Astronomers travel around the world. They travel to observe the night sky using big telescopes on remote mountains, to attend conferences or work with collaborators abroad. From the early days of my PhD, I planned to visit our SUNDIAL collaborators at the Instituto de Astrofísica de Canarias (IAC) in La Laguna, Tenerife for a few months. I was extremely excited for this opportunity. A quick search for ‘Tenerife’ in google and you will find out why.

After 2 years, when my trip to Tenerife was finally realised, I found it a bit hard to leave the life that I built in Groningen in the last two years and leave for a few months. I tried to stay motivated, said goodbye to my friends, packed my bag and left the Netherlands. Ten hours later, I was at my Airbnb in La Laguna. 

La Laguna is the oldest and one of the biggest cities in Tenerife. It is located in the North of the Island, far from the touristic cities in the South and close to Santa Cruz, the capital city of Tenerife. Surprisingly, it was full of young students, who study at the University of La Laguna. The city was lively and full of different activities every week. The historical part of La Laguna was actually declared a World Heritage Site by the UNESCO in 1999. It is a nice place for taking a walk, window shopping or enjoying a nice meal.  However, the IAC is located further away from this historic centre. 

Right from the beginning, I enjoyed the experience at the IAC. People were motivated, friendly and sometimes very relaxed! I started to enjoy the warm and sunny days of Tenerife, long coffee and lunch breaks, the sound of the Spanish language at the institute and sharing thoughts with other astronomers.  My plan for this visit was to initiate a new research project, different from what I’m currently involved in at the Kapteyn Astronomical Institute in Groningen. So on my first day at the IAC, after catching up with friends and meeting my collaborators, I started to think of a few ideas. After a week or so, we decided to focus on one topic: The iconic ultra-diffuse galaxy Dragonfly 44. 

As their name suggests, ultra-diffuse galaxies or UDGs are faint galaxies whose stellar material is dispersed or diffused across space. Compared to our Milky Way, UDGs are about ten times fainter than the night sky. Therefore, studying these galaxies allows us to test our current understanding of how galaxies form and evolve in the Universe. In particular, recent studies on a UDG, dubbed ‘DF44’ , in the Coma cluster have reported that although DF44 visually appears to be a dwarf-like galaxy, its dark matter halo is as massive as those of Milky Way-like objects. This result is in tension with currently favoured theories of galaxy formation so investigating this issue is crucial to our understanding about galaxies in astronomy.

The key ingredient that led researchers to conclude that DF44 has a Milky Way-like dark matter halo is the number of stars or globular clusters around the galaxy. The larger the number of clusters, the bigger their dark matter halo. In 2016 and 2017, two different observations showed that DF44 has of the order of one hundred globular clusters in its vicinity, implying that its halo is as large as the Milky Way. But this finding is inconsistent with other observations of DF44 and is what motivated us to re-visit the number of the star clusters around this galaxy.

For the next 2 months, I worked on this project. I was working from early morning until late at night, and most of the weekend. My life was 24/7 about science. My coffee and lunch breaks became shorter and shorter as this research was becoming more and more interesting. My collaborators were very motivated about the work which made my experience more exciting.

I also had the time to visit the observatory at the Teide, the volcano for a day and stayed sometime there to visit the telescope and look at the spectacular night sky of the island. My non-astronomer friends who joined this trip were amazed by the beauty of the night sky, the Milky Way, Jupiter’s red stripes and Saturn’s ring. As a professional astronomer, and after looking at the night sky for many years, sometimes I forget how fascinating astronomy actually is. 

I left the Island at the end of October. I was very happy and scientifically satisfied by what I did at the IAC. Since I came back to Groningen, I feel fresh and motivated, ready to do some more amazing science. 

Acknowledgement: I want to thank Johan Knapen, my SUNDIAL supervisor at the IAC who helped me when I needed immediate medical care during my trip, Micheal Beasley for long conversations not only about our work on DF44, but also sharing our crazy ideas, Reynier Peletier, my supervisor in Groningen for making this trip possible. and Nushkia Chamba for editing the article.

This article has been published on SUNDIAL.