First Earth-sized exoplanet found

[Nephew Twiddleton]

You don't need the magnetic field to block radiation, even in interplanetary space the radiation level is barely high enough to be dangerous (can't find the specific level, but NASA was running rat tests to see if they could actually cause problems or not with the radiation levels involved), standing on a planet cuts it in half (less whatever the local rocks put out) and an atmosphere (which is the biggest part of Earth's shield) drops it even farther.

IIRC a magnetic field is important in limiting atmosphere loss from solar wind, but weaker solar winds or increased vulcanism would balance that.

Your specifics are what I was thinking of- the thought just kinda jumped from point a to c.

Venus and Mars are good examples on either extreme- Mars' atmosphere was mostly stripped off because it lost core activity and vulcanism, even though it is further away from the sun and rotates at almost the same rate as Earth.

Venus is closer and rotates slower than the Earth, but maintains its atmosphere at very dense levels due to a highly active core, even though it is closer in size, but slightly smaller than Earth.

Actually, Venus could be a good example of how temperatures on Gliese 581 g might be more stable than we think- it's a little larger than Earth and would have a denser atmosphere resulting from extra gravity- if it has a other appropriate factors, the night time side might not be that cold, and the day time side might not be too hot. Naturally, we would have to study more either way, and feasible interstellar travel would help, since we only have 4 examples here that don't necessarily help us figure out all the needed factors for maintaining an atmosphere with stable temperatures.

If we do manage to detect such an atmosphere on Gl 581 g, we still probably wouldn't know much about its core activity. We could assume it's very active, but perhaps there could be some other factor at play.

I think that sleepiness is clouding my thoughts

[Mesozoic Mister Nigel]

Would you like some blankets?

We have this lovely "fire water".

Of course, it's equally likely that they'll do it to us.  We'd have no way of knowing if a ship was on its way here until they started to slow down.

At first I thought this was the coolest thing ever, and it could be like Star Trek.

And then I realized. There are humans on this planet. And then I had a sad.

There is no reason to believe that aliens will be any more advanced or civilized than we are.

After all, keep Roswell in mind.  They build the kind of ships that crash.  We can do THAT.

That only happened because the helmsman was their equivalent of Welsh.

'
GOD    FUCKING     DAMMIT   

It is because they are anthropologists from the future.

[Freeky]

You don't need the magnetic field to block radiation, even in interplanetary space the radiation level is barely high enough to be dangerous (can't find the specific level, but NASA was running rat tests to see if they could actually cause problems or not with the radiation levels involved), standing on a planet cuts it in half (less whatever the local rocks put out) and an atmosphere (which is the biggest part of Earth's shield) drops it even farther.

IIRC a magnetic field is important in limiting atmosphere loss from solar wind, but weaker solar winds or increased vulcanism would balance that.

This is patently bullshit.

Hi Dr. Stern:

   I hope you can help me. I was just checking out your webpage and a question regarding the earth's Van Allen belts and solar flares/solar winds. I read that the earth's magnetic field has actually weakened by about 7% and field's actual total energy measured is less by 14% (since 1829). What is the impact of this weakening on the Van Allen Belts and the earth's Magnetosphere?

   If solar flare activity increases (e.g. second-biggest geomagnetic storm ever measured hit the earth about a week ago) and the earth's magnetic field weakens, what impacts would we observe inside the atmosphere? Higher radiation exposure for folks on planes? Greater disruptions with electrical grids and radio transmissions? What's projected in the long term?

   Can you recommend any websites that "a non-scientist lay person" might be able to read up on this. I guess the late August solar flare activity had nothing to do with the New York blackout (it occurred 2 weeks earlier in August).
Reply

   When discussing risks and dangers from radiation in space, you should really distinguish two kinds of radiation:

     (1)     Trapped radiation, e.g. Van Allen Belt
     (2)     Energetic ions emitted by solar flares.

(1)         Trapped radiation is governed by the geomagnetic field. If you are below the belt (as in the international space station) or elsewhere outside its intense part, you should have nothing to worry about. It could well be that the belt is now weaker than in the time of Gauss, 160 years ago, but that does not really change the preceding statement. These ions have about 50 MeV.

(2)         Solar flares release unpredictable blasts of particles of higher energy, often 500 MeV and up to 10 GeV. In this case, people on the ground are still safe, because the atmosphere has enough thickness to stop the particles, equivalent to something like 4 meters of concrete. See the end of
       http://www.phy6.org/Education/wsolpart.html
If you are in a spacecraft on your way to Mars, that can be dangerous. In Ben Bova's book "Mars" this does happen, and astronauts have to hide in a protected area--behind fuel tanks, probably.

  On Earth, we have an additional shield, the Earth's magnetism, which will deflect all but the highest energies from regions at equatorial and middle latitudes. Jetliners crossing the polar region may perhaps find it useful to fly a little deeper in the atmosphere when the sun emits high-energy particles, and I heard the Concorde carried a radiation alarm.

   The magnetic field would have completely protected the space station in its originally planned orbit, inclined 29 degrees to the equator (latitude of Cape Canaveral). As it happened, this was later increased to about twice as much, to enable Russian launch sites to resupply the station (which turned out quite important after the "Columbia" disaster). Twice each orbit, therefore, the station has relatively weak magnetic protection, near its closest approach to the magnetic poles. I heard a rumor that during the 3 big flare events at the end of October 2003 the astronauts did in fact hide, but that is strictly hearsay which I cannot confirm. The even bigger flare on November 4 did not produce such a radiation surge.

   I am not sure about disruption of power grids, but I think it arises when the auroral electrojets shift to lower latitudes during storms. There are two large electric currents flowing along the auroral zone towards midnight, associated with the polar aurora (or more precisely, with the electric currents which produce big aurora; see in "Exploration of the Earth's Magnetosphere.") Like any electric currents, they produce a magnetic field which can be observed on the ground, and which changes fairly irregularly.

   When they move equatorwards, into more inhabited regions (and out of them again), the changing magnetic field induces electric currents in the high voltage networks there. The induction is slow, so the transformers of the grid, configured to impede currents of 60 or 50 cycles/second, see essentially a DC current, to which they offer it no significant impedance, allowing it to grow big. Such a current can burn out transformers, unless appropriate circuit breakers are tripped in time. I don't know how serious that is: burn-outs happened in 1989, but as far as I know, not recently.

   I am not an expert in disruption of radio. Flares emit X-rays, which modify the ionosphere, adding ionization deeper down. It then can absorb certain frequencies, but I am not sure whether, say, cell phones are affected, or ships and airplanes. I think the frequencies used by communication satellites are high enough to be immune, and of course a lot of land traffic these days uses optical cable. I am not sure about GPS.

   That's about all I know on this subject. Let me know if you find anything more, or anything contrary to what I know.  

http://www.iki.rssi.ru/mirrors/stern/Education/FAQs5.html#q72

http://www.iki.rssi.ru/mirrors/stern/Education/wms1.html

[Nephew Twiddleton]

Good find Freeky!

The radiation (solar/ionic type stuff) might not be a problem for extremophile life. Gl 581 g, if it lacks sufficient geomagnetism, might have radiation loving microbes, maybe some lichen type stuff adapted to the situation, or  a form of highly intelligent space roaches that will invade Earth to eat all our garbage.

Trying to find a downside there...

[Requia ☣]

Freeky: I've read that specific article before, note that it's talking about radiation *in space*, planetside radiation is much lower.  Staying in orbit around a planet with no magnetic field would not be good (though if you already got to the planet, so your spacecraft must be capable of shielding), but planetside there are other shields.  Hell MARS has enough atmosphere to prove adequate shielding.

[Freeky]

Freeky: I've read that specific article before, note that it's talking about radiation *in space*, planetside radiation is much lower.  Staying in orbit around a planet with no magnetic field would not be good (though if you already got to the planet, so your spacecraft must be capable of shielding), but planetside there are other shields.  Hell MARS has enough atmosphere to prove adequate shielding.

Sorry, I was reacting more to

even in interplanetary space the radiation level is barely high enough to be dangerous

than the planetside bits.

[Requia ☣]

Note that 'barely dangerous'; is not the same as not dangerous.  A trip to mars wouldn't kill you right away, but there's an increased risk of cancer (as much as 19% in the high estimates, double a normal non smoker's chance of getting it).

Hmm, I did neglect to account for solar flares, I'm not sure how much radiation those put off, but it doesn't need to be a lot since it all hits at once.

[Jasper]

A much worse problem is posed by very high-energy particles called cosmic rays. These will interact with metals and generate a storm of secondary radiation particles scattered out of the metal atoms. Thus, aluminum and other metal shields can themselves turn lethal when hit by cosmic rays. The only known way to stop cosmic rays safely is by providing a sufficient thickness of matter for them to be slowed down. This can be done either using water or soil. The thickness of water needed is only of the order of several centimeters. The thickness of soil (lunar or earth) needed is roughly six feet (2 meters). Exotic coatings and materials are being developed to serve as lighter shields, but however light these are, the cumulative mass needed to shield a practical human settlement is still enormous. Since these materials require advanced manufacturing processes, they will have to be manufactured on Earth and shipped out - at enormous launch cost.

http://www.adl.gatech.edu/research/tff/radiation_shield.html

Interesting.