Halfway to Pluto!

By Phil Plait | December 29, 2009 10:33 am

eso_pluto_surface_300Today, December 29, 2009, the New Horizons Pluto probe crosses an arbitrary but psychologically important line: it is now closer to Pluto than it is to Earth.

If there were people on board the small interplanetary probe, no doubt they’d be popping champagne. I’m sure that back on Earth, the team behind NH are pretty happy. This probe has a checkered history, having been planned, canceled, re-planned, delayed, on and on. It’s amazing it got to launch at all. But on January 19, 2006 the small, half-ton probe was sent on its way, and on July 14, 2015 it’ll sail past Pluto and its collection of moons, snapping pictures and taking data.

Today marks the official halfway point, where New Horizons has half its path already behind it. Here’s a plot of its distance to Earth (in blue) and Pluto (red) care of the New Horizons site:

newhorizons_distance

Distance in the graph is measured in Astronomical Units (a yardstick used by astronomers for convenience; it’s the distance of the Earth to the Sun, about 150 million km (93 million miles)). The distance to Earth is wiggly because the Earth goes around the Sun as New Horizons moves out, and the distance to Pluto decreases steadily as the spacecraft catches up on its journey. Where the two lines cross is where the distances are equal, and that’s now, today!

You may be wondering about the timing: New Horizons is halfway in distance to Pluto, but the mission timeline halfway point isn’t until October 16, 2010 (if I’ve done the math correctly). The probe was launched at high speed, slowed down due to the Earth’s and Sun’s gravity, picked up a kick from Jupiter in early 2007, and has been slowing ever since. Since it was moving faster before, it reached the distance halfway point before the schedule halfway point.

New Horizons is now 16.37 AU – 2.449 billion km, or 1.522 billion miles — from home. But maybe now, home is no longer Earth. Once it crossed that line today, home became deep space. Even Pluto and its moons Charon, Nix, and Hydra are only milestones for it. It won’t be stopping when it gets there; New Horizons will sail on by, continuing into deep space. It’ll become one of several other spacecraft we’ve sent out of the solar system itself, set to wander interstellar space forever.

That is, unless one day we catch up to them ourselves. I imagine in a few hundred years they’d make fine museum pieces. Or maybe, if poetry still exists in humans all those far-flung centuries from now, we’ll let those probes continue on. I rather like that idea better.

You can follow the New Horizons probe on Twitter, which is how I found out about this milestone today.

Art credit: ESO/L. Calçada

CATEGORIZED UNDER: Astronomy, Space
MORE ABOUT: New Horizons, Pluto

Comments (56)

  1. Plutonium being from Pluto

    Awesome news! Visitors coming soon! (Well Plutonean soon anyhow.) :-D

    Welcome NewHorizons, welcome! I’ll get the Plutonium kettle on for your traditional Plutonean cuppa – hope you like your liquid nitrogen tea just above absolute zero. ;-)

    Oh & the skiiing & ice skating is great both here and on Charon at this time of year – although you do have to dodge the (Triton-like but bigger & better) cyrovolcanic geysers and time your run so one doesn’t erupt under you. If that happens you sure can get lots of air & do some spectacular gymnastics given our gravity but it does tend to ruin your time and just take too loong. Refreshing though. ;-)

    Plus we get our snowfall soon – it always helps to come while there’s still an atmosphere & before we have to sink back down to our homes at the bottom of the sub-icy crust ocean near Pluto’s core – mantle boundary layer!

    Still whatever time you arrive, I’m sure you’ll enjoy the rings and seeing our three moons and I bet you reclassify my home planet as, well, a proper (if cosily small) planet after seeing it up close on this friendly trip. 8)

    Seriously, that’s great news & a superluminous note to end the year on.
    Thanks for this BA. :-)

  2. Mount

    I’m sure those craft will last longer in deep space than they would in a museum. Let’s just hope they don’t come back to haunt us like V’ger did!

  3. ND

    Gah! 2015 is not close enough!

    We need vasimr propulsion now! Cause I’m impatient!

  4. Joe Meils

    If we’d launched it with an Orion nuke pulse drive, we would have been there two years ago… LOL

    Congrats, Phil. You made it through the update without accidentally referring to Pluto as a planet.

  5. Pluto is a PLANET! Or at least in spirit it is, despite whatever revisionist nonsense spouted by the Astronomical Union says.

    I’m sure demoting Pluto sounded like a good idea at the time, but may I remind you that so did the Star Wars Holiday Special? You go watch that, with Bea Arthur celebrating Life Day and Princess Leia singing Life Day songs, and THEN you tell me Pluto isn’t a planet!

  6. KC

    Yes really -let’s put the IAU on the sh*t list with other revisionists like that bastard Copernicus!

  7. rob

    v’ger is coming, and it’s gonna bring n’rizon with it.

  8. OtherRob

    I’m not sure I’d call halfway an arbitrary line. Sure, there’s no actual line in space marking the point, but it is an actual milestone in the journey and one worth celebrating. :-)

  9. Ed

    Hi Phil:

    Why doesn’t NASA use the cameras on this and previous spacecraft such as the Voyager duo to do stellar parallax measurements? They’ve got all sorts of time. We know their positions with respect to earth very accurately. And the cameras that they use are high quality (if not perhaps very large aperture). The Voyager and Pioneer spacecraft would now have baselines to earth in the hundreds of AU.

  10. !AstralProjectile

    PBFP: Liquid nitrogen just above 0 K? You are just trying to lull us into a false sense of security.

  11. Plutonium being from Pluto

    Well, you gotta make sure your booze is nice & cold don’t you? ;-)

    (Yes, even the tea is alcoholic on Pluto – and there’s plenty of ice to spare for drinks too!)

    NewHorizons is staying for tea isn’t it? ;-)

  12. NewHorizons

    ^ I am now Plutonium being from Pluto, I am now! ;-)

  13. Matthew Ota

    By the time New Horzons gets to Pluto, perhaps it’s status will have been restored to full planethood…or at least it will get some new respect from planetary scientists.

  14. Michael Swanson

    It doesn’t matter if the IAU wanted to reclassify Pluto as a dirt clod, it’s still magnificent. I don’t see why it should matter so much that it was reclassified. After all, the Moon is just a lowly moon, but it’s still valued, beloved and much studied.

    C’mon 2015!

  15. Ed @11: Almost a great idea. To do really good parallax measurements you actually need to design the cameras with that task in mind. Large aperture (actually high optical speed and low noise), low (and well-characterized) optical distortion, and, um, well I guess those would be the driving requirements. What you really want is something like the Hipparcos mission. Even though it only had a baseline of 2 A.U. (because it orbited the Earth), it measured 100,000 stars to .001 arcseconds. Not bad. The upcoming Gaia mission will do even better.

    It’s possible you could measure a small number of stars more accurately than that using the much larger baseline of the existing deep space probes, but you’d have to look at the numbers for their optical, positioning, and attitude systems. When you’re making measurements that precise, the killer is always (ALWAYS) systematic error. Which means you have to calibrate the system on the ground with those measurements in mind. Since that wasn’t done for the planetary missions, they probably wouldn’t give you any better data than already exists in the Hipparcos catalog.

  16. 1. Plutonium Says: “hope you like your liquid nitrogen tea just above absolute zero.”

    Wouldn’t that make it nitrogen ice by something like 100K?

    5. Mark – I think it’s time to adjust the meds again.

    – Jack

  17. Chanelle

    @5 (Mark)

    If I promise to always call Pluto a planet, can I pass on the Christmas Special? Really, just the threat is enough to make me change my ways forever.

  18. MAC

    The sad thing is that New Horizons will get to Pluto before NASA has a manned space program again, at least at the pace that’s currently planned. Sure was nice to be the greatest spacefaring nation on Earth for a while there.

  19. 20. MAC Says: “Sure was nice to be the greatest spacefaring nation on Earth for a while there.”

    This is sad but true. I’ve heard the US described as “the Portugal of space exploration.” During the 14th and 15th Centuries, the Portuguese had no equals in exploring the planet. They had invented the Portuguese Quadrant that let sailors venture out of sight of land and know when it was time to turn east to hit the port they wanted. They were the first Europeans to circumnavigate Africa. Even the ruling family was involved (Prince Henry the Navigator). Basically, they blazed the trail for others to follow.

    Sadly, they yielded to “problems at home” and handed over the leadership in global exploration to Spain and England (with some Italians in there).

    No one outside of historians even remembers their contributions today.

    – Jack

  20. Popping champagne on a spacecraft, at present, would be a bad idea. That’s the real stumbling block for manned spaceflight ;-)

    Congrats New Horizons team!

  21. Torbjörn Larsson, OM

    That is, unless one day we catch up to them ourselves. I imagine in a few hundred years they’d make fine museum pieces.

    They would, but how do you propose to dig them up out of the desert of space? I’ve been told by astronomers that it’s a frikken big universe out there.

    [Even if you knew the initial trajectory, wouldn’t the search volume along it embiggen like (travel time)^3?]

  22. Gary Ansorge

    I just hope the Klingons don’t stumble across it. Wouldn’t want those guys dropping in on us before we’re ready(with phase cannons, anti-matter bombs and force shields).

    I notice SETI is actually getting federal funding again. About damn time.

    Pluto sounds like a real party place. Great for us DeadHeads,,,

    GAry 7

  23. JB of Brisbane

    From Mork & Mindy, circa late seventies:

    Mork: I’ve been to all the planets – Mars, Venus, Jupiter…

    Exidor: Even Pluto?

    Mork: Oh, don’t go to Pluto, it’s a Mickey Mouse planet!

  24. Blizno

    ~13 A. U. is only half way? This is one long journey.

    My brother-in-law worked on the design of the rocket that launched the probe. Proud? Yes, vicariously, I am.

    I have decided to avoid dying from a car crunching my bicycling self or a gamma-ray burster toasting my planet before I can see Pluto up close. I expect Pluto to look like Mercury with less cratering and with a dusting of frozen atmosphere, but see it I must.

  25. More on the way there than more towards the point of origin hardly seems arbitrary.

  26. Pluto IS a planet. The real paradigm shift some are having trouble adjusting to is a solar system with potentially hundreds of planets instead of eight or nine. Planets are not rare or special; they are everywhere. This is an extension of the Copernican principle. It’s the IAU who are being revisionists by trying to artificially narrow the definition of planet because they cannot deal with the idea of a solar system with numerous planets.

    Too bad New Horizons isn’t an orbiter. That would have given us so much more information. Still, I personally am looking forward to July 14, 2015 (four days after my birthday) like a kid looking forward to Christmas.

    And yes, Pluto is definitely a party planet. You should see the jacuzzis and pools some of us Plutonians have. :)

  27. Gamercow

    Pluto is a planet in the same way that a dwarf star is a star. Its just further classification. Therefore, there are 13(8 + Pluto, Haumea, Makemake, Ceres, and Eris?) named known planets in our solar system.

  28. Shawn Smith

    Pluto is a satelite of Sol. It is the longest known of the Plutinos / dwarf planets. We don’t call, and almost never have called, any of the asteroid belt objects planets (I think Ceres was considered a planet for a short time). We haven’t called any comets planets. We haven’t called any of the asteroids at Jupiter’s Lagrange points planets. Laurel, it sounds like you are the one who is being a revisionist here, because you apparently want to call all those other things planets. The IAU simply chose some criteria for a definition of “planet” that seemed reasonable, mainly because it didn’t have one before, and it turned out Pluto didn’t meet the criteria. Eris, Makemake, Haumea, and Quaoar don’t meet the criteria either.

    Interesting milestone for New Horizons. I also look forward to any information the New Horizons probe can provide us.

  29. 33. Shawn Smith Says: “I think Ceres was considered a planet for a short time”

    I believe both Ceres and Eros are now classified as “dwarf planets.” The rationale is that they orbit the sun directly and are large enough to be spherical.

    – Jack

  30. Chris A.

    @Shawn Smith (33):

    “…Ceres was considered a planet for a short time.”

    Only if you consider two-thirds of a century to be a short time:

    Ceres discovered: 1801
    Ceres listed as one of 11 planets (also including Vesta, Juno, and Pallas) in “First Steps to Astronomy and Geography”: 1828
    Asteroid numbering convention introduced (by Encke), excluding Ceres, Pallas, Vesta, and Juno: 1851
    Ceres, Pallas, Juno, and Vesta given asteroid numbers 1-4: 1855
    Last listing in the same table with the planets (along with Pallas, Juno, and Vesta) by the Berlin Astronomical Yearbook: 1867

    Pluto had a slightly longer run as a planet. Big deal. Our knowledge changes. Accept it, move on.

  31. Alaskana

    Is this craft going to orbit Pluto for any amount of time, or is it just going to go cruising by, grabbing as much data as it can while it passes?

  32. 36. Alaskana Says: “Is this craft going to orbit Pluto for any amount of time, or is it just going to go cruising by, grabbing as much data as it can while it passes?”

    This is a flyby mission. One quick glance, then it’s out of the solar system forever.

    Well, not all that quick. I’m sure they will have the observation schedule highly optimized by the time it gets there and will spend months doing “close up” observations both before and after closest approach.

    The reason it isn’t an orbiter is time. It’s on a coasting trajectory (i.e. no power, like with an ion engine) so we gave it as big a push as possible and picked up more from Jupiter, and even at that it’s taking over 9 years to get there. To be an orbiter it would have to approach Pluto at roughly its orbital velocity, which is a lot slower than it’s going to be travelling. Halley’s comet travels roughly this orbit (from just inside Earth’s orbit to just outside Neptune’s) and it takes 38 years to make the journey!

    – Jack

  33. StevoR

    @ 15. Matthew Ota Says:

    By the time New Horzons gets to Pluto, perhaps it’s status will have been restored to full planethood…or at least it will get some new respect from planetary scientists.

    Me too – agreed 100%. :-)

    @ 31. Laurel Kornfeld Says:

    Pluto IS a planet. The real paradigm shift some are having trouble adjusting to is a solar system with potentially hundreds of planets instead of eight or nine. Planets are not rare or special; they are everywhere. This is an extension of the Copernican principle. It’s the IAU who are being revisionists by trying to artificially narrow the definition of planet because they cannot deal with the idea of a solar system with numerous planets.

    Absolutely spot on & well said. :-D

    My definition for a planet – a reasonable definition unlike the ridiculous IAU one – is that an object is a planet if it is :

    a) Never self luminous by nuclear fusion thus not a star or brown dwarf,

    b) Not directly orbiting another planet thus not a moon

    &

    c) Large enough to be round or, if rapidly spinning oblate spheroidal, through its own gravity thus not a comet or asteroid.

    Planets can then be divided into various classes & sub-classes depending on their composition and orbital positions such as Gas Giant, Hot Jupiter, Eccentric Orbiter, Hot Neptune, Ice Giant (Neptune-like), Gas Dwarf, Super-Earth, Earth-like or Terrestrial planets & Ice dwarfs.

    Our solar systems has three main types of planets each occupying their own zone around our Sun – the rocky, the gassy & the icy! :-)

    By my reckoning & classification system (which I make no claims to have invented or anything like that, its really pretty much common sense.) we have four rocky or Earth-like planets, four gas giant or Jovian planets* and many ice dwarf planets of which Pluto, Eris and Makemake are the largest currently known.

    Now doesn’t that make more sense – isn’t much better and clearer than the IAU’s mess?

    —–

    * I like this basic division into the rocky, the gassy & the icy but if you wish to get more technical you can if desired separate the smaller Ice Giants Neptune & Ouranos from the “proper” Gas Giants Jupiter & Saturn. Ceres could be considered an asteroidal planet or an ice dwarf while other candidates for asteroidal planet class include Pallas & Vesta. From an observational viewpoint it can also be useful to use the “Inferior planets /superior planets” division with Mercury & Venus being inferior ie. closer to our Sun & also near it and setting or rising close to twilight. Plus folks can also call the planets visible to the ancient pre-telescopic times “classical” & the later discovered Ouranos, Neptune, Pluto, Ceres, Haumea etc .. post-Telescopic planets and so forth.

    Planets – the more, the merrier! ;-)

  34. Plutonium being from Pluto

    @ 34. Jack Hagerty Says:

    I believe both Ceres and Eros are now classified as “dwarf planets.” The rationale is that they orbit the sun directly and are large enough to be spherical.

    Yes for Ceres there but not for Eros which is a saddle -shaped elongated Near-Earth Asteroid – the one the NEAR-Shoemaker probe explored and landed on some years ago! I take it you mean Eris? ;-)

    Or did you mean another asteroid? There are a number of possible asteroid belt dwarf planets or candidates for that status – Ceres, Pallas, Vesta and maybe one or two others. :-)

    @ 35. Chris A. Says:

    @Shawn Smith (33):

    “…Ceres was considered a planet for a short time.”

    Only if you consider two-thirds of a century to be a short time: Pluto had a slightly longer run as a planet. Big deal. Our knowledge changes. Accept it, move on.

    The IAU definition deliberately designed by a tiny anti-Pluto minority of the Prague meeting was NOT a change in knowledge but a political decision that makes little if any scientific sense.

    The third criteria for the IAU definition – to do with planets clearing their orbits – is problematic in being vague, hard to define in itself and is illogical & unscientific.

    It fails among other things the reductio ad absurdum test of logic because it means that if Earth or even Jupiter was orbiting in the Edgeworth-Kuiper belt they would not be planets either which everyone would agree is absurd.

    (In the fact, the planets of Fomalhaut b and those around HR 8799 which were photographed the other year – among others – do NOT count as planets under the IAU definition because of this criteria yet are many times more massive than Jupiter!)

    The sole reason that such a, let’s face it, totally unscientific and downright stupid criteria was added to the IAU definition of planet was to exclude Pluto from planethood. This decision was made at the very last minute by just a handful of astronomers with the advocates of Pluto’s planethood – notably Alan Stern – excluded from the final decision and vote.

    It was very much NOT a case of knowledge changing but rather a mistake made because of a tiny minority of biased people who, for dubious and illogical reasons that are known only to them had a nasty prejudice against Pluto.

    Such mistakes need changing and correcting – the sooner the better for *all* astronomers.

    Thngs will move on indeed – because in the future hopefully even the near future we will look back at the aberration of Pluto’s temporary “non-official planethood” and wonder what the blazes those fools were thinking & how they could ever have made such a blatantly wrong, silly decision. ;-)

  35. StevoR

    For those that haven’t already seen them, here are my :

    TWELVE REASONS WHY PLUTO *IS* A PLANET :

    1. The orbital clearing condition which is the reason for eliminating Pluto is fatally flawed because it is too hard to define. Strictly speaking this criteria eliminates every object in our solar system from proper planethood as all planets have objects – comets and asteroids crossing their orbits!

    2. A reductio ad absurdum approach reveals that this criterion fails because it leads to absurd results ruling out objects we’d clearly consider planets based on their location – an Earth or Jupiter-type planet hypothetically located in the Oort cloud would be excluded yet we’d clearly still call it a planet otherwise!

    3. The “dwarf planet-dwarf” star analogy – just as dwarf stars are still stars so surely are dwarf planets still planets. Extrapolating the “dwarf planets don’t count” line to the stellar realm would imply our Sun is not a proper star nor are 99 % of all stars – those 90% on the main-sequence and the 10 % of “stellar corpses” such as white dwarfs and neutron stars.

    4. Inconsistency and inapplicability in regard to exoplanets – the IAU definition excluded planets of other stars. Yet surely planets orbiting other suns are no less planets for not orbiting our star! There are also more inconsistencies with at least one planet smaller than Pluto (PSR B 1257+12 e ) known and one exoplanetary situation (HD 45364.) analogous to Neptune-Pluto situation

    5. Pluto is a complex world with the key aspects of planets – like the other outer planets (& beating Mercury & Venus) Pluto dominates its own family of three moons (Charon, Hydra & Nix), one of them large enough tobe aworld in its own right – and perhaps even has a system of rings too!

    6. Pluto also has its own atmosphere, (unlike Mercury) and has a complex weather system incl. snowfall as well as being geologically (hadeologically?) differentiated and structured. It thus meets all the criteria for planethood with the sole exception of the absurd “orbital clearance” criterion.

    7. When planetary systems are forming, planetary orbits often cross and interact in unpredictable ways – but this doesn’t stop planets from being planets! Yet by the IAU’s “orbital clearance” criterion, these objects – even ones Jupiter sized and above – are NOT strictly planets because their orbits are not yet cleared. This situation may later repeat in the distant future too eg. when our Sun passes through the red giant & white dwarf stages.

    8. By IAU definitions planets cannot collide because their neighbourhood then isn’t clear. By the same logic nor can they exist as binaries or “double planets” . This appears contrary to common-sense and consistency. It also has potential for creating trouble with the possiblity that some exoplanets may exist in this form – even potentially twin Neptunes or Jupiters. Indeed, given that some would describe the Earth-Moon system as well as the Pluto-Charon one as such a ‘double planet’ then a strict definition of the IAU rule may rule our Earth out of planetary status!

    9. The undemocratic manner in which the IAU ruling was made. Of the 10,000 IAU members only 2,500 attended the Prague meeting that demoted Pluto from planetary status. Furthermore, of those 2,500 only the merest handful – just 424 actually got to vote making therefore a very unrepresentative decision. Among those to excluded from voting and arguing their case in that last minute meeting were some highly relevant and articulate people – notably Pluto expert Alan S. Stern, head of the New Horizons mission.

    10) The first proposed IAU definition of ‘planet’ (that would have included Pluto, Eris and Ceres) was much better in terms of logical consistency and general application as well as being more easily explained, understand and applied – ie. two main criteria for planets are that they are objects circling a star directly which are not themselves stars or brown dwarfs and are rounded by their own gravity. Other superior definitions to the IAU can also be found all of which include Pluto. (For example see comment # 39 above.)

    11) Cultural and historical reasons – noting Pluto’s long-established and culturally scientific place as a recognised planet from its discovery in 1930 until its (hopefully brief) demotion in 2006. These include the slight to Clyde Tombaugh’s memory, widow and family plus the perceived political aspect of stripping from planetary status the sole planet discovered by an American.

    12.) The demotion of Pluto has had a massively negative reaction being unpopular with the general public and many astronomers with a large number even refusing to accept the IAU’s authority outright. The IAU demotion of Plto has brought astronomy and science generally into disrepute and threatens to split the astronomical community – it is in their interests then for this mistake to be speedily corrected and Pluto restored to its correct planetary status.

    *****

    PS. If you think this looks familiar, yes, I’ve posted these ’12 reasons why Plut0 *is* a planet’ before here in other forms & variants before ages ago in past threads but I hope its still okay to post them again here – my apologies if not.

  36. Plutonium being from Pluto

    @ 29. Blizno Says:

    I have decided to avoid dying from a car crunching my bicycling self or a gamma-ray burster toasting my planet before I can see Pluto up close. I expect Pluto to look like Mercury with less cratering and with a dusting of frozen atmosphere, but see it I must.

    Yeah good idea – you’ll love it! My planet is much better looking than Mercury! We’ve got Moons, rings, craters, cyrovolcanoes – far bigger, more numerous & better than Triton’s, the whole “double planet” scene with Charon & our misty snowing atmosphere. New Horizons is in for a treat and I’m sure you’ll all love what you see. :-)

    @ 18. Jack Hagerty Says:

    1. Plutonium Says: “hope you like your liquid nitrogen tea just above absolute zero.”

    Wouldn’t that make it nitrogen ice by something like 100K?

    Er .. yes well spotted – but it all depends on the pressure & a few anti-freezing impurities (ie the “tea” & alcohol) you see. Our kettles are very specially designed! ;-)

    @ 31. Laurel Kornfeld Says:

    … yes, Pluto is definitely a party planet. You should see the jacuzzis and pools some of us Plutonians have.

    Oh Hades yes! You’re welcome to come celebrate Earth’s newest year here! ;-)

    Wishing everyone a Happy New Year & clear skies for 2010 whether they’re on Pluto or Earth or the International Space Station or anywhere else! :-)

  37. 40. Plutonium being from Pluto Says: “I take it you mean Eris?”

    Actually, I meant Vesta, another asteroid rather than a KBO. I have no idea why I said “Eros.”

    I blame the cold meds…

    – Jack

  38. Gary Ansorge

    43. Jack Hagerty:

    Obviously, you were referring to some old Greek definitions of love(Eros, Platanos and Agape).

    Have you had YOUR Eros today?

    GAry 7

  39. God, no, not THIS discussion again from Pluto crackpots…

  40. StevoR

    Yes, this discussion – but why call us “crackpots”? :roll:

    Is it just that you disagree with us or do you have something to actually back up that insult?

    What exactly makes my arguments & those of others who see that Pluto is indeed a planet & the IAU got it horribly wrong “crackpottery”? Do tell. Really – I want to know.

  41. Plutonium being from Pluto

    @ 43. Jack Hagerty Says:

    40. Plutonium being from Pluto Says: “I take it you mean Eris?” Actually, I meant Vesta, another asteroid rather than a KBO. I have no idea why I said “Eros.” I blame the cold meds… – Jack

    Fair enough. Hope you’re feeling better soon & hope you have a great new year too. :-)

  42. Messier Tidy Upper

    @ 43. Jack Hagerty Says:

    40. Plutonium being from Pluto Says: “I take it you mean Eris?”

    Actually, I meant Vesta, another asteroid rather than a KBO. I have no idea why I said “Eros.” I blame the cold meds…

    I’d be kind of neat to have both the largest asteroid Ceres & the brightest asteroid Vesta (the onlyone visible to the unaided eye) count as dwarf planets. Ceres is certainly round enough but I think Vesta is borderline with a massive crater “chipping” it.

    Far as I know the asteroid candidates for asterodis are pretty much limited to those two and Pallas unlike the ice dwarf candidates (Makemake, Haumea, Quaoar) etc .. which a lot more numerous.

    Hope your feeling better Jack & hope everyone’s got the New Year off to a great start. :-)

  43. Spectroscope

    ^ Vesta ( http://en.wikipedia.org/wiki/4_Vesta) is quite likely not round enough with, yes, a very large crater distorting its shape.

    The Dawn spaceprobe (http://en.wikipedia.org/wiki/Dawn_Mission) will give us a good view of Vesta from 2011 when it’s scheduled to start orbiting it – just next year now.

    Both Vesta & Pallas (http://en.wikipedia.org/wiki/2_Pallas ) are borderline Dwarf Planet Candidates and, as far as I know, are the only asteroid DPC’s with Ceres currently the very smallest officially recognised dwarf planet (I presume you meant DPC’s not asteroids which they’re already classed as MTU! (48) ;-) )

    It seems having a mainly icy composition makes it a lot easier to get round than rock does. Pallas appears to be roughly octahedron rather than round and my gut feeling is that it & Vesta will just narrowly miss out on DP-hood but I guess we’ll have to wait & see.

    For a list of DPC’s check the Wikipedia page here :

    http://en.wikipedia.org/wiki/List_of_dwarf_planet_candidates

    Thanks to everyone who wished me & others here a happy new year & same back at y’all. Have a great 2010 everyone. :-)

  44. Thanks, everyone, for the good health wishes. This is just a garden variety cold (not the “flu” or anything that would garner some sympathy).

    It’s ground down to just some sinus pain. Not even enough to keep me away from the keyboard…

    – Jack

  45. Messier Tidy Upper

    @ 49. Spectroscope Says:

    (I presume you meant DPC’s not asteroids which they’re already classed as MTU! (48) )

    You mean here?

    “Far as I know the asteroid candidates for asterodis dwarf planets are pretty much limited to those two and Pallas …”

    Er .. yes. (Blushes.)

  46. Spectroscope

    @ 50 Jack Hagerty :

    No worries. Glad to hear it. :-)

  47. Astroquoter

    “…Marc Buie can very easily imagine what it must be like to walk around on Pluto: with less than 1% of your weight on Earth because of the low gravity, at temperatures of 230 degrees below zero, in the twilight because the Sun is nothing more than a dazzling star in the black sky, across snowfields of methane ice and transparent crystals of frozen nitrogen and with a gigantic moon hanging overhead – at least if you are on the right side of the planet.”
    – Page 61, ‘The Hunt For Planet X’, Govert Schilling, Copernicus Books, 2009.

  48. StevoR: your discussion “twelve reasons…” is too long. So I will take it one by one, starting from easiest (yeah, I am lazy ***).

    “7. When planetary systems are forming, planetary orbits often cross and interact in unpredictable ways – but this doesn’t stop planets”
    Ever heard about so-called “protoplanets”?

    “from being planets!”
    These objects weren’t planets YET in that moment of solar system history.

    Do you have something to say? Or we can now discuss another point from “ELEVEN reasons…”? :>

  49. The IAU never had the power to demote or promote anything. It is a matter of language. If enough people call Pluto a planet it is. A segment calls it a planet and a segment doesn’t. You can’t rewrite old usage so that suddenly it is wrong. I invented the slowly catching on word Exodwarf and wrote an article about Planet definition on my blog that I am fixing to allow comments.

  50. I’d be kind of neat to have both the largest asteroid Ceres & the brightest asteroid Vesta (the onlyone visible to the unaided eye) count as dwarf planets. Ceres is certainly round enough but I think Vesta is borderline with a massive crater “chipping” it.

    Far as I know the asteroid candidates for asterodis are pretty much limited to those two and Pallas unlike the ice dwarf candidates (Makemake, Haumea, Quaoar) etc .. which a lot more numerous.

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