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
   

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2. What is a black hole?
   

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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
   

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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!
   

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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”)
   

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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
   

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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
   

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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
   

   View Slide

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
   

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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”)
    

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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
    

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12. Image: Event Horizon Telescope
    collaboration
    Taking a
    picture using
    radio light
    M87*
    

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13. Image: NRAO/AUI
    Taking a
    picture using
    radio light
    

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14. Image: ESO/O. Furtak
    Taking a
    picture using
    radio light
    

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15. Taking a
    picture using
    radio light
    Image: NRAO
    

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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
    

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17. Image: Event Horizon Telescope
    collaboration
    Taking a
    picture using
    radio light
    Lines show
    polarization
    of the light
    

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18. Image credit: NASA/CXC/M. Weiss
    Eating its
    star-friend
    (X-ray binaries)
    Star
    friend Black hole
    Accretion disk
    

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19. Image credit: NASA/CXC/M. Weiss
    Star
    friend Black hole
    Accretion disk
    20 million degrees F
    Eating its
    star-friend
    (X-ray binaries)
    

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20. Video credit: NASA
    Eating its
    star-friend
    (X-ray binaries)
    

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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
    

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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
    

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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
    

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24. Video: NASA/GSFC
    Image: Caltech
    X-ray
    telescopes
    

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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)
    

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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
    

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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
    

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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
    

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29. Image credit: NASA/CXC/M. Weiss
    Smashing
    together
    Image & video: Caltech/MIT/LIGO Lab
    https://www.ligo.caltech.edu/video/ligo20160211v2
    

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30. Image credit: NASA/CXC/M. Weiss
    Video: T. Ramirez/G.
    Lovelace/SXS
    Collaboration/LIGO-Virgo
    Collaboration
    Smashing
    together
    

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31. Bending
    light from
    behind
    them
    https://www.youtube.com/watch?v=y30bsSuTAIo
    Video: M31 by N. Priore
    

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32. Bending
    light from
    behind
    them
    Image: NASA
    

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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
    

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34. Bending
    light from
    behind
    them
    Image: NASA/ESA/HST
    

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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
    

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36. Q&A time!
    Image: NASA/JPL-Caltech
    alstev@msu.edu
    @abigailStev
    github.com/abigailStev
    Dr. Abbie Stevens
    

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37. Q&A time!
    Image: NASA/JPL-Caltech
    alstev@msu.edu
    @abigailStev
    github.com/abigailStev
    Dr. Abbie Stevens
    

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38. Image credit: NASA/CXC/K. Divona
    

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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
    

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