Category Archives: planets

dwarf planets, New Horizons mission, planets, Pluto

The Pluto Firestorm Continues

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The Issue is NOT Just Planetary Status

Artists’ concept of the New Horizons spacecraft as it flies by Pluto in July, 2015. Credit: Johns Hopkins University Applied Physics Laboratory/Southwest Research Institute (JHUAPL/SwRI)

I recently got into a fascinating late-evening computer chat with someone who is really incensed that Pluto is no longer a planet. He seemed pretty upset about it, and although not a planetary scientist, seemed cognizant of the IAU’s role in the supposed “demotion” of Pluto a few years ago. Since we just passed the anniversary of that silly vote that led to all the commotion, and in light of my conversational partner’s concerns about this distant world, I thought it a good time to talk about Pluto again.

Essentially, there are two issues:  the definition of planet (and where Pluto fits) and the IAU vote. People get upset about the second issue without understanding the scientific implications of the first. And, whether or not the IAU voted the way it did, there was and is still a healthy conversation going on in the planetary science community about just how we define solar system objects, particularly planets.

In less than a year, we’ll know more about Pluto than at any other time in human history. The New Horizons spacecraft will have just completed a successful flyby of Pluto, looked at Charon (its companion), and its moons (and maybe will have found a few more!). It will be exciting, and as Alan Stern (PI of the New Horizons mission put it on a recent NASA press conference), ” A year from now, we’ll write the textbooks on Pluto.”

Continue reading The Pluto Firestorm Continues →

dwarf planets, planets, Pluto

Pluto’s New Moon

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A Dwarf Planet with Moons

Pluto has been in the news a lot lately. The New Horizons spacecraft is headed out to swoop past this icy dwarf planet and show us what it really looks like.  That will happen in July 2015 — just three years from now.  In the meantime, the Hubble Space Telescope keeps checking out this distant world and finding new moons around it. The HST observations are an ongoing project to make sure that mission planners for New Horizons have a good idea of the known hazards (i.e. things that the spacecraft could hit) as it whizzes past Pluto in a few years.

The dwarf planet Pluto and its five moons. Will HST find more? Courtesy NASA/STScI.

Last week, the HST folks announced the discovery of a fifth moon orbiting Pluto. For now, it’s called P5, and in time, it will get an official name.

Pluto’s moons, with the exception of its largest moon Charon, are pretty small. This newly discovered one is no bigger than 15 miles across.  Now, it’s kind of intriguing that Pluto has so many of its own moons, and scientists are busily figuring out how it could have gained such a following through its history. The current thinking is that these little moons  are debris from a collision between Pluto and another object early in the history of the solar system, and subsequently were swept into Pluto’s orbit.

Collisions ARE an important part of solar system evolution. Earth’s own Moon was most likely formed in the aftermath of a collision between the infant Earth and a Mars-sized object.  And, we still see collisions today: comets collide with planets, asteroids collide, objects in Saturn’s rings collide, and so on. Collisions are a fact of life when you live in a planetary system and people in planetary science are still defining and understanding the role that smashups play in the larger evolution of worlds.

The New Horizons mission is a small spacecraft that proposed to NASA after the Pluto Kuiper Express mission got cancelled by the agency due to lack of funds. New Horizons has moved out beyond the orbit of Uranus, carrying a suite of scientific instruments, including a set of cameras, radio science detectors, plasma and high-energy particle detectors, and a dust counter. It has already sent back data and images  Jupiter and some of its moons, and an asteroid.

Once the mission gets to Pluto, it will fly quite close to this frozen world and take massive amounts of data about its surface and atmosphere.  After that, the spacecraft heads out to explore more of the Kuiper Belt and relay information about this unexplored frontier of the solar system. Stay tuned!