Unlike some science disciplines, there is no standard citation style for Physics or Astronomy. If your professor doesn't specify a certain style, here are some examples of citation styles of a variety of Astronomy & Physics references:
Journal Paper
Cohen D. H., Leutenegger M. A., Wollman E. E., Zsargo ́ J., Hillier D. J., Townsend R. H. D., Owocki S. P., 2010, MNRAS, 405, 2391
C. H. Crouch, O. Sauter, X. Wu, R. Purcell, C. Querner, M. Drndic, and M. Pelton, Nano Lett. 10, 1692 (2010).
In-text Citation: (Crouch 2010, 1692)
Book (Where specific pages of a book are cited, these should be given at the text citation, not in the reference list.)
Hamann W.-R., Feldmeier A., Oskinova L. M., eds, 2008, Clumping in Hot Star Winds. Universitatsverlag, Potsdam
Donat, W., III, & Boksenberg, A. J. 1993, The Astronomical Almanac for the Year 1994, Vol. 2 (2nd ed.; Washington, DC: GPO)
In-text citation: (Donat 1994)
Paper or Chapter in a Collection
Huchra, J. P. 1986, in Inner Space/Outer Space, ed. E. W. Kolb et al. (Chicago, IL: Univ. Chicago Press), 65
In-text Citation: (Huchra 1986, 65)
Conference Proceedings
Salpeter, E. E., & Wasserman, I. M. 1993, in ASP Conf. Ser. 36, Planets around Pulsars, ed. J. A. Phillips, S. E. Thorsett, & S. R. Kulkarni (San Francisco, CA: ASP), 345
In-text Citation: (Salpeter 1993, 345)