A New Year's Message

The Internet is a strange place. On the one hand, it empowers people, providing easy access to information and enabling those with like-minded interests to come together and share those interests. Unfortunately, the nature of the beast is that it can also become a venue for rumors, false information, and misunderstandings.

On several recent occasions, especially over the last few weeks, various comments and statements which I never made and do not support have been attributed to me. Additionally, things I said in jest have been misinterpreted as being serious when this was never the intention. Whether this all is due to simple misunderstanding or miscommunication of things I said, I want to take this opportunity to set the record straight.

I have never said and never would say that Mike Brown's book should be banned or not published or that he should not be permitted to give public talks.  As a writer, I recognize the sanctity of the First Amendment, and as the cliche says, I may disagree with what someone says, but I will defend to death their right to say it. That is true for those with whom I disagree about any subject, including the status of Pluto. Suppression of discussion and debate is never a good thing.

What I do advocate is that forums, publications, web sites, seminars, etc. present both sides of the issue by hosting speakers representing both opposing positions and/or printing articles representing both opposing positions. In some cases, there are more than two positions on an issue, and all should be heard.

In his essay On Liberty, 19th-century writer John Stuart Mill advocates an "open marketplace of ideas," meaning every idea, every position should be given a venue. An optimist, Mill believed the best ideas would rise to the top on their own merit. Whether and how often this happens is a matter of debate, but Mill's noble concept remains an ideal for every free and open society.

Additionally, some comments I have made as jokes or tongue-in-cheek remarks have unfortunately been taken the wrong way. Brown's description of himself as "plutokiller" will inevitably bring on references to Death Stars and various science fiction destruction scenarios. It should naturally be understood that this is an attempt to inject some humor into the debate. Similarly, humorous comments referencing Star Wars or Harry Potter in response to the "plutokiller" theme are also jokes and not meant to be taken as ever wishing harm on anyone.

The response to my involvement in astronomy and advocacy for Pluto has been overwhelmingly positive. There have been a few exceptions where I have received vitriolic emails from people who either disagree with me or do not like what I am doing. These have been very hurtful, and as a journalist, I have publicly exposed their contents in the hope of deterring any such future messages. Sometimes, it is hard to remember that by putting oneself in the public eye, one automatically leaves oneself vulnerable to less than positive feedback. This is the unfortunate nature of the beast, yet it is still a painful thing to face.

The ideal in science is being dispassionate and objective. In the arts, such as writing and acting, where I have spent most of my life, expressing passion openly is much more accepted. I admit to being very passionate about Pluto and about astronomy, but I assure anyone put off by such passion that it in no way reflects any type of malice. While I might be involved in boycotts, protests, or parodies of things I don't like, I would never wish harm to anyone whose views differ from mine or whose style differs from mine (wishing electoral defeat or dissolution/reform of a group such as the IAU does not count as "harm" in my book).

Astronomy is a grand adventure, a constant experience of wonder and discovery. I have been extremely fortunate in finding teachers and mentors, beginning with fellow members of Amateur Astronomers, Inc. of Cranford, NJ, and extending to amateur and professional astronomers around the world and instructors at Swinburne University, who have been eager to teach, generous with their time, and patient in explaining difficult concepts. These experiences and a love of planetary science have led me to decide to further my studies at Swinburne in the Masters program.

Astronomy also unites us all by reminding us that we are one people on one "pale blue dot," a small planet that is fragile, has seen too much abuse, and is in tremendous need of healing. The "Star Trek" universe always appealed to me because in it, humanity was able to move beyond war and petty divisions to come together for the greatest adventure of all--the exploration of "strange new worlds." I still believe this can be our future.

Toward that end, I apologize to anyone of whom I spoke ill or maligned or was perceived to do so, and emphasize again that my purpose in writing online is solely the promotion of planet status for Pluto and all dwarf planets. It never has been and never will be a personal vendetta.

Here's wishing a Happy, Healthy 2011 to all seven billion people on this planet and to the animal and plant life with which we share our world. While debating the definition of planet and the status of celestial objects, I hope we can all remember to have fun, to maintain a sense of humor about the whole thing, and to never forget the wonders of our universe and be grateful for the opportunities to experience them.Happy New Year!

The Solstice Is the Reason for the Season

“All that lives must die to be reborn again.”

 As far back as I can remember, this time of year felt sacred, even otherworldly. At first, I thought it was the fairy tale atmosphere of Christmas, the lights, the music, the colors, the gifts. And because my family didn’t celebrate this holiday, this special time became one of sheer misery, a party everyone else had to which I wasn’t invited.

Always the “bookish” type and at the same time a rebel, I decided at about 11 or 12 to use the encyclopedia we had at home to look up the origin of celebrations at this time. That was when I learned why others have felt, recognized, and commemorated the solemnity of this time for as far back as 10,000 years—the Winter Solstice.

Because I live on Earth and experience the seasons as much as anyone, I realized with a surge of joy that the Winter Solstice is my party too. No one is “not invited.”

By now, it is well known that just about all of the trappings of the holiday season, everything from wreaths, evergreens, and most of all the new birth, originated well before Christianity ever existed. Yet because Christianity so completely co-opted just about every aspect of Winter Solstice celebrations, the original meaning of the season has been lost to so many people. This is in no way meant to offend those who celebrate the Christian holiday. No one around today was involved in the suppression of the Solstice celebrations, which happened centuries ago.

Hanukkah never really did much for me personally. Maybe it’s because many Jewish leaders take part in a similar attempt to dissociate it from the Winter Solstice, which is somewhat disingenuous. While it commemorates events that took place over several years, Hanukkah clearly is rooted in seasonal celebrations representing the waxing light of the Sun. In fact, the one candle that lights all the others has the very same name as the Hebrew word for Sun.

Those who told me that holiday has nothing to do with the Winter Solstice only made me less interested in it. The same is true of those who described it as a “minor” holiday. Nothing about this time of year is “minor.” Such sentiment runs completely counter to everything I authentically feel inside.

In the last 20 years, there has been a revival of Earth spirituality, and abundance of books on the seasonal festivals, and a growing movement to go back to our roots in nature and celebrate them. Along with the Internet, this has been a godsend to so many of us who know in our gut the profundity of the season and long to not just celebrate it but be part of it.

People sometimes ask me, why celebrate the rebirth of the Sun since as an amateur astronomer, you know the Sun doesn’t change at all; rather, it is the Earth that moves.

To me, science does not negate every bit of mysticism and symbolism in the universe. The Sun might not literally die and be reborn, as the old myths describe, yet from our perspective on Earth, it certainly appears that way. Knowing it is all caused by the Earth’s axial tilt does not diminish the magic represented by the apparent birth of life from death. Nature appears dead; the trees are barren; the seeds lie hidden and buried underground. Yet life does not end. The growing strength of the Sun from the day of the Winter Solstice forward is the spark that kindles new life in everything. Seeds germinate underground, growing to the strengthening light until at last they break through the frozen surface at the Spring Equinox. Dormant trees eventually grow new buds that become leaves. Hibernating animals rest only to return as the warmth grows stronger.

The “comfort and joy” of the Solstice is in knowing that it is a time of sleep, but sleep does not equal death. Even physical death, which appears to us as an end, may be just a time of rest before a new birth. The seasonal cycle may very well be nothing less than a reflection of a much greater, much more profound cycle. It provides us the hope that, as stated in one Solstice story, “everything lives and dies and lives again. There is no end to life.”

Skeptics will jump on that last statement, calling it a fairy tale and wishful thinking. Maybe it is, but maybe it is not. The Winter Solstice provides an opportunity to not just understand the mechanics of an astronomical event, but to allow awe, wonder, and magic into our lives. It is something everyone has a right to celebrate and honor. Limiting the joy of the season to only Christians is a disservice to everyone else.

I live for the day when, instead of having the “Christmas talk” with their four-year-olds, or feeling like December is a “dilemma,” non-Christian parents—and Christian parents too—instead share with their children the mystery, beauty, and even sanctity of the real reason for the season.

The words of this song, "Winter Solstice," by Ruth Elaine Schram, express well the hope of this time of year.

"In the Midwinter when the air is chill,
on the horizon the Sun stands still.
After December's full Moon so bright,
soon it will be the year's longest night!

Stars will align, and they will leave their mark
showing the point of the Sun's new arc!
From this day forward, its path will ascend!
Hours of daylight grow longer again!

This is the Winter Solstice!
Winter Solstice!
Follow the path of the Sun!

This is the Winter Solstice!
Winter Solstice!
Now a new path has begun!

Follow the path of the Sun!"

Happy Winter Solstice!

And Happy Summer Solstice to all in the Southern Hemisphere!

Pluto Has Oceans Under Ice?

Pluto Has Oceans Under Ice?#ng_comments

Some more fascinating information about this intriguing little planet.

Mike Brown, Mind Reader???

Mike Brown, who never misses an opportunity to dub himself the “plutokiller,” apparently missed his calling. Given his latest outrageous statement, which presumes to know what supporters of Pluto as a planet are thinking better than we do ourselves, he should have pursued a career in fortune telling or mind reading.

Debates in which people representing opposing views agree to disagree and discuss issues in a civil manner, without resorting to ad hominem attacks, have a long and proud tradition. At the Great Planet Debate in August 2008, scientists and lay people representing both sides of the planet definition debate successfully conducted such a debate in a spirit of friendship and camaraderie.

Unfortunately, Brown, who continues to repeat the false claim that the planet definition debate is over and that the only astronomers who still support Pluto as a planet are those affiliated with the New Horizons mission, has shown himself incapable of conducting such a debate.

When asked in an interview by Space.com about the many astronomers who still regard Pluto as a planet, Brown offered this answer:

“There aren't many astronomers. There is a very small number of very vocal people. The people who jump up and down the most about Pluto being a planet have the most to gain from Pluto being a planet. They're on the New Horizons mission to Pluto. I understand their nostalgic need to still feel like they're going to a planet. There's this feeling that by saying it's not a planet it becomes less important, and their life's work to send this spacecraft to Pluto becomes less important”

The comment can be found here: http://www.space.com/scienceastronomy/mike-brown-discusses-dwarf-planet-pluto-101119.html

This is a blatant lie, and it is downright unprofessional for Brown to mislead the public this way. The overwhelming majority of astronomers who still consider Pluto a planet are not affiliated with the New Horizons mission. In fact, one of them is a member of the trio that discovered Eris—Dr. David Rabinowitz.

New Horizons is fully funded and loses nothing from the demotion. Dawn is a mission to a dwarf planet and an asteroid, and it has just as much respect as New Horizons or any other NASA mission. Most astronomers who consider Pluto a planet—and there are many—are simply planetary scientists who believe that astronomers who don't study planets should not be the ones to define what a planet is.

The comment about New Horizons is nothing less than a cheap shot at Dr. Alan Stern, who has led the objectors to the IAU decision, not because of this mission but because he believes in what is known as the Geophysical Planet Definition—that a planet should be defined by what it is rather than where it is, and that any non-self luminous spheroidal body orbiting a star is a planet. This is a legitimate scientific position.

As unprofessional as the above statement sounds, it is not Brown’s worst. That new low was reached yesterday in an interview with Universe Today, where Brown accused supporters of Pluto’s planet status of deliberately lying and misleading the public, of not actually believing our own stance on this issue.

He says, regarding those who view Pluto as a planet: And honestly, I think manipulative is the word. They don’t believe what they say, they know what they say is not true and they say it in ways that are deceitful. That is maybe a strong statement to make, but they know what they are saying is not true. That bothers me. You shouldn’t say things that you know is not true just to make a point.”

Source: http://www.universetoday.com/81166/q-a-with-mike-brown-pluto-killer-part-2/comment-page-1/#comment-87740
What absolutely unbelievable arrogance. Brown reaches a new low with this baseless ad hominem attack. Those of us who view Pluto as a planet most certainly DO believe in what we are saying. We advocate a geophysical definition of planet, in which any object massive enough to be rounded by its own gravity that orbits a star is a planet. The idea is a definition based on what the object is, not where it is. Pluto is both a Kuiper Belt Object and a planet.

Is Brown a mind reader now? What makes him think he knows what supporters of the geophysical planet definition believe or know to be true more than they do? His palm reader? If anyone is misleading the public, it is Brown who falsely claims the debate over planet definition is over, when it is not. And it is hard to believe those who claim he is sick of the debate when he is making money off of the book and numerous talks he gives on the subject.

There is a logical way to say our solar system does not have only eight planets. Simply, it is to note that there are not only two types of planets, terrestrials and jovians, but a third class, the dwarf planets. Dr. Alan Stern coined this term in 1991 to indicate objects large enough to be rounded by their own gravity but not large enough to gravitationally dominate their orbits. Our solar system, in the words of writer Alan Boyle, has four terrestrial planets, four gas giants, and more in the form of numerous dwarf planets.

How does it make sense to put Earth and Jupiter in the same category? Earth has more in common with Pluto than with Jupiter. Jupiter has no solid surface, has its own “mini-solar system,” and is composed mostly of hydrogen and helium. That makes it more like the Sun than like the Earth (except, of course, it doesn’t conduct hydrogen fusion). Earth and Pluto are both rocky, both have large moons formed via giant impact, and both have nitrogen atmospheres. How we classify objects is subjective; it is based on attributes we pick and choose. Different astronomers will choose different attributes.
Brown’s cheap shot here is a disservice to science, an attempt to marginalize a legitimate scientific point of view. Imagine if, in 1920,when astronomers Harlow Shapley and Heber Curtis held a public debate over whether the Milky Way constitutes the entire universe (Shapley’s view) or whether the universe is made up of many galaxies (Curtis’ view, later proven accurate), one of the debaters suddenly told the other, “you don’t really believe the point you are arguing, and I know this for a fact.” That person’s scientific credibility would have seriously been called into question.

A likely reason Brown is resorting to these underhanded tactics is his underlying awareness that the IAU definition does not stand well among astronomers, with the growing undercurrent favoring a broader, more inclusive planet definition that makes room for more than just terrestrials and jovians as planets.

Brown wrote a book about himself, not about Pluto. In fact, a good portion of the book is dedicated to his life as a husband and father. That sort of thing belongs in the autobiography, lifestyle, or parenting sections, not in a book about astronomy. Not a single one of the many books on the subject of Pluto and planet definition takes such a detour.

Interestingly, one writer ended a book review by stating the real credit goes to Brown’s wife Diane. As a woman, I find this highly offensive. What sort of message does it send to women and girls when a woman is credited for being married to an astronomer rather than being an astronomer herself? It is nothing personal, but Diane Binney Brown is not a hero of astronomy or the person to be most credited for Eris’ discovery.

In my astronomy studies, I just completed a research project on Henrietta Leavitt, the astronomer who discovered what is known as the Period-Luminosity relationship, the fact that for a particular type of stars that vary in brightness (known as Cepheids), their period of going from minimum to maximum to minimum again is directly related to their brightness. Leavitt,
like astronomer Caroline Herschel in the 19^th century, never married or had children. Instead, she contributed something different. Her discovery transformed cosmology by allowing astronomers to determine the distances to galaxies near the Milky Way. Yet because she was a woman, Leavitt was never allowed to pursue research on these variable stars, not allowed to use telescopes at Harvard College Observatory, and consigned to doing menial work for observatory director Edward Pickering.

If any people should be held up as role models for women in astronomy, it is women like Leavitt and Caroline Herschel, not women who marry astronomers.

Brown will likely object to any criticism of his wife, noting that his family members should be off limits to critics. Well, he cannot have it both ways. If he wants his family members immune to criticism, then he should keep them out of the public eye, as many politicians do. If he uses them as pawns for self-promotion, then that use is fair game for any critic.
In rhetoric, logic, and debate, resort to ad hominem attacks is done most by those who know they are losing the debate. That is what is happening here.

Supposedly, at one point in his book, Brown prides himself on so accurately predicting a relative’s pregnancy that the relative questions whether he is an astronomer or an astrologer. Many other people are wondering just this too. Since Brown is so sure he knows what his opposition thinks, I suggest we bring in skeptic James Randi to test his mind reading skills.

Or we could just hire a psychic to read his palm.

The Fight for Dwarf Planets Continues

Check out this excellent interview with Dr. Alan Stern, Principal Investigator of NASA's New Horizons mission to Pluto, by Space.com here:

http://www.space.com/scienceastronomy/pluto-planet-debate-stern-qanda-101129.html

I want to commend Space.com for presenting both sides of the Pluto debate rather than just one. Stern's argument makes sense because it is based on what an object is rather than where it is. Gravitational dominance is addressed if we class these small planets as "dwarf planets." It means they are planets but not large enough to gravitationally dominate their orbits.  Arguments that "we cannot have too many planets" because kids won't be able to memorize them or because then the term planet won't be "special" have no scientific merit. We might as well limit Jupiter to four moons instead of 63 for the same reason. The same is true for arguments that there are only two kinds of planets, terrestrials and jovians. Just because an object is not a terrestrial or a jovian doesn't make it not a planet--it makes it a different kind of planet. We very well may discover objects in other solar systems that require adding a fourth, fifth, etc. category of planets. As for eccentric orbits, many giant exoplanets, some with several Jupiter masses, have orbits far more eccentric than that of Pluto. There are at least two cases of systems with two giant planets orbiting their stars in a 3:2 resonance just like Neptune and Pluto. If these objects are not planets, what are they?

Similarly, spherical moons of planets are compositionally akin to planets themselves, which is why Stern and others have proposed calling them "satellite planets." If we ever land rovers on Triton and Pluto, the challenges and circumstances will be very similar in spite of the fact that one orbits a planet and the other orbits the Sun directly.

Brown's argument that there are only a few astronomers left who view dwarf planets as planets and that they are all on the New Horizons mission was a cheap shot and is blatantly untrue. How many of the 300 professional astronomers who signed the petition rejecting the IAU decision are on the New Horizons mission? The answer is very few. New Horizons is already fully funded and unaffected by whatever resolutions the IAU passes. In fact, the Dawn mission to Ceres and Vesta, launched to a dwarf planet and an asteroid, receives no less credibility than any planetary mission. The reality is many astronomers know that the IAU decision was politically motivated and done surreptitiously in a way that violated the group's own bylaws. Rather than accept it, most planetary scientists are simply ignoring it. Most of the 424 IAU members who voted on the 2006 resolution are not planetary scientists but other types of astronomers. Why should they and not those who study planets be the ones who determine what a planet is?

A Thanksgiving Message

On February 22 of this year, I posted an entry in this blog asking for help to save the observatory of my beloved astronomy club, Amateur Astronomers, Inc. Last December, we were sent an eviction notice by Union County College, where our observatory is located. This is a very belated thank you to all those people who took the time to call and write to the Union County Board of Chosen Freeholders and the Trustees of Union County College asking to save Sperry Observatory, which has been on the site for over 40 years. We were blessed with an outpouring of support from the public and the media, which ended up making a real difference. We were especially blessed by the support of State Senate Majority Leader Barbara Buono, who publicly stood up and spoke on behalf of our observatory.

During the spring, negotiations with the college administration were re-opened, and a new two-year agreement with the college was reached, granting us a reprieve. The announcement of the agreement can be read here: http://www.asterism.org/ . Click on "Special Notices."

Writing only as an individual, not representing anyone but myself, I want to thank everyone who took action on behalf of our club and our observatory. That little building has been like a second home to me for over three years. Thanks to your efforts, we can continue to share our love of astronomy and the beauty of the universe with the public from our beloved home of more than four decades.

On a similar note, I want to thank the many individuals--lay people, amateur astronomers, and professional astronomers--who have not only stood by planet Pluto, but have given me moral support on several occasions when I received some very nasty emails by a few meanspirited people opposed to my advocating for Pluto. Those who sent these messages, which were filled with personal attacks and not legitimate arguments DO NOT represent the majority of astronomers or lay people who support the IAU decision. I have had many friendly, respectful conversations with those on the "other side" of this debate, including the late Dr. Brian Marsden, who died too young this month and will most certainly be missed. How sad that he won't be here to see the images from Dawn and New Horizons, which certainly would have been of tremendous interest to him.

This is also an appropriate time to make an announcement concerning my book The Little Planet That Would Not Die: Pluto's Story. Yes, the book is still coming, but unfortunately, not by the end of 2010, as I had hoped for so much. In past entries, I have reported that I am taking classes in astronomy at Swinburne University with the goal of obtaining a Graduate Certificate of Science in Astronomy. These classes have been rewarding but also extremely challenging--challenging to the point that I realized I could not adequately complete the classwork and at the same time do justice to a project as important as a book about Pluto. The book is a work in progress, but with the last Swinburne class assignment, a research project, due on December 4, that progress has had to be put on hold.

Once that project is submitted, I will be back at work on the book full speed ahead. I will be taking a break after four classes at Swinburne with the goal of resuming studies toward the Masters in Astronomy after the book is completed, published, and promoted, hopefully with a book tour.

Also coming after the classwork is done will be the promised review of the DVD "Naming Pluto" and a book review of Pluto: Sentinel of the Outer Solar System by Dr. Barrie W. Jones.

Here's wishing a Happy Thanksgiving to all who celebrate and a big thank you to all of Pluto's loyal fans!

It Was Never "Eris vs. Pluto"

When Eris was observed occulting (passing over) a faraway star late last week, astronomers realized that their conclusion of Eris being bigger than Pluto was likely premature. No sooner had the information been released than the media began referring to a demotion for Eris equaling a victory for Pluto. And once again, they have it wrong.

On November 5, several teams of astronomers in the Chilean Andes observed Eris pass in front of a 17^th magnitude star in the constellation Cetus. Many additional astronomers observed the efforts of one of these teams remotely, via the Internet. The best observation was made by Jose Luis Ortiz at the Institute of Astrophysics of Andalusia, Spain using a 16-inch telescope. Their occultation video can be found here: http://www.youtube.com/watch?v=HxQ0b8p4cGY

By viewing Eris pass over this star, astronomers can determine Eris’ diameter. What they discovered is that Eris has a diameter of 2340 kilometers or 1454 miles or less, making it a bit smaller than Pluto, which has a diameter of 2344 kilometers or 1456.5 miles, plus or minus 10 kilometers.

Because Eris’ discovery re-opened the already ongoing debate over the definition of planet, Eris is often portrayed as Pluto’s rival, the cause of its demotion. This viewpoint misses the mark completely because the two planets were never in competition. On the contrary, Eris’ existence confirms that Pluto is not a loner, that there is an entire class of small planets beyond Neptune, which share features with one another as well as with Neptune’s largest moon, Triton.

Small objects at such distances are difficult to measure under the best of circumstances. Eris is three times further from the Sun than Pluto. Previous Hubble images showed it to have a slightly larger diameter than Pluto, but even the best such measurements have a degree of uncertainty.

According to Kelly Beatty in Sky and Telescope magazine, Eris may have previously appeared larger than it really is because its axis is pointing toward the Sun, warming up the hemisphere facing the Sun and thereby leading to inflated infrared measurements. The article can be found here: http://www.skyandtelescope.com/news/106861063.html?loggedin=y

Eris’ mass is currently believed to be 2.5 grams per cubic centimeter, making it more massive than Pluto even if it is smaller. Pluto’s mass is estimated at 1.8 to 2.1 grams per cubic centimeter. Higher density likely means it is composed of more rock and less ice—another argument against classifying either Eris or Pluto as comets or “dirty snowballs,” given that the majority of their composition is rock. And Eris has a reflectivity of about 90 percent, significantly higher than that of Pluto, meaning it is highly reflective of sunlight falling upon it. This too could make the planet appear bigger than it really is.

The diameter numbers for Pluto and Eris are so close as to be almost identical. No one should be surprised if the “contest” over which is bigger goes back and forth many times as new data becomes available.

The fact that Eris and Pluto are so similar works against the mindset that demoted Pluto in the first place. The argument was we have four terrestrials, four gas giants, and one misfit, Pluto. Eris’ discovery illustrates that Pluto is not and never was, a misfit. It was the second (as Ceres was the first) of a third class of planets to be found in our solar system, small objects large enough to be planets because unlike asteroids, they are large enough for their own gravity to pull them into a round shape. Dwarf planets are simply small planets not large enough to gravitationally dominate their orbits. There is no rational explanation to label them as not being planets at all other than the artificial, convenience-based argument that our solar system cannot have too many planets, as children will never be able to memorize them.

Pluto and Eris are not rivals; they are two of a kind. Makemake and Haumea are likely similar in composition, mass, and density. Interestingly, all these objects also bear striking similarities to Neptune’s largest moon, Triton. Triton orbits Neptune backwards, meaning it revolves in the opposite direction as Neptune does around the Sun. It is in an unstable orbit, meaning it likely was once a planet with its own orbit around the Sun and was subsequently captured by Neptune.

With a diameter of 2700 kilometers, Triton has a composition strikingly similar to that of Pluto. Both have surfaces covered with frost of carbon dioxide, carbon monoxide, nitrogen, and methane, and both have a pinkish-red color. These similarities are enough to raise questions about whether Triton, Pluto, and Eris, as well as possibly Makemake and Haumea, have similar origins.

Anyone interested in more detail about Pluto’s troposphere (lower atmosphere) can find it at http://www.astro.ex.ac.uk/exoclimes2010/posters/1.7_Zalucha.pdf

Even among the four terrestrials and four gas giants in our solar system, no two planets are identical in size, composition, geology, number of moons, etc. The similarities and differences that we pick and choose to categorize these objects are largely subjective. Saturn has the lowest density of all the planets; it would float if we could find a large enough ocean in which to place it. Jupiter and Saturn have more in common with the Sun than with the Earth when it comes to composition, as the former are composed mostly of hydrogen and helium, and neither has a solid surface.

Astronomers determined Jupiter and Saturn are not stars, however, because they never conducted hydrogen fusion and therefore never produced their own light—neither is anywhere near massive enough to do this. Yet at the same time, they chose to put Jupiter and Earth in the same overall category of planet even though the two bodies have little in common. Earth actually has more in common with Pluto than with Jupiter. Both Earth and Pluto are rocky with solid surfaces; both have nitrogen in their atmospheres, and both have large moons believed to have formed via giant impacts with the original planet.

The next time you hear people use the argument that Pluto is “not like the other planets,” the old “one of these things is not like the others,” remember that inherent in this statement is a subjective choice of characteristics used to determine similarity and difference. A different choice of characteristics will yield a different categorization system. If we use hydrostatic equilibrium to classify an object as a planet, spherical moons of planets like Triton are essentially planets themselves and deserve their own category of secondary or satellite planets.

The best way to learn the specifics about these bodies is to go there. An Eris Express would take about 30 years, but if we can find a way to speed up that travel time and to fund such a mission, the returns would be priceless. The same is true for further exploration of Uranus and Neptune and their satellites, possibly through orbiters like Galileo did for Jupiter and Cassini is doing for Saturn.

Until we actually see these places up close, all conclusions should be understood to have a tentative quality about them. People want quick, easy answers, but that does not work for small objects at such distances. For the foreseeable future, we just have to learn to accept that there is no “final answer.”