\u201cThe images we collected from these observatories showed a weak but clear tail, thus confirming that 1998 SH2 is, in fact, a comet,\u201d said Olivier Hainaut, an astronomer with the European Southern Observatory and coauthor of the study. \u201cThat\u2019s how science works \u2014 you form a hypothesis, and you set out to test it. This data is exactly what was needed to confirm our hypothesis that 1998 SH2 was a comet.\u201d<\/p>\n
As an outcome of the investigation, 1998 SH2 will receive an additional comet provisional designation, P\/1998 SH2.<\/p>\n
Planetary defense implications<\/p>\n
The research also sheds light on another, even more unusual, class of objects called dark comets<\/a>. Like 1998 SH2, dark comets exhibit significant irregularities, or perturbations, in their trajectory but lack other visible evidence of comet activity \u2014 there\u2019s no coma, tail, or visible outgassing. These enigmatic objects fall into two distinct populations: larger ones with orbits similar to those of Jupiter-family comets (short period comets<\/a> with highly elliptical, or eccentric, orbits), and smaller ones that orbit closer to the Sun. Since the 2016 discovery of the first dark comet, about a dozen more have been identified.<\/p>\n The paper\u2019s authors suggest that many of the larger dark comets, which have orbits like 1998 SH2\u2019s, could turn out to be regular comets if astronomers get the right opportunity to observe them with powerful telescopes capable of imaging incredibly faint objects. And by analyzing the motion of all near-Earth objects using precision astrometry data, researchers may reveal more comets that were previously designated as asteroids if they exhibit cometlike nongravitational perturbations.<\/p>\n \u201cThis work shows the importance of continuously tracking near-Earth objects,\u201d said Farnocchia. \u201cBecause of outgassing, the motion of comets is more significantly perturbed than that of asteroids. Detecting these perturbations can be an important diagnostic tool for planetary defense that will help understand which objects may be comets rather than asteroids, how their orbits evolve, and how that influences their Earth impact risks.\u201d<\/p>\n Hunting for near-Earth objects<\/p>\n