Posted on by Ken Kremer

New Horizons Spacecraft ‘Stays the Course’ for Pluto System Encounter

The Pluto and Charon Binary Planet System imaged by the Hubble Space Telescope. NASA’s New Horizons spacecraft will pass through in 2015 using the original baseline trajectory . Credit: Hubble Space Telescope

Following an intense 18 month study to determine if NASA’s New Horizons spacecraft faced potentially destructive impact hazards during its planned 2015 flyby of the Pluto binary planet system, the mission team has decided to ‘stay the course’ – and stick with the originally planned trajectory because the danger posed by dust and debris is much less than feared.

The impact assessment study was conducted because the Pluto system was discovered to be much more complex – and thus even more scientifically compelling – after New Horizons was launched in January 2006 from Cape Canaveral in Florida.

Two years ago researchers using the iconic Hubble Space Telescope discovered two new moons orbiting around Pluto, bringing the total to 5 moons!

It was feared that debris hitting the moons could have created dangerous dust clouds that in turn would slam into and damage the spacecraft as it zoomed past Pluto at speeds of some 30,000 miles per hour (more than 48,000 kilometers per hour) in July 2015.

“We found that loss of the New Horizons mission by dust impacting the spacecraft is very unlikely, and we expect to follow the nominal, or baseline, mission timeline that we’ve been refining over the past few years,” says New Horizons Project Scientist Hal Weaver, of the Johns Hopkins University Applied Physics Laboratory, in a statement.

After both the team and an independent review board and NASA thoroughly analyzed the data, it was determined that New Horizons has only a 0.3 percent chance of suffering a mission destroying dust impact event using the baseline trajectory.

Hubble Space Telescope view of Pluto and its known moons.
Hubble Space Telescope view of Pluto and its known moons.

The 0.3 percent probability of mission loss is far less than some earlier estimates.

This is really good news because the team can focus most of its efforts on developing the flyby encounter science plan when New Horizons swoops to within about 12,500 kilometers (nearly 7,800 miles) of Pluto’s surface.

Pluto forms a “double planet” system with Charon, its largest moon. Charon is half the size of Pluto.

But the team will still expend some effort on developing alternative trajectories – known as SHBOTs, short for Safe Haven by Other Trajectories, just in case new information arises from the ships camera observations that would force a change in plans as New Horizons sails ever closer to Pluto.

“Still, we’ll be ready with two alternative timelines, in the event that the impact risk turns out to be greater than we think,” says Weaver.

Indeed the team, led by Principal Investigator Alan Stern, of the Southwest Research Institute is finalizing the encounter plan this month and plans a rehearsal in July of the most critical nine-day segment of the baseline flyby trajectory.

New Horizons will perform the first reconnaissance of Pluto and Charon in July 2015. The “double planet” is the last planet in our solar system to be visited by a spacecraft from Earth.

And New Horizons doesn’t’ stop at Pluto. The goal is to explore one or more of the icy Kuiper Belt Objects (KBO’s) further out in the Solar System.

The team will use the Pluto flyby to redirect New Horizons to a KBO that is yet to be identified.

And don’t forget to “Send Your Name to Mars” aboard NASA’s MAVEN orbiter- details here. Deadline: July 1, 2013. Launch: Nov. 18, 2013

Ken Kremer

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Learn more about Pluto, Mars, Curiosity, Opportunity, MAVEN, LADEE and NASA missions at Ken’s upcoming lecture presentations

June 23: “Send your Name to Mars on MAVEN” and “CIBER Astro Sat, LADEE Lunar & Antares Rocket Launches from Virginia”; Rodeway Inn, Chincoteague, VA, 8 PM

Posted on by Jason Major

Researchers Present the Sharpest Image of Pluto Ever Taken from Earth

A “speckle image” reconstruction of Pluto and its largest moon, Charon (Gemini Observatory/NSF/NASA/AURA)

Real planet, dwarf planet, KBO, who cares? What matters here is that astronomers have created the sharpest image of Pluto ever made with ground-based observations — and developed a new way to verify potential Earth-like exoplanets at the same time.

Here’s how they did it:


After taking a series of quick “snapshots” of Pluto and Charon using a recently-developed camera called the Differential Speckle Survey Instrument (DSSI), which was mounted on the Gemini Observatory’s 8-meter telescope in Hawaii, researchers combined them into a single image while canceling out the noise caused by turbulence and optical aberrations. This “speckle imaging” technique resulted in an incredibly clear, crisp image of the distant pair of worlds — especially considering that 1. it was made with images taken from the ground, 2. Pluto is small, and 3. Pluto is very, very far away.

Read: Why Pluto is No Longer a Planet

Less than 3/4 the diameter of our Moon, Pluto (and Charon, which is about half that size) are currently circling each other about 3 billion miles from Earth — 32.245 AU to be exact. That’s a long way off, and there’s still much more that we don’t know than we do about the dwarf planet’s system. New Horizons will fill in a lot of the blanks when it passes close by Pluto in July 2015, and images like this can be a big help to mission scientists who want to make sure the spacecraft is on a safe path.

“The Pluto-Charon result is of timely interest to those of us wanting to understand the orbital dynamics of this pair for the 2015 encounter by NASA’s New Horizons spacecraft,” said Steve Howell of the NASA Ames Research Center, who led the Gemini imaging study.

See images of Pluto taken by Hubble here.

In addition, the high resolution achievable through the team’s speckle imaging technique may also be used to confirm the presence of exoplanet candidates discovered by Kepler. With an estimated 3- to 4-magnitude increase in imaging sensitivity, astronomers may be able to use it to pick out the optical light reflected by a distant Earth-like world around another star.

Speckle imaging has been used previously to identify binary star systems, and with the comparative ability to “separate a pair of automobile headlights in Providence, RI, from San Francisco, CA” there’s a good chance that it can help separate an exoplanet from the glare of its star as well.

The research was funded in part by the National Science Foundation and NASA’s Kepler discovery mission, and will be published in the journal Publications of the Astronomical Society of the Pacific in October 2012. Read more here.

Main image: the first speckle reconstructed image for Pluto and Charon from which astronomers obtained not only the separation and position angle for Charon, but also the diameters of the two bodies. North is up, east is to the left, and the image section shown is 1.39 arcseconds across. Resolution of the image is about 20 milliarcseconds rms. Credit: Gemini Observatory/NSF/NASA/AURA. Inset: the Gemini North telescope on the summit of Mauna Kea. (Gemini Observatory)

Posted on by Tammy Plotner

Does The Pluto System Pose A Threat To New Horizons?

Pluto's newest found moon, P4, orbits between Nix and Hydra, both of which orbit beyond Charon. Could there be still more moons of Pluto? Perhaps, and the New Horizons team plans to look harder to ensure that we don't run into something that could damage or destroy New Horizons. Credit: NASA

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With nearly two-thirds of its journey complete, the New Horizons spacecraft is still alive and well. It recently experienced a “hibernation wakeup” which started on November 5th and will last until November 15th… and it will sleep again until a month-long call in January. However, the real “wakeup call” may be when it reaches the complicated Pluto system. Watch out for that rock!

As more and more moons are discovered around Pluto, the higher the probability becomes of one of them – or debris surrounding them – could impact the delicate probe. With P4 discovered just a few short months ago, scientists are beginning to wonder just how many more are there which are too small and faint to be seen.

Says New Horizons Principal Investigator Alan Stern: “Even more worrisome than the possibility of many small moons themselves is the concern that these moons will generate debris rings, or even 3-D debris clouds around Pluto that could pose an impact hazard to New Horizons as it flies through the system at high speed. After all, at our 14-kilometer-per-second flyby speed, even particles less than a milligram can penetrate our micrometeoroid blankets and do a lot of damage to electronics, fuel lines and sensors.”

To enable research into what might be a prospective problem, the New Horizons team brought together about 20 of the world’s experts in ring systems, orbital dynamics and state-of-the-art astronomical observing techniques to search for small satellites and rings at distant Pluto. During a two day workshop, the group hashed and rehashed every possible scenario – including all the hazards that a small moon and debris-strewn system might cause.

The presenters and attendees of the New Horizons Pluto Encounter Hazards Workshop on November 4, 2011. Credit: NASA

“We found a plausible chance that New Horizons might face real danger of a killer impact; and that to mitigate that hazard, we need to undertake two broad classes of work.” said Stern. “First, we need to look harder at the Pluto system for still undiscovered satellites and rings. The best tools for this are going to be the Hubble Space Telescope, some very large ground-based telescopes, telescopes that can make stellar occultation observations of the space between Pluto and Charon where New Horizons is currently targeted, and thermal observations of the system by the ALMA radio telescope array just now being commissioned.”

The next step is planning – planning on a possible safer route through the Pluto system in the event that observations confirm navigational hazards. Studies presented at the Encounter Hazards Workshop show a good “safe haven bailout trajectory” (or SHBOT) could be designed to target a closest-approach aim point about 10,000 kilometers farther than the nominal mission trajectory. In this case, it would be a matter of aiming more towards Charon’s orbit, where the moon itself has cleared a path. However, even 180 degrees away on closest approach may not be enough. There’s always a chance of a debris field – one that doesn’t follow a plane, but has created a torus. In this event, material could be sailing along at speeds of up to 1-2 kilometers per second. Enough to annihilate delicate instruments.

“The question of whether the Pluto system could be hazardous to New Horizons remains open –but one we’ll be studying hard over the next year, with everything from computer models to big ground-based telescopes to the Hubble.” concludes Stern. “I’ll report on results as we obtain them, but it is not lost on us that there is a certain irony that the very object of our long-held scientific interest and affection may, after so many years of work to reach her, turn out to be less hospitable than other planets have been. We’ll see.”

Original Story Source: New Horizons News.

Posted on by Ray Sanders

Ring System Around Pluto?

HST Image of Pluto-Charon system. Also shown are Nix and Hydra. Image Credit: NASA/ESA

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With the New Horizons spacecraft on its way to Pluto, there may be an intriguing additional task for the mission’s science team: look for a potential ring around Pluto and its moons. Researchers at The Universidade Estadual Paulista in Brazil have recently submitted a paper for publication in which they explore the possibility of a ring system around the Pluto-Charon system.  In their paper, the team discusses the effects of micrometeoroid impacts on Nix and Hydra and how the resulting dust particles could form a ring around Pluto.  The team also investigates forces, such as the solar wind, which would dissipate said ring system.


Pryscilla Maria Pires dos Santos and her team provide an exhaustive list of calculations in their paper which estimates the ring system to have a diameter of nearly 16,000 kilometers – well outside the orbits of Nix and Hydra.  Based on their calculations, Pires dos Santos state that despite nearly 50% of the ring’s mass being dissipated within a year, a tenuous ring system can be maintained by the dust expelled by micrometeoroid impacts.

Additional data presented in the paper places the rings “optical depth” as being several orders of magnitude fainter than even Jupiter’s rings. (Yes, Jupiter has a ring system!)  While ground-based observatories and even the Hubble Space Telescope haven’t detected the ring system Pires dos Santos et al. are hopeful that the New Horizons mission will provide data to validate their theoretical models. New Horizons has a dust counter capable of measuring dust grains with a minimum mass of 10-12 grams, which should provide the data required to support or refute the team’s models.

Pires dos Santos mentions: “It is worth to point out that the interplanetary environment in the outer Solar System is not well known. Many assumptions have to be made in order to estimate a normal optical depth of a putative ring encompassing the orbits of Nix and Hydra.”

If you’d like to read the full paper, you can access it  (for free) at: http://arxiv.org/PS_cache/arxiv/pdf/1108/1108.0712v1.pdf

Source: arXiv:1108.0712v1 [astro-ph.EP]

Posted on by Nancy Atkinson

Double Occultations This Week Will Reveal More Details About Pluto

Several teams of astronomers are taking advantage of a rare double event this week to learn more about the atmosphere and makeup of Pluto and its moons. The dwarf planet will occult, or pass in front of two different stars this week. One of the best viewing sites for these two events is in Hawaii, and eclipse-chaser Dr. Jay Pasachoff is there to record both events. “To see those occultations, we have to be in a particular set of places on Earth, those over which the shadow of the object in starlight passes,” Pasachoff wrote in a guest post on the Planet Hunters blog. “Since the stars are so far away, their light is essentially parallel and the shadows of the objects on Earth are the same as the sizes of the objects.”

If all goes well, we will know a lot more about the Pluto system, Pasachoff said.

Map of where the occultation would be visible on June 22-23, 2011.

Last night, June 22/23, both Pluto and its moon Charon occulted a magnitude 14.4 star, with each occultation lasting a minute or so and separated from each other by 12 minutes. “The event is particularly exciting because if we capture both Pluto and Charon nearly simultaneously, we can find out about the system’s internal orbits with higher precision than before, perhaps allowing a refinement of the center of mass and thus the masses and densities of each object,” Pasachoff said.

Also, the first deployment for an occultation of the NASA/German SOFIA observatory took place last night to view the Pluto occultation, flying at an altitude of 43,000 feet off the west coast of Central America.

“The scientific goal is to catch the ‘central flash,’ which conveys vital information about conditions in Pluto’s global atmosphere,” wrote American Astronomical Society press officer Rick Fienberg on Twitter. Fienberg was part of the press corps that was accompanying the flight.

On Sunday/Monday night, June 26/27, Pluto will occult a different star, and over a much narrower path, its small moon Hydra might also occult another star.

Pasachoff said that the most recent predictions for last night’s occulations shifted the prediction south, so that Hawaii is slightly off the main predicted path, to its north. But other teams are in Cairns, Australia, to see if it goes that far south.

For the June 26/27 event (June 27 UT but June 26 in Hawaii), the star is magnitude 13.6. “That is a couple of magnitudes brighter than most of the stars we have observed being occulted,” Pasachoff said, “so the data would be particularly low-noise. In addition to the occultation of Pluto itself, whose southern limit is predicted to pass through the Hawaiian islands, the tiny Pluto moon Hydra is to be occulted, though that narrow path’s prediction now passes north of the Hawaiian islands. We have arranged for telescopes in Yunnan, China, in Japan, Taiwan, and Thailand to observe with us, and MIT’s Matt Lockhart is en route to Yunnan with one of our POETS (Portable Occultation, Eclipse, and Transit System) cameras. We have Australian sites still observing as well, just in case the actual path is hundreds of kilometers south of the predictions.”

Earlier occultations by Pluto studied by Pasachoff and his colleagues showed that Pluto’s atmosphere was warming and that the atmosphere would probably remain warm enough by 2015 for the New Horizons spacecraft to detect and study it with its on-board instruments, and was part of the incentive for the mission to launch when it did.

To learn more about the occultations and the research, check out this main stellar occultation website from Williams College, where Pasachoff is located, which has links to the work of other researchers as well.

Maps and details of the predictions can be found here, and more details about Pluto occultations websites can be found here.

We’ll try to provide an update of the events when details become available.

You can follow Universe Today senior editor Nancy Atkinson on Twitter: @Nancy_A. Follow Universe Today for the latest space and astronomy news on Twitter @universetoday and on Facebook.

Posted on by Ian O'Neill

Pluto’s Moons, Nix and Hydra, may have been Adopted

The discovery images of Nix (and Hydra) obtained by the Hubble Space Telescope. Credit: NASA, ESA, H. Weaver (JHU/APL), A. Stern (SwRI)

 

How many moons does Pluto have? The mini-moons of Pluto, Nix and Hydra, were discovered in 2005 (but named in 2006) during an observation campaign by the Hubble Space Telescope. The discovery of these mini-moons increase the number of natural satellites orbiting Pluto to three (including larger moon Charon). But where did these satellites come from? The current accepted theory on the formation on the large moon, Charon, is much like the theory supporting the creation of Earth’s Moon. It is thought that a large impact between two Large Kuiper Belt Objects chipped Charon away from a proto-Pluto, putting the chunk of Pluto mass into orbit. Over the years, tidal forces slowed the pair and Charon was allowed to settle into its present-day orbit. Recent theory suggests that Nix and Hydra are a by product of this collision, merely shattered fragments of the huge impact. But there are problems with this idea. Could Nix and Hydra have come from somewhere other than the Pluto-Charon impact?

The orbits of Plutos moons, Charon, Nix and Hydra (credit: NASA)
The small moons that orbit the Large Kuiper Belt Object (formerly classified as a planet) can be found about 48,700 kilometers and 64,800 kilometers from the surface of Pluto. The closest moon is called Nix and the farthest, Hydra. Nix has an orbital resonance of 4:1 with Charons orbit and the larger moon Hydra has a resonance of 6:1 (i.e. Nix will orbit Pluto once for every four of Charons orbits; Hydra will orbit Pluto once for every six of Charons orbits).

The reasons behind these mini-moon orbits are only just beginning to be understood, but it is known that their resonances with Charons orbit is rooted way back during the Pluto-system evolution. If we assume Hydra and Nix were formed from a massive Kuiper Belt Object collision, the easiest explanation is to assume they are whole fragments from the impact caught in the gravity of the Pluto-Charon system. However, due to the highly eccentric orbits that would have resulted from this collision, it is not possible that the two little moons could have evolved into a near-circular orbit, in near-corotational resonance with Charon.

So, could it be possible that the moons may have formed from the dust and debris resulting from the initial collision? If there was enough material produced, and if the material collided frequently, then perhaps Nix and Hydra were born from a cold disk of debris (rather than being whole pieces of rock), eventually coalescing and forming sizeable rocky moons. As there may have been a disk of debris, collisions with the orbiting Nix and Hydra would have also reduced any eccentricity in their orbits.

But there is a big problem with this theory. From impact simulations, the post-impact disk of debris surrounding Pluto would have been very compact. The disk could not have reached as far as the present-day orbits of the moons.

One more theory suggests that perhaps the moons were created in a post-impact disk, but very close to Pluto, and then through gravitational interactions with Charon, the orbits of Nix and Hydra were pulled outward, allowing them to orbit far from the Pluto-Charon post-impact disk. According to recent computer simulations, this doesn’t seem to be possible either.

To find an answer, work by Yoram Lithwick and Yanqin Wu (University of Toronto) suggest we must look beyond the Pluto-Charon system for a source of material for Nix and Hydra. From simulations, the above theories on the creation of the small moons being started by material ejected from a large collision between two Large Kuiper Belt Objects (creating Pluto and Charon) are extremely problematic. They do not correctly answer how the highly eccentric orbits Nix and Hydra would have from a collision could evolve into the near-circular ones they have today.

Lithwick and Wu go on to say that the circular, corotational resonant orbits of the two moons could be created from a Plutocentric disk of small bits of rock scooped up during Pluto’s orbit around the Sun. Therefore Nix and Hydra may have been formed from the rocky debris left over from the development of the Solar System, and not from a collision event creating Charon. This may hold true for the countless other Kuiper Belt Objects in orbit in the far reaches of the Solar System, no impact is necessary for the creation of the tiny moons now thought to be their satellites.

It is hoped that the New Horizons mission (launched January 21st, 2006) to the far reaches of the Solar System will reveal some of the questions that remain unanswered in the depths of our mysterious Kuiper Belt. Hopefully we will also find out whether Nix and Hydra are children of Pluto and Charon… or whether they were adopted.

Source: arXiv