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The central parts of our Galaxy, the Milky Way, as observed in the near-infrared with the NACO instrument on ESO’s Very Large Telescope. By following the motions of the most central stars over more than 16 years, astronomers were able to determine the mass of the supermassive black hole that lurks there. Credit: ESO/S. Gillessen et al.

Reinhard Genzel and Andrea Ghez have jointly been awarded the 2020 Nobel Prize in Physics for their work on the supermassive black hole, Sagittarius A*, at the center of our galaxy. Genzel, Director at the Max Planck Institute for Extraterrestrial Physics in Germany, and his team have conducted observations of Sagittarius A* for nearly 30 years using a fleet of instruments on European Southern Observatory (ESO) telescopes.

Genzel shares half of the prize with Ghez, a professor at the University of California, Los Angeles in the US, “for the discovery of a supermassive compact object at the center of our galaxy”, with the other half awarded to Roger Penrose, professor at the University of Oxford in the UK, “for the discovery that black hole formation is a robust prediction of the general theory of relativity.” 

“Congratulations to all three Nobel laureates! We are delighted that the research on the supermassive black hole at the center of our galaxy has been recognized with the 2020 Nobel Prize in Physics. We are proud that the telescopes ESO builds and operates at its observatories in Chile played a key role in this discovery,” says ESO’s Director General Xavier Barcons. “The work done by Reinhard Genzel with ESO telescopes and by Andrea Ghez with the Keck telescopes in Hawaii has enabled unprecedented insight into Sagittarius A*, which confirmed predictions of Einstein’s general relativity.”

ESO has worked in very close collaboration with Genzel and his group for around 30 years. Since the early 1990s, Genzel and his team, in cooperation with ESO, have developed instruments designed to track the orbits of stars in the Sagittarius A* region at the center of the Milky Way. 

They started their campaign in 1992 using the SHARP instrument on ESO’s New Technology Telescope (NTT) at the La Silla Observatory in Chile. The team later used extremely sensitive instruments on ESO’s Very Large Telescope (VLT) and the Very Large Telescope Interferometer at the Paranal Observatory, namely NACO, SINFONI and later GRAVITY, to continue their study of Sagittarius A. 

In 2008, after 16 years of tracking stars orbiting Sagittarius A*, the team delivered the best empirical evidence that a supermassive black hole exists at the center of our galaxy. Both Genzel’s and Ghez’s groups accurately traced the orbit of one star in particular, S2, which reached the closest distance to Sagittarius A* in May 2018. ESO undertook a number of developments and infrastructure upgrades in Paranal to enable accurate measurements of the position and velocity of S2.

The team led by Genzel found the light emitted by the star close to the supermassive black hole was stretched to longer wavelengths, an effect known as gravitational redshift, confirming for the first time Einstein’s general relativity near a supermassive black hole. Earlier this year, the team announced they had seen S2 ‘dance’ around the supermassive black hole, showing its orbit is shaped like a rosette, an effect called Schwarzschild precession that was predicted by Einstein.

Genzel and his team are also involved in the development of instruments that will be installed on ESO’s Extremely Large Telescope, currently under construction in Chile’s Atacama Desert, which will enable them to probe the environment even closer to the supermassive black hole.

View the partial eclipse through telescopes imaging the Sun three different ways! Eclipse glasses free (while supplies last, may limit to one per group). Come on out and enjoy the view from Hiram, Ohio!

Due to scheduling difficulties, there will be no November Open Night at the observatory. We regret we are unable to offer a program this month but hope to offer public observing in December. Thank you for your interest!

Tonight’s planned Public Night is CANCELED due to inclement weather conditions and overcast skies expected to continue into late-night.

Photo: Earth's Moon - Mare Serenitatis & Mare Iridium. Photo by James Guilford.

The Moon: Mare Serenitatis (left, Sea of Serenity), half-lit Mare Iridium (right, Sea of Rainbows)

I can’t say as I blame them, the people who didn’t show for our observatory open night Saturday, March 28 — only seven braved the cold. After all, the temperature was about 19° (F), darned cold! But the sky was clear and the waxing Moon was high in the sky. Both Moon and Jupiter were sharing constellation Cancer with The Beehive star cluster (M44). Still, those sensible people who stayed home and warm missed a glorious view of old Luna. In my idle time waiting for visitors, I tried out a little afocal astrophotography using the observatory’s 9-inch Warner and Swasey telescope (ca. 1901) and my little Samsung Galaxy Camera 2 all-in-one. Most shots were a little shy of sharp, and all had some degree of chromatic aberration, and all had a big chunk of image missing where our century-old star diagonal is missing a bit of glass. One shot, however, did work out well, especially after a little fix-up including conversion to monochrome to eliminate color fringing. Not long after the last of our brave visitors left, I caught sight of the indistinct reappearance of Jupiter’s Great Red Spot and that was it… time to close up and go home. My toes needed to be thawed.