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  • Elitsa Ilieva

Mapping Galaxies

An image of the cosmic web (Davis, 2019), or the structure of the universe, where each of the bright spaces contains galaxies.

Space and galaxies may seem distant and filled with uncertainty to the common person, but astronomy is a major field of research with impressive discoveries continuously being made. Professor Anna Sajina is one researcher in this exciting field at Tufts University.

Her work focuses on active galaxies, which is the stage at which galaxies have an active galactic nucleus consuming massive amounts of gas, growing their supermassive black holes, and building up numerous stars. She is also involved in the Prime Focus Spectrograph survey project that Tufts recently joined. This spectrograph is a big instrument that would be “the first of an upcoming new generation that allows you to take spectra of thousands of galaxies in one go.” This spectra is a graph that shows the intensity of light being emitted over a range of energies, which is useful because light is the main way to evaluate the properties of galaxies. Specifically, having this spectra available allows for the distance between the Earth and these galaxies to be measured. By looking at things at different distances, you are essentially looking at things at different epochs. This is because, Professor Sajina explains,

“The light of a galaxy that is further away from us will take longer to reach us than something that’s close to us, which means that the light we received from a galaxy that’s further away from us, actually left that galaxy further back in time. Therefore, if you look at things at different distances, it’s like looking back in time.”

Therefore, the spectra provided by the spectrograph allow us to explore how galaxies have changed from the past till today. This is because we are not able to observe how a particular galaxy is changing, so we must see how populations of galaxies evolve with time, and spectrographs allow this.

This new instrument that Professor Sajina is going to be working with is truly revolutionary because it takes over 2000 spectra in one go, while previously it was only possible to get spectra of one galaxy or very few at a time. However, with the new spectrograph, “if you have more precise positions, for every galaxy you can get more precise measures of its intrinsic property, but you can also better build a picture of the 3-D distribution of galaxies in space.” This is why Professor Sajina is so excited by the Prime Focus Spectrograph project.

Professor Sajina believes that astronomy is a “great ambassador for the STEM fields,” as “even people who are not scientists tend to be interested in astronomy.” Though the field was not initially on her radar as an undergraduate, after taking a course her sophomore year at the University of British Columbia in Canada on astronomy, she was fascinated by it. She found a summer internship a year later and realized that she enjoyed the research aspect of the field as well, and went onto graduate school, earning a PhD and then a Postdoc at Caltech.

She noted the importance of getting involved in research as an undergrad in determining her path following undergraduate school and advises that students “find opportunities to get involved in research as an undergrad to actually see what that’s like, because it’s different from just the classroom experience.” She also commented that a career in research requires curiosity and drive that is different from what a student in a classroom setting requires. She explains this difference: “Researchers are different [than students] because nobody knows the answer ahead of time, so you have to have that curiosity, drive and persistence, because sometimes it’s quick, and sometimes it takes a long time... being a good student is not actually the same [as being a good researcher], and even the converse can be true...Those are slightly different skill sets.”

In a field that requires so much patience and observation rather than active experimentation with variables and controls that can be done in a lab, this curiosity and skill specific to researchers is what allows the research to always be moving forward onto bigger things and more amazing discoveries. In the vast space that are galaxies, there is only more information to be found—all that is needed is people to discover it.


Davis, Matt. “What Is the Cosmic Web?” Big Think, Big Think, 12 Sept. 2019,

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