Clyde Tombaugh’s Ten Special Commandments for Planet Hunters


Back in 1989, amateur astronomer Toney Burkhart found out that Clyde Tombaugh was going to be giving a talk in San Francisco, just a short distance from Burkhart’s home. Trouble was, he found out only about 10 minutes before the presentation was going to start, so he rushed over and arrived just in time to hear Tombaugh’s talk, where he told amusing stories of how he found Pluto, and what he went through with night after night in a cold observatory taking photographs and comparing the glass plates, looking for a planet in the outer solar system. Then Tombaugh shared read his version of the Ten Commandments, called, “Ten Special Commandments for a Would-Be Planet Hunter.”

Afterward, the posters of the Commandments were being sold as a fund raising event.

“Clyde was going around the country to raise money for scholarships for young people to study planetary science,” Burkhart told Universe Today. “There were a lot of people there in the lobby buying posters autographed by Clyde Tombaugh and I wanted one very much.”

However, when Burkhart went to purchase one, he discovered that in his haste to leave his home, he had forgotten his billfold.

“I waited until everything was over and thought that I would at least go over and say hi to Clyde and tell him how much I thought of his hard work and to shake his hand, at least,” Burkhart said, and Tombaugh was more than happy to chat with an fellow astronomy enthusiast.

“While I was chatting with Clyde, I told him that I wish I brought money to buy one of the posters. He looked at me and smiled and said, ‘Well, that’s alright.’” And I said no, I really would have bought one if I had not ran out of the house and forgot my billfold. He was holding his notes and I asked him, what are you going to do with those notes, throw them away?”

Burkhart said Tombaugh smiled and replied that he couldn’t give away his notes, as he had more talks to give, but said he could mail them to Burkhart after his tour was over.

Burkhart offered to send Tombaugh a check later, or at least pay for postage, but Tombaugh looked at him and said, “No, that’s OK, I see you are really into astronomy and it would be my pleasure to give it you.”

Grateful, Burkhart asked if Tombaugh could autograph it, not for Burkhart but for his son Jason. Tombaugh took Burkhart’s address, and true to his word, about a month later Burkhart received Tombaugh’s personal version of the Commandments, with corrections made in pen, (the corrections were made by Tombaugh’s wife, Patricia, Burkhart said) along with his autograph. “I have them in safekeeping to leave to my son to have and hopefully give them to his kids,” Burkhart said.

Here are the the Ten Special Commandments for a Would-Be Planet Hunter, according to Clyde Tombaugh

1. Behold the heavens and the great vastness thereof, for a planet could be anywhere therein.

2. Thou shalt dedicate thy whole being to the search project with infinite patience and perseverance.

3. Though shalt set no other work before thee for the search shall keep thee busy enough.

4. Though shalt take the plates at opposition time lest thou be deceived by asteroids near their stationary positions.

5. Though shalt duplicate the plate of a pair at the same hour angle lest refraction distortions overtake thee.

6. Thou shalt give adequate overlap of adjacent plate regions lest the planet play hide and seek with thee.

7. Thou must not become ill in the dark of the moon lest thou fall behind the opposition point.

8. Thou shalt have no dates except at full moon when long exposure plates cannot be taken at the telescope.

9. Many false planets shall appear before thee, hundreds of them, and thou shalt check every one with a third plate.

10. Thou shalt not engage in any dissipation, that thy years may be many for thou shalt need them to finish the job!

Clyde W. Tombaugh
14 March 1989

Burkhart shared the scan of Tombaugh’s notes on his Facebook page.

h/t to Charles Bell.

New Horizons Flies by Uranus

The Pluto-bound New Horizons spacecraft will fly by another planet today (March 18, 2011). However, the robotic craft won’t be taking any images as it zooms past Uranus’ orbit at about 6 p.m. EDT, 3.8 billion kilometers (2.4 billion miles) away from the gas giant (and 2.0 billion km (1.8 billion miles) from Earth). New Horizons is currently in hibernation mode, and the great distance from Uranus means any observations wouldn’t provide much as far as data and images. But, even so, this event is a ‘landmark’ so to speak in New Horizon’s gauntlet across the solar system.

“New Horizons is all about delayed gratification, and our 9 1/2-year cruise to the Pluto system illustrates that,” said Principal Investigator Alan Stern, of the Southwest Research Institute. “Crossing the orbit of Uranus is another milepost along our long journey to the very frontier of exploration.”


New Horizons is now well over halfway through its journey to Pluto. Motoring along at 57,900 km/hr (36,000 mph), it will travel more than 4.8 billion km (3 billion miles) to fly past Pluto and its moons Nix, Hydra and Charon in July 2015.

But the journey doesn’t end there. After that, New Horizons will head off to a post-Pluto encounter with other objects within the Kuiper Belt, some event(s) which might take place even into the 2020’s. The planetary science community is working on the selection of potential targets.

The mission still has more than 4 years to go to get to Pluto; it will take 9 nine months to send all the data back to Earth.

The next planetary milestone for New Horizons will be the orbit of Neptune, which it crosses on Aug. 25, 2014, exactly 25 years after Voyager 2 made its historic exploration of that giant planet.

“This mission is a marathon,” says Project Manager Glen Fountain, of the Johns Hopkins University Applied Physics Laboratory. “The New Horizons team has been focused on keeping the spacecraft on course and preparing for Pluto. So far, so good, and we are working to keep it that way.”

Source: New Horizons

Stellar Occultation by Eris

On November 6, 2010, the dwarf planet Eris occulted a faint 16 magnitude star and this was the first time astronomers were able to witness an occultation by Eris. Additionally, at 96.6 Astronomical Units away, it was the most distant object for which this kind of occultation — where one astronomical object passes in front of another — had been seen. Why was this dim, distant event important? It has helped refine the size of what is (was?) thought to be the biggest dwarf planet (yes, I know, an oxymoron) we know of.

“Most of the ways we have of measuring the sizes of objects in the outer solar system are fraught with difficulties,” wrote astronomer and discoverer of Eris, Mike Brown, on his website ‘Mike Brown’s Planets.’ “But, precisely timed occultations like these have the potential to provide incredibly precise answers.”
Continue reading “Stellar Occultation by Eris”

What is a Plutoid?

About Dwarf Planets


Pluto, we hardly knew ya! Don’t worry, she’s not going anywhere. However, this once happy planet will no longer be listed amongst the “planets” in our solar system. According to International Astronomical Union (IAU), which began meeting in August of 2006, the term Plutoid now applies to Pluto, as well as any other small stellar body that exist beyond the range of Neptune. Arriving at this working definition in 2008, two years after first meeting, the IAU defines the term Plutoids thusly: “Plutoids are celestial bodies in orbit around the Sun at a semimajor axis greater than that of Neptune that have sufficient mass for their self-gravity to overcome rigid body forces so that they assume a hydrostatic equilibrium (near-spherical) shape, and that have not cleared the neighbourhood around their orbit.”

The reason the IAU began meeting in the first place was to iron out some ambiguities that exist in the terminology of astronomy. For example, thought some might find it shocking, astronomers had never actually come up with a definition of “planet”. Originally, a planet meant a “wandering star” – ie. a star that appeared to move from constellation to constellation. This was the definition used by ancient astronomers, and it applied to the sun and moon as well. However, Copernicus’s heliocentric model changed all that; now it was clear that the Earth was a planet itself and moved around the Sun with the rest of them. In addition, more and planets were being discovered beyond Jupiter, such as Uranus and Neptune, and then between Jupiter and Mars. This included Ceres, Pallas, Vesta, and Juno, but astronomers soon realized that these bodies were far too small to fit with the rest of the planets.

Then came Pluto’s discovery. At the time, scientists thought it to be several times larger than it actually was; accordingly they placed it on the list of planets. Eventually, its true size was realized and other bodies similar to Pluto in size and composition were found far beyond Neptune, in what is known as the Kuiper Belt. Pluto was to these stellar objects what Ceres was to large objects in the asteroid belt – that is to say, comparable in size. Astronomers proposed several names for these objects, but matters did not come to a head until Eris was discovered. This dwarf planet was actually larger than Pluto, 2500 km in diameter, making it twenty-seven percent larger than Pluto.

In the end, the IAU could only resolve this matter by removing Pluto from the list of planets and devising a new category for dwarf planets that could no longer be considered true planets. Plutoid was the result, and now applies to the trans-Neptunian objects of Pluto, Haumea, Makemake, and Eris.

We have written many articles about Plutoid for Universe Today. Here are some facts about Pluto, and here’s an article about why Pluto is no longer a planet.

If you’d like more info on Pluto, check out Hubblesite’s News Releases about Pluto, and here’s a link to NASA’s Solar System Exploration Guide to Pluto.

We’ve also recorded an episode of Astronomy Cast dedicated to Pluto. Listen here, Episode 64: Pluto and the Icy Outer Solar System.


Eris and Pluto: Two Peas in a Pod

About Dwarf Planets


Or two dwarf planets in the Kuiper Belt…

Eris — that pesky big dwarf planet that caused all the brouhaha about planets, dwarf planets, plutoids and the like — has gotten a closer look by a team of astronomers from several different universities, and guess what? Eris and Pluto have a lot in common. Eris appears to have a frozen surface, predominantly covered in nitrogen ice and methane, just like Pluto.

The scientists integrated two years of work conducted in Northern Arizona University’s new ice research laboratory, in addition to astronomical observations of Eris from the Multiple Mirror Telescope Observatory from Mount Hopkins, Ariz., and of Pluto from Steward Observatory from Kitt Peak, Ariz.

“There are only a handful of such labs doing this kind of work in the world,” said Stephen Tegler, from NAU and lead author of “Methane and Nitrogen Abundances on Eris and Pluto,” which was presented this week at the American Astronomical Society’s Divison of Planetary Science meeting. “By studying surfaces of icy dwarf planets, we hope to get a better understanding of the processes that affect their surfaces.”

NAU’s ice lab grew optically clear ice samples of methane, nitrogen, argon, methane-nitrogen mixtures, and methane-argon mixtures in a vacuum chamber at temperatures as low as minus 390 degrees Fahrenheit to simulate the planets’ cold surfaces. Light passed through the samples revealed the “chemical fingerprints” of molecules and atoms, which were compared to telescopic observations of sunlight reflected from the surfaces of Eris and Pluto.

“By combining the astronomical data and laboratory data, we found about 90 percent of Eris’s icy surface is made up of nitrogen ice and about 10 percent is made up of methane ice, which is not all that different from Pluto,” said David Cornelison, coauthor and physicist at Missouri State University.

The scientists say the recent findings will directly enhance NASA’s New Horizons spacecraft mission, currently scheduled to fly by Pluto in 2015, by lending greater value to the continued research of Eris and Pluto.

Source: Northern Arizona University, DPS

New Horizons Mission Practices Telescopic Imager on Pluto’s Twin


This summer, the New Horizons spacecraft was awoken for its annual systems checkout, and took the opportunity to exercise the long range camera by snapping pictures of Neptune, which at the time, was 3.5 billion km (2.15 billion miles) away. The Long Range Reconnaissance Imager (LORRI) snapped several photos of the gas giant, but Neptune was not alone! The moon Triton made a cameo appearance. And the New Horizons team said that since Triton is often called Pluto’s “twin” it was perfect target practice for imaging its ultimate target, Pluto.

This image gets us excited for 2015 when New Horizons will approach and make the closest flyby ever of Pluto.

“That we were able to see Triton so close to Neptune, which is approximately 100 times brighter, shows us that the camera is working exactly as designed,” said New Horizons Project Scientist Hal Weaver, of the Johns Hopkins Applied Physics Laboratory. “This was a good test for LORRI.”

Weaver pointed out that the solar phase angle (the spacecraft-planet-Sun angle) was 34 degrees and the solar elongation angle (planet-spacecraft-Sun angle) was 95 degrees. Only New Horizons can observe Neptune at such large solar phase angles, which he says is key to studying the light-scattering properties of Neptune’s and Triton’s atmospheres.

“As New Horizons has traveled outward across the solar system, we’ve been using our imagers to make just such special-purpose studies of the giant planets and their moons because this is a small but completely unique contribution that New Horizons can make — because of our position out among the giant planets,” said New Horizons Principal Investigator Alan Stern.

Triton is slightly larger than Pluto, 2,700 kilometers (1,700 miles) in diameter compared to Pluto’s 2,400 kilometers (1,500 miles). Both objects have atmospheres composed mostly of nitrogen gas with a surface pressure only 1/70,000th of Earth’s, and comparably cold surface temperatures approaching minus-400 degrees Fahrenheit. Triton is widely believed to have been a member of the Kuiper Belt (as Pluto still is) that was captured into orbit around Neptune, probably during a collision early in the solar system’s history.

Source: New Horizons

Pluto Goes into the Dark


Last week, Pluto passed in front of what looks like a dark patch in the sky, and astrophotographer John Chumack was ready to capture the event. The dark patch is actually Barnard 92, a dark nebula. Since Pluto is usually very hard to see among the background of stars, it stands out against this dark nebula which blocks out the background stars. Still, Pluto – distant and dim as it is – is just a faint point of light, so John took special measures. “Although Pluto was easily visible in a short 5 minute exposure, I took an hour exposure to show the Dark nebula and the ‘rich & pretty’ surrounding star field,” he said.

The image was taken from John’s observatory in Yellow Springs, Ohio, using his homemade 16” Newtonian telescope and a QHY8CCD single shot color camera, captured from 01:00am until 02:00 am E.S.T. on July 6, 2010. Pluto and B92 sits within the large Sagittarius Star Cloud, M24.

Great shot, John! For more wonderful astronomical images, check out John’s website, Galactic Images.

New Hubble Images Show Pluto is Changing

Pluto-philes (and astronomers, too) have always bemoaned the fact that the best image of the principal dwarf planet wase just a fuzzy, pixelized haze. Bemoan no more. The most detailed look to date of the entire surface of Pluto has been constructed from hundreds of images taken by the Hubble Space Telescope. The images were taken during 2002 to 2003, and it took four years of computer crunching and software tweaking to create the global images. Surprisingly, the images show Pluto changed noticeably during the two-year photo shoot; the dwarf planet’s color became “redder,” and astronomers could see Pluto’s ice sheets were shifting.

“These Hubble pictures represent a true-color appearance of what you would see if you were near Pluto, comparable to looking at our own Moon with the naked eye,” said principal investigator Marc Buie of the Southwest Research Institute. “We now know we’re looking at something that has the biggest surface changes of any object in our solar system.”

The pictures show nitrogen ice growing and shrinking, getting brighter in the north and darker in the south.

Buie and planet hunter Mike Brown from Caltech introduced the Hubble images during a teleconference with reporters today, and emphasized how surprised they were with the changes seen on Pluto in just a relatively short period of time. Even accounting for seasonal changes, seasons can last 120 years in some regions of Pluto.

The top picture was taken in 1994 by the European Space Agency’s Faint Object Camera. The bottom image was taken in 2002-2003 by the Advanced Camera for Surveys. The dark band at the bottom of each map is the region that was hidden from view at the time the data were taken. Credit: NASA, ESA, and M. Buie (Southwest Research Institute)

They said the images underscore that Pluto is not simply a ball of ice and rock but a dynamic world that undergoes dramatic atmospheric changes. While they believe the changes are driven by the seasons, it may mostly come from how quickly things can change on Pluto. The seasons are propelled as much by the planet’s 248-year elliptical orbit as its axial tilt — unlike Earth where the tilt alone drives seasons. On Pluto spring transitions to polar summer quickly in the northern hemisphere because Pluto is moving faster along its orbit when it is closer to the Sun.

“If Earth had such an extreme orbit, and we were experiencing a nice springtime day with 60-70 degree F temperatures, as the orbit changed it could suddenly drop to -90 degrees F,” said Brown.

There is also a mysterious bright spot on the center of Pluto, which has been observed in earlier images. But the spot is unusually rich in carbon monoxide frost.

Click here to see a video of Pluto rotating.

The astronomers said Pluto is so small and distant that the task of resolving the surface is as challenging as trying to see the markings on a soccer ball 40 miles away. Buie said we won’t have a better look at Pluto until the New Horizon’s spacecraft is six months away from the dwarf planet in 2015.

The images were taken with the Advanced Camera for Surveys on HST, and the 348 images taken in 2002 and 2003 were the last ones taken of Pluto with high enough resolution to be useful. “I had time allocated two years ago to look at Pluto, which came just three or four weeks after the high resolution camera failed,” Buie. “That was very disappointing.”

But the images do show Pluto is significantly redder than it had been for the past several decades. Astronomers use the word “red” to mean it reflects more red light than blue or green light. To the human eye, Pluto has a yellowish-orange color, and is about 20% redder than it used to be. “It’s not as red as the surface of Mars, but more red than Io,” Buie said.

Red is usually associated with carbon. The astronomers said there is also methane, which is not usually stable in an environment like Pluto’s.

“This business about the color change had me scared for awhile,” Buie confessed. “I got the result years ago, but it was so hard to understand and believe. I’m still nervous about it. It could be that I completely screwed this up, but I can tell you Charon is on the same images, and Charon has the same color throughout but Pluto changed. I don’t’ know how the camera system on HST could have given me the wrong colors on Pluto.”

This was previously the best image of Pluto, taken in 2000 by HST. Credit: Eliot Young (SwRI) et al., NASA

Someone suggested that Pluto is reddening because of its recent demotion from full planethood. “Yes, people have said that Pluto is mad at me,” said Brown, who has the nickname of the “Pluto killer” because he discovered other Kuiper Belt objects which led to the new class of dwarf planets.

“For a long time Pluto was this lonely oddball that we didn’t have anything else to compare it with,” said Brown. “Understanding this all as a new class of objects is a much more interesting way of looking at the solar system and it is quite a bit of fun, too.”

More information from Buie’s webpage on the Pluto images.

The paper about the images isn’t posted online yet, but it will be up on this webpage soon.

Source: Conference call.
Additional images and info from NASA

New Horizons Spacecraft Now Closer to Pluto Than Earth

Fastest Spacecraft


The New Horizons spacecraft crossed a milestone boundary today: it is now closer to its primary destination, Pluto, than to Earth. But New Horizons –the fastest man-made object — is not yet halfway to the dwarf planet. That won’t happen until February 25, 2010. New Horizons is now 1,440 days into its 9.5-year journey and well past 15 AU (astronomical units) from the Sun. But there is a long haul yet to go: there are still 1,928 days until operations begin for the close encounter, and 2022 days until the spacecraft reaches the closest point to Pluto in the summer of 2015. It is exciting to think what we will learn about Pluto and the Kuiper Belt in five and a half years. Will our perspectives change? Hard to believe they won’t.

New Horizons is currently traveling at about 50,000 kph (31,000 mph) (relative to the Sun) and is located about 2.4 billion kilometers (1.527 billion miles) from Earth.

The spacecraft launched in January 2006.

New Horizons will be taken out of hibernation in early January to repoint the communications dish antenna to keep up with the changing position of the Earth around the Sun. It was last awoken in November to download several months of stored science data from the Venetia Burney Student Dust Counter, to correct a recently discovered bug in the fault protection system software, (last thing anyone wants is to have the spacecraft go into safe mode at closest approach), and to upload instructions to run the spacecraft through early January. Telemetry shows that New Horizons is in very good health and almost exactly on its planned course.

Principal Investigator Alan Stern wrote in his last PI’s Perspective notes that the science team will meet in January to discuss which Kuiper Belt Objects they hope to “fly by and reconnoiter after Pluto. Those searches will begin next summer and continue through 2011 and 2012. Hopefully, they’ll net us four to 10 potential targets.”