AST 105 1st Edition Lecture 21Topic: QuasarsI. Background Knowledge a. Baade and Murkowski in 1951b. From Hubble’s lawc. VelocitiesII. Luminosities ofIII. Sizes of IV. Super-Massive Black Holes (SBH)a. Other objectsV. Gamma-Ray Bursts Quasars- In 1951, Baade and Murkowski took photographs of object This object was called Cyngas A- Had a very strong radio source- Hubble’s law d=Vrecess../ Ho Spectra indicates a red shift doppler recessional velocity of 14,000 km per second ( recessional velocity) H0 = Hubble’s constant (72 km/second 1/MPC) D= 194 Mega-parsecs (=about 634 million LY’s)- 634 million LY’s away from us - Very strong source of radio waves- Large luminosities in radio frequencies - “Star like appearance and very strong radio signals”- Technically, Quasars must have a minimum red shift that corresponds to a velocity of 6% the speed of light up to 90% the speed of light At 90% speed of light, distance of 12 billion LY’s away Luminosity - Typical luminosity of a Quasar is 100x greater than the luminosity of the entire Milky Way Galaxy - Lsun = 1026 watts- LMilky Way= 1037 watts - Lquasar= 1039 watts These notes represent a detailed interpretation of the professor’s lecture. GradeBuddy is best used as a supplement to your own notes, not as a substitute.Sizes - In Quasars, we’ve noticed that luminosity fluctuates- Relativity puts a limit on the size of a fluctuating luminous body: “An object cannot vary in brightness faster than the time for light to travel across the object.” - We see fluctuations in as little as 3 hours - 3 light hours across is 3 trillion meters across (3.2x1012 meters)- 3 trillion meters: distance from Sun to a little beyond Neptune - Quasar- the size of our solar system with an energy output equal to 100 Milky Way Galaxies! Super-Massive Black Holes (SBH)- We saw earlier that SBH’s exist in the center of the galaxies- Well, Quasars are basically super massive black holes- Where you relative to the spin axis helps determine whether you are a Blazar, Quasar or Radio Galaxy - “As matter comes into the SBH, violent collisions along spin axis blasts light jets of light“Other Objects: -Radio Galaxies - similar to Quasars but no visible light - about 90 degrees on spin axis -Blazar- high luminosities, more signal- about 0 degrees on spin axis-Quasar - mix of radio and visible- about 45 degrees on spin axis Gamma-Ray Bursts- Emit energy for a short periodo range is somewhere between .001 seconds up to 1,000 seconds- 1 time event Unlike X-Ray Bursts (binary with at least 1 neutron star), gamma ray bursts only happen once. - Since late 1960’s, we have recorded at least 3,000- A typical GRB emits as much energy in one minute as our sun will emit over its entire10 billion year lifetime - 2 sources behind Gamma Ray Bursts:I. Binary system of 2 neutron stars (collide explosion)II. Binary system of a black hole and a neutron star (“neutron star orbit decayed, gravitational forces so strong basically smash like pancake”; black hole swallows neutron star) Announcements: I. The rest of the quizzes should now fall on a Thursday. II. The Final Exam will not be comprehensive, but just another test.III. Quiz #9 will be this Thursday April
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