SAYING ‘GOODBYE’ TO VOYAGER 1 & 2 | THE WEEK NASA uses modern technology in the fight to keep our dying spacecraft alive. November NoCoAstro was the first planet located by mathematical predictions instead of Neptune was the first direct observations of the sky.direct observations Questions, comments, submissions, photos or just to say ‘hello’: OUR JOURNEYCONTINUES ObjView ObjView at NoCoAstro dot org CONTACT Amanda Bell EDITOR How you discoverdo a planet, anyway

? November NoCoAstro.org pm pm , 7:30 , , 7pm 7pm , , 7pm , * more details online at: online at: details *more Fossil Creek ReservoirCreek Fossil Fossil Creek ReservoirCreek Fossil Learning Ctre Poudre : Fort MuseumofDiscovery Collins : : ’s Aurora and Radiation Belts: AuroraEarth’s Belts: Radiation and : : Thursday December 1st, 6:15pm Thursday1st, December : Date Speaker Location NOCOASTRO MEETING NOCOASTRO OUTREACH* 3rd & 17th, Saturday &17th, 3rd Wednesday 7th, Friday 30th, Just stop by the Fort Collins Museum of Discovery. Discovery. oftheFort Museum Collins by stop Just

Exploration on the Edge of Space with Dr. David Malaspina David ExplorationDr. with ofSpace Edge onthe

DID YOU KNOW…? All meetings are FREE & open to the public! toopenthepublic! & FREE meetingsAll are KNOW…? YOU DID DECEMBER DECEMBER T RUE BLUE ORIGIN OF NAME: Discovered 23 September 1846, Neptune was named after the Roman god of the sea (which equates to the Greek god of the sea, Poseidon). : A few weeks after Neptune’s discovery, astronomers began to notice (s). Only - the largest & only spherical moon - could be observed by technology at the time. Later, mid-20th century improvements in ground-based telescopes and space probes allowed discovery of Neptune’s 13 (maybe 14) satellites, all named for minor Greek water deities. ATMOSPHERE: Even though Neptune is the farthest planet from the sun (and so receives the least energy from the sun), Neptune’s weather patterns are driven by the strongest sustained winds in the — recorded at over 1,200 mph (or 2,000 km/hr). Earth’s most powerful storms reach only 250 mph! During Voyager 2’s visit in 1989, the ‘Great Dark Spot’, a storm large enough to contain the entire Earth, was seen moving at an incredible 750 miles per hour. You will probably not be surprised to hear that, as an ice giant, Neptune’s atmosphere is composed mostly of hydrogen, helium and methane. Like , Neptune is visibly blue because of the methane in its atmosphere. MAGNETOSPHERE: Neptune’s magnetic field is tilted about 47 degrees off the planet’s rotation axis. Like Uranus, with an equally off-balance magnetic field and axis of planetary rotation, Neptune’s magnetosphere experiences wild variations. At an amazing 25x Earth’s magnetic field strength, it is believed to originate in an ionized convecting fluid-ice mantle. SIZE: SURFACE AREA: over 2.9 billion square miles [14.98x Earth SA]. EQUATORIAL CIRCUMFERENCE: ~96k miles [3.86x Earth]. VOLUME: 6.25 x 10^13 km cubed [almost 58x Earth volume]. MASS: 1.02 x 10^26 kg [17.15x Earth mass]. MEAN DENSITY: 1.638 g/cm cubed [almost 30% Earth density]. Neptune, as expected, is much larger than earth but also much less dense. November NoCoAstro RINGS: It wasn't until the mid 1980s and the Voyager 2 mission — around 140 years after astronomers discovered Neptune — that scientists discovered Neptune had rings! Neptune GRAVITY: Neptune, though much larger than Earth, has a surface gravity of only 11.15 m/s Rules: squared [that's just 1.14x Earth’s surface gravity of 9.807 m/s squared or 1 g]. Do you know why? Which Kuiper Belt DISTANCE FROM SUN: Neptune has an almost perfectly circular orbit approximately objects are under 30 AU or roughly 30x Earth distance from sun of 1 AU. Traveling at just 0.182x Earth’s orbital speed, its influence? Neptune orbits the sun once for every 164.79 Earth orbits. Neptune’s weirdly-circular orbit means that other celestial bodies with far more eccentric orbits may actually cross Neptune’s path! Such is the case for , whose distance from the sun is generally greater than Neptune; however, for about 20 years of Neptune’s 164.79 year orbit, Pluto is actually nearer to the sun than Neptune! ROTATION: Neptune is rotating on its axis quickly, once every 16.11 Earth hours. [this is 0.67x Earth rotation]. EQUATORIAL INCLINATION: With an inclination very similar to Earth’s of 28.3 degrees, Neptune experiences similar seasonal variations in a response to variations in sunlight — yes, even at this distance! You learned last month that ’s seasons last about 7 years each. On Neptune, where one orbit around the sun requires nearly 165 Earth years, seasons actuall last about 40 years! PLANETARY : Two common astronomical used are & , which can vary widely for any celestial body. Neptune’s bond albedo of 0.29, which includes all possible scattered light from Neptune, is the lowest of the solar system’s giant planets. TEMPERATURE VARIATION: The wild & windy atmosphere of Neptune receives 1/2 the solar radiation of

Uranus and 1/1000th as much as Earth but isn’t actually the coldest planet in the solar system. Neptune averages -353 degrees November F or -214 degrees C [compare to Earth’s average temperature of 59 degrees F or 15 degrees C]! MISSIONS TO NEPTUNE: VOYAGER 2: In 1989, Voyager 2 became the first (and so far only) spacecraft to visit Neptune. This was also “the last picture show” of the Voyager mission’s tour of the solar system. NoCoAstro W HAT IS AN ICE C RYPTIC T RITON: C ONCEALED G IANT, ANYWAY? Triton: E XTRAORDINARY Short answer: it’s complicated. • is Neptune’s only moon containing C OMPOUNDS: enough mass to become spheroidal We classify ice giants separately from in shape. What surprises are Neptune & the gas giants because their Uranus hiding? composition is dominated by ice rather • is the only large moon in the solar than gas. system with a retrograde orbit At the high pressures typical inside (meaning it was captured instead of giant planets, exotic molecular and Sounds simple enough, doesn’t it? Don’t formed around Neptune!) polymeric compounds are formed. be fooled. • is the only moon in the solar Several substances, ‘forbidden’ in system with clouds and a planet-like classical chemistry’, may be stable at atmosphere! high pressures. These include previously-unknown variants of salt and • is extremely cold (-391 degrees F) even new oxides of magnesium, silicon yet has geysers spewing icy material and aluminum! 5-miles from its surface! • will one day reach the Roche Limit around Neptune, tearing itself apart.

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Did it justget over 30 gravitationally- Moving beyond our solar Moving beyond How do we know it’s there & How do we edition of this newsletter? edition of What can you look forward to in your next & final next to in your look forward can you What more crowded in here? system, every dream! Trekkies GROUP: THE LOCAL bound galaxies. UNIVERSE: OBSERVABLE bodies. PLANET NINE: is it? what exactly : KUIPER BELT: Disc-shaped r Disc-shaped BELT: KUIPER of icy of thousands hundreds (probably) EXTRA! EXTRA! IT! ABOUT ALL READ November NoCoAstro Paul Fleming: web-edit at NoCoAstro dot org web-edit Paul Fleming: Amanda Bell: ObjView at NoCoAstro dot org Trevor presMoriarty: at NoCoAstro dot org TREASURER &OUTREACH Greg Halac: treas at NoCoAstro dot org Bob Michael: vp at NoCoAstro dot org Dave Karp: sec at NoCoAstro dot org NEWSLETTER EDITOR VICE PRESIDENT SECRETARY PRESIDENT






“We each want to be the one to find it.” Scott Sheppard, Carnegie Institution for Science November January

PLANET NINE IS PLAYING HIDE & SEEK | AAAS Objects beyond Neptune provide fresh evidence for Planet Nine. JOIN US!


SEE YOU ONLINE! November NoCoAstro