A summer with their head in the stars

In 2015, astrophysicists no longer scan the skies through telescopes. "Much of our day is spent on the computer," says Laetitia. The 21-year-old from Vaud just completed her Bachelors degree and seized the opportunity to do an internship at EPFL's Astrophysics Laboratory – LASTRO – at the Sauverny observatory. However, the data she's looking at comes from the other side of the world: Chile, to be exact, where the Swiss telescope Euler was built in the Atacama desert, at the European Southern Observatory. Observations that are impossible in Europe can be done in the region's crystal-clear skies.

The images will help the two students make progress on their project, which involves gravitational lensing, one of LASTRO's areas of expertise. As Einstein predicted with the theory of relativity, gravity can also affect light as well. If a ray of light comes close to a mass (e.g. a galaxy), the light will be distorted as it would if it went through a lens.

This phenomenon can distort the images of objects hidden behing other celestial bodies. "If you look at a light source hidden behind a galaxy, the light rays that reach us will bend and produce mirage images," says Frédéric Courbin, Senior Scientist at LASTRO. The length of the optical path that each of these mirages follows to Earth differs, and measuring this over time teaches us about the geometry of the universe and how it is expanding." These measures and calculations have been done at LASTRO for the past ten years. "The aim of our project is to reduce the uncertainty of the measurement of the Hubble Constant," says Laetitia. This number is used to describe the rate at which the universe is expanding at a given point in time, which is crucial to understanding the mysterious dark matter discovered in the 2000s (and earned the 2011 Nobel Prize in Physics).

This summer, Laetitia is working together with Eric Paic, a 20-year-old French student about to start the third year of his Bachelor’s degree. Eric takes after his father, who was a physicist. Eric chose EPFL because the training "combines engineering knowledge and a focus on research" and because it introduces astrophysics early on in the curriculum. His dream is to become a researcher, specializing in "stellar physics or cosmology." His internship at Sauverny is also teaching him more about programming and about teamwork in a lab. "This is an opportunity to understand how a research project is conducted over several years," he said.

Laetitia shares his enthusiasm. "I am very grateful for the chance to see what observational cosmology looks like from the inside," she said. After completing her studies, she also dreams of becoming a researcher, with the goal of contributing to the greater good. And who knows, maybe she’ll discover answers to some of the big questions of the universe.

Picture: © Murielle Gerber, EPFL 2015.

Fore more informations, chek out the LASTRO website: http://lastro.epfl.ch/