Scientists Stunned to Discover Star With Supersonic Tsunamis Three Times Higher Than the Sun

Each time a 4 million kilometer high tsunami crashes onto the star's surface, it releases enough energy to shatter the Earth hundreds of times over .

A giant star is experiencing violent waves three times the size of the Sun crashing onto its surface. Nicknamed the 'heartbeat star,' the unusual celestial body also periodically fluctuates in brightness as the gravity of its nearby companion star stretches it into a flattened sphere, Space reported on August 15.

In fact, the heartbeat star's massive wave is being pulled up by the companion star as it approaches in its 32.8-day elliptical orbit. Just as the Moon's gravity is responsible for causing tides on Earth by pulling the ocean toward it, the companion star's gravity pulls material from the heartbeat star and drags it away at supersonic speeds, creating a supertsunami.

The main star deformed into an oblate spheroid in the MACHO 80.7443.1718 system. (Image: CfA).

The binary star system, called MACHO 80.7443.1718, is located 169,000 light-years from Earth in the Large Magellanic Cloud. It consists of a primary star 35 times the mass of the Sun and a smaller companion star. Although they were first recorded to vary in brightness in 1990, scientists had not seen another star that fluctuated like this until NASA's Keppler space telescope came online and discovered dozens of similar stars.

Because the larger star in the system is distorted, it alternates between facing wider and narrower toward Earth, resulting in a pulsating brightness that resembles a beating heart. That's why scientists nicknamed the star a "heartbeat star." Normally, heartbeat stars fluctuate in brightness by 0.1%, but MACHO 80.7443.1718 is different. Every 32.8 days, it goes through a regular cycle of increasing its brightness by 20% , which is 200 times more than other heartbeat stars.

Using computer models of the gas dynamics on the surface of the system's giant primary star, astrophysicists Morgan MacLeod and Avi Loeb of the Harvard-Smithsonian Center determined that the MACHO 80.7443.1718 system contains more than just a heartbeat star, as the plasma waves that rise up as the companion star approaches collapse onto its surface, releasing enormous amounts of energy. "Each crash of the towering wave on the star releases enough energy to shatter the entire Earth hundreds of times over ," MacLeod said.

The waves on the heartbeat star are enormous, rising some 4 million kilometers above the surface. They form as the companion star approaches perihelion , the closest point in its 32.8-day orbit around the primary star. The primary star is also enormous, with a radius of 16.7 million kilometers, 24 times that of the Sun. The outer layers of this bloated star are diffuse and weakly held together by gravity, making them more susceptible to deformation by the companion star.

MacLeod and Loeb viewed heartbeat stars as a natural evolution of closely orbiting binary stars, but the high mass of the primary star seems to exacerbate the situation. Over the long lifetimes of stars many times more massive than the Sun, the orbits of the two stars around each other gradually become circular, eventually ending in a series of close approaches and distortions. However, massive stars like the primary star in the MACHO 80.7443.1718 system have much shorter lifetimes.

For example, MACHO 80.7443.1718 is only 6 million years old and will explode as a supernova in a few million years. In fact, it has stopped burning hydrogen in its core and is moving on to fusing helium, while it continues to burn hydrogen in its outer layers. This is a sign of a star's impending death as it rapidly burns through its fuel, from hydrogen to helium, then carbon, oxygen, neon, and silicon, and then to its iron core, shedding layers like an onion. The chain reaction stops at the iron core.

In this case, the transition from burning hydrogen to helium contributes to expanding the star's outer shell by 2-3 times, making the star puffier and more susceptible to the influence of the companion star. The research team published the findings in the journal Nature Astronomy.