Overview
The Olimpíada Brasileira de Astronomia e Astronáutica (OBA) is held every year by the Sociedade Astronômica Brasileira (SAB) together with the Agência Espacial Brasileira (AEB). It is open to students in every year of Ensino Fundamental and Ensino Médio across Brazil, and abroad when the school teaches in Portuguese. The facts below are from the rules of the 29th edition, held in 2026.
Who can apply
Any student enrolled in a public or private school at these levels can take part. The school's registered teacher representative enrols students on the OBA platform. A student whose school is not registered may sit the exam at a nearby registered school with that school's consent. There is no minimum or maximum number of students per school.
Levels or stages
| Level | School years | Time allowed |
|---|---|---|
| Level 1 | Years 1 to 3 of Ensino Fundamental | Up to 2 hours |
| Level 2 | Years 4 and 5 of Ensino Fundamental | Up to 2 hours |
| Level 3 | Years 6 to 9 of Ensino Fundamental | Up to 2 hours |
| Level 4 | Any year of Ensino Médio | Up to 3 hours |
Exam pattern
The first phase is a written paper taken in person at the school, individually, with no calculator and no use of materials, people or the internet. It has, in principle, 7 questions on astronomy and 3 on astronautics. Answers go on an answer card that the teacher scans with a phone app.
Syllabus
Content follows what most school textbooks cover and grows with each level. Level 1 covers the Earth, Moon and Sun, the solar system, constellations, rockets and satellites, and Brazilian satellites. Level 2 adds galaxies, stars, light-years, the history of astronomy, the International Space Station and space telescopes. Level 3 adds Kepler's laws, brightness and magnitude, gravitation and the exploration of Mars. Level 4 adds the law of universal gravitation, Hubble's law, the electromagnetic spectrum, the Doppler effect, stellar evolution, escape velocity and satellite orbits.
Marking and results
Scores are ranked separately for each level. About 80,000 medals (gold, silver and bronze) are shared among the four levels for the highest scores, and every participant receives a certificate. Level 3 students in Year 9 scoring 9 or more, and Level 4 students scoring 7 or more, are invited to a second phase. The second phase is three online exams of about 20 multiple-choice questions each, then an in-person exam for about 200 students. About 50 students are then trained and the national teams are chosen for the International Olympiad on Astronomy and Astrophysics and the Latin American Olympiad.
Important dates
For 2026, the exam was set for 15 May 2026. Schools and students had to register by 1 May 2026, and papers were corrected and scores entered between 18 and 31 May 2026.
Fees
There is no registration fee for schools or students, and certificates and medals are free. Postage of the certificate package is shared: in 2026 a public school pays R$65 and a private school pays double.
How to apply
The school's teacher representative registers the school and students on the OBA platform at app.oba.org.br.
Preparation tips
Use textbook astronomy and past OBA papers from the official site.
At higher levels, practise short calculations without a calculator.
Is the OBA free?
Yes, there is no registration fee. Schools only share the postage cost for certificates and medals.
Can the OBA be taken at home?
No. In 2026 the exam could only be taken in person at school under supervision.