2020 Nobel Prize in Physics awarded for research on Milky Way’s supermassive black hole

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.

Milky Way stars during public star party

Photo: Looking South Along the Lake at Letha House Park, Milky Way Glowing Overhead, the Moon Sinking Low in the West. Photo by Alan Studt.
Looking South Along the Lake at Letha House Park, Milky Way Glowing Overhead. Photo by Alan Studt. Nikon D810: ISO 3200, 13 sec., f/2.8, 14mm.

We had great sky conditions for our August 6 public star party at Letha House Park. We didn’t get an exact count, but I think there were between 75 and 100 guests who came for the program, including Park Ranger Bob who stopped by to say hello.

I had to make a quick count in the dark, but I think we had about 12 telescopes for this Medina County Park District program. Two telescopes were brought by new members who I believe joined one of our star parties for the first time.

Many thanks to Dave Nuti, Chris Christe, Bruce Lane, Jay Reynolds, Nora Mishey, Carl Kudrna, Rich & Nancy Whisler, Bob Wiersma, Alan Studt, Rob Seig, Bob & Mary Deep, and Gale Franko who joined me to help with the program!

Thanks to Jay, who manned the observatory and gave our new 12-inch go-to scope a workout to show the night sky to our numerous  guests.  And thanks also to Nora, who brought delicious homemade cookies and her astronomy Q & A display, and who served as a host in the building to help promote our club and the park district’s programs.

Reported by William Murmann, CAA President

Photo: Summer Milky Way. Photo by Alan Studt.
Summer Milky Way. Photo by Alan Studt. Nikon D810: ISO 5000, 15 sec., f/2.8, 14mm.

A most memorable vacation photo

Photo: The Milky Way by Alan Studt
Milky Way Rising – Photo by Alan Studt – Click to Enlarge

Cuyahoga Astronomical Association member Alan Studt captured this wonderful photo of our home galaxy, the Milky Way, under some fairly challenging circumstances the night of May 23. He and his wife, Gale, were on vacation in Massachusetts when a celestial photo op presented itself.

“That … night happened to be the only clear night in the forecast during our vacation so I had to check it out. We were staying about six miles east of Hyannis in West Dennis, just a five-minute drive from the south shoreline of Cape Cod.

“The beach parking lot gates get locked at midnight and the ‘Teapot’ in Sagittarius didn’t clear the horizon until 11:45, so I didn’t have a lot of time to shoot. I didn’t know where else to go to stay out later until the Milky Way was higher so I had to to accept what I could get.

“The weather conditions were not great. Temps in the mid-40s with at least a steady 25 MPH wind gusting to 35 MPH. Gale thinks it was faster since the car was shaking when she went back in to wait for me. My tripods blew over before I hung bags with bottles of water, extra lenses and shoes on them… the cameras were not attached at the time.”

So, even under pressure of time and weather, Studt came home with something truly out-of-this-world as a memorable vacation photo: a sea of stars!

Studt’s Photo Notes: Looking out over Nantucket Sound/Atlantic Ocean. Three horizontal shots layered together in Photoshop. 90-degree view – east to south. Taken at West Dennis Beach, Massachusetts on a very windy evening just before midnight. The lights in the distance on the right are from Nantucket Island, 30 miles south. On the left, down at the end of the beach is The Lighthouse Inn, an old lighthouse that is now a restaurant. There was a waxing First Quarter Moon about — maybe 30 degrees — above the horizon in the west. Nikon D600, 24mm, f3.5, ISO 6400, 20 seconds. Processed in Lightroom & Photoshop CC

Tracing the Milky Way’s magnetic field

Image: Polarized Emission from Milky Way Dust. Credit: ESA and the Planck Collaboration
Polarized Emission from Milky Way Dust

The interaction between interstellar dust in the Milky Way and the structure of our Galaxy’s magnetic field, as detected by the European Space Agency’s Planck satellite over the entire sky.

Planck scanned the sky to detect the most ancient light in the history of the Universe – the cosmic microwave background. It also detected significant foreground emission from diffuse material in our galaxy which, although a nuisance for cosmological studies, is extremely important for studying the birth of stars and other phenomena in the Milky Way.

Among the foreground sources at the wavelengths probed by Planck is cosmic dust, a minor but crucial component of the interstellar medium that pervades the galaxy. Mainly gas, it is the raw material for stars to form.

Interstellar clouds of gas and dust are also threaded by the galaxy’s magnetic field, and dust grains tend to align their longest axis at right angles to the direction of the field. As a result, the light emitted by dust grains is partly ‘polarized’ – it vibrates in a preferred direction – and, as such, could be caught by the polarization-sensitive detectors on Planck.

Scientists in the Planck collaboration are using the polarized emission of interstellar dust to reconstruct the galaxy’s magnetic field and study its role in the build-up of structure in the Milky Way, leading to star formation.

In this image, the color scale represents the total intensity of dust emission, revealing the structure of interstellar clouds in the Milky Way. The texture is based on measurements of the direction of the polarized light emitted by the dust, which in turn indicates the orientation of the magnetic field.

Credit: ESA and the Planck Collaboration