Tuesday, July 7, 2009
Laurel Kornfeld's Planets: Adventures in Studying Astronomy
Okay, I admit it. I ripped off the title of this entry, or at least its style, from Mike Brown’s blog.
One of the most frequent questions I am asked when I advocate Pluto’s reinstatement as a planet is, what difference does this make in my life or in anyone else’s life? In many entries, I have discussed the disservice being done to children and to those of all ages studying astronomy who are being taught about only eight planets in our solar system or are, as Dr. Mark Sykes reported, wrongly being told that Pluto is an asteroid.
Most people upset by the 2006 IAU decision expressed their displeasure and moved on to other concerns. I may be wrong, but my guess is very few felt motivated to make major changes in their lives, such as going back to school and studying astronomy with the goal of learning as much as possible about the subject in order to best advocate the decision be overturned.
But that is exactly what I did. I have always had many interests and activities, all of which I love, and all of which compete for my attention. Astronomy was not at the top of the list in August 2006. All of that changed when the IAU issued its infamous ruling. I knew, felt as strongly as possible, that this decision was wrong. And I set about doing whatever I could to counter it, which started with educating myself on the details of planetary science.
I knew then that arguments such as “Pluto should stay a planet because it has always been one” or “because that is how I was raised,” or because “the mnemonic won’t work without Pluto” were not scientifically valid. If a case were to be made for Pluto retaining its planet status, that case must be built on logical arguments stemming from a solid foundation of scientific knowledge.
After reading more web sites about the solar system than I can count, I joined an astronomy club and took a class for volunteers who become qualified observers on open public nights. I spent a lot of time at weekly meetings listening to lectures on every aspect of astronomy. Then I took an un-graded online course offered by Swinburne University, based in Melbourne, Australia, titled “From Planets to the Universe.” That six-week course offered interaction with students worldwide discussing a lot of material in a very short time.
The benefits of online education are that students from very different backgrounds have the opportunity to learn from one another, to exchange differing perspectives, to throw around ideas and bounce them off one another. I enjoyed this to the point that I applied to Swinburne Astronomy Online’s Graduate Certificate program and was accepted.
Unlike the other courses, the courses in this program are graded. And here I was, with no real math or science background, in a course with high school teachers of chemistry and physics and people who had actually worked professionally in planetariums and observatories. The course title was “Exploring the Solar System.” And the instructor as well as the program director are members of the IAU! Thankfully, they were always fair and never used my online criticism of the IAU against me academically.
There is no way to summarize everything learned in a 12-week semester, but suffice it to say that our exploration of the solar system was comprehensive and detailed. This is not the solar system many of us learned in grade school, which was mainly a list of nine objects revolving around the Sun. This was an in-depth look at a solar system far more diverse, hosting a multitude of different objects, no two of which are exactly alike.
Some supporters of Pluto’s demotion argue that Pluto unfairly gets more attention than the larger moons of the gas giant planets because it is deemed a planet, and they are not. That certainly was not the case in this class. At one time, we knew little about the planets themselves and even less about their moons. Today, 40 plus years of robotic explorations have given us so much data about these moons, which really should be classified as secondary planets, that classes like the one I took spend an entire two-week period just on the moons and rings of the jovian planets. We do not have to choose between Pluto and these other, fascinating worlds. We can teach and study both.
One important lesson from studying the planets is that the robotic missions have given us much of our current knowledge of the solar system, knowledge that dispelled many previously held notions. Only 50 years ago, many believed Venus hosted lush vegetation and that Mars may host intelligent life. Now we know that although it is sometimes called Earth’s “sister planet,” Venus’ heavy atmosphere of sulfur dioxide and its high temperature and pressure make it impossible for any life to exist on that planet. We have explored Mars from orbit and on the ground and now know that its tenuous atmosphere and lack of a magnetic field preclude anything other than microbial life.
We have learned that while the four jovian planets used to be lumped into one group, “gas giants,” Uranus and Neptune are actually different enough from Jupiter and Saturn to merit being placed in a separate category, the ice giants. While Jupiter and Saturn are composed mostly of hydrogen and helium, the two outermost jovians, Uranus and Neptune, are made up of hydrogen compounds such as methane, ammonia, and water plus small amounts of hydrogen, helium, and rock. Uranus and Neptune are believed to have liquid cores just as Jupiter and Saturn do, but their densities are akin to those of ices, likely a mixture of water, methane, and ammonia.
Mercury is now recognized as having a tenuous magnetic field and a very thin atmosphere, facts that contradict long-held views among astronomers that it had neither. The moons of the jovian planets are believed to have formed with those planets from the solar nebula, unlike Earth’s moon, which most scientists view as having been formed from a giant impact by a Mars-like body. Interestingly, Pluto’s moon Charon is believed to have been formed by a similar impact.
The point of all these facts is that in exploring the solar system through ground-based telescopes and robotic missions, we have come to learn that much of what was previously believed and even viewed as fact is wrong. Even though the largest planets are divided into the two categories of “terrestrials” and “jovians,” we have learned that no two planets in either category are exactly alike; in fact, each one is far more unique than its categorization would lead one to believe.
In astronomy, the more we learn, the more we find out we didn’t know and still don’t know. That is where the question of Pluto comes into the discussion. Pluto is estimated to be 70 percent rock and 30 percent ice. Uranus and Neptune are very icy, yet no one cites that fact to disqualify them from being considered planets. Earth in many ways is more similar to Pluto than to Jupiter, whose composition is similar to that of the Sun. Like Earth and the terrestrial planets, Pluto is differentiated geologically into core, mantle, and crust. The jovians are differentiated too, but they have inner cores of liquid molecular hydrogen, outer layers of hydrogen and helium (and several other gases in the case of Uranus and Neptune), and none has a solid surface.
With such a variety of characteristics and so much diversity, how can we possibly choose one factor and use that as the measuring stick for planethood? The answer is that we cannot because any characteristic chosen would be arbitrary. In the presence of so many factors and features, we need a planet definition that is broad enough to encompass all these objects. That leads us back to what it is they all have in common. And that answer is that they are all large enough to be shaped by their own gravity, which pulls them into a round shape, a condition known as hydrostatic equilibrium.
Among objects in hydrostatic equilibrium, we are likely to discover bodies with characteristics we cannot even imagine, both in this solar system and in others. Some may revolve around other planets. These differences do not mean the new objects are not planets, just that we may need to add new subcategories of planets as more is learned. As even Dr. Neil de Grasse Tyson admits, planetary science is still very much in its infancy. And that is not a time to be establishing narrow definitions, especially when we know an infusion of data about Pluto and the Kuiper Belt is coming within the next decade.
One of the best things about studying astronomy is the opportunity to “meet” and converse with people all over the world. These conversations have continued beyond the online classroom. Having been in the political world and dealt with very negative people who loved to put me down, publicly demonize me, and repeat ad nauseam how I was not good enough, I appreciate all the more the very positive, supportive classmates I’ve had. When I was afraid of failing the class—and the subsequent online ridicule if “Pluto haters” ever found out that “Plutogirl” failed astronomy—fellow students offered much valued encouragement and moral support. Their message was always, “you can do this.” Outside the classroom, that has largely been my experience with friends and acquaintances in the astronomy community, people who, ironically, I would never have met had Pluto not been demoted.
In the end, I passed the course with an 83 and discovered that one does not have to receive a perfect grade to have learned a tremendous amount. I look forward to doing a lot of writing about astronomy, including, as previously announced, writing a book about Pluto. Yet the fact remains that while most people go back to school to further their careers, I plan to continue this program because I want to do all I can to get Pluto reinstated as a planet. And in that process, I have re-discovered a fascinating field and many wonderful people, all of which make this a most worthwhile, meaningful effort.