supermassive black holes preserving a galactic treasure

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Supermassive Black Holes

Supermassive Black HolesPreserving a Galactic Treasure

Galaxy Structure and Classification (Easy)

http://upload.wikimedia.org/wikipedia/commons/2/21/HubbleTuningFork.jpg2Galaxy Structure and Classification (Harder)

http://sings.stsci.edu/Publications/sings_poster.html3Parts of a Spiral Galaxy(Supermassive Black Hole)

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http://en.wikipedia.org/wiki/File:Milky_way_profile.svg4Supermassive Black Holes (SBH)Sgr A* (pronounced: Sagittarius A-star)Strong radio source inthe center of the MilkyWay galaxy (our galaxy)Mass = 4 x 106 MM87 (supergiantelliptical galaxy)Contains a SBH at itscenterMass = 6.6 x 109 M

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https://commons.wikimedia.org/wiki/File:Sagittarius_A_Light_bulb.jpg5Proof of Existence for Sgr A*The mass of the central (and not visible) object can be found from the velocities of nearby stars orbiting it.

These images/animations were created by Prof. Andrea Ghez and her research team at UCLA and are from data sets obtained with the W. M. Keck Telescopes.

http://www.astro.ucla.edu/~ghezgroup/gc/pictures/orbitsMovie.shtml6How to Weigh a Black HoleAssume the mass of the star is insignificant compared to the mass of the central objectAssumption based on the fact that the central object does not appear to move.This eliminates the M2 term.Use a form of Keplers Third Law.See equation practice sheet for quantities and units.

Schwarzschild RadiusHow big is a black hole? Based on the mass, we can calculate the distance from the singularity from which no light can escape.This is called the Schwarzschild radius.Equation is derived using the escape velocity.See equation practice sheet for quantities and units.

Diameter of a Black HoleIf we have both the linear diameter (RSch) and the distance to the black hole, we can calculate the angular diameter.Relate these using the small angle formula See equation practice sheet for quantities and units.

Trying to Observe the Galactic CenterRadio Observable but very low resolutionMicrowave Observable but requires VLBI for good resolutionInfrared Observable but highly blurred by Earths atmosphereVisible Cannot pass through all the dust in the galactic diskUV/X-ray/Gamma Not observable on Earth

VBLI = Very Long Baseline Interferometry (This is a technique which uses radio/microwave telescopes around the world at the same time observing the same object in order to create the effect of a telescope the size of the earth. This creates higher resolution images.)10What We Expect to see in Radio When We Observe Sgr A*

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http://eventhorizontelescope.org/science/images/figure4_web.jpg11Supermassive Black Hole Activity