Sergio Dieterich
NSF Postdoctoral Fellow

Serge Dieterich

Research Interests

Very low mass stars and brown dwarfs; astrometry; stellar masses; the solar neighborhood; stellar populations; observational tests of stellar structure; physics and astronomy education


B.A., Physics, Johns Hopkins University, 2003
M.S., Physics, Georgia State University, 2013
Ph. D., Astronomy, Georgia State University, 2013

Contact & Links

  • (202) 478-4885 | fax: (202) 478-8821
  • sdieterich at
  • Department of Terrestrial Magnetism
    Carnegie Institution of Washington
    5241 Broad Branch Road, NW
    Washington, DC 20015-1305
  • curriculum vitae
  • Publications
  • Personal Website


Serge Dieterich
Radius Diagram for a sample of nearby stellar and substellar objects nearing the stellar/substellar boundary. In keeping with astronomical tradition the value of the luminosity axis decreases from left to right. All objects have had their precise distances determined through astrometry. For brighter objects radius decreases with luminosity, as is expected for stars. There is then a sudden jump in radius for objects fainter than 2MASS J0523-1403. This behavior is expected if the fainter objects are young brown dwarfs that have not yet had the time to fully contract. A few objects with larger radii trace out a second sequence above the stellar main sequence . These objects are thought to be very young brown dwarfs or unresolved binary stars.The smallest star, 2MASS J0523-1403, is nearly the same size as the planet Saturn.

Sergio (Serge) Dieterich is an observational astronomer who studies the properties of the smallest stars in the solar neighborhood and the differences and similarities between these stars and their lower mass substellar cousins, the brown dwarfs. He is particularly interested in how stellar structure and evolution processes happening deep within the core of a star or brown dwarf are related to the colors and spectroscopic features of the surface of the star, which is the only part probed by telescope observations. Serge also specializes in the technique of astrometry, which measures minute changes in the relative position of a star in the sky to determine the star’s distance from Earth as well as any orbital motion the star may have about an unseen companion.

While working on his Ph.D. at Georgia State University Serge combined the techniques of astrometry and photometry (the measurement of the brightness and colors of a star) to estimate the radii and temperatures of a large sample of objects thought to lie close to the stellar/substellar mass boundary. Serge and his collaborators noticed a gap and sudden jump in stellar radius trends for stars that shine with roughly one ten-thousandth the energy of our Sun, and have interpreted that break as a possible indication of the temperature and brightness where the stellar sequence ends and the brown dwarfs take over. Serge will now use the powerful telescopes of Carnegie’s Las Campanas Observatory to study an even larger sample of objects and probe questions such as how stellar chemical composition and stellar surface gravity affect these trends.

Serge was born in Porto Alegre, Brazil, and moved to Miami, Florida, just before starting high school. He has a B.A. in physics from Johns Hopkins University, an M.S. in physics from Georgia State University, and recently obtained his Ph.D. in astronomy also from Georgia State. After college and before starting graduate school Serge taught high school physics and middle school physical science for two years.