Can you believe it? We’re less than a month away from NASA’s New Horizons‘ historic flight past the dwarf planet Pluto. I’m sure you’ve got a zillion questions about the mission and want to hear how everything’s going.
Well, you’re in luck. Primary investigator Alan Stern, as well as several member of the science team and NASA will be on hand on Friday, June 19th at 11:30 am PDT (2:30 pm EDT) to have a special Google+ Hangout on Air just to talk about the mission. They’ll also be interacting with the audience and answering your questions about the mission.
Want to watch it live? Click here and then select that you’re going to attend. That’ll put the event right into your calendar. Then come back at 11:30/2:30 on Friday and watch it live.
New Horizons infographic about the Pluto encounter.
Are you ready for New Horizons’ flyby of Pluto? The science and engineering team reports they are ready for action, with the spacecraft on track and all systems functioning, with closest approach on July 14, 2015.
To get the rest of us ready, the National Space Society has put together a stirring video of the New Horizons mission. It was directed and produced by Erik Wernquist, who created another stirring video last year, Wanderers, which looks to the future of solar system exploration. For this new video, New Horizons principal investigator Alan Stern served as advisor.
“As both an NSS member and the Principal Investigator of New Horizons, I’m excited about this beautiful film – and very appreciative of the efforts of NSS and its sponsors to create this. It really is stirring; I hope you’ll think so too,” said Stern.
You can read the latest update from the New Horizons team here, which includes information about the third and final far encounter science phase, called Approach Phase 3, which runs until seven days before Pluto close approach. Additionally, the team is on the lookout for possible hazards for the spacecraft, e.i., new moons, rings or other space debris that might present hazards to the fast-moving spacecraft when it flies through the Pluto system. They’ve been analyzing the latest images from the spacecraft and so far it looks all clear.
“Every day we break a new distance record to Pluto, and every day our data get better,” said Stern. “Nothing like this kind of frontier, outer solar system exploration has happened since Voyager 2 was at Neptune way back in 1989. It’s exciting–come and watch as New Horizons turns points of light into a newly explored planetary system and its moons!”
Additionally, @NewHorizons2015 just tweeted out a great infographic about the encounter:
This set of computer modeling illustrations of Pluto’s moon Nix shows how the orientation of the moon changes unpredictably as it orbits the “double planet” Pluto-Charon.
Credit: NASA/ESA/M. Showalter (SETI)/G. Bacon (STScI)
Simulation of Pluto’s moon Nix sped up so that one orbit takes 2 seconds instead of 25 days.
Wobbling and tumbling end-over-end like a badly thrown football, Pluto’s moons are in a state of orbital chaos, say scientists. Analysis of data from NASA’s Hubble Space Telescope shows that two of Pluto’s moons, Nix and Hydra, wobble unpredictably. If you lived on either, you’d never know when and in what direction the Sun would rise. One day it would pop up over your north horizon, the next over the western. Every sunset would be like a proverbial snowflake — not a single one the same.
Watch the video, and you’ll see what I mean. Not only does the moon totter, but the poles flip. If there was ever a solar system body to meet the criteria of end-of-the-world, doomsday crowd, Nix is it. The moons wobble because they’re embedded in the bizarro gravity field of the Pluto-Charon duo. Charon is officially the dwarf planet’s largest moon, but the two bodies act more like a double planet because Charon’s so huge.
OK, it’s only 750 miles (1,212 km) in diameter, but that’s half as big as Pluto. Imagine if our moon was twice as big as it is now, and you get the picture.
Charon is large compared to Pluto, so they orbit about their common center of gravity located in the space between the two bodies. Credit: Wikipedia
As the duo dances an orbital duet about their common center of gravity, their variable gravitational field sends the smaller moons tumbling erratically. The effect is enhanced even more by their irregular and elongated shapes. It’s likely Pluto’s other two moons, Kerberos and Styx, are in a similar situation.
Because their moment to moment motions are essentially unpredictable, scientists describe their behavior is chaotic. Saturn’s moon, Hyperion, also tumbles chaotically.
Pluto (upper right) and its largest moon Charon form a “double planet” as seen in this photo taken by NASA’s New Horizons probe which is set to make a close flyby of the Pluto system on July 14. Credit: NASA / NASA / Johns Hopkins University Applied Physics Laboratory / Southwest Research Institute
The discovery was made by Mark Showalter of the SETI Institute and Doug Hamilton of the University of Maryland using the Hubble Space Telescope and published in today’s issue of the journal Nature. Showalter also found three of Pluto’s moons are presently locked together in resonance, meaning there’s a precise ratio for their orbital periods.
“If you were sitting on Nix, you would see that Styx orbits Pluto twice for every three orbits made by Hydra,” said Hamilton.
That’s not all. If you’ve ever grilled with charcoal, you’d have a good idea what Kerberos looks like. Dark as one those briquettes. The other moons are as bright as sand because they’re mostly made of ice. Astronomers had thought that material blasted off the moons by meteorite impacts should make them all the same basic tone, so what’s up with Kerberos? No one knows.
This illustration shows the scale and comparative brightness of Pluto’s small satellites. The surface craters are for illustration only and are not real. Credits: NASA/ESA/A. Feild (STScI)
Pluto’s moons are thought to have formed during a collision long ago between the dwarf planet and a similar-sized object. The smash-up created lots of smaller bodies that eventually took up orbits about the present-day Pluto. Outside of Charon, the biggest leftover, the other moons measure in the tens of miles across. The four little ones — Nix, Styx, Kerberos and Hydra — were discovered with the Hubble scope during surveys to better map the Pluto system before New Horizons arrives next month. No one would be surprised if even more itty-bitty moons are found as we draw ever closer to the dwarf planet.
A view of Pluto Safari on an iPhone. Image via Simulation Curriculum.
If you’re like us, you’ve been following the news closely as the New Horizons mission speeds towards Pluto. Want to follow it even closer? Check out the free Pluto Safari app now available from the developers that brought us the award winning astronomy app ‘SkySafari 4.’ It is available in both iOS and Android.
The fully interactive Pluto Safari provides a countdown in time and distance for when New Horizons will reach Pluto on July 14, 2015. It will also give you the latest position of New Horizons and Pluto, providing 3-D views of the Solar System and the Pluto system, as well as 3-D models of the spacecraft. By using the Time Controls, you can run through the mission, backwards or forwards, to see the mission step-by-step. Just so you don’t get lost in time and space, the status bar always displays the current date, time and location.
Views of Pluto Safari on iPads. Image via Simulation Curriculum.
The app will also show you where Pluto is located in the sky from your location. Who doesn’t want to look up in the exact spot where Pluto is, knowing that New Horizons is there too? But the app allows you to do even more: the simulator provides an accurate depiction of the sky, and you can touch and drag to change the direction you are looking, and zoom in and out to adjust your field of view.
Pedro Braganca from Simulation Curriculum, the company that developed the app told Universe Today that the info on the app will be updated throughout the mission as new data becomes available. Simulation Curriculum created the 3D model of the spacecraft, but the surface texture maps for Pluto and Charon were created by Marc Buie of the Southwest Research Institute.
“The maps are both scientifically accurate (from Hubble data) and aesthetically pleasing,” Braganca said via email. “Obviously we’ll replace these textures with the ‘real’ Pluto map whenever that gets released post-flyby.”
Pluto Safari on Android devices. Image via Simulation Curriculum.
If you’re newbie and only now hearing about the New Horizons mission, you can go back in time to review the mission since it launched on January 19, 2006, and explore all the mission milestones in the interactive Solar System Simulator. There’s also a detailed multimedia guide to Pluto and its history.
Want to give a piece of your mind to the IAU for the controversial demotion Pluto to a dwarf planet? The app has a “poll” that also allows you to weigh in on Pluto’s planet status.
You’ll also get alerts to the latest news from New Horizons on the milestones, data, and discoveries.
Pluto Safari’ has interactive educational activities. Image via Simulation Curriculum.Additionally, Pluto Safari has interactive educational information for all ages.
Braganca shared an interesting story about they worked with JPL to get even intricate details in the app correct.
“On the orbital/trajectory data side, when we were developing the simulation of the Pluto-New Horizons encounter, we were unable to show New Horizons passing through Pluto’s shadow,” he said via email. “Our calculations appeared to be correct, and we were using the latest position data available for Pluto/NH from JPL Horizons – so it was a bit of a mystery. To help us figure this out, we contacted Jon Giorgini, Senior Analyst at JPL. Jon confirmed that the latest New Horizons maneuver was not yet modeled in the spacecraft reference trajectory. There was also a couple thousand km uncertainty in the Pluto system barycentric position, as determined from the ground. Jon updated the JPL Horizon data to the latest available information and we were then in close agreement with the Pluto-encounter with the new values.”
You can use the app from the desktop on your computer if want a larger view than on your phone by going to the app’s website, PlutoSafari.com.
To download Pluto Safari for iOS 7 and later, click here.
To download Pluto Safari for Android 4.1 and later, click here.
As New Horizons gets ever-closer to Pluto, Pluto Safari provides a great way to feel like part of the mission.
“The New Horizons Pluto flyby is a rare chance for science to touch the general public,” said Braganca. “With a free app, we’re capturing a new generation at this teachable moment. The Voyager missions of the 1980s inspired engineers who went on to develop today’s mobile technologies. Who knows we might inspire today’s young learners to accomplish 30 years from now?”
These images show Pluto in the latest series of New Horizons Long Range Reconnaissance Imager (LORRI) photos, taken May 8-12, 2015. Hints of possible complex surface geology and the polar cap first seen in April are visible. Credit: NASA
Hey Pluto, it’s great to see your face! Since sending its last batch of images in April, NASA’s New Horizons probe lopped off another 20 million miles in its journey to the mysterious world. Among the latest revelations: the dwarf planet displays a much more varied surface and the bright polar cap discovered earlier this spring appears even bigger.
Comparison of the April image of one hemisphere of Pluto with the same hemisphere photographed in May. The photos have been rotated to align Pluto’s rotational axis with the vertical direction (up-down), as shown schematically in the center panel. Between April and May, Pluto grew larger as the spacecraft got closer, with Pluto’s apparent size increasing by approximately 50%. Pluto rotates around its axis every 6.4 Earth days; this and the images below show the variations in Pluto’s surface features during its rotation. Credit: NASA
“These new images show us that Pluto’s differing faces are each distinct; likely hinting at what may be very complex surface geology or variations in surface composition from place to place,” said New Horizons Principal Investigator Alan Stern, of the Southwest Research Institute in Boulder, Colorado.
Compare Pluto’s polar cap (white spot at top of the globe), first seen in April (left) with the latest image taken on May 10. Approximately the same face of Pluto is shown in both images. The cap’s extent varies with longitude. Credit: NASA
Mission scientists caution against over-interpreting some of the smaller details. The photos have been processed using a method called deconvolution, which strips away the out-of-focus information to enhance features on Pluto. Deconvolution can occasionally add “false” details or artifacts, so the smallest features in these pictures will need to be confirmed by images taken from closer range in the next few weeks.
Pluto compared on April 16, 2015 and May 12. Credit: NASA
Compared to recent photos of Ceres, the other dwarf planet in the limelight this season, Pluto shows only light and dark blotches. That’s how Ceres started out too. All those variations in tone and texture suggest a fascinating and complex surface. And it’s clear that the polar cap — whatever it might ultimately be — is extensive and multi-textured. The images were taken from a little less than 50 million miles (77 million km) away or about the same distance Mars is from Earth during a typical opposition.
New Horizons current position and particulars on May 28, 2015. Credit: NASA
Watch for dramatic improvements in the images as New Horizons speeds toward its target, covering 750,000 miles per day until closest approach on July 14. By late June, they’ll have four times the resolution; during the flyby that will improve to 5,000 times. The spacecraft is currently 2.95 billion miles from Earth. Light, traveling at 186,00o miles per second, requires 8 hours and 47 minutes – the length of a typical work day – to make the long round trip.
The overview of the New Horizon journey to the binary system of Pluto and Charon. The NASA probe is now surpassing Hubble imagery. (Photo Credit: NASA/New Horizons)
The latest set of images from the long range imager, LORRI, on New Horizons now reveals surface features. At a press conference today, exhilarated NASA scientists discussed what the images are now suggesting. (Photo Credit: NASA/New Horizons)
Today, a trio of NASA scientists expressed their exhilaration with the set of new Pluto images released by the New Horizons team. “Land Ho” exclaimed Dr. Alan Stern as he first tried to explain where they are on their long journey. Nearly 500 years ago, not even Magellan on a three year journey to circumnavigate the Earth waited so long. A ten year journey is beginning to reveal fascinating new details of the dwarf planet Pluto, once the ninth planet of our Solar System. The latest images show surface features on Pluto suggesting polar caps.
A team effort that Dr. Weaver said called upon leading experts to resolve these newest details of Pluto’s surface. The inset at left shows schematically the geographic relationship of the two bodies as they orbit each other. The inset at right shows surface details at 3x maximum resolution. (Photo Credit: NASA/New Horizons)
The NASA press conference took place this afternoon, anchored by Dr. John Grunsfeld, Associate Administrator for the Science Mission Directorate who quickly turned over the discussion to the project scientist of the New Horizons mission, Dr. Alan Stern from the Southwest Research Institute of San Antonio, Texas. Grunsfeld began by stating NASA’s mission – “to explore, discover and inspire” and added that New Horizons is certainly executing these prime objectives.
The overview of the New Horizon journey to the binary system, Pluto and Charon, and beyond. The NASA probe is now surpassing Hubble imagery. (Photo Credit: NASA/New Horizons)
Alan Stern started off by expressing his excitement with the latest results from the long range telescope on board New Horizons, LORRI, but emphasized he represents a team effort, the culmination of decades of work.
With just 11 weeks remaining and now 98% of the way to Pluto, the latest set of images from LORRI have now revealed details better than the best that was previously attainable – from the Hubble Space Telescope. Most incredible are indications of polar caps on the dwarf planet Pluto.
Until now, the Hubble space telescope had shown tantalizing but mottled features of the surface of Pluto (Photo Credit: NASA)
Dr. Stern, stated that the 25th Anniversay of the Hubble mission has also functioned as a segue to what is about to unfold from New Horizons. Until now, the best images of Pluto’s surface had been wrestled out of images from Hubble with computer processing. Yet, at the present distance New Horizons remains, his team is still relying on image processing to reveal these first surface details.
The gravitational tug of war of the unique binary system has forced both small bodies to forever face each other, similar to how our Moon always faces the Earth. (Photo Credit: NASA/New Horizons)
Dr. Stern stated how remarkable the Pluto-Charon system is. The earlier set of LORRI images from 2014 had shown the gravitational dance of the two small bodies. He stated that they are truly a binary system and a type we have never explored before. Pluto-Charon is a dual synchronous, tidally locked system. Dr. Stern explained that the Earth, close-in to the Sun, and their space probe New Horizons, now on its final approach, is viewing the sunlit side of Pluto and Charon.
The system is tipped over relative to its orbital plane around the Sun. Dr. Stern stated, “it is like watching Pluto rotate on a spit.” He said that we are nearly seeing it face on; similar to an observer hovering far above the Earth’s polar cap and looking down upon the Earth-Moon system. The orbits of the two bodies, as seen in the LORRI image sequence (animations, above), appear elliptical (oval), however, due to the extreme and final state of this binary system, the orbits are perfect circles; the eccentricities are zero! New Horizons is just approaching slightly off center.
Images of the New Horion space probe shows its compactness, necessarily to minimize weight, volume, power demands and achieve the high velocity necessary to reach Pluto in nine years. Af left the instruments are shown included the long range imager, LORRI. (Photo Credit: NASA/New Horizons)
Dr. Stern continued and explained how this latest set is now showing surface features on Pluto. The features “are suggesting the presence of polar caps”, however he also emphasized that it remains only suggestive until New Horizons can deliver more details, that is, higher resolution, color imagery from the Ralph imager and spectroscopic data (Ralph and Alice imaging spectrometers) to reveal composition. Dr. Stern turned over the press conference to Dr. Hal Weaver of John Hopkins’ Applied Physics Laboratory, the lead scientist for the LORRI instrument.
LORRI, the Long Range Reconnaissance Imager, shown through details of a schematic. (Credit: NASA/New Horizons)
LORRI as Dr. Weaver explained is a state-of-the-art instrument. A fixed focus telescopic camera, functional from room temp down to 180 degees Fahrenheit below zero and utilizes an 8 inch primary mirror. The optical quality is extraordinary but the light gathering power is the same as one has in an amateur 8 inch telescope such as offered by Meade or Celestron. Still further, Dr. Weaver stated that LORRI is also extremely efficient and ligthweight, using less than 5 watts of power and weighing less than 20 lbs.
New York City’s Manhattan is shown as an example of the resolving power the Ralph multi-spectral imager will have at closest approach to Pluto and Charon (Photo Credit: NASA/New Horizons)
Dr. Weaver explained how the raw images from LORRI are presently little more than blotches of light, unspectacular at first glance, but with image processing, the details discussed today are revealed. The New Horizons team employed world-class experts in the technique of Image Deconvolution. It was again Hubble that spawned “a cottage industry”, over 20 years ago, including one expert – Todd Lauer of the National Optical Astronomy Observatory. Lauer and others took on the challenge of extracting quality imagery from the Hubble space telescope as it struggled with the astigmatism accidentally built into its optical system. A NASA Space Shuttle mission delivered and inserted a corrective lens into Hubble which has made its 25 years of service possible.
Without the imaging processing technique of deconvolution, the latest images of Pluto are mere blotches. Dr. Weaver credited experts born from the Hubble astigmatism from 20 years ago. (Photo Credit: NASA/New Horizons)
And the New Horizons’ processed images are now slightly better than Hubble and will just get much better. From the Q&A with the press. Weaver explained that while the images show more detail, Earth-based and Hubble images remain more light sensitive. Hubble sets an upper limit to the size of any remaining moons to be discovered. Weaver stated that by June, New Horizons’ LORRI will exceed the light sensitivity limits of Hubble. If there are more moons to be found, June will be the month.
An artist’s illustration of Pluto. With a tenuous atmosphere that has so far defied explanations, New Horizons is altogether revealing a light red – peach – colored surface but with large contrasting areas of white and dark red. (Illust. Credit: NASA/New Horizons)
Through the Q&A, Dr. Stern stated that an extraordinary aspect of Pluto’s atmosphere is that the planet’s atmosphere has continued to expand despite having passed a point in its orbit at which it should be freezing and condensing onto its surface. The atmosphere expanded 200 to 300% in the last decade. With the limited observations, Stern and other Pluto experts surmise that there is a lag in the climate akin to how our hottest months lag the beginning of Summer by a couple of months. Perhaps, a latent heat stored up in the near surface has continued to vaporize frozen gases thus building up the atmosphere more than first expected.
The composition of the dwarf planet’s surface was discussed. Most evident in Earth-based spectroscopy is that there is molecular nitrogen, carbon monoxide and methane. Stern stated they these species of molecules could explain the bright and dark spots of the surface. However, he emphasized that Pluto is composed of 70% rock by mass and the remaining is ice. Charon stands in remarkable contrast to Pluto. Chraon has primarily water and ammonia hydrates on its surface; no detectable atmosphere (so far). Charon’s appearance is much more uniform and bland. Altogether, Stern said that experts call this the Pluto-Charon dichotomy.
The present approach at 60 million miles to Pluto is just the beginning of the story of New Horizons’ study of the primary targets. This press conference illustration explains near-term plans. (Illust. Credit: NASA/New Horizons)
Dr. Stern near the end of the press conference restated that this is truly “my meet Pluto moment.” New Horizons is like a plane on its final approach to touchdown but New Horizons cannot slow down. There are no retro-rockets, no propulsion onboard that can slow down the probe on its trek to escape the gravity of the Sun. The probe will join the Pioneer and Voyager space probes as the only Human-made objects to leave the Solar System. With its final approach, with every day, Pluto and Charon closes in as Dr. Stern and Dr. Weaver explained, Pluto’s image will fill the full breadth of the imaging detector. Details on its surface will be equivalent to high resolution images of New York’s Manhattan (figure, above) showing details such as the ponds in Central Park.
To continue following the latest release of images from New Horizons go to http://www.nasa.gov/newhorizons/lorri-gallery.
New Horizons spacecraft by Johns Hopkins University Applied Physics Laboratory/Southwest Research Institute
Are you excited about the upcoming NASA New Horizons flyby to Pluto? Even though the flyby will happen on July 14, 2015, Pluto is getting closer and closer in the spacecraft’s cameras. And there’s lots of science to be done between now and then.
Join me today, Friday April 3 at 10 am PDT / 1 pm EDT for a special Hangout with NASA and members from the New Horizons science team to discuss the state of the mission and what we can expect over the next few months as we finally meet Pluto up close. Ask the team your questions live.
We’ll be joined by:
Jim Green (NASA Headquarters, Planetary Science Division Director)
Alan Stern (SWRI, Principle Investigator on New Horizons)
ILLUSTRATION IS RESERVED - DO NOT USE. The eight planets of the Solar System and the dwarf planet Pluto. For many astronomers and planetary scientists Pluto's status remains an open question. Redefining what is a planet could return Pluto to the fold - 9 planets and also open the door for many more. Insets from upper left, clockwise: Clyde Tombaugh, Mike Brown, Alan Stern, Gerard Kuiper.(Credit: NASA, Judy Schmidt, Björn Jónsson)
A storm is brewing, a battle of words and a war of the worlds. The Earth is not at risk. It is mostly a civil dispute, but it has the potential to influence the path of careers. In 2014, a Harvard led debate was undertaken on the question: Is Pluto a planet. The impact of the definition of planet and everything else is far reaching – to the ends of the Universe.
It could mean a count of trillions of planets in our galaxy alone or it means leaving the planet Pluto out of the count – designation, just a dwarf planet. This is a question of how to classify non-stellar objects. What is a planet, asteroid, comet, planetoid or dwarf planet? Does our Solar System have 8 planets or some other number? Even the count of planets in our Milky Way galaxy is at stake.
“Dawn arising.” The latest image of Ceres – February 12, 2015 – by the Dawn spacecraft from 80,000 km. With icy deposits pock marking its surface, a possible reservoir of water below its surface, is Ceres a planet, dwarf planet, an asteroid or all three? (Credit: NASA/Dawn)
Not to dwell on the Harvard debate, let it be known that if given their way, the debates outcome would reset the Solar System to nine planets. For over eight years, the solar system has had eight planets. During the period 1807 to 1845, our Solar System had eleven planets. Neptune was discovered in 1846 and astronomers began to discover many more asteroids. They were eliminated from the club. This is very similar to what is now happening to Pluto-like objects – Plutoids. So from 1846 to 1930, there were 8 planets – the ones as defined today.
The discoverer of Pluto – Clyde Tombaugh in the 1930s and again with homebuilt telescope in the 1990s that earned him an assignment at Lowell Observatory – discover Planet X. The cremated remains of Clyde are attached to the New Horizons space probe that is now approaching the dwarf planet Pluto.
In 1930, a Kansas farm boy, Clyde Tombaugh, hired by Lowell Observatory discovered Pluto and for 76 years there were 9 planets. In the year 2006, the International Astronomical Union (IAU) took up a debate using a “democratic process” to accept a new definition of planet, define a new type – dwarf planet and then set everything else as “Small Bodies.” If your head is spinning with planets, you are not alone.
All two body systems have a barycenter, the shared point in space around which they orbit. Pluto and Charon’s happens to be between both bodies due to their proximity and similar mass. (Credit: NASA/New Horizons)
Two NASA missions were launched immediately before and after the IAU announcement took affect. The Dawn mission suddenly was to be launched to an asteroid and a dwarf planet and the New Horizons had rather embarked on a nine year journey to a planet belittled to a dwarf planet – Pluto. Principal Investigator, Dr. Alan Stern was upset. Furthermore, from the discoveries of the Kuiper mission and other discoveries, we now know that there are hundreds of billions of planets in our Milky Way galaxy; possibly trillions. The present definition excludes hundreds of billions of bodies from planethood status.
The presently known largest trans-Neptunian objects (TSO) – are likely to be surpassed by future discoveries. Which of these trans-Neptunian objects (TSO) would you call planets and which “dwarf planets”? (Illustration Credit: Larry McNish, Data: M.Brown)
There are two main camps with de facto leaders. One camp has Dr. Mike Brown of Caltech and the other, Dr. Stern of the Southwest Research Institute (SWRI) as leading figures. A primary focus of Dr. Brown’s research is the study of trans-Neptunian objects while Dr. Sterns’s activities are many but specifically, the New Horizons mission which is 6 months away from its flyby of Pluto. Consider first the IAU Resolution 5A that its members approved:
(1) A “planet” is a celestial body that (a) is in orbit around the Sun, (b) has sufficient mass for its self-gravity to overcome rigid body forces so that it assumes a hydrostatic equilibrium (nearly round) shape, and (c) has cleared the neighborhood around its orbit.
(2) A “dwarf planet” is a celestial body that (a) is in orbit around the Sun, (b) has sufficient mass for its self-gravity to overcome rigid body forces so that it assumes a hydrostatic equilibrium (nearly round) shape2, (c) has not cleared the neighbourhood around its orbit, and (d) is not a satellite.
(3) All other objects, except satellites, orbiting the Sun shall be referred to collectively as “Small Solar System Bodies”.
This is our starting point – planet, dwarf planet, everything else. Consider “everything else”. This broad category includes meteoroids, asteroids, comets and planetesimals. Perhaps other small body types will arise as we look more closely at the Universe. Within the category, there is now a question of what is an asteroid and what is a comet. NASA’s flybys of comets and now ESA’s Rosetta at 67P/Churyumov–Gerasimenko are making the delineation between the two types difficult. The difference between a meteoroid and an asteroid is simply defined as less than or greater than one meter in size, respectively. So the Chelyabinsk event absolutely involved a small asteroid – about 20 meters in diameter. Planetesimals are small bodies in a solar nebula that are the building blocks of planets but they could lead to the creation of all the other types of small bodies.
Dr. Alan Stern, project scientist for New Horizons and Neil deGrasse Tyson discuss the New Horizons spacecraft in the mission operations center at JHU/APL. The interview was for a NOVA special (12/14/2011), the Pluto Files, about a Kansas farm boy, a missing planet and the 70 years of astronomical discoveries leading to the present day. (Credit: JHU/APL,PBS)
Putting aside the question of “Small Bodies” and its sub-classes, what should be the definition of planet and dwarf planet? These are the two terms that demoted Pluto and raised Ceres to dwarf planet. It is also interesting to note how Resolution 5A is meant exclusively for our Solar System. In 2006, there were not thousands of exo-planets but just a few dozen extreme cases but nevertheless, the IAU did not choose to extend the definition to “stars” but rather just in reference to our pretty well known star, the Sun.
Recall Tim Allen’s movie, “The Santa Clause”. Clauses can cause a heap of trouble. The IAU has such a clause – Clause C which has caused much of the present controversy around the definition of planets. Clause (c) of Resolution 5A: “has cleared the neighborhood around its orbit.” This is the Pluto killer-clause which demoted it to dwarf planet status and reduced the number of planets in our solar system to eight. In a sense, the IAU chose to cauterize a wound, a weakness in the definitions, that if left unchanged, would have led to who knows how many planets in our Solar System.
The question of what is Pluto is open for public discussion so armed with enough knowledge to be dangerous, the following is my proposed alternative to the IAU’s that are arguably an improvement. The present challenge to Pluto’s status lies in the Kuiper Belt and Oort Cloud. Such belts or clouds are probably not uncommon throughout the galaxy. Plutoids are the 500 lb gorilla in the room.
Two spacecraft, Dawn and New Horizon will reach their final objectives in 2015 – Dwarf Planets – Ceres and Pluto. (Credit: NASA, Illustration – T.Reyes)
This year, as touted by the likes of Planetary Society, Universe Today and elsewhere, is the year of the dwarf planet. How remarkable and surprising will the study of Ceres, Pluto and Charon by NASA spacecraft be? There is a strong possibility that after the celestial dust clears and data analysis is published, the IAU will take on the challenge again to better define what is a planet and everything else. It is impossible to imagine that the definitions can remain unchanged for long. Even now, there is sufficient information to independently assess the definitions and weigh in on the approaching debate. Anyone or any group – from grade schools to astronomical societies – can take on the challenge.
To encourage a debate and educate the public on the incredible universe that space probes and advanced telescopes are revealing, what follows is one proposed solution to what is a planet and everything else.
planet: is a celestial body that a) has sufficient mass for its self-gravity to overcome rigid body forces so that it assumes a hydrostatic equilibrium – nearly round shape, b) has a differentiated interior as a result of its formation c) has insufficient mass to fuse hydrogen in its core, d) does not match the definition of a moon.
minor planet: is a planet with a mass less than one Pluto mass and does not match the definition of a moon.
inter-Stellar (minor) planet: is a (minor) planet that is not gravitationally bound to a stellar object.
binary (minor) planet: is a celestial body that is orbiting another (minor) planet for which the system’s barycenter resides above the surface of both bodies.
These definitions solve some hairy dilemmas. For one, planets orbit around the majority of most stars in the Universe, not just the Sun as Resolution 5A was only intended. Planets can also exist gravitationally not bound to a star – the result of it own molecular cloud collapse without a star or expulsion from a stellar system. One could specify gravitational expulsion however, it is possible that explosive events occur that cause the disintegration of a star and its binding gravity or creates such an impulse that a planet is thrusted out of a stellar system. Having an atmosphere certainly doesn’t work. Astronomers are already anticipating Mars or Earth-sized objects deep in the Oort cloud that could have no atmosphere – frozen out and also despite their size, not be able to “clear their neighborhood.”
An animation (above) of Kepler mission planet candidates compiled by Jeff Thorpe. Kepler and other exoplanet projects are revealing that the properties of planets – orbits, size, temperature, makeup – are all extreme. Does Pluto represent one of those extremes – the smallest of planets? (Credit: NASA/Kepler, Jeff Thorp)
The need to create a lower-end limit to what is a planet reached a near fever pitch with the discovery of a Trans-Nepturnian Object (TNO) in 2005 that is bigger than Pluto – Eris. Dr. Michael Brown of Caltech and his team led in the discovery of bright large KBOs. There was not just Eris but many of nearly the same size as Pluto. So without clause (c), one would be left with a definition for planet that could allow the count of planets in our Solar System to rise into the hundreds maybe even thousands. This would become a rather unmanageable problem; the number of planets rising year after year and never settled and with no means to make reasonable comparisons between planetary systems throughout our galaxy and even the Universe.
The book that tells the story of discovery – trans-Neptunian objects (TNO) that led to the downfall of Pluto from full planethood to that of a dwarf. The 2006 IAU decision was a pre-emptive strike to stave off a proliferation of planets in our system. It worked but “killed” Pluto. Did it have it coming? Dr. Brown also agrees that the present definition of planet is flawed and incomplete. (Photo Credits: Caltech/M.Brown)
Two more celestial body types follow that are proposed to round out the set.
moon: is a celestial body that a) orbits a (minor) planet and b) for which the barycenter of its orbit is below the surface of its parent (minor) planet.
This creates the possibility of a planet-moon system such that its barycenter is above the surface of the larger body. Pluto and Charon are the most prominent case in our Solar System. In such cases, if one body meets the criteria of a (minor)planet, then the other body can also be assessed to determine if it is also a (minor) planet and the pair as binary (minor) planets. If the primary body was a minor planet, it is possible that the barycenter could be above its surface but the secondary body does not meet all the criteria of a minor planet, specifically “differentiated interior”.
The definition of moon is compounded by the existence of, for example, asteroids with moons. For such objects, the smaller object is defined as a satellite.
Satellite: is a celestial body that a) orbits another celestial body, b) whose parent body is not a (minor) planet.
Another permissible term is moonlet which could be used to describe both very small moons such as those found in the Jovian and Saturn systems or a small body orbiting an asteroid or comet. Moonlet could replace satellite.
The discriminator between planet and moon is not mass but simply whether the celestial body orbits a (minor) planet and the barycenter resides inside the larger body. The definition of moon excludes the possibility of a planet orbiting another planet except in the special case of binary (minor) planet.
Defining a lower size limit to “Planet” is necessary to compare stellar systems and classify. A limit based on the body’s average surface pressure and temperature or the surface gravity could define a limit. While they could, they are not practical because of the extremes and diverse combinations of conditions. Strange objects would fall through the cracks.
Removing clause (c) – “has cleared the neighborhood around its orbit” – will avoid a future conflict such as a very low mass star with a plutoid-sized object or smaller, in a close orbit that has cleared its neighborhood.
Additionally, choosing to declare that Pluto becomes the “standard weight” that differentiates minor planet from planet sets a precedent. In an era in which computers measure and tally the state of our existence, setting this limit to include Pluto and return it as the ninth planet of our Solar System, is, in a small but significant way, a re-declaration of our humanity. Soon we will be challenged by artificial intelligence greater than ours; we are already have. Where will we stand our ground?
Forget about Pluto for a moment. Should Eris be our tenth planet? Like Pluto it has a prominent moon- Dysnomia. Human perception and conceptions of the Universe have shaped our view of the Solar System. The Ptolemaic system (Earth centered), Kepler’s Harmonic Spheres, even the fact that ten digits reside on our hands impact our impression of the Solar System (Photo Credits:NASA/ESA and M. Brown / Caltech)
The consequences of this proposed set of definitions, makes Ceres a minor planet and no longer an asteroid. Many trans-Neptunian objects discovered in this century become minor planets. Of the known TNOs only Pluto and Eris meets the criteria of planet.The dwarf planet Eris would become the tenth planet. Makemake, Sedna, Quaoar, Orcus, Haumea would be minor planets. By keeping Pluto a planet and defining it as the standard bearer, only one new planet must be declared. Surely, more will be found, very distant, in odd elliptical and tilted orbits. The count of planets in our solar system could rise by 10, 20 maybe 50 and perhaps this would make the definition untenable but maybe not. So be it. New Horizons will fly by a dwarf planet in July but this should mark the beginning of the end of the present set of definitions.
Three perspectives of a ten planet Solar System. No longer Earth centered, or with harmonic spheres but now with planets outside the ecliptic plane and growing. How many planets would be too many? (Credits: Wikimedia, T.Reyes)
This set of definitions defines a set of celestial bodies that consistently covers the spectrum of known bodies. There is the potential of exotic celestial objects that are spawned from cataclysmic events or from the unique conditions during the early epochs of the Universe or from remnants of old or dying stellar objects. Their discovery will likely trigger new or revised definitions but these definitions are a good working set for the time being. Ultimately, it is the decision of the IAU but the sharing of knowledge and the democratic processes that we cherish permits anyone to question and evaluate such definitions or proclamations.To all that share an interest in Pluto as or as not a planet raise your hand and be heard.
A video from 2014 by Kurz Gesagt describing the Pluto-Charon system. Is this a binary planet system or one of the “dwarf” variety?
My condolences to the friends and family of Tammy Plotner, the first regular contributing writer to Universe Today. Can’t we all relate to what drew Tammy to write about the Universe? She wrote outstanding articles for U.T.
Animation of images acquired by New Horizons on Jan. 27–Feb. 8, 2015. Hydra is in the yellow square, Nix is in the orange. (Credit: NASA/Johns Hopkins APL/Southwest Research Institute.)
Now on the final leg of its journey to distant Pluto the New Horizons spacecraft has been able to spot not only the dwarf planet and its largest moon Charon, but also two of its much smaller moons, Hydra and Nix – the latter for the very first time!
The animation above comprises seven frames made of images acquired by New Horizons from Jan. 27 to Feb. 8, 2015 while the spacecraft was closing in on 115 million miles (186 million km) from Pluto. Hydra is noted by a yellow box and Nix is in the orange. (See a version of the animation with some of the background stars and noise cleared out here.)
“Professor Tombaugh’s discovery of Pluto was far ahead its time, heralding the discovery of the Kuiper Belt and a new class of planet. The New Horizons team salutes his historic accomplishment.”
– Alan Stern, New Horizons PI, Southwest Research Institute
Launched Jan. 19, 2006, New Horizons will make its closest pass of Pluto and Charon on July 14 of this year. It is currently 32.39 AU from Earth – over 4.84 billion kilometers away.
“It’s thrilling to watch the details of the Pluto system emerge as we close the distance to the spacecraft’s July 14 encounter,” said New Horizons science team member John Spencer from the Southwest Research Institute (SwRI). “This first good view of Nix and Hydra marks another major milestone, and a perfect way to celebrate the anniversary of Pluto’s discovery.”
Along with the distance between Earth and Pluto, New Horizons is also bridging the gap of history: a portion of Mr. Tombaugh’s ashes are being carried aboard the spacecraft, as well as several historic mementos.
Annotated and unannotated versions of the LORRI images from Feb. 8 (top and bottom); the right side has had Pluto’s glare and additional background stars removed. (Credit: NASA/Johns Hopkins University Applied Physics Laboratory/Southwest Research Institute)
Each frame in the animation is a combination of five 10-second images taken with New Horizons’ Long-Range Reconnaissance Imager (LORRI) using a special mode that increases sensitivity at the expense of resolution. Celestial north is inclined 28 degrees clockwise from the “up” direction in these images.
The dark streaks are a result of overexposure on the digital camera’s sensitive detector.
Pluto and its moons, most of which were discovered while New Horizons was in development and en route. Charon was found in 1978, Nix and Hydra in 2005, Kerberos in 2011, and Styz in 2012. Credit: NASA/HST
Pluto has a total of five known moons: Charon, Hydra, Nix, Styx, and Kerberos. Pluto and Charon are within the glare of the image exposures and can’t be resolved separately, and Styx and Kerberos are too dim to be detected yet. But Hydra and Nix, each around 25–95 miles (40–150 km) in diameter, could be captured on camera.
More precise measurements of these moons’ sizes – and whether or not there may be even more satellites in the Pluto system – will be determined as New Horizons approaches its July flyby date.
Pluto and Charon, the largest of Pluto's five known moons, seen Jan. 25 and 27, 2015, through the telescopic Long-Range Reconnaissance Imager (LORRI) on NASA's New Horizons spacecraft. Credit: NASA/Johns Hopkins University Applied Physics Laboratory/Southwest Research Institute.
Here we go! New Horizons is now on approach and today – on the anniversary of Pluto discoverer Clyde Tombaugh’s birth – the spacecraft has sent back its first new images of the Pluto system. The images aren’t Earth-shattering (Pluto-shattering?) but they do represent the mission is closing in on its target, and will allow the New Horizons engineers to precisely aim the spacecraft as it continues its approach.
The photos were taken with the telescopic Long-Range Reconnaissance Imager (LORRI) on January 25 and 27, 2015.
“Pluto is finally becoming more than just a pinpoint of light,” said Hal Weaver, New Horizons project scientist. “LORRI has now resolved Pluto, and the dwarf planet will continue to grow larger and larger in the images as New Horizons spacecraft hurtles toward its targets. The new LORRI images also demonstrate that the camera’s performance is unchanged since it was launched more than nine years ago.”
A comparison of images of Pluto and its large moon Charon, taken in July 2014 and January 2015. Between takes, New Horizons had more than halved its distance to Pluto, from about 264 million miles (425 million kilometers) to 126 million miles (203 million kilometers). Credit: NASA/Johns Hopkins University Applied Physics Laboratory/Southwest Research Institute.
New Horizons was about 203 million kilometers (126 million miles) away from Pluto when it began taking images. Pluto appears as a pixelated smudge, and New Horizons is only close enough so that just Pluto and its largest moon, Charon are visible. In this current view from LORRI, Pluto is about 2 pixels and Charon is 1, compared to 1 pixel and 0.5 pixels last July. The images were magnified four times to make Pluto and Charon more visible.
NASA says that over the next few months, LORRI will take hundreds of pictures of Pluto, against a starry backdrop, to refine the team’s estimates of New Horizons’ distance to Pluto. As in these first images, the Pluto system will resemble little more than bright dots in the camera’s view until late spring. However, mission navigators can still use such images to design course-correcting engine maneuvers to direct the spacecraft for a more precise approach. The first such maneuver based on these optical navigation images, or OpNavs, is scheduled for March 10.
The image of Pluto and its moon Charon, taken by NASA’s New Horizons spacecraft, was magnified four times to make the objects more visible. Over the next several months, the apparent sizes of Pluto and Charon, as well as the separation between them, will continue to expand in the images. Image Credit: NASA/JHU APL/SwRI
Closest approach for the spacecraft will be on July 14.
These first images represent a milestone.
“These images of Pluto, clearly brighter and closer than those New Horizons took last July from twice as far away, represent our first steps at turning the pinpoint of light Clyde saw in the telescopes at Lowell Observatory 85 years ago, into a planet before the eyes of the world this summer,” said Alan Stern, New Horizons principal investigator. “This is our birthday tribute to Professor Tombaugh and the Tombaugh family, in honor of his discovery and life achievements — which truly became a harbinger of 21st century planetary astronomy.”
During its flyby, New Horizons will be characterizing the global geology and topography of Pluto and Charon, mapping their surface compositions and temperatures, examining Pluto’s atmospheric composition and structure, studying Pluto’s smaller moons, and searching for new moons and rings.
