Charles H. Townes

Professor of the Graduate School
Astrophysics Experimental
http://isi.ssl.berkeley.edu

Research Interests

I am interested in astrophysics broadly. My primary research at present involves very high angular resolution astronomy in the mid-infrared (10 micron wavelength region) by use of interferometric techniques. Three 1.65 meter telescopes mounted in trailers have been constructed so that interferometry can be carried out at various baselines. They are installed on Mt. Wilson, and are obtaining good results. The first two represented the first time that very high angular resolution was made available on a regular basis in the mid-infrared region. Construction of the third similar telescope provides three baselines simultaneously rather than our previous single one between the two telescopes, which allows two-dimensional imaging and management of asymmetries. Scientific objectives include: 1) the angular resolution, proper motions, and study of protostars or unusual stars hidden in the dust clouds of their origin; 2) angular resolution of late-type stars, the molecules and solids formed from their emissions, and their dynamics; 3) high resolution determination of where and how molecules are formed around stars; and 4) high resolution mapping of other important infrared objects.

Current Projects

Examples of our work include demonstration that old stars throw off substantial material episodically on time scales of 10-100 years, discovery of a recent episode in which Betelgeuse suddenly emitted a large amount of gas, measurement of Betelgeuse's diameter, and discovery that it is not circular. These represent the first measurement of a stellar size at mid-IR wavelengths, giving a much more reliable (and somewhat larger) size because of the non-uniform brightness in the visible region, including darkening at the edges of the star due to its atmosphere. The variable star Mira has recently been measured and shown to be appreciably larger than previously thought, as well as to throw off dust shells somewhat irregularly. We have also measured its change in size over its yearly period. We see motion of material around a number of stars. And spatial interferometry on spectral lines has been carried out. This allows study of the formation and conditions of molecular material in stellar atmospheres and surroundings.

Selected Publications

W. C. Danchi, M. Bester, C. G. Degiacomi, L. J. Greenhill, and C. H. Townes, “Characteristics of dust shells around thirteen late-type stars,” AJ107, 1469 (1994).

R. Genzel, D. Hollenbach, and C.H. Townes, “The nucleus of our galaxy,” Rep. Prog. Phys.57, 417 (1994).

A. Poglitsch, N. Geis, R. Genzel, F. Herrmann, J. M. Jackson, S. C. Madden, T. Nikola, G. J. Stacey, and C. H. Townes, “Far-infrared observations at the center of the galaxy,” The Nuclei of Normal Galaxies, R. Genzel and A.I. Harris (Eds.), 445, p. 239, Kluwer (1994).

W. C. Danchi, L. Greenhill, M. Bester, C. G. Degiacomi, and C. H. Townes, “Long baseline interferometric observations of circumstellar dust shells at 11 microns,” Very High Angular Resolution Imaging, J. G. Robertson and W. J. Tango (Eds.), 383, Kluwer (1994).

R. N. Treuhaft, S. T. Lowe, M. Bester, W. C. Danchi, and C. H. Townes, “Vertical scales of turbulence at the Mount Wilson Observatory,” Ap. J.453, 522 (1995).

L. J. Greenhill, F. Colomer, J. M. Moran, D. C. Backer, W. C. Danchi, M. Bester, and C. H. Townes. “The circumstellar envelope of VX Sgr,” Ap. J.449, 365 (1995).

M. Bester, W. C. Danchi, D. Hale, C. G. Degiacomi, C. H. Townes, D. Mèkarnia, and T. Geballe, “Measurement at 11 micron wavelengths of the diameters of Alpha Ori and Alpha Sco; changes in effective temperature of Alpha Ori and very recent dust emission,” Ap. J.463, 336 (1996).

A. Poglitsch, R. Genzel, S. Madden, T. Nikola, R. Timmermann, N. Geis, and C. H. Townes, “Far infrared fine structure line observations of the galactic center radio arc,” in The Galactic Center, R. Gredel (Ed.), ASP Conf. Series 102, 114 (1996).

C. H. Townes, “A physicist courts astronomy,” Prefatory Chapter IN Annual Review Astronomy and Astrophysics,” Vol. 35 (1997).

S. Madden, A. Poglitsch, N. Geis, G. J. Stacey, and C. H. Townes, “[C II] 158 micron observations of IC 10: evidence for hidden molecular hydrogen in irregular galaxies,” Ap. J. 483, 200 (1997).

J. D. Monnier, M. Bester, W. C. Danchi, M. A. Johnson, E. A. Lipman, C. H. Townes, P. G. Tuthill, and T. R. Geballe, “Observations and modeling of the nonuniform dust outflow around the red supergiant NML-Cygni,” in A Half Century of Stellar Pulsation Interpretations: A tribute to Arthur N. Cox, P.A. Bradley and J.A. Guzik (Eds.), APS Conference Series 135, p. 329 (1998).

T. Nikola, R. Genzel, F. Hermann, S. C. Madden, A. Poglitsch, N. Geis, C. H. Townes, and G. J. Stacey, “[CII] emission from NGC 4038/39 (The “Antennae”),” Max-Planck-Institute fur Extraterrestrische Physik, Preprint 441, (1998) Ap. J. (in press).

J. D. Monnier, W. C. Danchi, D. S. Hale, P. G. Tuthill, and C. H. Townes, “Mid-infrared interferometry on spectral lines: III ammonia and silane around IRC + 10216 and VY CMa”, Ap. J.543, 868 (2000).

J. Weiner, W. C. Danchi, D. D. S. Hale, J. McMahon, C. H. Townes, J. D. Monnier, and P. G. Tuthill, “Precision measurements of the diameters of Orionis and Ceti at 11 microns,” Ap. J.544, 1097 (2000).

N. Short, W. Fitelson, D. Hale, and C. H. Townes, “Low Altitude Atmospheric Turbulence Characteristics at Mt. Wilson Observatory” Proceedings of SPIE, V488, 803 (2003)

J. Weiner, D. Hale, C. H. Townes, “The Variability of Late-Type Stars Diameters Measured Using Mid-Infrared Interferometry”, “Interferometry for Optical Astronomy II”, Conferences, August 22-28, 2002, Waikolea, Hawaii, Proceedings of SPIE, Vol 4838. 172-180, 2003

J. Weiner, D. D. S. Hale, and C. H. Townes, “Asymptotic Giant Branch and Supergiant Stellar Diameters in the Mid-Infrared”, ApJ, Vol. 589, 976 (2003)

S. Tevousjan, J. Weiner, K. S. Abdeli, D. D. S. Hale, C. H. Townes, “Mid-Infrared Interferometry on Dust Shells around 4 Late Type Stars”, ApJ, Vol 611, 466 (2004)

J. Weiner, K. Tatebe, D. D. S. Hale, C. H. Townes, J. Monnier, M. Ireland, P. Tuthill, R. Cohen, R. K. Barry, J. Rajagopol, W. C. Danchi, “The Asymmetrical Dust Environment of IK Tau”, Ap.J. 636-1067 (2006)

K. Tatebe, A.A. Chandler, D.D.S. Hale, and C.H. Townes, “Characteristication of Dust Shell Dynamics and Asymmetry for 6 Mira-Type Stars, ApJ. 652, 666 (2006)
K. Tatebe, D.D.S. Hale, E.H. Wishnow, and C.H. Townes, Observation of a Burst of High-Velocity Dust from - Herculis, ApJ. Letters ~ April, 2007