Документ взят из кэша поисковой машины. Адрес оригинального документа : http://www.stsci.edu/~mutchler/talks/Pluto_Odyssey_13march2008.pdf Дата изменения: Fri Mar 14 18:43:36 2008 Дата индексирования: Tue Nov 24 02:51:42 2009 Кодировка: Поисковые слова: moon

Is Pluto a planet?

Historical overview
· Discovery of Pluto and it's "moon" Charon · Discovery of Kuiper Belt and Eris, the 10th planet? · "Great Planet Debates"of 1851, 2006, 2008 · Ceres, Vesta and the Asteroid Belt: dИjЮ vu · Ongoing discovery: Hubble, New Horizons, and Dawn missions

Personal anecdotes
· "Planet X" books · Hubble imaging of Pluto, Ceres, and Vesta · Discovery of Pluto's moons Nix & Hydra · Coming full circle, and "teachable moments" · Semantics: names, classifications · Basketballs and gorillas, imagination and blissful ignorance

Max Mutchler
Space Telescope Science Institute Johns Hopkins University Odyssey Lecture Series "Hubble's Expanding Universe" March 13, 2008

Every journey begins with one small step...

Launch of the Hubble Space Telescope April 24, 1990

Excerpt from The Search for Planet X, by Tony Simon, 1962

No one can say that we have come to the end of discoveries in the Solar System. New tools and methods ­ such as computing machines...and observatories in space outside the Earth's atmosphere, man(kind) will get much better views of the far reaches of the Solar System. Standing on the shoulders of the scientists of centuries past, patient and brilliant astronomers of the future will surely discover more new worlds... and have the fun of debating what to name it.

4th

Grade (1974)

Hubble and the Space Shuttle: launch and servicing missions
Dy sn om ia Er is an d

What is a planet ?

1990 1993 1997 1999 2002 2008 ! ????

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A thousand childhood doodles...

The discovery of Pluto in 1930

Clyde Tombaugh

A comforting, familiar incomplete bedtime story

Blink-comparator that Tombaugh used to compare two images, and discover Pluto by it's motion

Pluto discovery images

Pluto discovery images

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The slowly emerging picture of Pluto

IS PLUTO...
The discovery of Pluto's moon Charon in 1978

James Christy & Robert Harrington U.S. Naval Observatory Washington, D.C.

Hubble images reveal two new moons of Pluto

Pluto moons discovery observations
· Re-live a "eureka moment" with me · ACS W ide Field Channel (W FC) covers entire orbital stability zone · Pluto-Charon near chip gap: peek-a-boo! · 4 long exposures on May 15 and again on May 18, 2005 · Discovery on June 15, 2005: try it yourself...

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15 May 2005, frame 1

15 May 2005, frame 2

15 May 2005, frame 3

15 May 2005, frame 4

15 May 2005, sum 4 frames

15 May 2005, median 4 frames

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New moons are roughly 3-4x farther out than Charon, and co-planar with possible 6:4:1 orbital resonances

Hydra (P1)

Charon

Nix (P2)

18 May 2005, median 4 frames

15 and 18 May 2005, median 8 frames

elf: Note to s t -way fligh ancel one sland! c i to remote

Pre-discovery observations in 2002
· Why weren't these moons discovered earlier? · Now knowing exactly where to look: new moons marginally detected · Additional points for orbit determinations

Clean image on 15 Feb 2006

Relative sizes of Pluto, Charon, and new moons (P1 and P2)

Nix Hydra
2300 km 1200 km ~100 km Annette and Patsy Tombaugh

The new moons are roughly 12x smaller and 600x fainter than Charon, and 4000x fainter than Pluto

Jim Christy Jim Christy

New Horizons launch 19 January 2006

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Eris (was "Xena") discovery announced in July 2005

The planet vote of 2006... and the reaction

Forcing the question: is this the 10th planet?

http://www.iau2006.org Draft Resolution 5 for GA-XXVI: Definition of a Planet 16 August 2006 (initial proposal)
(1) A planet is a celestial body that (a) has sufficient mass for its self-gravity to overcome rigid body forces so that it assumes a hydrostatic equilibrium (nearly round) shape1, and (b) is in orbit around a star, and is neither a star nor a satellite of a planet. (2) W e distinguish between the eight classical planets discovered before 1900, which move in nearly circular orbits close to the ecliptic plane, and other planetary objects in orbit around the Sun. All of these other objects are smaller than Mercury. W e recognize that Ceres is a planet by the above scientific definition. For historical reasons, one may choose to distinguish Ceres from the classical planets by referring to it as a "dwarf planet." (3) W e recognize Pluto to be a planet by the above scientific definition, as are one or more recently discovered large Trans-Neptunian Objects. In contrast to the classical planets, these objects typically have highly inclined orbits with large eccentricities and orbital periods in excess of 200 years. W e designate this category of planetary objects, of which Pluto is the prototype, as a new class that we call "plutons". (4) All non-planet objects orbiting the Sun shall be referred to collectively as "Small Solar System Bodies". For two or more objects comprising a multiple object system, the primary object is designated a planet if it independently satisfies the conditions above. A secondary object satisfying these conditions is also designated a planet if the system barycentre resides outside the primary. Secondary objects not satisfying these criteria are "satellites".Under this definition, Pluto's companion Charon is a planet, making PlutoCharon a double planet. If Pallas, Vesta, and/or Hygeia are found to be in hydrostatic equilibrium, they are also planets, and may be referred to as "dwarf planets".

Three different faces of Ceres

High resolution images of Ceres reveal roundness, surface features, and colors

Why does roundness matter ? Three different faces of Ceres

High resolution images of Ceres reveal roundness, surface features, and colors

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Same initial conditions, but different subsequent evolutions Vesta's impact crater, volcanic maria, dry?

Vesta color composites, in phase sequence

Thomas, P. et al., 2005, "Differentiation of the asteroid Ceres as revealed by its shape", Nature Letters, Vol 437 Thomas, P. et al., 1997, "Impact excavation on asteroid 4 Vesta: Hubble Space Telescope results", Science, Vol 277

Hubble WFPC2 images of asteroid Vesta in May 2007: color composite movie

dwarf planet

asteroid
(small solar system body)

Hey, no fair!

with dither / drizzle

with MEM deconvolution

Big collisions in the early Solar System: Earth-Moon formation Pluto and moons Vesta impact: created 50 smaller asteroids, and 20% of meteorites

Vesta was discovered in 1807... why not thousands of years ago?

Vesta Jupiter

"Naked eye" in May 2007

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http://www.iau2006.org Final Resolution for GA-XXVI: Definition of a Planet 24 August 2006
The IAU therefore resolves that planets and other bodies in our Solar System, except satellites, be defined into three distinct categories in the following way: (1) A "planet" is a celestial body that (a) is in orbit around the Sun, (b) has sufficient mass for its self-gravity to overcome rigid body forces so that it assumes a hydrostatic equilibrium (nearly round) shape, and (c) has cleared the neighbourhood around its orbit. (2) A "dwarf planet" is a celestial body that (a) is in orbit around the Sun, (b) has sufficient mass for its self-gravity to overcome rigid body forces so that it assumes a hydrostatic equilibrium (nearly round) shape, (c) has not cleared the neighbourhood around its orbit, and (d) is not a satellite. (3) All other objects, except satellites, orbiting the Sun shall be referred to collectively as "Small Solar System Bodies". Pluto is a "dwarf planet" by the above definition and is recognized as the prototype of a new category of trans-Neptunian objects. For now, Charon is considered just to be Pluto's moon. The idea that Charon might qualify to be called a dwarf planet on its own, may be considered later.

Dysnomia

...and Ceres are "dwarf planets"?
Nix

Y
Eris

Y
Hydra

Y ?

Y

?

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Planet X becomes... just an ex-planet
On Sept. 7, the former 9th planet was assigned the asteroid number 134340 by the Minor Planet Center, the official organization responsible for collecting data about asteroids and comets in our solar system. Pluto's companion satellites, Charon, Nix and Hydra are considered part of the same system and will not be assigned separate asteroid numbers, instead they will be called 134340 I, II and III, respectively. There are currently 136,563 asteroid objects recognized by the MPC; 2,224 new objects were added last week, of which Pluto was the first. Other notable objects to receive asteroid numbers included 2003 UB313, also known as "Xena," and the recently discovered Kuiper Belt objects 2003 EL61 and 2005 FY9. Their asteroid numbers are 136199, 136108 and 136472, respectively.

Citation from IAU Minor Planet Circular 56612 on the naming of

Asteroid "6815 Mutchler"

Asteroid 134340 (alias Pluto)

Historical perspective: how many planets are there?
· Antiquity -- 7 planets in geocentric model (Moon, Mercury, Venus, Sun, Mars, Jupiter, Saturn) · 1550 ­ 6 planets in heliocentric model (add Earth, remove Moon and Sun) · 1781 ­ 7 planets (add Uranus) · 1807 ­ 11 planets (add Ceres, Pallas, Juno, Vesta) · 1845 ­ 12 planets (add Astraea) · 1846 ­ 13 planets (add Neptune) · 1851 ­ 8 planets (too many objects in Asteroid Belt to include them all) · 1930 ­ 9 planets (add Pluto) · 1992 ­ Discovery of 1992 QB1...the Kuiper Belt! · 2005 ­ Discovery of Eris (UB313) · 2006 ­ 8 planets (remove Pluto; don't add Ceres, Charon, Eris or other "dwarf planets")

Ceres and Pluto: The "ugly duckling" problem of being the first of an entire class
Asteroid Belt
Discovered 1801-1851

Kuiper Belt
Discovered in 1992...or 1930?

Ceres

Inferring planets from extra-solar Kuiper Belt's (vice versa): where planetary meets stellar astronomy

inition lanet def e? Will our p Elsewher ork here? w
Dawn mission to Vesta and Ceres Launched September 27, 2007

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Waiting for their spaceships to come in...
Dawn New Horizons
Pluto 2015

Ceres 2015 Vesta 2011

"teachable moments"

What does a "quadruple planet" look like?
http://www.stsci.edu/~mutchler/pluto_50.html

Questions?

Animation produced with

Celestia

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