An exoplanet with a minimum mass of 8.47±0.47 Earth masses has been discovered around 40 Eridani A:
"Star Trek's" planet Vulcan, ancestral home of Spock and his species, just became a little more real, thanks to a team of exoplanet scientists. Because "Star Trek" creators eventually associated planet Vulcan with a real star, called 40 Eridani A, scientists have wondered for years whether a factual equivalent of the beloved science fiction planet exists, with or without pointy-eared inhabitants. And now, a team of scientists has said that the star really does host at least one planet.
"This star can be seen with the naked eye, unlike the host stars of most of the known planets discovered to date," Bo Ma, lead author of the new research and an astronomer at the University of Florida, said in a statement. "Now, anyone can see 40 Eridani A on a clear night and be proud to point out Spock's home." That star, located about 16 light-years away from Earth, is also known as HD 26965. It's a bit orange, because it's a little smaller and cooler than our sun. But it also has some clear similarities to Earth's star: It's about the same age and sports a fairly similar sunspot pattern.
Also at Science Magazine.
(Score: 2) by r1348 on Wednesday September 19 2018, @11:50AM (17 children)
Revolution period of 42 days = close orbit = tidally locked = no life
(Score: 2) by fyngyrz on Wednesday September 19 2018, @02:12PM (8 children)
Boundary conditions might allow for semi-sorta earthlike life on a tidally locked planet (although it's difficult to imagine that the gravity of a planet with 8 earth masses will.) It probably means no life globally, though. At least, no life remotely like us, globally.
It also means no spaceflight without technology we have not even imagined. Much more than one earth gravity, and you're definitely not getting into orbit with chemical rockets.
OTOH, planets with less than one earth gravity will have a considerably easier time of it than we do.
(Score: 0) by Anonymous Coward on Wednesday September 19 2018, @04:11PM (4 children)
It's even worse than that. Even with lower density to achieve the same surface gravity, more mass means higher orbital velocity.
To grab an extreme but handy example, consider the sun, enclosed by a Dyson sphere of negligible mass and ~3.7Gm radius. The gravity on the outer surface of the sphere is 1g, same as Earth -- but the near-surface orbital velocity is 190 km/s instead of Earth's 7.9 km/s.
More specifically, for 8.47 M⊕, the radius required for surface gravity of 1g is an improbable 8.47½ R⊕ = 2.91 R⊕, but the resulting orbital velocity is 8.47¼ = 1.7x Earth's, or 13.5 km/s.
(Score: 2) by takyon on Wednesday September 19 2018, @04:49PM (3 children)
With big enough multi-stage rockets or perhaps nuclear rockets [nextbigfuture.com], an alien civilization could still be able to get into space and to other planets, even with higher surface gravity and orbital velocity, and very small payloads sent to orbit and beyond using fully expendable rockets. Then they could establish themselves on another planet or satellite with more manageable gravity, assuming one is available. For one example, it looks like multiple planets in the TRAPPIST-1 [wikipedia.org] system could support life, and even the small ones have higher masses than Mars.
It may take centuries longer and more units of currency for aliens to escape such a planet, which could mean that they end up dying in a global war before they have a chance to spread. But they still have a chance. They could build small robots to set up the support infrastructure on another planet in their system, and they could send their equivalent of frozen eggs and an artificial womb instead of a full-sized craft with life support. Anything they can do within mass constraints.
[SIG] 10/28/2017: Soylent Upgrade v14 [soylentnews.org]
(Score: 2) by bob_super on Wednesday September 19 2018, @06:38PM
Or they could just learn how to pinch the Higgs Field and find space access easier than your crossing the street to Starbucks.
Their cousins down the galaxy had been taunting them since they discovered how to funnel the energy from the fusion of Uranium in the flablolisk's stomach.
(Score: 2) by fyngyrz on Thursday September 20 2018, @08:10PM (1 child)
It gets harder — a lot harder — as gravity goes up.
More dangerous, too.
We got pretty lucky in terms of the gravity here. Sorta kinda. Luckier would have been a little less gravity. :)
(Score: 2) by takyon on Thursday September 20 2018, @08:35PM
Higher gravity, higher orbital velocity, higher escape velocity. Are these things surmountable or not? If aliens have to launch something bigger than Saturn V just to get 100 kg to orbit, they still have a chance to eventually escape their planet. It will just be far more costly and take much longer to get off the ground.
[SIG] 10/28/2017: Soylent Upgrade v14 [soylentnews.org]
(Score: 2) by r1348 on Wednesday September 19 2018, @08:18PM (2 children)
I heard of the boundary conditions model, and saw some simulations too, but I remain quite skeptical. Atmospheric pressure would cause it to flow from the hot side to the cold side, where it would freeze and precipitate. Very soon you find yourself with a planet with no gas atmosphere, even if it has enough mass to hold one. Less than idea for the formation of life.
(Score: 2) by fyngyrz on Thursday September 20 2018, @08:16PM (1 child)
Well, our form of life, anyway.
(Score: 2) by r1348 on Thursday September 20 2018, @08:57PM
As I explained in a post further down the thread, carbon-based organic chemistry in water solutions remains by far the best candidate as a precursor of life. I'm not claiming other ways are impossible because that would be like claiming to know every possible chemical combination, which would be outrageous, but it still is the most likely scenario. Just to give you an example on how easily spontaneous carbon-based chemistry is, we detected organic molecules like benzene and acetone in interstellar gas clouds. So even in the most extreme and barring environment you can think of, carbon chemistry still happens.
(Score: 2) by takyon on Wednesday September 19 2018, @04:31PM
Single-planet star systems could be extremely rare. I wouldn't rule out the possibility of more planets in this system with higher orbital periods.
[SIG] 10/28/2017: Soylent Upgrade v14 [soylentnews.org]
(Score: 2) by HiThere on Wednesday September 19 2018, @05:19PM (2 children)
At 8 times Earth's mass, it's probably a hot Neptune. Well, it's actually even heavier than Neptune, but since it's closer to the sun this might be necessary to hold onto Hydrogen...I'm not sure how hot it would be in a close orbit (shorter orbit than Mercury, which has an 88 day orbit), but it likely means there's no habitable planet in that system.
Javascript is what you use to allow unknown third parties to run software you have no idea about on your computer.
(Score: 2) by takyon on Wednesday September 19 2018, @05:45PM (1 child)
What is that supposed to mean? It is less massive than Neptune, and we don't know about the density since the radius is unknown. It could have a low density from being a puffed-up gas dwarf, or a high density for being a former gas giant with the gas blown away.
Nobody has ruled out additional planets around this star, with greater orbital periods.
[SIG] 10/28/2017: Soylent Upgrade v14 [soylentnews.org]
(Score: 2) by HiThere on Wednesday September 19 2018, @11:02PM
OK, you're right. That's about half Neptune's mass. I must have mis-read a Google search. That still puts it more at the gas giant size than the rocky size...though it's smaller than anything in this system. Perhaps it's hot enough to have lost most of its Hydrogen, though, so I guess it could be a bit rocky. Of course, the current theory says that the larger planets for far out and then migrate inwards, destabilizing the orbits of all the smaller planets as they come in. I don't know how certain that theory is, however, even for the local system, but if it applies to this planet's system, there won't be any habitable planets. OTOH, the resonances from this planet should be a lot weaker than those of Jupiter, so...
But at 8 Earth masses, it's not going to have a chemistry similar to one we know. I suspect it would retain Hydrogen released by splitting long enough for it to recombine, even near to top of the atmosphere. This despite the higher temperature. So the chemistry would probably be a lot more similar to that of Neptune despite the higher temperature.
Javascript is what you use to allow unknown third parties to run software you have no idea about on your computer.
(Score: 2) by bob_super on Wednesday September 19 2018, @06:31PM (3 children)
It's life, but not as you know it.
I often despair at some people's thorough lack of imagination...
(Score: 2) by r1348 on Wednesday September 19 2018, @08:25PM (2 children)
We can only build on what we know, I'm more than open to analyze models for "life as we don't know it", but I still have to see one without major flaws.
Take silicon-based life for example, probably the most popular alternative hypothesis to carbon-based: carbon dioxide is a gas in Earth-average temperatures, and it plays a major role in all the most basic metabolic processes. Silicon dioxide is, well, sand. Try imagining breathing out a bucket of it. And yes, it can be a gas too... at temperatures where you can't expect to find liquid water around.
(Score: 2) by bob_super on Wednesday September 19 2018, @08:41PM (1 child)
Why would you need liquid water to have life ?
(Score: 2) by r1348 on Thursday September 20 2018, @08:52AM
Because most of organic chemistry, and all that is involved in metabolic processes, happens in water solutions.