An astronomy expert explains how The Bachelor's research will help us discover new planets

As an astronomer, I’m used to talking about the stars - the ones above, the distant suns and the worlds that orbit them. But this week, I’ve been swept along in discussions of an entirely different kind of star - and it’s all thanks to a reality TV show called The Bachelor Australia.

The reason? This year’s Bachelor is Matt Agnew, who just finished his PhD at Swinburne University. I had the great privilege of helping to supervise Matt’s studies, so it’s been really bizarre to see him in a whole new light, handing out roses rather than prospecting for alien worlds.

While he’s reportedly already chosen one of the 28 candidates on the show, I know Matt is also passionate about the search for alien worlds, with TESS (as I’ll explain in a moment).

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Our latest Bachelor did some amazing work for his PhD - and if his very public search for true love helps to also spread the word of his amazing research, then that’s a win-win as far as I’m concerned!

So what did Matt do, before he became a heart-throb? And who, or what, is TESS?

Helping to prospect for alien worlds

Astronomers searching for planets around other stars face a big problem. Simply put, we are finding planets around huge numbers of stars, at an ever-accelerating rate.

But there are far too few facilities available on the ground to follow up on all those planetary systems and learn more about them. As a result, we have to find ways to work smarter, not longer - to make our searches ever more efficient and effective.

That problem will only become more pronounced in the coming years, with NASA’s Transiting Exoplanet Survey Satellite (that’s TESS) expected to discover thousands of new alien worlds.

Launched in April last year, TESS has already found 28 confirmed planets, but a further 993 remain as “candidates” that need urgent ground-based follow-up.

That’s where Matt’s PhD research comes into play. My colleagues and I have, for the past decade or so, used computer modelling of proposed planetary systems to separate the wheat from the chaff - to identify planetary systems that are not all they seem to be.

By studying how the proposed planets in a given system would interact with each other over millions of years, we can show that some of those systems simply don’t work. The planets we thought were there just don’t exist.

From a certain point of view

Matt turned this idea on its head. If you turn this technique around, you can predict the best places to search for new alien worlds.

Imagine that we find a new planetary system, with a huge planet, maybe as big as Jupiter, moving on an orbit that takes 100 days to complete around its host star. That planet will exert a strong gravitational pull on other objects in the same system, stirring them up, and clearing the space around it.

Now imagine you want to search for other planets in that system. Where should you look?

One approach would be just to study the star continuously, watching day-in, day-out, for any sign that it hosts additional planets. That allows you to find planets on a wide variety of orbits, from those close to their host to those that lurk in the icy depths, far from the star.

But that method is really resource-intensive and inefficient.

Imaginary planets

That’s where Matt’s work came in. We can simulate the effect of the first planet we discover on imaginary planets moving on a wide variety of orbits around their host star. With modern computers, we can run simulations that cover millions of virtual years in just a few hours, or a few days at most.

That allows us to discover which of those imaginary planets could actually exist. Those that aren’t feasible might crash into their host star, or collide with the known planet (in the simulation).

In other words, they aren’t physically feasible. So there’s no point spending huge amounts of precious resources (telescope time) searching for planets that can’t be there in the first place.

Matt published his work in four peer-reviewed papers, which are freely available online (here, here, here and here).

They’re well worth a read, and tell a fantastic story of how we can use theoretical methods, and fast computers, to help make the search for alien worlds an easier and more productive game.

The future - planets and roses

Matt did fantastic work during his PhD - and I’m confident his work will be important in the years to come. We’re implementing his results into our work with the new Minerva-Australis observatory, our very own planet-finding facility.

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By making sure we only search for planets that could realistically exist, we’ll be able to scour the sky more efficiently, helping us to find and characterise as many alien worlds as possible.

Hopefully, his time on The Bachelor will be as productive. While I’ve seen and heard conflicting views among scientists as to the value of having an astrophysicist front and centre on that kind of show, I’m personally really positive about it.

I’d like to think Matt will be a fantastic advocate for science and astronomy. He’s an eloquent communicator, and passionate about our search for new worlds and for life elsewhere.

In much the same way the particle physicist Brian Cox (who also happens to be a famous rock star) has been able to engage huge numbers of people in science who might previously have had little interest, it might well be that Matt’s stint as The Bachelor will encourage his audience to learn more about the universe around them.

Even if it just helps people to learn the difference between astronomy and astrology, I’d consider that a win.

Jonti Horner was the external supervisor for Matt Agnew's PhD work, which was undertaken at Swinburne University of Technology.