An underground telescope wants to revolutionize astronomy with 10 kilometer arms: this will be the Einstein

In September 2017, the ruling of the Swedish Academy of Sciences regarding the Nobel Prize in Physics was announced. of that year. It went to three physicists assigned to the LIGO/VIRGO Collaboration, the experiment responsible for detecting gravitational waves that impact our planet.

New telescope. Now the experiment that could take over from LIGO/VIRGO is beginning to come into view. This is the Einstein telescopea new instrument that, from beneath the Earth’s surface, will continue the search for these waves.

Behind this project there are various institutions coordinated through the German Einstein Telescope community. For now, we know little about the project, but the first plans speak of a budget of 1.8 billion euros and an operating cost of 40 million annually. Construction of the instrument is also expected to begin in 2026 and be operational by 2035.

The telescope would be similar to LIGO/VIRGO, a triangle along whose vertices laser beams would be emitted. The location of the new instrument could be on the triple border between Germany, Belgium and the Netherlands. Its location is expected to be announced later in the year.

A different “spectrum”. Conventional telescopes, from optical to radio telescopes, including those like the James Webb that operate in other certain ranges, capture waves in different features of the electromagnetic spectrum, visible light, infrared, radio waves… However, they are not the only waves. that spread throughout the universe.

Albert Einstein predicted when developing his general theory of relativity that another type of wave would exist, gravitational waves. It was not until a century later, in 2015, that they were detected for the first time. A detection that was worth a Nobel Prize.

Third generation. Now the instruments capable of detecting this type of waves are moving towards their third generation. The technology used is laser interferometers. In these devices, a laser beam is divided and sent through two “arms”. At the ends of these, two mirrors where the beam bounces. Gravitational waves deform the path of the beam, causing it to arrive back sooner or later depending on the path of the wave.

“We want to use it to examine an area that is a thousand times larger than what is possible today (…). “And we should then find considerably more sources for which current instruments are not sensitive enough,” stated in a press release Achim Stahl, member of the German Einstein Telescope community.

250 meters below the ground. The Einstein telescope is designed to contain three nested detectors, explain those responsible. Each of these detectors will have two interferometers with “arms” 10 kilometers long. The telescope will be built about 250 meters deep to isolate it from possible interference.

The telescope will be 10 times more powerful than the current ones (the latest iterations Advanced Virgo and Advancer Ligo). A sensitivity great enough to distinguish changes in distance thousands of times smaller than the diameter of a proton, explains Stahl.

Gravitational waves and neutron stars. In 2017, a few weeks before the Nobel announcement, the LIGO/VIRGO Collaboration gave new news. It was the detection of a collision between two neutron stars. If the detection of gravitational waves in 2015 had lasted a few hundredths of a second while this new signal lasted about 100 seconds.

During this time, various telescopes were able to point in the direction from which the wave came to check what was happening from another perspective. The collision could thus be observed in two different types of waves, in the electromagnetic spectrum and as a gravitational wave.

Astronomy multi-messenger. Einstein promoters want to make this the norm. If we manage to have several instruments like Einstein in the future, it should be easy to triangulate the origin of these waves in order to tell other telescopes where to look and thus be able to systematize this new form of astronomy.

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Image | NIKHEF