Image: NASA/JPL-Caltech How do we “see” black holes? Dr. Abbie Stevens Great Lakes Lectures

Black holes • A lot of stuff (mass) in a very small space • Very powerful gravity • Escape velocity faster than the speed of light! Image: J. Provost, ScienceNews.org imagine 3D space like a 2D fabric

Video: NASA/GSFC/J. Schnittman Black holes • Event horizon • Singularity • Photon sphere • Accretion disk Not pictured: relativistic jets The “danger zone” is very small!

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”)

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

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

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

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

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”)

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

Image: Event Horizon Telescope collaboration Taking a picture using radio light

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

Image: NRAO/AUI Taking a picture using radio light

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

Taking a picture using radio light Image: NRAO

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

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

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

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

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

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

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

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

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)

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

Image credit: NASA/CXC/M. Weiss Smashing together Video: S. Ossokine/A. Buonanno/T. Dietrich (MPI for Gravitational Physics)/R. Haas (NCSA)/SXS project

Image credit: NASA/CXC/M. Weiss Smashing together Video: T. Pyle, Caltech/MIT/LIGO Lab LIGO Virgo

Image credit: NASA/CXC/M. Weiss Smashing together Image & video: Caltech/MIT/LIGO Lab

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

Bending light from behind them

Bending light from behind them Image: NASA

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

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

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

Q&A time! Image: NASA/JPL-Caltech [email protected] @abigailStev github.com/abigailStev Dr. Abbie Stevens Great Lakes Lectures

Q&A time! Image: NASA/JPL-Caltech [email protected] @abigailStev github.com/abigailStev Dr. Abbie Stevens Great Lakes Lectures

Image credit: NASA/CXC/K. Divona

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: $1B for development and 5 years of operations § Combines strengths of NICER and LOFT: high throughput X-ray timing with good spectroscopy § If selected, launch in 2032 on a Space-X Falcon Heavy