17 D. A. Swartz et al. The Ultraluminous X-ray Source Population from the Chandra Archive of Galaxies. Astrophysical Journal. Suppl., ser. 154, no. 2 (2004).

18 Doppler Shift. Imagine the Universe! NASA, Goddard Space Flight Center, May 5, 2016. https://imagine.gsfc.nasa.gov/features/yba/M31_velocity/spectrum/doppler_more.html

19 American Institute of Physics online history archive. World Fame I. https://history.aip.org/history/exhibits/einstein/fame1.htm

1 Polarization Light Waves and Color. Lesson 1. How Do We Know Light Is a Wave? Polarization. The Physics Classroom. www.physicsclassroom.com/class/light/Lesson-1/Polarization

2 V. Radhakrishnan, N. Manchester. Detection of a Change

of State in the Pulsar PSR 0833–45. Nature. 222 (1969): 228–229; P. E. Reichley, G. S. Downs. Observed Decrease in the Periods of Pulsar PSR 0833–45. Nature. 222 (1969): 229–230.

3 R. N. Manchester. Pulsars at Parkes.

4 J. R. Oppenheimer, G. M. Volkoff. On Massive Neutron Cores.

5 V. Gribov et al. Arkady Migdal. Physics Today. 44, no. 12 (1991): 92.

6 Superfluids. University of Oregon. http://abyss.uoregon.edu/~js/glossary/superfluid.html

7 S. Balibar. The Discovery of Superfluidity. Journal of Low Temperature Physics. 146, nos. 5–6 (Mar. 2007): 441–470.

8 E. Gibney. Neutron Stars Set to Open Their Heavy Hearts. Nature News. May 31, 2017. www.nature.com/news/neutron-stars-setto-open-their-heavy-hearts-1.22070

9 R. R. Silbar, S. Reddy. Neutron Stars for Undergraduates. ArXivpre-print service, Nov. 26, 2003. https://arxiv.org/pdf/nucl-th/0309041.pdf

10 G. Ashton et al. Rotational Evolution of the Vela Pulsar during the 2016 Glitch. Nature Astronomy. 3 (2019): 1143–1148.

11 M. Riordan. The Discovery of Quarks. Stanford Linear Accelerator Center, Stanford University, Apr. 1992. www.slac.stanford.edu/cgi-wrap/getdoc/slac-pub-5724.pdf

12 J. M. Lattimer. Neutron Star Structure and the Equation of State. Astrophysical Journal. 550, no. 1 (2001).

13 H. T. Cromartie et al. Relativistic Shapiro Delay Measurements.

14 Our History: A Passion for Discovery, a History of Scientific Achievement. Brookhaven National Laboratory. www.bnl.gov/about/history

15 FAIR – The Universe in the Lab. Facility for Antiproton and Ion Research in Europe. https://fair-center.eu/

16 Shapiro Delay. COSMOS – The SAO Encyclopedia of Astronomy. http://astronomy.swin.edu.au/cosmos/S/Shapiro+Delay

17 T. Damour. 1974: The Discovery of the First Binary Pulsar. ArXivpre-print service, Feb. 17, 2015. https://arxiv.org/pdf/1411.3930.pdf

18 M. Kramer. Pulsars and General Relativity. Max Planck Institute for Radio Astronomy, Sept. 15, 2010. www.mpifr-bonn.mpg.de/1038767/Kramer_pulsars.pdf

19 M. C. Miller et al. PSR J0030 + 0451 Mass and Radius from NICER Data and Implications for the Properties of Neutron Star Matter. Astrophysical Journal Letters. 887, no. 1 (Dec. 12, 2019); T. E. Riley et al. A NICER View of PSR J0030 + 0451: Millisecond Pulsar Parameter Estimation. Astrophysical Journal Letters. 887, no. 1 (Dec. 12, 2019).

20 The Neutron Star Interior Composition Explorer Mission. Goddard Space Flight Center, NASA. https://heasarc.gsfc.nasa.gov/docs/nicer

21 A. Watts. Constraining the Neutron Star Equation of State Using Pulse Profile Modelling. AIP Conference Proceedings. 2127, no. 1 (2019).

22 K. Nandra et al. Athena: The Advanced Telescope for High-Energy Astrophysics. European Space Agency, 2013. www.cosmos.esa.int/documents/400752/400864/Athena+Mission+Proposal/18b4a058-5d43-4065-b135-7fe651307c46

23 Using Gravitational Wave Observations to Learn about Ultra-Dense Matter. LIGO, Aug. 12, 2019. www.ligo.org/science/Publication-GW170817ModelSelection/index.php

1 Making (Galactic) History with Big Data: First Global Age Map of the Milky Way. News release, Max Planck Institute for Astronomy, Jan. 8, 2016. www.mpia.de/news/science/2016–01-milky-way-agemap

2 South Africa’s MeerKAT Telescope Discovers Giant Radio ‘Bubbles’ at Centre of Milky Way. News release, SKA Telescope, Sept. 12, 2019. www.skatelescope.org/news/MeerKAT-discovers-giant-radio-bubbles