According to the Hubble–Lemaître law, what is generally true of more distant galaxies?
A They stop moving
B They recede faster on average
C They orbit Earth faster
D They become stars
On large scales, galaxies farther away generally have greater recession speeds because space is expanding.
What does the Hubble constant describe?
A The age of the Sun
B The rotation speed of Earth
C The present expansion rate of the Universe
D The brightness of the Moon
The Hubble constant relates galaxy recession speed to distance and describes the Universe’s present expansion rate.
Which kind of stellar explosion is used as a standard candle for distant galaxies?
A Meteor shower
B Solar flare
C Type Ia supernova
D Planetary eclipse
After calibration, Type Ia supernovae have a useful known intrinsic brightness and help estimate distances.
What key property makes an object a standard candle?
A It has a fixed orbit
B It emits only radio waves
C It never changes position
D Its intrinsic brightness is known
If its true brightness is known, astronomers can compare it with observed brightness to estimate distance.
What does apparent magnitude describe?
A How bright an object looks from Earth
B The object’s mass
C Its true size
D Its distance in light-years
Apparent magnitude measures how bright a celestial object appears to an observer.
What does absolute magnitude describe?
A Intrinsic brightness at a standard distance
B Brightness through Earth’s clouds
C The length of an orbit
D The age of a galaxy
Absolute magnitude compares intrinsic brightness using a standard distance of 10 parsecs.
What is the cosmic web?
A A ring around the Solar System
B The large-scale network of galaxies and matter
C A pattern of stars in one constellation
D A cloud inside the Sun
Galaxies and matter form a large-scale network of filaments, dense regions, and vast voids.
What is a cosmic filament?
A A beam from a black hole
B A ring around a planet
C A long thread-like structure in the cosmic web
D A single star’s outer layer
Cosmic filaments are long structures that connect denser galaxy-rich regions.
What is a cosmic void?
A A region filled only with stars
B A hole inside a planet
C A dark spot on the Sun
D A very sparse region between dense structures
Cosmic voids contain far fewer galaxies than the denser filaments and clusters around them.
What is a galaxy supercluster?
A A single giant star
B A group of moons
C A very large collection of galaxy groups and clusters
D A cloud of dust around a comet
A supercluster is a large-scale association containing many galaxy groups and clusters.
What does cosmic inflation refer to?
A A very rapid expansion in the early Universe
B The growth of a star into a giant
C A galaxy spinning faster
D The expansion of Earth’s atmosphere
Inflation is the name for a proposed period of extremely rapid expansion very early in cosmic history.
What happened during the epoch of recombination?
A The first planets formed around the Sun
B All stars stopped shining
C Electrons joined nuclei to form neutral atoms
D Black holes disappeared
As the early Universe cooled, electrons joined nuclei; light could then travel much more freely.
What did Big Bang nucleosynthesis mainly produce?
A Light atomic nuclei
B Large planets
C Modern galaxies
D Black holes
During the first minutes, the hot early Universe formed light nuclei, especially hydrogen and helium.
What do the tiny temperature variations in a cosmic microwave background map represent?
A The changing seasons on Earth
B The surface of the Sun
C Signals from modern satellites
D Small early differences that seeded later structure
Small early density variations in the CMB grew into the structures that later formed galaxies.
What does the cosmological principle say about the Universe on very large scales?
A It is broadly uniform in all directions and locations
B It has one central planet
C Every galaxy is identical
D All stars are the same age
The cosmological principle treats the Universe as broadly homogeneous and isotropic on sufficiently large scales.
What are baryon acoustic oscillations?
A Pulses from rotating neutron stars
B Waves in a planet’s rings
C A scale pattern left by sound waves in the early Universe
D Bright lines from a comet
Early-universe sound waves left a characteristic scale in how galaxies are distributed.
Which description best fits an elliptical galaxy?
A A smooth, rounded or oval shape
B A perfect ring of planets
C A straight line of stars
D A cloud with no stars
Elliptical galaxies usually look smooth and rounded or oval rather than showing prominent spiral arms.
What does “irregular galaxy” mean?
A It contains only one star
B It has no clear spiral or elliptical shape
C It has no gravity
D It is smaller than every planet
An irregular galaxy lacks the well-defined overall shape seen in spiral and elliptical galaxies.
What is an active galactic nucleus (AGN)?
A A new planet outside a galaxy
B A bright, energetic region at a galaxy’s center
C A quiet group of stars
D A dark cloud between planets
An AGN is a highly energetic central region, commonly powered by matter around a supermassive black hole.
What feature is often found in a powerful radio galaxy?
A A tail of ice
B A solid surface
C Large radio-emitting lobes or jets
D A ring of asteroids
Some active galaxies send powerful jets that create large radio-emitting regions beyond the galaxy’s center.
What kind of radiation does a radio telescope collect?
A Radio waves
B Visible light only
C X-rays only
D Sound waves
Radio telescopes detect radio waves arriving from objects in space.
Why are X-ray telescopes usually placed above Earth’s atmosphere?
A The atmosphere absorbs most cosmic X-rays
B X-rays cannot travel through space
C Earth has no gravity
D X-rays only come from the Moon
Earth’s atmosphere blocks most incoming X-rays, so astronomers observe them from space or high altitudes.
Why is infrared astronomy useful for studying dusty star-forming regions?
A Dust creates visible sound
B Infrared light can pass through some dust
C Infrared light stops gravity
D Dust reflects all infrared light
Infrared observations can reveal cooler objects and regions hidden by dust in visible light.
What does adaptive optics correct in ground-based telescope images?
A The orbit of a planet
B A star’s real temperature
C The distance to the Moon
D Blurring caused by Earth’s atmosphere
Adaptive optics adjusts for atmospheric distortion that would otherwise blur telescope images.
What is a light curve?
A A map of a galaxy’s shape
B A path followed by a comet
C A picture of a star’s surface
D A graph of an object’s brightness over time
A light curve shows how an object’s measured brightness changes over time.
What does a galaxy rotation curve plot?
A Temperature against star color
B Orbital speed against distance from the galaxy’s center
C Brightness against age
D Mass against number of planets
A rotation curve shows how orbital speeds change with distance from a galaxy’s center.
What is the intergalactic medium?
A Gas inside a star
B Dust on a planet’s surface
C The Sun’s outer atmosphere
D Diffuse matter in the space between galaxies
The intergalactic medium is the thin gas and plasma found between galaxies.
What is a galaxy merger?
A Two stars becoming one planet
B A comet entering a planet’s orbit
C Two galaxies gradually combining through gravity
D A telescope joining two images
Gravity can draw two galaxies together; over time their stars and gas become part of a merged system.
Which description best fits a dwarf galaxy?
A A planet with a ring
B A small star cluster inside the Sun
C A galaxy with no matter
D A comparatively small galaxy with fewer stars
Dwarf galaxies are much smaller and contain fewer stars than large galaxies such as the Milky Way.
What does “cosmic dawn” refer to?
A The start of each Earth day
B The era when the first stars and galaxies began to appear
C The birth of the Solar System
D The first sunrise on Mars
Cosmic dawn is the period when the first stars and galaxies formed in the early Universe.