The Keck Observatory on Mauna Kea in Hawaii is
one of the telescopes used by Lisa Kewley in her
study.

Astronomer Lisa Kewley laid the foundations of her galactic inquiry during PhD research at the Research School of Astronomy and Astrophysics on Mt Stromlo. Since then, she’s journeyed to the University of Hawaii to use some of the largest telescopes in the world. For her work studying the formation of the Milky Way, Dr Kewley was awarded the 2006 Annie Jump Cannon Award by the American Astronomical Society. Each year, this prize honours an outstanding woman who has made a major contribution to the field of astronomy early in her research career.

Reporter: When did you become interested in astronomy?

Dr Lisa Kewley: In high school, but I used to tell my parents I wanted to be a dentist to see their reaction. I read popular astronomy magazines and books. I had a fascination for black holes and I also loved the beautiful images of nebulae and galaxies. The main driver for my early interest in astronomy was my Year 11 physics teacher, who had a strong interest in the field. He organised a camp in the Flinders Ranges where all of our practical experiments were astronomy-related. One of my favourite experiments was mapping the progress of Jupiter’s moons across the planet’s surface through the telescope. At the end of that year, I attended the National Science Summer School, held at the University of Canberra. I was in the astronomy group and we visited Mt Stromlo and the Department of Physics at ANU. During the visit, I saw that people could actually do astronomy as a career and I thought that would be fantastic.

R: How did your time at Mt Stromlo prepare you for a career in astronomy?

LK: Mt Stromlo gave me the firm foundation in astronomy research that has allowed me to compete for astronomy fellowships internationally and collaborate with astronomers from all over the world. I had a wonderful time there. The faculty’s expertise covers a broad range of research areas so there are many areas of the field that are open for PhD students. I decided to do my PhD on the relationship between star formation and black holes in luminous infrared galaxies. My supervisors were inspirational and extremely supportive. It was at Mt Stromlo where I learned how to carry out independent research, how to identify the important questions that need to be answered and how to design a project that can answer those questions. I learned to look at the bigger picture and to see where my research fits in, which is an important skill for young astronomers.

Unlike other university astronomy programs, the Research School of Astronomy and Astrophysics has its own telescopes at Siding Spring. I also spent a lot of time observing on the optical spectrograph on the Mt Stromlo 2.3m telescope. Once I had been taught how to use the telescope, I ran the telescope myself and took spectra of many galaxies. This telescope and the spectroscopy training were essential for my future observing runs. I am now using much bigger telescopes such as the 10m Keck telescope on Mauna Kea to observe very faint, far away galaxies.

R: Was it daunting making the move to Hawaii?

LK: I did a fellowship at the Harvard-Smithsonian Center for Astrophysics in Boston prior to moving to Hawaii. The move to the US was more exciting than daunting. As part of my PhD program at Mt Stromlo, I travelled to the US twice and I had been to international conferences where I met US astronomers. So the move wasn’t daunting I think because I already knew some people at different institutions here. They seemed very supportive of young people and were doing exciting research. There were also many other Australians astronomers in the US.

The move to Hawaii was very exciting. I was keen to use the biggest telescopes in the northern hemisphere, which are on Mauna Kea. The faculty at the University of Hawaii have very interesting research programs and they have been very supportive of my oxygen study. My first impressions of the islands were that they are very beautiful and the scenery intrigued me because the scenery and weather changes a lot within very small distances. Some parts of the Big Island look like Queensland while other parts look like the Hay plains, yet you can drive between them in a couple of hours.

R: What is it like viewing the night sky from Mauna Kea?

LK: Mauna Kea is an amazing site for observing. The mountain sits above the clouds, and the sky is often very clear and still. Astronomers can get very good quality images and spectra using telescopes on Mauna Kea. I think the night sky in Australia is more interesting to look at by eye though because you can see the Milky Way in Australia.

R: What is the observatory like at Mauna Kea?

LK: The observatory experience depends a lot on which telescope I am using. Observing on Keck is a lot like observing on the Mt Stromlo 2.3m or the Anglo-Australian telescope, because the astronomer runs the instrument. Much of the observing on Mauna Kea is done remotely because a lot of people suffer altitude sickness at 15,000 feet. There are control rooms at ground level filled with computers and a TV system where you can talk directly to the telescope operator. The control rooms are similar to the control rooms on the Mt Stromlo 2.3m or the Anglo-Australian telescope. However, on some telescopes like the Japanese Subaru 8m telescope, a support astronomer runs the instrument and the astronomer is there to make decisions about the progress of the observations.

R: How does your research technique work?

LK: I monitor the levels of oxygen in galaxies like our Milky Way to tell me how these levels have changed over time. This helps us understand how our galaxy evolved to include the levels of oxygen that we see today. Oxygen is created during generations of star formation. It’s then thrown into the interstellar gas by stellar winds and supernovae. In this gas, the oxygen becomes ionised. That is, the electrons on the oxygen atoms heat up and escape. Collisions with other particles then excite the ionised atoms. The oxygen atoms take energy from the other particles during a collision, and then this energy is radiated at certain specific wavelengths. We see this radiated energy as emission-line spikes in a spectrum of a galaxy. You can imagine this by looking at the colourful spectrum of light that passes through a prism. If you add some thin lines on top of that spectrum in the blue region, then this it is similar to what we observe when we look at galaxies.

There are three strong oxygen lines in an optical spectrum of a galaxy and there are also two strong hydrogen lines. I compare the strength of the oxygen lines to the strength of the hydrogen lines and this tells me the amount of oxygen (relative to hydrogen) in galaxies.
The amount of oxygen increases with each generation of star formation so the amount of oxygen in galaxies provides a fossil record of previous generations of star formation. I look at the oxygen in hundreds of galaxies at many different distances from us to obtain a picture of how the amount of oxygen changed in galaxies over time.

R: What has your oxygen study suggested about the history of the universe?

LK: My study suggests that there was a burst of oxygen production from huge amounts of star formation sometime during the first six billion years of the universe, and oxygen has been increasing fairly steadily since then.

R: Oxygen is essential for life on Earth. How do you feel about the connection between the air that sustains us and its astral origins?

LK: The free oxygen we have in the atmosphere today comes mainly from photosynthesis. In the Earth’s early atmosphere four billion years ago, oxygen atoms existed in the form of water. Recent work in planets around other stars suggests that if the amount of oxygen and other elements is high, then planets are more likely to form during the formation of stars. So understanding the amount of oxygen in our galaxy and in other galaxies helps us understand how life on our planet (and maybe life on other planets) came to be.

R: Where is your research heading now?

LK: I am continuing my project on the oxygen in galaxies, but now I am looking at different types of galaxies, such as those that have had very high energy bursts of light called gamma rays. Some of these gamma rays come from stars that are collapsing to form a black hole without losing much material in the process. My recent work, and the work of others, suggests that the gamma ray bursts are coming from galaxies that have very low amounts of oxygen and other elements - much lower than the amount of oxygen in our galaxy. Why would stars collapsing to form a black hole need low levels of oxygen and other elements? This is an exciting question that we’re trying to answer at the moment.