Scientists using the world’s most powerful array of radio telescopes have caught a giant comet in unexpected ways, while still freezing and far from the sun.
These observations suggest that carbon monoxide gas erupts in the evolving jet mode of Comet C/2014 UN271, a hockey puck within a 140-km range and is the largest known comet in the mysterious Oort cloud.
The findings, published in the Journal of Astrophysics letter, mark the first discovery of molecular activity in the record comets and provide new insights into how these ancient objects operate in operation far beyond the warmth that usually drives comet behavior.
Watch the jet develop in real time
The researchers observed C/2014 UN271 in March 2024 using the Atacama Large Millimeter/Submillimeter Array (ALMA) in Chile, while the distance from the Sun is much more than 16.6 times higher than that of the Earth, which is the distance from Uranus. At such extreme distances, most comets are still dormant.
However, this cosmic giant proved surprisingly active. The telescope detected carbon monoxide gas flowing out of the nucleus from the asymmetric jets of the carbonaceous gas moving sharply between observation sessions only nine days apart.
“These metrics give us an idea of how this huge, icy world works,” said Nathan Roth, chief writer at American universities and NASA Goddard Space Flight Center. “We see explosive beyond style patterns that raise new questions about how the comet develops as it continues its journey toward its inner solar system.”
Temperature clues of gas velocity
The research team made a particularly interesting finding, which was not emphasized in the initial announcement: They could calculate the surface temperature of the comet by measuring the rate at which carbon monoxide gas is removed from the nucleus.
The gas expansion rate shows that the surface temperature is around 60 kelvin (minus 213 degrees Celsius) – colder than the 95 kelvin predicted by the standard thermal model. This unexpected discovery suggests that the surface properties of comets differ from the typical assumptions of how these objects absorb and heat.
Consistent air velocities across different observation dates also indicate that the jet originates from a specific active region on the nucleus rather than a random burst.
Ancient chemistry has been preserved
C/2014 UN271 represents a scientific treasure as it enters the inner solar system after spending millions of years in the dirt clouds that have spent millions of years. The remote shell of this cold object retained material from the earliest days of the solar system.
ALMA measured carbon monoxide productivity at 4.7 × 10²⁷ molecule per second – competing for the carbon seen in the famous comet of Hale-Bopp. However, considering that UN271 is much larger in size, this suggests that its surface composition is very different from other good comets.
Multiple activity modes
This observation shows a complex two groups of people over the system:
- Fast moving sunlight jets that produce gas at a speed of 0.386 km per second
- Slower, slower component, 0.212 km per second
- Constantly changing spatial patterns of changes in the period of observation
Complementary optical observations of the LAS CUMBRES Observatory telescope show that the comet experienced a major outbreak in late February 2024, gradually returning to normal levels during Alma observations, rising by nearly half.
What will happen next?
As C/2014 UN271 continues to approach the Sun, scientists expect additional frozen gas to be activated when it reaches the closest point of Saturn’s distance in 2031. Based on the temperature threshold, ethane, hydrogen sulfide and other volatiles may have begun to activate as the comet is heated further.
The study shows how modern telescope technology detects the behavior of objects at previously impossible distances. Why is this beyond scientific curiosity? Understanding these original time capsules helps to reveal the chemical conditions that exist when planets form, including the sources of water and organic compounds that make the Earth habitable.
Alma’s excellent sensitivity allows scientists to detect weak radio signals of carbon monoxide molecules even at such extremely high distances, providing new possibilities for studying the oldest residents of the external solar system.
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