The cosmic beat of Trappist-1

While the Trappist-1 system may not be brimming with life - it has an undeniable interplanetary groove

The cosmic beat of Trappist-1

Illustration of the Trappist-1 system showing potential water states in each zone. mage: NASA/JPL-Caltech

When scientists announced the discovery of the TRAPPIST-1 system, a relatively short hop down the astronomical highway, space enthusiasts around the world could barely contain their excitement.

The system, which hosts seven ‘Earth-sized,’ rocky planets offered a hugely promising avenue in the ongoing search for extra-terrestrial life.

Three of the planets were found to be located in the ‘Goldilocks zone’ - the area around a parent star where temperatures are not too hot or too cold - meaning they could be capable of hosting oceans of water.

Michaël Gillon, lead author of the study that originally discovered the system, called it “the best target yet for studying the atmospheres of potentially habitable, Earth-size worlds."

While concerns over intense solar radiation may have dampened those expectations in the months following the discovery - the remarkable system is still throwing up fascinating new findings. 

Personal space invaders

At about 40 light-years (378 trillion kilometres) from Earth, the system of planets is relatively close by in astronomical terms - in the constellation Aquarius.

According to the scientists responsible for the discovery, the planets orbit so closely to each other that if a person was standing on the surface of one, they could gaze up and see geological features or clouds on the neighbouring worlds.

As a dwarf star, Trappist-1 is far smaller than our own sun and the seven orbiting planets are located within six million miles of its surface.

Earth, by contrast, is nearly 93 million miles from the sun.

However, this proximity brings with it a new conundrum – how can these planets orbit so closely to each other without colliding in epic inter-planetary destruction?

Based on computer simulations, scientists consistently found that after about half-a-million years the planet’s circular orbits should have become more elliptical, leading to orbital intersections – and doomsday-level consequences.

Considering the star is believed to be somewhere between three to eight billion years old, researchers were left with a puzzle.

Orbital resonance

The answer, according to a study published this week, lies in the planet’s “orbital resonance.”

Instead of simply studying the orbits of the planets as they are today, researchers simulated possible ways the planets could have arrived at this point.

In short, the research suggests that the gravitational tug of each planet has worked in concert to keep each orbit stable and circular – ensuring two worlds are never found in the same place at the same time.

This resonance means that the planet’s orbital periods form whole number ratios – repeating rhythmically, similar to the manner in which Neptune and Pluto dance around our own sun.

The paper’s lead author, Dr Dan Tamayo from the Centre for Planetary Sciences at the University of Toronto, said the system likely comprises a “chain of resonances” – adding that “this is the longest one that has ever been discovered in a planetary system.”

“They key piece of information here is actually when you look at how long each planet takes to go around the central star,” he said.

“Those orbital periods, they form an incredibly precise progression. For every two orbits of the outermost planet the next one in does three; the next one after that does four, then six, nine, 15, 24 – it is just like clockwork.

“When we tuned that precisely, we can get these systems to survive for as long as we can possibly simulate them on a supercomputing cluster.”

Cosmic beats

In an effort to illustrate the theory, Dr Tamayo teamed up with astrophysicist, Matt Russo – a scientist conveniently located in the office next door.

Dr Russo – a researcher at the Canadian Institute for Theoretical Astrophysics and guitarist in the indie-pop group Rvnners – took a novel approach.

Using the computer simulations, Dr Russo created an animation of the system’s orbital map and added a piano note for every time a planet crosses in front of its star.

The team then built out the composition - adding a drum beat every time a planet overtakes a neighbour. 

The result is a cosmic symphony- and a beautiful representation of the precise clockwork configuration that has allowed the system to survive for billions of years:

“This may sound like a remarkable coincidence but it turns out that the system was tuned this way early on when it was evolving,” said Dr Russo.

“It is kind of funny because most planetary systems are like bands of amateur musicians – they are all playing parts but at different speeds.

“Trappist-1 is different though – it is like a supergroup where all seven members are synchronising their parts in nearly perfect timing.”

The theory has a long way to go before it is fully verified, however the Canadian researchers believe the planets likely migrated to their current orbital positions as they came together billions of years ago.

You can hear the two scientists discuss the study in the below video: