#OTD 6-22-1978 astronomer James Christy was studying an image of me when he noticed something unusual. At first he thought the blob on my side indicated a defective photographic plate -or worse- an explosion!😱It turned out to be my largest moon #Charon! 🤩

#Charon, discovered #OTD 6-22-1978, has one of the most massive scars in the Solar System! Long ago Charon's subsurface ocean froze & expanded, slowly ripping apart its icy shell and leaving a crack more than 1000 miles long (1600 km).😮#Space

Happy Flyby Anniversary! #OTD 7-14-2015, #NewHorizons flew within 7800mi (12,550km) of the 9th planet's surface! The once unknowable #Pluto, fuzzy cosmic disco ball too distant to be understood, was reborn in the spacecraft's detailed photos of complex & diverse geology.🤩#Space

#NewHorizons is one tough little spacecraft!😅It survived 9.5 yrs of brutal cold & constant vulnerability to #space particles, which could be lethal even at the size of a rice grain. Then, on arrival #OTD 7-14-2015, it had only 9 min. to capture centered pics of its target!#Pluto

#OTD 7-16-2011 Dawn entered the orbit of the asteroid Vesta, making it the 1st spacecraft to orbit an object in the Asteroid Belt! During its year-long orbit, Dawn mapped the super-sized asteroid's geology, finding a rough topography transitional between asteroid & planet🤩#Space

#OTD 8-22-1989 As Voyager 2 was just days away from sweeping past #Neptune, the spacecraft cameras captured a faint, continuous ring encircling the planet. It was the first definitive proof of Neptune's dim but fascinating system of 5 rings.🤩 #Space

#OTD 8-25-1989 Voyager 2 made a close flyby of #Neptune, giving humanity its 1st closeup of the Solar System's 8th planet! At the time, however, Neptune was actually farther from the Sun than I was. This is true for ≈ 8% of my orbit, or 20 yrs out of every 248-yr orbit. 🤩#Space

#OTD 8-25-1989 Voyager 2, after making a close flyby of Neptune, captured mesmerizing images of the 8th planet's largest moon. Active Triton has a lot in common with icy mini planets like me, including a thin atmosphere, similar surface composition, & cryovolcanism.🤩#Space

#OTD 9-5-2012 Dawn leaves Vesta with a host of data on the huge asteroid. The spacecraft revealed Vesta is a complex, layered body with an iron core -- a long-surviving protoplanet/planetary building block like those that coalesced to form rocky planets like Mars & Earth.🤩#Space

#OTD 9-18-2010 Xiangliu, moon of dwarf planet Gonggong (2007 OR10), was discovered! In 2016 astronomers learned Gonggong had an unusually slow rotation. Tidal forces exerted by a satellite could explain this, so they went hunting in archival Hubble images & found Xiangliu🤩#Space

The Windy Planet was discovered #OTD 9-23-1846! #Neptune's winds whip clouds of frozen methane across the planet's surface at 1200mph (2000kph).🌪️😱They're so fast they break the sound barrier! Earth's most powerful winds reach a measly 250mph.😄#Space

#HappyEquinox to Earth! You get to enjoy an equinox every 6 months, but some of us aren't so lucky. The last time the Sun radiated directly on my equator was back in 1988, an event which coincided w/ my closest approach to the Sun. Polar nights that last 124 years are no joke!😅

#NationalDanceDay Neptune's inner moons Naiad & Thalassa perform a beautiful & unique zigzag dance to avoid colliding. They only orbit 1,150mi apart (1850km), but faster Naiad weaves in & out on a perfectly timed path that increases the #space cushion & stabilizes the 2 orbits.🤩

Happy Discovery Day to Neptune's largest🌙Triton, discovered #OTD 10-10-1846! Triton was found 17 days after Neptune, but remained nameless until a 2nd moon, Nereid, was found in 1949. Triton is the only large🌕in our System to orbit in the opposite direction of its planet.#Space

Triton, discovered #OTD 10-10-1846, is one of the few moons on which active eruptions have been observed. In 1989 Voyager 2 observed geyser-like eruptions of nitrogen gas & dust from beneath the surface in plumes up to 5mi (8 km) high.🤩#Space

On #NationalDessertDay, I offer you Cthulhu Macula Chocolate Fudge and Lowell Regio Meringue, chilled to perfection after billions of years in the making. Enjoy! 🤩#Pluto #Space