OCTOBER 13 - 17, 2008

TUESDAY, OCTOBER 14

2:30 pm: Joint CfA/MIT/Tufts Cosmology Seminar. "A Simple Model for DM Halos," Neal Dalal, CITA. Phillips Auditorium.

Abstract: The rarest, most massive dark matter halos are quite challenging to simulate numerically but also relatively easy to understand theoretically. I will describe how several aspects of massive halos may be understood using simple, self-similar collapse models. Combined with the (known) statistics of Gaussian random fields, this model makes predictions for the abundance and clustering of massive halos, with no adjustable parameters. This allows us to extend theoretical predictions for the halo mass function into regimes beyond the range of N-body simulations but accessible to ongoing cluster surveys.

WEDNESDAY, OCTOBER 15

2:30 pm: Solar, Stellar, and Planetary Sciences Division Seminar. "On the Importance of Being a Triple: From Binary Minor Planets to Blue Stragglers and Massive Black Holes," Hagai Perets, Weizmann Institute of Science. Phillips Auditorium.

Abstract: Triple gravitational systems are frequently observed at almost any astrophysical scale, from the solar system up to galactic scales. The dynamical evolution of such systems can be highly complex and lead to unique configurations in which tidal effects become important. I will discuss three examples of such triple systems: binary minor planets in the Solar system, binary blue stragglers observed in stellar clusters and the stellar disks observed in the Galactic center. Although very different in scale, I will suggest that same mechanism, secular perturbations (Kozai oscillations) of a binary system by a third object, have a major role in the evolution of each of these systems and the induced formation of unique and exotic objects.

In recent years binary minor planets (binary asteroids and binary trans-Neptunian objects) have been observed in the Solar system. Together with the sun these systems have a triple configuration. I will show that secular perturbations by the sun together with tidal friction can inherently change the orbits of these binaries and possibly induce their coalescence and the formation of irregular shaped minor planets. Blue stragglers are stars that seem much younger then the stellar population in which they are observed. Two main mechanisms have been suggested for their origin: either rejuvenation through through stellar collisions or through close binary mergers. I will suggest a third novel formation mechanism of blue stragglers from triple systems, which can explain many of their surprising properties, not explained by the currently studied mechanisms. Finally, I will discuss the evolution of the two nuclear disks observed to exist in the Galactic center around the massive black hole which together form a triple system.

4:00 pm: Initiative in Innovative Computing Colloquium Series. "Science Web 3.0 and Scientific Social Communities," Timothy Clark, Instructor in Neurology, Harvard Medical School; Director of Informatics, Mass General Institute for Neurodegenerative Disease; Core Member, Harvard Initiative in Innovative Computing. Room 330, 60 Oxford Street, Cambridge. Event parking is available at the 52 Oxford Street Garage [map]. Please inform the parking attendant you are attending the IIC seminar.

Abstract: Science Web 3.0 is an emerging system of semantically linked data, integrated with the Social Web, in support of science collaboration and scientific knowledge integration. This powerful environment for capturing, organizing and sharing scientific knowledge is now beginning to be taken up in real projects in the form of scientific social communities. IIC and its collaborators in the Harvard community are playing a leading role in this development.

THURSDAY, OCTOBER 16

11:00 am: Institute for Theory and Computation (ITC) Colloquium. "Stellar Dynamics Near Massive Black Holes: Young Stars, Hypervelocity Stars and Gravitational Wave Sources," Hagai Perets, Weizmann Institute. Pratt Conference Room.

Abstract: A massive black hole resides in the center of most, perhaps all galaxies. The one in the center of our home galaxy, the Milky Way, provides a uniquely accessible laboratory for studying in detail the connections and interactions between a massive black hole and the stars in its vicinity. Due to the the extreme conditions in this region (highest stellar densities, velocities and tidal fields) unique processes can occur there. These processes and their implication on the stellar population near the massive black hole open new possibilities in our understanding of gravitational dynamics and of post-Newtonian gravity in the weak- and strong-field limits. They may also explain and predict the existence of stars with exotic properties. In recent years young stars have been observed at the center of our Galaxy where such stars can not regularly form. At the outskirts of the Galaxy hypervelocity stars have been observed to escape from the Galaxy at extreme velocities. I will discuss the origin and evolution of these two unique population of stars and the possible connection between them, through the dynamical processes occurring near the massive black hole in the Galactic center. In addition I will discuss the possibility of using hypervelocity stars as probes of the Galactic potential the production of gravitational wave sources both in the Galactic center and in other galactic nuclei detectable by the planned Laser interferometer space antenna (LISA) mission and the possibility of directly probing the properties of the massive black hole in the Galactic center (its mass and its spin) and their general relativistic effects.

12 noon: Optical and Infrared Astronomy Division Lunch Talk. "Constraining the Nature of Star Formation at High Redshift," Dr. Kyoung-Soo Lee, Yale University. Room M-340, 160 Concord Avenue.

Abstract: Our improved understanding of dark-matter halo statistics can be effectively used to extract useful physical information directly from the observed galaxy statistics commonly measured from large galaxy surveys, such as luminosity function and clustering properties (luminosity-dependent trend and overall shape) of galaxies. I will discuss a simple formalism to constrain the scaling laws between UV luminosity and halo mass (local gravity), and the typical duration of star-formation at z~4 and 5. From these results, possible dominant mechanisms responsible for star-formation activity in the majority of galaxies (LL) are discussed.

4:00 pm: Colloquium. Speaker: Prof. Andy Fabian, Institute of Astronomy, Cambridge. Topic: To be announced. (Anyone wishing to meet with the speaker should contact the host, Prof. Julia Lee, 6-7521.) Preceded by tea at 3:30 pm. Phillips Auditorium.

7:30 pm: Monthly Observatory Night for the Public. "Measuring the Universe," Dr. Mark Reid, CfA. The lecture will be followed by telescopic observing, weather permitting. No tickets or reservations are necessary; however, seating is to the capacity of the hall. Doors open at 7:00 pm. Phillips Auditorium.

Abstract: Over 2,000 years ago, the Greek scientist Hipparchus measured the distance to the Moon by triangulation from two locations across the Mediterranean Sea. Determining the distance to stars proved much more difficult, and it was not until the 19th century that this was accomplished. Even in the early 20th century, the nature of nebulae was debated: were they nearby objects or distant "island universes" (galaxies)? While we now know the distance to galaxies at the edge of the Universe, we have only just begun to measure distances accurately throughout the Milky Way and hope to learn what it really looks like.

FRIDAY, OCTOBER 17

9:00 am - 5:00 pm: The Chandra Fellows Symposium. Data from the Chandra X-ray Observatory have provided stunning images, surprises and new insights. Chandra Fellows will present highlights of their recent work on X-ray related topics such as black holes, X-ray binaries, supernovae, star clusters, AGN, and galaxy clusters. The detailed program is attached and can also be found here. Dr. Nancy Evans is organizing the symposium. For more information, contact her at nevans@cfa; or ext 5-7416. Light refreshments will be available. Phillips Auditorium.

SAO HUMAN RESOURCES NOTES

Federal and Trust Open Season Health Fair

Please plan to join us on Thursday, November 6, when SAO will sponsor the 2009 Federal and Trust Open Season Health Fair. Representatives from various Federal and Trust health carriers will be present at CDP in Room 385, from 10 a.m. to 12:30 p.m., to answer any health insurance questions/concerns you may have about benefits available in 2009. Take advantage of free screenings that day! Harvard Pilgrim Health Care (a Trust carrier) will offer all SAO employees free blood pressure screening and/or BMI (body mass index) measurement at the health fair. If you have any questions about this event, please contact Anne LeBlanc at 5-7371 or Linda McDonald at 6-7605.

Federal Leave Donations Needed

Tom Mullen, a federal employee of the Radio and Geoastronomy Division, has been approved as a leave recipient under the Leave Transfer Program. Any federal employee wishing to donate their annual leave to Tom during his medical emergency may do so by completing a leave donor form. Please send your completed form to Linda McDonald at MS 17. Details of the Leave Transfer program can be found here.

Trust Fund Leave Donations Needed

Karen McLaine, a Trust Fund employee of the Financial Management Division, has been approved as a leave recipient under the Leave Transfer Program. Any Trust Fund employee wishing to donate their annual leave to Karen during her medical emergency may do so by completing a leave donor form. Please send your completed form to Linda McDonald at MS 17. Leave Transfer Program details can be accessed here.

Job Vacancies

An online listing of all current SAO job openings is available. For more information, please call Human Resources, ext. 5-7371, or view your nearest bulletin board.

The Calendar is prepared by the Web Services Group. The deadline for entries is 5:00 pm on Thursday of the preceding week. Please use this form to submit entries.