SOFIA finds keys hidden in the haze of Pluto

US, WASHINGTON (ORDO NEWS) — When the New Horizons spacecraft passed Pluto in 2015, it discovered one of its many amazing features in its images. It was that this small, cold world in a distant solar system has a foggy atmosphere. Now, the new data helps explain to us how the haze of Pluto is formed from the faint light of the Sun, at a distance of 6 billion kilometers, when it moves in its unusual orbit.

Remote observations of Pluto using the SOFIA telescope mounted on an airplane show that the fine haze enveloping Pluto consists of very small particles that remain in the atmosphere for a long period of time and do not immediately fall to the surface. SOFIA data show that these particles of fog are actively replenishing – a discovery that redefines predictions about the fate of Pluto’s atmosphere as it moves to even colder regions of space in its orbit of 248 Earth years around the Sun. The results are published in the scientific journal Icarus.

“Pluto is a mysterious object that constantly surprises us,” said Michael Perse, lead author of the article and director of the Wallace Astrophysical Observatory at the Massachusetts Institute of Technology. “In earlier observations, there were hints that there might be a haze, but there was no solid evidence to confirm that it really existed until data from SOFIA were received. Now we are wondering if Pluto’s atmosphere will collapse in the coming years. – but it may be more stable than we previously thought.

SOFIA studied Pluto just two weeks before the New Horizons mission in July 2015. A modified Boeing 747 flew over the Pacific Ocean and directed its nearly 2.7-meter telescope to Pluto during an eclipse when Pluto cast a faint shadow on the surface of the Earth as it passed in front of a distant star.

SOFIA observed the middle layers of Pluto’s atmosphere at infrared and visible wavelengths, and shortly thereafter, the New Horizons spacecraft examined its upper and lower layers using radio waves and ultraviolet radiation. These combined observations made so close in time gave the most complete picture of Pluto’s atmosphere.

Blue foggy atmosphere

The atmosphere of Pluto, created by the evaporation of surface ice under the distant light of the Sun, is predominantly nitrogen, along with a small amount of methane and carbon monoxide. Particles of fog form high in the atmosphere, more than 30 kilometers above the surface, as methane and other gases react to sunlight and then slowly settle to the icy surface.

The New Horizons mission found evidence of the presence of these particles when it sent back images showing a bluish haze in Pluto’s atmosphere. Now, data from SOFIA supplement this detailed information by finding that the particles are extremely small, have a thickness of only 0.06-0.10 microns, or about 1000 times less than the width of a human hair. Due to their small size, they scatter blue light more than other colors when they drift to the surface, creating a blue tint.

Thanks to these new discoveries, scientists are revising their predictions about the fate of Pluto’s atmosphere. Many predictions indicated that as the dwarf planets move away from the Sun, less surface ice will evaporate – creating less atmospheric gases, while losses in space continue – which will ultimately lead to atmospheric collapse. But instead of collapsing, the atmosphere seems to change in a shorter cyclic pattern.

Using what scientists learned from SOFIA to reanalyze previous observations, including from SOFIA’s predecessor, Kuiper Aerial Observatory, it shows that the haze thickens and then disappears in a cycle that lasts only a few years. This indicates that tiny particles are created relatively quickly. Researchers suggest that Pluto’s unusual orbit leads to changes in the haze and, therefore, may be more important in regulating its atmosphere than the distance from the Sun.

Pluto moves around the Sun in a long orbit of an oval shape, called an elliptical orbit, and at an angle. This leads to the fact that some areas of the dwarf planet are more exposed to sunlight at different points in its orbit. When ice-rich areas are exposed to sunlight, the atmosphere can expand and create more particles of fog, but as these areas begin to receive less sunlight, it can shrink and become more transparent. This cycle continued even when Pluto’s distance from the Sun increases, although it is unclear whether this picture will continue.

“We still do not understand much, but now we are forced to reconsider earlier forecasts,” said Pers. “The atmosphere of Pluto may decay more slowly than previously thought, or maybe not decay at all. We must continue to follow this to find out. ”

In pursuit of the shadow of Pluto,

SOFIA had a unique position to study Pluto from afar, taking advantage of the rare moment when Pluto passed in front of a distant star, casting a faint shadow on the surface of the Earth. Pluto’s atmosphere was momentarily illuminated by this star.

It was expected that the shadow of Pluto would move at a speed of 85,000 km per hour for a short two minutes over the Pacific Ocean near New Zealand. SOFIA set the course for interception, but two hours before the eclipse, updated data moved the shadow 320 kilometers to the north.

“It took a little effort to capture this shadow. SOFIA has the advantage of being mobile, but the revised flight plan had to be verified with the air traffic control system, ”said William Rich, SOFIA Deputy Director of Operations. “There were some tense moments, but the team worked together, and we got permission. “We reached the shadow of Pluto just at the right time and were very happy to do it!”

The agreement between the data collected remotely by SOFIA and the New Horizons near-span confirms that observations of eclipses from Earth can provide the same high-quality data as from spacecraft.

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