Adventures in Ground-based Astronomy: An Inside View (Part I)
Soon I will be leaving the Earth-based realities of the Nature Research Center to observe massive forming stars beyond the Solar System, part of my research in exploring the chemistry of forming solar systems — environments much like our own Solar System was about 4.6 billion years ago.
An example of a stellar nursery is the Orion Nebula, a small fuzzy patch within the “sword” of the Orion constellation, but to astronomers a brilliant region of star and solar system formation. Some of the forming stars in my study come from within this nebula.
To observe these exciting solar system nurseries, I and a collaborating student from the California Institute of Technology, (my home institution prior the Nature Research Center) will be venturing off to the Keck Observatory in Waimea on the main island of Hawaii. There, we will observe from Keck Headquarters a few miles from the summit of Mauna Kea, where an astronomer will be moving the telescope based on our list of target stars and commands from our base in the Keck control room. Observing on one of the Keck telescopes is a competitive process, and it is a privilege to be selected for even 1/2 night of observing; my proposal was awarded 1 night, which is sufficient to obtain new data on early solar system chemical processes!
The Keck Observatory is comprised of twin telescopes which stand together on the summit of Mauna Kea, home to 13 working telescopes (see my earlier post, “The Many Faces of Mauna Kea“, which describes the mountain in more detail). The first Keck telescope (“Keck I”) began science observations in 1993; Keck II was initiated in 1996. Each of the Keck telescopes has a light-gathering mirror of 10 meters (~4oo inches), making them the largest optical and infrared telescopes in the world, each capable of bringing into view objects more than 10 billion light years from Earth!
A marvel in design: The Keck telescopes each stand nearly 90 feet high and weighs 300 tons. Each of the 10-meter mirrors function as single, giant parabolic glass services, yet have an ingenious and unique design. Because extremely large pieces of glass are both enormously expensive and are prone to collapse under their own weight, each Keck mirror is comprised of a mosaic of 36 hexagonal segments arranged in a honeycomb configuration. A single segment is 1.8 meters wide, 7.5 cm thick, and weighs roughly 1/2 ton. A complex computer alignment system perfectly aligns the mirror segments twice per second to an accuracy of 4 nanometers (4 billionths of a meter, or 1,000 times thinner than a human hair)!
Keck face-to-face: Following an observing run a few years ago, I had the fortune of a fascinating tour of the inner workings of the telescope atop Mauna Kea. The following photos show some of the very cool and seldom seen features that keep observational astronomy on the cutting-edge:
There are always mirror parts polished and ready to replace problematic segments on the Keck mirror. These are stored in a holding area within the Keck domes. On this visit I learned that it is the field of astronomy that has mastered the art of mirror polishing!
There are several instruments on each of the Keck telescopes that are used by astronomers interested in various parts of the sky, such as asteroids, comets, forming stars outside our solar system, and the center of our Galaxy. The instrument I use for observing gas in forming solar systems is the Near Infrared high-resolution Spectrograph (abbreviated NIRSPEC).
My current target is the molecule carbon monoxide (CO) and it’s variations known to exist in the gas surrounding forming stars. NIRSPEC is an extremely powerful tool for such observations due to both its high spectral resolution and the fact that it is at Keck, a telescope that is large enough to collect light from distant, and thereby very faint, objects.
I was particularly excited to finally meet NIRSPEC in person, after driving it all the previous night! I don’t think it minded my getting this photo taken while it was blanketed and resting:
NIRSPEC is a cryogenic instrument, meaning that it operates under very cold conditions in a vacuum. It’s operating temperature is 60 K (Kelvins), corresponding to over -350 degrees F! Cryogenics are used in astronomy to help reduce “noise”, or interference in the signal from the astronomical target, which can result from extra heat produced during observations.
Keeping NIRSPEC at such a cold temperature is no easy task; after repairs or maintenance, it can take almost 2 weeks to reestablish the working temperature of 60 K and the vacuum system to a functioning level!
While the visiting observing astronomers operate the instrument (such as NIRSPEC) from Keck Headquarters, there is a support astronomer working the telescope, helping to find the targets supplied by the scientists, and watching for wet or icy weather which could damage the sensitive mirror. This support astronomer is responsible for closing the dome in cases of bad weather. Support astronomers are critically important to the success of observing runs, and to the proper maintenance of this state-of-the-art observatory.
This is a somewhat blurred view of the summit observing station:
Part II of this adventure takes place at observing mission control, at Keck Observatory Headquarters, down the mountain….