mainly astrophysics

ALMA, the largest ground-based astronomical project in existence released its first images to the press in October, 2011.

The Atacama Large Millimetre/Submillimetre Array in the Atacama Desert, Chile

The ‘Atacama Large Millimeter/Submillimeter Array’, ALMA for short, is the giant telescope that sits atop the Chajnantor plateau in the Atacama Desert, Chile. It’s not the only telescope to set up for business in the Atacama: it joins a small army of telescopes, arrays and astronomical instruments that decorate the desert’s stargazing hot spots.

The Chilean commute is driven by the particular conditions provided by the Atacama which make it a perfect location for astronomy. For ALMA in particular, a radio instrument, the site needs to be high and dry. The dryness of the desert is important as water in the atmosphere blocks out some of the radiation at the same wave lengths as ALMA processes. It’s certainly high; 5059 metres above sea level gets you halfway to 747 cruising altitude and half the usual amount of air – that means half as much radio-absorbent water vapour to look through. High altitude sites are also ideal for optical telescopes.

Stars twinkle, we know that from the song, but while it may look pretty to a stargazer the twinkling effect is a nightmare for an astronomer. It’s not the star itself that creates this effect, but turbulence in the atmosphere. If you look through less air a star doesn’t flicker as much – you get better quality image. The drive to get above the atmosphere is what sent the Hubble telescope into space and even though a billion dollar budget isn’t available to send every observatory skywards, astronomers always go for the next best thing: stick it on a mountain.

The Chajnantor observatory is one of the highest in the world: it’s 750 metres higher than the observatory on Mauna Kea, Hawaii, although not quite as loftily perched as the Chacaltaya Astrophysical observatory in Bolivia (5230 m) or the University of Tokyo Atacama Observatory, also in the Atacama (5640 m).

An artist’s rendering of the finished Array

Although only part built (completion date is set for 2013) ALMA is now capable of gathering data and it’s already large enough to be rated as the biggest astronomical instrument in the world. Currently only 16 of 64 dishes, 12 metres in diameter have been built. All will be coordinated to look at the same part of the sky and moved around on tracks, ‘zooming’ in and out on astronomical objects. At maximum separation the array will span an enormous 150 km. This configuration will be used when the most distant objects are being observed (the further apart the dishes, the greater the ‘zoom’). When lower magnification is needed, the dishes are reeled in to a more modest 700 metres.

ALMA is not a conventional telescope by any standards: you couldn’t hold it against your eye and peer into the cosmos (not unless you had 64 eyes each a mile or so apart). It’s very different to the archetypal instrument we’re familiar with and the reason for this is ALMA doesn’t see optical light, it sees radio waves. Although the pairing of words ‘Large’ and ‘Millimeter’ in the acronym sounds contradictory, the ‘M’ in ALMA actually refers to the wavelength of light it observes. It won’t be tuning into the local weather report however, the radio waves detected by ALMA come from some of the coldest parts of the universe – minus 200 degrees Celsius and below – and will be studied to reveal new information about distant galaxies, nearby star-forming regions, extra-solar planets (planets in other solar systems like our own) and more.

ALMA’s size combined with the Atacama’s fine-tuned properties conspires to produce astronomical images of unprecedented quality. Sean M. Andrews, a lecturer at Harvard University was one of the lucky few astronomers given the opportunity to use the first round of data. Andrews studies disks of dust and debris around nearby stars and will be using data from ALMA to look for evidence of planets forming from these disks. “ALMA provides access to a new observing window, at a wavelength of 450 microns, which is only possible because of the very low levels of water vapour in the atmosphere thanks to the high altitude and superb observing site,” Andrews said. “Whenever a new wavelength range is opened in astronomy, there are usually many new discoveries.”

The Atacaman landscape has often been compared to a Martian vista; it has even been used as a filming location for Mars based sci-fi movies and TV series. An extra dimension was added to the comparison in 2004 when astrobiologists found almost nothing living in soil samples taken from the desert, not even microbes. What a brilliant notion – that we should travel to the part of earth most like another world in order to stare into outer space.

This article was originally published by Pulsamérica.

I’m a fourth year undergraduate from the University of Southampton, UK, studying for my masters at the Harvard-Smithsonian Centre for Astrophysics. With my summer reading completed, and a new exoplanet waiting to be discovered, I stepped off the plane into Boston Logan Int. this September and eagerly exchanged a drizzly English summer for a beautiful New English Autumn.

So far my education has been heavily exam based with little hands-on research, so this is my opportunity to see what an astronomy career might be like. It is my ambition to write a thesis on the characterisation of an exoplanet – one chosen from the ever-increasing pool of candidates flagged by the Kepler mission. This is a daunting prospect for me: a lowly undergrad with little to no prior research experience suddenly in astronomy heavy-weight territory. Kepler data is highly coveted for a reason – some of the most breathtaking recent discoveries in astronomy have come from Kepler, the spacecraft trailing the Earth in its orbit as it monitors one portion of the sky (just near the constellation Cygnus), continuously looking for the tell-tale blink of a star as a planet passes inarxiv front of it. Any of us brought up on a diet of science fiction has to get excited about ‘Tatooine’, aka Kepler 16b, the circumbinary planet. You may have also heard about Kepler 11 – the multiple planet system, or Kepler 19, a star with one transiting planet and one mysterious ‘invisible’ planet. I can’t think of a more romantic area of astronomy to be involved in right now; where else can you use words like ‘Super-Earths’ and ‘Hot Jupiters‘ every day, outside of a comic book?

It’s the first day of my first year of research; I walk into my office clutching calculator, pen, notebook, mug, and sit down opposite ‘Unity’, my computer. I get straight to work on a Unix tutorial, slowly familiarising myself with the language of Linux and the ‘command line’. After an initial period of struggle wherein I always forget the difference between ‘.’ and ‘..’, and have a near accident with the ‘rm’ command, I quickly pick up the basics.

The results of my first week: a firm grasp of Unix and immaculately polished ‘c’, ‘d’, ‘l’ and ‘s’ keys. (Linux tutorial)

Aims for the future: think of more descriptive filenames (if only I could remember the difference between ‘test_58′ and ‘test_59′).

The next few days see me patiently ‘command-line prompt’, ‘command’, ‘carriage return’ my way through ‘IDL‘, ‘Python‘, ‘Supermongo‘ tutorials. Although I find it satisfying to learn new tools it is a slow process and it stops me racing ahead to publish my first scientific breakthrough. But after a month of ‘cd’ing between directories, running IDL scripts again and again, cajoling Unity into compliance, I sit with her as she finally, reluctantly shows me what I want: spectra. It’s taken us a long time to get here – now it’s time to do science.

I’ve spent the last few weeks juggling with data – strings of numbers reduced and processed and compiled, for looped, while looped, zipped and unzipped until they arrange themselves in meaningful patterns and I’m looking at something that no other human being in history has ever seen.

This is what science is about – the bunch of dots on my screen that hold so much information to the well-trained eye, a few wiggles here and there which make all the difference between breakthrough and null result. I look forward to the day when those dots and wiggles show me my first planet. One day they may even be able to say ‘rocky planet in the habitable zone’ and eventually they’ll say ‘rocky planet in the habitable zone with water in its atmosphere’. Maybe by that time I’ll have finished the online tutorials.

This article was originally published by Astrobites.