1. Black Holes Katryna Fast

2. Formation A black hole is generally the end state of high mass stars – more than 25 solar massesA black hole is generally the end state of high mass stars – more than 25 solar masses Neutron stars have a similar limit to the Chandrasekhar limit – a mass at which the gravitational force overwhelms neutron degeneracy pressure and the star collapses.Neutron stars have a similar limit to the Chandrasekhar limit – a mass at which the gravitational force overwhelms neutron degeneracy pressure and the star collapses. This limit is approximately 3 solar massesThis limit is approximately 3 solar masses The gravitational force eventually becomes so strong that nothing – including light – can escape. 1The gravitational force eventually becomes so strong that nothing – including light – can escape. 1 Black holes cannot be observed through electromagnetic radiation, instead they are studied by their effects on nearby stars and other matter 2.Black holes cannot be observed through electromagnetic radiation, instead they are studied by their effects on nearby stars and other matter 2. 1. Astronomy Today – Chaisson and MacMillan 2. http://science.nasa.gov/astrophysics/focus-areas/black-holes/

3. Background information Black holes have an event horizon, which can be thought of as the surface of the black hole.Black holes have an event horizon, which can be thought of as the surface of the black hole. Black holes have a Schwarzschild radius at which objects will be so greatly affected by its gravitational attraction that it will be pulled apart into the black hole.Black holes have a Schwarzschild radius at which objects will be so greatly affected by its gravitational attraction that it will be pulled apart into the black hole. The Schwarzschild radius is proportional to the mass of the black hole. 1The Schwarzschild radius is proportional to the mass of the black hole. 1 The Schwarzschild radius of the Earth is approximately 1 cm.The Schwarzschild radius of the Earth is approximately 1 cm. 1.Astronomy Today – Chaisson and MacMillan

4. Supermassive black holes Supermassive black holes are much larger than regular black holesSupermassive black holes are much larger than regular black holes They are found at the center of galaxies, and how they are formed is still a mysteryThey are found at the center of galaxies, and how they are formed is still a mystery They are not formed as a result of a supernovaThey are not formed as a result of a supernova They have been detected by observations of material orbiting the center of the galaxy, the conditions of which are unexplainable without a massive gravitational force acting upon the material.They have been detected by observations of material orbiting the center of the galaxy, the conditions of which are unexplainable without a massive gravitational force acting upon the material. Not all galaxies have supermassive black holes, but most doNot all galaxies have supermassive black holes, but most do The supermassive black hole at the center of our Milky Way galaxy is called Sagittarius A*. 3The supermassive black hole at the center of our Milky Way galaxy is called Sagittarius A*. 3 3. http://astronomy.swin.edu.au/cosmos/S/Supermassive+Black+Hole

5. Sagittarius A* stats Name often shortened to SgrA*Name often shortened to SgrA* It is named for it’s position in the constellation of SagittariusIt is named for it’s position in the constellation of Sagittarius It is located 26,000 light years from our Solar System 4It is located 26,000 light years from our Solar System 4 It has an estimated mass of 4.5 million solar masses 5It has an estimated mass of 4.5 million solar masses 5 It’s event horizon is 0.02 AU 6.It’s event horizon is 0.02 AU 6. 4. http://www.nasa.gov/mission_pages/chandra/multimedia/black-hole-SagittariusA.html 5. http://science.nasa.gov/science-news/science-at-nasa/2015/06jan_saga/ 6. Astronomy Today – Chaisson and MacMillan

6. Press release NASA’s Chandra Detects Record-Breaking Outburst from Milky Way’s Black Hole 7 NASA’s Chandra Detects Record-Breaking Outburst from Milky Way’s Black Hole 7 January 05, 2015January 05, 2015 While observing SgrA* in hopes of seeing how it would react with the approaching G2 cloud, astronomers using the Chandra telescope observed the brightest X-ray flare ever observed from the black hole.While observing SgrA* in hopes of seeing how it would react with the approaching G2 cloud, astronomers using the Chandra telescope observed the brightest X-ray flare ever observed from the black hole. A year later, another incredibly bright flare was observed.A year later, another incredibly bright flare was observed. The two prevailing theories about these flares area:The two prevailing theories about these flares area: A large asteroid being drawn into SgrA*and the debris heated and produced X-rays before passing the event horizonA large asteroid being drawn into SgrA*and the debris heated and produced X-rays before passing the event horizon Magnetic field lines of gas entering SgrA* became tightly packed and tangled, then rearranged themselves and resulted in an X-ray outburstMagnetic field lines of gas entering SgrA* became tightly packed and tangled, then rearranged themselves and resulted in an X-ray outburst 7. http://chandra.harvard.edu/press/15_releases/press_010515.html

7. An X-ray image of the area surrounding SgrA* before and after the first flare taken by the Chandra telescope in partner with NASA and Northwestern University. 7 7. http://chandra.harvard.edu/press/15_releases/press_010515.html

8. Article 1 Echoes of multiple outbursts of Sagittarius A* revealed by Chandra 8 Echoes of multiple outbursts of Sagittarius A* revealed by Chandra 8 M. Clavel, R. Terrier, A. Goldwurm, M.R. Morris, G. ponti, S. Soldi, and G. TrapM. Clavel, R. Terrier, A. Goldwurm, M.R. Morris, G. ponti, S. Soldi, and G. Trap Published by Astronomy & AstrophysicsPublished by Astronomy & Astrophysics 12 July 201312 July 2013 8. http://www.aanda.org/articles/aa/abs/2013/10/aa21667-13/aa21667-13.html

9. PURPOSE This paper discusses the changing luminosity of SgrA* and focuses on studying variable emissions in Fe K α and the region between SgrA* and the Radio Arc, which is the area where the strongest variations were detected.This paper discusses the changing luminosity of SgrA* and focuses on studying variable emissions in Fe K α and the region between SgrA* and the Radio Arc, which is the area where the strongest variations were detected. They used Chandra’s high-spatial resolution to highlight the fine structure in variable illumination.They used Chandra’s high-spatial resolution to highlight the fine structure in variable illumination. They localized the non-thermal emission in SgrA* to provide an overview of its variationsThey localized the non-thermal emission in SgrA* to provide an overview of its variations They analyzed small-scale variations over a large area of the region with the largest detected variationsThey analyzed small-scale variations over a large area of the region with the largest detected variations

10. Observations The authors use observations from the Chandra telescope to map past energy fluctuations from SgrA*The authors use observations from the Chandra telescope to map past energy fluctuations from SgrA* They map the brightest emissions of SgrA* for the years which they were able to get data for, both including their own observations and data previously recorded by ChandraThey map the brightest emissions of SgrA* for the years which they were able to get data for, both including their own observations and data previously recorded by Chandra

11. Conclusion In order to produce the bright filament that was observed in 2011, the luminosity must have been at least 10 39 erg s -1In order to produce the bright filament that was observed in 2011, the luminosity must have been at least 10 39 erg s -1 There was a two-year peaked emission that propagated through the Bridge – an area between a molecular cloud and SgrA*There was a two-year peaked emission that propagated through the Bridge – an area between a molecular cloud and SgrA* There were ten-year linear variations in all bright molecular structures in the area with the brightest fluctuations except for the Bridge.There were ten-year linear variations in all bright molecular structures in the area with the brightest fluctuations except for the Bridge. These behaviours are suspected to be due to reflection of two particular flares of SgrA* from the past.These behaviours are suspected to be due to reflection of two particular flares of SgrA* from the past.

12. Article 2 CHANDRA/HETGS Observations of the brightest flare seen from SgrA* 9 CHANDRA/HETGS Observations of the brightest flare seen from SgrA* 9 M.A. Nowak, J. Neilsen, S.B. Markoff, F.K. Baganoff, D. Porquet, N. Grosso, Y. Levin, J. Houck A. Eckart, H. Falke, L. Ji, J.M. Miller, and Q.D. WangM.A. Nowak, J. Neilsen, S.B. Markoff, F.K. Baganoff, D. Porquet, N. Grosso, Y. Levin, J. Houck A. Eckart, H. Falke, L. Ji, J.M. Miller, and Q.D. Wang Published by the Astrophysical JournalPublished by the Astrophysical Journal 10 November 201210 November 2012 9. http://iopscience.iop.org/article/10.1088/0004-637X/759/2/95/meta;jsessionid=68CBD33CAB0266F38CC569BD5080D386.c1

13. Purpose Previous observations show that SgrA* has a luminosity far lower than other nearby active galactic nuclei with low luminosity.Previous observations show that SgrA* has a luminosity far lower than other nearby active galactic nuclei with low luminosity. It is the goal of this paper to place SgrA* as either a “quiescent” galactic nuclei or as on the low end of active galactic nucleiIt is the goal of this paper to place SgrA* as either a “quiescent” galactic nuclei or as on the low end of active galactic nuclei The authors also seek to understand the nature of the flares observed from SgrA*The authors also seek to understand the nature of the flares observed from SgrA* During their observations, the brightest flare to-date was observed and an analysis of the flare’s components is provided, and the flare is compared two other bright flares from past observations.During their observations, the brightest flare to-date was observed and an analysis of the flare’s components is provided, and the flare is compared two other bright flares from past observations.

14. Observations The authors use observations from the Chandra telescopeThe authors use observations from the Chandra telescope They focus on a bright flare which occurred in 2012They focus on a bright flare which occurred in 2012 They use these observations to analyze the spectra of SgrA* in its quiescent state and use this analysis to determine the luminosity of the observed bright flare.They use these observations to analyze the spectra of SgrA* in its quiescent state and use this analysis to determine the luminosity of the observed bright flare.

15. Conclusions The bright flare observed is seen to be similar in many ways to two of the other brightest flares, compared by way of spectral analysis.The bright flare observed is seen to be similar in many ways to two of the other brightest flares, compared by way of spectral analysis. They determine that the mechanism to emit the bright flares must produce a moderate photon index, as opposed to the harder spectra than weaker flares are theorized to have.They determine that the mechanism to emit the bright flares must produce a moderate photon index, as opposed to the harder spectra than weaker flares are theorized to have.

16. References 1.Chaisson E, McMillan S. 2014. neutron stars and black holes strange states of matter. Astronomy Today. Whilton N, Kenney L, Goodwin T. 8: p. 555-557 2.NASA. 2015. Black holes. science.nasa.gov. 3.Swinburne University of Technology 4.NASA. 2013. Supermassive black hole Sagittarius A*. nasa.gov. 5.NASA. 2015. NASA’s Chandra detects record-breaking outburst from milky way’s black hole. science.nasa.gov. 6.Chaisson E, McMillan S. 2014. the milky way galaxy a spiral in space. Astronomy Today. Whilton N, Kenney L, Goodwin T. 8: p. 601-602. 7.2015. Sagittarius A*: NASA’s chandra detects record-breaking outburst from milky way’s black hole. Chandra X-Ray Observatory. 8.Clavel M, Terrier R, Goldwurm A, Morris MR, Ponti G, et al. 2013. Echoes of multiple outbursts of Sagittarius A* revealed by chandra. A&A. 558: A32. 9.Nowak MA, Neilsen J, Markoff SB, Baganoff FK, Porquet D, et al. 2012. Chandra/HETGS observations of the brightest flare seen from SgrA*. ApJ. 759: 95, 9 pages.