• Welcome! The TrekBBS is the number one place to chat about Star Trek with like-minded fans.
    If you are not already a member then please register an account and join in the discussion!

Proxima Centauri has an earth like planet!

Some of the planets listed in these Star Trek sources are much larger than Jupiter: I 0.14 - 10 Gm, S 10 - 50 Gm, T 50 - 120 Gm (Gm = gigameter = 10^6 km). However, there is good reason to suspect that such large planets cannot exist. They would be unable to support themselves against their gravity, and they would collapse to smaller sizes. If the Sun did not have its heat, it would collapse to a white-dwarf state with a radius close to the Earth's.

For instance, Seager2007.pdf by Sara Seager and others. It's very technical, but it has a nice graph of some calculated sizes on PDF page 6, Figure 4.

From the calculations, the largest Jovian-composition cold planet has a mass of about 1000 Earth masses and a radius of about 75,000 km (11.8 Earth radii), a bit more than Jupiter's. More mass, and it is smaller. The largest Earthlike-composition planet has a radius of about 15,000 km (2.35 Earth radii), and the largest all-water planet a radius of about 25,000 km (4 Earth radii). Both such planets also have a mass of about 1000 Earth masses.
 
Last edited:
Actually I was musing on Venus, what would life be like right now had Venus developed along the same lines as Earth and been more temperate?

Do you think we'd have visited by now?
 
Coco Pops 1967 said:
Actually I was musing on Venus, what would life be like right now had Venus developed along the same lines as Earth and been more temperate?
Click to expand...
It would have to have avoided its runaway greenhouse effect, which would be rather difficult for its location. But if it did, it could still have liquid water. The Earth's average temperature is about 15 C, and scaling to Venus's distance gives 66 C. Some Earth organisms can survive such temperatures, and even metabolize and grow and reproduce, so if there was liquid water on Venus's surface, it could have organisms in it.

From Vapour pressure of water - Wikipedia, it is about 0.0168 atm for 15 C and 0.2469 atm for 65 C. This means that Venus's atmosphere could hold about 15 times as much water as the Earth's, and that can give plenty of water-vapor greenhouse effect. So that's why I say that it's difficult to avoid.

Do you think we'd have visited by now?
Click to expand...
We've already visited that planet, in the form of spacecraft landing there, but we would have sent more there, like the ones that we have sent to Mars.
 
lpetrich said:
It would have to have avoided its runaway greenhouse effect, which would be rather difficult for its location. But if it did, it could still have liquid water. The Earth's average temperature is about 15 C, and scaling to Venus's distance gives 66 C. Some Earth organisms can survive such temperatures, and even metabolize and grow and reproduce, so if there was liquid water on Venus's surface, it could have organisms in it.

From Vapour pressure of water - Wikipedia, it is about 0.0168 atm for 15 C and 0.2469 atm for 65 C. This means that Venus's atmosphere could hold about 15 times as much water as the Earth's, and that can give plenty of water-vapor greenhouse effect. So that's why I say that it's difficult to avoid.


We've already visited that planet, in the form of spacecraft landing there, but we would have sent more there, like the ones that we have sent to Mars.
Click to expand...


So there was never any chance of it having a temperature similar to Earth had it not had that greenhouse effect run wild?
 
publiusr said:
A couple of other candidates

This reminds me a little of Helliconia
https://en.wikipedia.org/wiki/Wolf_1061
Click to expand...
Titled link: Wolf 1061 - Wikipedia

Three known planets, with estimated surface temperatures 222 C, 48 C, and -66 C.

Estimates done by scaling with the Stefan-Boltzmann law from the Earth's average surface temperature of 15 C. Estimated in this way, the surface temperatures of Venus and Mars are 66 C and -40 C. That is fairly close to a common estimate for Mars, -55 C, but far below Venus's actual surface temperature.

This planet that is about 40 light years out--orbits its star very close in--"every 1.6 days at a distance of 1.4 million miles. "
https://en.wikipedia.org/wiki/Gliese_1132_b
Click to expand...
Gliese 1132 b - Wikipedia (or GJ 1132 b), also [1511.03550] A rocky planet transiting a nearby low-mass star -- they have both a mass and a size for it: 1.62(55) Earth masses and 1.16(11) Earth radii. This implies an average density of 6.0 +- 2.5 g/cm^3.

That's consistent with a largely or mostly rocky composition, but it does not rule out super oceans.

The authors estimate the planet's equilibrium temperature to be 306 C for Bond albedo 0: perfect absorber, and 136 C for Bond albedo 0.75: lots of clouds, like Venus. My own estimate is 328 C. So the planet will likely be much like Venus.

Gliese 1214 b - Wikipedia (GJ 1214 b) is a similar planet discovered earlier, though it's much larger: 6.55(98) Earth masses and 2.678(130) Earth radii. Its estimated temperatures are close to those for Gliese 1132 b.

Its density is about 1.88 g/cm^3, a figure that suggests that it is mostly water.

Extra-solar planets in motion
http://www.universetoday.com/133087/four-planet-system-directly-imaged-motion/
Click to expand...
Four Planet System Directly Imaged In Motion - Universe Today
HR 8799 - Wikipedia
It must be conceded that those planets have not been seen over much of their orbits: 7 years for that video, and 17 years if one counts the HST pre-discovery picture.
Wikipedia periods: 45, 100, 190, 460 years
Universe-Today periods: 49, 112, 225, 450 years

Fomalhaut b - Wikipedia
A similar planet, with an estimated period of 1700 years.
 
Coco Pops 1967 said:
Oh yeah oopsie....... Forgot that bit. Well I guess in that case Earth is quite the fortunate one.
Click to expand...

Our greater distance, faster rotation and ocean saved us.

We actually have about the same amount of CO2 as Venus did. We're standing on it. It's bedrock. Limestone.chalk..what have you.

All the little icky microscopic things took CO2 out of the atmosphere and made little skeletons out of it--after polluting the planet with oxygen. We need oxygen for immediate respiration--the mammalian heart the equivalent of a big block engine with blowers.

But over time--it is oxygen which ages and kills us--that why they sell anti-oxidants to rid us of free-radicals.

Oxygen and water are actually bad for DNA--even though we need both.

Early lide got it right. Reptiles have less of a footprint than mammals. They take in oxygen--but are cold blooded--so food goes farther.

Something I learned from another board. You don't give somebody with a heart attack pure oxygen. The vessels narrow and things get worse. You have to mix just a bit of CO2--to slip the rest of the high oxygen content air in so you avoid vasoconstiction.

The dino-killing asteroid landed on carbonate rock--and it helped with a greenhouse spile. Pave roads with asphault--and you still need hydrocarbon tar. Want to use concrete? Well, here is a reason some want these new wood skyscraper concepts.

http://www.pbs.org/wgbh/nova/transcripts/27rbroman.html

NARRATOR: The recipe for concrete was written down by the Roman architect Vitruvius in the first century BC. The main ingredient comes from one of the most common materials in the world, limestone.

TONY ROOK: If you take ordinary limestone, which is a pretty heavy sort of stuff, and heat it to red hot, and leave it long enough at red hot, when you finish, you get stuff which is like this, which is very, very light, it's a very, very light material, and that's called quicklime.

NARRATOR: Quicklime is chemically very different from limestone. All the carbon dioxide has been burned off. Then, when water is added, something strange starts to happen.

TONY ROOK: Hear it starting to do something. It starts crackling. All the hissing is just steam coming out of it. Each individual bit is swelling and turning into a new material. Because it is very, very hot now. In fact, you wouldn't be able to put your hand close to it now. And it's slowly turning itself into one of the finest powders you can make, which is called hydrated lime, or just lime.

NARRATOR: As more water is added, the powder turns into a putty adhesive enough to bond the coarse materials that make up concrete.


No limestone on Venus--or very little I might imagine
 
publiusr said:
Our greater distance, faster rotation and ocean saved us.

We actually have about the same amount of CO2 as Venus did. We're standing on it. It's bedrock. Limestone.chalk..what have you.

All the little icky microscopic things took CO2 out of the atmosphere and made little skeletons out of it--after polluting the planet with oxygen. We need oxygen for immediate respiration--the mammalian heart the equivalent of a big block engine with blowers.

But over time--it is oxygen which ages and kills us--that why they sell anti-oxidants to rid us of free-radicals.

Oxygen and water are actually bad for DNA--even though we need both.

Early lide got it right. Reptiles have less of a footprint than mammals. They take in oxygen--but are cold blooded--so food goes farther.

Something I learned from another board. You don't give somebody with a heart attack pure oxygen. The vessels narrow and things get worse. You have to mix just a bit of CO2--to slip the rest of the high oxygen content air in so you avoid vasoconstiction.

The dino-killing asteroid landed on carbonate rock--and it helped with a greenhouse spile. Pave roads with asphault--and you still need hydrocarbon tar. Want to use concrete? Well, here is a reason some want these new wood skyscraper concepts.

http://www.pbs.org/wgbh/nova/transcripts/27rbroman.html

NARRATOR: The recipe for concrete was written down by the Roman architect Vitruvius in the first century BC. The main ingredient comes from one of the most common materials in the world, limestone.

TONY ROOK: If you take ordinary limestone, which is a pretty heavy sort of stuff, and heat it to red hot, and leave it long enough at red hot, when you finish, you get stuff which is like this, which is very, very light, it's a very, very light material, and that's called quicklime.

NARRATOR: Quicklime is chemically very different from limestone. All the carbon dioxide has been burned off. Then, when water is added, something strange starts to happen.

TONY ROOK: Hear it starting to do something. It starts crackling. All the hissing is just steam coming out of it. Each individual bit is swelling and turning into a new material. Because it is very, very hot now. In fact, you wouldn't be able to put your hand close to it now. And it's slowly turning itself into one of the finest powders you can make, which is called hydrated lime, or just lime.

NARRATOR: As more water is added, the powder turns into a putty adhesive enough to bond the coarse materials that make up concrete.


No limestone on Venus--or very little I might imagine
Click to expand...


You might know of this.

Wasn't there a form of concrete made in Roman times that supposedly is stronger then what we have today?
 
Coco Pops 1967 said:
You might know of this.

Wasn't there a form of concrete made in Roman times that supposedly is stronger then what we have today?
Click to expand...
http://io9.gizmodo.com/how-the-ancient-romans-made-better-concrete-than-we-do-1672632593
The Roman recipe used by the team involves adding volcanic rocks to a liquid mortar. To make the mortar, ancient Romans — and the modern research team — started by heating limestone into quicklime, and then added water and volcanic ash. The key ratio for this mixture is three parts ash to one part lime. Rome had no shortage of volcanic ash to use, since volcanoes lay to north and south of Rome. But the ancient Romans settled on the Pozzolane Rosse ash from the Alban Hills volcano to the south. This "pozzolonic mortar," say the researchers, "is key to the durability of concrete components in structurally sound monuments well maintained over two millennia of use."

It's the reaction that occurs between the lime and the volcanic material that produces the stronger concrete, the researchers found. As the concrete hardened, strätlingite crystals formed in spaces around the sand and the volcanic gravel, making the structure stronger. The crystals do the same work that microfibers do in our modern concrete, but are resistant to corrosion and are generally better at reinforcing those spaces.
Click to expand...
 
There are a few problems. The biggest is that we don't have near enough volcanic rock to keep up with the amount of concrete used today. Another problem is that many modern day construction techniques require fast drying concrete and this dries too slow. If I remember correctly people are researching an alternative to volcanic rock and also ways to increase the drying time. I don't know where this has led, but think it would be pretty funny if after all these modifications they end up with normal quick dry cement.
 
Of course, the Romans didn't use steel reinforcing so while it was good under compression, their concrete was rubbish under tension. That's my understanding -- I'm not a civil engineer.
 
Unless we used steel reinforcing roman concrete. I don't see why we couldn't. Still the other issues remain though.
 
Titled link: Studying Proxima b: Tiny Sailing Probes Could Orbit Nearby Exoplanet. I'm not impressed, because there are some huge technical challenges, like keeping the beams aimed at the spacecraft. There is also the problem that there does not seem to be any way of decelerating the spacecraft at their targets, making their missions high-speed flyby ones. There is the additional problem of transmitting data back to us.

How Breakthrough Starshot's Interstellar Probes Would Work (Infographic) lists
  • Building and cooling a ground-based light-beamer array
  • Overcoming atmospheric interference on the laser beams as they exit Earth's atmosphere
  • Precise aiming of the probes at an exoplanet
  • Integrity and stability of the sail under thrust
  • Fast travel through the interstellar medium (dust, gas, cosmic rays)
  • Maintaining fuctionality over decades in space
  • Precision aiming of cameras at target
  • Precision aiming of transmitter at Earth
  • Transmitting images using a laser as a transmitter and the sail as an antenna
  • Power generation and storage
  • Policy issues

How Interstellar Space Travel Works (Infographic) is a nice summary.
 
You must log in or register to reply here.

Similar threads

Callum MacLeod
Star Trek: Mjolnir - Worldship
Replies
6
Views
401
Callum MacLeod
Callum MacLeod
E
What can we make? (no Earth)
2 3
Replies
52
Views
3K
Cryogenator
Cryogenator
K
United Planets Cruiser C-514
Replies
2
Views
802
publiusr
P
B
Bohandi and Ansoids (my original alien species)
Replies
14
Views
631
BohandiAnsoid
B
TommyR01D
Voyager and Red Dwarf in Comparison
Replies
7
Views
715
Richard S. Ta
Richard S. Ta
If you are not already a member then please register an account and join in the discussion!

Sign up / Register


Back
Top