Astronomical Scintillations

My first trip from grad school had been to the University of California at Santa Cruz for the Adaptive Optics Summer School held by the Center for Adaptive Optics (CFAO). I was very excited and the visit did not disappoint. We had learnt lots of adaptive optics and met a lot of people doing great work in the area.

Lick Observatory on Mount Hamilton. Picture from Wikipedia

And the best part of the trip had to be the trip they organized to the Lick Observatory at Mount Hamilton. The winding roads and breathtaking views led to domes that housed the most amazing optics and astronomy. Elinor Gates, a scientist at the observatory, was the most knowledgeable host we could have hoped for! She showed us around their adaptive optics setup, their telescopes, and narrated some very engaging ghost stories whilst setting up a smaller telescope on the night sky! It was an absolutely starry and spectacular night!

So some weeks ago, when the N-Cal OSA committee here asked for local speakers, I immediately thought of Elinor! Would be good to catch up with her and see what’s new at the Lick Observatory! Elinor kindly agreed to give us a talk on “Untwinkling the Stars.”

Elinor Gates chatting with folks after the talk

The Lick Observatory is an astronomical observatory on the summit of Mount Hamilton, east of San Jose, founded in 1888 by the bequest of James Lick. They have several telescopes like the 3m Shane Reflector which has adaptive optics on it, the 1m Nickel Reflector and a couple of smaller telescopes and accessory equipment.

Heat, wind and such turbulence in the Earth’s atmosphere, which cause scintillation or twinkling of stars, also create distortions and aberrations when these stars and planets are imaged by ground based telescopes. It is too expensive to put all our telescopes in space (like the Hubble Space Telescope) where they will experience no aberrations from atmospheric turbulence. So Lick Observatory has incorporated an adaptive optics system into some of their telescopes. Adaptive Optics can be used to detect these aberrations with a wavefront sensor and correct them using a deformable mirror.

You can use a natural star in the field of view of your object of interest as a reference “point source”, and use the deformation of that star as an indicator of the aberrations. But it’s often hard to find a nice guide star naturally in the field of view for every interesting object in the sky. So at Lick Observatory they have a laser guide star. They shine a laser beam up into the night sky. A layer of sodium ions at about 60 miles in the mesosphere absorbs and emits light, which can be seen by the telescope like a reference point source in the sky. They can then use the deformation of this laser guide star for wavefront sensing and correction. Elinor told us stories of how they station people outside to watch-out for the safety of airplanes and pilots when they turn their laser guide star on for wavefront sensing.

At Lick Observatory they have been using their telescopes with adaptive optics and both natural and laser guide stars for many years now. The technology is also used on select other telescopes in the world. Elinor and many other astronomers use the telescopes for finding and observing many important astronomical bodies. She showed us some cool images of Asteriods, Moons, Galaxies, Black Holes, Quasars, Stars whose names sound like math-formulae… wow! It’s great to see what can be achieved using cutting-edge technology, visionary scientific goals and well invested bequests!

Elinor’s talk was very well received. It is always good to see the stellar work being done by women in optics. It's even better to see the work being appreciated by the optics community. If you are working in Optics and will be in the Bay area on Tuesday 10/18, OSA is hosting a Minorities and Women in OSA event at 4-5.30pm at the Sainte Claire Hotel in San Jose. They will have some highly accomplished ladies working in optics - Jannick Rolland from the University of Rochester, Donna Strickland from the University of Waterloo, Laura Weller-Brophy of FluoroLogic, Inc., and Elizabeth Rogan who is the CEO of the Optical Society. It promises to be an interesting event and everybody is invited! You are welcome to register at this link (no charge). 

Our sincere thanks to Elinor for making the long and winding drive from Mount Hamilton to meet us for the N-Cal OSA meeting. Folks, if you are in town, you might want to think of visiting the Lick Observatory which is open to public during the day! 

Thanks for stopping by! Cheerio!