Everyday choices: Talvikki Hovatta, what is a relativistic jet?
What sparked your interest in space?
I’ve been an avid reader since I was a child. My interest in space began when I started reading my brother’s astronomy books. After that, my mother began bringing me all sorts of astronomy books from her conference trips.
I spent every summer vacation lying in a tent in our yard reading – even on our winter holidays, I had to bring ten books along. I still read a lot, but these days it’s not only about astronomy.
You’re currently studying, among other things, the composition of relativistic jets launched by black holes. What exactly are these jets?
Powerful magnetic fields are anchored to black holes or to their surrounding accretion disks – the matter orbiting black holes. These magnetic fields twist into something like a spring, which likely propels some of the orbiting material into jets. The particles in the jets accelerate to nearly the speed of light, and since they travel so fast, they emit radiation. That radio emission is what we detect here on Earth. By analysing the properties of that radiation, we can model the kinds of particles in the jets.
Why hasn’t this been figured out before?
When studying such distant objects, the signals we receive are naturally very weak. We don’t just study the intensity of the light – that is, its brightness – but also its direction, or polarisation. That requires extremely sensitive equipment, and now we’re getting a new, high-quality receiver at Metsähovi that will make this research possible. To determine the composition of the jets, you also need a telescope with ample observation time – which is rare for large telescopes.
What are some common misconceptions about space research?
People often think of black holes as vacuum cleaners in space, heading toward us and sucking everything in. That’s not true. If the Sun were to suddenly become a black hole with the same mass, it wouldn’t suck us in. Life on Earth would end, of course, but our planet would continue orbiting the black hole just as it orbits the Sun now.
Another misconception comes from films like Contact, where Jodie Foster wears headphones to listen to space signals. We don’t listen to space with headphones – the signals go to a computer. That said, at Metsähovi, it is actually possible to listen to those signals, and it’s a lot of fun.
What’s your favorite thing about space?
I’m especially fascinated by black holes. Of course, I also have favourite quasars – ones I’ve been ‘stuck with’ for a long time and where something exciting is happening. One of them is 3C273, the first quasar ever discovered. Even though it’s been extensively studied, I still find it fascinating. I’m currently writing a research paper about it, based on some amazing magnetic field data we collected using the world’s most sensitive millimeter-wavelength telescope array in Chile.
This article has been published in the Aalto University Magazine issue 36 (issuu.com), September 2025.
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