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Pluto was discovered by a manual search of the sky using a blink comparator. This is an extremely laborious process. For Pluto, it made sense to go to all this trouble, because there were indications that a ninth planet had to be out there: Neptune's orbit was perturbed by the gravity of another planet, it seemed. Later, it turned out that that wasn't the ...


31

There are a few special things about Pluto, as compared to the other dwarf planets in the Kuiper belt. These include: It is the largest dwarf planet known, by diameter. (Note, this was only determined after the New Horizon's flyby) It orbits relatively close to the Sun, at times it is even closer than Neptune! It has the largest satellite system of any non-...


12

The flyby distance will depend on how accurately they can measure 2014 MU69's orbit. This KBO was discovered only 3 years ago, and because it's so faint we only have a few observations to go on. For the Pluto encounter, the NH team went back to the Lowell observatory archives to measure the original plates made by Tombaugh when he discovered Pluto, in an ...


11

According to this blog post, the artefact was caused by scattered light reflected off some element inside the telescope. The ghostly circular pupil image and the little dots that are moving around in the image (and that aren’t JR1) are scattered light from a nearby bright star. LORRI isn’t that big of a telescope – just a little bit smaller than an 8-inch ...


5

I was wondering, are the comets 67P/Churyumov-Gerasimenko and 103P/Hartley 2 the only Kuiper Belt comets to date that have their water D/H ratio measured? Have we determined the water D/H ratio of any other comet originating from the Kuiper Belt? I ask as I'm trying to assess the likelihood that Kuiper Belt comets provided the main source of delivery of ...


5

To use the longer base line of 100 AU instead of 2 AU, we need measurements from both the probe in the Kuiper Belt and another probe near the earth. But the data transfer over 100 AU distance is very slow. But such parallax measurements are done for thousands to millions of stars, see the pages about the probes Hipparcos https://en.wikipedia.org/wiki/...


5

It's unlikely. Per one of the scientists working navigation on the New Horizons mission, Simon Porter, Lack of known objects prevents [targeting an additional flyby]; PT1 is almost on the outer edge of the [cold classical Kuiper Belt]. Many expensive hours of Hubble time and months of calendar time were dedicated to finding the three candidate objects. ...


5

I'm confident that if New Horizon's can reach another target, they will attempt to visit it. One of the reasons PT1 was selected as the target is that it was the closest object they could reach, leaving a reasonable amount of delta v, about half of what remained after flying by Pluto. I'm also confident they will try to find such potential targets. However, ...


4

As close as they think can safely be achieved. I expect that will be in the range of hundreds of km, but that's purely speculation. It should be a fair bit closer than Pluto, however, because there they do not have to worry about flying too close to debris orbiting 2014-MU69. It's Hill Sphere is only about 400,000 km, and it seems likely that there wouldn't ...


4

A comet has to approach the Sun to within its snow line to start sublimating volatiles and form coma and the tails. For our Sun, its snow (or frost) line is at roughly 5 AU (Astronomical Units), so at about the closest approach of Jupiter to the Sun in its orbit (its perihelion). Pluto orbits way past the Sun's snow line in too circular orbit to approach ...


3

One reason is its brightness. Pluto passes near and far and the atmosphere freezes and thaws. So while most bodies are pretty dingy, Pluto is covered with fresh snow.


2

One reason not mentioned is an accident of timing. But for an orbital coincidence, what we now call Eris might have been discovered before, or at about the same time as, Pluto. Eris has an absolute magnitude of about -1.17, versus Pluto whose absolute magnitude is -0.7. The greater absolute brightness of Eris is one reason Eris was originally thought to ...


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