
Space Is Full of Planets, and Most of Them Don't Even Have Stars - phront
https://www.forbes.com/sites/startswithabang/2018/03/13/space-is-full-of-planets-and-most-of-them-dont-even-have-stars/
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perl4ever
Based on the inverse correlation between star size and frequency, this doesn't
surprise me at all.

It seems like there is an obvious further inference to make - people have
debated whether life originated on earth or not. Given that the vast majority
of planets do not have a star, and given that we know there are chemotrophs
even on Earth that prove it is possible to live without a sun, it seems
overwhelmingly likely that life came from one of these rogue planets that was
large enough to retain enough heat underground for the evolution of life over
the first few billion years of the universe. That would also neatly explain
why evidence of life appeared so soon after the Earth became solid.

~~~
hyperpallium
If you're a fan of Moore's Law and the Singularity, you'll love the reasoning
of backtrapolating the exponentially increasing complexity of life over
time... to get 0 well before the formation of the earth
[https://www.technologyreview.com/s/513781/moores-law-and-
the...](https://www.technologyreview.com/s/513781/moores-law-and-the-origin-
of-life/)

~~~
m_mueller
What about Fermi's paradox though? I mean, where _is_ everyone?

~~~
throwaway7312
Uncontacted tribes in the Amazon likely wonder the same thing. It's such a big
Earth, yet only a few hundred humans are known to exist.

Why are there no other detectable signs of human life, like smoke signals,
territory markers, or emissaries from any more but a handful of other tribes?
Surely if advanced humans existed, they would have contacted these tribes by
now, to share technology, discoveries, and medicine. Yet they haven't.

How can the whole planet be so... silent?

~~~
chongli
If they're not aware of any other humans (let alone all the cities out there)
then they're likely not aware of the actual size of the earth. Perhaps they
only consider it in terms of the surrounding territory.

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itronitron
Interstellar travel now seems a lot more hazardous than it did before. To
quote one of my TAs in college, "it's the stuff you can't see that gets you"
...

~~~
lev99
The article states that planets may outnumber stars 100,000 to 1.

The Milky Way has 4E^11 stars.

It has an upper estimate of 4E^16 planets.

It has a lowest estimate diameter of 100kly.

It has an estimated thickness of 2kly.

It's lower estimate volume is 63,000 kly^2.

\-----------------------------

If planets are uniformly disrupted (they surely aren't), there are ~17 planets
in every cubic light year. Sure, that's a hazard.

~~~
nabla9
> ~17 planets in every cubic light year.

The change of hitting one while traveling one light year is in the order of
10e-16.

~~~
varjag
About the same as getting shot while drowning in bathtub stricken by
lightning?

~~~
gnarbarian
That's how my uncle died.

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afterburner
New 4x games should now include plenty of planets between star systems. Cold
and still, but potential mining boons and refueling bases.

~~~
ianai
And I demand Star Trek TNG be reran with scientifically appropriate visits to
rogue planets. /s

~~~
lebrad
The Founder's homeworld on Deep Space Nine was a rogue planet

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drdeadringer
I can't help but think of how the various Star Trek series handled rogue
planets... and then later on how IRL science delved into rogue planets as more
of a reality than previously realized.

~~~
beamatronic
Could you provide an example? I don’t recall such an episode.

~~~
baxtr
“It is unclear how plant life could survive on Dakala. One scene, however,
shows the surface covered in the dim light of a nearby star, perhaps supplying
enough energy for some form of photosynthesis. Another theory, from the Star
Trek Encyclopedia (4th ed., vol. 1, p. 177), is that the plant and animal life
was supported by the surface heat from volcanic vents.“

From [http://memory-alpha.wikia.com/wiki/Dakala](http://memory-
alpha.wikia.com/wiki/Dakala)

~~~
flomo
FYI, you're just quoting some technobabble.

Back in reality there were popular magazines like _Discover_ that would have
flashy covers about things like _ROUGE PLANETS!_ Mostly just sensationalism.

Some semi-unemployed Hollywood writer would be paging through these while
smoking out and get inspiration for a script. That is Star Trek's scientific
insight.

And I'm a trek fan. OP probably just doesn't know a lot of this stuff was
"ripped from the headlines" (of popular science magazines).

~~~
baxtr
Yes, you’re right. I think it’s fun though :-) sci-fi is by its nature just
technobabble, see the annoying protomolecule stuff in “The Expanse”

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wrycoder
If this is recent information, how does it bear on dark matter, i.e. machos?
An excellent read, btw.

~~~
antognini
This is not super recent information. There have been estimates that there are
about as many rogue planets as stars since 2011. There's still a pretty wide
variation in the estimate of the number of rogue planets from study to study,
so the frequency is pretty uncertain. But even if the numbers are on the high
side, it's not anywhere close to explain dark matter. Supposing that there are
10 Jupiter mass planets for every star, that would only increase the luminous
mass of the Galaxy by 1%. Dark matter accounts for more than ten times the
mass of the Galaxy as luminous matter.

~~~
SubiculumCode
Not a physicist. If napkin calculation goes, that's 1000 Jupiters per star. Is
that really improbable? There is a lot of space outside of solar system radii.

~~~
antognini
I think it would require more like 10,000 Jupiters per star to account for
dark matter in the Galaxy. The issue is that these microlensing surveys put an
upper bound on the number of rogue Jupiters that can be floating around and
this bound is much less than 10,000 per star.

~~~
Eesais2e
Can microlensing account for the whole continuum of black hole sizes that
might be floating around in the galactic halo?

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kamaal
This sort of space real estate is the biggest hindrance to developing long
term interstellar traveling tech.

With so many asteroids and planets lying around. There is no real motivation
to travel very far distances for resources. Once you start mining the first
set of asteroids and settling your race in space. You could grow organically,
and at some point mine a terrestrial planet. At that point you have so many
resources at your disposal it doesn't really make much sense to move out to
very large distances unless for science or your population is just multiplying
beyond control.

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senectus1
I wonder what happens to the planets in the solar system when a rogue planets
gets sucked into the star (sun) ?

I mean, yeah it'd be bad if a rogue planet smashed into us, or even came close
enough to mess with our gravitational pool (or the moons). but I imagine if an
earth sized or bigger slammed into the sun, that we'd feel the effects of
this.

massive solar flare roasting our planet alive? a shower of ejecta from the
collision that we pass through? it changes the mass of the sun in a
significant way that changes the pull it has on the planets around it?

~~~
ChuckMcM
Napkin math (aka pure speculation) suggests that unless the rogue planet hit
the star directly and at an angle that could send ejecta our way, the results
would be more observational than catastrophic.

The Earth is roughly 333,000 times less massive than the Sun. Think of it this
way, If an asteroid hit the Earth that was, in relative terms, the size of the
earth relative to the sun, it would be about 1/3 the size of Ceres. Everything
on Earth would die but the other planets would probably not notice.

Given that the surface of the Sun can be treated, to a first approximation, as
a fluid, an impact that was perpendicular to the surface would likely have the
same characteristics of a milk drop. Which is to say a large wave would race
away from the impact point and the collapsing of that wave in would eject a
bit of coronal mass roughly equal to 1% of the mass of the impactor (note this
makes a big, and unsupported, assumption about the viscosity of the solar
corona.)

The only scary bit comes if the rogue planet enters the solar system slightly
off the plane of the ecliptic and hits the Sun in a glancing blow. In such a
scenario it could transfer a huge amount of momentum into the coronal mass
which would then immediately begin to head away from the Sun. If the Earth
were in the path of that mass it would probably wipe everything out after
blowing off our atmosphere.

This wouldn't be good for the rogue planet either, which would probably enter
a hyperbolic orbit and shoot away from the solar system on a new trajectory.
In the unfortunate circumstance that this "coronal braking maneuver" was
sufficient to slow the planet enough to be captured by the Sun, the remaining
planets would get to witness periodic brushes with the Sun by the rogue planet
until it had lost enough energy to fall into the Sun.

That would be mitigated if the orbit it fell into pulled it by Jupiter or
another large planet which, by virtue of its gravity circularize the orbit
sufficiently that it would not come near the corona on future orbits.

~~~
cobbzilla
Let's say the rogue planet is a massive, super-cold planet. How big and how
cold would it have to be to lower the Sun's energy output just enough to
trigger a "Snowball Earth" scenario? Assume a direct hit.

~~~
ChuckMcM
I think the only way this works is if the planet _doesn 't_ hit the Sun. One
could imagine a scenario (but the orbital mechanics don't work out) where a
massive rogue planet enters into the solar system and interposes itself
between the Earth and Sun, thus shading the Earth and dropping its temperature
the required amount. Sort of like a month long solar eclipse or something. But
at that mass it's probably pulling Earth out of its orbit so that scenario is
not really very plausible.

If it hits the Sun, it really doesn't matter how cold or how massive it is (up
until it becomes a brown dwarf at which point we're talking binary star
interaction levels of mass).

The thing is that the Sun is really spectacularly huge. You could fit over a
million earth size planets inside of it. And it is a run away fusion reactor
so it is kind of like throwing frozen beer cans into a 500 acre California
wildfire. Very little effect on the fire (although any embedded Hot Shot
firefighters will appreciate your effort).

But things are even easier than actually hitting the Sun in this case. If
you're trying to just screw up the Earth, any rogue planet that flew through
the Solar system and pulled earth more than about 6 - 8% off its existing
orbit should completely wreck the climate. If you were a fiction writer you'd
want it to be bad enough that people could survive long enough to write a
story about it or course.

Generally though any astronomical mass that would nominally qualify as a
planet flying within a million miles of the Earth is going to likely trigger
an extinction level event. Especially if it is off the ecliptic by some
amount.

~~~
restalis
_" where a massive rogue planet enters into the solar system and interposes
itself between the Earth and Sun, thus shading the Earth and dropping its
temperature the required amount. Sort of like a month long solar eclipse"_

For our planet's distance from the sun, I have a hard time imagining how
anything without self propulsion could maintain a stable orbital position to
cast a shade over us for a long enough period (e.g. a month).

------
lmm
Has the IAU come around to a sensible definition of "planet", or are these
officially non-planets?

~~~
doikor
Current definition requires the object to be orbiting the Sun (and only the
Sun not other stars) so by IAU definition these are not planets.

> A "planet" is a celestial body that: (a) is in orbit around the Sun, (b) has
> sufficient mass for its self-gravity to overcome rigid body forces so that
> it assumes a hydrostatic equilibrium (nearly round) shape, and (c) has
> cleared the neighbourhood around its orbit.

> A "dwarf planet" is a celestial body that: (a) is in orbit around the Sun,
> (b) has sufficient mass for its self-gravity to overcome rigid body forces
> so that it assumes a hydrostatic equilibrium (nearly round) shape, (c) has
> not cleared the neighbourhood around its orbit, and (d) is not a satellite.

> All other objects, except satellites, orbiting the Sun shall be referred to
> collectively as "Small Solar System Bodies".

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ataturk
Why would we visit forbes.com to learn about astronomy?

~~~
pferde
We would not, because with javascript disabled, it only displays blank page.
:)

~~~
swebs
Same. Here's an archive:

[http://archive.li/TUHro](http://archive.li/TUHro)

It would be great if HN had an auto-archive feature now that more people are
becoming privacy conscious.

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dandr01d
[deleted]

~~~
King-Aaron
Roger

