From Astrobites: “Living the ‘Magellan’ life : Observing at a Chilean masterpiece”

Astrobites bloc


Feb 4, 2016
Gourav Khullar

Personal experiences

Magellan 6.5 meter telescopes
Carnegie Institution Magellan 6.5 meter telescopes

You are driving up a mountain. In the middle of nowhere. In a part of the globe that’s too remote to imagine. On a road that could give way anytime. There’s an alpaca chilling by the hills, looking at you with interest. Well, almost.

You’ve seen textbooks of the Atacama Desert as a kid, but never actually believed that people live here, let alone work for science. I welcome you to Las Campanas, a mountain in one of the driest areas of the world – 2500m above sea level – and home to one of the world’s modern wonders, the Magellan Telescopes.

When I was asked of my aspirations growing up, it was becoming obvious that I loved the cosmos. After all, what could be more exciting than studying the galaxies and attempting to understand the physics of the universe! Unfortunately, in India, where I am from, astrophysicists are still thought of as ‘just stargazers’, and not being an ‘encyclopedias of constellations’ means that you are as far from an astronomer as astrology is from real science. What most people don’t realize is that the idea of actual observing at a telescope (that is classically called, well, ‘classical observing’) is almost a dying art in astrophysics, with the advent of modern day telescopes and algorithmic pipelines that let you observe and reduce data while sitting in the comfort of a coffee shop. You submit a queue of astrophysical objects (and hence the name ‘queue-observing’) that you wish to observe, and voila, thy job will be done! Space telescopes like Hubble and Spitzer, and even modern-day ground based observatories like ALMA, work like this. Hence, it is almost ironic that I root for more astronomers on telescopes today. This article shall tell you why.

NASA Hubble Telescope

NASA Spitzer Telescope

ALMA Array

The Magellan telescopes are run by the Carnegie Institution of Washington [more correctly Carnegie Institution for Science] in collaboration with several major universities across the US. At the University of Chicago, I work with the South Pole Telescope collaboration on high-redshift galaxy clusters that were detected by the Sunyaev-Zeldovich effect.

South Pole Telescope
U Chicago/South Pole Telescope

To lock down on how far these clusters exactly are and how massive they are, spectroscopic data and, subsequently, Doppler shifts of spectral lines are needed. This is why I left my cozy office chair in Hyde Park for a 20-hour long journey to another cozy chair in the control room of the Clay 6.5m telescope. This majestic structure houses LDSS3, one of the world’s best spectroscopic and imaging instruments in the optical and near-infrared wavelength bands (read Ian Czekala’s post on the same instrument, but with different science goals!). I was co-observing with Mike McDonald, an assistant professor at MIT and a boss at observing and handling data.

Everything about the Magellan telescopes is classical, and almost poetic. The first sight of the metallic domes bathed in sunlight gets you pumped up for the nights to come. The staff at the lodge is very friendly, and the cooks make sure that you have the best Chilean food that you can possibly get. You meet other astronomers working on other telescopes or instruments, and you see them recognizing each other from previous runs. It is this ‘inner circle’ that I hope to be a part of someday.

We were allotted the nights of 31st January and 1st February, and were rewarded with the best weather we could possibly hope for. With The Beatles playing in the control room and delicious empanadas ready to be devoured, we started the night by calibrating our spectral slits – taking images of the grism, measuring the ambient light in the dome, and measuring the sky background for that night. We planned to use the 4000 Angstrom break (a super cool tracker to measure Doppler shifts in galaxies), which falls in the red part of the electromagnetic spectrum because of the distance of these clusters. Once twilight was past, we attacked the first cluster with 3-hour long exposures – yes, it takes that long for us to get a sizeable signal-to-noise ratio for a cluster that far! By the end of two nights, all five cluster targets were spectrally conquered.

What did I learn from this past week? That it is computationally challenging to detect faint emission lines from a redshift 1.2 galaxy cluster hidden behind the glowing sky background. That it is important to consider all potential sources of error while dealing with data reduction of clusters. But what did I learn that I wouldn’t have sitting in my cozy office chair in Chicago?

That there is something amazingly profound about looking up in the sky and seeing the Milky Way with its stellar population and diffuse gas structures. The Magellanic Clouds give you good company, and the alignment of four planets in the sky (go figure!) adds the right touch to my story – that Mike and I upheld the spirit of astronomy and astrophysics by being there and looking at those clusters with our own eyes, while they were being studied on the grand canvas of the universe.

Large Magellanic Cloud
Large Magellanic Cloud

Small Magellanic Cloud
Small Magellanic Cloud

We utilized our intuition, not an algorithm, to determine how long is good enough to see a cluster, or whether our time was better spent studying another cluster. I believe that part of what makes us astronomers is this very intuition. It is in the same spirit of the field that we should consider what we miss by moving to an automated version of astrophysics.

If and when astronomy moves in that direction, I for one, will miss the empanadas, the alpacas and this great opportunity to take some clicks of my own. It is beautiful up there.

See the full article here .

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