Andrea M. Ghez

Table of contents

Helpful webpages:

Link to inclusion in public webpage:

Speaker notes:

Introduction slide / General speaker notes

Researcher's background:

Andrea Ghez was born in New York City, her father of Jewish heritage and mother from an Irish Catholic family. Ghez was inspired to be the first female astronaut, and began college as a major in mathematics. She later transitioned to majoring in physics, and earned her bachelors degree from MIT in 1987, followed by a PhD from the California Institute of Technology in 1992 under the supervision of Gerry Neugebauer. Andrea is now a professor in the Department of Physics and Astronomy at the University of California.

Synopsis of Work:

Ghez was awarded the Nobel Prize in 2020, shared with Roger Penrose and Reinhard Genzel, for her discovery of a supermassive black hole governing the orbits of stars at the center of our Milky Way.

Ghez uses incredibly powerful imaging techniques to study the galactic center, most notably through the use of Adaptive Optics at the Keck telescopes in Hawaii. By studying the kinematics of stars close the the galactic center, Ghez and her team were able to deduce the existence of a supermassive black hole Saggitarius A* at a mass of approximately 4 million solar masses. Adaptive Optics are used to correct for atmospheric turbulence present with ground-based telescopes, which allows for observations at incredibly high spatial resolution. Previously, the star S2 had been imaged orbiting the galactic center with a period of about 16 years. Ghez and her team discovered the start S0-102 with the Keck telescopes orbiting at a period of 12.8 years, and used this star's orbit to accurately measure the mass of the central black hole.

Citations and resources:

https://en.wikipedia.org/wiki/S55_(star)

https://en.wikipedia.org/wiki/S2_(star)#S0–102

https://en.wikipedia.org/wiki/Andrea_M._Ghez

Societal relevance of work:

Ghez was the fourth woman to win the Nobel prize in physics, preceded by Marie Curie, Maria Goeppert Mayer and Donna Strickland.

The existence of black holes, and a supermassive black hole at the center of our galaxy, had long been theorized but lacked concrete experimental evidence. The concurrent work of Andrea Ghez and Reinhard Genzel finally settled this theory as true, and perfectly bolsters Albert Einstein's theory of General Relativity. Not only does this work settle theoretical debates, but it also has interesting consequences for galaxy evolution. Recent observations of nearby galaxies reveal that a central supermassive black hole is not a unique characteristic, and it has been proposed that all galaxies may host black holes in their core. The relationship between the growth and evolution of galaxies and their central supermassive black holes is an active question in astronomy today.

Slide 1: Kepler's Law

Researcher's background:

Andrea Ghez was born in New York City, her father of Jewish heritage and mother from an Irish Catholic family. Ghez was inspired to be the first female astronaut, and began college as a major in mathematics. She later transitioned to majoring in physics, and earned her bachelors degree from MIT in 1987, followed by a PhD from the California Institute of Technology in 1992 under the supervision of Gerry Neugebauer. Andrea is now a professor in the Department of Physics and Astronomy at the University of California.

Science details:

By observing the kinematics of stars at the galactic centre, namely the orbit of S0-021, Ghez and her team were able to accurately deduce the mass of the object at the centre using Kepler's third law of planetary motion. The mass measured was so great that it could only be explained by the presence of a supermassive black hole.

The two stars of closest orbit to Sgr A* are S0-2 and S0-102.

The orbit of S0-2 is approximately 16 years, while the orbit of S0-102 is approximately 12.8 years. The velocity of both stars at their periapsis (point of closest approach to the central black hole) are about 1.7% the speed of light.

The observations of these stars and the galactic center were made at the Keck Observatory in Hawaii, made possible by Adaptive Optics.

Citations and resources:

https://en.wikipedia.org/wiki/S55_(star)

https://en.wikipedia.org/wiki/Andrea_M._Ghez

https://en.wikipedia.org/wiki/S2_(star)

Figures:

Animation of the stellar orbits in the central 0.5 arcseconds of our galaxy. Data obtained from Keck Telescopes. The orbit of S0-2 is seen in yellow.

http://www.astro.ucla.edu/~ghezgroup/gc/animations.html

Societal relevance of work:

Ghez was the fourth woman to win the Nobel prize in physics, preceded by Marie Curie, Maria Goeppert Mayer and Donna Strickland.

The existence of black holes, and a supermassive black hole at the center of our galaxy, had long been theorized but lacked concrete experimental evidence. The concurrent work of Andrea Ghez and Reinhard Genzel finally settled this theory as true, and perfectly bolsters Albert Einstein's theory of General Relativity. Not only does this work settle theoretical debates, but it also has interesting consequences for galaxy evolution. Recent observations of nearby galaxies reveal that a central supermassive black hole is not a unique characteristic, and it has been proposed that all galaxies may host black holes in their core. The relationship between the growth and evolution of galaxies and their central supermassive black holes is an active question in astronomy today.

Slide 2: Kepler's law 2

Researcher's background:

Andrea Ghez was born in New York City, her father of Jewish heritage and mother from an Irish Catholic family. Ghez was inspired to be the first female astronaut, and began college as a major in mathematics. She later transitioned to majoring in physics, and earned her bachelors degree from MIT in 1987, followed by a PhD from the California Institute of Technology in 1992 under the supervision of Gerry Neugebauer. Andrea is now a professor in the Department of Physics and Astronomy at the University of California.

Science details:

By observing the kinematics of stars at the galactic centre, namely the orbit of S0-021, Ghez and her team were able to accurately deduce the mass of the object at the centre using Kepler's third law of planetary motion. The mass measured was so great that it could only be explained by the presence of a supermassive black hole.

The two stars of closest orbit to Sgr A* are S0-2 and S0-102.

The orbit of S0-2 is approximately 16 years, while the orbit of S0-102 is approximately 12.8 years. The velocity of both stars at their periapsis (point of closest approach to the central black hole) are about 1.7% the speed of light.

The observations of these stars and the galactic center were made at the Keck Observatory in Hawaii, made possible by Adaptive Optics.

Citations and resources:

https://en.wikipedia.org/wiki/S55_(star)

https://en.wikipedia.org/wiki/Andrea_M._Ghez

https://en.wikipedia.org/wiki/S2_(star)

Figures:

The orbits of the two stars SO-2 and SO-102 around the supermassive black hole located at the center of the Milky Way galaxy, as imaged in IR by the Keck Telescopes.

https://en.wikipedia.org/wiki/S2_(star)

Societal relevance of work:

Ghez was the fourth woman to win the Nobel prize in physics, preceded by Marie Curie, Maria Goeppert Mayer and Donna Strickland.

The existence of black holes, and a supermassive black hole at the center of our galaxy, had long been theorized but lacked concrete experimental evidence. The concurrent work of Andrea Ghez and Reinhard Genzel finally settled this theory as true, and perfectly bolsters Albert Einstein's theory of General Relativity. Not only does this work settle theoretical debates, but it also has interesting consequences for galaxy evolution. Recent observations of nearby galaxies reveal that a central supermassive black hole is not a unique characteristic, and it has been proposed that all galaxies may host black holes in their core. The relationship between the growth and evolution of galaxies and their central supermassive black holes is an active question in astronomy today.

Slide 3: two observations

Researcher's background:

Andrea Ghez was born in New York City, her father of Jewish heritage and mother from an Irish Catholic family. Ghez was inspired to be the first female astronaut, and began college as a major in mathematics. She later transitioned to majoring in physics, and earned her bachelors degree from MIT in 1987, followed by a PhD from the California Institute of Technology in 1992 under the supervision of Gerry Neugebauer. Andrea is now a professor in the Department of Physics and Astronomy at the University of California.

Science details:

By observing the kinematics of stars at the galactic centre, namely the orbit of S0-021, Ghez and her team were able to accurately deduce the mass of the object at the centre using Kepler's third law of planetary motion. The mass measured was so great that it could only be explained by the presence of a supermassive black hole.

The two stars of closest orbit to Sgr A* are S0-2 and S0-102.

The orbit of S0-2 is approximately 16 years, while the orbit of S0-102 is approximately 12.8 years. The velocity of both stars at their periapsis (point of closest approach to the central black hole) are about 1.7% the speed of light.

The observations of these stars and the galactic center were made concurrently by two research groups – one headed by Andrea Ghez at UCLA through the use of the Keck Telescopes, and the other headed by Reinhard Genzel at the Max Planck Institute for Extraterrestrial Physics using the European Souther Observatory's Very Large Telescope in Chile.

Citations and resources:

https://en.wikipedia.org/wiki/S55_(star)

https://en.wikipedia.org/wiki/Very_Large_Telescope

https://www.keckobservatory.org/

https://en.wikipedia.org/wiki/S2_(star)

Figures:

Left: Time-lapse of observations from the European Southern Observatory showing stars orbiting Sgr A*, from Reinhard Genzel's group.

https://www.nature.com/articles/d41586-018-05825-3

Right: Animation of the stellar orbits in the central 0.5 arcseconds of our galaxy. Data obtained from Keck Telescopes. The orbit of S0-2 is seen in yellow.

http://www.astro.ucla.edu/~ghezgroup/gc/animations.html

Societal relevance of work:

Ghez was the fourth woman to win the Nobel prize in physics, preceded by Marie Curie, Maria Goeppert Mayer and Donna Strickland.

The existence of black holes, and a supermassive black hole at the center of our galaxy, had long been theorized but lacked concrete experimental evidence. The concurrent work of Andrea Ghez and Reinhard Genzel finally settled this theory as true, and perfectly bolsters Albert Einstein's theory of General Relativity. Not only does this work settle theoretical debates, but it also has interesting consequences for galaxy evolution. Recent observations of nearby galaxies reveal that a central supermassive black hole is not a unique characteristic, and it has been proposed that all galaxies may host black holes in their core. The relationship between the growth and evolution of galaxies and their central supermassive black holes is an active question in astronomy today.

Slide 4: Adaptive Optics with diagram

Researcher's background:

Andrea Ghez was born in New York City, her father of Jewish heritage and mother from an Irish Catholic family. Ghez was inspired to be the first female astronaut, and began college as a major in mathematics. She later transitioned to majoring in physics, and earned her bachelors degree from MIT in 1987, followed by a PhD from the California Institute of Technology in 1992 under the supervision of Gerry Neugebauer. Andrea is now a professor in the Department of Physics and Astronomy at the University of California.

Science details:

In order to resolve the orbits of the stars in the galactic center, Ghez and her team had to correct for atmospheric disturbances with a technique called Adaptive Optics. Atmospheric disturbances are particularly difficult to correct for due to their fluctuating nature, and must be corrected for dynamically, hence 'Adaptive' Optics.

The technique works by creating an artificial 'guide star' in the sky, and sensing the disturbances from that star. The Keck telescopes create this star by shining a sodium laser into the upper part of the earth's mesosphere (rich in sodium atoms deposited by micrometeorites). The laser is tuned to cause spontaneous emission in these atoms, creating a star-like source in the sky close to the real source of interest. The atmospheric disturbances distorting the image of the guide star are then used to control a flexible mirror which is warped to compensate for the disturbances, thus producing a corrected image of the star of interest.

Citations and resources:

https://www2.keck.hawaii.edu/optics/lgsao/lgsbasics.html

https://en.wikipedia.org/wiki/Adaptive_optics

Figures:

Left: Keck I and Keck II telescopes in Hawaii, firing their dual sodium lasers into the atmosphere. https://www.ethantweedie.com/observatory-photography

Right: Diagram of an Adaptive Optics system. The blue light from the star is used for the wavefront sensor, and the deduced wavefront errors drive a wavefront corrector (here a flexible mirror) to remove the errors in the input wavefront, and therefore pass a corrected (and ideally diffraction limited) wavefront on to the science instrument. https://www.ast.cam.ac.uk/research/instrumentation.surveys.and.projects/lucky.imaging/lucky.adaptive.optics

Societal relevance of work:

Ghez was the fourth woman to win the Nobel prize in physics, preceded by Marie Curie, Maria Goeppert Mayer and Donna Strickland.

The existence of black holes, and a supermassive black hole at the center of our galaxy, had long been theorized but lacked concrete experimental evidence. The concurrent work of Andrea Ghez and Reinhard Genzel finally settled this theory as true, and perfectly bolsters Albert Einstein's theory of General Relativity. Not only does this work settle theoretical debates, but it also has interesting consequences for galaxy evolution. Recent observations of nearby galaxies reveal that a central supermassive black hole is not a unique characteristic, and it has been proposed that all galaxies may host black holes in their core. The relationship between the growth and evolution of galaxies and their central supermassive black holes is an active question in astronomy today.

Slide 5: Adaptive Optics with GIF

Researcher's background:

Andrea Ghez was born in New York City, her father of Jewish heritage and mother from an Irish Catholic family. Ghez was inspired to be the first female astronaut, and began college as a major in mathematics. She later transitioned to majoring in physics, and earned her bachelors degree from MIT in 1987, followed by a PhD from the California Institute of Technology in 1992 under the supervision of Gerry Neugebauer. Andrea is now a professor in the Department of Physics and Astronomy at the University of California.

Science details:

In order to resolve the orbits of the stars in the galactic center, Ghez and her team had to correct for atmospheric disturbances with a technique called Adaptive Optics. Atmospheric disturbances are particularly difficult to correct for due to their fluctuating nature, and must be corrected for dynamically, hence 'Adaptive' Optics.

The technique works by creating an artificial 'guide star' in the sky, and sensing the disturbances from that star. The Keck telescopes create this star by shining a sodium laser into the upper part of the earth's mesosphere (rich in sodium atoms deposited by micrometeorites). The laser is tuned to cause spontaneous emission in these atoms, creating a star-like source in the sky close to the real source of interest. The atmospheric disturbances distorting the image of the guide star are then used to control a flexible mirror which is warped to compensate for the disturbances, thus producing a corrected image of the star of interest.

Citations and resources:

https://www2.keck.hawaii.edu/optics/lgsao/lgsbasics.html

https://en.wikipedia.org/wiki/Adaptive_optics

Figures:

Left: Keck I and Keck II telescopes in Hawaii, firing their dual sodium lasers into the atmosphere. https://www.ethantweedie.com/observatory-photography

Right: Animation showing observations of the Galactic Center with and without Adaptive Optics, illustrating the resolution gain. http://www.astro.ucla.edu/~ghezgroup/gc/animations.html

Societal relevance of work:

Ghez was the fourth woman to win the Nobel prize in physics, preceded by Marie Curie, Maria Goeppert Mayer and Donna Strickland.

The existence of black holes, and a supermassive black hole at the center of our galaxy, had long been theorized but lacked concrete experimental evidence. The concurrent work of Andrea Ghez and Reinhard Genzel finally settled this theory as true, and perfectly bolsters Albert Einstein's theory of General Relativity. Not only does this work settle theoretical debates, but it also has interesting consequences for galaxy evolution. Recent observations of nearby galaxies reveal that a central supermassive black hole is not a unique characteristic, and it has been proposed that all galaxies may host black holes in their core. The relationship between the growth and evolution of galaxies and their central supermassive black holes is an active question in astronomy today.