Deep-space objects called 'centaurs continue to perplex NASA

Imagine a cosmic creature that blurs the lines between comets and distant icy objects. NASA has named these objects found roaming the outer reaches of our solar system “centaurs.”

Astronomers are beginning to learn more about these mysterious bodies thanks to observations from NASA’s James Webb Space Telescope.

Leading a recent study is Sara Faggi, a researcher at NASA’s Goddard Space Flight Center. She’s part of a team exploring one such object: Centaur 29P/Schwassmann-Wachmann 1, or simply 29P.

Using the powerful instruments aboard the Webb Telescope, Faggi and her colleagues have made discoveries that could change our understanding of these hybrid celestial bodies.

Their findings are helping scientists piece together the puzzle of our solar system’s formation.

Centaur 29P: A cosmic enigma

Centaurs in astronomy are named after the mythological creatures that are half-human, half-horse, symbolizing their hybrid nature.

Orbiting the Sun between Jupiter and Neptune, these objects are thought to be former trans-Neptunian bodies nudged inward by gravitational influences over the last few million years.

They’re in a transitional phase, sharing characteristics with both the distant Kuiper Belt objects and short-period comets.

What’s particularly fascinating about 29P is its highly active behavior. It experiences outbursts every six to eight weeks, making it one of the most active objects in the outer solar system.

“Centaurs can be considered as some of the leftovers of our planetary system’s formation. Because they are stored at very cold temperatures, they preserve information about volatiles in the early stages of the solar system,” explains Faggi, from American University in Washington, D.C

New jets found on Centaur 29P

The team utilized Webb’s Near-Infrared Spectrograph (NIRSpec) to gather data on 29P. They discovered a new jet of carbon monoxide (CO) and previously unseen jets of carbon dioxide (CO₂) gas. These observations offer new clues about the centaur’s nucleus and its composition.

“Webb really opened the door to a resolution and sensitivity that was impressive to us — when we saw the data for the first time, we were excited. We had never seen anything like this,” Faggi says.

The telescope’s unique imaging and spectral capabilities revealed two jets of CO₂ emanating in the north and south directions, and another jet of CO pointing toward the north.

Interestingly, while they detected CO and CO₂, there was no indication of water vapor in the atmosphere of 29P. This absence could be related to the extremely cold temperatures present in this body, making it too chilly for water ice to sublimate.

What do the jets tell us?

Based on the data, the team created a 3D model of the jets to understand their orientation and origin. They found that the jets were emitted from different regions on the centaur’s nucleus, even though the nucleus itself cannot be resolved by Webb.

“The fact that Centaur 29P has such dramatic differences in the abundance of CO and CO₂ across its surface suggests that 29P may be made of several pieces,” says Geronimo Villanueva, co-author of the study at NASA’s Goddard.

“Maybe two pieces coalesced together and made this centaur, which is a mixture between very different bodies that underwent separate formation pathways.”

This possibility challenges existing ideas about how primordial objects are created and stored in the Kuiper Belt.

It suggests that 29P might be an aggregate of distinct objects with different compositions, adding another layer of complexity to our understanding.

Outbursts and outgassing

Understanding why 29P exhibits these bursts in brightness and outgassing activity is a key area of interest. In comets, jets are often driven by the outgassing of water.

However, centaurs are too cold for water ice to sublimate, which means the nature of their activity differs. This raises questions about the mechanisms driving their behavior.

“We only had time to look at this object once, like a snapshot in time,” notes Adam McKay, a co-author of the study at Appalachian State University in Boone, North Carolina.

“I’d like to go back and look at Centaur 29P over a much longer period of time. Do the jets always have that orientation? Is there perhaps another carbon monoxide jet that turns on at a different point in the rotation period?”

Why study centaurs and 29P?

You might wonder, what’s the big deal about these icy bodies floating way out there? Studying centaurs like 29P isn’t just about satisfying curiosity.

These objects act like time capsules, preserving the conditions and materials from the early solar system. By understanding them, we can gain insights into how the planets, including Earth, came to be.

As scientists continue to study centaurs like 29P, they’re hopeful that these findings will enhance our understanding of how the solar system formed and evolved.

The team is optimistic that applying these techniques to other centaurs will expand the astronomical community’s knowledge.

By peering into these distant objects, we’re essentially looking back in time to the early stages of our cosmic neighborhood. Each discovery brings us one step closer to unraveling the complex history of our solar system.

The full study was published in the journal Nature.

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