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Roberta Humphreys

Emeritus Faculty (Minnesota Institute for Astrophysics)

TATEH 285-07 (office), 624-6530
roberta @



Honors and Awards:
Fellow, AAAS 1980, Humboldt Senior Scientist Award, Federal Republic of Germany, 1988, George W. Taylor Research Award, Institute of Technology, 1985, Mullen-Spector-Truax Women's Leadership Award 2008, Honorary Fellow Royal Astronomical Society 2013

Professional Activities:
AAS Tinsley Prize Committee 1994-96, Chair 1995-96; AAS Nominating Committee 1998-2000, Chair, 2000; NASA UV/Optical Review Panel 1995; NASA Senior Review (Office of Space Science) 2001; NASA Senior Review (The Universe) 2006; NSF Special Review for AURA 2000, NSF Special Review Panel for ITR/NVO 2001; NVO Science Definition Team 2001-02; University of Minnesota Member Representative to AURA 2001- 2010, AURA Nominating Committee 2006, Space Telescope Institute Council (AURA) 2004-2010. Senate/Faculty Consultative Committee 1995-96, 1998-2000, Vice-Chair University/Faculty Senate 1995-96, 1999-2000; Senate 2007 - 2010; AAS Henry Norris Russell Prize Committee, 2011 – 2013, Chair SOC for Workshop on Outstanding Problems in Massive Star, 2012, NASA Senior Review of the Hubble Space Telescope, 2014

Note that during the “tenure wars” of 1995-96, when the Board of Regents and central administration tried to revise the tenure code and effectively remove tenure, I was one of the faculty leaders opposing the administration and worked with the AAUP during the collective bargaining campaign. As Associate Dean I was responsible for faculty affairs for the college including promotion and tenure. In 2005 I initiated and served as co-PI on an ADVANCE proposal to NSF for the advancement of women in science and engineering. I also led the organization of 16 Minnesota colleges and universities for the submission of an LSAMP proposal to NSF. The latter was successful

Summary of Interests
Luminous stars, stellar evolution, optical spectroscopy, galactic structure

About My Work

Roberta Humphreys’ studies of “Luminous Stars in Nearby Galaxies” (Papers 1 – VIII) demonstrated the existence of an empirical upper luminosity boundary in the HR Diagram and by implication an upper limit to the masses of stars that could evolve to become red supergiants (Humphreys & Davidson 1979). This upper limit, sometimes called the Humphreys-Davidson limit, was not predicted by theory and greatly influenced future work on massive star evolution. They suggested then and in two subsequent papers (1984, 1994) that massive stars above this limit encountered an instability, possibly due to the opacity-modified Eddington limit, and experienced high mass loss episodes which prevented their evolution to cooler temperatures. The Luminous Blue Variables (LBVs) and stars like eta Car are examples of this high mass loss phase. As part of this work she also obtained the first spectra and IR photometry of individual stars outside the Local Group. In recent years, she has used the HST to study individual evolved, cool stars that define this upper luminosity limit, the cool hypergiants. Using high resolution spectroscopy and multi-epoch imaging, she has found that some of these stars experience localized high mass loss events probably due to large scale convective activity.She also led the Automated Plate Scanner (APS) project for nearly 20 years. One of their major activities was the digitization of the POSS I and creation of the on-line database ( The APS group was the first to use neural networks for object classification. She and her students (Larsen, Parker and Cabanela) have used the database for large scale studies of the Milky Way.

Selected Publications

R. Humphreys et al., On the Social Traits of Luminous Blue Variables", ApJ, 825, 64 (2016)

R. Humphreys et al., Luminous and Variable Stars in M31 and M33. II. Luminous Blue Variables, Candidate LBVs, Fe II Emission Line Stars, and Other Supergiants, ApJ, 790, 48H (2014)

R Humphreys et al., Luminous and Variable Stars in M31 and M33. I. The Warm Hypergiants and Post-Red Supergiant Evolution, ApJ,773, 46H (2013)

R. Humphreys and K. Davidson (Eds.), Book: Eta Carinae and the Supernova Impostors, (2012)

R. Humphreys et al., The Photometric and Spectral Evolution of the 2008 Luminous Optical Transient in NGC 300, A.J. 743, 118 (2011)

R. M. Humphreys, T. C. Beers, J. E. Cabanela, S. Grammer, Y-S Lee, and J. A. Larsen, Mapping the Asymmetric Thick Disk. III. The Kinematics and Interaction with the Galactic Bar, (2011)

R. M. Humphreys, A. Mehner, K. Davidson, J. C. Martin, K. Ishibashi, G. Ferland, and N. Walborn, A Sea Change in Eta Carinae", A.J. Letters (2010)

R. M. Humphreys, K. Davidson, & M. Koppelman, The Early Spectra of Eta Carinae 1893 - 1941 and the Onset of Its High Excitation Emission Spectrum”, A.J. (2008)

R. M. Humphreys, L. A. Helton, & T. J. Jones , “The 3D Morphology of VY Canis Majoris I. The Kinematics of the Ejecta”, A.J. (2007)

R. M. Humphreys, K. Davidson, G. Ruch & G. Wallerstein, “High-Resolution, Long-Slit Spectroscopy of VY Canis Majoris: The Evidence for Localized High Mass Loss Events”, A.J. (2005)


Ph.D. Astronomy, University of Michigan, 1969
B. A. Astronomy, Indiana University, 1965