16 articles · five interactive Labs · English and Chinese
How we learned to read the universe
Follow balloon flights, radio pulses, the microwave sky and distant stars to the discoveries that changed astronomy, cosmology and gravity.
A balloon rises, and the radiation grows stronger. A radio trace repeats with uncanny regularity. A distant explosion looks too faint. Each discovery begins with something astronomers could actually measure. Choose the puzzle that catches your attention, then follow the observations to the idea they changed.
Try a measurement yourself
CMB Spectrum Thermometer
How can a small foreground make a precise cosmic thermometer read too warm?
CMB Sky and Angular Power
Why does a broad telescope beam remove small sky patterns before large ones?
Supernova Distance and Cosmic Expansion
How do distant supernovae reveal the history of cosmic expansion?
Inside a Star in Hydrostatic Balance
What holds a star up against its own gravity?
Pulsar Timing and Orbital Decay
How can pulse arrival times reveal an orbit that slowly shrinks?
Stars and new windows on the sky
What reaches us from above the atmosphere, and what holds a star up?
Why a white dwarf has a maximum mass
How did Chandrasekhar show that some stellar remnants cannot remain white dwarfs?
A rocket found an unexpectedly bright X-ray sky
How did a few minutes above the atmosphere reveal a new kind of astronomical source?
Hess found stronger radiation above the clouds
How did a balloon flight show that some radiation reaches us from space?
Learning to read radio signals
Build an image from separated antennas, then listen for a spinning star.
The regular pulses Jocelyn Bell refused to discard
How did marks on a paper chart reveal a new kind of star?
How Ryle built a large radio telescope from smaller ones
How can a few antennas spread over time reveal the shape of a radio galaxy?
Measuring the history of expansion
The microwave background and distant supernovae preserve different chapters of cosmic history.
COBE compared the sky with a laboratory blackbody
How did a cold reference aboard a satellite test the thermal origin of the cosmic microwave background?
The small temperature differences in COBE’s sky
How did a nearly uniform microwave sky reveal the beginnings of cosmic structure?
From an almost smooth sky to a universe full of galaxies
How did physical cosmology connect the early microwave background with the later distribution of galaxies?
The microwave hiss that remained after the antenna was checked
Why did a few unexplained degrees in a radio receiver become evidence for a hot early universe?
Distant supernovae showed that cosmic expansion had accelerated
Why did supernovae that looked unexpectedly faint change the inferred history of cosmic expansion?
A planet moves its star
A small motion of a star can reveal an unseen companion.
The four-day year of 51 Pegasi b
How did a star’s small wobble reveal a giant planet in an unexpectedly tight orbit?
Gravity leaves a trace
Follow a changing orbit, a passing wave and the stars around an unseen mass.
The stars that weighed the Milky Way’s dark centre
How can the motions of visible stars reveal a central object that the telescope cannot see directly?
A pulsar clock revealed an orbit losing energy
How did radio pulses reveal gravitational radiation long before a detector on Earth caught a wave?
The short rising signal that reached both LIGO detectors
How did a fraction of a second of changing light reveal two merging black holes?
Why collapse does not need a perfectly spherical star
What did Penrose prove when he showed that gravitational collapse survives departures from perfect symmetry?
Read the GW150914 paper from the traces to the masses
Which parts of the discovery paper establish the signal, its significance and its source properties?
Find a Nobel contribution
The names below identify the awarded contribution. Each story also names the wider team and the people who made the discovery possible.
1936 · Victor F. Hess
Hess found stronger radiation above the clouds
Official award1974 · Martin Ryle · Antony Hewish
How Ryle built a large radio telescope from smaller ones
Official award1978 · Arno Penzias · Robert Wilson
The microwave hiss that remained after the antenna was checked
Official award1983 · Subrahmanyan Chandrasekhar
Why a white dwarf has a maximum mass
Official award1993 · Russell Hulse · Joseph Taylor
A pulsar clock revealed an orbit losing energy
Official award2002 · Riccardo Giacconi
A rocket found an unexpectedly bright X-ray sky
Official award2006 · John Mather · George Smoot
COBE compared the sky with a laboratory blackbody
Official award2011 · Saul Perlmutter · Brian Schmidt · Adam Riess
Distant supernovae showed that cosmic expansion had accelerated
Official award2017 · Rainer Weiss · Barry Barish · Kip Thorne
The short rising signal that reached both LIGO detectors
Official award2019 · James Peebles
From an almost smooth sky to a universe full of galaxies
Official award2019 · Michel Mayor · Didier Queloz
The four-day year of 51 Pegasi b
Official award2020 · Roger Penrose
Why collapse does not need a perfectly spherical star
Official award2020 · Reinhard Genzel · Andrea Ghez
The stars that weighed the Milky Way’s dark centre
Official award
A discovery comes before its prize
These are milestones, not a claim that an entire field began in one year. Radio synthesis, stellar theory and physical cosmology grew through many contributions.
- 1912 · Hess finds stronger ionization high above the ground
- 1931 · Chandrasekhar calculates a white-dwarf mass limit
- 1960 · Ryle and Hewish publish their aperture-synthesis method
- 1962 · A rocket detects an extrasolar X-ray source
- 1965 · The microwave-background discovery papers appear
- 1965 · Penrose proves a singularity theorem without spherical symmetry
- 1967 · Bell finds the repeating radio signal
- 1974 · Hulse and Taylor discover a binary pulsar
- 1982 · Peebles calculates fluctuations in a cold-dark-matter model
- 1990 · FIRAS reports its first cosmic blackbody spectrum
- 1992 · DMR reports large-scale microwave anisotropy
- 1995 · Mayor and Queloz report 51 Pegasi b
- 1998 · Distant supernovae point to accelerated expansion
- 2002 · A near-complete S2 orbit constrains the central mass
- 2015 · LIGO observes GW150914
Terms as you need them
- Redshift
- Light arrives at longer wavelengths after cosmic expansion stretches it.
- Luminosity distance
- The distance that relates an object’s total light output to its observed brightness.
- Blackbody spectrum
- The pattern of thermal brightness across frequencies, set by temperature.
- Anisotropy
- A quantity differs with the direction in which we look.
- Angular power spectrum
- How sky-temperature variations are distributed among angular scales.
- Visibility
- An antenna pair measures one component of the sky’s spatial pattern.
- Pulsar
- A spinning neutron star whose beam sweeps past Earth repeatedly.
- Timing residual
- The difference between an observed arrival time and the time a model predicts.
- Hydrostatic equilibrium
- The outward pressure gradient balances inward gravity.
- Chirp
- A wave whose frequency rises as two orbiting objects approach each other.
- Trapped surface
- A closed surface for which both future-directed perpendicular light fronts converge.
- Minimum companion mass
- Radial velocities constrain mass together with the unknown orbital inclination.