24 votes
Accepted

What caused this mysterious stellar occultation on July 10, 2017 from something ~100 km away from 486958 Arrokoth?

There were three attempts to measure Arrokoth by occultation, and the June 3rd attempt didn't detect anything. The July 10th attempt had a tiny blip, that appeared to be in the "wrong place"...
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22 votes

Where does the Solar System end?

Here's my answer. I'll try to make it as comprehensive as possible. It's pretty hard to define the edge of the Solar System. Most people would probably define it as where objects are no longer ...
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  • 33.7k
12 votes

Where does the Solar System end?

Whenever I see this question discussed, it seems that the heliopause, or some variation thereof, is given as an answer -- and then it's mentioned that the Oort Cloud extends beyond it. A more correct ...
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12 votes

What caused this mysterious stellar occultation on July 10, 2017 from something ~100 km away from 486958 Arrokoth?

According to Wikipedia: A preliminary analysis of all collected data suggested that Arrokoth was accompanied by an orbiting moonlet about 200–300 km (120–190 mi) away from the primary. It was later ...
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11 votes
Accepted

Strange speck of light in the picture sequence of the approach to 2014 Mu69 (Ultima Thule)

It's probably a cosmic ray strike, a common artifact on New Horizons images. The image, however, is of very poor quality which makes it difficult to analyse the exact nature of the spot. I'll go ...
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  • 1,171
10 votes
Accepted

What does the Sun look like from Eris at its aphelion?

Light flux decreases as one over distance squared. So if Eris is 100 times further away from the Sun than the Earth is, then the amount of light that reaches Eris is 10 000 less than that on Earth. ...
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  • 16.7k
9 votes

Why isn't Eris considered a planet despite being the body of dominant mass?

You are correct that the IAU definition of "clearing the orbit" has the problem of being not explicitly quantified. And a complete clearing was obviously never the intention behind the definition. I ...
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  • 2,400
8 votes

Could stellar occultations be used to survey Kuiper belt objects?

Yes this is possible and has been tested by the TAOS (Transneptunian Automated Occultation Survey) group among others. That group is in the process of building the TAOS-II project which will use ...
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  • 7,135
8 votes

Which measurements have shown that 2014 MU69 is red? (New Horizons' next target)

This was a hard one to answer, primarily because of the difficulty in tracking down information. The Observations of MU69 The extended mission for New Horizons involved adjusting its orbit to do a ...
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  • 14.4k
8 votes
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How does 2015 RR245 compare to the other KBOs predicting "Planet 9"?

It was the first thing I thought too, but I would say it won't count in the statistics. The earlier paper by Batygin & Brown was talking about bodies orbiting further out. 2015 RR245 orbits ...
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  • 2,377
8 votes
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Is Planet Nine shepherding the Kuiper Belt?

Estimates of Planet 9's orbit currently suggest that it doesn't have any major effect on the Kuiper Belt, because its orbit is too far away and on a different plane than the Kuiper belt, and from the ...
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8 votes
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What type of planetary-mass object would Planet Nine be?

It is a planet - either a gas giant core, a mini-Neptune, or a super-Earth. First off, Mike Brown has stated outright “It is a planet—there’s virtually no doubt,” he said. “What we now call ...
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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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6 votes
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Orbital period for a 1 light year object?

To answer this, let's visit Kepler's third law which tells you the orbital period of a body, if you know how far away it is. $$\frac{P^2}{a^3} = \mathrm{constant}$$ As it turns out, if you use the ...
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6 votes
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Could rocks from Earth have reached the Kuiper belt, or Neptune at least? If so, how?

(I have tracked down the reference that I made in my comment on the question.) Presumably earth rocks once blasted into space (by volcanism or meteorite impact) gain or lose energy primarily by ...
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  • 2,661
5 votes
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Is it proper to refer to objects beyond Neptune as "Kuiper Belt Objects?"

Yes there is a difference, Kuiper Belt Objects (KBOs) are a subset of Trans Neptunian Objects (TNOs). Other subsets are Oort-cloud objects (OCOs) and scattered disk objects (SDOs). These are not KBOs ...
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  • 3,311
4 votes
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How can the Kuiper belt coexist with the 9th planet?

The recent evidence for the 9th planet is an alignment in various parameters of known Kuiper belt objects. These are not Kuiper belt objects. The Kuiper belt is taken to refer to the neighborhood of ...
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4 votes
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Which measurements have shown that 2014 MU69 is red? (New Horizons' next target)

While the answer by @zephyr is extensive, unresolved images of a very distant Kuiper belt object distant body over a short arc of it's orbit through a single filter can not be used to calculate a ...
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  • 31.6k
4 votes
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How many Kuiper Belt objects have moons? How do we know this?

"Moons" is a misnomer here, the majority of Kuiper Belt Objects (KBOs) with companions are binaries. Now there are several populations in the Kuiper Belt, characterized by their ...
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3 votes
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Kuiper belt planet formation

The Kuiper Belt is fairly large (with inner and outer radii $\sim30\text{ AU}$ and $\sim50\text{ AU}$), but it does not contain much mass. The total mass is likely somewhere between $0.01$ and $0.1$ ...
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3 votes
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What is the farthest reported distance from observer from which a solar system body has occulted a star?

Wikipedia lists some of the most farthest objects from the sun in the solar system. The third farthest object "Eris" was the subject of one of the most distant stellar occultations observed ...
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  • 3,226
3 votes

How many observations does it take to determine the orbit of a TNO

The main problem with determining an object's orbit is we only know the position with certainty in two dimensions. The distance to the object is largely unknown. This accounts for the large ...
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  • 176
3 votes
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Could the trajectories of non-periodic comets be used to infer properties of the 'ninth planet'?

The idea is basically to look for comets coming from the same direction. Look for a pair of comets that at some time earlier in their orbit was at the same place at the same time. That is a data point,...
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3 votes
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Is there Kuiper belt/Oort cloud like structure in gas giants?

The gravitational region around the planets isn't hard to calculate, sometimes called the Sphere of Influence, sometimes called the Hill Sphere. They're calculated differently but they define pretty ...
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  • 22.9k
2 votes
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Observed data: Why so many MPECs about TNOs lately?

This is the result of a new way to investigate the images taken by the PanSTARRS survey, see Weryk et al. 2016. A second batch of new discoveries was issued on July 26. This has been planned for ...
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2 votes
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Which kind of strategy should we take to discover Planet 9 and other KBOs?

This question already discusses the challenges of discovering planet 9 The main problem of the hypothetical planet 9 as compared to Sedna and 2012 VP113 is: Sedna and 2012 VP113 have orbits that ...
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  • 287
2 votes
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Are there actual asteroids in the Oort cloud?

Tl;Dr: It is a matter of consideration if you want to call Kuiper belt bodies/Oort cloud bodies "asteroids" or not. Long answer: The Oort cloud defines the cosmographic boundary of the Solar ...
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  • 3,226
2 votes

Is the mass of Kuiper belt dominated by large objects?

It depends on what you call large. There may be hundreds of thousands of icy bodies larger than 100 km (62 miles) and an estimated trillion or more comets within the Kuiper Belt. But the total mass of ...
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