Is there information already on how the short distances between planets would affect G-forces felt on surface?
Seven earth-sized planets discovered circling a star 39 light years from Earth
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Re: Seven earth-sized planets discovered circling a star 39 light years from Earth
#222Do we know definitively that there are no other planets in this system? The presence of a large, Jupiter-sized planet in a system is thought to be helpful for deflecting asteroid impacts. Obviously we are talking 'to scale' given TRAPPIST-1 itself is around the size of Jupiter! The more we learn about this system is going to be fascinating though - the supposed inward migration of these planets may even help us under…
Is it possible there isn't an asteroid belt to be concerned about?
Re: Seven earth-sized planets discovered circling a star 39 light years from Earth
#223Wiki says "TRAPPIST-1 is an ultracool dwarf star that is approximately 8% the mass of and 11% the radius of the Sun. It has a temperature of 2550 K and is at least 500 million years old." https://en.wikipedia.org/wiki/TRAPPIST-1 Too young star for alien life hopes?
Earth is 4.5G years old, and the earliest undisputed microbial life fossils are 3.5G years old, so that gives 1000 million years.
But we can also say that Earth was cool enough for liquid water 4.4G years ago, and there are some findings suggesting microbial life already 4.1G years ago. So only 300 million years, at maximum.
Re: Seven earth-sized planets discovered circling a star 39 light years from Earth
#224My favourite part of the press release: > The planets also are very close to each other. If a person was standing on one of the planet’s surface, they could gaze up and potentially see geological features or clouds of neighboring worlds, which would sometimes appear larger than the moon in Earth's sky. > In contrast to our sun, the TRAPPIST-1 star – classified as an ultra-cool dwarf – is so cool that liquid water cou…
And they all seem to rotate around their sun in 1.5-20 days. https://i.kinja-img.com/gawker-media/image/upload/s--YG_G3T_...
Revolve around. Sorry, had to.
Re: Seven earth-sized planets discovered circling a star 39 light years from Earth
#225Earlier quoted context omitted.
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
Isn't that technically the moon's "year"?
A year generally refers to the time something takes to make one revolution around its closest star.
Re: Seven earth-sized planets discovered circling a star 39 light years from Earth
#226Is there information already on how the short distances between planets would affect G-forces felt on surface?
The earth moon distance is tiny, and the G-Forces are hard to directly measure.
Re: Seven earth-sized planets discovered circling a star 39 light years from Earth
#227Re: Seven earth-sized planets discovered circling a star 39 light years from Earth
#228Earlier 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…
> 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 immediate galactic vincinity, such that moving at 0.998c relative to earth is also moving at a very similar fraction of c relative to lots of other things you are going to potentially hit on a journey from earth to a nearby star system?
Re: Seven earth-sized planets discovered circling a star 39 light years from Earth
#229To 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)
> 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)
That is assuming constant energy consumption to sustain 1g, but unfortunately that's not the case, the closer you get to the speed of light, the more energy you'd need to sustain 1g, and this becomes unrealistic long before you are anywhere close to the speed of light.
Re: Seven earth-sized planets discovered circling a star 39 light years from Earth
#230To 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)
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