Astronomers have discovered a teardrop-shaped star that pulsates on just one side. The star, called HD74423, is located in a binary system 1,500 light-years away from Earth, is around 1.7 times the mass of our sun, and is accompanied by a nearby red dwarf. In fact, they are so close to each other that their orbit lasts just 1.6 days.
Scientists say that the reason why the oddly-shaped star pulsates on just one side is because of the gravitational pull from the closely situated red dwarf, turning the star into the shape of a teardrop and causing it to pulsate in a very strange manner. The majority of stars pulsate on all sides, so this is definitely a unique observation although scientists have known about this for quite a while. Don Kurtz, who is from the University of Central Lancashire in Britain as well as the co-author of the study (which can be read in full here), stated, “We've known theoretically that stars like this should exist since the 1980s,” adding, “I've been looking for a star like this for nearly 40 years and now we have finally found one.”
Amateur astronomers had initially noticed that the star’s light curve was “out of the ordinary” so they sent their information to Saul Rappaport from the Massachusetts Institute of Technology who then contacted another colleague and eventually the news was sent to Kurtz. Dr. Simon Murphy, who is from the Sydney Institute for Astronomy at the University of Sydney, also noticed HD74423’s unique characteristics and called it “chemically peculiar” and a “rare type of hot star”.
Since the red dwarf is so close to HD74423 that it’s pulling at one side, scientists were able to observe this interaction by using data from NASA’s TESS Satellite. Dr. David Jones, who works at the Instituto de Astrofisica de Canarias and is co-author of the study, explained, “As the binary stars orbit each other we see different parts of the pulsating star,” adding, “Sometimes we see the side that points towards the companion star, and sometimes we see the outer face.”
By studying that data, astronomers were able to conclude that the star does in fact only pulsate on one side. They noted that the small fluctuations in the star’s brightness only showed up when the same hemisphere was pointed towards the telescope, giving further validation of the unusual pulsating pattern. A video of HD74423 pulsating can be seen here.
Even though this is the only star thus far that has been found to pulsate on just one side, scientists think that there could be many more out there that are just waiting to be found in the data collected by the TESS Satellite.