Georgina Dransfield has just returned from months at the South Pole, working to expand our understanding of exoplanets – and dreaming of a pair of jeans

There’s genuinely not a lot I’d change if I could do my mission to Antarctica again. The science I went there to do went as well as I hoped it would and I made it back without losing any body parts to frostbite. The only real regret I have is that I didn’t pack a pair of jeans; somehow this most inane of oversights managed to cause me a not-insignificant amount of frustration that only grew as the weeks ticked on by.

I began my jeans-less journey in Great Malvern, Worcestershire on 17 November 2021. Four trains, five planes, two quarantines and 31 days later I arrived at Concordia Station on Dome C in Antarctica, where I would be working for the next seven weeks as part of the Antarctic Search for Transiting Exoplanets (aka ASTEP) telescope summer team.

Goodbye to sunsets

The group I travelled with, mostly glaciologists and seismologists, were all itching to get to Concordia to begin data collection, and they were understandably curious as to why astronomers were headed there during the months of neverending daylight. It’s a fair point. Antarctica is a brilliant astronomical site because of the long nights and dry air, but we only get to observe for half the year. So, why bother going in the summer when it never gets dark? Simple: for ASTEP, our annual summer campaigns represent our only opportunity to access the telescope for maintenance and upgrades.

As I climbed out of the propeller plane outside Concordia, I realised that all cold I’d experienced leading up to this point was just pretend cold. This was real, proper, freeze-the-insides-of-your-nose-ina-millisecond cold. I really wanted to take photos, but I also wanted skin, so I prioritised the latter and ran inside, where I was greeted by my colleagues. Two of our team, Karim and Djamel, had already been there for a couple of weeks dismantling the telescope to move it to its new dome. My arrival with the fourth member of the gang, Olivier, completed the group so we could start work in earnest.

Unlike me, my colleagues were there to do some high-level work with the telescope itself. Karim, Djamel and Olivier were jointly responsible for two of the three missions that made up our summer campaign: installation of a new two-colour camera box and relocation of the telescope to a bigger, better dome. The new dome can be opened and closed remotely from Europe, meaning that we would no longer have to leave the telescope open all season. Or worse, send the winterover astronomer out to close the dome manually when the weather inevitably deteriorates.

• 

• 

• 

Lights, camera, action

The two-colour camera box is also a significant upgrade for ASTEP. In simple terms, it contains two cameras: one detects mostly blue light, while the other is sensitive in the red. To understand why this will allow us to do more and better science, we need to first consider what ASTEP is designed to do.

ASTEP is a 40cm telescope dedicated to the search for planets outside the Solar System. While there are several ways to find new worlds, we use the approach that’s led to over 75 per cent of confirmed exoplanets: the transit method. A transit is an astronomical event where a planet passes in front of its parent star causing a characteristic dip in brightness as it temporarily obscures a tiny portion of the stellar disc. We know if we’ve observed a transit by plotting a graph of stellar brightness over time for the target star, called a light curve. If we see a V- or U-shaped dip in the light curve, then we might be onto something.

So here comes the fun bit: the depth of this dip tells us something about the size of the planet relative to the host star’s size. If it’s a planet. That there ‘if’ is the bane of planet hunters’ lives. Instead of a planet, the dip in the light curve could be caused by an astrophysical false positive like, say, an eclipsing binary. Those pesky double stars have light curves that mimic transit light curves, causing many a broken heart in the world of exoplanet science.

Fortunately for us, we have a weapon in our fight against these lookalikes. In an exoplanet’s transit light curve the depth should be the same when observed in different colours, while the curve from a binary eclipse could vary significantly with wavelength. This means that by observing simultaneously in two colours, we can detect a transit and rule out the most common false-positive scenario.

The work my colleagues did required them to put on their full polar gear and walk the 500m from the base to the telescope and its nearby astro-shelter every day. Repeatedly. I could do that, and I certainly did do that for the first few days. But, you see, I didn’t want to. Having to spend 15 minutes putting on a ton of layers and then trudging half a kilometre in the world’s softest, driest, most powdery snow while wearing boots that, while very warm, weighed a couple of kilograms each… that novelty wore off rapidly. Also, I didn’t have to do it because my job, mission number three, was the installation of our new automatic data analysis pipeline and for that I just needed to be on the same network as the telescope computer, which I could achieve on the main base.

I realise it might be hard for some readers to really get excited about a quest to the ends of the Earth to install software on a computer, but let me tell you now that the pipeline is a thing of beauty.

ASTEP’s two cameras photograph the chunk of sky we tell it to look at and the CCDs have several million pixels each. These pixels get exposed for however long we decide, then the image is saved and we begin another one. This continues for the duration of the observation, which can be anything from a few hours to a handful of days. The job of my pipeline is to get us from these digital photos of the sky, often thousands of them containing many hundreds of stars, to the light curve of just one star. But not just any star, it must be the correct star.

Below-zero bandwidth bothers

So the pipeline has to process the full set of images produced each night. From image calibration and star detection, to correct target identification and light-curve plotting, the pipeline is responsible for getting us the data products we need to discover and characterise new planets. Throughout our winter observing season, the pipeline must run automatically on-site, with just the results emailed to us daily.

This is because we can’t get our hands on the raw images until one of us goes there the following year and copies them onto a hard drive. It’s just one of the many limitations of working in such an extreme environment: the internet is terrible, so we don’t have the bandwidth to download our raw data as it’s taken.

I’d spent the weeks and months prior to the trip developing the pipeline and practicing installation on various UNIX architectures, so that bit went smoothly and was completed within the first three days. I then spent the rest of my time at Concordia testing and from climbing a single flight of stairs. The puzzling lack of Nicolas Cage movies. It’s all hard and a bit alien, but it’s made easier by having some familiar things. I did consider this ahead of time – Ihad a pack of Jammie Dodgers and my 30-year-old teddy bear, but not one single pair of jeans.

Georgina and the jeans she borrowed from an IT technician on the base (left). Having arrived at the station not knowing anyone, she made some friends for life during her time at the South Pole (right)

You see, the reason I didn’t pack jeans was because I figured they wouldn’t be practical or comfortable under my polar suit. As it happened, I wore it seldom, and instead sat around in glorified pyjamas most of the time. One of the hardest things about working in Concordia is how far removed everything is from normal life. Yes, I’m referring to the cold, but also living in such close quarters with a very small group of strangers. And the constant daylight messing with your sleep patterns. And having such limited contact with loved ones back home. Getting out of breath What really alleviated some of the hardships of being there for so long were the people I bonded with. When I’d arrived on 18 December, everyone at Concordia was a stranger to me. By Christmas I’d made friends and by New Year’s Eve some of those friends felt like family. A couple of weeks into the new year, the IT technician very kindly loaned me a pair of jeans because I wouldn’t stop berating myself for neglecting to pack some. So maybe, on reflection, it was a good thing since it gave us all something to laugh about: me in a Sicilian chap’s tiny jeans. But next time, if there is a next time, I know what will be at the very top of my packing list.

The restaurant at the end of the world

Finding a decent meal at the South Pole isn’t easy, especially when you’re a vegan

We all know the joke about how you know someone’s vegan because they tell you, but the vegan food on base was genuinely comical. I did worry how a French-Italian station would handle feeding me, and while there were a few rather delicious hits, the misses were considerably more spectacular, the most astounding being my Christmas dinner: sliced orange, mountains of eggless mayonnaise, capers, green beans, diced tomatoes and… chips. But I did Britain proud (I think) by introducing the base to chip butties. I’m sorry to report they were met mostly with disgust. Not one to be put off by widespread disapproval, I made ‘some form of potato sandwich’ my default meal after a while. I was often saddened by the lack of vegan desserts, so I took matters into my own hands and made a couple of cakes. I also realised that I had everything necessary to make vegan pancakes, so midnight pancakes became a thing. Strictly speaking, I wasn’t supposed to be in the kitchen at all, but as is so often the case, it pays to make friends with the chefs.

• 

• 

• 

How do we know where to look?

The telescope’s location gives it a unique view of the night sky

ASTEP was originally conceived as a survey in its own right, intended as a ground-based successor to the French satellite CoRoT (Convection, Rotation and planetary Transits), but nowadays our time is mostly dedicated to TESS follow-up. TESS is the Transiting Exoplanet Survey Satellite, a space telescope searching the sky for exoplanet candidates. Unlike Kepler, which stared continuously at the same patch of sky, TESS covers the whole sky in 26 sections. Its observations are sent to the ground where they’re made into light curves to identify potential candidates. So where does ASTEP come into this? Well, TESS can’t distinguish between true planets and false positives, so a global network of observatories on the ground reobserves TESS’s candidates and either validates them or rules them out. ASTEP’s unique location close to the Pole allows us to go after a specific subset of TESS’s discoveries, which are largely inaccessible to everyone else: long, infrequent transits, as the polar region has the largest amount of overlap between the individual sections of TESS’s coverage and is observed the longest. With the average night on Earth lasting about 10 hours, and our longest going on for a couple of months, those super-long events really are best left to us.

Georgina Dransfield is an Anglo-Uruguayan teacher-turnedastro-PhD student at the University of Birmingham debugging. A task that was huge, tedious and could have been comfortably done in jeans.

Photos: ESA/IPEV/PNRA–E. KAIMAKAMIS, ESA/IPEV/PNRA-M. BUTTU, NASA, MARK GARLICK/ISTOCK/GETTY IMAGES, GEORGINA DRANSFIELD