New Horizons

[me123]

The next few weeks will be quite exciting for those of us interested in astronomy. Working with NASA, a team from John Hopkins University in Maryland, USA have sent a probe to visit the dwarf planet Pluto. This will be our first visit to a trans-neptunian object, and the furthest object from Earth that we have explored. At the closest point on the flu-by, on the 14th of July, we will get our first proper look at Pluto and her five moons.

It's been a long mission. The probe, which was launched back in January 2006, is traveling at 30,800mph, and even at that speed it's taken almost ten years to reach Pluto. During the course of its mission Pluto has been controversially "relegated" from planetary status into the new category of "dwarf planets". And we've discovered plutonian new moons since the mission was planned: Nix and Hydra, found in the year prior to launch, and more recently the small moons of Kerberos and Styx.

Of course, the great distance has been a massive technical challenge for the scientists involved. They've had to manoeuvre a space craft the size of a piano across the solar system to get to Pluto and fly past it, close enough to get the best images, but without colliding with the planet or any satellites around it. The challenge is compounded by the distances involved for communicating with the spacecraft - it's now so far away that it takes four and a half hours to send a message to New Horizons. Similarly, it will take four and half hours for the data to reach earth, and many hours for each individual image to be downloaded.

We're already seeing some of the best images of the Pluto system that we've ever seen. The best images we've had until now were blurry at best: such as the 2010 Hubble images:

What we're seeing now is still quite low-resolution, but we've got some really interesting pictures in the meantime:

Pluto and Charon orbiting their Barycentre.

Most recent LORRI image of Pluto & Charon from New Horizons

These are already giving us data and interesting new observations - for example, it's beginning to look like Charon and Pluto have a completely different composition, suggesting that they were formed completely separately. Given the high quality images taken of the Jovian system, I'm sure we won't be disappointed. Every day, as the spacecraft closes in on its target, the pictures will get better and better.

I'm certainly going to be very intrigued to see the pictures when they come back to us, and to learn about more about these bodies. I wasn't around for the groundbreaking Voyager missions and their "Grand Tour" of the solar system - I'm sure many members were (and, in fact, there may even be some members who recall Pluto being discovered, although I don't know if we have any nonagenarians who visit regularly?). Whilst this won't be a planetary fly-by after the IAU declassified Pluto, the prospect of learning more about a Trans-Neptunian Dwarf Planet are perhaps even more exciting.

And the mission probably won't end there. It's hoped and expected that NASA will fund the mission beyond its Pluto encounter, to divert the craft towards some smaller KBOs.

 

[ainsworth74]

Just to clarify but they've gone all the way to Pluto (taking nearly ten years) to just do a fly-by? Presume the physics mean it was impossible to slow down enough to loiter in the vicinity of Pluto and Charon?

Don't get me wrong that's not a criticism, more disappointment, as if it were up to me we'd be doing an awful lot more exploration of space including an actual properly active manned mission to Mars (as well as a manned flyby of Venus as proposed here) along side a lot more probes.

 

[me123]

Sadly, yes, it will be a fly-by. The probe's going far too fast to enter orbit. Pluto has a relatively weak gravitational pull which would mean we'd have to slow down on approach, which would require a lot of fuel. Any missions would be decades long, and you'd need a funding source that's willing to wait that long for results. Given that Pluto is now moving even further away at the moment, I wouldn't expect it to happen in our lifetime (bearing in mind we have only been to Uranus and Neptune once, and FWIW we've got loads to learn on those planets!).

However, don't dismiss the fly-by entirely. Until relatively recently, the best images we had of the gas giants were from the Voyager spacecraft flying by. These are still the only close-up images we have of Uranus and Neptune. In fact, when Voyager 2 passed Neptune, it was going faster than New Horizons will go past Pluto. We got good images then, and technological advances will mean that we should get even better images of Pluto.

Furthermore, although funding hasn't been confirmed, as long as this mission is a success I suspect they'll get funding to continue with the mission and visit even more Kuiper belt objects. And, the further it goes, the more we can learn about the environment of the outer solar system.

 

[ainsworth74]

The probe's going far too fast to enter orbit. Pluto has a relatively weak gravitational pull which would mean we'd have to slow down on approach, which would require a lot of fuel.

Yes thought that would be the case. Much easier for a probe like Galileo to scoot out to visit Jupiter and its moons and then hang around them all for ages as it had Jupiter's huge gravity well to decelerate in. Still a bit annoying having spent so long getting there to only zip by!

However, don't dismiss the fly-by entirely.

I wasn't doing that at all. Like I say if it were up to me we'd be doing a lot more missions like this

 

[NorthernSpirit]

The only problem to sending probes further than Mars, is that they require to be powered off Plutonium 238 and sadly there isn't much of it left. So hopefully New Horizons will use every ounce of it in its dual RTG's to obtain even more info.

 

[DarloRich]

1) Is Pluto not a planet now?
2) What happens to the probe AFTER it zooms past Pluto?
3) For how long can it return information to earth?

 

[me123]

1) No. the International Union of Astronomy defined a planet in a controversial resolution in 2006:

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 neighbourhood around its orbit.

It also defined a dwarf planet as:

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) shape,
(c) has not cleared the neighbourhood around its orbit, and
(d) is not a satellite.

Pluto technically hasn't cleared its orbit. Part of the reason for redefinition is that new Trans-Neptunian Objects are being discovered all the time, the first such body being what is now know as the minor planet Eris, discovered in 2003. It became clear that Pluto was one of many such objects that had an elliptical and eccentric orbit, and rather than being a planet, was a member of another class of objects, dubbed dwarf planets or, more specifically in its case, the first member of a group come to be known as "Plutoids", which has been defined as:

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.

It's a controversial decision, really more for emotional reasons than anything else. It's not agreed by all, and some scientists (including those in the New Horizons team) will argue that Pluto is a planet. It had the very unusual impact that the New Horizons mission launched to explore the 9th planet, but will end up exploring the first known Plutoid, which is probably a more exciting concept.

2) Technically, the mission ends when the encounter is over in January 2016, and the probe will continue flying into space. In reality, it is expected that there will be funding to continue the mission to manoeuvre the spacecraft to explore at least one Kuiper Belt object over the next few years, with an expected end to the mission in 2026.

However, like the Voyager probes before it, it will continue to function and whilst it's continuing to function it will probably still continue to send much less glamorous, but very important data about the outer heliosphere. The Voyager craft will continue to send data for the next 15-20 years, and by careful use of the power source and rationing the power (for example, by turning off the cameras and other instruments that won't be needed), the probe could be functioning for quite some time.

3) It's not known exactly when it'll stop functioning. It could be 2038. With the Voyager probes functioning for 38 years, there's potentially a lot of time for observations of the outer solar system. It'll ultimately be limited by its power source.

 

[GrimsbyPacer]

According to those requirements it's possible to classify Pluto as a planet.
It orbits the Sun like most objects in the system.
It's round as the pictures show like many smaller worlds too
It's not a moon, although it's a double planet system with Charon.

The cleared the neighbourhood requirement that downgraded Pluto is flawed.
Eris is further from Pluto than the Sun to Earth a great many times!
And Pluto crosses Neptune's orbit ocassionally, since Neptune hasn't cleared it's orbit does that make Neptune a Dwarf planet also?
Even Jupiter has Trojan Asteroids in it's orbit around the Sun so it hasn't been cleared.

The real reason it was unmade a planet was that scientists want a short list for some reason. Ceres was a planet when found, but when others were found later so a new classification of asteroid was made up. Same again when the Planets as they were known, were found orbiting Jupiter and Saturn.

As far as I am concerned, it's a planet like Eris is also.
It will be interesting to see Pluto and Charon with their four minor moons with chaotic orbits. Also I am surprised by Pluto's apparent Orange colour.
I remember hearing somewhere that another smaller world will be visted by the probe after Pluto but there are two choices, it was on Space.com and I'll try to find tonight.

 

[me123]

As I've said, it's a controversial reclassification.

Pluto hasn't cleared its neighbourhood. Like Eris and other dwarf planets, such as Makemake and Haumea, it forms part of the Kuiper belt. Ceres, similarly, forms part of the Asteroid belt.

Jupiter has cleared its field, with the Trojan asteroids orbiting in resonance with the planet. Similarly so with Earth and 3753 Cruithne. Neptune has also cleared her orbit, and in fact the orbit of Pluto is testament to his fact. The orbits don't actually meet at any point due to the inclination of Pluto's orbit, however even if they did meet the orbits are in resonance, so they never could collide. In fact, the complexities of Neptune's orbit all suggest that the neighbourhood has been cleared.

I would agree that Pluto and Charon in fact form a binary (dwarf-)planetary system, as can be seen in the image in my first post above. None of this is intended to make Pluto any less significant - in fact, being a dwarf planet, a Plutoid; it just makes this mission all the more interesting, and makes Pluto itself all the more special! It's a real testament to Clyde Tombaugh that Pluto was discovered some 73 years before any other such objects.

Science is always changing, and we learn new things every day. Ultimately, the classification of planets is a man-made definition. But I think we have to trust that the leading body in its field knows what it's talking about.

 

[DarloRich]

me123 - thanks. i find all this fascinating although my knowledge of such things is about 0 and what I do have is based on some schoolboy astronomy and physics!

I am interested to know the spacecraft will try to look further into the Kuiper belt and the "trans Neptune" area generally. I think i am right in saying our knowledge of this area is very limited

PS i don't care what any bunch of scienticians say - Pluto is a planet in my book!

 

[NorthernSpirit]

3) For how long can it return information to earth?

There should be enough power in NH's RTG to last until around 2026 after which it all depends on if the probe is still functioning, if it is then it'll continue to be used until the RTG runs dry.If not, its game over.

 

[DarloRich]

There should be enough power in NH's RTG to last until around 2026 after which it all depends on if the probe is still functioning, if it is then it'll continue to be used until the RTG runs dry.If not, its game over.

what is the "lag" on the communications from that kind of distance? I assume it is a microwave transmission via the Deep Space Network must there must be a hell of a delay!

 

[GrimsbyPacer]

Light takes 5.5 hours to get to Pluto from the sun at it's current distance of 39.4 AU. Microwaves should take roughly the same time, but Earth orbits 1 AU from the Sun (8mins away) so it must vary slightly.

 

[me123]

The spacecraft encountered some technical problems over the weekend, but it's expected to be back up and running tomorrow. In the meantime, we're getting closer, and we're getting better pics too! Apparently, the "core" aspects of the mission - the close-up flyby, hasn't been affected. (Unfortunately, I can't post them here as they're massive, but click through to see).

Picture 1
Picture 2

I expect the pictures we'll get once it's back up and running will be even better; having had 3-4 days without science the probe will millions of miles closer to Pluto since its last observations. It's certainly looking quite different to what I'd have expected!

 

[me123]

We (as a species) have now flown past Pluto and the spacecraft is heading out into the Kuiper Belt. The spacecraft has started sending the data back to us, and it's due to reach Earth soon. In the meantime, here's the best photo so far of Pluto.

 

[TheEdge]

In a bizzare way I found that image to be a bit of a anticlimax. There have been so many years of artists impressions and descriptions of Pluto being this alien world barely recognisable as a member of the solar system and it just turns out to be a fairly plain looking grey rock.

 

[Peter Mugridge]

It looks more of an orangey-red to me, like a paler version of Mars. This assumes that is a real-colour image and hasn't been adjusted to false colour for scientific purposes.

 

[GrimsbyPacer]

The choice of which minor planet New Horizons will visit in the Kuiper-Edgeworth Belt will be made in August.

I'm glad the mission went well.
Not only does Pluto have a giant heart and a whale as surface features it has pale near white, orange, and black colour in different regions.
It's hardly just a frozen grey rock some expected.

Pluto and Charon are tidally locked meaning that one hemisphere on each part of the "double planet" faces the other always. Still waiting for the pictures of Pluto's moons, Nix, Styx, Kerberos and Hydra though.
Charon is black and grey and looks totally different to Pluto, which is interesting.

When will the next mission to explore these strange new worlds start?
Eris, Makemake, Quoar, Sedna, Haumea are all large with virtually no information available on them. I hope NASA decides to fund a second mission soon.

New Horizons launch back in 2006 is worth a watch, being the fastest ever.

 

[TheKnightWho]

For those arguing about the planetary definition:

Pluto is a member of the Kuiper belt - a Kuiper Belt Object (KBO) - and therefore it makes far more sense for it to be classified as a dwarf planet (especially when you consider it is technically a binary system with its "moon" Charon, with all 4 of its real moons orbiting the two of them).

However, there are several reasons we discovered it long before any other KBO: it's on the absolute inner edge, and GrimsbyPacer is correct to point out it is sometimes closer than Neptune, although their (possibly coincidental) resonance means they can never cross paths, meaning Neptune has cleared its orbit. It's also extremely large for a KBO, with only Eris being the same size, albeit with more mass than Pluto. However, it's the methane ice surface that is the primary reason we discovered it so quickly - methane ice is similar to water ice in many ways, including reflectivity, which makes Pluto shine an extraordinary amount for something of its size and distance from the Sun. Many large KBOs don't benefit from having such a bright surface, so we didn't discover them until far later.

 

[Clip]

If you look at the lighter shaded area of the bottom of that picture and trace the outline of it does it look similar to its cartoon namesake?

*Granted this was pointed out in the papers today but its dead canny

 

[GrimsbyPacer]

TheKnightWho, the IAU's planet classification method is flawed.
First of all the creator of the Dwarf Planet term disagrees with Pluto not being a planet anymore. And second, Alan Stern who is the biggest Pluto expert you'll find still regards Pluto as a planet, and he's running the New Horizons mission.
Thirdly, the vote that declassified Pluto was held when only 400 out of nearly 10,000 eligible voters could attend, so I don't take notice of that.

I can also see potential problems with their criteria.
1, Orbits the Sun directly.
Jupiter orbits a barycentre in space in a similar way to Charon and Pluto, does that make Jupiter a dwarf planet or just not a planet at all?
2, Hydrostatic equilbrium (round shape).
So if a 10,000km cube of rock was discovered it wouldn't be a planet?
This is a rather strange rule since most objects are round anyway.
3, Cleared the Neighbourhood.
Cruithe clearly runs into Earth orbit commonly, is Earth not a planet?
Trojans around Jupiter and Neptune suggest they aren't planets either.
Asteroids still strike all planets, are they all dwarves?

Personally I count planets as having a 1,000km diameter solid object.
Alan Stern's Satelite Planet idea isn't bad either, but not really needed.
Smaller down to 100km diameter can be dwarf, and minor planets below that.

 

[TheNewNo2]

Personally I count planets as having a 1,000km diameter solid object.

Well the gas giants aren't really "solid"...


The problem with all this is that as humans we like putting things into neat boxes, but the universe (outside of mathematics) isn't like that. For instance we talk of species as a discrete thing, but things evolve and change, and eventually they wouldn't be able to reproduce with their "species X" ancestor, which would make them distinct "species Y". But in between there will be a generation which could mate with either species X or Y - what do you call those?

With planets it's similar - we have to come to an agreement of what constitutes a planet, and what we came up with excludes Pluto and also a lot of similar objects in the asteroid belt and Kuiper belt. That doesn't change what Pluto is (a ball of rock a long way away), nor does it make it less important as a historical object.

 

[Peter Mugridge]

If you look at the lighter shaded area of the bottom of that picture and trace the outline of it does it look similar to its cartoon namesake?

*Granted this was pointed out in the papers today but its dead canny

I thought it was a bit of a Goofy statement when I saw it.

 

[GrimsbyPacer]

Well the gas giants aren't really "solid"...


The problem with all this is that as humans we like putting things into neat boxes, but the universe (outside of mathematics) isn't like that. For instance we talk of species as a discrete thing, but things evolve and change, and eventually they wouldn't be able to reproduce with their "species X" ancestor, which would make them distinct "species Y". But in between there will be a generation which could mate with either species X or Y - what do you call those?

With planets it's similar - we have to come to an agreement of what constitutes a planet, and what we came up with excludes Pluto and also a lot of similar objects in the asteroid belt and Kuiper belt. That doesn't change what Pluto is (a ball of rock a long way away), nor does it make it less important as a historical object.

Good post, but the gas giants will count as long as the have a solid core 1,000km across. All in the Solar system easily meet this requirement and I expect virtually all exo gas giants to have a solid core too. Either from extreme pressure or from magnetic field scooping asteroids up. If Saturn had nothing but gas it will be a nebula wouldn't it? I'm certain my measure is much better than the IAU's.

 

[Darandio]

Press conference is scheduled for 8pm BST. Watch it live here...

http://www.nasa.gov/multimedia/nasatv/index.html

 

[ainsworth74]

Wow! I've just been watching the livestream and wow is the only word that describes it!

Image of Pluto here and one of Charon here.

 

[me123]

Me too. And I agree. Wow. The pictures are amazing. Charon in particular is looking spectacular - it's so uneven, those cliffs and canyons must be huge! (They said 4 miles in the conference IIRC?).

And then, here's the first of many high resolution images of Pluto's surface. The technology on this probe is amazing. Bear in mind that the probe was moving at over 30,000mph when the picture was taken, unable to communicate with earth and taking this photo on instruction from a computer program.

Really amazing work done by the New Horizons team. There's lots of work ahead too (it'll take 16 months to just download the images to Earth, never mind the analysis of the scientific data). I'm looking forward to seeing the "dark side" of Pluto too - I can't imagine that "Charon-shine" will be amazingly bright but I think the photos will be spectacular nonetheless.

 

[GrimsbyPacer]

The big heart of Pluto (my sister thinks it's an upside down butt) is now called Tombaugh Regio after the planet's discoverer.

The dark area on Charon is called Mordor now.
One can not simply walk to Mordor!

 

[TheKnightWho]

TheKnightWho, the IAU's planet classification method is flawed.
First of all the creator of the Dwarf Planet term disagrees with Pluto not being a planet anymore. And second, Alan Stern who is the biggest Pluto expert you'll find still regards Pluto as a planet, and he's running the New Horizons mission.
Thirdly, the vote that declassified Pluto was held when only 400 out of nearly 10,000 eligible voters could attend, so I don't take notice of that.

I can also see potential problems with their criteria.
1, Orbits the Sun directly.
Jupiter orbits a barycentre in space in a similar way to Charon and Pluto, does that make Jupiter a dwarf planet or just not a planet at all?
2, Hydrostatic equilbrium (round shape).
So if a 10,000km cube of rock was discovered it wouldn't be a planet?
This is a rather strange rule since most objects are round anyway.
3, Cleared the Neighbourhood.
Cruithe clearly runs into Earth orbit commonly, is Earth not a planet?
Trojans around Jupiter and Neptune suggest they aren't planets either.
Asteroids still strike all planets, are they all dwarves?

Personally I count planets as having a 1,000km diameter solid object.
Alan Stern's Satelite Planet idea isn't bad either, but not really needed.
Smaller down to 100km diameter can be dwarf, and minor planets below that.

1) Everything orbits a barycentre. The important question is whether that barycentre exists inside the body of the object - for the 8 planets it does. For Pluto it does not.

2) A 10,000km radius cube simply *could not exist* naturally. Hydrostatic equilibrium exists as a criterion because it dictates a certain size beyond which something can reasonably be a planet.

3) Resonance is an important consideration. Clearing an orbit means that everything that it is physical possible to run into has been run into/does not exist. This discounts moons, trojan asteroids (which exist in resonance with their parent planets) etc. Pluto has not cleared its orbit anything like as clearly as any of the other planets, as it is a Kuiper Belt Object.

I feel there is far too much nostalgia over Pluto, really. The definition of planet may be considered contentious, but that's not because the IAU's definition is incoherent as some would like to make out.

 

[GrimsbyPacer]

1, despite Pluto's odd shape orbit it's barycentre lies within the Sun.
Jupiter's doesn't, and the Sun's wobble is caused by this.
2, yes it might not exist, but the principle remains. Comet like gas giants with trails have been detected already.
3, it's good to know that the asteroid that exploded over Russia a few years ago won't happen ever again now were a planet! As all asteriods have been cleared, umm they are over 10,000 Near Earth Objects catalogued already so I doubt that's the case.
Also Pluto and Charon have few if any craters unlike Mercury or Mars so maybe they are not many collisions out there as previsiously expected.

I feel there is far too much nostalgia for when there were 8 known planets. I think some people are scared to learn of too many planets that they won't know the names of.

Here's Mordor.