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OpenStem
@openstem · Joined Jul 2026
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Quiz5 questions
Which band of the electromagnetic spectrum carries the highest-energy photons?
ARadioBInfraredCGamma-rayDVisible light
Astronomy · L3 · The EM Spectrum in Astronomy
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Astronomy · L3 · The EM Spectrum in AstronomyQuiz5 questions
Why does every element produce its own unique pattern of spectral lines?
ABecause each element has a different colourBBecause each element's electrons can only occupy specific, fixed energy levelsCBecause elements absorb all wavelengths equallyDIt is random and has no physical cause
Astronomy · L3 · Spectroscopy & Redshift
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Astronomy · L3 · Spectroscopy & RedshiftQuiz5 questions
What holds up a neutron star against further gravitational collapse?
AOrdinary gas pressure from heatBNeutron degeneracy pressure, a quantum-mechanical effectCMagnetic repulsionDNothing — neutron stars are still collapsing
Astronomy · L3 · Black Holes & Neutron Stars
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Astronomy · L3 · Black Holes & Neutron StarsQuiz5 questions
What does it mean for a planet to be in its star's habitable zone?
AThe planet definitely has life on itBThe planet's orbital distance would allow liquid water to exist on its surface, given the right conditionsCThe planet is the same size as EarthDThe star is the same type as the Sun
Astronomy · L3 · Habitable Zones & the Search for Life
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Astronomy · L3 · Habitable Zones & the Search for LifeQuiz5 questions
A star has a parallax angle of 0.1 arcseconds. What is its distance, using d = 1/p?
A0.1 parsecsB1 parsecC10 parsecsD100 parsecs
Astronomy · L3 · The Cosmic Distance Ladder
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Astronomy · L3 · The Cosmic Distance LadderQuiz5 questions
What shapes Earth's magnetosphere into a compressed dayside and a long nightside tail?
AEarth's rotationBPressure from the solar windCThe Moon's gravityDCosmic ray bombardment
Astronomy · L3 · Aurora & Magnetosphere Physics
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Astronomy · L3 · Aurora & Magnetosphere PhysicsQuiz5 questions
In the giant-impact hypothesis, what is 'Theia'?
AThe name of the debris disk that formed the MoonBA Mars-sized protoplanet that collided with the young EarthCAn alternative name for the Moon itselfDA hypothetical planet beyond Neptune
Astronomy · L3 · Moon Formation & the Giant Impact
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Astronomy · L3 · Moon Formation & the Giant ImpactQuiz5 questions
Why are star clusters especially useful for testing stellar evolution theory?
ABecause every star in them is identicalBBecause all their stars share almost the same age and starting composition, differing mainly in massCBecause they contain no massive starsDBecause they never change over time
Astronomy · L3 · Star Clusters & Stellar Populations
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Astronomy · L3 · Star Clusters & Stellar PopulationsQuiz5 questions
What are cosmic rays mostly made of?
APhotons of visible lightBProtons, with smaller fractions of heavier nuclei and electronsCNeutrinos onlyDDust grains
Astronomy · L3 · Cosmic Rays & High-Energy Astrophysics
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Astronomy · L3 · Cosmic Rays & High-Energy AstrophysicsQuiz5 questions
What physical effect underlies gravitational lensing?
ALight is absorbed and re-emitted by massive objectsBMass curves spacetime, bending the path light followsCLight slows down near massive objects, changing colourDMagnetic fields deflect photons
Astronomy · L3 · Gravitational Lensing
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Astronomy · L3 · Gravitational LensingQuiz5 questions
What are the three stages of impact crater formation, in order?
AExcavation, contact and compression, modificationBContact and compression, excavation, modificationCModification, excavation, contact and compressionDCompression, ejection, vaporisation
Astronomy · L3 · Asteroid Impacts & Craters
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Astronomy · L3 · Asteroid Impacts & CratersQuiz5 questions
How did Ptolemy's geocentric model account for planets appearing to move backward (retrograde motion)?
ABy assuming Earth also orbits the planetsBBy adding small circular loops called epicycles on top of the main orbitsCBy ignoring retrograde motion entirelyDBy placing the Sun at the centre
Astronomy · L3 · History of Astronomy: Paradigm Shifts
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Astronomy · L3 · History of Astronomy: Paradigm ShiftsQuiz5 questions
What is a hot Jupiter?
AA rocky planet with a thick, superheated atmosphereBA gas giant orbiting very close to its star, with a period of only daysCA giant planet ejected from its system entirelyDA planet with an unusually hot, molten core
Astronomy · L3 · Exosolar System Architecture
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Astronomy · L3 · Exosolar System ArchitectureQuiz6 questions
Why does a collapsing cloud spin faster as it shrinks?
ABecause gravity directly speeds up rotationBBecause angular momentum L = Iω is conserved as the moment of inertia I decreasesCBecause the cloud heats upDIt doesn't — the spin rate stays constant
Astronomy · L3 · Solar System Formation Quiz
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Astronomy · L3 · Solar System Formation QuizQuiz7 questions
What is right ascension the sky's analogue of?
AAltitudeBLongitudeCLatitudeDAzimuth
Astronomy · L3 · Celestial Coordinates & Precession
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Astronomy · L3 · Celestial Coordinates & PrecessionQuiz7 questions
Why are giant molecular clouds the only interstellar clouds able to collapse into stars?
AThey are the only clouds containing any hydrogen at allBThey are cold and dense enough that gravity can overcome the gas's internal pressureCThey are the only clouds located near existing starsDThey are heated by nearby supernovae, which triggers fusion directly
Astronomy · L3 · Star Formation & Molecular Clouds
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Astronomy · L3 · Star Formation & Molecular CloudsQuiz7 questions
What are planetary rings physically made of?
AA single solid, continuous sheet of iceBCountless individual particles, mostly ice, each independently orbiting the planetCCompressed gas trapped by the planet's magnetic fieldDA thin layer of the planet's own atmosphere
Astronomy · L3 · Planetary Ring & Moon Systems
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Astronomy · L3 · Planetary Ring & Moon SystemsQuiz7 questions
What causes an emission nebula to glow?
AIt reflects starlight off its dust grainsBUltraviolet radiation from nearby hot stars ionises its gas, which then emits light as electrons recombineCIt is heated by cosmic ray bombardment aloneDIt glows from residual heat left over from the Big Bang
Astronomy · L3 · Nebula Types
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Astronomy · L3 · Nebula TypesQuiz11 questions
According to Kepler's third law, a planet with an orbital semi-major axis of 4 AU (from the Sun) has an orbital period of:
A4 yearsB8 yearsC16 yearsD64 years
Astronomy · L4 · Astronomy Science — 10 Q
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Astronomy · L4 · Astronomy Science — 10 QQuiz4 questions
The vis-viva equation v² = GM(2/r − 1/a) shows that, for a fixed semi-major axis a, orbital speed v is:
AConstant everywhere along the orbitBLargest when r is smallest (near periapsis)CLargest when r is largest (near apoapsis)DIndependent of r entirely
Astronomy · L4 · Orbital Mechanics: Vis-Viva & Hohmann Transfers — 4 Q
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Astronomy · L4 · Orbital Mechanics: Vis-Viva & Hohmann Transfers — 4 QQuiz4 questions
Tidal acceleration across a body of radius R at distance d from a mass M scales as:
AGM/d²B2GMR/d³CGMR²/d⁴DIt does not depend on d
Astronomy · L4 · Tidal Forces, Roche Limit & Tidal Locking — 4 Q
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Astronomy · L4 · Tidal Forces, Roche Limit & Tidal Locking — 4 QQuiz4 questions
According to the Stefan-Boltzmann law, if a star's temperature doubles while its radius stays the same, its luminosity increases by a factor of:
A2B4C8D16
Astronomy · L4 · Blackbody Radiation & Stellar L-R-T — 4 Q
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Astronomy · L4 · Blackbody Radiation & Stellar L-R-T — 4 QQuiz4 questions
The equation of hydrostatic equilibrium, dP/dr = −Gm(r)ρ(r)/r², describes a balance between:
ANuclear fusion rate and neutrino emissionBThe outward push of the pressure gradient and the inward pull of gravityCMagnetic pressure and radiation pressureDRotation and tidal forces
Astronomy · L4 · Stellar Structure Equations — 4 Q
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Astronomy · L4 · Stellar Structure Equations — 4 QQuiz4 questions
If a galaxy's visible mass were the only mass present, the naive Keplerian expectation is that orbital velocity at large radius should:
AStay perfectly flatBIncrease linearly with radiusCDecline as 1/√rDDrop to zero abruptly
Astronomy · L4 · Galactic Dynamics & Dark Matter — 4 Q
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Astronomy · L4 · Galactic Dynamics & Dark Matter — 4 QQuiz4 questions
A star shows a parallax angle of 0.05 arcseconds. What is its distance?
A0.05 parsecsB5 parsecsC20 parsecsD200 parsecs
Astronomy · L4 · The Cosmic Distance Ladder, Quantitatively — 4 Q
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Astronomy · L4 · The Cosmic Distance Ladder, Quantitatively — 4 QQuiz4 questions
Einstein's equivalence principle states that:
AMass and energy are always exactly equalBThe effects of gravity are locally indistinguishable from the effects of uniform accelerationCAll observers everywhere measure the same gravitational fieldDLight and matter always travel at the same speed
Astronomy · L4 · General Relativity Basics — 4 Q
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Astronomy · L4 · General Relativity Basics — 4 QQuiz4 questions
Transmission spectroscopy detects an exoplanet's atmospheric composition by measuring:
AThe planet's total mass from its orbital wobbleBHow transit depth varies with wavelength, revealing wavelength-dependent atmospheric absorptionCThe planet's rotation period from its day-night temperature differenceDThe colour of reflected starlight only, with no wavelength dependence
Astronomy · L4 · Exoplanet Atmospheres & the Habitable Zone — 4 Q
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Astronomy · L4 · Exoplanet Atmospheres & the Habitable Zone — 4 QQuiz4 questions
By mass, the interstellar medium is composed mostly of:
ADust grains, with a small amount of gasBGas (mostly hydrogen), with dust making up only about 1% by massCEqual parts gas and dustDHeavy elements like iron and gold
Astronomy · L4 · The Interstellar Medium — 4 Q
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Astronomy · L4 · The Interstellar Medium — 4 QQuiz4 questions
An active galactic nucleus is powered primarily by:
ANuclear fusion in a dense cluster of young starsBGravitational energy released as matter accretes onto a supermassive black holeCCollisions between galaxy clustersDRadioactive decay of heavy elements in the galactic core
Astronomy · L4 · Active Galactic Nuclei & Quasars — 4 Q
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Astronomy · L4 · Active Galactic Nuclei & Quasars — 4 QQuiz4 questions
Recombination refers to the epoch when:
AGalaxies first formedBFree electrons combined with protons to form neutral hydrogen atomsCThe first stars ignitedDDark energy began to dominate the universe's expansion
Astronomy · L4 · The Cosmic Microwave Background — 4 Q
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Astronomy · L4 · The Cosmic Microwave Background — 4 Q