After a 40-year search, astronomers have spotted a first-of-its-kind star that pulsates on just one side.

Amateur astronomers played an important role in the discovery by trawling through data from NASA’s planet-hunting Transiting Exoplanet Survey Satellite (TESS).

The “one-sided pulsator” was spotted in the Milky Way about 1,500 light-years from Earth, according to researchers. A light-year, which measures distance in space, equals about 6 trillion miles.

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The star, which is known as HD74423, is about 1.7 times the mass of the Sun.

An international team of astronomers harnessed a wealth of data to make the discovery. Their research is published in the journal Nature Astronomy.

"What first caught my attention was the fact it was a chemically peculiar star," said co-author Simon Murphy, Ph.D. from the Sydney Institute for Astronomy at the University of Sydney, in a statement. "Stars like this are usually fairly rich with metals - but this is metal poor, making it a rare type of hot star."

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Other astronomers had also started to study the star. "We've known theoretically that stars like this should exist since the 1980s," the study's co-author, Don Kurtz, who is from the U.K.’s University of Central Lancashire, said in the statement.

"I've been looking for a star like this for nearly 40 years and now we have finally found one," added Kurtz, who is also the inaugural Hunstead Distinguished Visitor at the University of Sydney.

While astronomers have known about pulsating stars for a long time, stars that oscillate over just one hemisphere are a new phenomenon. HD74423, the researchers explain, is in a binary star system with a red dwarf, or small, cool star. “Its close companion distorts the oscillations with its gravitational pull,” the researchers explained, in the statement. “The clue that led to its discovery came from citizen scientists poring over public data from NASA's TESS satellite, which is hunting for planets around distant stars.”

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Because the orbital period of the binary system is less than two days, HD74423 is being distorted into a teardrop shape by the red dwarf’s gravitational pull.

"The exquisite data from the TESS satellite meant that we could observe variations in brightness due to the gravitational distortion of the star as well as the pulsations,” said Professor Gerald Handler from the Nicolaus Copernicus Astronomical Centre in Poland, who is the study’s lead author.

Experts believe that other similar stars exist.

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The pulsating star is the latest in a series of fascinating discoveries by astronomers across the globe.

In another project, for example, a 77-year-old amateur astronomer recently helped discover a rare galaxy double nucleus. Allen Lawrence, a retired electrical engineer, used infrared images from NASA’s Wide-field Infrared Survey Explorer to reveal the double nucleus galaxy.

NASA also recently announced that a 17-year-old summer intern made an incredible planet discovery. Wolf Cukier, a student from Scarsdale High School in New York, had just finished his junior year when he started his internship at NASA’s Goddard’s Space Flight Center in Goddard, Md., last summer. Within just a few days, he made an incredible find while sifting through variations in star brightness captured by the space agency’s Transiting Exoplanet Survey Satellite (TESS) uploaded to the Planet Hunters TESS citizen science project.

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A signal from a distant system called TOI 1338 turned out to be a planet. The planet, TOI 1338 b, is the first circumbinary planet, or world orbiting two stars, that has been spotted using TESS data. TOI 1338 b is about 6.9 times larger than Earth, which means that it is between the size of Saturn and Neptune.

Follow James Rogers on Twitter @jamesjrogers