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Physithon - Astrophysics & Space | LearningFirst

Last revised May 21, 2026

Physithon - Astrophysics & Space

Stellar physics, black holes, the expanding universe, gravitational waves, and exoplanet detection — the working physics behind modern astrophysics.

Journey through the cosmos — from stellar physics and nuclear fusion in stars, to galaxy formation, large-scale cosmic structure, and modern cosmology. This collection covers stellar evolution and the Hertzsprung-Russell diagram, black holes and neutron stars, the expanding universe and dark energy, observational techniques (telescopes, spectroscopy, gravitational wave detection), and planetary science including exoplanet detection methods. Built for aspiring physicists preparing for advanced competitions.

Academic primerPhysics olympiad prep

Earn2CreditsinPhysics

5Modules14Sessions177Cards57Quizzes

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Certificates, credits, and a record of your progress.

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2 base learning credits

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Modules in this Collection’s System

One session. One clear takeaway.Each short session develops one distinct idea with a clear takeaway. Together, the sessions show how those ideas connect into a structured understanding of the topic.

Stellar Physics and Evolution

Stellar fusion (pp chain, CNO cycle), the Hertzsprung-Russell diagram, stellar evolution, and the death pathways into white dwarfs, neutron stars, and black holes.

4Sessions

Galaxies and Large-Scale Structure

Galaxy formation, dark matter halos, large-scale cosmic structure, and the cosmic web — how matter organizes itself across cosmic time.

3Sessions

Cosmology

The Big Bang, inflation, the cosmic microwave background, dark energy, and the ΛCDM model — the modern story of cosmic origins and fate.

3Sessions

Observational Techniques

Telescopes across the electromagnetic spectrum, gravitational wave detectors (LIGO/Virgo), and the multi-messenger astronomy era they enabled.

2Sessions

Planetary Science and Space Exploration

Planetary science, exoplanet detection methods (transit, radial velocity, direct imaging), and the search for habitable worlds beyond the solar system.

2Sessions

What You'll Walk Away With

1HR diagram reference mapping main sequence, giants, supergiants, and white dwarfs to luminosity and temperature with evolutionary tracks indicated
1stellar evolution flow chart tracing low-mass and high-mass star paths from protostar through main sequence to final remnant (white dwarf, neutron star, or black hole)
1cosmology timeline card from inflation through CMB recombination through structure formation through dark energy domination — with the key observational evidence at each stage
1observational techniques comparison — optical, radio, X-ray, gamma-ray, and gravitational wave — on what each window observes and what physics it reveals
1exoplanet detection methods atlas covering transit, radial velocity, direct imaging, gravitational microlensing, and astrometry — with the bias each method introduces

You'll Have Answers To

?How does a star's mass determine its luminosity, lifetime, and final remnant — and why does the mass-luminosity relation work?
?What does the no-hair theorem actually claim about black holes, and how have observations tested it?
?How did Hubble's law, Type Ia supernovae, and the CMB combine to establish that the universe is expanding and accelerating?
?What does each electromagnetic and gravitational-wave window reveal about astrophysics that the others can't?
?Why has the transit method (Kepler, TESS) found so many more exoplanets than radial velocity or direct imaging?

Critical Concepts Explored

Stellar fusion: pp chain and CNO cycleHertzsprung-Russell diagramStellar evolution and main-sequence lifetimeWhite dwarfs, neutron stars, black holesSchwarzschild radius and event horizonHubble's law and cosmic expansionCosmic microwave background (CMB)Dark matter and dark energyTelescope spectrum: optical to gravitational waveExoplanet detection: transit, radial velocity, direct imaging

Editor's Note

“Modern astrophysics taught with the math and the wonder”

This collection covers the modern astrophysical canon at competition rigor — stellar fusion mechanics, the H-R diagram as a working tool, black hole physics with the actual metrics, cosmology from CMB to dark energy, and the observational techniques (Hubble, JWST, LIGO, Kepler) that produced the evidence. Genuinely Physithon-grade and refreshingly devoid of pop-cosmology hand-waving.

Editor's Brief

Who it's for: Physithon and physics olympiad students preparing for astronomy and astrophysics rounds, plus advanced high-school and early-undergraduate students looking for an integrated treatment of stellar physics, cosmology, and observational astronomy.
What stands out: The collection treats observational astronomy as physics, not history — every technique is introduced alongside the physical principle it exploits and the discoveries it enabled.
Read if: You want to understand black holes, dark energy, and exoplanets at the level of the underlying physics — not the documentary version, not the equations divorced from the observations.

Gold Quotes

A star's mass determines essentially everything about its life and death — luminosity, lifetime, evolutionary path, and final remnant. The mass-luminosity relation is one of the most powerful compressions in physics.

L ∝ M³·⁵ on the main sequence; lifetime t ∝ M/L ∝ M⁻²·⁵. A 10 M☉ star burns 1000× brighter and lives 1/300th as long as the Sun. Mass also determines the death pathway: <0.5 M☉ → red dwarf → helium white dwarf; 0.5-8 M☉ → red giant → planetary nebula → CO white dwarf; >8 M☉ → core-collapse supernova → neutron star or black hole.

A black hole is fully characterized by three numbers — mass, charge, and angular momentum. The no-hair theorem is one of general relativity's strongest claims and has been observationally tested through gravitational-wave inspiral signatures.

The Schwarzschild radius r_s = 2GM/c² marks the event horizon — the boundary inside which no signal can escape. Sagittarius A* (4 million M☉) at our galactic center has r_s ≈ 12 million km. The 2017 Event Horizon Telescope image of M87's central black hole confirmed event-horizon-scale physics aligned with general relativity's predictions to a few percent.

The cosmic microwave background is the most precise measurement in cosmology — 2.725 K blackbody radiation with tiny anisotropies (1 part in 100,000) that seeded every galaxy in the observable universe.

WMAP and Planck mapped CMB anisotropies in detail, fitting the ΛCDM cosmological model: ~5% baryonic matter, ~26% dark matter, ~69% dark energy. The acoustic peaks in the CMB power spectrum encode the geometry of the universe (flat to within 0.4%), the Hubble constant, and the seed conditions for galaxy formation. JWST observations are now testing predictions about the earliest galaxies.

About the Curator

AAcademic Marathon

Academic Marathon is the editorial voice behind LearningFirst's Physithon and Biothon competition-prep collections — producing rigorous, mathematically grounded primers across the cutting-edge sub-disciplines of physics and biology that competition-track high-school students need to know.