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How Big Can the Black Hole Be?. Hunter Zhao 05/05/2007 Chandra Astrophysics Institute Thomas S. Wootton High School. Outline. Placing an upper limit on size of Sgr. A*. Light travel time argument, definition and ways we can obtain the upper limit.
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How Big Can the Black Hole Be? Hunter Zhao 05/05/2007 Chandra Astrophysics Institute Thomas S. Wootton High School
Outline • Placing an upper limit on size of Sgr. A*. • Light travel time argument, definition and ways we can obtain the upper limit. • Compare the quantitative results obtained from the model with the exact size estimation using Schwarzchild diameter.
Introduction and Background • Sagittarius A* is a supermassive black hole at the center of the Milky Way galaxy. • It involves placing an UPPER limit on the size of the most powerful astronomical object in space, what else can you ask for☺?
Event horizon – sphere of no return. • Several important assumptions will be made throughout my research (as will be explained later).
Data/Methods • Astronomers made continuous observations on the light-emitting behaviors of Sgr. A* and its accretions. • Chandra X-ray Observatory Telescope • Ds 9 Analysis Tool • I looked at images and light curves of Sgr. A*. • Light curve is a graphical visualization
Results Sgr. A* seen through telescopes that detect x-ray (top), radio (bottom left), and optical (bottom right) energies of light. Sgr. A* is located at the crosshairs.
The light curve shows a pattern of periodical light outbursts from Sgr. A* every intervals of 45,000 seconds (12.5 hours). The burst widths, as well as intensities, vary from burst to burst. Burst # 1 Duration: 7400 Burst # 3 Duration: 3965 Burst # 2 Duration: 6990 A screenshot of a light curve taken from an observation by CXO Telescope. The x-axis signifies time; the y-axis signifies intensity.
Discussion / Analysis • Nature of the periodical bursts. • A conceptual model for the occurrence. • Diameter (m) = Speed of Light (m/s) x Burst Width (s) • Optically thin. • Instantaneous burst. • A burst time greater than instantaneous would cause the burst width, as well as overall luminosity to increase.
Discussion / Analysis From left to right, top to bottom. My drawings for a graphical visualization of the process of the light curve’s formation during a burst from Sgr. A*. An estimated Sgr. A* diameter of 1 lightsecond is used (see assumptions).
Further into UPPER limit… • An upper limit means that the size of Sgr. A* cannot be any bigger than this estimation. • The size CAN be SMALLER. • The size of Sgr. A* stays CONSTANT. • Upper limit (glowing region): 1.19 x 1012 meters • Results yielded from Shortest burst width x Speed of light • About 8 times Earth’s orbit around the Sun. • Predicted Diameter (event horizon): 2.22 x 1010 meters • Found from known mass of Sgr. A*. • About 16 times diameter of the Sun. • Ratio : 54 (limit) : 1 (estimated diameter)
Questions • Is there a way to exclude the diameter of accretions around Sgr. A*? • What shape does the accretions around Sgr. A* form?
Conclusions • Upper limit of Sgr. A*. • Light travel time argument. • Comparison between estimated upper limit diameter and Schwarzchild diameter. • The results of this research can be used to restrict ways of determining actual size of Sgr. A*.
Acknowledgements • Special thanks to Mark, Fred, and Louis for helping me develop the model. • Acknowledgements to Ds9, MS Office, Texas Instruments. • A great audience like you!!!
