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I thought we already knew there was a supermassive black hole in the center of the Milky Way for a while now? What specifically did Genzel and Ghez do to expand

I thought we already knew there was a supermassive black hole in the center of the Milky Way for a while now? What specifically did Genzel and Ghez do to expand on that knowledge? I'm curious to know.

stargazer-3 6y ago
Back in the day they each led research to detect irrefutable evidence of it. This isn't anything new and groundbreaking.
- xioxox 6y ago
  I think that's rather unfair. The measurements are still ongoing with ever-increasing accuracy. In 2018 they managed to record the closest approach of the star S2, measuring a velocity of 7000 km/s at its maximum. This was after mapping the full 16 year orbit. I know that Genzel is still actively researching this topic with his group, see e.g. https://www.mpe.mpg.de/7433286/news20200416 https://www.mpe.mpg.de/7433286/news20200416
  - ISL 6y ago
    Ghez is very active. Both her group and Genzel's group are at the very leading edge. I haven't found an updated GIF, but even when I first saw images like this around 2002, it was clear she was chasing something awesome. https://www.physicscentral.com/explore/people/images/2008orbits_animfull.gif https://www.physicscentral.com/explore/people/images/2008orb...
  - stargazer-3 6y ago
    That is true, but the prize was awarded to Genzel for “for the __discovery__ of a supermassive compact object at the centre of our galaxy” (emphasis mine), not for the (impressive no doubt) follow-up work, so my comment was done in that context. That being said, I should have been a bit more enthusiastic about the infrared group's work to not appear dismissive on their ongoing contribution. Fun fact: looks like we're both in MPE (although I left two years ago).
xioxox 6y ago
Have a look at the linked documents giving the popular science background. They led the teams that gave the decisive proof that there is black hole at the galactic centre. The teams developed techniques to precisely measure the orbits of the stars which orbit the central black hole. Looking at the speed of the stars, particularly as they pass close to the object, you can measure its mass and put a constraint on its size. The only thing which is small enough and heavy enough is a black hole. Doing this required lots of advances in data analysis and adaptive optics to be able to measure the stars orbits to enough precision.
- fsnowdin 6y ago
  Now that's an answer. Thanks for the detailed reply!
nabla9 6y ago
We already know it because Genzel and Ghez discovered it. Their work goes back 30 years.
- fsnowdin 6y ago
  When I heard about this, I seriously thought we just only discovered Sagittarius A* this year and that I must have fucked up my memories. Thanks for the clarification!
  - cb321 6y ago
    The Penrose-Hawking singularity theorems go back 55 years to work starting in 1965. No joke. This has be to near a record in time lag between the work the Nobel committee recognized and when that work was first published. Better late than never I guess (but too late for Hawking, as has been mentioned elsewhere..) EDIT - a detailed analysis: https://physicstoday.scitation.org/do/10.1063/PT.5.2012/full/ https://physicstoday.scitation.org/do/10.1063/PT.5.2012/full...
    - fsnowdin 6y ago
      I've always thought Nobel prizes are awarded based on the winners' works in that particular year so this came as huge surprise. Too late for Hawking indeed, he could've very well been one of the winners today.
      - DiogenesKynikos 6y ago
        There's a huge backlog of people who deserve Nobel prizes. The committee is also conservative, and doesn't want to give out a prize for something that turns out to be wrong. Both factors mean that it takes years from discovery to the awarding of a Nobel prize.
        throwaway890369 6y ago
        It's one thing to allow enough time to pass before a given theory/experiment can be considered as "accepted" by science, and therefore eligible to the award. However, the Nobel committee's rules can be considered archaic to a fault: 3 winners at most, all winners must be living at the time of the award. If you want an egregious example of exclusion, look at the 2013 Nobel prize for the discovery of the Higgs boson. The prize was given to Higgs and Englert [0], but by any measure it should have been awarded to the five living scientists who made the discovery [1]. Was there really any reason to exclude Guralnik, Hagen and Kibble, who were all alive at the time of the award, other than a strict adherence to the "rule of three"? [0]: https://web.archive.org/web/20131008193310/http://www.nobelprize.org/nobel_prizes/physics/laureates/2013/press.pdf https://web.archive.org/web/20131008193310/http://www.nobelp... [1]: https://en.wikipedia.org/wiki/1964_PRL_symmetry_breaking_papers https://en.wikipedia.org/wiki/1964_PRL_symmetry_breaking_pap...
satori99 6y ago
Made this cool video? https://www.youtube.com/watch?v=u_gggKHvfGw https://www.youtube.com/watch?v=u_gggKHvfGw

stargazer-3 6y ago

Back in the day they each led research to detect irrefutable evidence of it. This isn't anything new and groundbreaking.

xioxox 6y ago
I think that's rather unfair. The measurements are still ongoing with ever-increasing accuracy. In 2018 they managed to record the closest approach of the star S2, measuring a velocity of 7000 km/s at its maximum. This was after mapping the full 16 year orbit. I know that Genzel is still actively researching this topic with his group, see e.g. https://www.mpe.mpg.de/7433286/news20200416 https://www.mpe.mpg.de/7433286/news20200416
- ISL 6y ago
  Ghez is very active. Both her group and Genzel's group are at the very leading edge. I haven't found an updated GIF, but even when I first saw images like this around 2002, it was clear she was chasing something awesome. https://www.physicscentral.com/explore/people/images/2008orbits_animfull.gif https://www.physicscentral.com/explore/people/images/2008orb...
- stargazer-3 6y ago
  That is true, but the prize was awarded to Genzel for “for the __discovery__ of a supermassive compact object at the centre of our galaxy” (emphasis mine), not for the (impressive no doubt) follow-up work, so my comment was done in that context. That being said, I should have been a bit more enthusiastic about the infrared group's work to not appear dismissive on their ongoing contribution. Fun fact: looks like we're both in MPE (although I left two years ago).

xioxox 6y ago

Have a look at the linked documents giving the popular science background. They led the teams that gave the decisive proof that there is black hole at the galactic centre. The teams developed techniques to precisely measure the orbits of the stars which orbit the central black hole. Looking at the speed of the stars, particularly as they pass close to the object, you can measure its mass and put a constraint on its size. The only thing which is small enough and heavy enough is a black hole. Doing this required lots of advances in data analysis and adaptive optics to be able to measure the stars orbits to enough precision.

fsnowdin 6y ago
Now that's an answer. Thanks for the detailed reply!

nabla9 6y ago

We already know it because Genzel and Ghez discovered it. Their work goes back 30 years.

fsnowdin 6y ago
When I heard about this, I seriously thought we just only discovered Sagittarius A* this year and that I must have fucked up my memories. Thanks for the clarification!
- cb321 6y ago
  The Penrose-Hawking singularity theorems go back 55 years to work starting in 1965. No joke. This has be to near a record in time lag between the work the Nobel committee recognized and when that work was first published. Better late than never I guess (but too late for Hawking, as has been mentioned elsewhere..) EDIT - a detailed analysis: https://physicstoday.scitation.org/do/10.1063/PT.5.2012/full/ https://physicstoday.scitation.org/do/10.1063/PT.5.2012/full...
  - fsnowdin 6y ago
    I've always thought Nobel prizes are awarded based on the winners' works in that particular year so this came as huge surprise. Too late for Hawking indeed, he could've very well been one of the winners today.
    - DiogenesKynikos 6y ago
      There's a huge backlog of people who deserve Nobel prizes. The committee is also conservative, and doesn't want to give out a prize for something that turns out to be wrong. Both factors mean that it takes years from discovery to the awarding of a Nobel prize.
      - throwaway890369 6y ago
        It's one thing to allow enough time to pass before a given theory/experiment can be considered as "accepted" by science, and therefore eligible to the award. However, the Nobel committee's rules can be considered archaic to a fault: 3 winners at most, all winners must be living at the time of the award. If you want an egregious example of exclusion, look at the 2013 Nobel prize for the discovery of the Higgs boson. The prize was given to Higgs and Englert [0], but by any measure it should have been awarded to the five living scientists who made the discovery [1]. Was there really any reason to exclude Guralnik, Hagen and Kibble, who were all alive at the time of the award, other than a strict adherence to the "rule of three"? [0]: https://web.archive.org/web/20131008193310/http://www.nobelprize.org/nobel_prizes/physics/laureates/2013/press.pdf https://web.archive.org/web/20131008193310/http://www.nobelp... [1]: https://en.wikipedia.org/wiki/1964_PRL_symmetry_breaking_papers https://en.wikipedia.org/wiki/1964_PRL_symmetry_breaking_pap...

satori99 6y ago

Made this cool video? https://www.youtube.com/watch?v=u_gggKHvfGw https://www.youtube.com/watch?v=u_gggKHvfGw