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46 votes
Accepted

How is it possible that we haven't discovered anything in the Oort cloud yet?

It's not very surprising that no Oort Cloud objects have been detected via occultations. They're extremely rare, even for our most advanced space-based observatories. According to Ofek & Nakar ...
HDE 226868's user avatar
  • 36.6k
28 votes

Does the Oort cloud have any large holes in it and if not does this mean nothing large has entered the solar system for a long time?

The Oort Cloud has not been directly observed. The Oort cloud is still theoretical. We're pretty sure it's there, but we don't have direct evidence. The objects that make it up are too small, too dark,...
Darth Pseudonym's user avatar
20 votes

"Tidally locked" Oort Cloud object

The question in the title and the body are different. There are no tidally locked objects in the Oort cloud. The sun's tidal forces at that distance are not sufficient to lock an object's rotation. ...
James K's user avatar
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15 votes
Accepted

Scientific evidence against CMB originating from “Oort Soup”?

The idea that belts or spheres of dust might be responsible for (some) microwave emission is not crazy. Indeed we know that dust does emit microwaves and indeed, the contribution of such dust has to ...
ProfRob's user avatar
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14 votes
Accepted

Does Halley's Comet travel past the outer bounds of the Oort Cloud?

No. Halley's Comet has an aphelion of 35 AU, which is far less than the believed boundaries of the Oort cloud. Any object on an elliptical orbit with a perihelion of 0.6 AU and an aphelion of 2,000 ...
notovny's user avatar
  • 4,788
11 votes

What reason is there to doubt the existence of the hypothesised planet Tyche in the far distant solar system?

Several months after the accepted answer was posted: In 2014, NASA announced that the WISE survey had ruled out any object with Tyche's characteristics, indicating that Tyche as hypothesized by ...
Keith Thompson's user avatar
11 votes
Accepted

What's the reason for the hollow region in Oort cloud?

This is a fascinating question and I do not think there is yet an absolutely agreed consensus even on the likely distribution of the Oort cloud objects and it isn't clear to me how the pictures you ...
ProfRob's user avatar
  • 153k
9 votes
Accepted

Could a black hole pass quiescently through the Oort cloud?

An approach would be to use the Bondi-Hoyle (B-H) accretion rate and then assume that some large fraction of the gravitational potential energy was radiated from the innermost stable circular orbit (...
ProfRob's user avatar
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9 votes
Accepted

"Tidally locked" Oort Cloud object

Suppose you orbit with period $P$, and have a angular velocity $\omega$ randomly chosen (let's start with everything aligned in a plane orthogonal to spin too). Then to keep your face pointed towards ...
Anders Sandberg's user avatar
8 votes
Accepted

Why didn't passing stars destroy the Oort cloud?

The Oort cloud is disturbed. This is thought to be one of the ways we can get long period comets. It is also depleted of objects over time and it is likely that only a fraction of the original objects ...
ProfRob's user avatar
  • 153k
8 votes

Does Halley's Comet travel past the outer bounds of the Oort Cloud?

Without knowing anything specific about this comet, you can use Kepler's third law to get an idea whether this could be the case. It says that the cube of the semi-major axis is proportional to the ...
Paŭlo Ebermann's user avatar
7 votes
Accepted

If the Oort cloud has billions of objects larger than 20 km, then why do we have so few comets?

Most Oort cloud objects stay in the Oort cloud, and we never see them. Comets don't last long. A comet is made of a mixture of ices and dust. A comet that enters the inner solar system has one of a ...
James K's user avatar
  • 123k
7 votes
Accepted

How far out can the sun keep celestial objects revolving?

The suns gravitational pull extends unlimitedly far and, if the universe were otherwise empty, a body could orbit it (very slowly) at unlimited distance. However, the universe is NOT otherwise empty....
Steve Linton's user avatar
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7 votes
Accepted

Would it be practical to map out the Kuiper Belt and Oort Cloud via Radar?

An answer can perhaps be given in terms of the capabilities of the now defunct Arecibo radar facility. This was the most powerful radar system, as summarised in Venditti et al. (2023). Arecibo had a ...
ProfRob's user avatar
  • 153k
6 votes

Could more objects from the Oort cloud with highly elliptical orbits be discovered in the future?

Although, there hasn't been a confirmed direct observations of the Oort cloud, it is confirmed to be the home of long period comets. Some notable examples include C/1999 F1 (Catalina), C/2006 P1 (...
Nilay Ghosh's user avatar
  • 4,462
6 votes

Could more objects from the Oort cloud with highly elliptical orbits be discovered in the future?

If you consider "objects" to include comets, then yes, they will be, probably within a few months. Extremely long-period comets are continually being discovered by various space telescopes ...
notovny's user avatar
  • 4,788
6 votes

Does the Oort Cloud lose mass with time?

The Oort cloud objects are only very loosely bound to the Sun. That is, their total energy (kinetic plus gravitational potential) is only just negative. That means you only need a slightly positive ...
ProfRob's user avatar
  • 153k
6 votes

Does the Oort cloud have any large holes in it and if not does this mean nothing large has entered the solar system for a long time?

Maybe, but not likely. Let's look at something similar - the Asteroid Belt. The Asteroid Belt between Mars and Jupiter (not really "between" since some of it extends past Jupiter, and ...
MikeP's user avatar
  • 161
4 votes
Accepted

Outer Limit of Oort Cloud

Here is a link to a list of close passages between the Sun and nearby stars calculated to have happened in the past few million years or to happen in the future few million years. All of them ...
M. A. Golding's user avatar
4 votes

What is the density of the solar system per cubic light second outside the Jupiter ecliptic?

I assume you want density expressed in units of average mass in kg per cubic light second. An ecliptic plane is infinitely thin, so we might assume this is irrelevant to the question. Perhaps you ...
Connor Garcia's user avatar
  • 16.3k
4 votes

Do hypervelocity stars have Oort clouds?

There is no problem with orbiting a star that moves very fast. Remember that space is mostly empty, so there is nothing like air resistance or friction that would tend to deform the orbit. Stars that ...
Anders Sandberg's user avatar
4 votes

Oort cloud shape

The Oort cloud objects are thought to have a spherical distribution because the very long period comets that enter the inner Solar System do so from random directions. Why is their distribution ...
ProfRob's user avatar
  • 153k
4 votes
Accepted

Can we measure comets in a similar way to exoplanets?

The thing about detecting exoplanets by eclipses is that the eclipses are repeatable. You have the same star, whose light curve dims in the same way with each eclipse, which gives you information ...
rob's user avatar
  • 1,021
4 votes
Accepted

Lack of objects between heliopause and Oort cloud?

There is no "gap" other than an apparent one caused by the use of logarithmic axes. The density of Oort cloud objects is thought to decrease with increasing distance from the Sun. However, ...
ProfRob's user avatar
  • 153k
3 votes

What is the word for space that is in the solar system, but outside the heliopause?

There doesn't seem to be such a word. Interstellar space within the Solar System is still just interstellar space. There doesn't seem to be a demand for the word you're looking for either. We ...
Sir Cumference's user avatar
3 votes
Accepted

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 ...
userLTK's user avatar
  • 24.1k
2 votes

What wavelengths are used to search for distant solar system objects like KBOs and Oort cloud members?

Virtually all KBO searches use mosaic CCD cameras operating in the visible part of the spectrum, usually with a red filter like SDSS-r' (centered at approx. 622nm SDSS filters) on big (~4m telescopes)....
astrosnapper's user avatar
  • 8,357
2 votes

Do hypervelocity stars have Oort clouds?

Hypervelocity stars are moving at up to 1000 $km/s$ relative to the general movement of stars in their part of the galaxy (which is typically 100 $km/s$ relative to one another or the galactic centre)....
Steve Linton's user avatar
  • 10.3k
2 votes
Accepted

The Kuiper Belt and Oort cloud

How come the comets and asteroids in the Kuiper belt and Oort cloud are kept in a gravitational field and they don't get pushed and pulled by the planets around them? Basically, they're so far away ...
Glorfindel's user avatar
  • 4,790
2 votes
Accepted

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 ...
Nilay Ghosh's user avatar
  • 4,462

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