Posted on by Ray Sanders

Are Pluto and Eris Twins?

Artist's rendering of the distant dwarf planet Eris. New suggests that Eris is almost exactly the same diameter as Pluto. Eris is very reflective - possibly due to the frozen remains of its atmosphere. Image Credit: ESO/L. Calçada

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Back a couple of weeks ago, I wrote an article highlighting the debate between scientists on which dwarf planet is bigger, Pluto or Eris. During a planetary science conference earlier this month in France, word “leaked” out that Eris was still more massive, but likely smaller in diameter.

Today, the latest findings were published in Nature, and as such are now “official”. There’s also some additional information, so I’d like to revisit this topic and include some new details which may help answer the question:

Could Eris and Pluto actually be twins?

Before we answer the pressing question, let’s revisit my prior post at: http://www.universetoday.com/89901/pluto-or-eris-which-is-bigger/.

Bruno Sicardy of the Paris Observatory and his team calculated the diameter of Eris in 2010. The technique they used took advantage of an occultation between Eris and a faint background star. Sicardy’s results provided a diameter of 2,326 kilometers for Eris, slightly less than his 2009 estimate of Pluto’s diameter at 2,338 kilometers.

Combining the diameter estimate with mass estimates yielded a density estimate for Eris which suggests, and is supported by its extra mass, that its composition is far more rocky than Pluto, with Eris being only 10-15% ice by mass.

In this week’s announcement by the European Southern Observatory, additional information was presented which sheds new light on cold, distant Eris.

Regarding the new density estimates, Emmanuel Jehin, one of Sicardy’s team members mentions, “This density means that Eris is probably a large rocky body covered in a relatively thin mantle of ice”.

Further supporting Jehin’s assertion, The surface of Eris was found to be extremely reflective, (96% of the light that falls on Eris is reflected, making it nearly as reflective as a backyard telescope mirror). Based on the current estimate, Eris is more reflective than freshly fallen snow on Earth. Based on spectral analysis of Eris, its surface reflectivity is most likely due to a surface of nitrogen-rich ice and frozen methane. Some estimates place the thickness of this layer at less than one millimeter.

Jehin also added, “This layer of ice could result from the dwarf planet’s nitrogen or methane atmosphere condensing as frost onto its surface as it moves away from the Sun in its elongated orbit and into an increasingly cold environment. The ice could then turn back to gas as Eris approaches its closest point to the Sun, at a distance of about 5.7 billion kilometers.”

Based on the new information on surface composition and surface reflectivity, Sicardy and his team were able to make temperature estimates for Eris. The team estimates daytime temperatures on Eris of -238 C, and that temperatures on the night side of Eris would be much lower.

Sicardy concluded with, “It is extraordinary how much we can find out about a small and distant object such as Eris by watching it pass in front of a faint star, using relatively small telescopes. Five years after the creation of the new class of dwarf planets, we are finally really getting to know one of its founding members.”

Source(s): ESO Press Release , Universe Today

Posted on by Ray Sanders

Pluto or Eris: Which is Bigger?

Hubble image of Pluto and some of its moons, Charon, Nix and Hydra. Image Credit: NASA, ESA, H. Weaver (JHU/APL), A. Stern (SwRI), and the HST Pluto Companion Search Team

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The controversy between Pluto and Eris regarding their status as “largest dwarf planet” continues. During a joint meeting of the American Astronomical Society Division for Planetary Sciences and the European Planetary Science Congress last week in Nantes, France, new data was presented that may help settle the debate. The new findings regarding this size of Eris may be a surprise to some, and to others a confirmation of what was believed to be true.

How were astronomers able to make the new measurements of Eris, and what implications will these new measurements have on the Pluto / Eris debate?

Using a celestial alignment known as an occultation, Bruno Sicardy of the Paris Observatory (University of Pierre and Marie Curie, France) and his team were able calculate the diameter of Eris in 2010. The occultation was caused by Eris moving past a background star, which blocked the star’s light and cast a small shadow on Earth. When Sicardy and his team compared the shadow’s size at two different sites in Chile, the calculations provided a diameter of 2,326 kilometers for Eris. A previous study by Sicardy in 2009 placed Pluto’s diameter to be at least 2,338 kilometers.

However, the first estimates of Eris’ size that were made shortly after its discovery put the diameter at 3,000 km, plus or minus 400 km. But a later estimate from observations with the Hubble Space Telescope said Eris might be 2,400 km in diameter, plus or minus 100 km.

If Sicardy’s data calculations hold true, this places Pluto and Eris at nearly the exact same diameter. What has continued to not be up for debate, however, is that Eris is far more massive than Pluto. Given a nearly identical diameter for Eris and Pluto, Eris’s extra mass makes it the denser of the two dwarf planets. According to Sicardy and his team the increased density of Eris, “indicates that Eris is mainly composed of rocky material, with a relatively thin ice mantle.” Since Pluto’s density indicates it comprised of about equal parts ice and rock, Eris’s extra mass would appear to validate Sicardy’s assertion.

Eris and its moon, Dysnomia. Credit: NASA, ESA, and M. Brown (California Institute of Technology)

The Co-discoverer of Eris, and noted “Plutokiller” Mike Brown (Caltech) offers an interesting thought regarding the Pluto / Eris Debate:

“Scientifically, knowing which one is bigger will teach us…. absolutely nothing. The fact that they are nearly identical in size is scientifically interesting; which one is a few kilometers bigger than the other matters not one bit.” Brown also added, “But, still, I will admit to having a bit of an emotional attachment to Eris, so, deep down inside, I want to believe it will turn out to be a little bigger.

You can read a brief synopsis of Sicardy’s findings at: http://meetingorganizer.copernicus.org/EPSC-DPS2011/EPSC-DPS2011-137-8.pdf

If you’d like to learn more about the Pluto / Eris debate, Brown has some great thoughts regarding the debate on his blog at: http://www.mikebrownsplanets.com/2010/11/how-big-is-pluto-anyway.html

Posted on by Jason Major

“Pluto-Killer” Sets Sights on Neptune

Infrared image of Neptune from Keck Observatory in Hawaii. Credit: Mike Brown/CalTech

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The confessed (and remorseless) “Pluto Killer” Mike Brown has turned his gaze – and the 10-meter telescope at the Keck Observatory in Hawaii – on Neptune, our solar system’s furthest “official” planet. But no worries for Neptune – Mike isn’t after its planetary status… he’s taken some beautiful infrared images instead!

Normally only visible as a featureless blue speck in telescopes, Brown’s image of Neptune — along with its largest moon Triton —  shows the icy gas giant in infrared light, glowing bright red and orange.

Neptune and Triton in infrared. Credit: Mike Brown/CalTech.

Brown’s initial intention was not just to get some pretty pictures of planets. The target of the imaging mission was Triton and to learn more about the placement of its methane, nitrogen and seasonal frosts, and this sort of research required infrared imaging. Of course, Neptune turned out to be quite photogenic itself.

“The big difference is doing the imaging in the infrared where methane absorbs most of the photons,” said Brown. “So the bright places are high clouds where the sunlight reflects off of them before it had a chance to pass through much of the atmosphere. Dark is clear atmosphere full of methane absorption.

“I just thought it was so spectacular that I should post it.”

No argument here, Mike!

Neptune, now officially the outermost planet in our solar system, is the fourth largest planet and boasts the highest wind speeds yet discovered — 1,250 mph winds scream around its frigid skies! Like the other gas giants Neptune has a system of rings, although nowhere near as extravagant as Saturn’s. It has 13 known moons, of which Triton is the largest.

With its retrograde orbit, Triton is believed to be a captured Kuiper Belt Object now in orbit around Neptune. Kuiper Belt Objects are Mike Brown’s specialty, as he is the astronomer most well-known for beginning the whole process that got Pluto demoted from the official planet list back in 2006.

Read more on Skymania.com here.

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Jason Major is a graphic designer, photo enthusiast and space blogger. Visit his website Lights in the Dark and follow him on Twitter @JPMajor or on Facebook for the most up-to-date astronomy awesomeness!

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

Hubble Telescope Spots Another Moon Around Pluto

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From a NASA press release:

Astronomers using the Hubble Space Telescope discovered a fourth moon orbiting the icy dwarf planet Pluto. The tiny, new satellite – temporarily designated P4 — was uncovered in a Hubble survey searching for rings around the dwarf planet.

The new moon is the smallest discovered around Pluto. It has an estimated diameter of 8 to 21 miles (13 to 34 km). By comparison, Charon, Pluto’s largest moon, is 648 miles (1,043 km) across, and the other moons, Nix and Hydra, are in the range of 20 to 70 miles in diameter (32 to 113 km).

“I find it remarkable that Hubble’s cameras enabled us to see such a tiny object so clearly from a distance of more than 3 billion miles (5 billion km),” said Mark Showalter of the SETI Institute in Mountain View, Calif., who led this observing program with Hubble.

The finding is a result of ongoing work to support NASA’s New Horizons mission, scheduled to fly through the Pluto system in 2015. The mission is designed to provide new insights about worlds at the edge of our solar system. Hubble’s mapping of Pluto’s surface and discovery of its satellites have been invaluable to planning for New Horizons’ close encounter.

“This is a fantastic discovery,” said New Horizons’ principal investigator Alan Stern of the Southwest Research Institute in Boulder, Colo. “Now that we know there’s another moon in the Pluto system, we can plan close-up observations of it during our flyby.”

The new moon is located between the orbits of Nix and Hydra, which Hubble discovered in 2005. Charon was discovered in 1978 at the U.S. Naval Observatory and first resolved using Hubble in 1990 as a separate body from Pluto.

Illustration of the Pluto Satellite System orbits with newly discovered moon P4 highlighted. Credit: NASA, ESA, and A. Feild (STScI)

The dwarf planet’s entire moon system is believed to have formed by a collision between Pluto and another planet-sized body early in the history of the solar system. The smashup flung material that coalesced into the family of satellites observed around Pluto.

Lunar rocks returned to Earth from the Apollo missions led to the theory that our moon was the result of a similar collision between Earth and a Mars-sized body 4.4 billion years ago. Scientists believe material blasted off Pluto’s moons by micrometeoroid impacts may form rings around the dwarf planet, but the Hubble photographs have not detected any so far.

“This surprising observation is a powerful reminder of Hubble’s ability as a general purpose astronomical observatory to make astounding, unintended discoveries,” said Jon Morse, astrophysics division director at NASA Headquarters in Washington.

P4 was first seen in a photo taken with Hubble’s Wide Field Camera 3 on June 28. It was confirmed in subsequent Hubble pictures taken on July 3 and July 18. The moon was not seen in earlier Hubble images because the exposure times were shorter. There is a chance it appeared as a very faint smudge in 2006 images, but was overlooked because it was obscured.

For more images and information, see the HubbleSite.

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 Jason Major

More Surprises From Pluto

Artist's illustration of Pluto's surface. Credit: NASA

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Ah, Pluto. Seems every time we think we’ve got it figured out, it has a new surprise to throw at us.

First spotted in 1930 by a young Clyde Tombaugh, for 76 years it enjoyed a comfortable position as the solar system’s most distant planet. Then a controversial decision in 2006 by the International Astronomical Union, spurred by suggestions from astronomer (and self-confessed “planet-killer”) Mike Brown*, relegated Pluto to a new class of worlds called “dwarf planets”. Not quite planets and not quite asteroids, dwarf planets cannot entirely clear their orbital path with their own gravitational force and thus miss out on full planetary status. Besides immediately making a lot of science textbooks obsolete and rendering the handy mnemonic “My Very Eager Mother Just Served Us Nine Pies” irrelevant (or at least confusing), the decision angered many people around the world, both in and out of the scientific community. Pluto is a planet, they said, it always has been and always will be! Save Pluto! the schoolkids wrote in crayon to planetarium directors. The world all of a sudden realized how much people liked having Pluto as the “last” planet, and didn’t want to see it demoted by decision, especially a highly contested one.

Yet as it turns out, Pluto really may not be a planet after all.

It may be a comet.

But…that’s getting ahead of ourselves. First things first.

Discovery data showing carbon monoxide spectrum. Credit: J.S. Greaves / Joint Astronomy Centre.

Recent discoveries by a UK team of astronomers points to the presence of carbon monoxide in Pluto’s atmosphere. Yes, Pluto has an atmosphere; astronomers have known about it since 1988. At first assumed to be about 100km thick, it was later estimated to extend out about 1500km and be composed of methane gas and nitrogen. This gas would expand from the planet’s – er, dwarf planet’s – surface as it came closer to the Sun during the course of its eccentric 248-year orbit and then freeze back onto the surface as it moved further away. The new findings from the University of St Andrews team, made by observations with the James Clerk Maxwell telescope in Hawaii, identify an even thicker atmosphere containing carbon monoxide that extends over 3000 km, reaching nearly halfway to Pluto’s largest moon, Charon.

It’s possible that this carbon monoxide atmosphere may have expanded outwards from Pluto, especially in the years since 1989 when it made the closest approach to the Sun in its orbit. Surface heating (and the term “heating” is used scientifically here…remember, at around -240ºC (-400ºF) Pluto would seem anything but balmy to us!) by the Sun’s radiation would have warmed the surface and expelled these gases outwards. This also coincides with observations made by the Hubble Space Telescope over the course of four years, which revealed varying patterns of dark and light areas on Pluto’s surface – possibly caused by the thawing of frozen areas that shift and reveal lighter surface material below.

“Seeing such an example of extra-terrestrial climate-change is fascinating. This cold simple atmosphere that is strongly driven by the heat from the Sun could give us important clues to how some of the basic physics works, and act as a contrasting test-bed to help us better understand the Earth’s atmosphere.”

–  Dr. Jane Greaves, Team Leader

In fact, carbon monoxide may be the key to why Pluto even still has an atmosphere. Unlike methane, which is a greenhouse gas, carbon monoxide acts as a coolant; it may be keeping Pluto’s fragile atmosphere from heating up too much and escaping into space entirely! Over the decades and centuries that it takes for Pluto to complete a single year, the balance between these two gases must be extremely precise.

Read more about this discovery on the Royal Astronomical Society’s site.

Pluto's elliptical orbit

So here we have Pluto exhibiting an expanding atmosphere of thawing expelled gas as it gets closer to the Sun in an elliptical, eccentric orbit. (Sound familiar?) And now there’s another unusual, un-planet-like feature that’s being put on the table: Pluto may have a tail.

Actually this is an elaboration of the research results coming from the same team at the University of St Andrews. The additional element here is a tiny redshift detected in the carbon monoxide signature, indicating that it is moving away from us in an unusual way. It’s possible that this could be caused by the top layers of Pluto’s atmosphere – where the carbon monoxide resides – being blown back by the solar wind into, literally, a tail.

That sounds an awful lot, to this particular astronomy reporter anyway, like a comet.

Just saying.

Anyway, regardless of what Pluto is or isn’t, will be called or used to be called, there’s no denying that it is a fascinating little world that deserves our attention. (And it will be getting plenty of that come July 2015 when the New Horizons spacecraft swings by for a visit!) I’m sure there’s no one here who would argue that fact.

New Horizons’ upcoming visit will surely answer many questions about Pluto – whatever it is – and most likely raise even more.

 

Artist's impression of Pluto's huge atmosphere of carbon monoxide.Credit:P.A.S. Cruickshank.

The new discovery was presented by team leader Dr. Jane Greaves on Wednesday, April 20 at the National Astronomy Meeting in Wales.

Article reference: arxiv.org/abs/1104.3014: Discovery Of Carbon Monoxide In The Upper Atmosphere Of Pluto

 

*No disrespect to Mr. Brown intended…he was just performing science as he saw fit!

 

 

Posted on by Nancy Atkinson

Clyde Tombaugh’s Ten Special Commandments for Planet Hunters

The Ten Special Commandments for a Would-Be Planet Hunter, according to Clyde Tombaugh. Scan courtesy of Toney Burkhart.

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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.

Posted on by Nancy Atkinson

New Horizons Flies by Uranus

An 'overhead' view of New Horizons' location. Credit: NASA

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.”

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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