The Frozen Dome

Normally, if I heard or read the words 'Dome C' I would think they referred to the third dome in a cluster of structures at some observatory. Recently, I've come to learn that Dome C is also the name for one of the coldest places on earth, one of several summits on the Antarctic Ice Shelf.

Ironically, there is still an astronomical link. Dome C is considered to be one of the best potential sites for a new observatory on the face of our planet. For one thing, the Sun never gets higher than 38 degrees above the horizon, so there is a lot of night time for observing from the south polar region. Even better, there is almost no infrared sky glow, the air is extremely dry, there is almost no aerosol or dust, and no light pollution. The Antarctic Plateau is the largest desert on Earth, so there is very little precipitation and a very high percentage of cloud-free time. Surprisingly, the wind is also quite mild at Dome C, averaging a mere 6 mph in winter. That is a good thing, considering the average annual temperature is -55C, with lows of -80C and balmy highs in the -25C range. Who needs wind chill when it's that cold?

Most importantly, the seeing is typically 2.5 times better at Dome C than at the best existing observatories. Star images taken through a telescope at Dome C would be 2.5 times sharper and 6 times brighter.

The image on the left is a simulation of a star field as observed from the best existing observatory sites; the image in the middle is the same star field as observed from Dome C. To see as many stars from a mid-latitude observatory, you would need to build a telescope 2.5 times bigger, which would cost ten times as much, and would give the image on the right, which makes the stars look brighter but doesn't improve the sharpness of the image.

Image and text from 'Exceptional astronomical seeing conditions above Dome C in Antarctica', by
by Jon S. Lawrence, Michael C. B. Ashley, Andrei Tokovinin, and Tony Travouillon, published in Nature, 16 September 2004.

Three interesting papers have been released to the pre-print server describing the PILOT program (the Pathfinder for an International Large Optical Telescope), a proposed observatory on Dome C in Antarctica. The first paper presents an overview of the instrumentation suite and its expected performance, a summary of the key science goals and a discussion of the future of Antarctic astronomy.

Paper 2 describes a series of projects dealing with the distant Universe. One potential project that caught my eye is the search for pair-instability supernovae (PISNe) and gamma-ray burst afterglows. These could be our best glimpses into stars formed in the very early days of the Universe. PISNe are predicted to be the product of super massive stars formed in the early history of the Universe. These stars were formed before there were any heavier elements, so their unique chemical composition and masses resulted in a different kind of final disruption of the supernovae progenitors in this era. The light curves of these PISNe are predicted to be have slower rise times and to stay bright for much longer than SN closer to home. This is pretty cutting edge astrophysics, seeing as how no PISN has ever been found.

PILOT could also examine some of the first evolved galaxies and galaxy clusters to inform us of the processes in the evolution of structure in the Universe. They also propose a large-area weak-lensing survey and a program to obtain supernovae infrared light-curves to examine the nature and evolution of dark energy and dark matter.

The ability to do infra-red astronomy from the planet's surface makes PILOT a good match and essentially the only competition for the James Webb Space Telescope in the coming decade.

Paper 3 presents a series of projects dealing with the nearby Universe. Several projects are proposed that examine stellar populations in nearby galaxies and stellar clusters, to gain insight into the formation and evolution of younger galaxies and stars.

Other projects will investigate the formation processes of stellar and planetary systems. Three projects in the field of exoplanet science are proposed. These include a search for free-floating low-mass planets and dwarfs, a program of follow-up observations of gravitational microlensing events, and a study of infrared light-curves for previously discovered exoplanets.

Free-floating low-mass planets; now there is a category of interesting objects. The plan is to examine nearby star clusters to search for planets not associated with stars down to several Jupiter masses. Why would astronomers be so interested in free floating planets? Because typically, exoplanets light is difficult or impossible to disentangle from the light of their accompanying star. If we can find exoplanets free of the overpowering glare of their host stars we can study the chemical composition and atmospheric properties of these planets.

And finally a study of coronal mass ejections from the Sun, and a monitoring program searching for small-scale Low Earth Orbit satellite debris items are also proposed.

The opportunities to do exciting, results-oriented science exploration and discovery from Antarctica is is almost as mind-numbing as the night time temperatures resident astronomers and technicians will have to bear to perform the work.

Constructing, operating and maintaining a telescope at the bottom of the world under these conditions will be another great story. Now that I know about Dome C and PILOT, I'll keep an ear to the ground and let you know when there are new developments.

No comments: