IAO — International Astronomy Olympiad
The oldest international astronomy olympiad, founded in 1996 and held mostly across Eurasia. Students compete in junior and senior age groups through theoretical, practical and observational rounds.
- Founded
- 1996
- Host rotation
- Annual, rotating host city (mostly Eurasia)
- Level
- International (secondary school, junior & senior groups)
- Format
- Theoretical, practical and observational rounds in two age groups
- Rounds
- Theoretical round, practical round, observational round
- Eligibility
- Secondary-school students split into a junior group (14–15) and a senior group (16–18)
- Website
- www.issp.ac.ru/iao
Notable facts
Unlike the IOAA, the IAO keeps a strong emphasis on classical astronomy, celestial mechanics and real-night-sky observing. It directly inspired the creation of the IOAA in 2007.
Recent editions
| Year | Host |
|---|---|
| 2024 | Nepal |
| 2023 | Sirius, Russia |
| 2022 | Matera, Italy |
Typical topics
Past problems
2025
Duration of totality
During a total solar eclipse the Moon's umbral shadow sweeps the Earth's surface at a supplied speed relative to an equatorial observer. Using the given umbral diameter and shadow velocity, estimate the maximum duration of totality and explain why real eclipses fall short of it.
Show solution
Divide the umbral diameter by the shadow's ground speed: t = D_umbra/v_shadow. For a 250 km umbra moving at about 0.55 km/s relative to an equatorial observer, t ≈ 455 s ≈ 7.6 min — the theoretical ceiling near 7.5 min. Real eclipses fall short because the umbra is usually smaller than its maximum (Moon not at perigee, Earth not at aphelion) and observers are rarely on the centre line near the equator where the geometry is most favourable.
Classifying a supernova light curve
Students receive 200 days of magnitudes for an unknown supernova together with template light curves. By comparing rise time, peak magnitude, and decline rate, classify the event as Type Ia or core-collapse and justify the identification.
Show solution
Overlay the observed magnitudes on each template and compare rise time, peak magnitude and post-maximum decline. A Type Ia rises in ~20 d and then fades smoothly at ≈0.1 mag/day in B, powered by ⁵⁶Co decay, with no plateau. The measured curve matches the Ia template: fast rise, smooth decline, no hydrogen-plateau phase. Core-collapse templates instead show a ~100 d plateau (II-P) or a broader, lumpier maximum — so the event is classified as Type Ia.
2024
Angular size of a lunar crater
A lunar crater 90 km in diameter is observed at a geocentric distance of 380 000 km. Calculate its angular diameter in arcminutes and decide whether a telescope resolving 1 arcsecond can reveal structure within the crater rim.
Show solution
The small-angle formula gives θ = D/d = 90/380 000 ≈ 2.37 × 10^−4 rad ≈ 0.0136° ≈ 0.81 arcmin ≈ 49″. A 49″ feature spans about 49 resolution elements for a 1″-limited telescope. Structure within the rim — terraces and central peaks a few kilometres across, subtending several arcseconds — is therefore easily resolved.
Circumpolar constellations at 45° N
Using an unaided-eye sky chart set for local midnight, identify which of the listed constellations are circumpolar from the observing site and estimate the altitude of Polaris above the northern horizon.
Show solution
Polaris stands at an altitude equal to the site's latitude, so h ≈ 45° above the northern horizon. A star or constellation is circumpolar when its declination satisfies δ > 90° − φ = 45°. Checking each listed constellation against the chart, those lying entirely within 45° of the north celestial pole — for example Ursa Minor, Cassiopeia and most of Draco — never set from this site.