Monday, July 23, 2012

A Week at the LBT

One of the most rewarding aspects of a career in astronomy is the chance to go observing at a professional observatory. I recently spent a week at the Large Binocular Telescope (LBT) in Arizona, observing for the Max Planck Institute. With me were two other observers, Hugh and Mario, members of other research teams at the Institute. In total, we had 6 full nights with which to pursue our various science programs, as well as collect astronomical data for other scientists in our research consortium.

The LBT is a marvel of engineering. It consists of two enormous primary mirrors, each 8 meters (26 ft) in diameter, mounted on the same huge superstructure, a squat but airy truss of red-painted steel, carbon fibre, cabling and glass. The mirrors are built to look up at the same region of sky and the LBT can track an object through its pair of binocular 'eyes' with incredible sub-arcsecond accuracy. The two telescopes will eventually be combined into an Interferometer - an advanced technology instrument that behaves a bit like a single telescope 12 meters in size.

Standing below one of the LBT mirrors.
Click for an album of images from my trip
A large telescope such as the LBT is used at the forefront of astronomical research. Take for example the kinds of science that we were pursuing for those 6 nights. I was using an instrument called LUCI that is sensitive to light in the near-infrared. With LUCI, I obtained spectra of galaxies that are tens of billions of light years away, when stars were forming throughout the Universe at a furious pace. Hugh was using LUCI to precisely measure the apparent sizes of nearby stars, allowing him to look for the presence of disks of dust around them, solar systems in their youth. Intense star-forming regions in our Milky Way galaxy interested Mario: he wanted to train LUCI on some of their most massive stars.

The 2 hour drive from Tucson went up a windy mountain road rising from the desert to the pine and fir crested peak that hosts the Mount Graham International Observatory. In a large trolley, we carried up a week's worth our of groceries up to the Observer's dining area, which sported large windows overlooking the Pinaleño mountains, a row of big refrigerators, a full kitchen, comfy couches and - joy! - a pool table. This, and the attached sleeping cubicles, were to be our home for the duration of our run. We chatted with the last shift of observers, talked about science and telescope issues, settled into our rooms and got accustomed to the thin air at 11,000 ft.

The next day we started our run. Things didn't go according to plan.

In the heady days of tall ships, being caught in the Equatorial becalming zones called the Doldrums came to be a bane of sailors. The word was adopted into modern English to mean times of ennui and lack of activity. Bizarrely, at the LBT, the Doldrums happen when the wind is high, because the telescope dome cannot be opened if it's blowing so hard that the telescope structure could suffer serious stress. We waited and watched unsuccessfully for the telescope to open while howling gale-force winds buffeted the top of Mount Graham. An unusual weather system, which started before we arrived at the peak, kept up a steady barrage of dusty winds for four whole days and nights (taking a night away from the observers before us). As a result, we never actually looked at sky for half of our run, though, if one had stood on the balcony of the telescope dome and look up without being blown off, one would have seen a lovely Milky Way over the horizon and bright stars burning against a velvet black sky. This was a painful reminder of one of the misfortunes of astronomical observing - Weather. Observatories are built in far off and inaccessible places for a reason: those very places, usually deserts or high mountain tops, have the best observing conditions. Time on a big telescope comes at a premium, both monetary and in man hours, so they are designed for a maximum return.

In contrast, the next three nights were fantastic! As the winds died away, the front of calm weather beyond brought superb, twinkle-less skies (heavy twinkling is a sign of turbulent air, something we call "bad seeing") and a thin young moon. With the help of our fantastic Support Astronomer, Olga, who helped deal with a niggle that kept putting the telescope an arcsecond away from where it should have been, I managed to get 7 hours of great data with which we mapped the movement of star-forming regions in twelve galaxies at a redshift of 1.5, seeing them as they were in a 5 billion year old Universe. Hugh, with a twinkle in his eye, showed us the subtle blooming of his stellar spectra that revealed a thin disk of young planetesimals in a star light years away. Mario fussed about excitedly with his spectra, judging quality and applying numerous calibrations. Things proceeded without a hitch and we even had time, while the telescope was kept busy running automated scripts on a long exposure, to play the odd game of pool in the observer's dining room.

For a century, since the rise of large institutional observatories, astronomers have packed their cases - once full of photographic plates, chemicals, and cold weather gear; now with laptops, manuals, and comfortable shoes - and climbed mountains to expand our view of the Universe. Observatories, whether on the ground or up in space, continue to enrich our knowledge and serve as test-beds for cutting edge technology, and we hope that we, as astronomers and as humans, will always be able to find that lone narrow and windy road that takes us up to the stars.

1 comment:

  1. Shout-out to Olga (Kuhn), who was in grad school with me at the CfA!

    During one of my observing runs at the nearby VATT, I had the good fortune of getting an insider's tour of the LBT with Olga. That was back when they only had one of the two mirrors installed.