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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

#241

Post by kakarot »

dwaltrip wrote: post #158
hughes wrote: post #122

Earlier quoted context omitted.

> trillions of years This is off by several orders of magnitude. Like estimating the age of your neighbor to be somewhere around 400,000 years old.

Uh? I think it's widely accepted that our best models of small stars are fairly well understood, and predict that they will continue to fuse hydrogen in their cores for more than a trillion years.

Referring to an average of 1-2 trillion years as "trillions of years" is either misleading, uninformed, lazy, or a combination of the 3. When dealing with hard science it's important to choose your descriptors wisely. Most readers will not follow up.

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

#242

Post by wallace_f »

ryandrake wrote: post #213
delecti wrote: post #157

Earlier quoted context omitted.

Just going that fast isn't really risky at all (assuming you don't hit anything, which isn't actually a safe assumption). The tough part is making something capable of a constant 1g of acceleration for a 7 year trip. Most of the craft we make only accelerate for the first small percent of a trip. We can do accelerations that high, but not for very long, and we can't even manage acceleration for such a long duration e…

Also, and I'm not an astrophysicist, but I believe going fast _relative to Earth_ doesn't make it any more or less likely that you're going to hit anything. Moving at .998c relative to Earth and hitting something that is stationary relative to Earth is the same thing as not moving and being hit by something going .998c relative to you. EDIT: Right, as chris_va pointed out, we're all traveling at .998c relative to som…

>doesn't make it any more or less likely that you're going to hit anything.

I believe that would be wrong. Also not an astrophysicist but I would guess that most of the stuff in our galaxy is moving at speeds which are, on average, relative to our galaxy, and moving at some average rotational speed around it. Of course there could be stray bits moving quite quickly on through.

So moving at c relative to the planets and solar systems swirling around our galaxy probably would make you more likely to hit something.

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

#243

Post by kakarot »

mtgx wrote: post #42
eb0la wrote: post #3

At Voyager-I speed (17km/s) we need just 688k years to get there. Not bad considering the humble satelite doesn't accelerate anymore.

I doubt we'll attempt serious inter-stellar travel before we figure out antimatter or black hole-powered engines. So we may have to wait a century or two. This century we should be more worried about making fusion-powered intra-solar system travel a common thing, and about establishing large colonies on Mars and several moons.

I don't know about all of that speculation, but you did give me a nice mental image of a barren, battle-scarred solar system littered with battleships containing black holes, ready to cause catastrophe at any moment, much like the nuclear wastelands of the Arctic.

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

#244

Post by pshposh »

idbehold wrote: post #209
pshposh wrote: post #155

Earlier quoted context omitted.

But what if we are the first and no filter exists at all?

That's almost equally depressing. "Really, we're the best the universe has to offer?"

This is the best Earth has to offer is how I prefer to think about it. Though I am not even sure humans are the best we have to offer anyways.

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

#245

Post by ionwake »

dragonwriter wrote: post #206
ionwake wrote: post #165

Earlier quoted context omitted.

Thats the one I read. It sounds awesome. Srsly give me 5% of the GDP of the US and I'll put a monkey on Trappist within 5 years. Monkey time. *Im not being serious, I have no idea how much it would cost or if it would even work.

Project Orion doesn't get you anywhere close to 1G constant acceleration to turnover and constant deceleration the rest of the way; a fairly high performance Orion concept for interstellar use did have 1G acceleration, but only for 10 days on each end of a 133 year trip to Alpha Centauri -- and needed 300,000 nuclear bombs with 1 megaton yield each as fuel. > Srsly give me 5% of the GDP of the US and I'll put a monke…

Thank you for your feedback, however with all due respect, with my limited understand, if the acceleration is achievable, you are wrong.

The monkey would arrive, like I said, in monkey time, within 5 years. This is ofcourse assuming there would be no deceleration phase.

The monkey would unfortunately however, die on impact.

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

#246

Post by ryandrake »

dragonwriter wrote: post #228
ryandrake wrote: post #213

Earlier quoted context omitted.

Also, and I'm not an astrophysicist, but I believe going fast _relative to Earth_ doesn't make it any more or less likely that you're going to hit anything. Moving at .998c relative to Earth and hitting something that is stationary relative to Earth is the same thing as not moving and being hit by something going .998c relative to you. EDIT: Right, as chris_va pointed out, we're all traveling at .998c relative to som…

> Also, and I'm not an astrophysicist, but I believe going fast _relative to Earth_ doesn't make it any more or less likely that you're going to hit anything. OTOH, given that it is (like most of the stuff around it) orbiting the center of mass of the Milky Way Galaxy, shouldn't Earth be moving relatively close (within a very small fraction of light speed) to the speed of most of the interstellar dust, etc., in its i…

Of course. Thanks. This is why they don't put me in charge of our next interstellar trip.

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

#247

Post by infogulch »

semaphoreP wrote: post #200
coryfklein wrote: post #149

I'm having a hard time finding more data on the density of matter in interstellar space. Wikipedia says > The density of matter in the interstellar medium can vary considerably: the average is around 10^6 particles per m3 but cold molecular clouds can hold 10^8–10^12 per m3 [1] But I imagine that interstellar gas would be easier to fly through than interstellar sand. Do we know the composition of matter in interstell…

It's almost all Hydrogen/Helium gas. Other larger atoms and molecules are known to exist in the interstellar medium, but it's primary gas. Also, a good way to remember the density is ~1 Hydrogen atom per cm^3.

How about intergalactic densities?

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

#248

Post by Retric »

jerf wrote: post #167
noobermin wrote: post #88

Earlier quoted context omitted.

Of course, #askNasa didn't win me a question, but could any astrobiologists comment on this question: Tidal locking means the planets would always have a side facing the star, leading to very different thermodynamics in terms of climate and weather on the planet, not to mention radiation. Doesn't that very much hurt the chances for life on those planets?

The debate rages. The problem is that one side of the planet is essentially exposed to space and thus tends to be at cosmic background temperature, and the other side exposed to the star. It is thought by a lot of people that anything volatile enough to be a gas, ever (so, including water), would rapidly end up migrating over to the frozen side, so even if the planet started with the right mix of water and whatever o…

Oceans can move a lot of heat around a planet, so the cold side could stay well above freezing. Remember it's T^4 so cold areas radiate far less heat.

That said, if there where minimal atmosphere then the effects your talking about become a larger issue. Atmosphere is largely a function of solar wind and volcanic activity which relates to the isotopes in a planets core making this hard to predict.

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

#249

Post by Beltiras »

autokad wrote: post #49
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)

2000 saturn v rockets sounds possible

That's 2000 chemical rockets. The example talks about a perfect Hydrogen-Helium conversion.
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