Solar canines, different celestial results might seem in alien skies

Ice crystals in Earth’s ambiance typically align excellent to create numerous placing visible results, from a halo across the moon, to brilliant spots known as solar canines on both aspect of the solar in a winter sky, or a rainbowed pillar, known as a crown flash, above a storm cloud.

Similar phenomena can seem within the skies over some exoplanets of the “hot Jupiter” selection, a typical kind of gaseous large that at all times orbits near its host star, Cornell astronomers have discovered. On WASP 17b, a scorching Jupiter exoplanet, 10,000 mile per hour winds might align particles in clouds manufactured from quartz and different crystalline mineral aerosols, creating circumstances by which polarizing mud might work together with starlight in the identical manner aligned ice crystals work together with daylight on Earth.

“Just like the alignment of ice crystals in Earth’s atmosphere produces observable phenomena, we can observe the alignment of silicate crystals in hot Jupiter exoplanets,” mentioned Elijah Mullens, M.S. ’24, doctoral pupil in astronomy and co-author of the examine.

“Silicate Sundogs: Probing the Effects of Grain Directionality in Exoplanet Observations” revealed in The Astrophysical Journal Letters on July 21. In the paper, Mullens and co-author Nikole Lewis, affiliate professor of astronomy within the College of Arts and Sciences, suggest that the circumstances are proper on this exoplanet’s ambiance for the wind to align silicate crystals – a course of known as mechanical alignment – creating visible results.

The concept of mechanical alignment was put ahead in 1952 by Cornell astronomy professor Tommy Gold to clarify what aligns mud within the interstellar medium (ISM), Lewis mentioned. Gold proposed that gasoline motion aligned mud particles, as if air have been blowing on them. His mechanical alignment principle has fallen out of favor for ISM mud particles; researchers now say it’s extra doubtless that magnetic fields and radiative torques, the place starlight heats one aspect, make particles align.

“Now we see that the 1952 proposal doesn’t work for the interstellar medium, but it probably works for a hot Jupiter exoplanet, a very hot planetary atmosphere with high-speed winds,” mentioned Lewis, whose experience is in atmospheric dynamics of those exoplanets. “When we started looking at planetary atmospheres, in particular these hot Jupiters, it occurred to me that with 10,000 mile per hour winds zipping around in these very dense atmospheres, surely the grains would align.”

Lewis and Mullens got here up with this concept once they have been each on the staff that used the James Webb Space Telescope (JWST) to discover proof for quartz nanocrystals within the high-altitude clouds of WASP-17 b, a scorching Jupiter exoplanet 1,300 light-years from Earth, reported in 2023.

“We didn’t expect to see quartz crystals in a hot Jupiter atmosphere,” Lewis mentioned. “We were predicting something completely different.”

Quartz crystals are tiny: at 10 nanometers throughout, 10,000 might match side-by-side throughout a human hair. And they’ve an elongated form, like boats, mentioned Mullens. In a wind, the crystals behave like a bunch of boats on a river with a robust present.

“If you put a bunch of these crystals in very strong winds like we expect on hot Jupiters, they’re going to align themselves with the wind like boats in a current,” he mentioned. 

But even when they don’t align horizontally with the wind, as proposed on this paper, Mullens mentioned, the crystals are vulnerable to being organized in a roundabout way – maybe vertically, or with electrical fields, and even randomly – that create visible results from interactions with the sunshine from its star.

Researchers can see these results with JWST, an infrared telescope. They can’t take pictures of WASP 17b as a result of it’s so distant, Lewis mentioned, however “if we were able to take a picture of WASP 17b at optical wavelengths and resolve the disk of the planet, we would see these types of sun dog features.”

Both on Earth and an exoplanet, visible results reveal a lot about what’s happening within the ambiance, mentioned Mullens.

“Other than being pretty, these effects can teach us about how crystals are interacting in the atmosphere. It’s really information-rich, just as on Earth where the atmospheric conditions need to be a certain way for them to be horizontally oriented to produce a sun dog,” he mentioned. “If we see something similar in a hot Jupiter, we can be able to tell something about how the crystals are interacting with local forces.”

Mullens will proceed to check particle directionality on WASP 17b very quickly; he’s principal investigator on a proposal for additional observations of the exoplanet, accepted by JWST for the approaching yr.

Support for this examine got here from a National Science Foundation Graduate Research Fellowship.

Kate Blackwood is a author for the College of Arts and Sciences.