# Tag Info

16

First of all I'll start with a few ideas: Baryonic Matter: Baryons are elementary particles made up of 3 quarks. This includes protons and neutrons, and the term baryonic matter refers to matter made of baryons, such as atoms. Examples of non-baryonic matter includes neutrinos, free electrons and other exotic matter. Things like planets, stars, dust, etc. ...

12

There is no "orbital path" detected, that's why it is a "free-floating planet". There is no radial velocity mesured, but the informations given by its kinematic location show that it belongs to the beta Pictoris group, that is a stellar group. For more dirty details, have a look at the submitted paper on PSO J318.5-22: http://arxiv.org/abs/1310.0457 ...

12

It would be much better for Earth if the impactor hit the moon... In this Worldbuilding answer, I used a paper on ejecta kinematics to do calculations for ejecta velocity upon impact. Without going into too much detail here, much of the ejecta from a large impactor would not exceed the moon's escape velocity of 2.38 km/s. You can examine Figure 7 from the ...

11

Since Andromeda is already visible to the naked eye, to a civilization located at half the distance from the Milky Way, Andromeda would be still be visible. Its total brightness would be four times higher, but since its area would grow by the same factor, its surface brightness would stay constant. The Milky is less bright by a factor of ~2.5, but also ...

11

Rogue planets have been discovered by infra-red imaging because planets are hot when they form. Here's a list of a few. There's 2 types of Rogue planets. One is failed stars. condensing pockets of gas and dust that form similar to how our solar-system formed, but that are too small to form stars. Source. The 2nd type is planets that escape from a ...

9

The Sun will not become a supernova, it will never explode. A star must have about 8 times more mass than the Sun in order to cause a supernova explosion. When it starts to fuse helium, the Sun will become a red giant and expand out to about Earth's orbit and throw out gas to form a beautiful so called planetary nebula. Mercury, Venus and maybe Earth will be ...

9

Planets, if any in that star system, would be visible to the naked eye, the way you can see Mercury, Venus, Mars, Jupiter, Saturn and Uranus in our system. On a virtually empty sky, they would draw that much more attention. Of course, if you had a Moon (or several moons), that would be visible too. Very rarely and briefly, asteroids passing by very close ...

9

The most successful methods are by gravitational microlensing and direct observation in the infrared or far infrared. The transit method doesn't work well for rogue planets, because usually at least three transits are needed to confirm a planet.

9

The minimum mass of a "planet" forming from a gas cloud (definitions of what a planet is are rather slippery, and some would say this is not a planet at all) is not determined by the time available. The collapse process is rapid - less than a million years. There is a minimum mass though, and what you are referring to is something known as the fragmentation ...

8

The closest body we currently know to exist is Proxima Centauri which is part of the Alpha Centauri system at about 4.25 light years away. There may be rogue planets that are closer but we haven't been able to detect any. Objects down to brown dwarf size that are closer than Alpha Centauri have not been found by extensive surveys. Here is a list of close ...

8

The Moon orbits the Earth from $\approx$ 380000 km, but its radius is only $\approx$ 3500 km. The sky has 41253 sq degrees, and the Moon covers only $\approx$ 0.25 sq degree from it. Thus, the probability that an incoming meteor is blocked by the Moon, is $\approx$ 1:160000. Thus, the Moon is totally unfeasible to protect us from anything. The debris would ...

7

Astronomers call the type of object you are describing-- one that condensed from an isolated nebula but was too small to undergo hydrogen fusion-- a sub-brown dwarf. They are quite difficult to detect as you might imagine, since they "shine" only with the heat of their formation, very dimly in the infrared (the Wikipedia page refers to some that orbit other ...

7

Yes, they would experience gravitational attraction. It would take a long time for them to collide... the formula (derived here and shown here) is: $$t = \frac{\pi}{2} \sqrt{\frac{d^3}{2G(m_1+m_2)}}$$ where $d$ is the initial distance between the two planets of mass $m_1$ and $m_2$ and $G$ is the Gravitational constant. This gives a time of about $10^{23}$ ...

7

I don't know the first use of the time rogue planet or the first use of such planets called something else. But if science fiction is anything to go by, rogue planets are as thick as fleas in interstellar space and they are all heading for Earth's solar system. The Wanderer (1965) by Friz Leiber involves a planet entering the solar system and causing ...

6

You can see the Andromeda galaxy with a naked eye, even with some level of light pollution. So if the star you are asking about would be even closer to Andromeda, you would see at least that galaxy. There are some other galaxies that can be seen from Earth with a naked eye or with binoculars, so sky of such a lonely planet would still have some night lights ...

6

Arguably, "rogue planets" have already been discovered by direct imaging. Giant planets when first formed are big and hot. They radiate their own light, mostly in the infrared. So young isolated planets can be seen directly. There have been various claims in the literature that objects as small as a few Jupiter masses have been identified in young star ...

6

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 resurfaced during Pluto's perihelion. Your theory cannot account for the very young age of the surface. Next capture of a rogue planet is not easy. It would ...

6

Intergalactic planets have never been observed. They're too small and it's too great a distance, but intergalactic stars have, and if stars can be ejected from a galaxy, planets can to. The orbital mechanics is the same for both. The escape velocity of the galaxy is impressive. For solar-systems, where most of the mass is in the star in the center, the ...

6

It would be more accurate to call them surveys than studies. A study looks at an object in detail. A survey counts and categorizes objects. Rogue planets are enormously difficult to see, and only a few very large ones have actually been observed directly. For the largest rogue planets, it's unclear if they actually are ejected planets as opposed to ...

6

While near encounters with supermassive black holes are bad for the stability of solar systems [citation needed?], many intergalactic stars become intergalactic without a close encounter. They are part of streams and tidal tails that emerge when galaxies or globular clusters get tidally disrupted by another galaxy. Still, even while encounters with black ...

5

Giant planets when first formed are big and hot. They radiate their own light, mostly in the infrared. So young isolated planets can be seen directly. There have been various claims in the literature that objects as small as a few Jupiter masses have been identified in young star forming regions. See various papers by the IAC brown dwarf research group ...

5

On the numbers Rogue planets are thought to be more abundant than stars in the milky-way and depending on where you make the cut-off, rogue dwarf-planets for example, are expected to enormously outnumber the number of stars. older article quoting the MOA survey. This article - OGLE survey, or, Portland's Optical Gravitational Lensing Experiment estimates:...

5

Using microlensing the MOA (Microlensing Objects in Astrophysics), OGLE (Optical Gravitational Lensing Experiment) groups have found many free-floating planets. The stars, free floating planets etc are all moving around the center of our galaxy. They are moving at different speeds, so very occasionally a foreground object passes through the direct line of ...

4

This rogue planet orbits the center of the galaxy Milk Way, (or rather, the center of mass of the system PSO J318 - rest of MW, wherever it is localised) just like the Sun and the other stars. But I think the details of this orbit, that is eccentricity, period, inclination, etc are not well known. If PSO J318.5-22 be confirmed as a Beta Pictoris association ...

4

The processes by which planets can be removed from their parent stars are discussed in some detail by Davies et al. (2014). These include direct ejection through interactions with other stars in dense birth environments; the ejection of planets due to planet-planet interactions, again usually taking place fairly early in a star's life; the later ejection of ...

4

1) this question has no real answer as it depends on the reference frame being used. It is very unlikely that they will be stationary except in their own reference frame. rephrased 1) In theory their paths can be calculated precisely if you know their speed and the positions and motions of all other bodies (also gas and dust clouds) that might influence ...

4

At the moment there is basically only one way. That is to associate the planetary-sized object with a cluster of stars or moving group of stars of known age. That's basically it. If the planetary-sized object really can't be associated with another object, then only limits can be placed on its age by comparing it's luminosity to theoretical planet cooling ...

4

The Wikipedia article on voids is pretty good (though IMO unusually awkwardly written.) The key thing is that voids are not empty, they are just large volumes which have a lower density (typically around 10% of average) compared with the rest of the universe. These low density areas still contain stars and galaxies, just fewer of them and the galaxies they ...

4

This is considered very unlikely. It is actually very difficult for things to be captured into orbits. They pick up speed as they fall in towards the larger object, and that's automatically enough speed to carry them back out. Capture either requires dust and gas to slow the body down, or very lucky gravitational interaction with a third object. This has ...

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