Gulbis: Stellar Occultations
- Image of Pluto (bright object) and Charon (faint blue object at lower left) while the star C313.2 was being occulted by Charon on 11 July 2005. This image was taken using POETS on one of the 6.5-m Magellan telescopes at Las Campanas Obs.
Stellar occultations, or the light from a star being blocked as it passes behind a foreground object, provide significant information on bodies in the outer solar system. Observations of these events offer some of the highest spatial resolution data that is achievable from Earth (on the order of a few km at Pluto). Therefore, stellar occultations are employed to determine planetary diameters and to probe the temperature and pressure profiles of planetary atmospheres. These events can also lead to the discovery of features such as satellites, rings, and atmospheres.
During a stellar occultation, the shadow created on the Earth is a function of the size of the body and its distance from the Earth. For the objects in which we are interested (particularly Pluto & Charon and Kuiper Belt objects), the shadow is significantly smaller than the Earth's angular diameter. An observer must thus be in the right place at the right time to see the occultation. My colleagues at MIT spend considerable time and effort taking observations and performing astrometry (measuring object and star positions) in order to predict these events. We then use portable CCD camera systems, which can be taken all over the world and attached either to portable telescopes or to telescopes that are located in the predicted shadow path.
Recent observations include two stellar occultations by Pluto and one by Charon: P445. 3 (from the S.W. US; Hubbard et al. 2009, Person et al. 2008 & McCarthy et al. 2008), P384.2 (from Australia; Elliot et al. 2007), and C313.2 (from S. America; Person et al. 2007 & Gulbis et al. 2006a).In 2009, we had the first successful observation of a stellar occultation by a KBO other than Pluto or Charon: 55636 (Elliot et al. 2010). These observations allowed us to place important physical constraints on this Haumea-family object.
We are currently working on predicting stellar occultations by large Kuiper Belt objects (KBOs), in order to determine object diameters and search for binaries and atmospheres.
Stellar Occultation Publications:
Elliot, J. L., M. J. Person, A. A. S. Gulbis, S. P. Souza, E. R. Adams, B. A. Babcock, J. W. Gangestad, A. E. Jaskot, E. A. Kramer, J. M. Pasachoff, R. E. Pike, C. A. Zuluaga, A. S. Bosh, S. W. Dieters, P. J. Francis, A. B. Giles, J. G. Greenhill, B. Lade, R. Lucas, and D. J. Ramm, Changes in Pluto's Atmosphere: 1988-2006, Astronomical Journal, 134, 1-13, 2007.
Elliot, J.L., M.J.Person, C.A. Zuluaga, A.S. Bosh, E.R. Adams, T.C. Brothers, A.A.S. Gulbis, S.E. Levine, M. Lockhart, A.M. Zangari, B. Babcock, K. Dupre, J.M. Pasachoff, S. Souza, W. Rosing, N. Seacrest, L. Bright, E.W. Dunham, S. Sheppard, T. Tilleman, B. Berger, J. Briggs, G. Jacobson, P. Valleli, B. Volz, S. Rapaport, B. Carter, R. Hart, M. Brucker, E.G. Schmidt, R. Michel, A. Mattingly, L. Zambrano-Marin, A. Meyer, J. Wolf, E.V. Ryan, W.H. Ryan, K. Morzinski, B. Grigsby, J. Brimacombe, D. Ragozzine, H.G. Montano, An Old World with a Fresh Surface, Nature, 465, 897-900, 2010.
Gulbis, A. A. S, J. L. Elliot, M. J. Person, E. R. Adams, B. A. Babcock, M. Emilio, J. W. Gangestad, S.D. Kern, E. A. Kramer, D. J. Osip, J. M. Pasachoff, S. P. Souza, and T. Tuvikene, Charon's radius and atmospheric constraints observations of a stellar occultation , Nature, 439, 48-51, 2006.
Hubbard, W.B., D.W. McCarthy, C.A. Kulesa, S.D. Benecchi, M.J.Person, J.L. Elliot, and A.A.S. Gulbis, Buoyancy Waves in Pluto’s High Atmosphere, Icarus, 204, 284-289, 2009.
McCarthy, D., C. Kulesa, W. Hubbard, S. D. Kern, M. J. Person, J. L. Elliot and A. A. S. Gulbis, Occultation Measurement of Gravity Wave Breaking in Pluto's High Atmosphere, Astronomical Journal,136, 1519-1522, 2008.
Person, M. J. , J. L. Elliot, A. A. S. Gulbis, C. A. Zuluaga, B. A. Babcock, A. J. McKay, J. M. Pasachoff, S. P. Souza, W. B. Hubbard, C. A. Kulesa, D. W. McCarthy, S. D. Kern, S. E. Levine, A. S. Bosh, E. V. Ryan, W. H. Ryan, A. Meyer and J. Wolf, Waves in Pluto's Upper Atmosphere, Astronomical Journal, 136, 1510-1518, 2008.
Person, M.J., J.L., Elliot, A.A.S. Gulbis, J.M. Pasachoff, B.A. Babcock, S.P. Souza, and J. Gangestad, Charon's Radius and Density from the Combined Data Sets of the 2005 July 11 Occultation, Astronomical Journal, 132, 1575-1580, 2006.