[SpookyZalost]

discuss all space related topics here.

let's start with this new one that popped up on the NASA website.

so apparently when the hubble takes deep field images something interesting shows up sometimes.




those curvy lines are asteroid trails, they show up due to the long exposures needed for photographing distant galaxies.

the shape is because of Hubble's orbit around earth, many of these distant space rocks were too faint to be discovered otherwise.

"Astronomers found a unique asteroid for every 10 to 20 hours of exposure time." - NASA


this is part of the mission of the frontier fields program.

[Guardian]

That looks awesome! All those galaxies!

Space is... insane.

[SpookyZalost]

indeed, space is a beautiful wonderful, incomprehensible thing which drives many people mad trying to understand it lol.

[SpookyZalost]

wanted to post some new interesting information here.

so everyone's heard about all those exoplanets they keep finding, the so called "super earth's" I'm sure when looking at the 2 to 8 earth masses you probably think... nah we can't go there, that's 2x to 8x earth gravity.

well that's partially right...

see the equation for surface gravity is the mass divided by the radius Squared.

g = G * M / r^2

let's apply that equation to the closest exoplanet, proxima centauri B.

mass: 1.27

Approximate Radius: 1.1

g = G * 1.27 / 1.1^2

first you convert those numbers to metric.

Earth:

Mass: 5.98 * 1024kg

Radius: 6378 km

Proxima Centauri B:

Mass: 7586472000000000kg

Approximate Radius: 7008.1km

so the surface gravity is
0.0000000103089776 m/s^2

or just under 1 G

Earth's surface gravity is

0.0000000010495868 m/s^2

so while the planet is bigger, and more massive it's surface gravity is lower.

keep that in mind next time you hear about an exoplanet, because you may weigh less not more than you do here on earth... and even if it is higher, it might not be by as much as you think Density play's a key role here, the less dense, the greater the surface area and thus the lower the surface gravity.

[SpookyZalost]

anyone done any time dilation calculations for travel time?

right now if you get the right slingshot orbit with a solar sail ship you can get approx .7C or 70PSL.
figuring in the time dilation factor it's about 14 years on ship for every 20 years traveled. or close to 25% slowdown.

given that I wouldn't mind making the trip out to Alpha centauri in cryo sleep on a sufficiently advanced ship, after all 40 years there and back isn't nearly as bad as 10,000 years.

and in other news.

K2-229, is a star with 3 exoplanets.
what's special about this star however is K2-229b, the closest in planet which is a super earth planet of a radius of 1.2 Earth radii and a mass of 2.6 Earth masses, hence a bulk density of 8.9 g/cm3, this super dense planet has more in common with mercury than earth and it's suspected to be mostly iorn core much like our innermost planet... basically it's an earth sized space cannonball.

[Guardian]

anyone done any time dilation calculations for travel time?

Nope!

right now if you get the right slingshot orbit with a solar sail ship you can get approx .7C or 70PSL.
figuring in the time dilation factor it's about 14 years on ship for every 20 years traveled. or close to 25% slowdown.

given that I wouldn't mind making the trip out to Alpha centauri in cryo sleep on a sufficiently advanced ship, after all 40 years there and back isn't nearly as bad as 10,000 years.

Crazy to think about. Would be pretty insane, but we need to get some interest in space exploration going first. Until then, no incentive for some research into getting specifics right. I'm sure there's plenty of opportunity to monetize, it's just a huge risk with no guaranteed return.

basically it's an earth sized space cannonball.

...and its terrifying when you put it like that. Imagine a planet getting smacked with that one? Yikes.

[Darth-Apple]

Hopefully you could get a ship that could go so fast that you time travel and don't age in the process. Then, essentially, you haven't lost 40 years at all.

Interesting calculations and information, thank you for posting.

Are there any earth-like planets that are smaller in size and mass than our planet, or is ours generally considered to be pretty small for its kind?

[SpookyZalost]

Darth: I don't know about earth like given the radiation conditions but the nearest exoplanet (proxima Centauri b) is just a bit bigger than earth but lower in mass, the gravity is around .9 G's.

Tau Ceti has one that while not as hospitible as earth given it's orbit only has a surface gravity of around 1.2 g's which is actually not nearly as bad... it's also much larger than earth.

[Darth-Apple]

Interestingly enough, I read an article not too long ago that said that planets with significantly more mass than earth would have the problem of alien civilizations being unable to depart from the planet's surface due to the gravitational pull. More fuel would be required to overcome it, and more fuel would weigh more, causing even more fuel to be consumed. Space travel would be inhibited on those planets due to the gravitational pull.

Makes you wonder if Earth has almost the perfect mass.

[SpookyZalost]

Darth: indeed, on the other hand mass =/= gravity so if the planet is big enough then higher mass wouldn't matter... to a point.

in cases of 3 to 4 earth masses or more though I could totally see that... if you can deal with the fused tectonic plates and planet wide super storms first...