Imagine surfing on a wave that is as high as three suns. Sounds impossible, right? Well, not for one star in a distant galaxy, where such waves are a reality. Astronomers have discovered a star system where one of the stars has huge and powerful waves on its surface, caused by the gravity of another star that orbits very close to it. The waves are so big that they are as tall as three suns, and they break and crash on the star’s surface, releasing a lot of energy. The star system is called MACHO 80.7443.1718, and it is the most extreme example of a heartbeat star, which is a type of star that pulses in brightness because of its shape changes due to tides. The discovery was published in Nature Astronomy by researchers from the Center for Astrophysics at Harvard and the Smithsonian.
How did they find it?
The researchers used computer simulations to model the star system and explain its unusual behavior. They also analyzed data from NASA’s Transiting Exoplanet Survey Satellite (TESS), which observes stars for changes in brightness. They found that MACHO 80.7443.1718 has a very irregular light curve, which means that its brightness varies a lot over time. This is because the two stars are so close together that they distort each other’s shape and create tides on their surfaces. The tides are especially strong on the smaller star, which is about half the size of the sun, and they produce giant waves that travel around the star.
The researchers compared their simulations with the observations and found a good match. They were able to reproduce the light curve and the shape of the stars, as well as the speed and direction of the waves. They also calculated the height of the waves, which turned out to be about 300 kilometers high, which is equivalent to three times the diameter of the sun.
Why is it so special?
The researchers estimate that the waves on the smaller star are about 300 kilometers high, which is equivalent to three times the diameter of the sun. The waves are so powerful that they break and crash on the star’s surface, creating shock waves that heat up the gas and make it glow brighter. This is why the star system has such a dramatic light curve.
The researchers also found that the smaller star rotates faster than the larger one, which is unusual for such a close pair of stars. They think that this is because the waves transfer angular momentum from one star to another, making them spin at different speeds. This discovery could help us understand how tidal forces affect the evolution of stars and planets in other systems.
What are heartbeat stars?
Heartbeat stars are a rare class of binary stars that have very eccentric orbits, meaning that they are very far apart at some points and very close together at others. When they are close together, they experience strong gravitational interactions that change their shape and brightness. These changes can be detected by telescopes like TESS, which can help us learn more about the physical properties and dynamics of these stars.
Heartbeat stars can also help us find planets around them, because some of them have small dips in their light curves that indicate the presence of a third body in the system. For example, one of the first heartbeat stars discovered by TESS was found to have a planet orbiting around it.
What does it mean for us?
The discovery of MACHO 80.7443.1718 shows that heartbeat stars can have very extreme and complex behaviour that challenges our understanding of stellar physics. It also demonstrates the power of computer simulations and data analysis to reveal new phenomena in the cosmos.
As one of the authors of the study said, “This system offers a unique laboratory to study how stars can interact with each other in very violent ways.”
