IOAA-Junior — International Olympiad on Astronomy and Astrophysics for Juniors
The junior branch of the IOAA, created for students under 16. It mirrors the senior format with gentler difficulty and has run annually since 2022.
- Founded
- 2022
- Host rotation
- Annual, rotating host country
- Level
- International (under 16)
- Format
- Theory, data-analysis and observation rounds adapted for younger students
- Rounds
- Theoretical exam, data-analysis exam, observational exam, team competition
- Eligibility
- Students under 16 on 31 December of the competition year; selected by national teams
- Website
- ioaastrophysics.org/junior-ioaa
Notable facts
The first edition was hosted in Suceava, Romania in 2022. Several IOAA-Jr medalists go on to compete at the senior IOAA a few years later.
Recent editions
| Year | Host |
|---|---|
| 2025 | Piatra-Neamț, Romania |
| 2024 | Kathmandu, Nepal |
| 2023 | Volos, Greece |
| 2022 | Suceava, Romania |
Typical topics
Bright stars & constellationsSolar system & planetary motionPhases of the Moon & eclipsesMagnitudes & brightnessTelescopes & observing basicsElementary celestial mechanics
Past problems
2024
Reading a sundial at noon
At local noon on an equinox a vertical gnomon casts a shadow 0.7 times its own height. Determine the Sun's altitude at noon and deduce the latitude of the observing site.
Show solution
For a vertical gnomon of height h, the shadow length s = h/tan(a) where a is the Sun's altitude. With s = 0.7 h we get tan a = 1/0.7 ≈ 1.43, hence a ≈ 55°. At local noon on an equinox the Sun's declination is 0°, so a = 90° − φ and the latitude is φ = 90° − 55° = 35°.