I'm trying to envision a human colony on a planet called Imot, which orbits in the habitable zone of a Red Dwarf star. Imot is similar to Earth though somewhat larger, and has strong magnetic field to protect itself from the stellar wind. Its year lasts 20 days and has a large moon that orbits it on a distance of 100,000 km.

My problems are the flares, the parent star flares nearly every day and some of the flares are very nasty. Since the planet's obliquity is 90 degrees there is no place to hide.

How to protect human colonists from the flares?


As the Imot's obliquity is 90 degrees, it is not and cannot be tidally locked. See my question answers on astronomy and this video especially.

Yes: It has a companion planet or an excessively large moon, with the two bodies orbiting their common center of mass (much like Earth and Moon). They may be tisdally-locked to each other, but they cannot be tidally-locked to their star.

If some kind of warning system is possible human's could temporarily go to a shelter.

Crops are the other problem, they need to be outside.

  • $\begingroup$ I suspect that the moon would not work. Check your Hill Sphere size. $\endgroup$ – JDługosz Nov 12 '16 at 11:22
  • $\begingroup$ @JDługosz I'm not good at Math but I run simulations with universesandbox.com & en.spaceengine.org and it works without a problem. However the moon has to be much closer then our moon, at 100,000 km Ganymede is stable. At 200,000 km Ganymede breaks free very quickly due to perturbations from the other planets. $\endgroup$ – Soba Nov 12 '16 at 11:29
  • $\begingroup$ I don't think the Cat would ever wear flares. Oh, not that Red Dwarf! $\endgroup$ – CJ Dennis Mar 8 '18 at 0:42

There are a Few Options

A) Move around the planet

enter image description here

While this is the least energy efficient - and a somewhat strange - option, you could move your colony around the planet throughout the year in such a way that they are always on the border between the light and dark parts of the planet. They will get a decent amount of light, comparable to sunrise or sunset, but they will be least affected by solar flares.

This would be most efficient if your colony orbits the planet, or if there is an ocean large enough for a floating colony to navigate the seas throughout the year.

B) Settle underground

See this poster from National Geographic for a visual of what a colony might look like

Lava tubes are cave-like conduits formed underground by cooled, hardened lava after molten rock has flowed through. Scientists say the ones on Mars may be significantly larger than those on Earth. The interiors of the Martian tubes, hidden under dozens of feet of solid rock, are protected from cosmic and solar radiation and fluctuating temperatures on the harsh, dusty surface.

If your future colonist analyze the structures below the surface, using something like this, they may find lava tubes perfectly suited for colonies! And if not - they can still dig to a reasonable depth where radiation won't cause problems.

C) Use radiation shielding

Scientists have proposed numerous strategies that would allow your colonists to build above ground - it just might not be pretty. Consider coating all structures in six feet of soil, or adding thick metal plates - it doesn't take a lot to match the protection an atmosphere gives once you have a magnetic field - and voila! Earth-like protection.

D) Use artificial magnetic fields

If your colonists want to live above ground, in the sunlight, without thick plating, and stay in once place, this is your final option. It is plausible that by the time your colonists arrive, humans will have figured out how to make cheap magnetic fields - which, if strong enough, are all you need to keep out the radiation from flares.
Also note that if you want croups outside the colony, on the surface, this method would work best.


The people are easy, dig down. Not all that different than tornado country. The people can either live in tunnels dug underground or surface buildings covered in regolith, rock actually makes a fairly effective radiation shield. Alternatively if the flares give some warning they could build flare shelters similar to tornado shelters and just run to them whenever the siren goes off. Note shielded vehicles will be very important in this scenario since they will put them away from shelter whenever used.

compare this list of how much material is needed to halve incoming radiation. enter image description here

Protecting the crops is hard because they need sunlight, so they have to be exposed to the sun. You have two options here. direct and indirect sunlight.

You can use solar panels on the surface to power underground lights for growing fields, you will however need a lot more solar panel acreage than growing acreage. It is also a very material intensive form of growing, since all your production needs to be dug out. you could do this with shielded(lead lined) surface buildings but your acreage gets even bigger, but your cost will be lower.

The alternative here is surface greenhouses with collapsible/retractable shielding, likely some kind of lead shutter that closes over the greenhouse, this of course works better with an early warning system otherwise your plants are still getting a dose. In both cases hydroponics or some other high density growing system will help make it more efficient. The crops use the stars light to grow making this the most energy efficient method.

this site will help with any shielding calculations.

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    $\begingroup$ Can you explain how it is easy to protect the people? As it stands, this is more of a comment. $\endgroup$ – HDE 226868 Nov 12 '16 at 3:29
  • $\begingroup$ This does not provide an answer to the question. To critique or request clarification from an author, leave a comment below their post. - From Review $\endgroup$ – a4android Nov 12 '16 at 3:48
  • $\begingroup$ I half get what your answer is about, but more details and reasons would help. What are the problems with protecting crops? $\endgroup$ – a4android Nov 12 '16 at 7:52
  • $\begingroup$ @a4android They must be outside, if I put them in a cave the ecosystem would be very slow. Maybe a greenhouse could help. As for the people they could hide if there some kind of warning system that could predict the flare. $\endgroup$ – Soba Nov 12 '16 at 11:32

How about dig a cave/tunnel a safe distance underground? Possibly combining that with an EM generator if needed.

More details requested:

This is an example of what I am talking about. Here where I live there is a frost line, which is basically anything deeper than roughly 4' down will never freeze. Some areas of the world its a bit deeper.

The same concept applies here. The surface will be bombarded, but it will only penetrate the ground to a certain depth. Add a bit of margin for error, and dig a tunnel deeper and you will be safe.

Not knowing the exact impact force, intensity, composition of the planet, and etc means a depth can only be guested at. Depending on all of these conditions a tunnel less than 30 feet deep might be fine.


The planet is likely to be tidally-locked, which would create a dichotomy between the hemispheres. That could make it an "Eyeball planet" (see here). There are several different flavors of Eyeball planets (see here): the best place for life can be along the terminator (in permanent sunset/sunrise) or the illuminated or dark sides depending on the planet's atmosphere and water content (see here for the example of Proxima).

enter image description here

For your planet, people could most easily protect themselves by either moving out of the sunlit side, hiding in caves. Beware also that the science of how flares affect planets is very thin. We really don't know whether they are as dangerous as the news articles suggest. The early Sun had a lot of flares and outbursts but Earth seems to have survived okay. Of course, we don't know what things were like back then.

  • $\begingroup$ The planet obliquity is 90 degrees, the planet can't be tidally locked. $\endgroup$ – Soba Nov 12 '16 at 11:13
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    $\begingroup$ IF you're going hard science this is pretty unrealistic. The timescale for a planet's obliquity to decay is very short for close-in orbits. In order, tides affect: the obliquity, the rotation rate, the orbital eccentricity, then the orbital semimajor axis. Tides would be strong enough in the habitable zone of basically any M stars to cause the obliquity to decay. $\endgroup$ – Sean Raymond Nov 12 '16 at 11:33
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    $\begingroup$ A thought: as the obliquity goes to zero by tides, it can go through a phase when it is excited. So if your planet orbits a relatively massive M star or on the outer parts of the HZ then there could be a phase during which the obliquity is near 90 degrees. $\endgroup$ – Sean Raymond Nov 12 '16 at 11:50
  • $\begingroup$ So even if planet starts with 90 degrees obliquity and has a massive moon to protect it from wobbling , it will still become tidally locked? $\endgroup$ – Soba Nov 12 '16 at 12:00

I don't believe this setting gonna work, in order for the orbit to be 20 days the star has to be 18% of the Sun mass, anything less then 30% of the Sun's mass and the planet becomes tidal Venus https://arxiv.org/abs/1203.5104

I really doubt that planet so close could protect its atmosphere from such flares. Maybe some freakishly strong magnetic field could do it, but that opens another can of worms, with trapping the charged particles like Jupiter And if you plan to wait for red dwarf to calm down, you gonna wait for a long time.

I would go with an Orange dwarf which is somewhat larger 45% of the Sun masses but avoids red dwarf habitability issues.


As long as the magnetic field is strong enough to hold the atmosphere in the face of such heavy bombardment you only have to worry about direct radiation, an Earth-like atmosphere will absorb the bulk of the Gamma, UV and X-rays and a lot of Infrared too but all the Radio and most of the Microwaves are still going to get through to the surface. You need an optically transparent Radio and Microwave absorber, it can absorb the green part of the visible spectrum too because plants don't use that light anyway. It turns out that plastics are good Radio and Microwave blockers/absorbers so thick Perspex on huge "greenhouses" may be enough to shield crops and livestock that can't be sheltered underground from high radiation levels, if you want to follow a sedentary lifestyle model, Zxyrra's Option A, mobile civilisation, is perfectly good too.


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