On July 15, 2015 the NASA “New Horizon” probe did a close flyby with much data recorded that will be sent for the 5.5-hour journey back to earth for analysis and distribution. The distance is so great that all information must be sent slowly using the available power in its radio-actively heated thermal power generation system. Thus we should expect new data announcements for at least the rest of 2015. Listen to the signal acquisition of the New Horizons spacecraft as others report to “Mom” Alice Bowman.
Pluto was discovered Feb 18, 1930 by blinking between photographic plates (pictures) taken years apart. This technique makes changes between the pictures stand out visually from the much more constant stellar background features.
Pluto was named by an 11 year old girl, Venetia Burney Phair. “I was fairly familiar with Greek and Roman legends from various children’s books that I had read,” she said in the interview. “And of course I did know about the solar system and the names the other planets have. And so I suppose I just thought that this was a name that hadn’t been used.”
Pluto has a 248 year orbit, so it moves against the stellar background each year by 360/248 degree (about 3 moon diameters). At that distance, Pluto’s apparent movement, as the earth zips from one side of its orbit to the other, produces an angular movement of 186 million mi/4000 million mi or .0465 radians or 2.66 degrees or 5 apparent moon diameters. This half-yearly variation in position is how Pluto’s distance from earth was first calculated. Pluto’s position appears to wobble back and forth as it slowly progresses around its elliptical (egg shaped) orbit.
In fact Pluto’s orbit is so elliptical that it was actually closer to the sun than Neptune between February 1979 and February 1999,. It’s distance from the sun varies from 30 AU to 49 AU (average earth-Sun distance) as it orbits. In 2014 it was at 32.6 AU.
Pluto has five moons, the largest Charon is about half of Pluto’s diameter.
Charon, like our moon, is gravitationally locked to Pluto’s rotation due to tidal energy losses slowing both Pluto’s and Charon’s rotation. An unchanging face of Charon is always visible from any fixed place on Pluto as they rotate around each other with a “day” of 6.39 earth days.
A picture taken by New Horizon on 7/9/2015 as New Horizon was approaching Pluto from ~1 million miles shows very unusual contrasting and complex patterns. New images of Pluto appear almost daily on the NASA New Horizon site.
It has methane ice (natural gas for heating for us) and ammonia ice on the side
Pluto even has another loosely bound satellite sharing its orbit that it may share orbits with for another 250,000 earth Yrs. There is a miniscule atmosphere with a pressure 100,000 to a million lower than here on earth that is starting to freeze out as the orbit takes it further away. During it’s “cold season” Pluto receives about 1/3 of the peak solar energy at closest approach.
Pluto rotates slowly with each of its days taking 6.39 earth days.
It’s polar rotational axis is at 120 degrees (60 deg from it’s the axis of solar orbit) so seasons are extreme. Earths rotational axis has only a 23.44 degree tilt from it’s orbital axis.
by Neil deGrasse Tyson
When the Rose Center for Earth and Space at the American Museum of Natural History reclassified Pluto as an icy comet, the New York Times proclaimed on page one, “Pluto Not a Planet? Only in New York.” Immediately, the public, professionals, and press were choosing sides over Pluto’s planethood. Pluto is entrenched in our cultural and emotional view of the cosmos, and Neil deGrasse Tyson, award-winning author and director of the Rose Center, is on a quest to discover why. He stood at the heart of the controversy over Pluto’s demotion, and consequently Plutophiles have freely shared their opinions with him, including endless hate mail from third-graders. With his inimitable wit, Tyson delivers a minihistory of planets, describes the oversized characters of the people who study them, and recounts how America’s favorite planet was ousted from the cosmic hub. Color illustrations
A radian is the angle of the length the radius of a circle wrapped around it’s circumference
Since the circumference of a circle is defined as the number pie times it’s diameter, a radian is 360 degrees/(2*pi) or 57.2958…. degrees. (The moon averages 2160/238,567 or 0.51 degrees or 31 minutes of arc.)
Due to the extreme rotational axis tilt, Pluto’s 248-year seasons are both long and extreme so there is much freezing of the N2 (Nitrogen gas), CO (Carbon monoxide), and CH4 (Methane) ices that comprise its atmosphere around the pole away from the sun (only 30 deg from pole orientation to the sun).
by Philip Morrison
A wonderful reference showing orders of magnitude for all ages is the book “Powers of Ten” by Philip Morrison, a delightful Physics Professor.Illustrations depict the Solar System in comprehensible scale.