Mississauga Astronomical Society

Thirtyfourth Meeting

Speaker’s’ Night

Day:                Friday, February 11, 2005

Speakers:   Paul Mortfield  - guest speaker

                   Guy Nason

The Sun

Paul Mortfield, a York University alumnus is an astronomer involved with solar spectrography, education, and public outreach at Stanford University in California. He does webcasts for NASA-TV for children, broadcasts for Sun-Earth Day and is very involved with teacher–student education. At night he does astrophotography as a hobby.   

The general public is very interested in the Sun for as shown by the recent National Geographic Magazine article about the Sun and T.V. star Malcolm in the Middle’s song about the nature and importance of the Sun.

We are currently in the downswing of the 11 year sunspot cycle, the peak having been reached in 2002. Paul showed images of the quiet Sun as seen today at extreme UV wavelengths and with various instruments on the SOHO satellite including continuum, magnetogram and various spectral lines. Each wavelength shows its unique features on the solar surface. The various images were combined into a dynamic movie showing an entire rotation. Paul also showed SOHO images with comets near the Sun’s surface. To date over 880 comets have been discovered on SOHO images by amateurs. The SOHO spacecraft was lost due to human error in 1998 but re-aquired using the Arecibo radio telescope to characterize its spin. Eventually the solar panels received solar power and controllers were able to regain control. Despite triple redundancy in gyroscopes, all off them have ceased functioning and the spacecraft is now using a small telescope for guiding

Sunspots at 3700 degrees C. appear dark only because they are on the hotter solar surface. New techniques allow studies of gas flow below the surface while magnetograms demonstrate fields. In this way, plasma flows can be observed along magnetic field lines. In H-alpha imaging, solar prominences are easily seen. A movie of the chromosphere in H-alpha was shown. Solar flares are classified as A, B, C then M and X in order of intensity. Paul showed examples of two large flares with  the largest ever recorded in history being an X45 flare on Nov. 4, 2003. This flare saturated the detector on SOHO for a full 11 minutes.  

The entire Sun vibrates in a complex way that can be visualized with SOHO instruments. When the frequency of vibration is increased by 42,000 times, the signal is audible. Paul showed images of the solar corona demonstrating the difference between the quiet Sun and active Sun, and images of coronal mass ejections where a billion tons of hot gas is ejected. This impacts directly on space weather affecting the Moon, planets and near-Earth environment, satellites (the X45 flare knocked out the Uzomi spacecraft to Mars) and astronauts. If, for example, a large flare had erupted at the time of the manned lunar landings, the astronauts would have received a lifetime dose of radiation.  Paul showed a movie of the Earth’s magnetosphere and the changing aurora.

Future solar missions include STEREO in 2006 which should study the Sun from two different angles, SOLAR-B in 2006 a successor to Yokho, and SDO (solar dynamics observatory) in 2008.

Asteroid Occultation

Guy Nason from the Toronto Centre summarized the asteroid occultation of Portlandia in December 2004. He then asked the members to observe the occultation of a 10.3 mag star in Leo near Regulus by the asteroid 112 Iphigonia on Feb. 24. The path very favourably passes through the GTA including Mississauga. There is value in observing from the edge due to uncertainty in the path.

 Submitted by Chris Malicki, Secretary  Chris Malicki, Secretary                               back to M.A.S. meeting reports page
Mississauga Astronomical Society