Office for Astronomy Outreach

100 hours of astronomy

100 Hours of Astronomy

Each year, the Office for Astronomy Outreach (OAO) organises 100 Hours of Astronomy, a global event that invites people of all ages and cultures to connect with the night sky and the science behind the stars. This event aims to spark scientific curiosity and bring astronomy to communities worldwide, from bustling cities to the most remote areas. Through public observation events, workshops, talks, and educational activities, 100 Hours of Astronomy facilitates shared experiences that inspire exploration of the Universe and encourage reflection on our place within it.

Since its inception during the International Year of Astronomy 2009, 100 Hours of Astronomy has shown that astronomy connects us to the stars and one another, becoming a universal celebration of knowledge and cooperation. By reminding us that we all look up at the same sky, we aim to foster community bonds, promote interest in scientific education, and cultivate a sense of global belonging. Anyone interested in engaging the public with astronomy can propose an event and join this international network, making 100 Hours of Astronomy a truly inclusive and collaborative celebration.

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100 Years of the Planetarium

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Planetariums have long been a source of inspiration for children and adults alike. In 1923, the first planetarium projector was invented in Jena, Germany, and two years later, the first planetarium opened its doors in Munich. Between 2023 and 2025, the world celebrates the centennial of the planetarium and the countless ways planetariums have impacted society. This year, the IAU Office for Astronomy Outreach (OAO) will team up with the International Planetarium Society (IPS) to continue the legacy of 100 Hours of Astronomy and celebrate 100 Years of the Planetarium!

With the increasing levels of light pollution worldwide, it is impossible to experience a truly dark sky in many places. Planetariums are then dark sky oases: sanctuaries for night sky enthusiasts, exposing the public to the Universe. Even in locations where skies are protected from city lights, planetariums are still powerful educational tools for understanding the Universe and our place within it. This year, we encourage everyone to visit their local planetarium—small, large, mobile, or stationary—and immerse themselves in the wonders of our Universe.

The OAO and IPS hope to activate planetariums worldwide to participate in this programme.

How to participate?

While the 2025 100 Hours of Astronomy theme is “100 Years of the Planetarium,” there are many ways to celebrate astronomy. Here’s how:


  1. Brainstorm ideas for an event with your community.
  2. Advertise your event on the OAO Astronomy Engagement Events Calendar.
  3. Tag the IPS and OAO in your social media posts using the hashtags#100HoursofAstronomy, #100YearsofthePlanetarium and #IAUOutreach!

This Year's Events and Activity Ideas

From 2 to 5 October 2025, the International Astronomical Union Office for Astronomy Outreach (IAU OAO) and the International Planetarium Society (IPS), two of the world's leading organisations dedicated to public engagement with astronomy, will team up to deliver a 100-hour marathon of astronomy events and activities dedicated to the 100th anniversary of the first planetarium.


The IAU OAO and IPS will host two main events during 100 Hours of Astronomy:
2 October: Big Astronomy, Big Aspirations100 Hours of Astronomy will begin with a 360° YouTube livestream of the planetarium show, Big Astronomy. This show highlights the diversity of people who work at some of the most important sites for modern astronomy and their careers. Ardis Herrold (Rubin Observatory) will follow with a talk entitled “The NSF-DOE Vera C. Rubin Observatory - The Transformative Years”, discussing the next generation of ground-based astronomy. All are welcome to join this hour-long online event and engage with speakers, creators and audiences worldwide! Exact times and details to come.
4 October: 24 Hours of PlanetariumsPlanetariums - large, small, mobile, stationary, and hand-made - are important cultural and educational centres for their communities. The OAO and IPS want to show the world the unique view from inside your planetarium and give you and your team global recognition. Planetariums are invited to sign up for our 24-hour continuous event that we will stream live from the Akashi Municipal Planetarium in Japan. Whether it be a quick hello with your audience or a longer message for the world, the OAO and IPS hope you will participate in this event to demonstrate the connection everyone has to understanding our place in the Universe. The organisations jointly aim to make this as high-impact and low-cost as possible, ensuring all planetariums can get involved.

OAO Outreach Activity Toolkit

This toolkit compiles crowdsourced astronomy engagement activities that can be implemented during one of the IAU Global Outreach Events.

We invite you to experiment with the featured activities and share your ideas by contributing to the Toolkit!

Share your event with the world

We encourage you to share your events and participate in this year’s 100 Hours of Astronomy! If your event is open to the public, please leave enough information for people to get involved—both in person and online!

While the 2025 100 Hours of Astronomy theme is “100 Years of the Planetarium,” the spirit of this programme is to bring people together through the awe astronomy inspires in us all. We hope people worldwide will spread their love for astronomy, whether under the dome or our shared sky!

The submissions must be written in English. If you cannot translate the information for your event, please use an online translator like Google Translate or DeepL.

Please note that we may copy-edit some content if needed.

Share your event with the world

OAO Astronomy Engagement Events Calendar

To highlight all the amazing activities happening around the globe, we will promote a calendar of events displayed on a world map and our social media channels.

More Information

All events must respect the general guidelines of the IAU Global Project and Themes, which promote the key role of astronomy for the betterment of science and society through collaboration and with a spirit of respect, tolerance, and peace.

If you need to change your events already on the calendar, please email the IAU Office for Astronomy Outreach Team via public@...Click to show with the subject line “100 Hours of Astronomy Calendar 2025 - Update”.If you cannot submit through this form, please email the IAU Office for Astronomy Outreach team via public@...Click to show with the subject line “100 Hours of Astronomy Calendar 2025 - Update”.