University:
Boston University
Course:
CAS AS 311 | Planetary Physics
Academic year:

2021
Views:

371

Pages:

14
Author:

preissatztcsz

Jets from Black Holes in Quasars BLACK HOLE Gravity so strong that nothing - not even light - can escape from inside the boundary event horizon → event horizon  How big is a BLACK HOLE? - Depends on its mass Human-mass black hole: much smaller than the nucleus of an atom Black hole with sun’s mass: 6 km (about the size of downtown) 1 billion times sun’s mass: about the size of the solar system Radius = 2GM/c2  ACCRETING BLACK HOLES ARE BRIGHT! Some of the particles can escape into winds or jets accretion disk  jet jet jet Most of the matter falls in but glows in UV & X-ray light before it crosses the event horizon How Nature Makes BLACK HOLES A star more than 10 or 20 times as massive as the sun uses up all of the nuclear fuel in its core → gravity contracts the star’s core Resistance is too weak to stop collapse → black hole forms  And then it just grows! How many BLACK HOLES are there in our Galaxy? Can estimate by number of very massive stars that have lived & died: → about 100 million! Nearly all of them are starving Don’t worry - there is a negligible chance that we’ll run into one for trillions of years Black-hole Binary Star Systems Most stars have companions (binary star) If more massive one becomes a black hole, it can suck gas from its companion → X-ray binary system About 20 such systems known in our Galaxy, another 20 suspected The Monster at the Center of Our Galaxy Massive stars orbit a point in space in Sagittarius at center of Milky Way → Black hole 4 million times mass of the sun Very little material is currently falling into the black hole Otherwise, it would be a very luminous source of X-rays Don’t Feed the Black Hole! Well-fed Monsters: Active Galaxies & Quasars • Ultraluminous nucleus of a galaxy • Supermassive black hole being fed constantly • Quasars are the most luminous variety The radio galaxy 3C 120 (distance = 500 million light-years) Hubble Space Telescope image (Harris & Cheung) Blazars Subclass (5-10%) of Quasars • • • • • Prominent jet of magnetized, ultra-hot gas (plasma) Flows out of nucleus at nearly the speed of light If jet points toward us, it beams radiation in our direction Jet is bright across entire electromagnetic spectrum Bright spots appear to move faster than light (illusion) Quasar 3C 273 Visible light HST X-ray Chandra Marshall et al. Radio VLBA The Boston University Blazar Research Group Some of the students can still escape but it’s too late for me & Svetlana accretion disk jet  jet Telescopes We Use - Visible Light + Much More Lowell Obs. Perkins Telescope (visible & infrared light) Calar Alto 2.2 m telescope (visible light) Liverpool Telescope (visible & infrared light) Very Long Baseline Array (VLBA) (radio images) Crimean Astrophysical Observatory 70 cm telescope St. Petersburg (Russia) State University 0.4 m telescope Rossi X-ray Timing Explorer, XMM-Newton, & Swift (X-rays) Chandra (X-rays), Hubble (visible light), Spitzer (infrared light) University of Michigan Radio Observatory IRAM 30 m (microwaves) Metsähovi Radio Observatory Fermi Gamma-ray Space Telescope VLBA Blazars X-ray Rapidly changing brightness Light from ultrahigh energy electrons Blazars Brightness changes over decades of time Visible light

Jets from Black Holes in Quasars Chapter 1