APRIL 23 - 27, 2007

The Calendar is prepared by the Web Services Group. The deadline for entries is 5:00 pm on Thursday of the preceding week. Entries may be submitted through interoffice mail (MS 77), by FAX at 617-384-7233, or via email to weekly_cal@cfa.

SATURDAY, APRIL 21

Sci-Fi Movie Night: "Star Trek IV: The Voyage Home" drew more new viewers to the series than ever before with its message of caution and hope. A gigantic space probe has parked in Earth orbit, sending out incomprehensible signals that are wreaking havoc with the planet's oceans and atmosphere. When they decode the signals, Kirk and company realize that they must time travel back to the 20th century in hopes of bringing back the creatures the probe is trying to contact. We won't spoil it for you here, other than to say perhaps humans aren't the only intelligent species on the planet. Letıs hope that the message of conservation and stewardship in this film catches on around the world before it's too late.

7:00 pm: "Flash Gordon" episode―Thrilling adventures on the edge of space!

7:15 pm: "Star Trek IV: The Voyage Home" (PG)―The key to saving the future, can be found only in the past.

Sci-Fi Movie Nights are held in the Phillips Auditorium. Doors open at 6:30 pm. No reservations are necessary; however, seating is to the capacity of the auditorium.

MONDAY, APRIL 23

12 noon: Solar, Stellar, and Planetary Sciences Division Seminar. "Supergranule Scale Convection Simulations," Dr. Robert Stein, Michigan State University. Pratt Conference Room.

Abstract: Realistic surface convection simulations have led to several insights into the structure of stars. The mean structure of stellar envelopes is different from that inferred from one-dimensional models. The atmospheres of cool stars has much larger temperature fluctuations than observed. Convection is very asymmetric due to stratification. It is driven primarily by cooling at the surface rather than heating from below. The bottom of the surface convection zone is actually stably stratified. The velocity has a power law spectrum with only granulation as a distinct scale and a slight enhancement at supergranule scales. The horizontal size of the convective cells increases steadily with depth as the scale height increases. They have also revealed several problems. Abundance determinations based on such models are in conflict with helioseismic observations. The nature of supergranulation and the role of magnetic fields in its distinctive appearance is still unclear. The existence or not of surface dynamo action is in dispute.

TUESDAY, APRIL 24

12:30 pm: Institute for Theory and Computation (ITC) Seminar. "What is the Origin of Cosmic Magnetic Fields?" Dr. Russell Kulsrud, Princeton University. Pratt Conference Room.

WEDNESDAY, APRIL 25

12:30 pm: High Energy Astrophysics Division Lunch Talk. Speaker: Dr. Arielle Phillips, Amherst College. Topic: To be announced. Phillips Auditorium.

THURSDAY, APRIL 26

11:00 am: Science Education Seminar and Open Discussion. Weekly sessions focus on current department programs, literature reviews, and recent trends in science education and assessment. Some sessions feature outside speakers or guests. All members of the CfA community are welcome. Please contact Bruce Ward at bward@cfa, if you wish to attend any session. Phillips Auditorium.

4:00 pm: Colloquium. Bok Prize Lecture: "Discoveries of Hypervelocity Stars and What They Tell Us About the Galactic Center," Dr. Warren Brown, CfA. Preceded by tea at 3:30 pm. Phillips Auditorium.

Abstract: Hypervelocity stars leaving the Galaxy at ~1000 km/s are a natural consequence of a massive black hole in a dense stellar environment. In 2005 we discovered the first such hypervelocity star (HVS): a 3 solar mass B star, similar to stars seen in the Galactic Center, but 110 kpc distant and moving away at over 700 km/s. Our follow-up survey has resulted in seven further HVS discoveries plus evidence for a class of HVSs on bound trajectories. We discuss how the observed anisotropic spatial distribution of HVSs is linked to their ejection mechanism. HVSs place quantitative constraints on the types of stars in the Galactic Center, and the history of stellar interactions with the central black hole.

FRIDAY, APRIL 27

12:30 pm: Radio and Geoastronomy Division Lunch Talk. "Investigating Magnetic Field-Circumstellar Disk Interaction in T Tauri Stars of the Orion Nebula Cluster," Dr. Alicia Aarnio, Vanderbilt University. Room M-340, 160 Concord Avenue.

Abstract: The Orion Nebula Cluster is an active site of star formation which provides observers with a glimpse into the earliest stages of stellar evolution. The cluster is home to thousands of objects a few million years of age or younger; for a subset of these young stars, energetic X-ray activity has been observed using the Chandra X-ray Observatory. Using a uniform cooling loop model effective in modeling solar magnetic field loops, Favata et al. (2005) derive loop arc lengths of tens of stellar radii or larger in some cases. In this work, we present Monte Carlo models of the spectral energy distributions of the stars with the largest flaring loops. We consider the implications of the flare loop lengths with respect to the truncation radii obtained from the best fit models and discuss the derived loop lengths in the context of stellar angular momentum loss theories.

12:30 pm: Institute for Theory and Computation (ITC) Seminar. "Lyman-alpha Emission from the Intergalactic Medium," Juna Kollmeier, Ohio State/OCIW. Pratt Conference Room.

Abstract: The intergalactic medium (IGM) is a key probe of both cosmology and galaxy formation. Most of our knowledge of the IGM, comes from absorption line measurements---1-dimensional skewers along the way toward bright background sources. In the era of hydrodynamic cosmological simulations, this information represents just a small fraction of the full 3-dimensional information encoded in current theoretical models for the properties of the IGM. In the era of large telescopes, it also represents only a fraction of the information that is observationally accessible. It is now possible to make predictions for the Lyman alpha emission from the IGM, that provide spatial and kinematic information about the IGM. I will discuss the theoretical advances that have made this possible and compare to current observations, as well as highlight future possibilities for understanding the distribution of neutral gas at high redshift and the physical processes that result in Lyman alpha emission.

7:00 pm: Sci-Fi Movie Night. The Star Trek series has attracted more than its share of parodies and send-ups. Star Trek could be lofty and thought provoking, but it could also be schlocky and over-the-top. In perhaps the best Star Trek parody ever created, "Galaxy Quest" presents the embittered cast of a now-cancelled sci-fi show who discover that their program broadcasts have reached an alien civilization. Now, those aliens have recruited the Galaxy Quest crew to help them win their interstellar battle against the evil General Sarris. The fate of the galaxy is in the hands of second-rate actors - we're all doomed!

7:00 pm: "Hardware Wars"—May the Farce be with you!

7:15 pm: "Star Trek IV: The Voyage Home" (PG)―The key to saving the future, can be found only in the past.

Sci-Fi Movie Nights are held in the Phillips Auditorium. Doors open at 6:30 pm. No reservations are necessary; however, seating is to the capacity of the auditorium.

SAO HUMAN RESOURCES NOTES

Leave Donations Requested

Two SAO Trust Fund employees have been approved to receive leave donations. Due to medical emergencies, Nathalie Martimbeau of the Optical and Infrared Division and Donna Coletti of the Library have been approved as leave donor recipients in the Leave Transfer Program. Any SAO Trust Fund employee who wishes to donate annual leave to Nathalie or Donna should complete a Leave Donor Form and send it to MS17.

Under the Leave Transfer Program, Trust Fund employees may only donate annual leave to other Trust Fund employees and Federal employees may donate annual leave only to other Federal employees. If you should have any questions or are not able to access the form, please contact Anne LeBlanc, ext. 5-7371.

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.

VISITING SCIENTISTS

A list of scientists currently visiting the CfA is available here.