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
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.”
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
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.
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
After careful consideration and analysis, the Hubble Space Telescope Time Allocation Committee has recommended using Hubble to search for an object the Pluto-bound NASA New Horizons mission could visit after its flyby of Pluto in July 2015.
The planned search will involve targeting a small area of sky in search of a Kuiper Belt object (KBO) for the outbound spacecraft to visit. The Kuiper Belt is a vast debris field of icy bodies left over from the solar system’s formation 4.6 billion years ago. A KBO has never been seen up close because the belt is so far from the sun, stretching out to a distance of 5 billion miles into a never-before-visited frontier of the solar system.
“I am pleased that our science peer-review process arrived at a consensus as to how to effectively use Hubble’s unique capabilities to support the science goals of the New Horizons mission,” said Matt Mountain, director of the Space Telescope Science Institute (STScI) in Baltimore, Maryland.
Fully carrying out the KBO search is contingent on the results from a pilot observation using Hubble data.
The space telescope will scan an area of sky in the direction of the constellation Sagittarius to try and identify any objects orbiting within the Kuiper Belt. To discriminate between a foreground KBO and the clutter of background stars in Sagittarius, the telescope will turn at the predicted rate that KBOs are moving against the background stars. In the resulting images, the stars will be streaked, but any KBOs should appear as pinpoint objects.
If the test observation identifies at least two KBOs of a specified brightness it will demonstrate statistically that Hubble has a chance of finding an appropriate KBO for New Horizons to visit. At that point, an additional allotment of observing time will continue the search across a field of view roughly the angular size of the full moon.
Astronomers around the world apply for observing time on the Hubble Space Telescope. Competition for time on the telescope is extremely intense and the requested observing time significantly exceeds the observing time available in a given year. Proposals must address significant astronomical questions that can only be addressed with Hubble’s unique capabilities, and are beyond the capabilities of ground-based telescopes. The proposals are peer reviewed annually by an expert committee, which looks for the best possible science that can be conducted by Hubble and recommends to the Space Telescope Science Institute director a balanced program of small, medium, and large investigations.
Though Hubble is powerful enough to see galaxies near the horizon of the universe, finding a KBO is a challenging needle-in-haystack search. A typical KBO along the New Horizons trajectory may be no larger than Manhattan Island and as black as charcoal.
Even before the launch of New Horizons in 2006, Hubble has provided consistent support for this edge-of-the-solar system mission. Hubble was used to discover four small moons orbiting Pluto and its binary companion object Charon, providing new targets to enhance the mission’s scientific return. And Hubble has provided the most sensitive search yet for potentially hazardous dust rings around the Pluto. Hubble also has made a detailed map of the dwarf planet’s surface, which astronomers are using to plan New Horizon’s close-up reconnaissance photos.
In addition to Pluto exploration, recent Hubble solar system observations have discovered a new satellite around Neptune, probed the magnetospheres of the gas-giant planets, found circumstantial evidence for oceans on Europa, and uncovered several bizarre cases of asteroids disintegrating before our eyes. Hubble has supported numerous NASA Mars missions by monitoring the Red Planet’s seasonal atmospheric changes. Hubble has made complementary observations in support of the Dawn asteroid mission, and comet flybys. In July 1994, Hubble documented the never-before-seen string of comet collisions with Jupiter that resulted from the tidal breakup of comet Shoemaker-Levy 9.
“The planned search for a suitable target for New Horizons further demonstrates how Hubble is effectively being used to support humankind’s initial reconnaissance of the solar system,” said Mountain. “Likewise, it is also a preview of how the powerful capabilities of the upcoming James Webb Space Telescope will further bolster planetary science. We are excited by the potential of both observatories for ongoing solar system exploration and discovery.”
Read more at http://www.nasa.gov/press/2014/june/nasa-hubble-to-begin-search-beyond-pluto-for-a-new-horizons-mission-target/#.U58LctTy7aV
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.
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!”
Stamp Petition Gains Nearly 6,000 Signatures
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.
In 2006, NASA dispatched an ambassador to the planetary frontier. The New Horizons spacecraft is now halfway between Earth and Pluto, on approach for a dramatic flight past the icy planet and its moons in July 2015.
After 10 years and more than 3 billion miles, on a historic voyage that has already taken it over the storms and around the moons of Jupiter, New Horizons will shed light on new kinds of worlds we’ve only just discovered on the outskirts of the solar system.
Pluto gets closer by the day, and New Horizons continues into rare territory, as just the fifth probe to traverse interplanetary space so far from the Sun. And the first to travel so far, to reach a new planet for exploration. nasa.gov