Äîêóìåíò âçÿò èç êýøà ïîèñêîâîé ìàøèíû. Àäðåñ îðèãèíàëüíîãî äîêóìåíòà : http://www.stsci.edu/~mutchler/talks/Pluto_Irvine.pdf Äàòà èçìåíåíèÿ: Sat Apr 22 00:14:52 2006 Äàòà èíäåêñèðîâàíèÿ: Tue Oct 2 18:27:56 2012 Êîäèðîâêà: Ïîèñêîâûå ñëîâà: moon

The discovery of two new moons of Pluto

Overview
· Some history: Hubble, Pluto · Hubble mission support for New Horizons: discovery of two more Pluto satellites · Confirming and following-up the discovery · Related discoveries...what is a planet? · New Horizons mission launched 19 Jan 2006! · Questions and handouts

Max Mutchler
Space Telescope Science Institute

Irvine Nature Center 20 April 2006

April 24, 1990

Hubble in Earth orbit

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Hubble was designed to be serviced in orbit by astronauts

Space Telescope Science Institute
on the campus of Johns Hopkins University in Baltimore

Hubble servicing missions:

1993 1997 1999 2002 2008?
SM3B astronauts visit the Institute

The discovery of Pluto in 1930, and confirmation

Calibrating, pointing, and drizzling Hubble Servicing Mission 3B in March 2002: ACS installed Clyde Tombaugh Advanced Camera for Surveys (ACS)

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The discovery of Pluto's moon Charon in 1978

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

The slowly emerging picture of Pluto

IS PLUTO...

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Everything we know about Pluto
· 1930 Pluto discovered
· · · · 1955 1965 1973 1976 ; eccentric orbit * rotation period 6.4 days stable 3:2 resonant orbit with Neptune obliquity > 90 deg * methane ice on surface; size constrained

1 Pluto has not given up it's secrets very easily over the first 75 years...

Discovery of the Kuiper Belt in 1992

· 1978 Charon discovered; "binary planet" * · 1980 Occultation reveals Charon radius to be 600 km · 1985 Pluto-Charon mutual events begin

Everything we know about Pluto
· · · · · 1986 1987 1988 1989 1992

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Pluto & Charon radii, albedos, colors Pluto density is 2 g/cm3 Pluto orbit chaotic; atmosphere, polar caps Pluto & Triton similar, structure in atmosphere Nitrogen and CO ice, density disparity

· 1992 Discovery of the Kuiper Belt
· 2001 Binary Kuiper Belt objects (KBOs)

· 2005 Two more moons discovered!

Discovery of two new moons of Pluto

Early Hubble observations of Pluto and Charon in the 1990s

Press release image for new moons: the discovery was surprisingly easy for Hubble with ACS... but not quite as easy as it looks here.

New satellite discovery observations
· Hubble proposal designed by W eaver, Stern, et al., initially rejected, then accepted when STIS died · Advanced Camera for Surveys (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 May 18, 2005, using only 2 orbits · Discovery on June 15: try it yourself...

Notice the star trails, cosmic rays, chip gap...

15 May 2005, frame 1

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Notice the star trails, cosmic rays, chip gap...

Dithering across the chip gap now...see anything?

15 May 2005, frame 2

15 May 2005, frame 3

Dithering across the chip gap now...see anything?

Looking for real objects among all the artifacts...

15 May 2005, frame 4

15 May 2005, sum 4 frames

Looking for real objects among all the artifacts...

Do it again 3 days later...where are the moons?

15 May 2005, median 4 frames

18 May 2005, frame 1

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Do it again 3 days later...where are the moons?

Dither across the gap...where are the moons?

18 May 2005, frame 2

18 May 2005, frame 3

Do it again 3 days later...where are the moons?

"Clean" image

18 May 2005, frame 4

18 May 2005, median 4 frames

"Clean" image

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

S/2005 P 1

Charon

S/2005 P 2

15 May 2005, median 4 frames

15 and 18 May 2005, median 8 frames

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Initial thoughts
· Why is Pluto suddenly going so easy on us ?!? · Well-designed program: long exposure times (but not too long), two epochs...the gap is OK · Two objects! They somewhat validate each other, and assumptions about their similar orbits · Surprised they are so close to Pluto and Charon: expecting any moons to be farther out, but they don't violate dynamical constraints (Stern, 1994) · Could they be something other than moons?

The "checklist" of possible explanations
· · · · · Detector artifacts? Optical "ghosts" or scattered light? Overlapping cosmic rays or star trails? Real, but asteroids? KBO (Plutinos)? New moons of Pluto!

Confirmation and follow-up
· Independent discovery in Aug 2005 by Andrew Steffl · Search other existing data: Hubble, Subaru... · Ground-based attempts to image the new moons in Sep/Oct: Keck, VLT, Gemini (difficult until spring 2006) · Hubble follow-up: Feb 15 and Mar 2, 2006

Pre-discovery observations in 2002
· Hubble program by Buie & Young · ACS High Resolution Channel · Primarily designed to map surface features (albedo) of Pluto and Charon · New moons marginally detected · Further observations will definitively determine orbits, and hopefully confirm these detections: are the satellites where they should be?

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Preliminary assumptions and implications
· Orbits are co-planar with Charon, nearly circular, possibly in stable resonances with each other · No other moons of similar magnitude; a very compact system · Implies there are probably many KBOs with multiple satellites · Moons probably formed primordially with Charon (collision), not later (captured)

Announcement on October 31, 2005

W eaver et al, 2005, IAU Circular 8625

Hubble Pluto Satellite Search Team
reporting the discovery to the New Horizons Science Team on November 2, 2005 at the Kennedy Space Center
Andrew Steffl (SwRI) Marc Buie (Lowell Observatory) Eliot Young (SwRI)

Hal Weaver (JHU/APL)

S. Alan Stern (SwRI)

Leslie Young (SwRI)

John Spencer (SwRI)

Bill Merline (SwRI)

Max Mutchler (STScI)

"The first discovery of the New Horizons mission"

More Hubble observations on 15 Feb 2006: confirmation!

Long V exposures 1,2,3,4 on 15 Feb 2006, sum

Clean drizzled V image on 15 Feb 2006

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2 March 2006 Hubble ACS / HRC V filter clean

2 March 2006 Hubble ACS / HRC B filter clean

Confirming observations

Publication on
February 23, 2006

Mutchler et al., 2006, IAU Circular 8676

Stern et al., 2006, IAU Circular 8686

Weaver et al., 2006, Nature Stern et al., 2006, Nature Steffl et al., Astronomical Journal (submitted)

Confirming observations
· Feb 15 and Mar 2 data, after pre-covery orbital predictions · Moons right where predicted! · Color info (add blue filter): all 3 moons are colorless or gray · Common origin for all 3 moons of Pluto: a giant collision ~4 billion years ago

Common origin of Pluto and all 3 moons: a giant impact ~4 billion years ago

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

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

P1 P2
2300 km 1200 km ~100 km

Animation produced with

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

Naming the new moons...hmmm...

Should we call Pluto a planet?
· I'm neutral. But some things to consider... · Is Pluto just the first of many Kuiper Belt "ice dwarf" planets discovered? · Is larger Xena the 10th planet? · Are slightly smaller Sedna, Quaoar planets? · Ceres was called a planet for ~50 years, then re-classified as an asteroid (a precedent) · Will we have only 8 planets, or hundreds of them? · Is this a problem? Seems like progress to me. · The IAU is working on it...in the meanwhile, it is a harmless and healthy "non-controversy"

"Xena & Gabrielle"
2398 km 1490 miles 2288 km 1422 miles

The 10th planet?
Earth
12,800 km

Moon
3360 km

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New Horizons launch on 19 January 2006!

Launch week, a.k.a...
Dad & Max Bill Nye

Launch parties
Annette and Patsy Tombaugh Jim Christy

David Levy

Hal W eaver signing the Atlas V rocket

"Nerdstock"

Kuiper Belt
2016-2020

Pluto
14 July 2015

Jupiter
28 Feb 2007

Launch
19 Jan 2006

In memory of Clyde W . Tombaugh, the American astronomer who discovered Pluto in 1930, NASA's New Horizons spacecraft carries a small aluminum canister containing some of Tombaugh's cremated remains, donated by his family. These remains will fly past Pluto with New Horizons on July 14, 2015, and then on past Kuiper Belt objects in the succeeding years. The memorial canister, about two inches wide and half-an-inch tall, is attached to the inside, upper deck of the spacecraft. Its inscription reads:

Interned herein are remains of American Clyde W. Tombaugh, discoverer of Pluto and the solar system's "third zone." Adelle and Muron's boy, Patricia's husband, Annette and Alden's father, astronomer, teacher, punster, and friend: Clyde W. Tombaugh (1906-1997)

New Horizons mission

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http://pluto.jhuapl.edu
Pluto-Charon Encounter Geometry Arrival July 14, 2015
Charon-Earth Occultation 14:17:50

P1 ?

P2 ?
Pluto-Earth Occultation 12:49:50 Charon

13:40

12:40

Pluto
0.24°

Charon-Sun Occultation 14:15:41 Pluto-Sun Occultation 12:49:00 · · · · · S/C trajectory time ticks: 10 min Charon orbit time ticks: 12 hr Occultation: center time Position and lighting at Pluto C/A Distance relative to body center

Sun Earth

11:40

Charon C/A 12:12:52 26,937 km 13.87 km/s

Pluto C/A 11:59:00 11,095 km 13.77 km/s

Questions?

Where is New Horizons right now?
... AND TWO LITTLE MOONS ! http://pluto.jhuapl.edu http://www.stsci.edu/~mutchler

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