March 13, 1930: Clyde Tombaugh’s discovery of Pluto announced

pluto_chicago dailyIn early 1930, Pluto was discovered by a farm boy from Kansas with no formal training in astronomy. The announcement in March of Pluto’s discovery was a moment of excitement for both scientists and the public.

Clyde Tombaugh was born on February 4, 1906 in Illinois, and grew up on a farm in Kansas. He became interested in astronomy as a teenager after observing craters on the moon and rings around Saturn through his uncle’s three inch telescope. The family soon ordered a better telescope to encourage their son’s interests. When he was 20, Clyde Tombaugh began building his own telescopes.

By 1928 Tombaugh had built his third backyard telescope and used it to make drawings of Mars and Jupiter. He sent these to Vesto M. Slipher, the director of the Lowell Observatory in Flagstaff, Arizona, asking for comments. After a short correspondence, Slipher offered him a job at the observatory. His task would be to search for “Planet X.”

Clyde W. Tombaugh at the door of the Pluto discovery telescope, Lowell Observatory, Arizona (Photo courtesy of Lowell Observatory Archives)

Clyde W. Tombaugh at the door of the Pluto discovery telescope, Lowell Observatory, Arizona (Photo courtesy of Lowell
Observatory Archives)

Planet X had been predicted by Percival Lowell. Lowell, a businessman and astronomer known for his belief that a network of canals existed on Mars and was evidence of an intelligent alien civilization, built the Lowell Observatory to prove his theory. But as it became more and more clear that there was no evidence for that theory, he began to focus on searching for a new planet. Lowell had observed some peculiarity in the orbits of Neptune and Uranus and figured there must be another planet with a mass comparable to Neptune’s orbiting the sun beyond Neptune. Lowell searched for the planet, which he called Planet X, from 1905 to his death in 1916.

For years after Lowell’s death, the Lowell observatory was hampered by an expensive legal battle with Lowell’s widow. In 1927 the observatory was ready to resume the search for Planet X, and it acquired a new 13 inch refracting telescope for the search.

Slipher assigned the task to Tombaugh, who arrived in Flagstaff in January 1929. First, he had to use the telescope to make many photographic plates, systematically taking pictures of regions of the night sky where the new planet might appear. For each region, Tombaugh made two photos, taken several days apart. He spent many cold nights in the unheated observatory dome carefully making the observations.

After creating many such pairs of plates, he would compare the two members of each pair. Distant stars would appear in the same position on both plates, but a planet would have moved in the several days between the two exposures. Tombaugh used a device called a blinking comparator to make the comparison. The device would present him with sections of the two photo plates to be compared, shifting between the two several times a second. Most of the time the photos were the same and Tombaugh would see nothing, but if an object had moved between the two exposures, Tombaugh would see a blink.

It was incredibly tedious work requiring intense concentration, but Tombaugh greatly preferred it to going back to work on the farm, so he persisted.

After months of searching, he had found several asteroids, but nothing that fit the criteria for Planet X. Finally, in February 1930, while scanning the plates he had taken a few weeks earlier, he saw something that moved. He determined that the object had moved about 3 mm on the plates between the two exposures, indicating an orbital distance of about 40-43 AU, putting it outside the orbit of Neptune at about the right place to be the predicted planet.

Tombaugh told Slipher he had found Planet X, and on March 13, 1930, the Observatory announced the finding of the new object. The announcement date was chosen to coincide with both the anniversary of Herschel’s discovery of Uranus in 1781 and Percival Lowell’s birthday in 1855.

The public and astronomers were enthusiastic about the new planet. Later that month the object was officially named Pluto, after the Roman god of the underworld, who could make himself invisible. The name was suggested by an 11 year old girl in England. A secondary reason for the name was that the first two letters are Percival Lowell’s initials.

Though exciting, the planet was tiny, just a dot on the photograph, and some astronomers doubted whether it was massive enough to affect the orbit of Uranus and Neptune.

Pluto’s mass was not known until 1978, when its moon Charon was discovered. Pluto’s mass is about 0.002 that of Earth, making it much too small to influence the orbit of Neptune.

Ultimately, Pluto lost its planet status. Other objects in the neighborhood of Pluto have been discovered in recent years, including several comparable in size to Pluto. In 2006, much to the disappointment of children around the world, the International Astronomical Union redefined the term “planet.” The new definition of a planet requires an object to orbit a star, be large enough to be made round by gravity, and have cleared its orbit of other debris. The third criterion disqualifies Pluto, which is now known as a dwarf planet.

After the discovery of Pluto, Tombaugh received a scholarship to study astronomy at the University of Kansas. He began as a freshman in 1932 and continued to work in astronomy for many years. Tombaugh was later known as one of only a few scientists to take UFOs seriously. He died in 1997, mercifully before the demotion of his planet to the status of a dwarf.

Read more at www.aps.org

Advertisements
Aside

Beyond the New Horizon: The Future of Pluto

Best fit lines for functions as determined by the Pluto masses on left, and Pluto and Planet X masses on the right

Best fit lines for functions as determined by the Pluto masses on left, and Pluto and Planet X
masses on the right

Michael B. Lund
Since its discovery in 1930, Pluto’s mass has been a value that has repeatedly been calculated.
Additionally, the search for Planet X prior to Pluto’s discovery results in mass calculations that date back several decades earlier. Over its observed history, the mass of Pluto has consistently decreased. We reassess earlier predictions of Pluto’s fate, and rule out the hypothesis that Pluto’s mass has been constant over the last century.
We are able to fit linear and quadratic equations to Pluto’s mass as a function of both time and distance.
The observations that will be made by New Horizons will help to determine if we can expect Pluto to continue to shrink until it has negative mass, or if it will begin to increase in mass again…
… Read more at http://arxiv.org/pdf/1504.00630v1.pdf

85 Years after Pluto’s Discovery, NASA’s New Horizons Spots Small Moons Orbiting Pluto

The moons Nix and Hydra are visible in a series of images taken by the New Horizons spacecraft. Image Credit: NASA/Johns Hopkins APL/Southwest Research Institute

The moons Nix and Hydra are visible in a series of images taken by the New Horizons spacecraft.
Image Credit: NASA/Johns Hopkins APL/Southwest Research Institute

Exactly 85 years after Clyde Tombaugh’s historic discovery of Pluto, the NASA spacecraft set to encounter the icy planet this summer is providing its first views of the small moons orbiting Pluto.

The moons Nix and Hydra are visible in a series of images taken by the New Horizons spacecraft from Jan. 27-Feb. 8, at distances ranging from about 125 million to 115 million miles (201 million to 186 million kilometers). The long-exposure images offer New Horizons’ best view yet of these two small moons circling Pluto which Tombaugh discovered at Lowell Observatory in Flagstaff, Arizona, on Feb. 18, 1930.

“Professor Tombaugh’s discovery of Pluto was far ahead its time, heralding the discovery of the Kuiper Belt and a new class of planet,” says Alan Stern, New Horizons principal investigator from Southwest Research Institute, Boulder, Colorado. “The New Horizons team salutes his historic accomplishment.”

Assembled into a seven-frame movie, the new images provide the spacecraft’s first extended look at Hydra (identified by a yellow diamond ) and its first-ever view of Nix (orange diamond). The right-hand image set has been specially processed to make the small moons easier to see. “It’s thrilling to watch the details of the Pluto system emerge as we close the distance to the spacecraft’s July 14 encounter,” says New Horizons science team member John Spencer, also from Southwest Research Institute. “This first good view of Nix and Hydra marks another major milestone, and a perfect way to celebrate the anniversary of Pluto’s discovery.”

nh_lorri_4x4

Assembled into a seven-frame movie, the new images provide the spacecraft’s first extended look at Hydra (identified by a yellow diamond ) and its first-ever view of Nix (orange diamond). Image Credit: NASA/Johns Hopkins APL/Southwest Research Institute

These are the first of a series of long-exposure images that will continue through early March, with the purpose of refining the team’s knowledge of the moons’ orbits. Each frame is a combination of five 10-second images, taken with New Horizons’ Long-Range Reconnaissance Imager (LORRI) using a special mode that combines pixels to increase sensitivity at the expense of resolution. At left, Nix and Hydra are just visible against the glare of Pluto and its large moon Charon, and the dense field of background stars. The bright and dark streak extending to the right of Pluto is an artifact of the camera electronics, resulting from the overexposure of Pluto and Charon. As can be seen in the movie, the spacecraft and camera were rotated in some of the images to change the direction of this streak, in order to prevent it from obscuring the two moons.

The right-hand images have been processed to remove most of Pluto and Charon’s glare, and most of the background stars. The processing leaves blotchy and streaky artifacts in the images, and also leaves a few other residual bright spots that are not real features, but makes Nix and Hydra much easier to see. Celestial north is inclined 28 degrees clockwise from the “up” direction in these images.

Nix and Hydra were discovered by New Horizons team members in Hubble Space Telescope images taken in 2005. Hydra, Pluto’s outermost known moon, orbits Pluto every 38 days at a distance of approximately 40,200 miles (64,700 km), while Nix orbits every 25 days at a distance of 30,260 miles (48,700 km). Each moon is probably between 25-95 miles (approximately 40- 150 kilometers) in diameter, but scientists won’t know their sizes more precisely until New Horizons obtains close-up pictures of both of them in July. Pluto’s two other small moons, Styx and Kerberos, are still smaller and too faint to be seen by New Horizons at its current range to Pluto; they will become visible in the months to come.

The Johns Hopkins University Applied Physics Laboratory manages the New Horizons mission for NASA’s Science Mission Directorate in Washington. Alan Stern, of the Southwest Research Institute (SwRI), headquartered in San Antonio, is the principal investigator and leads the mission. SwRI leads the science team, payload operations, and encounter science planning. New Horizons is part of the New Frontiers Program managed by NASA’s Marshall Space Flight Center in Huntsville, Alabama. APL designed, built and operates the spacecraft.

Read more at www.nasa.gov

Telescope digs for ice on Pluto

The track of Pluto across the night sky, as seen from 8 to 20 May 1997 when it was moving southwards in the direction of the constellation of Scorpius. North is at the top in this image. The superimposed red points are the moving point that the JCMT measured for the whole system of Pluto and its moons. Credit: Jane Greaves & George Bendo. Read more at: http://phys.org/news/2014-06-telescope-ice-pluto.html#jCp

The track of Pluto across the night sky, as seen from 8 to 20 May 1997 when it was moving southwards in the direction of the constellation of Scorpius. North is at the top in this image. The superimposed red points are the moving point that the JCMT measured for the whole system of Pluto and its moons. Credit: Jane Greaves & George Bendo.

In just over a year, the New Horizons spacecraft will fly past Pluto, giving us our first detailed look at the dwarf planet. Anticipating this encounter, St Andrews undergraduate student Ailsa Whitelaw and her supervisor Dr Jane Greaves have used forgotten data to map the sub-surface of Pluto, peering beneath its icy coating to uncover hidden chemicals that give a hint of the future of this distant world. Dr Greaves will present the new work in her talk on Wednesday 25 June at the National Astronomy Meeting (NAM 2014) in Portsmouth.

A simulation of the view of Pluto seen from the New Horizon spacecraft over the 4 hours around the closest flyby. The largest moon, Charon, appears in yellow and the Sun's inner planets are marked as seen post-flyby. Lines of longitude and latitude are marked on Pluto and the nightside is to the left of the yellow line at close approach. New Horizons will only have a detailed view of one hemisphere of Pluto. Credit: NASA / New Horizons / Geoviz

A simulation of the view of Pluto seen from the New Horizon spacecraft over the 4 hours around the closest flyby. The largest moon, Charon, appears in yellow and the Sun’s inner planets are marked as seen post-flyby. Lines of longitude and latitude are marked on Pluto and the nightside is to the left of the yellow line at close approach. New Horizons will only have a detailed view of one hemisphere of Pluto. Credit: NASA / New Horizons / Geoviz

Pluto is remote, orbiting at a distance of between 4.4 and 7.3 billion km from the Sun. For that reason even the best images, made using the Hubble Space Telescope, can only pick out features larger than a few hundred km in size on a world itself just 2300 km across. The dwarf planet rotates every 6.4 days, so researchers also observe Pluto using ground-based telescopes, looking at how its brightness varies to deduce whether light or dark features are facing the Earth and hence construct maps of its surface.

Ailsa and Jane adopted a new approach, using data obtained from the James Clerk Maxwell Telescope (JCMT) on Hawaii in the late-1990s. JCMT’s ‘SCUBA’ cameras operate in the sub-millimetre range of the spectrum, between far-infrared and microwave. Pluto was observed at 0.85 mm wavelength, meaning the waves are about 1000 times as long as our eyes can see and in a completely different region of the spectrum to any other data ever obtained from this distant world.
The two scientists assembled a ‘light curve’, where brightness is plotted against time. As Pluto is rotating, the data points correspond to different longitudes on its surface. The 0.85 mm waves are emitted from beneath the surface of the dwarf planet as seen in visible light, hinting at a different chemical mix in the sub-soil. One possible explanation is that a relatively dry layer of frozen nitrogen and methane lies below a dark surface patch of water ice and frozen polymers. Because Pluto’s surface slowly boils away in sunlight (eventually removing the dark patch), this also gives us a sneak preview of its appearance thousands of years in the future.
As well as their forensic analysis of Pluto’s past and future, the new results show a hemisphere of the dwarf planet that New Horizons will miss seeing in detail. The spacecraft zooms through the Pluto system on 14 July 2015, but only has a few minutes to study one side of the dwarf planet and its largest moon Charon at close range.
Jane says: “This was a bit like using a telescope as a digger to mine into Pluto, but with less effort! I’m really excited to see what New Horizons will find a year from now. Some researchers think that even deeper down, Pluto has liquid water, kept fluid by remnant heat from a big crash that formed its moons – if so the surface will probably look wrinkled. But the flyby is so quick that we’ll need to follow up – maybe with future radar we can dig down even further.”
The new ALMA telescope array now operating in Chile works at similar wavelengths and may be able to peer into the other icy dwarf planets discovered in the last decade.
www.ras.org.uk – phys.org

New Horizons Camera Spots Pluto’s Largest Moon

Charon Revealed!
NASA’s Pluto-bound New Horizons spacecraft, using its highest-resolution telescopic camera, has spotted Pluto’s Texas-sized, ice-covered moon Charon for the first time. This represents a major milestone on the spacecraft’s 9½-year journey to conduct the initial reconnaissance of the Pluto system and the Kuiper Belt and, in a sense, begins the mission’s long-range study of the Pluto system.

Pluto and Charon: New Horizons LOng Range Reconnaissance Imager (LORRI) composite image showing the detection of Pluto’s largest moon, Charon, cleanly separated from Pluto itself. The frame on the left is an average of six different LORRI images, each taken with an exposure time of 0.1 second. The frame to the right is the same composite image but with Pluto and Charon circled; Pluto is the brighter object near the center and Charon is the fainter object near its 11 o’clock position. The circles also denote the predicted locations of the objects, showing that Charon is where the team expects it to be, relative to Pluto. No other Pluto system objects are seen in these images. When these images were taken on July 1 and July 3, 2013, the New Horizons spacecraft was still about 550 million miles (880 million kilometers) from Pluto. On July 14, 2015, the spacecraft is scheduled to pass just 7,750 miles (12,500 kilometers) above Pluto’s surface, where LORRI will be able to spot features about the size of a football field.  (Credit: NASA/Johns Hopkins University Applied Physics Laboratory/Southwest Research Institute)

Pluto and Charon: New Horizons LOng Range Reconnaissance Imager (LORRI) composite image showing the detection of Pluto’s largest moon, Charon, cleanly separated from Pluto itself. The frame on the left is an average of six different LORRI images, each taken with an exposure time of 0.1 second. The frame to the right is the same composite image but with Pluto and Charon circled; Pluto is the brighter object near the center and Charon is the fainter object near its 11 o’clock position. The circles also denote the predicted locations of the objects, showing that Charon is where the team expects it to be, relative to Pluto. No other Pluto system objects are seen in these images.
When these images were taken on July 1 and July 3, 2013, the New Horizons spacecraft was still about 550 million miles (880 million kilometers) from Pluto. On July 14, 2015, the spacecraft is scheduled to pass just 7,750 miles (12,500 kilometers) above Pluto’s surface, where LORRI will be able to spot features about the size of a football field. (Credit: NASA/Johns Hopkins University Applied Physics Laboratory/Southwest Research Institute)

The largest of Pluto’s five known moons, Charon orbits about 12,000 miles (more than 19,000 kilometers) away from Pluto itself. As seen from New Horizons, that’s only about 0.01 degrees away.

“The image itself might not look very impressive to the untrained eye, but compared to the discovery images of Charon from Earth, these ‘discovery’ images from New Horizons look great!” says New Horizons Project Scientist Hal Weaver, of the Johns Hopkins University Applied Physics Laboratory, Laurel, Md. “We’re very excited to see Pluto and Charon as separate objects for the first time from New Horizons.”

The spacecraft was still 550 million miles from Pluto – farther than the distance from Earth to Jupiter – when its LOng Range Reconnaissance Imager (LORRI) snapped a total of six images: three on July 1 and three more on July 3. LORRI’s excellent sensitivity and spatial resolution revealed Charon at exactly the predicted offset from Pluto, 35 years after the announcement of Charon’s discovery in 1978 by James Christy of the Naval Observatory.  

“In addition to being a nice technical achievement, these new LORRI images of Charon and Pluto should provide some interesting science too,” says New Horizons Principal Investigator Alan Stern, of the Southwest Research Institute. New Horizons is viewing Pluto and Charon at solar phase angles (the angles between the Sun, Pluto and spacecraft) much larger than can be achieved from observatories located on or near the Earth, potentially yielding important information about the surface properties of Charon and Pluto – perhaps the existence of an overlying layer of fine particles, for example.

“We’re excited to have our first pixel on Charon,” Stern continues, “but two years from now, near closest approach, we’ll have almost a million pixels on Charon –and I expect we’ll be about a million times happier too!”

35 Years Later: Charon is visible as a “bump” moving around Pluto in the moon’s discovery images (right), taken with the 1.55-meter (61-inch) Kaj Strand Astrometric Reflector at the U.S. Naval Observatory’s Flagstaff Station in 1978. More than three decades later, Charon is visible for the first time in pictures (left) taken by the Pluto-bound New Horizons spacecraft.

35 Years Later: Charon is visible as a “bump” moving around Pluto in the moon’s
discovery images (right), taken with the 1.55-meter (61-inch) Kaj Strand Astrometric Reflector at the U.S. Naval Observatory’s Flagstaff Station in 1978. More than three decades later, Charon is visible for the first time in pictures (left) taken by the Pluto-bound New Horizons spacecraft.

Read more at http://pluto.jhuapl.edu/news_center/news/20130710.php

Pluto Stamp Watch

Stamp Petition Gains Nearly 6,000 Signatures

Artist Dan Durda's concept for a U.S. postage stamp honoring the New Horizons mission to Pluto. The probe's team has launched an online petition to make the stamp a reality CREDIT: NASA/SWRI/Dan Durda

The dwarf planet Pluto may be at the edge of our solar system, but an effort on Earth is seeking to put the icy world in mailboxes across the country — in stamp form.

An online petition backed by scientists with NASA’s New Horizons mission is pushing for new postage stamp for Pluto and is hoping to hit 100,000 signatures by March 13, which is the 82nd anniversary of Pluto’s discovery.

So far, the effort has gained the support of almost 6,000 Pluto fans since the petition launched on Feb. 1. SPACE.com is tracking the new Pluto stamp effort through its March 13 deadline. The petition, hosted at Change.org, will be submitted to the Citizens’ Stamp Advisory Committee of the U.S. Postal Service.

Click here to read or sign the Pluto stamp petition “Honor New Horizons and the Exploration of Pluto with a USPS Stamp.”
…..
Read more: space.com