Is Pluto A Binary Dwarf Planet?

Pluto Binary
Four Tiny Satellites Orbit the Pluto-Charon Binary
Image Credit: NASA / ESA / and M. Showalter (SETI Institute)

With the discovery by the Hubble Space Telescope of a fifth tiny moon orbiting Pluto, interest continues to mount about this peculiar system.

Now, there is a suggestion on that the system is actually a Double Planet with four moons (see the image).

The four tiny moons, all discovered by Hubble in the past seven years, do not orbit Pluto itself. Instead, they orbit the center of mass of the Pluto-Charon system.

Charon is 12% the mass of Pluto, and could well qualify as a Kuiper Belt Object (KBO) and is perhaps a dwarf planet itself.

Ceres is a dwarf planet in the Asteroid belt, with a mass of 0.000 15 that of Earth. Pluto’s mass is 0.002 2 of Earth, which would make Charon’s mass 0.000 27 that of Earth (more than Ceres).


Pluto has Five Moons

Pluto P5
Astronomers Find Fifth Moon Orbiting Pluto
Image Credit: NASA / ESA / M. Showalter

Tweet from Alan Stern of the Southwest Research Institute in Boulder, Colorado:

Just announced: Pluto has some company — We’ve discovered a 5th moon using the Hubble Space Telescope!

New Horizons Crosses 10 AU Mark Toward Pluto

New Horizons Path
New Horizons’ Path Towards Pluto
Image Credit: JHU / APL

The New Horizons mission to Pluto will cross the 10 AU (Astronomical Unit) boundary around 9:55 PM Phoenix time late tonight (10 February) or 0455 UTC on 11 February.

At that time, it will already have traveled 22 AU since its high speed launch on 19 January, 2006. New Horizons is currently clicking off the distance at 34,000 miles per hour (almost 55,000 kilometers per hour), and will encounter Pluto and its moons in July of 2015.

The New Horizon mission objectives include:

  • Map surface composition of Pluto and Charon
  • Characterize geology and morphology (“the look”) of Pluto and Charon
  • Characterize the neutral atmosphere of Pluto and its escape rate
  • Search for an atmosphere around Charon
  • Map surface temperatures on Pluto and Charon
  • Search for rings and additional satellites around Pluto
  • Conduct similar investigations of one or more Kuiper Belt Objects

New Horizon Pluto Postage Stamp

New Horizon
New Horizon Pluto Exploration Stamp
Image Credit: NASA / John Hopkins /Dan Durda.

Plans for the flyby are well under way – and now, so is an effort to petition the U.S. Postal Service to commemorate the historic achievements of New Horizons on a stamp. The mission team launches that petition today, in early 2012, and plans to submit the petitioners’ names and a formal proposal to the U.S. post office knowing it often takes three years or longer for a proposal to result in an actual stamp.

New Horizon Leaves Uranus Behind

New Horizons
Impression of New Horizons Passing Uranus on Course for Pluto
Image Credit: NASA / JHUAPL / SwRI

The New Horizons spacecraft has now passed Uranus on its voyage to Pluto and beyond. NASA’s spacecraft encountered Uranus’ orbit today at 3:00 PM Phoenix time (2200 GMT) while flying 1.8 billion miles (2.9 billion kilometers) from Earth.

Fifty Years of Space Exploration

Eye Candy from National Geographic.

50 Years
50 Years of Space Exploration
Image Credit: National Geographic

Click on the link for an expanded image. Click on the expanded image for a BIG expanded image.

New Horizon on the way to Pluto

New Horizon: Trajectory
New Horizon: Trajectory
Where Is New Horizon?
Credit: NASA, JPL, APL

Pluto, now contentiously classified as a dwarf planet, is member of a class of Kuiper Belt objects that include Eris (the largest – Pluto is second), Ceres, Haumea, and Makemake.

The trouble began in the late 1970’s with the discovery of Chiron, one of the minor planets, a designation made obsolete in 2006 and now referred to as small solar system bodies. There are approximately 200,000 of these objects. They are not sufficiently massive to squeeze themselves into a spherical shape, which is one of the rules for being classified as a dwarf planet (you have to be round).

Pluto has been studied extensively by telescope, but no spacecraft has flown by the planet. The New Horizons spacecraft was launched on a fast track (36,370 miles per hour) toward Pluto on 19 January 2006, using an Atlas V 551 first stage, a Centaur second stage and a STAR 48B solid rocket third stage. Flying at 51,000 miles per hour (about 23 kilometers per second – kps) during a gravity assist from Jupiter on 28 February 2007, New Horizons is expected to arrive at Pluto on 14 July 2015. During its flyby of Pluto and Charon, New Horizons will be traveling at 31,300 miles per hour (14 kps).

New Horizons was designed, built and is operated by the Johns Hopkins University Applied Physics Laboratory (APL) for NASA, and the Jet Propulsion Laboratory (JPL), along with other research organizations.

The New Horizons spacecraft carries seven instruments for the exploration of Pluto and its moon Charon, and the Kuiper Belt objects it expects to encounter:

  • Ralph: Visible and infrared imager/spectrometer; provides color, composition and thermal maps.
  • Alice: Ultraviolet imaging spectrometer; analyzes composition and structure of Pluto’s atmosphere and looks for atmospheres around Charon and Kuiper Belt Objects (KBOs).
  • REX: (Radio Science EXperiment) Measures atmospheric composition and temperature; passive radiometer.
  • LORRI: (Long Range Reconnaissance Imager) telescopic camera; obtains encounter data at long distances, maps Pluto’s farside and provides high resolution geologic data.
  • SWAP: (Solar Wind Around Pluto) Solar wind and plasma spectrometer; measures atmospheric “escape rate” and observes Pluto’s interaction with solar wind.
  • PEPSSI: (Pluto Energetic Particle Spectrometer Science Investigation) Energetic particle spectrometer; measures the composition and density of plasma (ions) escaping from Pluto’s atmosphere.
  • SDC: (Student Dust Counter) Built and operated by students; measures the space dust peppering New Horizons during its voyage across the solar system.
New Horizon Instruments
New Horizon Instruments
Credit: NASA, JPL, APL

Why go to Pluto? Our solar system is composed of three groups of planets: the rocky worlds (Earth, Venus, Mercury and Mars); the gas giants (Jupiter, Saturn, Uranus and Neptune); and the ice dwarfs of the Kuiper Belt (Pluto, Eris, Makemake, Haumea, and Ceres along with 35 or more additional dwarf planets). Indeed there are many more ice dwarfs than major planets in the Solar System.

So far, no spacecraft has explored any of the ice dwarfs in the Kuiper Belt. This gap in our knowledge of the Solar System will begin to filled in by the instruments on board the New Horizons spacecraft:

The ice dwarfs are planetary embryos, whose growth stopped at sizes (200 to 2,000 kilometers across) much smaller than the full-grown planets in the inner solar system and the gas giants region. The ice dwarfs are ancient relics that formed over 4 billion years ago. Because they are literally the bodies out of which the larger planets accumulated, the ice dwarfs have a great deal to teach us about planetary formation.

Trans Neptunian Objects
Trans Neptunian Objects
Credit: NASA, Wikipedia Commons
True Color Image of Pluto
by Eliot Young, Richard Binzel and Keenan Crane

Pluto, Charon, Nix and Hydra
Credit: APL