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103 votes
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Did I see Pluto with my naked eye?

Pluto is something like magnitude 14. The limit for the human vision is somewhere between magnitude 6 (widely accepted) and 8-ish (highly trained observers with perfect vision in ideal conditions ...
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37 votes

What if Earth and Moon revolved around each other like Pluto and Charon?

They do, but due to the ratio of masses being vastly different, they seem like they would not to do so as moon seems to rotate just around (the centre of) Earth. The ratio of Earth and Moon's masses ...
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31 votes
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How did New Horizons take such well-lit pictures of Pluto?

It's brighter on Pluto than you think. NASA developed a tool called Pluto time, which tells you when at your place the ambient light conditions are similar to the ones on Pluto. This occurs when the ...
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30 votes
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Can Pluto be seen with the naked eye from Neptune when Pluto and Neptune are closest?

No, it cannot. Far from it. The closest approach between both planets is roughly 16 AU due to the 3:2 orbit resonance. Pluto will even then be a tiny dot among many with a brightness around 14 mag. ...
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17 votes

Did I see Pluto with my naked eye?

As Florin correctly stated, it can't have been Pluto. You have probably looked at it and you have even gotten its light in your eyes. That little itty bitty shine just has no chance to make your ...
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17 votes
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How bright is it on Pluto in the middle of the day?

Back when New Horizons was preparing for its flyby back int 2015, NASA's website set up a tool to allow you to experience the brightness of light at High Noon on the subsolar point on Pluto. From ...
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14 votes

What if Earth and Moon revolved around each other like Pluto and Charon?

On barycentres The Pluto-Charon couple is not qualitatively different to the Earth-Moon couple with regards to orbits. As was pointed out in other answers, in both cases, the two bodies revolve ...
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14 votes

Is Pluto a "proto-planet"?

Pluto will never be a planet. There are a number of technical papers that give more precise meaning to the concept of "clearing the neighborhood". It's not just now, it's can the object in question ...
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  • 27.1k
14 votes

Can Pluto be seen with the naked eye from Neptune when Pluto and Neptune are closest?

According to the NASA Pluto fact sheet, the brightest that Pluto gets is an apparent visual magnitude of 13.65 when it is 28.6 au from the Earth and (presumably) about 29.6 au from the Sun. To work ...
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  • 114k
12 votes

Is Pluto still a dwarf planet?

Yes, Pluto is still a dwarf planet. According to the IAU website, it still fits the criteria for a dwarf planet, fails to meet the criteria for a planet, and still carries the "dwarf planet" label, ...
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12 votes

Do Pluto and Charon have unusual Lagrange points?

The L1, L2, and L3 points are unstable in any orbital system. (source) The L4 and L5 points of a pair of bodies are only stable if the larger of the bodies is at least 25 times as massive than the ...
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  • 2,958
9 votes

What is the resolution in megapixels of the Hubble Telescope?

The size of the cameras that took the Pluto pictures is easy enough to find: the ACS Wide Field Camera has two 2K by 4K (hence 8 Mega pixel) CCDs, with a field of view of 202×202 arcsec. The high ...
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8 votes
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Why is there a black stripe in the Hubble images of Pluto?

That photograph is a composite of two images taken with different exposure times. To be correct we'd have to say that the exposure of the two photographs is different, i.e. the outer photo was created ...
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8 votes

How bright is it on Pluto in the middle of the day?

These two calcs agree pretty well: The Sun's magnitude from from Pluto is -18.7 m = -18.75 magnitudes That's quite a bit brighter than a full moon, so you'd be able to read by it.
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8 votes
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What's the temperature of Pluto's core?

TL;DR: 1000 K (according to differentiated model of Pluto) According to the density value of Pluto, astronomers proposed three types of structural models: Undifferentiated or "cold" model: ...
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7 votes
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What's to be gained from the New Horizons mission once it's beyond the Kuiper Belt?

Possible rendezvous with a Kuiper belt object and Voyager type data on the heliosphere: "We should have power until the 2030s, so we can get into the outer part of the heliosphere," says Spencer. "...
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7 votes

Why is there a black stripe in the Hubble images of Pluto?

Pluto itself so bright that Charon would not be visible in the image if it were exposed in a way to show the remaining moons. Likewise, the remaining moons as so faint as to not be visible in an image ...
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7 votes
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How much more massive would Pluto have to be to clear its neighborhood?

This Wikipedia page does a decent job of describing the orbit-clearing criterion, based on the original paper by Stern & Levison (2002), which can be found here (PDF). In order to have cleared ...
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7 votes

Shall we say now that Pluto is "larger than Mercury" ?

The implication of the question is that this extra 1000 miles should be added to Pluto's radius. The answer is no. For all of the solid planets, it's that solid surface (or solid+liquid surface in the ...
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  • 27.1k
7 votes
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Is Pluto a "proto-planet"?

The question says a few interesting things: The system orbit isn't on the ecliptic The system hasn't cleared its neighbourhood These are not going to change in the next few million years - or ever. ...
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  • 2,377
6 votes

Could Pluto and Charon have extra-Solar origin?

The surface of Pluto is not just young, but very young, and also differentiated. The 'heart', Sputnik Planum, may be currently active, with flowing glaciers, and nitrogen snow. This area may have be ...
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6 votes

Is the point of this paper to say that Pluto's status as a planet should have been handled scientifically, rather than by a vote?

Part of the problem here is semantics. The meaning of "planet" was really poorly defined prior to 2006 (and some argue that it still is). In the early 2000's, this started to become an issue. You ...
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6 votes
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How many solar system objects that can really qualify as a KBO are likely to enter Pluto's Hill sphere each day?

The Hill sphere radius of Pluto is about $r$ = 6 million km. Most of the Kuiper belt is in prograde motion around the Sun (like Pluto). Pluto's average speed is under a lazy 5 km/s for an orbital ...
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6 votes
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Why does Wikipedia state that the Solar System has one unconfirmed planet?

That was a rather recent (16 January 2021) change to that wiki page made by a user named Mariofeds, who does not have a wikipedia user page and who has just one contribution to wikipedia. It may well ...
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  • 27.1k
6 votes

why the difference in resolution for images of Pluto?

Basically you say it yourself: The reason is in the flyby itself. One doesn't cover every part of the surface with equal resolution when just passing by. Some parts (as seen in the lower part of the ...
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  • 10.8k
5 votes
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Does Pluto have impact craters?

It was predicted by some, before the images arrived, that Pluto's craters would be much shallower than perhaps on other rocky objects/satellites. The reason is the icy composition and the relatively ...
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  • 114k
5 votes

Would Pluto keep an orbit without its moon?

The orbit of a planet does not in any way depend in its moons, mass or own gravity. The orbit is the same for a grain of dust as for a giant planet. It only depends on the mass on the Sun and the ...
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  • 10.8k
5 votes

Pluto- Current theories regarding its geological nature?

Geothermal activity can originate from a combination of: Residual heat from planet formation: During the formation of a planet, half of the potential energy of the parent region of dust and gas can ...
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  • 181
5 votes

Why is there a black stripe in the Hubble images of Pluto?

I'm pretty sure that the stripe is there because the two sections of the image have different contrasts. Pluto and Charon are so bright relative to Nix, Hydra, P4 and P5 that to have one contrast, ...
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