Ob i Bl k H lObserving Black Holes

Nathan SandersDepartment of AstronomyDepartment of Astronomy

BLACK HOLESBLACK HOLES ARE REALARE REAL

Observing Black Holes: Outline

• But they're black! (how can we see them?)y ( )

Supermassive Stellar masspMass: millions (or billions!)

of sunsRadius: 5x solar radius (or

Mass: ~10 sunsRadius: ~30 km (Boston to

Concord)Radius: 5x solar radius (or out to Uranus' orbit!)

Concord)

What's the problem?

The way astronomy usually worksThe way astronomy usually worksNGC 6397, NASA and The Hubble Heritage Team, A. Cool (SFSU)

What's the problem?

Black holes are dark (don't emit light)

What's the problem?

Can we just look for their shadow?

What's the problem?

The Sun Solar mass black hole(scaled up 1000x)

p

(scaled up 1000x)

Not easily... black holes are tiny

What's the problem?

...even smaller than this

The electromagnetic spectrum

http://en.wikipedia.org/wiki/File:EM_Spectrum_Properties_edit.svg

A few common ways to produce light:• Blackbody: Heat1,2

• Synchrotron: Speeding electrons in magnetic fields3,4• Synchrotron: Speeding electrons in magnetic fields ,

1http://en.wikipedia.org/wiki/File:Embers_01.JPG 2NASA/STEREO3http://en.wikipedia.org/wiki/File:Schéma_de_principe_du_synchrotron.jpg 4Astronomy Online

Black holes don't suck!Black holes don t suck!Material can orbit black holes just like

planets orbit the sunplanets orbit the sun

http://en.wikipedia.org/wiki/File:Oort_cloud_Sedna_orbit.svg

The key to seeing black holes Th i h h i !They interact through gravity!

Artist's rendition of an accreting black hole and jetArtist s rendition of an accreting black hole and jetNASA/Alfred Kamajian

http://imagine.gsfc.nasa.gov/YBA/cyg-X1-mass/black-holes.html

Supermassive black holesfPower sources for active galactic nuclei

Illustration: NASA/CXC/M.Weiss

Active Galactic Nuclei:Black holes that scream at us

...from nearby

Cygnus A in radio emission(image by Alan Bridle, NRAO, with permission)

Active Galactic Nuclei:Black holes that scream at us

...from nearbyOur galaxy,for scale

Cygnus A in radio emission(image by Alan Bridle, NRAO, with permission)

Active Galactic Nuclei:Black holes that scream at us

...and far away

1 lightyear~587,850,000,000

An AGN 11 billion light years

, , ,miles

g yaway

(image from NASA's Compton Gamma Ray Observatory)

Sgr A*: Supermassive black hole at the center of the Milky Way

http://en.wikipedia.org/wiki/File:Milky_Way_Arch.jpg

~15 years

~size of solar

tsystem

Stars orbiting the galactic center"This animation was created by Prof. Andrea Ghez and her research team at UCLA and are from data sets obtained with the W. M. Keck Telescopes." Reproduced with

permission.

Stellar-mass black holesR f i di id l i• Remnants of individual massive stars

• X-rays emitted by superheated accreting material50 million°F!

Cygnus X-1, artist's renditionESA, Hubble

A nearby ~9x solar-mass black holeCygnus X-1

• Just one of >100 million in our galaxy1g y

• First identified as a black hole in 19722

Cygnus X-1, Chandra X-ray space telescope

NASA/CXC1Timmes et al. 1996, ApJ 457:834 2Bolton 1972, Nature 235, 5336:271

X-ray binaries in the globular clusters of NGC 13991

1Angelini et al. 2001, ApJ 557, 1:35 (with permission) 2Miller & Colbert 2004, IJMPD 13, 1:1

Gravitational microlensingU i ll bl k h l lik if i lUsing stellar mass black holes like a magnifying glass

http://en.wikipedia.org/wiki/File:Black_hole_lensing_web.gif

Black hole lensing a galaxy, simulation

6 microlensing black holes found?a dim object

closerlookjwithHubble

a fewmonthsmonthslater,it's bright!

Lensing from a 6 solar mass black holeBennett et al. 2002, ApJ 579, 2:639

The future of lensing detection:gFast surveys

Large Synoptic Survey Telescope (LSST)

in construction

Panoramic Survey Telescope & Rapid Response System (Pan-STARRS)

Operating now!

Image credit: Pan Starrs 1 Science Consortium Image credit: LSST CorporationImage credit: Pan Starrs 1 Science Consortium (including Harvard!)

Observing Black Holes: Summary

• They're black...• But we see the matter around

them!

• Supermassive black holesS f th b i ht t bj t i• Some of the brightest objects in the universe

• Stellar mass black holes• In our galaxy and beyond!• In our galaxy and beyond!

www.astrobites.com

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