solar wind?
A: A stream of charged particles flowing from the Sun.

Q: What is heliosphere?
A: The bubble of space dominated by the Sun's plasma and magnetic field.

Q: What is one Astronomical Unit (AU)?
A: The average Earth-Sun distance, about 150 million km.

Q: What is a light-year?
A: The distance light travels in one year, about 9.46 trillion km.

Q: How long does sunlight take to reach Earth?
A: About 8 minutes 20 seconds.

Q: What is a galaxy?
A: A massive system of stars, gas, dust, and dark matter bound by gravity.

Q: What galaxy do we live in?
A: The Milky Way.

Q: What type of galaxy is the Milky Way?
A: A barred spiral galaxy.

Q: How many stars are in the Milky Way?
A: An estimated 100–400 billion.

Q: Where is our Solar System in the Milky Way?
A: In the Orion Arm, about 26,000 light-years from the galactic center.

Q: What is at the center of most galaxies?
A: A supermassive black hole.

Q: What is the supermassive black hole at our galaxy's center called?
A: Sagittarius A* (Sgr A*).

Q: What is the closest large galaxy to the Milky Way?
A: The Andromeda Galaxy (M31), about 2.5 million light-years away.

Q: What is the Local Group?
A: The group of about 80 galaxies including the Milky Way and Andromeda.

Q: What is a star?
A: A massive, luminous sphere of plasma generating energy by fusion.

Q: What is the main sequence?
A: The stable phase where stars fuse hydrogen into helium in their cores.

Q: What is a red giant?
A: A star that has exhausted hydrogen in its core and expanded.

Q: What is a white dwarf?
A: The compact remnant of a low- to medium-mass star after shedding outer layers.

Q: What is a supernova?
A: An explosive death of a massive star.

Q: What is a neutron star?
A: An ultra-dense stellar remnant after a supernova, composed mostly of neutrons.

Q: What is a pulsar?
A: A rapidly rotating neutron star emitting beams of radiation.

Q: What is a black hole?
A: A region of spacetime where gravity is so strong nothing, not even light, can escape.

Q: What is the event horizon?
A: The boundary of a black hole beyond which escape is impossible.

Q: What is a singularity?
A: A point of infinite density at the center of a black hole (in classical GR).

Q: What is the Schwarzschild radius?
A: The radius of the event horizon of a non-rotating black hole.

Q: What is the Big Bang?
A: The leading theory that the universe began ~13.8 billion years ago from a hot, dense state and expanded.

Q: How old is the universe?
A: About 13.8 billion years.

Q: What is cosmic microwave background (CMB)?
A: Residual radiation from the Big Bang, observed in the microwave spectrum.

Q: Who discovered the CMB?
A: Arno Penzias and Robert Wilson, 1964.

Q: What is redshift?
A: The lengthening of light wavelengths from receding objects.

Q: What is blueshift?
A: The shortening of light wavelengths from approaching objects.

Q: Who discovered the universe is expanding?
A: Edwin Hubble, in 1929.

Q: What is Hubble's law?
A: More distant galaxies recede faster (v = H₀d).

Q: What is the Hubble constant?
A: The rate of expansion of the universe (~70 km/s/Mpc).

Q: What is dark matter?
A: Hypothesized matter that doesn't emit light but exerts gravity, making up ~27% of the universe.

Q: What is dark energy?
A: A mysterious force driving the accelerating expansion of the universe, making up ~68%.

Q: What is general relativity?
A: Einstein's theory of gravity describing it as curvature of spacetime by mass-energy.

Q: What is special relativity?
A: Einstein's theory of physics at high velocities, with constant light speed.

Q: What is the speed of light?
A: ~299,792,458 m/s in a vacuum.

Q: What is the equivalence principle?
A: Gravitational and inertial mass are equivalent (gravitational and accelerating frames look the same).

Q: What is a gravitational wave?
A: A ripple in spacetime caused by accelerating masses.

Q: Who first detected gravitational waves?
A: LIGO in 2015, from a binary black hole merger.

Q: What is parallax?
A: The apparent shift in an object's position due to observer movement; used to measure stellar distances.

Q: What is a parsec?
A: ~3.26 light-years; the distance at which 1 AU subtends 1 arcsecond.

Q: What is the brightest star in Earth's night sky?
A: Sirius.

Q: What is the North Star?
A: Polaris, near the north celestial pole.

Q: What is a constellation?
A: A pattern of stars in the sky, often named after mythological figures.

Q: How many official constellations are there?
A: 88.

Q: What is the zodiac?
A: A circle of 12 constellations along the ecliptic.

Q: What is the ecliptic?
A: The Sun's apparent path across the sky.

Q: What causes seasons?
A: Earth's axial tilt of about 23.5°.

Q: What is an equinox?
A: A day when day and night are nearly equal in length.

Q: What is a solstice?
A: A day with the longest or shortest period of daylight.

Q: What is a meteor?
A: A streak of light from a meteoroid burning in Earth's atmosphere.

Q: What is a meteorite?
A: A meteoroid that survives passage through the atmosphere and lands on the surface.

Q: What is an asteroid?
A: A small rocky body orbiting the Sun, mostly in the asteroid belt.

Q: What is a comet?
A: An icy body that develops a tail when near the Sun due to vaporization.

Q: What causes a comet's tail?
A: Sunlight and solar wind pushing gas and dust away from the comet.

Q: What is Halley's Comet?
A: A famous short-period comet visible from Earth every ~76 years.

Q: What is a dwarf planet?
A: A celestial body orbiting the Sun, large enough to be round but not having cleared its orbit.

Q: Name some dwarf planets.
A: Pluto, Eris, Haumea, Makemake, Ceres.

Q: What is the brightest planet in the sky?
A: Venus.

Q: Why is Venus called Earth's twin?
A: Similar size and mass, though with a hostile atmosphere.

Q: What is Mars sometimes called?
A: The Red Planet, due to iron oxide on its surface.

Q: What is the largest mountain in the Solar System?
A: Olympus Mons on Mars.

Q: What is the Great Red Spot?
A: A persistent giant storm on Jupiter.

Q: How many moons does Jupiter have?
A: Over 90 confirmed (as of recent counts).

Q: What are Galilean moons?
A: Io, Europa, Ganymede, Callisto — Jupiter's largest moons discovered by Galileo.

Q: What is the largest moon in the Solar System?
A: Ganymede (of Jupiter).

Q: Which Saturn moon may host life?
A: Enceladus or Titan, both intriguing for astrobiology.

Q: What is special about Titan?
A: It has a thick atmosphere and liquid hydrocarbon lakes.

Q: Which planet has the most prominent rings?
A: Saturn.

Q: What are Saturn's rings made of?
A: Mostly ice particles with rocky and dust components.

Q: What is Neptune's largest moon?
A: Triton.

Q: What's interesting about Triton's orbit?
A: It orbits Neptune retrograde, suggesting it was captured from the Kuiper Belt.

Q: What is Earth's moon's diameter?
A: About 3,474 km (~1/4 of Earth's).

Q: How did the Moon form?
A: Likely from a giant impact between Earth and a Mars-sized body (Theia) ~4.5 billion years ago.

Q: What causes tides?
A: The Moon's (and Sun's) gravitational pull on Earth's oceans.

Q: What is a spring tide?
A: A higher-than-usual tide when Sun, Earth, Moon align.

Q: What is a neap tide?
A: A weaker tide when Sun and Moon are at right angles relative to Earth.

Q: What is a lunar eclipse?
A: When Earth's shadow falls on the Moon.

Q: What is a solar eclipse?
A: When the Moon passes between the Sun and Earth, blocking sunlight.

Q: What is the difference between a total and a partial solar eclipse?
A: Total eclipses fully cover the Sun; partial only some of it.

Q: What is an annular eclipse?
A: When the Moon is too far to fully cover the Sun, leaving a bright ring.

Q: What was the first artificial satellite?
A: Sputnik 1, launched by the USSR in 1957.

Q: Who was the first human in space?
A: Yuri Gagarin, in 1961.

Q: Who was the first American in space?
A: Alan Shepard, in 1961.

Q: When did Apollo 11 land on the Moon?
A: July 20, 1969.

Q: Who were the first people on the Moon?
A: Neil Armstrong and Buzz Aldrin.

Q: What is the International Space Station (ISS)?
A: A modular space station in low Earth orbit, occupied since 2000.

Q: What is the Hubble Space Telescope?
A: A space telescope launched in 1990, orbiting Earth.

Q: What is the James Webb Space Telescope (JWST)?
A: A large infrared space telescope launched in 2021, successor to Hubble.

Q: What is exoplanet?
A: A planet orbiting a star other than the Sun.

Q: How many exoplanets have been confirmed?
A: Over 5,000 confirmed as of 2024.

Q: What is the habitable zone?
A: The region around a star where liquid water could exist on a planet's surface.

Q: What is a transit method?
A: Detecting exoplanets by observing dips in stellar brightness as they pass in front.

Q: What is radial velocity method?
A: Detecting exoplanets by measuring stellar wobble caused by orbital pull.

Q: What is microlensing?
A: Detecting exoplanets via gravitational distortion of distant starlight.

Q: What is direct imaging?
A: Capturing an exoplanet's light directly, requiring blocking host star.

Q: What is the Drake Equation?
A: A probabilistic formula estimating the number of detectable extraterrestrial civilizations.

Q: What is the Fermi Paradox?
A: The contradiction between high probability of alien life and lack of evidence.

Q: What is SETI?
A: The Search for Extraterrestrial Intelligence; observing for signals.

Q: What is panspermia?
A: The hypothesis that life on Earth originated from elsewhere in space.

Q: What is astrobiology?
A: The study of life in the universe, including its origins and potential elsewhere.

Q: What is a nebula?
A: A vast cloud of gas and dust in space, often a stellar nursery.

Q: What is the Orion Nebula?
A: A bright nebula in the constellation Orion, visible to the naked eye.

Q: What is a planetary nebula?
A: A glowing shell of gas ejected from a dying low- to medium-mass star.

Q: What is a supernova remnant?
A: The expanding gas and dust left over from a supernova explosion.

Q: What is a globular cluster?
A: A spherical, dense collection of old stars bound by gravity.

Q: What is an open cluster?
A: A loosely bound, younger group of stars formed together.

Q: What is a binary star?
A: Two stars orbiting a common center of mass.

Q: What is an eclipsing binary?
A: A binary star where one passes in front of the other from our view.

Q: What is the Hertzsprung-Russell (H-R) diagram?
A: A plot of stars' luminosity vs. temperature, organizing them by evolution.

Q: What is spectroscopy?
A: The analysis of light by wavelength to determine composition, motion, and conditions.

Q: What are spectral classes of stars?
A: O, B, A, F, G, K, M (from hottest to coolest).

Q: What spectral class is the Sun?
A: G2V (yellow main-sequence dwarf).

Q: What is luminosity?
A: The total energy emitted by a star per unit time.

Q: What is apparent magnitude?
A: How bright a star appears from Earth.

Q: What is absolute magnitude?
A: How bright a star would appear at 10 parsecs.

Q: What is the cosmological principle?
A: On large scales, the universe is homogeneous and isotropic.

Q: What is inflation?
A: A theorized rapid expansion of the early universe, smoothing it out.

Q: What is recombination?
A: The era ~380,000 years after the Big Bang when electrons combined with nuclei and the universe became transparent.

Q: What is the cosmic microwave background's temperature?
A: About 2.725 K.

Q: What is structure formation?
A: The process by which gravity built galaxies and clusters from primordial fluctuations.

Q: What is a galaxy cluster?
A: A bound group of hundreds to thousands of galaxies.

Q: What is the Virgo Cluster?
A: A nearby galaxy cluster about 54 million light-years away.

Q: What is a supercluster?
A: A vast structure of galaxy clusters; e.g., the Laniakea Supercluster.

Q: What is the observable universe?
A: The portion of the universe visible from Earth, about 93 billion light-years in diameter.

Q: What is the cosmic web?
A: The large-scale structure of the universe — filaments, walls, voids of galaxies.

Q: What is a void in cosmology?
A: A large region of space with few galaxies.

Q: What are dark filaments?
A: Galaxy chains connecting clusters in the cosmic web.

Q: What is gravitational lensing?
A: The bending of light by massive objects acting as lenses.

Q: What is microlensing again (cosmology)?
A: Brief brightening of a star as a compact object passes in front.

Q: What is a quasar?
A: An extremely luminous active galactic nucleus powered by a supermassive black hole.

Q: What is an active galactic nucleus (AGN)?
A: A galactic core emitting unusually high amounts of energy from a central black hole.

Q: What is a blazar?
A: An AGN whose jets point nearly toward Earth.

Q: What is the cosmic distance ladder?
A: A succession of methods used to measure distances on different scales.

Q: What is a Cepheid variable?
A: A pulsating star whose period correlates with luminosity, useful as distance indicator.

Q: What is a Type Ia supernova?
A: A standardizable supernova used as a "standard candle" for cosmic distances.

Q: What is a standard candle?
A: An object of known luminosity used to measure distance.

Q: What is parallax used for?
A: Measuring distances to nearby stars.

Q: What is the Drake equation's main factors?
A: Star formation rate, fraction with planets, fraction habitable, fraction with life, fraction intelligent, fraction communicating, lifetime.

Q: What is the Hertzsprung gap?
A: A region in the H-R diagram with few stars, traversed quickly during evolution.

Q: What is stellar nucleosynthesis?
A: The process by which stars create heavier elements through fusion.

Q: Where do elements heavier than iron come from?
A: Primarily supernova explosions and neutron star mergers.

Q: What is the Chandrasekhar limit?
A: ~1.44 solar masses; the maximum mass of a stable white dwarf.

Q: What is the Tolman-Oppenheimer-Volkoff limit?
A: The maximum mass of a neutron star, ~2–3 solar masses.

Q: What is a magnetar?
A: A neutron star with an extremely powerful magnetic field.

Q: What is a pulsar's clock-like nature?
A: Regular pulses from rotation, useful for timing experiments.

Q: What is a fast radio burst?
A: A millisecond-duration radio pulse from extragalactic sources.

Q: What is dark matter evidence?
A: Galactic rotation curves, gravitational lensing, CMB anisotropies, structure formation.

Q: What's a leading dark matter candidate?
A: Weakly interacting massive particles (WIMPs), axions, etc.

Q: What is MOND?
A: Modified Newtonian Dynamics — an alternative to dark matter modifying gravity.

Q: What is cold vs hot dark matter?
A: Cold moves slowly, hot moves near c; cold fits structure formation better.

Q: What is the LIGO/Virgo collaboration?
A: Observatories detecting gravitational waves.

Q: What was the first kilonova detected?
A: GW170817, a neutron star merger in 2017.

Q: What is multi-messenger astronomy?
A: Combining observations of light, gravitational waves, neutrinos, and cosmic rays.

Q: What is a neutrino?
A: A nearly massless, weakly interacting subatomic particle.

Q: What are cosmic rays?
A: High-energy particles from space hitting Earth's atmosphere.

Q: What is the Sun's solar cycle?
A: An ~11-year cycle of magnetic activity, sunspots.

Q: What is space weather?
A: Conditions in space affecting Earth, e.g., from solar wind.

Q: What is a coronal mass ejection?
A: A massive burst of solar plasma and magnetic field.

Q: What is a geomagnetic storm?
A: A disturbance of Earth's magnetosphere from solar activity.

Q: What causes auroras?
A: Charged particles from the Sun interacting with Earth's magnetic field and atmosphere.

Q: What is the Van Allen radiation belt?
A: Zones of energetic charged particles trapped by Earth's magnetic field.

Q: What is space debris?
A: Defunct human-made objects orbiting Earth.

Q: What is the Karman line?
A: The boundary of space, ~100 km above Earth's surface.

Q: What is a satellite?
A: Any object orbiting another; in everyday use, human-made spacecraft.

Q: What is geostationary orbit?
A: A 35,786 km circular orbit where satellites match Earth's rotation.

Q: What is low Earth orbit (LEO)?
A: Orbits up to ~2,000 km altitude, used by ISS and many satellites.

Q: What is the difference between LEO and GEO?
A: LEO is faster, lower; GEO is fixed over a point on Earth.

Q: What is a Lagrange point?
A: A stable position in a two-body gravity system where small objects can remain stationary relative to the bodies.

Q: Where is JWST located?
A: At Earth-Sun Lagrange point L2, about 1.5 million km from Earth.

Q: What is a rocket equation?
A: The Tsiolkovsky equation relating velocity to mass and exhaust velocity.

Q: What is delta-v?
A: A measure of the change in velocity needed for a spaceflight maneuver.

Q: What is gravity assist?
A: Using a planet's gravity to alter a spacecraft's trajectory and speed.

Q: What is the Voyager mission?
A: NASA spacecraft (Voyager 1 and 2, 1977) studying the outer planets and now in interstellar space.

Q: What is the farthest human-made object?
A: Voyager 1.

Q: What is the Curiosity rover?
A: NASA's Mars Science Laboratory rover, landed 2012.

Q: What is the Perseverance rover?
A: NASA's Mars rover landed 2021, exploring for past life and caching samples.

Q: What is the New Horizons mission?
A: NASA spacecraft that flew by Pluto in 2015.

Q: What is the Parker Solar Probe?
A: A NASA mission flying closer to the Sun than any prior spacecraft.

Q: What is the cosmic horizon?
A: The maximum distance from which light has had time to reach us.

Q: What is dark age in cosmology?
A: The period before the first stars formed.

Q: What is reionization?
A: The epoch when ultraviolet light from early stars/quasars reionized the neutral hydrogen.

Q: What is the Drake equation's "L"?
A: The expected lifetime of a communicating civilization.

Q: What is the Hubble Deep Field?
A: A long-exposure image revealing thousands of distant galaxies.

Q: What is the JWST Deep Field?
A: A similar deep image by JWST, capturing the early universe.

Q: What is the cosmological constant?
A: A constant in Einstein's equations representing energy density of empty space.

Q: Who introduced the cosmological constant?
A: Einstein, originally to allow a static universe; later called his "greatest blunder."

Q: What is the universe's geometry?
A: Observations suggest it is flat on large scales.

Q: What is the multiverse hypothesis?
A: The idea that our universe is one of many.

Q: What is anthropic principle?
A: The observation that physical constants must permit observers like us.

Q: What is a wormhole?
A: A theoretical spacetime shortcut connecting distant regions.

Q: What is the steady-state theory?
A: A discarded cosmology proposing the universe is unchanging on large scales.

Q: What ended steady-state theory's viability?
A: The CMB discovery, fitting the Big Bang model.