A comet never seen before has been discovered by a citizen scientist on Monday using data from the Solar and Heliospheric Observatory (SOHO). It is the 4,000th comet to be discovered to date in the more than the two-decade lifespan of the spacecraft.

Until the comet's official designation from the Minor Planet Center, scientists are calling the 4000th space rock SOHO-4000. It has a diameter of between 15 and 30 feet, impossible to see from where we are (with or without a telescope), and move through the outer atmosphere of the sun.

As with other comets discovered using SOHO, SOHO-4000 is part of the Kreutz family of sungrazers. Comets belonging to the Kreutz family all follow a similar general trajectory, characterized by orbits taking them extremely close to the Sun at perihelion.

"I feel very fortunate to have found SOHO's 4,000th comet," Trygve Prestgard, the discoverer of the comet, said. "Although I knew that SOHO was nearing its 4,000th comet discovery, I did not initially think that this sungrazer would be it. It was only after discussing with other SOHO comet hunters, and counting through the most recent sungrazer discoveries, that the idea sunk in."

SOHO scientists knew they were on their way to finding the 4000th comet, but they didn't expect to discover it this soon. The spacecraft did, however, complete a special observing run last month to coincide with NASA's Parker Solar Probe fifth Sun flyby, which gathered more data of the same solar structures. SOHO's usual exposure time has been doubled as well, making way for the discovery of fainter and smaller objects like SOHO-4000.

SOHO is a joint mission of NASA and the European Space Agency (ESA), which started in 1995. It makes observation of the Sun, with an uninterrupted view from its vantage point between our home planet and the yellow dwarf, about 152 million kilometers from Earth.

Its ability to identify comets is due to its sensitive tools focused on the solar corona, its long lifespan, and through the dedication of citizen scientists who tirelessly scour heaps of data in order to map out undiscovered comets. SOHO's coronagraph, known as LASCO, has both high sensitivity and a wide field of view.

Over the past two decades, SOHO has discovered well over half of all known comets. Prestgard, meanwhile, has around120 comets to his credit, which he found using data from SOHO and NASA's STEREO mission.