UCT Astronomer’s Photo of Neutron Star Makes Headlines

A picture of a neutron star taken by South African astronomer Kelebogile Gasealahwe has been featured as NASA’s Astronomy Picture of the Day.

Gasealahwe, who has just completed her PhD at the University of Cape Town (supervised by Itumeleng Monageng), published a paper on her work on neutron star Circinus X-1 in August. A reviewer suggested she submit an image of the star and the companion star it orbits to the editors of the website Astronomy Picture of the Day. She did so, and it was chosen as the picture of the day, appearing on 3 September.

At just 4,600 years old, Circinus-X is one of the youngest X-ray neutron stars yet documented, says Gasealahwe. It is thought to be 30,700 light-years away from Earth (the distance light could travel in 30,700 years, at a speed of nearly 300-million metres a second).

“It’s not been well studied yet; it’s still young and very active,” she says. “So there’s a lot of things happening, but the main thing is we think it’s a neutron star.”

The picture shows the flares from the star pair, which she studied with the Meerkat radio astronomy telescope in the Northern Cape.

“It has these regular sort of flares – outbursts every sort of 16 and a half days – and we monitored it with Meerkat,” she says. “So we were able to observe it every day for 34 days and with the data we were able to build an image.”

Astronomers hope the work will provide clues about how soon jets form when a supernova (the explosion of a star) gives birth to a very dense neutron star. The image shows Circinus-X’s currently active jets inside the nebula.

MeerKat, a seven-dish telescope near Carnarvon, was built as part of South Africa’s bid for the giant Square Kilometre Array (SKA) radio-telescope. South Africa won the bid jointly with Australia in 2012. The SKA is still under construction.

One of the main motivations for the investment in Meerkat was that it would inspire black South Africans to pursue careers in science, including astronomy. A second motivation was that it would lead to economic development of the Northern Cape, one of the country’s poorest provinces.

Gasealahwe, the only child of a single mother, hails from the provincial capital of Kimberley. Her mother died when she was still at school, but her grandmother took over as her guardian. Her family were supportive of her ambitions for university education.

She says that as a child she admired the night-sky. “I found myself stargazing what felt like every night. Truly in awe of the beautiful creation.”

She went to Kimberley Technical High School, which offered engineering subjects, so she thought she would become an engineer.

“But I still had astronomy in the back of my mind and figured, you know what, I’m going to be the scientist and not the engineer, so I’m going to study astronomy.” She was accepted by UCT around the time that the outcome of the SKA bid was announced.

As an undergraduate, Gasealahwe was funded by the National Student Financial Aid Scheme and the Northern Cape Premier’s Trust fund. She went on to do honours and master’s degrees in optical astronomy, funded by the National Astrophysics and Space Science Programme, working on data collected at the Southern African Large Telescope at Sutherland.

She changed to radio-astronomy at PhD level. “Coming from an optical astronomy background, I was quite excited to expand my expertise in the radio astronomy field due to the growth prospects from MeerKAT and the future SKA.”

Now she’s about to start a postdoctoral fellowship. Married to an engineer, she has two sons, the younger born on Freedom Day this year, six weeks before she submitted her doctoral thesis.

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