Neptune's Mystery Moon, an Exoplanet's Gemstone Clouds, and the Science of Northern Lights

One-liner: Short Wave host Regina Barber's monthly space roundup, "Spacing Out with Gina," with science correspondent Katia Riddle and All Things Considered host Scott Detrow, covers three stories: new research suggesting Neptune's odd moon Nereid formed in place rather than being captured, after another moon shoved it into a lopsided orbit; a hot Jupiter-like exoplanet, WASP-94 A b, whose permanent day and night sides drive fast winds and clouds made of dust and rock; and the space weather behind the Northern Lights, including the legendary 1859 storm.

Neptune's Nereid: Native-Born Moon, Bullied Into a Weird Orbit

Key findings: Neptune has 16 moons, and one of them — Nereid — has puzzled researchers for decades: did it form in Neptune's orbit, or was it captured from elsewhere? Nereid's orbit is stretched into a highly eccentric oval, unlike the regular circular paths typical of moons that formed in place, which for years fueled the capture theory. New research, though, examined Nereid's composition more closely and found it's more consistent with a moon that formed around Neptune. As for that odd orbit shape: the current explanation is that another moon, Triton — about eight times bigger than Nereid — shoved it there earlier in the solar system's history. As Riddle put it, Triton "is kind of a bully." The study is led by Matthew Belyakov of Caltech and published in the journal Science Advances. Belyakov calls Nereid "a time capsule," possibly the only intact survivor of Neptune's original moons: "It's pretty important to understand how the early solar system transpired because that tells us something about our formation here on Earth."

Science background: The breakthrough hinges on the James Webb Space Telescope. Riddle relays that for researchers in this field, it's "really like before the James Webb Space Telescope and after the telescope" — JWST lets astronomers examine the composition of distant solar-system bodies directly, instead of relying on orbital shape alone to guess their origin.

WASP-94 A b: Permanent Day, Permanent Night, and Clouds Made of Gemstones

Key findings: Barber talked to University of Chicago astronomer Eliza Kempton about a new study she wasn't involved in but was excited about — one looking at weather on a planet orbiting another star: "We can see things like storms in Jupiter. But planets orbiting other stars, what's their weather like?" The planet in question is a hot gas giant 18 times closer to its star than Earth is to the sun, and it's tidally locked, so it has a permanent day side and a permanent night side; its star sits about 700 light-years from Earth. Astrophysicists at Johns Hopkins University used the James Webb Space Telescope to study the atmosphere of this planet, called WASP-94 A b: the boundary between day and night is riddled with clouds, but those clouds burn off along the sunlit day side, leaving clear skies there. Lead author Sagnick Mukherjee, whose paper appears in the journal Science, explains that the day-night split creates "this huge temperature difference. What it does is it sets off really fast winds." And the clouds aren't made of water like Earth's — University of Chicago astrophysicist Maria Steinrueck, who also wasn't involved in the study, says her favorite part of research like this is that "these planets are so hot, the gemstones are clouds" — the clouds are made of dust and bits of rock.

Science background: Hot Jupiters are gas giants that orbit extremely close to their star; tidal locking freezes them into permanent day and night hemispheres, and the resulting temperature extremes drive ferocious winds and let rock and dust condense into clouds the way water vapor does on Earth.

Northern Lights and Space Weather: From Alaska to the Storm of 1859

Key findings: The sun runs through activity cycles, and this year and last, strong auroras lit up many U.S. states. A big solar storm last fall reportedly let people see the Northern Lights as far south as Atlanta. The general rule: the bigger the solar storm, the farther south the aurora reaches. Barber's favorite space fact: a massive solar storm in 1859 pushed the Northern Lights as far south as Cuba, and it was so bright that campers thought the sun was rising in the middle of the night. NOAA and NASA haven't tracked anything close to that scale recently — every storm they've logged lately has been smaller. For now, people living along the US-Canada border have the best odds of seeing the aurora, and NOAA's website offers predictions on when and where to look.

Science background: The Northern Lights come from solar storms — "space weather" — interacting with Earth's magnetic field; the stronger the storm, the more charged particles reach the upper atmosphere at lower latitudes, which is why the 1859 storm pushed visible auroras as far south as Cuba.

Rich Details & Trivia

• Barber opens by promising Riddle "a secret handshake by the end of the day"; Riddle plays along ("I'm ready. I'm ready for it.") and the bit pays off at the very end of the episode.
• Riddle jokes that Pluto has "since been kicked out of the major planet guild." Detrow recites his dated mnemonic for memorizing the planets, Pluto included — "My very educated mother just served us nine pizzas" — and admits he needs to update it to "nothing" or "noodles" now that Pluto's gone, though he hasn't settled on which.
• The trio compares Northern Lights sightings: Detrow's never seen them despite getting his hopes up during recent active years (before remembering he lives in a city); Riddle says the same; Barber thinks she saw a "foggy green" once but can't confirm it — so they joke about all flying to Alaska together and taking the show on the road.
• Riddle rates the segment "five out of five stars. I'm game to nerd out any time on space stuff, guys."
• Credits: produced by Aru Nair and Kai McNamee; edited by Christopher Intagliata, Amina Khan, and showrunner Rebecca Ramirez; fact-checked by Riddle, Barber, and Tyler Jones; audio engineering by Jimmy Keeley and Ted Mebane.

Cross-Domain Connections

All three stories here come out of academic and government science — Caltech, Johns Hopkins University, the University of Chicago, NASA, NOAA — with no commercial companies or supply chains in sight, so there's no real link to the acquired business-history domain. Within science, this episode doesn't share real subject matter with the other space roundup, shortwave-moon-robots: that episode's closing joke about a group trip to Iceland to chase the Northern Lights is just a punchline, not the substantive space-weather reporting this episode actually does. The two episodes also lean on different space telescopes — this one uses James Webb, while shortwave-insect-population's quasar story used Euclid — parallel "space telescope makes a discovery" narratives, but no shared object or finding, so no forced link.

Pages to Build

• james-webb-space-telescope — both stories in this episode (Nereid's composition, WASP-94 A b's atmosphere) rely on the James Webb Space Telescope; the Tier 0 archive already holds several older episodes covering its launch and early results (2021-2022), so it's worth consolidating into a standalone concept page.
• hot-jupiter — the "hot Jupiter" class of exoplanet (extremely close orbit, tidal locking, extreme day-night temperature swings) is the core background for WASP-94 A b's weather story and is likely to recur in future exoplanet coverage.

Source · shortwave