“This fits the physical definitions of a comet, in that it is probably icy and throws dust into space, even though it also has the orbit of an asteroid,” Henry Hsieh, lead author of the new research and planetologist at the Planetary Science Institute said in a statement. “This duality and blurring of the line between what were previously thought to be two completely distinct types of objects – asteroids and comets – is a key part of what makes these objects so interesting.” Related: The Bernardinelli-Bernstein ‘Megacomet’ Is A Decade’s Discovery. Here is the discovery explained.
Despite its characteristics similar to those of a comet, the object’s orbit is definitely that of an asteroid: it revolves quietly around the sun in the outer part of the asteroid belt which lies between Mars and Jupiter, circling once every 5 years or so. The activity around the perihelion corresponds to the profile of a comet: increasing heat from the sun turns frozen ice into gas, a process called sublimation. Typical comets spend most of their time far enough from the sun that activity is frozen – literally.
Meanwhile, other scientists looked at 2005 observations QN173 collected by the dark energy camera in July 2016, the last time the object was around perihelion – and voila, here, too, they spotted a tail. “Most comets originate from the cold outer solar system, beyond Neptune’s orbit, and spend most of their time there, with their very elongated orbits only bringing them closer to the Sun and Earth for short periods of time. at a time, “Hsieh said.” During the times when they are quite close to the sun, they heat up and release gas and dust as a result of the sublimation of the ice, producing the fuzzy appearance and often spectacular tails associated with comets. ”
In these observations, the object was moving away from the sun, having made its closest approach, or perihelion, on May 14. (Although the close approach of a comet is much more dramatic than that of a typical asteroid in the main belt, the sun moves further and further away from it during one orbit. Earth’s perihelion, for example, falls in early January.) in Hawaii on July 7 noticed the object sporting a tail. The feature appeared in additional observations made by a telescope at the Lowell Observatory in Arizona. Scientists then checked previous sightings made by other facilities and again spotted the tail on images collected on June 11 by the Zwicky Transient Facility in California.
The new research included old sightings taken from the archives of various instruments originally collected between 2004 and 2020 at times when the comet was not active, in order to better understand the object itself. These observations suggest that the comet’s nucleus or head is about two miles wide, the statement said. Of the half a million objects scientists have examined in the asteroid belt, this is the eighth that scientists have been able to confirm has been active multiple times, and it is one of 20 ” presumed mainbelt comets.
“This extremely narrow tail tells us that dust particles barely float out of the nucleus at extremely slow speeds, and that the flow of gas escaping from the comet that normally lifts dust from a comet into space is extremely low, ”Hsieh said. Then, the scientists incorporated new observations of the object made by a multitude of instruments in July and August to better understand the activity of the strange main belt comet. In particular, the researchers were able to measure the tail of the object, which in July stretched 450,000 miles (72,000 kilometers) long, just under twice the distance from Earth to the Moon. But despite its massive length, the tail is not that wide, which poses a new puzzle for scientists.
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- Title: Is it an asteroid or a comet? This strange object in the solar system is actually both.
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