Dark Matter Search

By regularly observing millions of stars in the Large Magellanic Cloud (a close neighbor galaxy) and the Galactic bulge it is possible to observe instances of gravitational microlensing in which the gravitational field of a dark or dim foreground object serves as a lens to magnify the apparent brightness of a brighter source star. With my colleagues on the MACHO project, I have used this gravitational microlensing technique to study the structure of our Galaxy and the composition of the dark matter which dominates the mass of our Galaxy. Our latest results suggest that we have discovered at least some of the Galactic dark matter in the form of MAssive Compact Halo Objects (or MACHOs) with a mass between 0.1 and 1 solar mass. It is possible that these MACHOs are white dwarf stars.

References

• "The MACHO Project LMC Microlensing Results from the First Two Years and the Nature of the Galactic Dark Halo", C. Alcock, R.A. Allsman, D. Alves, T.S. Axelrod, A.C. Becker, D.P. Bennett, K.H. Cook, K.C. Freeman, K. Griest, J. Guern, M.J. Lehner, S.L. Marshall, B.A. Peterson, M.R. Pratt, P.J. Quinn, A.W. Rodgers, C.W. Stubbs, W. Sutherland, D.L. Welch (The MACHO Collaboration), Ap. J., in press (1997) (astro-ph/9606134).
• "Experimental Limits on the Dark Matter Halo of the Galaxy from Gravitational Microlensing", "C. Alcock, C. Akerlof, R. Allsman, T. Axelrod, D.P. Bennett, K.H. Cook, K. Freeman, K. Griest, S. Marshall, S. Perlmutter, B. Peterson, M.R. Pratt, P. Quinn, A. Rogers, C.W. Stubbs, and W. Sutherland (The MACHO Collaboration), Phys. Rev. Lett., 74, 2867 (1995).

For more information about this research project of the Astrophysics Group, please send us an e-mail to bennett@nd.edu or check the MACHO Project Website.