From July 3 to August 16, 2026, the Royal Palace is open to the public. This is an opportunity to explore the “Science and Culture” exhibition entitled Music, Sound & Imagination.

In the Grand Gallery, visitors can discover objects, works of art, sound clips and documents, all relating to sound and music. The Music, Sound & Imagination exhibition is organised by Belspo in collaboration with the Federal Scientific Institutes, of which the Royal Observatory of Belgium is a member, as well as the Royal Conservatoire of Brussels and the Queen Elisabeth Music Chapel.

Star Sounds and a Mini-Podcast

On this occasion, the Royal Observatory of Belgium has collaborated with the AstroSounds project to present “star sounds” to the public. AstroSounds is a citizen science project inviting members of the public to analyse the light spectra of stars that have been converted into sounds. Stars vibrate, and by studying their vibrations, we can glean information about the interiors of these celestial bodies. This science, known as asteroseismology, is one of the Observatory’s fields of expertise.

Just like the sounds of musical instruments, the “sounds” of stars are distinguished by their timbre, making it possible to recognise the type of star simply by listening to them. The exhibition and the Observatory’s website showcase the sounds of four types of stars: a sun-like star, an RR Lyrae star, a Beta Cephei star and a classical Cepheid.

Visitors will also have the opportunity to discover other sounds linked to the Observatory and its activities. The mini-podcast, which is also available online, invites listeners to experience a day in the heart of the Observatory’s laboratories and to discover the daily lives of its scientists.

Further information and tickets:

• Main exhibition website: https://royal.belspo.be
• Discover the sounds of four types of stars
• Podcast: “A Day at the Observatory”

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The principle measurement is based on the monitoring of the levitation of a superconducting niobium sphere of mass 4 grams. In 1995, currents were injected into superconducting coils causing the sphere to levitate; the currents have never been dissipated ever since. Although the fundamental importance of this measurement is not yet clear, as it does not contradict the physics of persistent currents, it is at least worthy of a place in the “cabinet of curiosities” of solid state physics.

An article discussing this double record will soon be published in EOS Transactions, the journal of the American Geophysical Union.

Measurements such as these are important in geophysics, as they’re rare over such long periods, and because they provide a record of the long-term variation in gravity due to slow tectonic movements and/or climatic variations. Such measurements are also important for the study of the water cycle that influences gravity.

The aforementioned gravimeter is still going strong and is not ready for retirement yet! Long-term monitoring of gravity has been shown to be of the highest scientific interest, and is measured in several laboratories. This gallant instrument is still participating in numerous projects, such as understanding long period gravity variations.

The superconducting gravimeter is located at the end of a 130 m – long gallery, 48 meters underneath the surface, in Membach (city of Baelen, eastern Belgium). The instrument sensor is immersed in liquid helium in which the temperature is held at -269°C, in other words 4 degrees above absolute zero. Photo credit: E. Coveliers & ORB-KSB. Copy authorized with mention of the source.

The Seismology-Gravimetry service of the Royal Observatory of Belgium thanks the Direction de l’Exploitation des Barrages – DGO2 and the Département de la Nature et des Forêts of the Walloon Region, the municipality of Membach-Baelen, Air Products and the National Lottery for their support.

Scientific contact:

Dr. Michel van Camp
Avenue Circulaire 3
BE-1180 Uccle
Tel : +32-(0)2 373 02 65
Mobile : 0473 518 241
mvc@oma.be
http://www.seismology.be

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