All About Planetariums: What Is a Planetarium, And Why Are Planetariums Important Today?

~6 min

Planetariums have been known since antiquity and, of course, have changed a lot: you can now put a planetarium show at home or even have a pocket planetarium, like the Sky Tonight and Star Walk 2 apps. Nowadays, the world celebrates the International Day of Planetariums annually. In 2024, it is celebrated on May 7. In today's article, let’s learn why planetariums are important, talk about their history, and reveal how you can make your own planetarium at home.


International Day of Planetariums

The International Day of Planetariums (formerly known as the International Day of Planetaria) is a holiday that is held annually on the second Sunday in March. It celebrates the importance of planetariums as an educational tool that allows us to appreciate the grandeur and beauty of the Universe. The event's main goals are to inform the public about the significant role that planetariums play in culture, science, and education, and to make people understand that astronomy is an enjoyable and enthralling activity. Another important goal of the International Day of Planetariums is to encourage international collaborations between planetariums of different countries.

The Italian Association of Planetaria was the first to organize the Day of Planetariums in 1991 in Italy. The International Planetarium Society (IPS) supported this initiative, and in 1995, the Day of Planetariums was held worldwide for the first time.

When is the International Day of Planetariums?

Traditionally, the International Day of Planetariums has been celebrated on the second Sunday of March. However, the International Planetarium Society decided to shift the day to May 7 starting from 2024. The date is tied to an important event in planetarium history: on May 7, 1925, the first projection planetarium, also known as the Zeiss planetarium, opened at the Deutsche Museum in Munich, Germany. The year 2025 will mark the centennial of this event.

What is a planetarium?

A planetarium is a theater built for presenting educational and entertaining shows about the night sky in particular and astronomy in general. As a rule, in planetariums, scenes of sky objects are projected onto a large dome-shaped screen. These shows are usually accompanied by lectures or music. The term "planetarium" can also be used to describe other devices that illustrate the Solar System or the Universe, such as an orrery or computer simulation.

What’s inside a planetarium?

  • The main feature of a planetarium is a large dome-shaped screen that covers the entire ceiling. This dome acts as a canvas for stunning visuals of the night sky.
  • The projector system projects images onto the dome, recreating the detailed image of the night sky.
  • An audio system complements the visuals, providing a rich soundscape.
  • Comfortable seating arrangements ensure an unobstructed view of the dome from any angle, allowing everyone to have an optimal viewing experience.
  • Many planetariums also have telescopes which you can use to see stars and planets.

What do you do at a planetarium?

At a planetarium, you can experience a variety of activities and shows. Many planetariums offer immersive full-dome movies that take you on virtual journeys through space, exploring distant galaxies and cosmic phenomena. You can attend workshops and lectures, which may include stargazing sessions, telescope handling, or even astrophotography lessons. Some planetariums even offer interactive exhibits where you can learn about astronomy and participate in hands-on activities. Whether you're stargazing, learning about the Universe, or simply enjoying the beauty of the night sky, a visit to a planetarium is a fascinating and educational experience for all ages.

History of planetariums: from antiquity to the modern times

Let's turn to history to learn more about the predecessors of modern planetariums and their evolution from primitive devices to the wonders of science and technology.

What was the first planetarium?

The history of planetariums goes back into antiquity. The earliest known depiction of the sky was found in the tomb of Senenmut, an ancient Egyptian architect. Archimedes, a Greek polymath, was the first to create a primitive planetarium device: around 250 BCE, he made a cast-metal globe demonstrating the planets’ motions. Around 150 CE, the mathematician and astronomer Ptolemy recorded his designs for a Celestial Globe. Although this globe has never been found, notes on its construction survived up to today.

In the Middle Ages, astronomical clocks displaying the positions of the Sun, Moon, zodiacal constellations, and major planets were used in some cathedrals. In 1584, the Danish astronomer Tycho Brahe constructed the Celestial Globe. This model of a celestial sphere had a diameter of 1,5 meters and showed stars visible with the unaided eye. Several decades later, in 1654, the Globe of Gottorf was constructed in Germany. Inside of this Globe, measuring about four meters in diameter, was a circular bench for several persons. The star map with astrological and mythological symbols was depicted on the inside surface of the Globe of Gottorf.

One of the predecessors of modern planetariums is the orrery, a mechanical model of the Solar System used to recreate the motions of the planets and their natural satellites around the Sun. The first orrery was made in 1704 by clockmakers George Graham and Thomas Tompion; the instrument was named after Charles Boyle, 4th Earl of Orrery, an English nobleman and patron of the sciences. Eise Eisinga’s planetarium, the oldest working planetarium (which, in fact, is an orrery), was built between 1774 and 1781 in the Netherlands.

Who invented the planetarium projector?

Another way to show the planetary motions didn’t come up until the 1920s when the first planetarium projector was invented by Carl Zeiss Сompany. In 1919, Walther Bauersfeld, chief design engineer of the Carl Zeiss Company, conceived the idea of projection of the sky objects in a dark room. It took Bauersfeld and a large staff of scientists and engineers several years of calculations and research to implement the idea. As a result, the first modern planetarium projector was constructed and made it possible to demonstrate the wide variety of celestial bodies of our beautiful Universe.

What is a modern planetarium?

In the 1980s, the first digital projectors displaying computer graphics emerged and opened up modern astrophysics to the public. Today, thanks to computer graphics and the data on the Universe obtained not only through telescopes but also from space probes, we can lift off the Earth and travel across space, visiting other planets and distant stars. Moreover, there are plenty of portable planetariums widely used in schools, universities, and exhibitions and planetarium apps that help astronomy lovers explore the Universe at any time and any place.

How to make a planetarium?

If there is no planetarium near you or you just want to get creative, it’s quite possible to make your own planetarium projector. It’s essentially a night light projecting stars on your walls and ceiling. To create it, follow the steps below.

  • Take a soda can or a square cardboard box that will be used as a container and find a light source that fits the container you've chosen and connects to a power source from outside.
  • Find constellation patterns on the internet and print one of them on a sheet of paper. Note that the constellation pattern should fit around your can or box.
  • Temporarily tape the constellation pattern to your can or box and use a pin to make holes in it. Make larger holes for big stars on your template and smaller ones for small stars.
  • Take the constellation template off. Now you will see a pattern of points through which the light will be projected.
  • Make a hole for your light source on the bottom part of your container and put the light source inside.
  • Glue the bottom in place and tape any areas through which light may escape.

So, there it is! Place your compact planetarium in a dark room, turn on the light source inside, and enjoy stargazing! If you want to get a better understanding of the process described above, watch this video tutorial on how to make a planetarium at home.

There is even an easier way to create a starry sky inside your house. Use the stargazing apps Star Walk 2 and Sky Tonight as your portable planetarium! Turn the AR mode on and you’ll see the starscape overlaid on walls and furniture in your room. Enjoy stars, planets, constellations, satellites, and other space objects in the sky above you with your virtual planetarium!

What is a planetarium: key points to remember

A planetarium is a special place where you can learn many things about astronomy and the night sky. As a rule, it has a large dome-shaped screen on which the sky images are projected. Planetariums offer a wide variety of activities, including astronomy-themed workshops, lectures, and exhibits. If you're interested in stargazing, you'll surely be interested in visiting a planetarium, and will also enjoy using Star Walk 2 and Sky Tonight – mobile planetariums on your device.

Happy stargazing!