Monday, March 21, 2016
Thursday, February 18, 2016
Today marks the 86th anniversary of the discovery of planet Pluto in 1930 by 24-year-old Clyde Tombaugh at the Lowell Observatory in Flagstaff, Arizona.
Sometime around 4 PM on that day, while using a blink comparator to move between two photographic plates depicting the same part of the sky taken several days apart a month earlier, Tombaugh detected a tiny dot that moved against the background stars.
That dot was Pluto. The fascinating story of its discovery is described here: http://pluto.jhuapl.edu/Participate/learn/What-We-Know.php?link=Discovery-of-Pluto .
“I have found your Planet X,” the young astronomer told Lowell Observatory director Vesto Slipher, ending the decades-long search for a trans-Neptunian planet initiated by observatory founder Percival Lowell.
Over the past year, we have had the opportunity to do what Clyde Tombaugh could only dream of—transform that tiny dot he found, not even large enough to be resolved into a disk with the most powerful telescopes of the day—into a living, breathing planet.
We are now into the “Year of Pluto 2,” and the amazing images and information keep coming and will continue to do so through most of this year.
This anniversary is an appropriate occasion to re-examine, in light of all these new findings, the claim that Pluto is somehow “different” from the solar system’s eight larger planets.
Let’s start with the often repeated, “Pluto is very different from the ‘big eight.’”
First, there are no “big eight,” unless one lumps together two very different types of worlds—the rocky, terrestrial planets on one hand, and the gas giants and ice giants on the other.
Any classification system that puts Earth and Jupiter in the same category but excludes Pluto overlooks an important fact, specifically, that Earth has far more in common with Pluto than it does with Jupiter.
Gas giants Jupiter and Saturn and ice giants Uranus and Neptune have no known solid surfaces. Both have extensive systems of rings and moons that are almost their own “mini-solar systems.” Jupiter and Saturn are composed primarily of hydrogen and helium, much like the Sun.
Like Earth, Pluto is rocky and geologically differentiated into core, mantle, and crust. Like Earth, it is geologically active. It has far more water ice than previously thought, and its geological processes suggest an internal heat source that could possibly support a subsurface ocean.
Some scientists see evidence for such an ocean in the faults and fissures on Pluto’s surface and in the planet’s lack of an equatorial bulge.
Equatorial bulges are created by the spin of rotating spherical objects. Because water moves more easily than ice, an underground ocean would reduce any bulge by acting against rotational forces.
Both Earth and Pluto have nitrogen in their atmospheres. The only other solar system world with a nitrogen atmosphere is Saturn’s moon Titan.
Both Earth and Pluto have large moons formed via a giant impact very early in the solar system’s history.
Pluto was initially thought to be larger than it is because until 1978, scientists did not realize they were looking at two objects rather than one when they observed Pluto through a telescope. The planet and its largest moon Charon, which is half its size, are separated by just 12,196 miles (19,640 km), the smallest separation between any planet and moon in the solar system.
And because Pluto and Charon orbit a center of gravity, known as a barycenter, outside of Pluto, between the two objects, they can genuinely be considered a double or binary planet system.
New Horizons’ findings indicate Pluto actually has more in common with Earth than anyone imagined.
Instead of the dead world many expected, Pluto has revealed itself to be “a world of unexpected complexity and riches,” mission principal investigator Alan Stern commented.
Among the small planet’s stunning array of terrains are wind-blown dunes similar to those on Earth and on Jupiter’s moon Europa. Worlds with atmospheres as thin as Pluto’s do not usually have dunes, suggesting Pluto’s atmosphere may once have been a lot thicker.
Pluto’s famous “heart,” named Tombaugh Regio for discoverer Tombaugh, has a young surface with no craters.
Ice floating on the left side of side of Tombaugh Regio, known as Sputnik Planum, flows in a manner similar to the movement of glaciers on Earth. Only two other worlds in the solar system, Earth and Mars, experience this type of activity.
The fact that Sputnik Planum’s terrain is constantly being reshaped suggests tectonic forces (geological forces that cause movements of a planet’s crust) are at work, possibly caused by internal heating produced through radioactive decay of rocky material in Pluto’s core.
“The Pluto system surprised us in many ways, most notably teaching us that small planets can remain active billions of years after their formation,” Stern said.
Pluto’s layered, atmospheric haze is similar to that seen on Titan. It is also far more complex than scientists anticipated. Pluto’s sky appears blue at sunrise and sunset because its haze particles scatter blue light. Which other planet has a blue sky?
Two mountains on the Pluto’s encounter side (that observed in most detail by New Horizons), Wright Mons and Picard Mons, appear to be ice volcanoes, also known as cryovolcanoes. These mountains have broad, gentle slopes, characteristic of what are known as shield volcanoes.
The only other shield volcanoes in the solar system are on Earth and Mars.
Pluto’s active geology and possibly cryovolcanism could be driven by a mix of ammonia and water ice in its mantle.
Located between the inner crust and outer core, that mantle may be experiencing convection, a process through which hot material rises up while cooler material sinks down.
On Earth, convection drives the movement of tectonic plates.
Networks of eroded valleys on Pluto’s surface, described by some scientists as “hanging valleys,” resemble similar features seen on Earth in Yellowstone National Park.
The point in emphasizing these detailed features is that Pluto may have more in common with Earth than with any other solar system planet.
The abundance of water ice on its surface and the possibility of a subsurface ocean add Pluto to the solar system’s leading contenders for microbial life, a list that includes Europa and Saturn’s moon Enceladus, both of which are believed to have subsurface oceans.
Data sent back by New Horizons just this week indicates Charon, which is also geologically active, once had a subsurface ocean too.
Nine and a half years ago, four percent of the IAU decided they knew how to best classify Pluto in spite of the fact that they had never seen it up close and knew nothing of its features. Even today, apologists for the IAU claim that their decision stands, that Pluto is not a planet because astronomy’s “ruling authority” said so.
Yet Pluto’s surface and atmosphere tell a very different story.
"I naturally refer to Pluto as a planet because that seems like the right moniker,” New Horizons project scientist Cathy Olkin states. “It has an atmosphere; it has interesting geology; it orbits the sun; it has moons. ‘Planet’ just seems right to me."
Friday, January 29, 2016
Thursday, January 21, 2016
The potential discovery of a Super Earth in the outer solar system made huge headlines today. Inferred from the eccentric orbits of several tiny objects in the Kuiper Belt, this planet is estimated to orbit 19 billion miles or 200 astronomical units (AU) from the Sun, with one AU equal to the Earth-Sun distance of approximately 93 million miles.
This distant world, which would take between 10,000 and 20,000 years to orbit the Sun, is estimated to have a mass ten times that of the Earth.
Significantly, this planet has not been observed or actually detected. Its existence is inferred solely through computer simulations.
Unfortunately, one of the two scientists conducting the study, Mike Brown, who has spent a decade obsessed with the very unprofessional claim that he “killed” planet Pluto, decided to take a page from the presidential candidates and use this possible discovery to promote his own personal agenda.
He did this by naming the potential object “Planet Nine,” a deliberate affront to those who reject the IAU planet definition just one day after the tenth anniversary of New Horizons’ launch.
By using this name on a press release distributed to countless media outlets, Brown assured that his version of the solar system would be repeated again and again in article headlines as the only view of the solar system.
It is a view based on the highly emotional, unscientific premise that our solar system cannot have “too many planets,” so artificial lines have to be drawn to keep the number of planets small.
By referring to any new planet discovered as “Planet Nine,” he is inherently denying the existence of the ongoing debate over planet definition and over the number of planets our solar system has.
According to the geophysical planet definition, held by many planetary scientists, a planet is any non-self-luminous celestial spheroidal body orbiting a star, free floating in space, or even orbiting another planet. If an object is not a star itself and is large enough and massive enough to be rounded by its own gravity, it is a planet.
That means, as I have often stated before, that dwarf planets are planets too. Alan Stern, the person who coined the term “dwarf planet” intended it to refer to a third class of planets in addition to terrestrials and jovians.
According to this definition, there is no requirement that an object “clear its orbit” to be considered a planet.
So for the many scientists and members of the public who adhere to the geophysical planet definition, our solar system has a minimum of 13 planets, 14 if we count Charon as part of a binary system with Pluto. In order from the Sun, these are Mercury, Venus, Earth, Mars, Ceres, Jupiter, Saturn, Uranus, Neptune, Pluto, Charon, Haumea, Makemake, and Eris.
Inner Oort Cloud Object Sedna and the recent, distant discovery known as 2012 VP113 and nicknamed “Biden,” are likely spherical as well, raising that count to 16. As Alan Stern noted, “If they do find it (this proposed object), it’ll be more like Number 19, not Number 9.”
Unfortunately, very few media outlets chose to seek the geophysical point of view. Instead, most simply more repeated the nonsense that Brown is “the Pluto Killer” and quoted only him and his research partner, Konstantin Batygin.
And Brown made sure to get in as many digs at Pluto and at denying the existence of the ongoing planet debate as possible, making statements such as, “There have only been two true planets discovered since ancient times, and this would be the third.”
Over and over, he presented his opinion as fact, and few journalists even thought to question it. From the geophysical view, more than two planets have been discovered since ancient times because Ceres, Pluto, Haumea, Makemake, and Eris are true planets too.
Brown and Batygin supposedly considered other names for this possible new object, including George, Planet of the Apes, Jehoshaphat and Phattie. Any one of these would have been better than “Planet Nine,” which is not really a name but a statement saying his view of the solar system is the only view.
Most following the New Horizons mission now know just how much of a planet Pluto is. It is more geologically active than Mars and has features such as flowing ice and likely cryovolcanoes, which strongly suggest an internal heat source no one anticipated.
There is complex interaction between its atmosphere and surface, and there may even be an underground ocean that could harbor microbial life. A good number of New Horizons scientists have commented that given these features, there isn’t anything else they can call this world other than a planet.
None of this apparently makes any difference to Brown, but then again, he doesn’t study Pluto. So insistent is he on the controversial “requirement” of orbit clearing that he states of the potential discovery, “The fact that it could affect the orbits of other objects over such a wide area would make it “the most planet-y of the planets in the whole solar system.”
Why should an object’s effect on other objects make it more “planet-y” than its intrinsic properties?
Theories positing the existence of a large planet far beyond Pluto have been around for a long time. Announcing that a computer simulation points to this possibility is an ideal opportunity to excite the public about space exploration and what might be out there.
Instead, Brown effectively hijacked this story to promote himself, his imagined accomplishment of having “killed” Pluto, and his subjective view of our solar system, conveniently ignoring that his view is just one in an ongoing debate.
The first principle of propaganda is, “A lie repeated a thousand times becomes the truth.” Another is “He/she who defines the terms wins the debate.”
Brown may repeatedly attempt to pass off his view of the solar system as the only view, but that does not mean the media or the public has to accept it. The story of a possible new solar system planet can stand on its own, without endless promotions of Brown and his book, parts of which stray so far from astronomy to the point that he actually devotes an entire chapter to engagement rings!
If I read a book about the solar system, the only rings I want to learn about are those around planets or asteroids. I suspect many other astronomy enthusiasts share that view.
One of the view journalists who did go out of his way to be fair and balanced in this story is Alan Boyle, author of the book The Case for Pluto. His article can be found at http://www.geekwire.com/2016/planet-nine-astronomers-boost-the-case-for-seeking-a-large-planet-x/?fb_action_ids=10154006841913189&fb_action_types=og.likes .
In that article, Alan Stern discusses what an actual discovery of a large outer solar system planet would mean from the geophysical point of view. He says, “And if it is found, it’ll confirm lots of work predicting the Oort Cloud is littered with planets, and the solar system made dozens to hundreds of them.”
Anyone who rejects the IAU planet definition or even just wants to acknowledge that planet definition is an ongoing debate should simply refuse to call this object “Planet Nine,” especially if it is actually found. Do not give Brown the power he seeks to define the terms and thereby win the debate.
This object would in no way replace Pluto, and its discovery has nothing to do with Pluto; it would simply be a fascinating addition to our solar system, which has room for many planets. That in itself makes for a fascinating story.
Tuesday, January 19, 2016
Wednesday, December 23, 2015
A year ago, in my Winter Solstice entry, I jubilantly noted that 2014, the year referred to by fans of Pluto and New Horizons as “Pluto Eve,” was giving way to the “Year of Pluto.” Anticipating the “something wonderful” mission Principal Investigator Alan Stern predicted we would find on the small, distant planet, I noted, “The light is about to shine on a very dark and mysterious world.”
As Tim Dean, editor of “The Conversation” website pointed out in his 2015 review of science and technology—which placed Pluto first—2015 seems to have come and gone nearly as fast as New Horizons flew by Pluto.
This is the year Pluto was a star, a celebrity that made the cover of multiple magazines and was recognized by many news outlets and websites as a top science story.
Like many who have followed this mission, I already miss the building buzz and excitement that characterized the final six months of New Horizons’ approach to Pluto.
Does the Year of Pluto end with 2015, I’ve questioned over the last several weeks.
Our view of this small planet has been transformed from a tiny dot, at best a pixelated Hubble image, to an actual world, with jagged mountains, valleys, snakeskin terrain, flowing ices, a layered haze, and one particular feature that has generated awe and wonder worldwide—the prominent heart-shaped region known as Tombaugh Regio, named in honor of Pluto discoverer Clyde Tombaugh.
Everything about this tiny world that is more geologically active than Mars has surprised scientists, who continue to brainstorm in an effort to explain its complex surfaces and processes.
Only about 25 percent of the data New Horizons’ seven instruments took on flyby day has been returned. The rest is still on the spacecraft, and the downlink will not be complete for approximately another 300 days.
The fact that 75 percent of the data is still to come makes a compelling case for the position that the Year of Pluto will go on past the calendar year 2015.
Even when all the data is back, its study and analysis will take years, as can be seen from the fact that 25 years after Voyager 2 flew by Neptune, a scientist studying those images identified an undetected moon orbiting the ice giant.
And because the data is generating so many more questions, particularly regarding Pluto appearing to have an internal heat source, it seems inevitable scientists will want to go back for another view.
Stern often describes the sequence of planetary exploration as starting with a flyby, then moving to an orbiter, a lander, a rover, and finally, a manned expedition.
So far, the only planetary body that has undergone all these levels of exploration is the Moon. Mars has been explored with several rovers, and plans are underway to send astronauts there sometime during the 2030s.
The development of new technologies could reduce a spacecraft’s travel time to Pluto. Small cube satellites could be sent in a follow up mission. Significantly, the US has just now resumed manufacturing the type of plutonium required for a mission so far from the Sun.
Pluto remains a prime destination because it is one of several solar system worlds that has or might have a subsurface ocean that could host microbial life. That puts it in a category that includes Ceres, Jupiter’s moon Europa, Saturn’s moons Titan and Enceladus, and possibly other, similar worlds at the forefront of the search for extra-terrestrial life.
We will never again see Pluto the same way we did just a year ago. When in 2006, four percent of the IAU voted to “reclassify” Pluto, they effectively made a decision for a world about which they knew nothing. How can anyone classify a world without knowing what it is, what it is made of, and what processes are taking place on it?
Recently, French scientist Jon Luc Margot published a mathematical formula which he claims astronomers can use to determine whether an individual exoplanet “clears its orbit” and therefore should or should not be classed as a planet by the IAU.
Incredibly, Margot actually stated on record that it doesn’t matter what an object is made of because its composition has no bearing on whether or not it is a planet. The only thing that counts, in his view, is whether the object clears its orbit.
Most people who look at the complex world imaged by New Horizons see a planet. Far from being fundamentally different from those sometimes referred to as “the big eight,” Pluto actually has much in common with them. Ironically, Pluto shares some surface characteristics with Earth and Mars. It is not a rubble pile loosely held together or a “giant comet” composed largely of ice.
2015 ends with the debate over Pluto’s status and the question of how to define a planet remaining unresolved. It might remain unresolved for a long time. Meanwhile, every new image and detail sent back across four billion miles serves to confirm that this strange world is not just a Kuiper Belt Object but half of a binary planet system.
For thousands of years, the Winter Solstice on Earth has been a time of rebirth and renewal, the beginning of the transition from darkness to light.
We’ve only begun that transformation from darkness to enlightenment when it comes to Pluto. Regarding the adventure of unraveling Pluto’s secrets, the only appropriate language is, “To be continued…”