Space photo of the day for June 17, 2025
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Big telescopes feature some of the finest and most precise mirrors in the world. So when one gets dirty, what happens?
The European Southern Observatory (ESO) operates some of the most powerful telescopes in the world. Established in 1962 by 16 countries across the globe, the ESO is a hub for astronomers looking to uncover the mysteries of our universe.
The observatory hosts four extremely powerful telescopes, which are used to survey the farthest corners of our galaxy, studying a variety of space structures and phenomena, from black holes to stars to asteroids.
While ESO's headquarters are in Garching, Germany, its four telescopes all sit in the Atacama Desert in Chile (hence the "Southern" part of ESO name). This photo was taken at the La Silla Observatory in Chile.
ESO hosts four different telescopes in Chile: the Very Large Telescope (VLT), the Atacama Large Millimeter/submillimeter Array (ALMA), the Extremely Large Telescope (ELT, which is currently being built), and La Silla, the subject of this photo.
While all four facilities focus on solving the mysteries of space, La Silla is centered specifically on finding exoplanets. Its two telescopes, the 11.5-foot (3.5 meters) New Technology Telescope (NTT) and the 11.8-foot (3.6 m) telescope both use ultraprecise mirrors to bounce images back from space for analysis.
In this photo, staff at La Silla work to clean the 11.8-foot telescope's primary mirror. As the mirror was made with fused silica, it takes a delicate process to restore it to a clean, ultraprecise state. Staff have to chemically strip the mirror's old aluminum coating before rinsing it with demineralized water.
The mirror then goes into a special vacuum chamber, where aluminum is deposited in a new layer thinner than the width of a human hair. If the aluminum layer were too thick or uneven, the mirror would lose its precision and with it, data from space.
You can read more about ESO's many telescopes and their work looking at exoplanets and other structures within our universe.
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A spinning universe could crack the mysteries of dark energy and our place in the multiverse
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Many researchers have tried to explain it by modifying equations of general relativity or suggesting the existence of new fields that could accelerate the universe's expansion," Poplawski told "It would be amazing if a simple rotation of the universe was the origin of dark energy, especially that it predicts its weakening." Evidence that the universe is rotating was recently delivered by the James Webb Space Telescope (JWST), which found that two-thirds of galaxies are rotating in the same direction. This suggests a lack of randomness and a preferred direction for cosmic rotation. Additionally, Poplawski pointed out that other astronomical data seem to show that the angle between the most likely axis of the spinning galaxies and the axis of the bulk flow of nearby galaxy clusters is 98 degrees, meaning they are nearly perpendicular in relation to each other. That is something that is in accordance with the hypothesis that the universe is rotating. 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"Therefore, the universe is not the only one; it is a part of a multiverse." For Poplawski, the simplest and most natural explanation of the origin of the rotation of the universe is black hole cosmology. Black hole cosmology suggests that every black hole creates a new baby universe on the other side of its event horizon, the one-way light-trapping surface that defines the outer boundary of a black hole. The theory replaces the central singularity at the heart of a black hole with "spacetime torsion" that gives rise to repulsive gravity that kick-starts the expansion of a new universe. "Because all black holes form from rotating objects, such as rotating stars or in the centers of rotating galaxies, they rotate too," Poplawski said. "The universe born in a rotating black hole inherits the axis of rotation of the black hole as its preferred axis." In other words, our universe may be spinning in a preferred direction because that is the way that the black hole it is sealed within is spinning. "A black hole becomes an Einstein-Rosen bridge or a 'wormhole' from the parent universe to the baby universe," Poplawski explained. "Observers in the new universe would see the other side of the parent black hole as a primordial white hole." In lieu of discovering a primordial white hole in our universe leading to our parent black hole and progenitor universe, the strongest evidence of this black hole cosmology is a preferred direction or "rotational asymmetry" in our universe. That can be seen in rotational asymmetry in the galaxies. "The motion of individual galaxies in that baby universe will be affected by the rotation of that universe," Poplawski said. 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