The first time discovered the water drop star

Due to the impact of gravity in the binary star system, the HD74423 star in the Milky Way is pulled deformed on one side of the hemisphere.

Graphic simulating water droplet star with red dwarf companion.(Photo: Gabriel Pérez Díaz).

The discovery was led by international astronomers led by Dr. Simon Murphy from the University of Sydney, Australia, using NASA's TESS extraterrestrial hunting space telescope. The star weighs 1.7 times the Sun and lies about 1,500 light-years from Earth.

"The first thing that caught our attention was that HD74423 was chemically bizarre," Murphy said. "Stars like this are usually rich in metal but HD74423 is the opposite, making it a rare hot star."

HD74423 is classified as a heartbeat star - the term for double star variables (whose light changes periodically) caused by the gravitational attraction of the companion star. In binary stars, when one star has an elliptical orbit that moves closer to the other star, gravity pulls it into a non-spherical shape, changing the brightness. However, all previously known heart rate stars are deformed on both sides of the hemisphere. HD74423 is the first case to deform only on one side, giving it a unique teardrop shape.

Astronomers, in theory, have been skeptical of the existence of teardrop-shaped heart stars since the 1980s . "We have been looking for such a star for nearly four decades but have now discovered it," said Don Kurtz, co-author of the study from Central Lancashire University in the UK.

In the case of HD74423, its unusual shape is caused by a companion smaller dwarf star. The two stars orbit very quickly, at close distances, with each round taking less than two days. This causes the larger star to become deformed as a teardrop. Details of the study were published in the journal Nature Astronomy on March 9.