[Vision2020] Don't Worry Kids, Pluto Still A Planet!
Tbertruss at aol.com
Tbertruss at aol.com
Wed Oct 5 13:10:46 PDT 2005
Jerry, et. al.
Jerry wrote on 10/3/05:
While the 10th planet, which actually should be the 9th since Pluto was
downgraded, may not have been officially named, it is being referred to as Xena by
the astronomical community, and it’s moon is being referred to as Gabrielle.
----------------------------
Pluto has not been "downgraded." You can call it whatever you want, but the
so called "official" body, the International Astronomy Association, that makes
so called "official" decisions about naming planets as "planets," released an
"official" clarification regarding this mistaken reporting on this issue:
http://www.iau.org/IAU/FAQ/PlutoPR.html
The IAU regrets that inaccurate reports appear to have caused widespread
public concern, and issues the following corrections and clarifications:
1. No proposal to change the status of Pluto as the ninth planet in the
solar system has been made by any Division, Commission or Working Group of the
IAU responsible for solar system science. Accordingly, no such initiative has
been considered by the Officers or Executive Committee, who set the policy of
the IAU itself.
-----------------------------------
And now, to celebrate the survival so far of one of my childhood "myths"
regarding Pluto as the ninth and farthest most planet from our sun (actually, only
part of the time, because Pluto sometimes slips inside the orbit of Neptune,
as you can read in the data below), a myth taught by my teachers as though it
was the last word on the subject, like a lot of other nonsense I was taught, a
myth that may be shattered in part when or if another more remote solar
system object is given planet status, here is information about Pluto that no doubt
everyone will memorize down to the last detail, including the astonishing
revelation that some of this data was discovered by Clyde Tombaugh, 18 Feb.,
1930, and, more seriously, the fact that Pluto does have a moon, Charon, when once
we were taught Pluto had no moons:
http://nssdc.gsfc.nasa.gov/planetary/factsheet/plutofact.html
Pluto/Earth Comparison
Bulk parameters
Pluto Earth Ratio
(Pluto/Earth)
Mass (1024 kg) 0.0125 5.9736 0.0021
Volume (1010 km3) 0.715 108.321 0.0066
Equatorial radius (km) 1195 6378.1 0.187
Polar radius (km) 1195 6356.8 0.188
Volumetric mean radius (km) 1195 6371.0 0.188
Ellipticity (Flattening) 0.0000 0.00335 0.0
Mean density (kg/m3) 1750 5515 0.317
Surface gravity (m/s2) 0.58 9.80 0.059
Surface acceleration (m/s2) 0.58 9.78 0.059
Escape velocity (km/s) 1.2 11.19 0.107
GM (x 106 km3/s2) 0.00083 0.3986 0.0021
Bond albedo 0.4 - 0.6 0.306 1.3 - 2.0
Visual geometric albedo 0.5 - 0.7 0.367 1.4 - 1.9
Visual magnitude V(1,0) -1.0 -3.86 -
Solar irradiance (W/m2) 0.89 1367.6 0.0007
Black-body temperature (K) ~37.5 254.3 0.147
Number of natural satellites 1 1
Planetary ring system No No
Orbital parameters
Pluto Earth Ratio
(Pluto/Earth)
Semimajor axis (106 km) 5906.38 149.60 39.482
Sidereal orbit period (days) 90,465 365.256 247.68
Tropical orbit period (days) 90,588 365.242 248.02
Perihelion (106 km) 4436.82 147.09 30.164
Aphelion (106 km) 7375.93 152.10 48.494
Synodic period (days) 366.73 - -
Mean orbital velocity (km/s) 4.72 29.78 0.158
Max. orbital velocity (km/s) 6.10 30.29 0.201
Min. orbital velocity (km/s) 3.71 29.29 0.127
Orbit inclination (deg) 17.16 0.000 -
Orbit eccentricity 0.2488 0.0167 14.899
Sidereal rotation period (hrs) -153.2928 23.9345 6.405
Length of day (hrs) 153.2820 24.0000 6.387
Obliquity to orbit (deg) 122.53 23.45 (2.451)
Pluto Observational Parameters
Discoverer: Clyde Tombaugh
Discovery Date: 18 February 1930
Distance from Earth
Minimum (106 km) 4284.7
Maximum (106 km) 7528.0
Apparent diameter from Earth
Maximum (seconds of arc) 0.11
Minimum (seconds of arc) 0.06
Mean values at opposition from Earth
Distance from Earth (106 km) 5750.54
Apparent diameter (seconds of arc) 0.08
Apparent visual magnitude 15.1
Maximum apparent visual magnitude 13.65
Pluto Mean Orbital Elements (J2000)
Semimajor axis (AU) 39.48168677
Orbital eccentricity 0.24880766
Orbital inclination (deg) 17.14175
Longitude of ascending node (deg) 110.30347
Longitude of perihelion (deg) 224.06676
Mean longitude (deg) 238.92881
On 11 February 1999 at 11:22 UT (6:22 a.m. EST), Pluto passed Neptune as the
furthest planet from the Sun once again and will remain so until 5 April
2231.
North Pole of Rotation
Right Ascension: 313.02
Declination : 9.09
Reference Date : 12:00 UT 1 Jan 2000 (JD 2451545.0)
Pluto Atmosphere
Surface Pressure: ~3 microbar
Average temperature: ~50 K (-223 C)
Scale height: ~60 km
Mean molecular weight: ~16-25 g/mole
Atmospheric composition: Methane (CH4), Nitrogen (N2)
Charon
Mean distance from Pluto (km) 19,600
Sidereal orbit period (days) 6.38725
Sidereal rotation period (days) 6.38725
Orbital inclination to Pluto (deg) 0.0
Orbital eccentricity 0.0
Equatorial radius (km) 593
Mass (1021 kg) 1.62
Mean density (kg/m3) 1850
Surface gravity (m/s2) 0.31
Escape velocity (km/s) 0.60
Geometric albedo 0.38
Apparent visual magnitude 16.8
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Vision2020 Post by Ted Moffett
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