100 hours of astronomy

100 Hours of Astronomy

100 Hours of Astronomy is a yearly global celebration organised by the Office for Astronomy Outreach (OAO) that invites people of all ages and backgrounds to come together and connect with the night sky — and with the science that helps us understand it.

From vibrant cities to the most remote corners of the world, this event brings astronomy closer to communities everywhere. Through public stargazing, workshops, talks, and hands-on educational activities, 100 Hours of Astronomy sparks curiosity, encourages shared exploration of the cosmos, and invites us all to reflect on our place in the Universe.

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Everyone, from amateur astronomers to educators and enthusiasts, is invited to propose an event and take part in this global celebration of the night sky.

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100 Years of the Planetarium

Planetariums have long been a source of inspiration for children and adults alike. 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 threat of satellite trails and light pollution to our skies, planetariums are dark sky oases: sanctuaries for night sky enthusiasts, exposing the public to the Universe.

Even in locations where the night sky is protected from city lights, planetariums can be a powerful educational tool 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.

Getting involved is easy!

How can you be part of a global event?

There are different ways to be involved:


  1. Apply to become a Regional Node.
  2. Plan a special event during 100 Hours of Astronomy.
  3. Assist to a pre-existing event close to you.
  4. Promote all events alongside 100 Hours of Astronomy using the hashtag #100HoursOfAstronomy!
Promotional graphic for participating in 100 Hours of Astronomy

We encourage you to share your events and participate in this year's 100 Hours of Astronomy!

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.

IPS

The IAU OAO and IPS will host two main events during 100 Hours of Astronomy:

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.
100 hours of astronomy
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.

Join the Global Celebration of 100 Hours of Astronomy!

From October 2 to 5 2025, people around the world will come together for 100 hours of continuous astronomy: a global celebration of the night sky and the science that helps us understand it. Through public stargazing, talks, workshops, and educational activities, we’ll share the beauty of the cosmos and reflect on our place in the Universe.


This year, our main hub will be the Akashi Municipal Planetarium in Japan, an historic site located exactly on the 135° East meridian, where Japan Standard Time is measured. It is a fitting place to mark this global moment under the stars!


In addition to our main hub, we have Community Nodes around the world. These are local contact points where you can get support, ask questions, and join ongoing activities near you.


Whether you're organising a big public event or a small online session, you’re part of something bigger. Let’s connect across borders and time zones to celebrate the power of astronomy, together.


Be part of the global movement, register your event today!

Akashi Municipal Planetarium

Plan a public astronomy event

Be part of the global 100 Hours of Astronomy 2025! ✨

100 Hours of Astronomy is a worldwide celebration where everyone — from astronomy clubs to schools and enthusiasts — organises public events to share the beauty of the night sky.

From 2 to 5 October, join this global movement with your own public or online activity!


How to participate:

  • To help you plan and advertise your event, download the 100 Hours of Astronomy Box, which includes graphics, logos, science and activity resources, and more!
  • Organise an astronomy event — big or small, in person or online — any time from 2 to 5 October.
  • Register your event between 1 August and 15 September on our official form.
  • Share your event details so people can easily join — both locally and online.

Registered events will appear on our global calendar and interactive map, and we’ll help promote them on social media. If you share photos, your activity could reach thousands worldwide!

This year’s theme is “100 Years of the Planetarium”, but any astronomy event that brings people together under the stars is welcome.

Register your event

Don't forget:

  • ✔ Event details must be in English — you can use tools like Google Translate or DeepL.
  • ✔ Use the hashtags #100HoursOfAstronomy and #IAUoutreach when posting online so we can help share your event.

100 Hours of Astronomy Box

The 100 Hours of Astronomy Box was compiled to help you plan and promote your events for the 100 hours, and beyond. This resource includes:

  • Ready-to-use designs for social media, available as a template on Canva and as AdobeIllustrator files.
  • Photo and video constent forms that can be easily adapted to your event.
  • Resources to suit any need: astronomy engagement tools, guides, and templates, including Canva designs, accessibility tips, educational materials, and links to key resources.
  • And more! This is an evolving resource. Check back here for new and exciting content!
100 Hours of Astronomy Box

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!

Help us spread the excitement of 100 Hours of Astronomy by sharing your event on social media! Use the official hashtags so your activity can reach a global audience.

Copy the hashtags and include them in your posts, photos, or livestreams: #100HoursOfAstronomy, #IAUoutreach

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.

Astronomy Engagement Events Calendar

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”.