A Rare Hybrid of a Comet And an Asteroid Is Showing Off Its Cometary Traits

Centaurs are rare celestial objects which will combine a number of the various features of asteroids and comets. They're basically rocky in nature, like asteroids, but may also throw out clouds of dust and gas as their exteriors vaporize, like comets.

When centaurs emit these gases, they're considered active. We've only ever found 18 chemically active centaurs within the last century some, but now a replacement one has been added to the list – and it would be ready to tell us more about how these mysterious flying rocks develop their unique characteristics.

Keeping a detailed eye on centaurs may be a huge challenge – they seem to be a great distance away, orbit in irregular ways, and take up lots of telescope time – but during this case, researchers studied archival images similarly as used new data gathered from the Dark Energy Camera at the Inter-American Observatory and therefore the Walter Baade Telescope at the Las Campanas Observatory, both in Chile, and therefore the Large Monolithic Imager at Lowell Observatory's Discovery Channel Telescope in Arizona.

"We developed a unique technique that mixes observational measurements – for instance, colour, and dirt mass – with modelling efforts to estimate such characteristics because the object's volatile sublimation and orbital dynamics," says astronomer Colin Chandler, from the Northern Arizona University.

That technique, involving a specially developed algorithm to appear for activity traces in existing space imagery, revealed evidence of Centaur 2014 OG392 converting solids into gases (sublimation) and giving up a protracted comet-like halo.

Backed up with new observations recorded over the course of the past two years, it seems clear that this particular centaur is special. Computer modelling then helped the astronomers work out what kinds of ice might be burning off the rock.

It's a tricky calculation to create, not least because the asteroid is perhaps not made of one form of ice but from a combination of materials that may all burn differently. The researchers think they know what's happening, however, and what can be happening on other similar objects.

"We detected a coma as far as 400,000 km [248,548 miles] from 2014 OG392," says Chandler, "and our analysis of sublimation processes and dynamical lifetime suggest carbonic acid gas and/or ammonia are the foremost likely candidates for causing activity on this and other active centaurs."

A coma is an envelope of ice and comet dust that forms around the comet's nucleus because it passes near the Sun. it's the coma that provides comets with their fuzzy appearance.

Because of the invention, The Centaur is not any longer a centaur any longer – it is a fully-fledged comet, with the designation C/2014 OG392 (PANSTARRS), something that the researchers are "very excited" about.

These varieties of objects, et al. like them, are thought to possess barely changed since the very period of time of the system, which means they're incredibly useful time capsules for studying how our planets formed and settled into their own orbits.

Any centaurs, comets, and asteroids that are still around are still around for a reason – they haven't spun out of the scheme or flown into the Sun – and scientists can work backwards from that.

There's lots more to get about centaurs, and we're learning more about how they work all the time. As more data is gathered and better analysis techniques are developed, we should always finally be able to solve a number of the mysteries surrounding these weird and wonderful system travellers.