Pluto Archives

February 26, 2013December 23, 2015 by Jason Major

New Horizons’ Pluto Stamp is One Step Closer to Becoming a Reality

Concept art for a New Horizons postage stamp. Image Credit: Dan Durda/Southwest Research Institute

A little over a year ago Alan Stern, principal investigator on the New Horizons mission, announced the team’s plans to have a Forever Stamp issued by the US Postal Service commemorating the New Horizons spacecraft along with its targets, Pluto and Charon. Thousands signed the petition, and today the team announced a long-awaited update to all of its supporters: it’s definitely a maybe!

In an email sent out to petition signers as well as on its Facebook page, the New Horizons team noted that the stamp — conceptualized by planetary scientist and artist Dan Durda — has cleared its first major hurdle in the USPS approval process and will be submitted for review and consideration before their Advisory Committee.

Pending that approval, it will then be put on the agenda for the meeting of the Citizens’ Stamp Advisory Committee.

After that point, since no notification is made to the applicant about a stamp’s approval by the Postmaster General until a public announcement is issued it’s likely that we won’t know if there will actually be a New Horizons stamp until the spacecraft is on final approach to Pluto in July 2015. Hopefully the USPS will see the benefit to having a stamp actually ready for purchase by that time and plan accordingly, but one never knows. Until then, cross your fingers and keep an eye out for a Forever Stamp featuring the “First Spacecraft to Explore Pluto!”

“This is a chance for us all to celebrate what American space exploration can achieve though hard work, technical excellence, the spirit of scientific inquiry, and the uniquely human drive to explore.”

– Alan Stern, New Horizons Principal Investigator

USPS Forever Stamps can be used to mail a one-ounce letter regardless of when the stamps are purchased or used and no matter how prices may change in the future. Forever Stamps are always sold at the same price as a regular First-Class Mail stamp. Forever Stamps can be used for international mail, but since all international prices are higher than domestic US prices, additional postage is necessary.

February 25, 2013April 26, 2016 by Jason Major

Pluto May Soon Have a Moon Named Vulcan (Thanks to William Shatner)

These may soon be the names of Pluto's family of moons (Hubble image: NASA, ESA and M. Showalter/SETI)

The votes have been tallied and the results are in from the SETI Institute’s Pluto Rocks Poll: “Vulcan” and “Cerberus” have come out on top for names for Pluto’s most recently-discovered moons, P4 and P5.

After 450,324 votes cast over the past two weeks, Vulcan is the clear winner with a landslide 174,062 votes… due in no small part to a little Twitter intervention by Mr. William Shatner, I’m sure.

In other words… yes, the Trekkies have won.

During a Google+ Hangout today, SETI Institute senior scientist Mark Showalter — who discovered the moons and opened up the poll — talked with SETI astronomer Franck Marchis and MSNBC’s Alan Boyle about the voting results. Showalter admitted that he wasn’t quite sure how well the whole internet poll thing would work out, but he’s pleased with the results.

“I had no idea what to expect,” said Showalter. “As we all know the internet can be an unruly place… but by and large this process has gone very smoothly. I feel the results are fair.”

As far as having a name from the Star Trek universe be used for an actual astronomical object?

“Vulcan works,” Showalter said. “He’s got a family tie to the whole story. Pluto and Zeus were brothers, and Vulcan is a son of Pluto.”

And what can you say when even Mr. Spock agrees?

The other winning name, Cerberus, is currently used for an asteroid. So because the IAU typically tries to avoid confusion with two objects sharing the same exact name, Showalter said he will use the Greek version of the spelling: Kerberos.

Cerberus (or Kerberos) is the name of the giant three-headed dog that guards the gates to the underworld in Greek mythology.

Now that the international public has spoken, the next step will be to submit these names to the International Astronomical Union for official approval, a process that could take 1–2 months.

(Although who knows… maybe Bill can help move that process along as well?)

Read more about the names on the Pluto Rocks ballot here, and watch the full recorded Google+ Hangout below:

February 18, 2013December 23, 2015 by David Dickinson

Naming Pluto’s Moons: Will it Come Down to Trekkies Versus the IAU?

The path of New Horizons through Pluto's growing family. (Image Credit: NASA/ESA/A. Field STScl).

As reported here on Universe Today last week, the SETI Institute has invited the public to vote on the names of Pluto’s 4^th and 5^th moons. Discovered in 2011 and 2012 respectively, researcher and co-discoverer Mark Showalter will take these names before the International Astronomical Union (IAU) after voting closes on February 25^th, 2013.

But days after the polling opened, a curious twist in the tale occurred that Star Trek’s Mr. Spock would only describe as “Fascinating.”

William Shatner, James T. Kirk himself, proposed the name Vulcan for one of Pluto’s unnamed moons. Fans and Trekkies worldwide rallied, and as of writing this, Vulcan enjoys a comfortable lead over Cerberus and Styx which are vying for the 2^nd place position.

This astronomical horse-race has the propensity to get interesting. In order to be considered, the IAU’s naming convention simply states “Those that share Pluto’s orbital rhythm take the name of underworld deities,” And the named moons of Charon, Nix & Hydra all follow this convention. Shatner’s case for Vulcan does cite the god as “The nephew of Pluto” in Roman mythology, but anyone who had studied Roman and Greek mythos knows that familial relations can be proven between nearly any given god and/or goddess.

Interestingly, Showalter turned down Shatner’s second Star Trek/mythological suggestion of Romulus, citing that Romulus and Remus are already the names of the moons of asteroid 87 Silvia. While the “double naming” of objects in the solar system isn’t unheard of, it may be a definite strike against a proposal. Cerberus, Orpheus, Hypnos & Persephone are all names in the running that are all also assigned to asteroids.

On February 14^th, researchers “Opened up the Gates of Hell” a bit further and took more mythological nominations into the running, adding Elysium, Hecate, Melinoe, Orthrus, Sisyphus, Tantalus, Tartarus and Thantos into the fray. You can write-in candidates such as “Donald,” & “Goofy,” but these stand a proverbial snowball’s chance in Hades of being accepted. Perhaps the backing of a starship captain would help, if Adama or Han Solo were available for hire…

Still, one wonders if the name Vulcan will make it past the gate-keepers at the IAU. The IAU has sparked controversy surrounding Pluto before, in its 2006 decision that angered 5^th graders everywhere when they demoted Pluto to dwarf planet status. No solar system body currently holds the name of Vulcan, although one hypothetical one once did; the tiny fleeting world that was once thought to be interior to Mercury’s orbit. Several astronomers even claimed to witness transits of the fleeting world across the face of the Sun, and up until the late 19^th century, you could still find Vulcan in many astronomy texts. While the idea of Vulcan as a planet interior to Mercury is out (think of how many telescopes, both amateur and professional, now continuously monitor the Sun daily) it’s not out of the question that a small group of asteroids less than 10 kilometres in size tentatively dubbed “Vulcanoids” may still inhabit the space interior to Mercury.

Fans of Pluto unite... could Vulcan spark a repeat protest? (Wikimedia Commons image in the Public Domain). — Fans of Pluto unite… could Vulcan spark a repeat protest? (Wikimedia Commons image in the Public Domain).

But if nothing else, the poll is a fun exercise to watch as astronomy fans worldwide delve into mythological lore and dig out the names of obscure gods and goddesses. A similar debate on mythological merits swirled around the naming of the moon of dwarf planet Orcus, ultimately named Vanth in 2009.

While only two names will be selected for P4 & P5, the other denizens of the underworld may just get their day in July 2015 when NASA’s New Horizons spacecraft gives us the first close up look at Pluto and friends. Previous “first flybys” of other planets and asteroids have turned up new moons before, and Pluto may be no different.

“The discovery of so many small moons indirectly tells us that there must be lots of small particles lurking unseen in the Pluto system,” stated Harold Weaver of the Johns Hopkins University of Applied Physics Laboratory. Such debris will be a definite concern as scientists seek to thread the spacecraft’s trajectory past Pluto and its moons.

A young Clyde Tombaugh with one of his famous homemade telescopes. (Credit : NASA/GSFC).

Discovered 83 years ago to the day on February 18^th, 1930 by American astronomer Clyde Tombaugh, Pluto remains an uncharted corner of the solar system. Mr. Tombaugh passed away on January 17th, 1997, and an ounce of his ashes are aboard the New Horizons spacecraft which, along with the Pioneer 10 & 11 and Voyager 1 & 2 spacecraft, are escaping the solar system to wander along the galactic plane.

I’ve also got a proposal out in the running. By naming one of Pluto’s moons Alecto, we would honor Clyde with the inclusion of his initials “CT” on a moon. There is precedent for such a clever tribute before; James Christy honored his wife Charlene in the naming of Pluto’s large moon Charon and Mike Brown paid homage to his wife Diane by naming Eris’s moon Dysnomia.

Whatever happens, it’ll be interesting to see what transpires in the final names of P4/P5 are selected. Hopefully it won’t end in a showdown pitting Trekkies against the IAU… but don’t forget, the Trekkies did keep a television series on the air and got a space shuttle re-named!

February 11, 2013April 26, 2016 by Jason Major

Help Name Pluto’s Newest Moons!

Pluto's known system of moons (NASA/ESA/M. Showalter))

Today marks seven months since the announcement of Pluto’s fifth moon and over a year and a half since the discovery of the one before that. But both moons still have letter-and-number designations, P5 and P4, respectively… not very imaginative, to say the least, and not really fitting into the pantheon of mythologically-named worlds in our Solar System.

Today, you can help change that.

According to the New Horizons research team, after the discovery of P4 in June 2011 it was decided to wait to see if any more moons were discovered in order to choose names that fit together as a pair, while a*lso following accepted IAU naming practices. Now, seven months after the announcement of P5, we think a decision is in order… and so does the P4/P5 Discovery Team at the SETI Institute.

"Hey, I can be democratic about this!" — “Hey, I can be democratic about all this!”

Today, SETI Senior Research Scientist Mark Showalter revealed a new poll site, Pluto Rocks, where visitors can place their votes on a selection of names for P4 and P5 — or even write in a suggestion of their own. In line with IAU convention these names are associated with the Greek and Roman mythology surrounding Pluto/Hades and his underworld-dwelling minions.

“In 1930, a little girl named Venetia Burney suggested that Clyde Tombaugh name his newly discovered planet ‘Pluto.’ Tombaugh liked the idea and the name stuck. I like to think that we are doing honor to Tombaugh’s legacy by now opening up the naming of Pluto’s two tiniest known moons to everyone.”

– Mark Showalter, SETI Institute

As of the time of this writing, the ongoing results look like this:

Results of Pluto Rocks voting as of Feb. 11, 2013 at 10 am EST (15:00 UT)

Do you like where the voting is headed? Are you hellishly opposed? Go place your vote now and make your opinion count in the naming of these two distant worlds!

(After all, New Horizons will be visiting Pluto in just under two and a half years, and she really should know how to greet the family.)

Voting ends at noon EST on Monday, February 25th, 2013.

The SETI team welcomes you to submit your vote every day, but only once per day so that voting is fair.

UPDATE: On Feb. 25, the final day of voting, the tally is looking like this:

PlutoRocks results as of Feb. 25, 2013 - Vulcan is in the lead, thanks to publicity from Mr. William Shatner — PlutoRocks results as of Feb. 25, 2013 – Vulcan is in the lead, thanks to publicity from Mr. William Shatner

Thanks in no small part to a bit of publicity on Twitter by Captain Kirk himself, Mr. William Shatner (and support by Leonard Nimoy) “Vulcan” has made the list and warped straight to the lead. Will SETI and the IAU honor such Trek fan support with an official designation? We shall soon find out…

November 21, 2012December 23, 2015 by Jason Major

Makemake’s Mysteriously Missing Atmosphere

Artist’s impression of the surface of Makemake, a dwarf planet beyond Pluto (ESO/L. Calçada/Nick Risinger)

It turns out there’s no air up there: the distant dwarf planet Makemake is surprisingly lacking in an atmosphere, according to findings made by astronomers using telescopes at ESO’s La Silla and Paranal observatories.

An international team of astronomers used the mountaintop telescopes to observe Makemake as it passed in front of a faint background star in April 2011, a brief stellar occultation that lasted only about a minute. By watching how the starlight was blotted out by Makemake, measurements could be made of the dwarf planet’s size, mass and atmosphere — or, in this case, its lack thereof… a finding which surprised some scientists.

“As Makemake passed in front of the star and blocked it out, the star disappeared and reappeared very abruptly, rather than fading and brightening gradually. This means that the little dwarf planet has no significant atmosphere,” said team leader José Luis Ortiz of the Instituto de Astrofísica de Andalucía in Spain. “It was thought that Makemake had a good chance of having developed an atmosphere — that it has no sign of one at all shows just how much we have yet to learn about these mysterious bodies.”

First discovered in 2005, Makemake is an icy dwarf planet about 2/3 the diameter of Pluto — and 19 AU further from the Sun (but not nearly as far as the larger Eris, which is over 96 AU away.) It was thought that Makemake might have a tenuous, seasonal atmosphere similar to what has been found on Pluto, but it now appears that it does not… at least not in any large-scale, global form.

Due to its small size, sheer distance and apparent lack of moons, making scientific observations of Makemake has been a challenge for astronomers. The April 2011 occultation allowed measurements to be made — even if only for a minute — that weren’t possible before, including first-ever calculations of the dwarf planet’s density and albedo.

As it turns out, Makemake’s albedo is about 0.77 — comparable to that of dirty snow… a reflectivity higher than Pluto’s but lower than that of Eris. Its density is estimated to be 1.7 ± 0.3 g/cm³, indicating a composition of mostly ice with some rock.

“Our new observations have greatly improved our knowledge of one of the biggest [icy bodies], Makemake — we will be able to use this information as we explore the intriguing objects in this region of space further,” said Ortiz.

New Horizons May Need to ‘Bail Out’ to Dodge Debris, Rings and Moons in the Pluto System

Artist’s concept shows the New Horizons spacecraft during its 2015 encounter with Pluto and its moon, Charon. Credit: JHUAPL/SwRI

Since the New Horizons spacecraft left Earth back in 2006, there are a few things we know about the Pluto system now that we didn’t know then. For instance, it was discovered Pluto has two additional small moons – P4 and P5 — and Alan Stern, New Horizons Principal Investigator, said Pluto may have a large system of moons to be discovered as the spacecraft gets closer. There are also comets, possibly more dwarf planets and other objects out in the Kuiper Belt region where Pluto orbits.

“That’s exciting,” Stern said, “but this is a mixed story.”

Stern told Universe Today that while the spacecraft possibly could come upon an undiscovered moon or Kuiper Belt Object and they would have to alter course, the biggest issue is tiny debris which may be coming from impacts on the smaller moons.

“We could have 100 moons the size of P4 and they would not be a significant hazard,” Stern said via email. “The hazard is from ejecta coming off these satellites when they are cratered, because the ejecta escapes their feeble gravity and gets into orbit around Pluto.”

At a press conference at the American Astronomical Society’s Division for Planetary Sciences meeting, Stern said that with all the debris in the Kuiper Belt, objects are definitely getting impacted. “If hits occur on Pluto and Charon, they have enough gravity that ejecta just flies across the planet and creates secondary craters. But the ejecta on smaller moons puts shards and debris into the Pluto system.”

Stern said the ejecta speeds from these moons would be comparable to orbital speeds. That means the debris can orbit at any inclination, and there could be a cloud of debris around the system, creating a hazard for the spacecraft.

This worries Stern and his team.

“My spacecraft is going very fast and even a strike from something as small as a BB would be fatal,” he said. “There’s almost no place the spacecraft could get hit and it would be OK.”

Stern said current knowledge of the density of debris of the system can’t prove the spacecraft won’t get hit, and they won’t be able to find out more until they get closer.

“We’re going somewhere new and have no direct evidence of debris that could pose an impact hazard,” he said. “We don’t know what we are going to find and we might have to change our course.”

Stern and his team are looking at some alternative plans, and developing them now is crucial.

“When we plan an encounter for a mission like this, it literally takes tens of thousands of man-hours by experts to put that sequence together and test it,” he said. “We have to plan them now in order to complete that planning. We can’t complete them in the last couple of months or weeks.”

The plans being considered are called SHBOT: Safe Haven Bail Out Trajectory. They currently have nine different possible trajectories, depending on what they find as they get closer.

Screenshot from Stern’s presentation, depicting the nine SHBOT trajectories.

The team is also using every available tool — including sophisticated computer simulations of the stability of debris orbiting Pluto, giant ground-based telescopes, stellar occultation probes of the Pluto system, and even the Hubble Space Telescope — to search for debris in orbit.

Stern told Universe Today that they use the cameras on New Horizons itself every summer when they “wake up” the spacecraft. “LORRI (Long Range Reconnaissance Imager) has already seen Pluto for about 6 years!” he said, “But we won’t pass HST resolution till we’re about 10 weeks out, in April 2015. That’s when we turn on the heavy effort to look for more moons, rings, etc.”

They are looking at the pluses and minuses for each of the plans so they can be tested and be just as “bullet-proof” as the original, nominal flight plan.

In addition to saving the spacecraft, these alternative trajectories also need to preserve the science mission as much as possible. Most of the alternate courses bring the spacecraft farther away from the Pluto system, but one actually brings it closer to Charon, as the path there may be clearer there because of Charon’s gravity and clearing effect.

The spacecraft will start science observations in January 2015, with closest approach to the system currently set for on July 14, 2015 (“Bastille Day,” Stern said, “when we storm the gates of the Pluto system!”)

During the final 50 days of approach, when the spacecraft is taking pictures and sending them back to Earth to be analyzed, the team may discover something and have to fire the spacecraft engines, putting them on one of the SHBOT trajectories. But the last opportunity to actually change course is 10 days before encounter.

“After that we are in too close and we would run out of fuel and not complete the maneuver,” Stern said.

So, while the Mars Science Laboratory team had “Seven minutes of terror” during the perilous landing on Mars, Stern said they have something similar. “We don’t have seven minutes of terror; we have seven weeks of suspense.”

September 26, 2012April 26, 2016 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)

August 30, 2012April 26, 2016 by Jason Major

What Has the Kuiper Belt Taught Us About The Solar System?

Over 4 billion miles (6.7 billion km) from the Sun, the Kuiper Belt is a vast zone of frozen worlds we still know very little about. Image: Johns Hopkins University Applied Physics Laboratory/Southwest Research Institute (JHUAPL/SwRI)

Today marks the 20th anniversary of the discovery of the first Kuiper Belt Object, 1992QB1. KBOs are distant and mostly tiny worlds made up of ice and rock that orbit the Sun at incredible distances, yet are still very much members of our Solar System. Since 1992 over 1,300 KBOs have been found, and with NASA’s New Horizons spacecraft speeding along to its July 2015 rendezvous with Pluto and Charon (which one could argue are technically the first KBOs ever found) and then onwards into the Belt, we will soon know much more about these far-flung denizens of deep space.

But how has the discovery of the Kuiper Belt — first proposed by Gerard Kuiper in 1951 (and in a fashion even earlier by Kenneth Edgeworth) — impacted our current understanding of the Solar System? New Horizons Principal Investigator Alan Stern from the Southwest Research Institute recently discussed this on his mission blog, “The PI’s Perspective.”

First, Stern lists some of the surprisingly diverse physical aspects of KBOs that have been discovered so far:

Some are red and some are gray;
The surfaces of some are covered in water ice, but others (like Pluto) have exotic volatile ices like methane and nitrogen;
Many have moons, though none with more known moons than Pluto;
Some are highly reflective (like Pluto), others have much darker surfaces;
Some have much lower densities than Pluto, meaning they are primarily made of ice. Pluto’s density is so high that we know its interior is about 70% rock in its interior; a few known KBOs are more dense than Pluto, and even rockier!

But although these features are fascinating in themselves, just begging for further exploration, Stern notes that there are three very important lessons that the Kuiper Belt has taught us about the Solar System:

1. Our planetary system is much larger than we had ever thought.

“In fact, we were largely unaware of the Kuiper Belt — the largest structure in our solar system — until it was discovered 20 years ago,” Stern writes. “It’s akin to not having maps of the Earth that included the Pacific Ocean as recently as 1992!”

2. Planetary locations and orbits can change over time.

“This even creates whole flocks of migration of planets in some cases. We have firm evidence that many KBOs (including some large ones like Pluto), were born much closer to the Sun, in the region where the giant planets now orbit.”

3. Our solar system, and likely others as well, was very good at making small planets.

“Today we know of more than a dozen dwarf planets in the solar system, and those dwarfs already outnumber the number of gas giants and terrestrial planets combined. But it is estimated that the ultimate number of dwarf planets we will discover in the Kuiper Belt and beyond may well exceed 10,000. Who knew?”

And with a little jab at the whole Pluto-isn’t-a-planet topic, Stern asks: “And which class of planet is the misfit now?”

Read: Was Pluto Ever REALLY a Planet?

The discovery of the Kuiper Belt has shown us that our solar system — and very likely planetary systems across the galaxy, even the Universe — aren’t neat and tidy things that can be easily summed up with grade-school models or chalkboard diagrams. Instead they are incredibly diverse and dynamic, continually evolving and consisting of countless, varied worlds spanning enormous distances… yet still connected through the ever-present effects of gravity (not to mention the occasional-yet-unavoidable collision.)

“What an amazing set of paradigm shifts in our knowledge the Kuiper Belt has brought so far. Our quaint 1990s and earlier view of the solar system missed its largest structure!”

– Alan Stern, New Horizons Principal Investigator

Read more about the New Horizons mission here.

The first KBO identified, 1992 QB1 (European Southern Observatory)

July 11, 2012December 23, 2015 by Jason Major

Fifth Moon Found Around Pluto

This just in! Astronomers working with the Hubble Space Telescope have spotted a new moon around distant Pluto, bringing the known count up to 5. The image above was released by NASA just minutes ago, showing the Pluto system with its newest member, P5.

This news comes just a couple of weeks shy of the one-year anniversary of the announcement of Pluto’s 4th known moon, still currently named “P4”.

The news was shared this morning by an undoubtedly excited Alan Stern of the Southwest Research Institute (SwRI) on Twitter.

Astronomers estimate P5 to be between 6 and 15 miles (9.6 to 24 km) in diameter. It orbits Pluto in the same plane as the other moons — Charon, Nix, Hydra and P4.

“The moons form a series of neatly nested orbits, a bit like Russian dolls,” said team lead Mark Showalter of the SETI Institute.

A mini-abstract of an upcoming paper lists image sets acquired on 5 separate occasions in June and July. According to the abstract, P5 is 4% as bright as Nix and 50% as bright as P4.

The satellite’s mean magnitude is V = 27.0 +/- 0.3, making it 4 percent as bright as Pluto II (Nix) and half as bright as S/2011 (134340) 1. The diameter depends on the assumed geometric albedo: 10 km if p_v = 0.35, or 25 km if p_v =0.04. The motion is consistent with a body traveling on a near-circular orbit coplanar with the other satellites. The inferred mean motion is 17.8 +/- 0.1 degrees per day (P = 20.2 +/- 0.1 days), and the projected radial distance from Pluto is 42000 +/- 2000 km, placing P5 interior to Pluto II (Nix) and close to the 1:3 mean motion resonance with Pluto I (Charon).

The new detection will help scientists navigate NASA’s New Horizons spacecraft through the Pluto system in 2015, when it makes an historic and long-awaited high-speed flyby of the distant world.

See the news release from NASA here.

(H/T to Ray Sanders at DearAstronomer.com)

Top image: NASA, ESA and M. Showalter (SETI Institute)

May 31, 2012December 23, 2015 by Jason Major

Was Pluto Ever REALLY a Planet?

Ever since the infamous 2006 reclassification of Pluto off the list of “official” planets (which had a rather incendiary effect on many of the distant world’s Earthly fans) the term “planet” has been seen by some as a variable one, difficult to define and apparently able to be given and taken away. But was Pluto ever really deserving of the title to begin with?

This fun info-animation by C.G.P. Grey suggests that it wasn’t, and offers a compelling explanation why.

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Grey writes on his blog:

“To my constant surprise the issue of Pluto’s planetary status — which I think should be a dry technical issue — really gets people riled. But it’s also been my experience that the people who most want Pluto to be a planet know the least about it and the history of its discovery. So, I hope that this video can help correct that a little bit.”

We still love you, Pluto, no matter what you are!

See more of Grey’s excellent animations on YouTube here.