My thoughts on today’s Pluto encounter, over at PJMedia.
[Update a few minutes later]
31 thoughts on “The Last Unknown Planet”
Of course the science is settled but I wouldn’t be surprised if one or more new planets were discovered.
Exploration shouldn’t stop because we know hardly anything about our neighbors but then again, some people think the Moon is a waste of time with nothing to be learned there.
” The window for one is in fact open right now for a year or so, but that isn’t sufficient time to plan and launch another mission, even if funding were available.”
Isn’t that a launch season? (Sorry, couldn’t resist)
They could try making a mission to map out the Kuiper Belt kinda like Dawn or something. The problem is the power source and the propulsion.
The next probe missions are going to be long endurance missions to explore the moons of the gas giants like Juno.
Oh right Juno is just for Jupiter unlike JIMO. ESA has the JUICE mission planned though.
We need a sub for Europa…
For some reason, I just don’t seem to care about the Pluto mission. Does that make me a heretic.
1. The NASA TV coverage of close approach was terrible. The attempt to appeal to young hipsters, combined with a really bad morning for the announcers, resulted in painful awfulness.
2. wodun-The definition of planet used by the IAU would basically prevent any more planets from being found, unless by some miracle one manages to clean out an area around itself in the Kuiper Belt. But if you use a more sane definition (size, mainly) there are quite possibly more Pluto-sized, or possibly even somewhat larger things way out there. We only found Sedna because it’s near perihelion. Put Pluto a few times farther out, we quite possibly wouldn’t have found it yet. It’s reasonably likely there are no more gaseous planets because they’d be seen by sensitive IR surveys. There was a fairly recent paper on that from the WISE data, excluding a warm, Saturn-like planet within 10,000 AU and a Jupiter-like planet to well more than that. But small, solid, cold bodies are still possible.
In my lifetime we have gone from the unmanned Vikings to today. I remember having a NatGeo book on the universe that showed fuzzy colored spheres for Uranus and Neptune, a question mark for Pluto and even Saturn and Jupiter had no more than Pioneer level details available. In thirty 7 years, we have learned so much about our star system and by extension, the universe due to these probe missions and what is truly amazing is that image is just a teaser for things to come.
Does anyone else find it ironic that NASA JPL is the most productive and innovative part of NASA, and that it does more with less than any other part of the agency. For example:
Viking
Voyager
Galileo
Cassini
Pathfinder & Sojourner
Pheonix
Spirit & Opportunity (90 day warrentee? HA!)
Curiosity
MER
Kepler
Spitzer
and now New Horizons (Assuming it does not slam into Pluto’s 6th, undiscovered moon)
If only the rest of NASA opperated this way. Of course, it is not entirely their fault. Congress is involved, and that is the surest way to screw things up…
But either which way, this is a remarkable feat and even my eldest son is suitable impressed, asking if he might be able to go there someday…
new horizons is John Hopkins APL … not JPL.
Still, a good point.
Whoops! My bad. I guess I am too used to thinking that JPL is responsible for the deep space probe missions.
It’s not surprising; I assumed it was JPL myself.
“If only the rest of NASA opperated this way.”
Indeed. That was one of the recommendations of the Augustine report – turn all NASA centers into Federally Funded Research and Development Centers. Among NASA centers, JPL is the only FFRDC.
Superb article.
Interesting to contrast the yield from a mission such as this, which cost about 700 million all told, with SLS/Orion, which this year alone is burning through that much money every 76 days.
I find it very interesting that the Pluto system, which such an eccentric orbit, has that many moons.
I would think Pluto’s orbit is why it has so many [captured?] moons.
OT but has anybody noticed that SpaceX has not yet provided an update on the failure. It is my understanding that they were to make an announcement late last week.
Musk may be dealing with a serious mental break? His behavior is atypical for him. Hopefully not or if so is only temporary.
Or they may be having trouble narrowing down the cause, and don’t want to say it’s one thing when it later turns out to be another. Patience.
One niggle: “…we’ve learned this week from the spacecraft is that it’s the largest known one, edging out its KBO “twin” Eris, which had previously been thought to be the ninth-largest body in the solar system.”
Actually, Pluto would only be promoted to the 16th largest (by volume, at least – Eris appears to have greater mass) body in the Solar System (excluding the Sun), since there are seven Moons that are larger – the Moon, Jupiter’s four Galilean moons, Titan, and Triton. And moons should count. This is assuming there isn’t any other KBO’s out there we haven’t located that are bigger than Pluto, of course (which is a distinct possibility).
Still, that’s no reason to say it isn’t a planet, contra the IAU. Indeed, since Charon does not orbit Pluto but rather both orbit a common point, it may be better to say that Pluto-Charon is a binary planetary system. And the reality is that the Solar System likely contains over a hundred – perhaps several hundred – planets, almost all of them in the Kuiper Belt and Scattered Disk.
I think you are absolutely correct on the number of planets. The IAU definition is way to complicated. Using the KISS principle, a planet should be defined as any body orbiting a star (in this case, our Sun) that has sufficient gravity to force a round shape. By that definition, no moons are included, but Ceres, Eris, possibly Sedna, and the Pluto-Charon Binary would all be classified as planets. Size and clearing the orbit is a poor way of defining a planet. Heck, would Mercury qualify using that standard? Or did the Sun and Venus do most of the work clearing it’s orbit?
Also add Makemake to the mix. Haumea is also a possibility, although that could be debated because of its potentially egg-like shape…
According to Mike Brown’s site – updated regularly – there are as many as 376 KBO’s that we have already discovered that are likely dwarf planets – ten of them with near certainty, including Pluto, Eris, Makemake, Haumea, Quaoar, Sedna and Orcus.
And that’s just the ones we know about.Who knows what else is out there in the Kuiper Belt and the Scattered Disk? Odds are we’ve only discovered a tithe of it.
Then the earth isn’t a planet because it is eggshaped (oblate spheroid.) Actually, they probably all are.
Any [outside] surface people call home will probably be referred to as a planet.
Greg, just because it is orbiting a planet doesn’t mean a moon isn’t also orbiting a star.
The treatment of moons is almost as arbitrary as the rest of the IAU planet definition. You look at a moon like Ganymede which is larger (certainly by volume) than not only Pluto but also Mercury, even has its own magnetosphere – yet it’s not considered a planet, because it happens to be orbiting Jupiter. What it really is is a satellite planet.
I can remember when Saturn had as many moons as our solar system had planets.
Geez, this planet controversy is people changing stuff for change sake without considering any of the history.
Since people from the pre-electric illumination days had a reason to be out at night and look up at the sky, shepherd’s, I guess, people have noticed there are the stars that pretty much stay in the same arrangement relative to each other, and there is the Moon and 5 planets — celestial wanderers — that move around.
These planets, in our culture, are named after mythical beings. Many of us have seen 4 of them — Venus, the dazzling “Morning Star” or “Evening Star” named after the goddess of love, Jupiter, the almost-as-bright ruler of the nighttime sky, Saturn, the yellower and dimmer aged ancestor of the gods, and Mars, the blood-red planet that we hardly notice except every 2 years when it becomes a prominent harbinger of war. Mercury gets lost in the glare of evening or morning twilight, and us moderns don’t see it unless we really go looking for it.
The Copernicus-Kepler-Galileo revolution establishes that Earth too is a planet, bringing the number up to 6. Galileo’s telescope observations establish Jupiter to have its own “planetary system” of moons. Herschel’s telescopic search for comets turns up a 7th planet — Uranus — a largish body but distant enough not to be noticed without a telescope.
Newton’s Theory of Gravitation leads to the purely mathematical discovery of yet another planet — Neptune — whose telescopic confirmation brings the number to 8.
A seemingly mathematical relationship regarding the spacing of the planets leads a bunch of German dudes to search for a missing planet between Mars and Jupiter. This math theorem is probably numerological hokum, but the gravitational perturbations from massive Jupiter probably account for a full-fledged planet not forming in that gap. A Sicilian priest beats the Germans to the punch in discovering Ceres. Other such asteroids are found, not counted as planets, but asteroids get found like crazy with the development of telescopic photography.
Newton’s Theory is used to predict a Planet X beyond Neptune, but this proves to be mathematical bunk, probably by not using the right error bars on physical measurements (sound familiar?). The technique of “blink comparison” of astrophotographs used to find new asteroids is tirelessly applied by Iowa-farm-boy-turned-astronomical-research-assistant Clyde Tombaugh, who discovers Pluto “in the right place”, but leaving questions if it is massive enough to account for the supposed gravitational anomoly that is today regarded as the artifact of wrong values for the other planets (the science (for a long while had been) settled).
A half century later, Caltech scientists Liu and Jewitt use CCD electronic imaging to discover what had been (legitimately) inferred from comet orbits — the existence of a second “asteroid belt” beyond Neptune. This and later surveys were arguably inspired by the fear of us getting clunked by an errant asteroid. It turns out that Pluto, discovered at the limits of pre-electronic-sensor photography, if not the largest, is historically first among peer trans-Neptune bodies.
Now, we learn that not only is Pluto a not-a-planet, it is indeed the near-central object to a full not-a-planetary system.
Planet-scmanet, Pluto plays an important role in the discovery and exploration of our solar system. Maybe it should be demoted to the same rank as Ceres, or maybe Ceres need to be elevated in importance. But Pluto for all of its mystery of discovery, long standing as the last-discovered major Solar System body, and remoteness, for it being the Mount Everest of visual astronomy to this day, Pluto merits a special place in the human imagination.
Greg – Arguably, our own Moon should be considered a planet in its own right. This depends somewhat on how one defines “orbiting a planet” – one definition of that might be that some of its orbit is convex towards the Sun or in other words that at some times it is travelling away from the Sun.
This is not true of our own Moon. Plot its orbit in true scale and it turns out that the path traced out by the Moon is always concave towards the Sun. And therefore, since by some definitions it isn’t orbiting Earth, it deserves to be called a planet.
Since even the earth-moon barycenter is within the earth, how far from the more massive body’s center does it need to be to qualify as a binary planet?
…bearing in mind that at some point the Moon will be far enough from the earth to extract the barycenter — but at what point would the Moon’s orbit of the sun become sufficiently loosened from the Earth to become not part of a binary system but a loose-cannon dwarf planet?
We could just call them what Sagan liked to call them, “worlds”.
Only if we can get the accent right.
I agree, Chris. Any body large enough for gravity to pull it into a spherical shape (if the highest point on the surface and the lowest point on the surface differ less than 1% of the radius of the body) but not large enough to start sustained fusion reactions in the core, it’s a world. So Pluto and Charon would be worlds; Hydra, Nix, Kerberos, and Styx would not.
The practical difference is the difference between landing and docking. Grabbing a boulder off an asteroid like Altius is planning is more like docking with the asteroid than it is like landing on the moon.
Of course the science is settled but I wouldn’t be surprised if one or more new planets were discovered.
Exploration shouldn’t stop because we know hardly anything about our neighbors but then again, some people think the Moon is a waste of time with nothing to be learned there.
” The window for one is in fact open right now for a year or so, but that isn’t sufficient time to plan and launch another mission, even if funding were available.”
Isn’t that a launch season? (Sorry, couldn’t resist)
They could try making a mission to map out the Kuiper Belt kinda like Dawn or something. The problem is the power source and the propulsion.
The next probe missions are going to be long endurance missions to explore the moons of the gas giants like Juno.
Oh right Juno is just for Jupiter unlike JIMO. ESA has the JUICE mission planned though.
We need a sub for Europa…
For some reason, I just don’t seem to care about the Pluto mission. Does that make me a heretic.
1. The NASA TV coverage of close approach was terrible. The attempt to appeal to young hipsters, combined with a really bad morning for the announcers, resulted in painful awfulness.
2. wodun-The definition of planet used by the IAU would basically prevent any more planets from being found, unless by some miracle one manages to clean out an area around itself in the Kuiper Belt. But if you use a more sane definition (size, mainly) there are quite possibly more Pluto-sized, or possibly even somewhat larger things way out there. We only found Sedna because it’s near perihelion. Put Pluto a few times farther out, we quite possibly wouldn’t have found it yet. It’s reasonably likely there are no more gaseous planets because they’d be seen by sensitive IR surveys. There was a fairly recent paper on that from the WISE data, excluding a warm, Saturn-like planet within 10,000 AU and a Jupiter-like planet to well more than that. But small, solid, cold bodies are still possible.
In my lifetime we have gone from the unmanned Vikings to today. I remember having a NatGeo book on the universe that showed fuzzy colored spheres for Uranus and Neptune, a question mark for Pluto and even Saturn and Jupiter had no more than Pioneer level details available. In thirty 7 years, we have learned so much about our star system and by extension, the universe due to these probe missions and what is truly amazing is that image is just a teaser for things to come.
Does anyone else find it ironic that
NASAJPL is the most productive and innovative part of NASA, and that it does more with less than any other part of the agency. For example:Viking
Voyager
Galileo
Cassini
Pathfinder & Sojourner
Pheonix
Spirit & Opportunity (90 day warrentee? HA!)
Curiosity
MER
Kepler
Spitzer
and now New Horizons (Assuming it does not slam into Pluto’s 6th, undiscovered moon)
If only the rest of NASA opperated this way. Of course, it is not entirely their fault. Congress is involved, and that is the surest way to screw things up…
But either which way, this is a remarkable feat and even my eldest son is suitable impressed, asking if he might be able to go there someday…
new horizons is John Hopkins APL … not JPL.
Still, a good point.
Whoops! My bad. I guess I am too used to thinking that JPL is responsible for the deep space probe missions.
It’s not surprising; I assumed it was JPL myself.
“If only the rest of NASA opperated this way.”
Indeed. That was one of the recommendations of the Augustine report – turn all NASA centers into Federally Funded Research and Development Centers. Among NASA centers, JPL is the only FFRDC.
That’s not a heart. It’s Pluto! (the dog)
http://www.theverge.com/2015/7/14/8962367/pluto-disney-whoa-dude-what
Superb article.
Interesting to contrast the yield from a mission such as this, which cost about 700 million all told, with SLS/Orion, which this year alone is burning through that much money every 76 days.
I find it very interesting that the Pluto system, which such an eccentric orbit, has that many moons.
I would think Pluto’s orbit is why it has so many [captured?] moons.
OT but has anybody noticed that SpaceX has not yet provided an update on the failure. It is my understanding that they were to make an announcement late last week.
Musk may be dealing with a serious mental break? His behavior is atypical for him. Hopefully not or if so is only temporary.
Or they may be having trouble narrowing down the cause, and don’t want to say it’s one thing when it later turns out to be another. Patience.
One niggle: “…we’ve learned this week from the spacecraft is that it’s the largest known one, edging out its KBO “twin” Eris, which had previously been thought to be the ninth-largest body in the solar system.”
Actually, Pluto would only be promoted to the 16th largest (by volume, at least – Eris appears to have greater mass) body in the Solar System (excluding the Sun), since there are seven Moons that are larger – the Moon, Jupiter’s four Galilean moons, Titan, and Triton. And moons should count. This is assuming there isn’t any other KBO’s out there we haven’t located that are bigger than Pluto, of course (which is a distinct possibility).
Still, that’s no reason to say it isn’t a planet, contra the IAU. Indeed, since Charon does not orbit Pluto but rather both orbit a common point, it may be better to say that Pluto-Charon is a binary planetary system. And the reality is that the Solar System likely contains over a hundred – perhaps several hundred – planets, almost all of them in the Kuiper Belt and Scattered Disk.
I think you are absolutely correct on the number of planets. The IAU definition is way to complicated. Using the KISS principle, a planet should be defined as any body orbiting a star (in this case, our Sun) that has sufficient gravity to force a round shape. By that definition, no moons are included, but Ceres, Eris, possibly Sedna, and the Pluto-Charon Binary would all be classified as planets. Size and clearing the orbit is a poor way of defining a planet. Heck, would Mercury qualify using that standard? Or did the Sun and Venus do most of the work clearing it’s orbit?
Also add Makemake to the mix. Haumea is also a possibility, although that could be debated because of its potentially egg-like shape…
According to Mike Brown’s site – updated regularly – there are as many as 376 KBO’s that we have already discovered that are likely dwarf planets – ten of them with near certainty, including Pluto, Eris, Makemake, Haumea, Quaoar, Sedna and Orcus.
http://web.gps.caltech.edu/~mbrown/dps.html
And that’s just the ones we know about.Who knows what else is out there in the Kuiper Belt and the Scattered Disk? Odds are we’ve only discovered a tithe of it.
Then the earth isn’t a planet because it is eggshaped (oblate spheroid.) Actually, they probably all are.
Any [outside] surface people call home will probably be referred to as a planet.
Greg, just because it is orbiting a planet doesn’t mean a moon isn’t also orbiting a star.
The treatment of moons is almost as arbitrary as the rest of the IAU planet definition. You look at a moon like Ganymede which is larger (certainly by volume) than not only Pluto but also Mercury, even has its own magnetosphere – yet it’s not considered a planet, because it happens to be orbiting Jupiter. What it really is is a satellite planet.
I can remember when Saturn had as many moons as our solar system had planets.
Geez, this planet controversy is people changing stuff for change sake without considering any of the history.
Since people from the pre-electric illumination days had a reason to be out at night and look up at the sky, shepherd’s, I guess, people have noticed there are the stars that pretty much stay in the same arrangement relative to each other, and there is the Moon and 5 planets — celestial wanderers — that move around.
These planets, in our culture, are named after mythical beings. Many of us have seen 4 of them — Venus, the dazzling “Morning Star” or “Evening Star” named after the goddess of love, Jupiter, the almost-as-bright ruler of the nighttime sky, Saturn, the yellower and dimmer aged ancestor of the gods, and Mars, the blood-red planet that we hardly notice except every 2 years when it becomes a prominent harbinger of war. Mercury gets lost in the glare of evening or morning twilight, and us moderns don’t see it unless we really go looking for it.
The Copernicus-Kepler-Galileo revolution establishes that Earth too is a planet, bringing the number up to 6. Galileo’s telescope observations establish Jupiter to have its own “planetary system” of moons. Herschel’s telescopic search for comets turns up a 7th planet — Uranus — a largish body but distant enough not to be noticed without a telescope.
Newton’s Theory of Gravitation leads to the purely mathematical discovery of yet another planet — Neptune — whose telescopic confirmation brings the number to 8.
A seemingly mathematical relationship regarding the spacing of the planets leads a bunch of German dudes to search for a missing planet between Mars and Jupiter. This math theorem is probably numerological hokum, but the gravitational perturbations from massive Jupiter probably account for a full-fledged planet not forming in that gap. A Sicilian priest beats the Germans to the punch in discovering Ceres. Other such asteroids are found, not counted as planets, but asteroids get found like crazy with the development of telescopic photography.
Newton’s Theory is used to predict a Planet X beyond Neptune, but this proves to be mathematical bunk, probably by not using the right error bars on physical measurements (sound familiar?). The technique of “blink comparison” of astrophotographs used to find new asteroids is tirelessly applied by Iowa-farm-boy-turned-astronomical-research-assistant Clyde Tombaugh, who discovers Pluto “in the right place”, but leaving questions if it is massive enough to account for the supposed gravitational anomoly that is today regarded as the artifact of wrong values for the other planets (the science (for a long while had been) settled).
A half century later, Caltech scientists Liu and Jewitt use CCD electronic imaging to discover what had been (legitimately) inferred from comet orbits — the existence of a second “asteroid belt” beyond Neptune. This and later surveys were arguably inspired by the fear of us getting clunked by an errant asteroid. It turns out that Pluto, discovered at the limits of pre-electronic-sensor photography, if not the largest, is historically first among peer trans-Neptune bodies.
Now, we learn that not only is Pluto a not-a-planet, it is indeed the near-central object to a full not-a-planetary system.
Planet-scmanet, Pluto plays an important role in the discovery and exploration of our solar system. Maybe it should be demoted to the same rank as Ceres, or maybe Ceres need to be elevated in importance. But Pluto for all of its mystery of discovery, long standing as the last-discovered major Solar System body, and remoteness, for it being the Mount Everest of visual astronomy to this day, Pluto merits a special place in the human imagination.
Greg – Arguably, our own Moon should be considered a planet in its own right. This depends somewhat on how one defines “orbiting a planet” – one definition of that might be that some of its orbit is convex towards the Sun or in other words that at some times it is travelling away from the Sun.
This is not true of our own Moon. Plot its orbit in true scale and it turns out that the path traced out by the Moon is always concave towards the Sun. And therefore, since by some definitions it isn’t orbiting Earth, it deserves to be called a planet.
Since even the earth-moon barycenter is within the earth, how far from the more massive body’s center does it need to be to qualify as a binary planet?
…bearing in mind that at some point the Moon will be far enough from the earth to extract the barycenter — but at what point would the Moon’s orbit of the sun become sufficiently loosened from the Earth to become not part of a binary system but a loose-cannon dwarf planet?
We could just call them what Sagan liked to call them, “worlds”.
Only if we can get the accent right.
I agree, Chris. Any body large enough for gravity to pull it into a spherical shape (if the highest point on the surface and the lowest point on the surface differ less than 1% of the radius of the body) but not large enough to start sustained fusion reactions in the core, it’s a world. So Pluto and Charon would be worlds; Hydra, Nix, Kerberos, and Styx would not.
The practical difference is the difference between landing and docking. Grabbing a boulder off an asteroid like Altius is planning is more like docking with the asteroid than it is like landing on the moon.