RASC: How do we 'see' black holes?

Black holes formed from dying massive stars are the densest things in the universe. They have ten to 100 times the mass of the Sun crammed into a space that is only tens of miles across. Black holes get their name because their gravity is so strong that not even light can escape, so they look black to us. However, even though light can't escape from inside the event horizon, we still know where lots of them are. Scientists can find and study black holes from effects they have on the space environment around them. In this talk, I'll tell you about the ways we have of finding black holes and learning more about their extreme physics.

Speaker bio:
Dr. Abbie Stevens is an NSF Astronomy & Astrophysics Postdoctoral Fellow at Michigan State University and the University of Michigan. She studies black holes and neutron stars by looking at X-ray light coming from stars they're eating. Alongside this research, Abbie is involved in X-ray space telescopes, science advising on creative projects, open-source software development, astronomy data science, science literacy education, and mental health initiatives in academia. Prior to Michigan, Abbie did her PhD at the University of Amsterdam in the Netherlands, her MSc at the University of Alberta in Canada, and her BA at Bard College in upstate NY. In her spare time, she enjoys knitting, gardening, traveling, reading, and drinking tea.

More about Dr. Abbie Stevens: https://abigailstevens.com/

Transcript

1. Image: NASA/JPL-Caltech How do we “see” black holes? Dr. Abbie Stevens Michigan State Univ. RASC-Calgary Centre
2. What is a black hole?
3. Black holes • A lot of stuff (mass) in a very small space • Very powerful gravity • Escape velocity faster than the speed of light, so not even light can escape from it! Image: J. Provost, ScienceNews.org imagine 3D space like a 2D fabric
4. Video: NASA/GSFC/J. Schnittman Black holes • Event horizon: crossing the point of no return • Singularity: at the “centre” Also: accretion disk, photon sphere Not pictured: relativistic jets The “danger zone” is very small!
5. Black holes Image: Event Horizon Telescope collaboration No limit on how big they can get! Small black holes are formed from the death and collapse of a big star (“stellar” or “stellar mass”) Big black holes have been around since very early in the universe, at the centers of galaxies (“supermassive”)
6. Black holes Image: Event Horizon Telescope collaboration No limit on how big they can get! Small black holes are formed from the death and collapse of a big star (“stellar” or “stellar mass”) Big black holes have been around since very early in the universe, at the centers of galaxies (“supermassive”) Quick interlude: Universe is really big, numbers get really big
7. Black holes Image: Event Horizon Telescope collaboration No limit on how big they can get! Small black holes are formed from the death and collapse of a big star (“stellar” or “stellar mass”) Big black holes have been around since very early in the universe, at the centers of galaxies (“supermassive”) Quick interlude: Universe is really big, numbers get really big 1 thousand seconds ≅ 16 minutes
8. Black holes Image: Event Horizon Telescope collaboration No limit on how big they can get! Small black holes are formed from the death and collapse of a big star (“stellar” or “stellar mass”) Big black holes have been around since very early in the universe, at the centers of galaxies (“supermassive”) Quick interlude: Universe is really big, numbers get really big 1 thousand seconds ≅ 16 minutes 1 million seconds ≅ 11 days
9. Black holes Image: Event Horizon Telescope collaboration No limit on how big they can get! Small black holes are formed from the death and collapse of a big star (“stellar” or “stellar mass”) Big black holes have been around since very early in the universe, at the centers of galaxies (“supermassive”) Quick interlude: Universe is really big, numbers get really big 1 thousand seconds ≅ 16 minutes 1 million seconds ≅ 11 days 1 billion seconds ≅ 32 years
10. Black holes Image: Event Horizon Telescope collaboration Biggest black hole ever seen: 60 Billion times the mass of our Sun Smallest black hole ever seen: 3 times the mass of our Sun No limit on how big they can get! Small black holes are formed from the death and collapse of a big star (“stellar” or “stellar mass”) Big black holes have been around since very early in the universe, at the centers of galaxies (“supermassive”)
11. Can’t just grab one, put it on a table, shine a light on it, and study it Video: NASA/GSFC/J. Schnittman How do we study them? To see it, need to wait for one to send light in our direction We “see” black holes by looking at effects on their space environment
12. Image: Event Horizon Telescope collaboration Taking a picture using radio light M87*
13. Image: NRAO/AUI Taking a picture using radio light
14. Image: ESO/O. Furtak Taking a picture using radio light
15. Taking a picture using radio light Image: NRAO
16. Image: Event Horizon Telescope collaboration Taking a picture using radio light Computer simulation showing what it might look like if we had higher- resolution images
17. Image: Event Horizon Telescope collaboration Taking a picture using radio light Lines show polarization of the light
18. Image credit: NASA/CXC/M. Weiss Eating its star-friend (X-ray binaries) Star friend Black hole Accretion disk
19. Image credit: NASA/CXC/M. Weiss Star friend Black hole Accretion disk 20 million degrees F Eating its star-friend (X-ray binaries)
20. Video credit: NASA Eating its star-friend (X-ray binaries)
21. The first black hole we saw is called Cygnus X-1, in 1972. Eating its star-friend (X-ray binaries) Image credit: NASA/CXC/M. Weiss
22. Type of light Gets through Earth’s atmosphere? Approx. scale of wavelength? The electro-magnetic spectrum The colors that we see are a very small part of all the types of light that exist. Images: Shutterstock, NASA X-ray telescopes
23. The electro-magnetic spectrum Type of light Gets through Earth’s atmosphere? Approx. scale of wavelength Images: Shutterstock, NASA X-rays from space can’t get through Earth’s atmosphere, so we put X-ray telescopes on satellites and launch them into space on rockets! X-ray telescopes
24. Video: NASA/GSFC Image: Caltech X-ray telescopes
25. Eating other gas (AGN & quasars) Image credit: NASA/CXC/M. Weiss Chandra Deep Field Low X-ray Mid X-ray High X-ray Video: NASA/CXC/SAO/K. Arcand, SYSTEM Sounds (M. Russo, A. Santaguida)
26. Black hole as ☆ Nearby orbiting stars Sagittarius A-star (Sgr A*) at the center of our Milky Way galaxy! 4.3 million times the mass of the Sun https://www.youtube.com/watch?v=A2jcVusR54E
27. Image credit: NASA/CXC/M. Weiss Smashing together Video: S. Ossokine/A. Buonanno/T. Dietrich (MPI for Gravitational Physics)/R. Haas (NCSA)/SXS project
28. Image credit: NASA/CXC/M. Weiss Smashing together Video: T. Pyle, Caltech/MIT/LIGO Lab LIGO Virgo https://www.ligo.caltech.edu/video/ligo20160211v6
29. Image credit: NASA/CXC/M. Weiss Smashing together Image & video: Caltech/MIT/LIGO Lab https://www.ligo.caltech.edu/video/ligo20160211v2
30. Image credit: NASA/CXC/M. Weiss Video: T. Ramirez/G. Lovelace/SXS Collaboration/LIGO-Virgo Collaboration Smashing together
31. Bending light from behind them https://www.youtube.com/watch?v=y30bsSuTAIo Video: M31 by N. Priore
32. Bending light from behind them Image: NASA
33. Image: NASA/ESA/HST Bending light from behind them The strong gravity of the black hole acts like a lens, bending and distorting the image. Image: J. Rhoads(ASU)/WIYN/ AURA/NOAO/NSF
34. Bending light from behind them Image: NASA/ESA/HST
35. Image: NASA/JPL-Caltech How do we “see” black holes? Taking a picture using radio light Eating its star-friend Nearby orbiting stars Bending light from behind them Smashing together Eating other gas
36. Q&A time! Image: NASA/JPL-Caltech alstev@msu.edu @abigailStev github.com/abigailStev Dr. Abbie Stevens
37. Q&A time! Image: NASA/JPL-Caltech alstev@msu.edu @abigailStev github.com/abigailStev Dr. Abbie Stevens
38. Image credit: NASA/CXC/K. Divona
39. RXTE Science drivers: spin distribution of black holes, accretion disk winds, disk-jet connection, neutron star equation of state, burst oscillations, gamma-ray bursts, LIGO counterparts, tidal disruption events, discovering new sources, etc! Video from NASA Mission Design Lab, April 2018 § Proposed Probe-class space telescope, “medium” budget: $1.5B for development and 5 years of operations § High-throughput X-ray timing with good spectroscopy § If selected, launch in early-to-mid 2030s on a Space-X Falcon Heavy