The Planet Killers
Barnard's Star Planet by Don Dixon
Ask an astronomer why he or she has devoted their lives to the study of the cosmos, and you’re likely to hear about a lifelong romance with the sky, a connection with the deep vastness of space, and a drive and a desire to explore what’s out there. Astronomers are in the discovery business, and they want to add to the richness of the Universe.
Dr. Mike Brown, Pluto Killer
But many times the act of revealing something new can actually have unintended, destructive consequences, as the changing science literally reshapes the world around us. One first hand insight can be read as Caltech astronomer and Kuiper belt explorer Mike Brown reflected on his 2005 discovery of Eris, the larger-than-Pluto object which led to the eventual demotion everyone’s favorite spheroid. This “destroyed” the old solar system, leaving our neighborhood with a mere 8 “real” official planets in the eyes of astronomers. This caused a gigantic public backlash, with everyone from schoolchildren to grandmas writing astronomers and planetarium directors nasty letters that ended with lots of exclamation points. Mike Brown seemingly accepted his public role as a sort of astronomical bad guy when he picked his Twitter name @plutokiller. In fact, a quick check on my Twitter account just now revelas Dr. Brown jokingly tweeting:
“I just persuaded a group doing a solar system scale model to not include Pluto as the 9th planet. My work is never done.”
So, perhaps to make an astronomical omelet, you have to break a few Kuiper eggs? Pluto’s predicament may just be a semantic battle between astronomers over what a planet is, but astronomers sometimes find themselves with the strange task of actually trying to”un-discover” something, proving that something we thought was real is only a numerical illusion.
Much of what we know about the Universe comes from teasing an incredible amount of information out of the faint light we see from a galaxy, a star, planet, or even specks of dust. Like any scientific data, these fingerprints of light can be interpreted in different ways, and subject to many different factors affecting them, so eliminating alternative explanations for something before announcing a major discovery becomes especially important.
When the first planet found around another star was announced, our imaginations solidified our new sister solar system for us by visualizing this new world whirling around its star. We made this planet as real as anything else in the Universe (I mean, have you ever been to Pluto?). But what would be our reaction if this planet suddenly blinked out of existence, and yanked from our reality? Can astronomers recall an entire world? As it turns out that’s exactly what happened, and it was decades before the extrasolar planets around 51 Pegasai or PSR-1257+12. The astronomer who gave us the first extrasolar worlds was Peter van de Kamp, and the man who took them away was the University of Pittsburgh’s George Gatewood.
Peter van de Kamp
Peter van de Kamp was born in the Netherlands in 1901, and by many accounts, was an endearing child who liked to play tricks on other children and adults. He received his doctorate in physics at the University of Utrecht in 1922, and then traveled to Berkeley. It was there he made his mark on astronomy with his award-winning work with statistical astronomy and later astrometry, the study of the precise positions of stars. Van de Kamp focused on precisely measuring the visible wobble of binary star systems. By taking successive snapshots of the stars over a period of years, he could meticulously trace out the orbits of the two stars around each other, working out their masses and orbital separation. This works even if one of the objects is too dim to see – the wobble from one star gives away the mass the position of the other star. Van de Kamp then surmised that if he looked at a star that was close enough to the earth, the wobble of even a low mass object around that star would show up on his photographic plates. A low mass object… like a planet.
It didn’t’ take long for Van de Kamp to find his best candidate: Barnard’s Star. It’s the fourth closest star to us at only 6 light-years from earth, and it’s a red dwarf, which meant its mass was a seventh that of the sun, making any planet’s pull that much more obvious. If there were planets invisibly orbiting Barnard’s Star, he was convinced he could see it happening in slow motion over the course of many years.
24 inch (61 cm) refractor at Sproul Observatory
So beginning in 1938, Van de Kamp began taking pictures of Barnard’s Star with the 24 inch refracting telescope at Sproul Observatory at Swarthmore College, where he had been named Director the year before. Almost every night the observatory was open and the skies were clear, the light from Barnard’s Star’s small dot and the other stars that happend to be in the camera’s field were chemically imprinted on the emulsion of large photographic plates. Van de Kamp and his assistants developed the plates, and Barnard’s Star’s position was painstakingly measured with respect to the stars around it. But the motions of the rotation of the earth as it orbited the sun had to be accounted for, and removed from the calculations. And what was left over would be the wobble due to any unseen companion. But this leftover motion was extremely small – at the limit of detection of Van de Kamp’s Philadelphia-area based telescope; this was at the cutting edge of astrometry.
Six years of almost daily images and measurements piled up, and in 1944, Van de Kamp surprised the world by announcing that Barnard’s Star indeed had a substellar companion a whopping 60 times the mass of Jupiter. Van de Kemp kept observing the star after the announcement at a pace of about 100 images a year. By the time of the 1963 meeting of the American Astronomical Society meeting in Tucson, Arizona, Van der Kamp was armed with more than 2400 images, and new wobble calculations based on them. Van De Kamp’s object went from 60 Jupiter masses to just 1.6 Jupiter masses, orbiting Barnard’s Star in 24 years. A true planet!
Van de Kamp's 1969 planet's wobble (note the big jump at ~1950) From Richard Nugent's website.
But astronomers at the meeting were skeptical. According to Van De Kamp’s observations, the planet had a very elliptical orbit, something very different than the nearly circular orbits of the planets in our own solar system. As the years and observations and measurements piled up, the planet’s orbit became even more elliptical, worrying even Van de Kamp. In 1969, Van de Kamp announced that he has solved the problem of the highly elliptical orbit – by removing the planet entirely, and replacing it with two planets, approximately a Jupiter mass each, orbiting Barnard’s Star once very 12 and 26 years. These two planets interacting with the star together would reproduce the wobble Van De Kamp had observed. We suddenly now had two extrasolar planets joining the 9 of our own solar system, and man was only just landing on the moon.
But the case for Van de Kamp’s planets soon started to show serious cracks. John Hershey, a colleague at Sproul Observatory, started looking for wobbles in another low-mass candidate, Gliese 793, whose images were obtained for the past few decades alongside Barnard’s Star. Amazingly enough, he found the exact same wobble that Van De Kamp found in Barnard’s Star. Surely, Gliese didn’t have the exact same planetary system pas Barnard’s Star! The only reasonable explanation was some previously unseen effect of the telescope. Key events in the wobble both stars detected correlated with two key dates: 1949 and 1957, and sure enough, both were dates when the telescope was undergoing maintenance, and the main lenses in the telescope had been removed and replaced, respectively. The image of Van de Kamp’s planets dimmed.
Pittsburgh's Allegheny Observatory by Jim Fotia
In the early 70s, George Gatewood was a was a young researcher at the University of Pittsburgh’s Allegheny Observatory located among the steep hills near downtown Pittsburgh. Gatewood was interested in characterizing the unique instrumental errors in the various telescopes in the world who carried out astrometric observations, so that photographs between telescopes could be shared between studies. So he and his advisor from The University of South Florida, Heinrich Eichhorn, happened to have more than 200 photograph of Barnard’s Star from Allegheny Observatory from 1916 to 1971. In addition, the Observatory’s Director Nicholas Wagman had confided in Gatewood that his own data suggested that the Barnard’s Star planets were instrumental phantoms. But Wagman refused to publish his data, and suggested Gatewood collect new observations.
Dr. George Gatewood
Gatewood initially had no interest in disproving the existence of Van de Kamp’s planets. In fact, Gatewood actually met the renown astronomer at a conference in 1966, and expressed his admiration for Van de Kamp’s work. But after two strong requests from Wagman, the graduate student and his advisor took up the task of independently verifying the nearby world. They had less images than Van de Kamp, but they had a better technique for reducing the star’s natural motion through the sky, and used eleven reference stars to pinpoint Barnard’s Star’s exact location on the photograph, compared to Van de Kamp’s three. The project became Gatewood’s 1972 PhD. dissertation, and the title says it all: “An Unsuccessful Search for a Planetary Companion around Barnard’s Star BD +4°3561″ The only two planets outside our solar system suddenly vanished for everyone.
Gatewood and Eichhorn's motion of Barnard's star is plotted as points, with the size of the points weighted. The dashed line represents van de Kamps' claimed orbit, while the straight line is the motion of a star with no planet. Thanks to Richard Nugent's great website.
That is, for all except Van de Kamp. He defiantly continued to believe in his planets even in the face of the slam-dunk evidence against them. That year, Peter van de Kamp retired from Swarthmore, and returned to the Netherlands. He later claimed to have found more planets, this time around the nearby sun-like star Epsilon Eridani, but that claim was likewise disproven over time as well (but other planets were “refound” just a few years ago by radial velocity! I haven’t read yet if there is any correlation between these radial velocities and vdK’s residuals. Probably a coincidence?). There are indications that Van de Kamp felt persecuted by the astronomical community. The determined astronomer held on to his worlds all the way until his death in 1995 at the age of 93.
George Gatewood met with Van de Kamp again shortly before his death, where the elder astronomer continued to insist that his planets were indeed real. He then suggested that Gatewood should stop looking for errors in other peoples data, and take the risk of making some observations of his own.
Peter van de Kamp
Gatewood must have taken the advice to heart. Just a year after Van de Kamp’s death, Gatewood announced that one of the stars he had previously cleared of planets in 1972, Lalande 21185, which he then restudied in 1992 with the aid of lasers (no planets again), but now upon a third look, had the signature of two planets. Gatewood knew all to well what kind of scrutiny such an announcement would be subjected to, so was extra careful in eliminating all other possible measurement and instrument errors in his calculations. Gatewood might never have publicly made his planetary birth announcement if it were not for the excitement that was flowing through the astronomical community at the time. The first extrasolar planets had been confirmed around the sun-like star 51 Pegasai by using a method of detecting wobbles using the spectrum of the star, making it much more sensitive to massive planets that go around their sun very quickly. It seems that the golden age of new world discovery was really here.
So Gatewood unleashed his planets out onto a world much friendlier to exoplanets. One of the first tests for Gatewood’s progeny came when Dr. Geoff Marcy and his team used their proven planet-finding radial velocity technique to observe Lanane 21185. Not only did Marcy not find any planets, he held up the spectra of Gatewood’s star as a perfect example of a normal M-dwarf star with no wobbling! The new science essentially eliminating the possibility of Gatewood’s planets.
Although Gatewood’s Planets joined Van De Kamp’s planets in being incinerated by the scientific crucible, the radial velocity method finally satisfied our desire to truly know that the planets were out there. Peter Van De Kamp predicted that the Universe was teeming with other worlds, something that the radial velocity planet hunters proved decades later.
The extrasolar planet count is currently at 424, and set to go into the thousands over the next 10 years. The few original worlds given to us seem now like long exorcised astronomical ghosts. But for so long, they were all we had, birthed after long, laborious, manual work over decades. At least for some who lived through that era, and the champions who held on to them with such passion, Barnard’s Star’s planets are even more real than the dozens discovered since.
January 25th, 2010 at 5:17 pm
Loved this story! But thanks for stealing the title to the book I’ve been working on since I was a junior in college….
(Oh well…after 18 years, it’s not like I was ever really going to finish it or anything.) LOL
PS: I got to introduce the staff last week to Aural Moon. Thought it was pretty cool that I can listen to it now while I’m in the office.
January 25th, 2010 at 7:45 pm
Tricia,
Thanks! You’ve been working on a book called The Planet Killers?? Do tell! What’s it about? Is there a planet fatale? You have to finish it now!!
Very cool about Aural Moon! I’ll try to remember to email you the high-quality stream address, so you can listen at 128k and hear every gong and glockenspiel.
January 25th, 2010 at 7:57 pm
People on the Internet keep saying that the reclassification of Pluto caused a huge public outcry, but for those of us not living in North America, it didn’t. (It did ignite public interest, but more curiosity than conflict in my experience.)
I had thought that maybe this was because of a cultural resistance to change (c.f. the fact that, unlike us obviously-more-civilised Australians, America has never adopted the metric system), but then I heard the episode of the “Are We Alone?” podcast in which it is argued that America’s sentimental attachment to Pluto is all the fault of a certain cartoon dog.
January 25th, 2010 at 10:52 pm
Adrian,
Thats a good point – the Pluto uproar does seem to be very U.S-centric.
I’m not altogether certain that we can really blame the Disney character for America’s attachment to Pluto. Of all the Disney characters, Pluto is one of the least popular, I’m willing to bet.
My guess is that the Pluto uproar has to with the anthropomorphizing of the planets in our solar system dating back to who knows when. To many, Pluto was a little guy way out there at the edge of the system – the somehow “his” position in the solar system and the planet’s smallness combined to create an image for many people.
So when he was portrayed as being “kicked out” of the solar system, many saw it as the big authoritarians picking on the little guy. It really is a fascinating dynamic – I would love to find a study about the phenomenon. I think it says something about how people perceive scientists and their relation to being overbearing authority figures that it does anything.
February 2nd, 2010 at 1:19 am
There are several misconceptions here. First, our solar system does not have only eight planets. Only four percent of the IAU voted on the controversial demotion, and most are not planetary scientists. Their decision was immediately opposed in a formal petition by hundreds of professional astronomers led by Dr. Alan Stern, Principal Investigator of NASA’s New Horizons mission to Pluto. One reason the IAU definition makes no sense is it says dwarf planets are not planets at all! That is like saying a grizzly bear is not a bear, and it is inconsistent with the use of the term “dwarf” in astronomy, where dwarf stars are still stars, and dwarf galaxies are still galaxies. Also, the IAU definition classifies objects solely by where they are while ignoring what they are. If Earth were in Pluto’s orbit, according to the IAU definition, it would not be a planet either. A definition that takes the same object and makes it a planet in one location and not a planet in another is essentially useless. Pluto is a planet because it is spherical, meaning it is large enough to be pulled into a round shape by its own gravity–a state known as hydrostatic equilibrium and characteristic of planets, not of shapeless asteroids held together by chemical bonds. These reasons are why many astronomers, lay people, and educators are either ignoring the demotion entirely or working to get it overturned.
Second, opposition to the demotion is not limited to Americans, and it is not due to the Disney dog. I am a graduate student in astronomy at Swinburne University and for three and a half years have run a blog advocating the overturning of the demotion. As stated above, there are strong scientific reasons for opposing the demotion and supporting a broader planet definition that includes any non-self-luminous spheroidal body orbiting a star. There are many exoplanets with eccentric orbits, some systems with two planets that cross one anothers’ orbits, and these are giant planets. According to the IAU definition, none would be classed as planets. Also, the reason often cited in support of demotion, that we need to keep the number of planets low so kids can memorize them, is not scientific either. The universe was not designed for our convenience, and memorization is not even that important for learning. Why not instead establish subcategories to distinguish different types of planets? Dwarf planets would simply be a third class, in addition to terrestrials and jovians, that are planet due to their being in hydrostatic equilibrium but are of the dwarf subcategory because they don’t gravitationally dominate their orbits.
Mike Brown has chosen to embrace the “Plutokiller” role in spite of the fact that he was for dwarf planets being considered a class of planets before he was against it. He also distorts the facts when he erroneously claims there is no more debate, and that there are only a few holdouts who reject the IAU definition. This is completely untrue. I am a member of many Internet groups and correspond with many people all over the world who reject the IAU definition just as much as some Americans do. Many of these people are amateur astronomers and astronomy students who already have an interest in the solar system.
Brown tweets, “‘I just persuaded a group doing a solar system scale model to not include Pluto as the 9th planet. My work is never done.’”
Well, MY work is never done either. I have spent the last three and a half years persuading children, students, planetariums, etc. to keep Pluto in and to add the other four dwarf planets, Ceres, Haumea, Makemake, and Eris as well. For more good arguments in favor of a broad planet definition, read “The Case for Pluto” by Alan Boyle and visit my “Laurel’s Pluto Blog.”
February 15th, 2010 at 5:40 pm
“The determined astronomer held on to his worlds all the way until his death…”
That is a very moving and profound sentence. You’re a fantastic writer. I really hope someday you’ll write for an astronomical magazine — maybe in the way James Kaler does.
But that sentence clearly sums up how history remembers you. In my own life, I strive to be like Kepler; who, when the time came, was able to take his deepest beliefs and cast them away in the face of his own data. And for that, Newton called him a giant.
Better data means a better understanding. Either you’re beliefs are supported or refuted. Clyde Tombaugh was a really nice guy, but Pluto doesn’t act or look like any other planet. It does look an awful lot like a Kuiper Belt Object, though. Time to let go of our worlds. @Lauren, let it go.
February 16th, 2010 at 6:56 am
Terry – thanks! Your customary wad of cash is in the mail!
There are interesting things about Pluto on either side of the argument, to be sure – astronomers are known to keep designations or systems based on historical precedent (like keeping the magnitude or the color system), so keeping Pluto a planet probably would have been just fine, considering all the work they had to go through just to make a new definition of a planet that applied only to our solar system anyway.
But at the same time while Eris, Haumea, Makemake are different from Pluto in their location in the solar system and even composition in some cases, they share many of their qualities. Eris IS larger than Pluto. But as they say, it’s not just the size that matters when making classifications.
In any case, the IAU definition of a planet is flawed, and it must be revised at some point in the future.
May 1st, 2010 at 12:11 pm
Excellent account of the “discovery” and “disappearance” of van de Kamp’s extrasolar planets. By the way, he was a good friend of the humorous musician Peter Schickele, also known as PDQ Bach, who wrote a song about him.
May 29th, 2010 at 1:35 pm
@Infinitewell First, my name is Laurel, not Lauren.
I absolutely will NOT let it go. Maybe you should tell Mike Brown to “let go” of his insistence that he killed Pluto. There is no data that confirming that Pluto is not a planet; there is only interpretation of existing data. That interpretation is based on a very narrow view of what a planet is and how it behaves.
Pluto does look like a planet in one key way–it is spherical, meaning it is massive enough to be rounded by its own gravity, a state known as hydrostatic equilibrium. The overwhelming majority of Kuiper Belt Objects are way too small to do this (with the known exceptions of Haumea, Makemake, and Eris). Pluto is also 75 percent rock and almost certainly geologically differentiated. That sure looks a lot like a planet to me and to many astronomers.
It is not that the data refutes Pluto being a planet; it is that the data tells us that we need to recognize there are more types of planets than we thought. Most exoplanets we’ve found look and act much less like the planets of our own solar system than does Pluto. One orbits its star backwards; one has an extremely comet-like orbit around its star; one formed directly from a molecular cloud the way stars do and unlike the way planets do.
Pluto is both a planet and a Kuiper Belt Object. I don’t know why so many people have such a hard time understanding this.
And no one should “let go” of opposition to a definition that is highly flawed and based more on one interpretation of the data in an ongoing debate than on the data itself.
July 17th, 2011 at 4:37 pm
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I would like credit for my photo of George Gatewood. It was taken in his office in the Allegheny Observatory in the spring of 1982 when he was developing the Multichannel Astrometric Photometer to hunt for exo-planets.
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