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Seven earth-sized planets discovered circling a star 39 light years from Earth

nature.com

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Re: Seven earth-sized planets discovered circling a star 39 light years from Earth

#171

Post by surrey-fringe »

DanBC wrote: post #44
e0m wrote: post #33

To get a spacecraft there it would take: Accelerating at 1g the 1st half, and decelerating at 1g the 2nd half, the traveler would experience 7.3 years of time. For observers it would take 41.8 years at a max speed of 0.998c If you had a near perfect hydrogen -> helium fusion engine, it'd take about 6 million tons of fuel (about the mass of the Pyramids of Egypt or 2,000 Saturn V rockets)

How much fuel would it take to get 6 million tons of fuel off Earth into the interstellar ship?

You have a path from earth to a planet 40 lightyears away. There is a planet every K meters that can house a fuel tank to serve as a checkpoint. Let F be the amount of fuel to take a ship between two adjacent planets. Let 0 be the first and L be the last checkpoint.

Suppose a rocket can hold 3F. Go to A, deposit F, and return 2 times. Next rocket goes to B, stopping at A each way to take F -- do the B trip two times. Now you have two tanks at B and none at A. Repeat like binary addition till you fill L-2 with F, then repeat for L=L-3 to L=0. Now each checkpoint except the last and next-to-last has 1F. A final ship can make the trip to the planet, build a civilization, find a fuel source and return with pics.

Re: Seven earth-sized planets discovered circling a star 39 light years from Earth

#172

Post by [deleted] »

longerthoughts wrote: post #136
Sharlin wrote: post #50

Earlier quoted context omitted.

They are still in separate orbits so the straight line between any two varies greatly in length... not to mention intersecting the star regularly.

Regular shuttles for interplanetary travel timed with periodically favorable orbital positions?

[deleted]

Re: Seven earth-sized planets discovered circling a star 39 light years from Earth

#173

Post by nickff »

RangerScience wrote: post #166
nickff wrote: post #134

Earlier quoted context omitted.

There has been and continues to be cross-contamination between Venus, Earth, and Mars, so it seems likely that planets much closer together, and passing each other more frequently would have more 'communication' of materials.

Continues to be...? Outside of human action, what's the vector?

My understanding is that it is mostly due to solar wind, meteorite impacts, and various other infrequent events.

Re: Seven earth-sized planets discovered circling a star 39 light years from Earth

#174

Post by colordrops »

RangerScience wrote: post #166
nickff wrote: post #134

Earlier quoted context omitted.

There has been and continues to be cross-contamination between Venus, Earth, and Mars, so it seems likely that planets much closer together, and passing each other more frequently would have more 'communication' of materials.

Continues to be...? Outside of human action, what's the vector?

powerful meteor strikes spreading debris out of orbit.

Re: Seven earth-sized planets discovered circling a star 39 light years from Earth

#175

Post by pshposh »

dagurp wrote: post #153
dmreedy wrote: post #70

Earlier quoted context omitted.

I guess J.J. Abrams is somewhat forgiven for this, then: http://vignette4.wikia.nocookie.net/startrek/images/2/29/Vul... [edited for direct .jpg]

Firefox tries to download this file

It doesn't work in Microsoft Edge either (yup I use it).

Re: Seven earth-sized planets discovered circling a star 39 light years from Earth

#176

Post by mturmon »

semaphoreP wrote: post #125
twoodfin wrote: post #105

Earlier quoted context omitted.

Optically? That's nuts! Anyone know how this would work? Can we really expect Webb to measure light diffraction/refraction through a few miles of atmosphere on a planet 40 ly away?

It'll be in the near-infrared, but the light won't be separated from the star. How they observe the atmosphere is that when the exoplanets transit, they block out different amounts of light at different wavelengths. From that, one can deduce an atmospheric spectrum.

Absolutely right. Here is a recent paper on exoplanet atmosphere characterization by JWST: https://arxiv.org/abs/1511.05528 -- the overview is at https://jwst.nasa.gov/origins.html

As you say, the contrast between seeing (star + planet) during a transit, versus star alone, is enough to identify absorption of infrared light by some chemical species.

The simulations in the above paper basically show they can infer some chemical abundances (carbon, oxygen) and some atmospheric parameters (inversion layers) for Neptunes and Jupiters. But probably not for Earths, so not for the system in the OP. Even for big, thick atmospheres, these spectroscopic characterizations take a lot of observation time (like, days).

The race is indeed on to develop instruments and algorithms for this problem -- e.g., detecting CH4 or CO2 in an exo-Earth atmosphere. There's feverish activity in the Astronomy community around this, and post-JWST missions are being formulated to tackle the problem.

Re: Seven earth-sized planets discovered circling a star 39 light years from Earth

#178

Post by delecti »

aaronblohowiak wrote: post #137
dexwiz wrote: post #62

Earlier quoted context omitted.

No, but we probably could with enough fuel. The bigger issue is space dust. Hitting it at relativistic speeds would be like flying into a cosmic shotgun for the entire journey.

Could that cause accidental fusion?

Assuming this [1] is reasonably accurate, very much yes. It proposes fusion occurring at speeds as "slow" as 0.9c.

[1] https://what-if.xkcd.com/1/

Re: Seven earth-sized planets discovered circling a star 39 light years from Earth

#179

Post by nxc18 »

dagurp wrote: post #153
dmreedy wrote: post #70

Earlier quoted context omitted.

I guess J.J. Abrams is somewhat forgiven for this, then: http://vignette4.wikia.nocookie.net/startrek/images/2/29/Vul... [edited for direct .jpg]

Firefox tries to download this file

Doesn't work on IOS either (chrome specifically).

Re: Seven earth-sized planets discovered circling a star 39 light years from Earth

#180

Post by strictnein »

imdsm wrote: post #148
johngalt wrote: post #130

Close orbit around a relatively cold star. Interesting. I wonder what their 'day' vs 'year' looks like. Also their atmosphere and surface pressure. They could be 7 copies of Venus for all we know.

If they are tidally locked as reported, then there will be no day, not really. Just as there is no day on the moon.

The moon rotates once every ~27 days, so its day is ~27 days. It's just in sync with its orbit of the earth, so it appears to us that it doesn't rotate.

http://www.space.com/24871-does-the-moon-rotate.html

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