More clues that Earth-like exoplanets are indeed Earth-like

June 28, 2018 by Jason Maderer, Georgia Institute of Technology
The artist's depiction of Kepler-186f. Credit: NASA Ames/JPL-Caltech/T. Pyle

A new study from the Georgia Institute of Technology provides new clues indicating that an exoplanet 500 light-years away is much like Earth.

Kepler-186f is the first identified Earth-sized planet outside the solar system orbiting a star in the . This means it's the proper distance from its for liquid water to pool on the surface.

The Georgia Tech study used simulations to analyze and identify the exoplanet's spin axis dynamics. Those dynamics determine how much a planet tilts on its axis and how that tilt angle evolves over time. Axial tilt contributes to seasons and climate because it affects how sunlight strikes the planet's surface.

The researchers suggest that Kepler-186f's is very stable, much like the Earth, making it likely that it has regular seasons and a stable climate. The Georgia Tech team thinks the same is true for Kepler-62f, a super-Earth-sized planet orbiting around a star about 1,200 light-years away from us.

How important is axial tilt for climate? Large variability in axial tilt could be a key reason why Mars transformed from a watery landscape billions of years ago to today's barren desert.

"Mars is in the habitable zone in our solar system, but its axial tilt has been very unstable—varying from zero to 60 degrees," said Georgia Tech Assistant Professor Gongjie Li, who led the study together with graduate student Yutong Shan from the Harvard-Smithsonian Center for Astrophysics. "That instability probably contributed to the decay of the Martian atmosphere and the evaporation of surface water."

As a comparison, Earth's axial tilt oscillates more mildly—between 22.1 and 24.5 degrees, going from one extreme to the other every 10,000 or so years.

An artist's depiction of Kepler-62f. Credit: NASA Ames/JPL-Caltech/T. Pyle

The orientation angle of a planet's orbit around its host star can be made to oscillate by gravitational interaction with other planets in the same system. If the orbit were to oscillate at the same speed as the precession of the planet's spin axis (akin to the circular motion exhibited by the rotation axis of a top or gyroscope), the spin axis would also wobble back and forth, sometimes dramatically.

Mars and Earth interact strongly with each other, as well as with Mercury and Venus. As a result, by themselves, their spin axes would precess with the same rate as the orbital oscillation, which may cause large variations in their axial tilt. Fortunately, the moon keeps Earth's variations in check. The moon increases our planet's spin axis precession rate and makes it differ from the orbital oscillation rate. Mars, on the other hand, doesn't have a large enough satellite to stabilize its axial tilt. "It appears that both exoplanets are very different from Mars and the Earth because they have a weaker connection with their sibling planets," said Li, a faculty member in the School of Physics. "We don't know whether they possess moons, but our calculations show that even without satellites, the spin axes of Kepler-186f and 62f would have remained constant over tens of millions of years."

Kepler-186f is less than 10 percent larger in radius than Earth, but its mass, composition and density remain a mystery. It orbits its host star every 130 days. According to NASA, the brightness of that star at high noon, while standing on 186f, would appear as bright as the sun just before sunset here on Earth. Kepler-186f is located in the constellation Cygnus as part of a five-planet star system.

Kepler-62f was the most Earth-like exoplanet until scientists noticed 186f in 2014. It's about 40 percent larger than our planet and is likely a terrestrial or ocean-covered world. It's in the constellation Lyra and is the outermost planet among five exoplanets orbiting a single star.

That's not to say either exoplanet has water, let alone life. But both are relatively good candidates.

"Our study is among the first to investigate climate stability of exoplanets and adds to the growing understanding of these potentially habitable nearby worlds," said Li.

"I don't think we understand enough about the origin of life to rule out the possibility of their presence on with irregular seasons," added Shan. "Even on Earth, life is remarkably diverse and has shown incredible resilience in extraordinarily hostile environments.

"But a climatically stable planet might be a more comfortable place to start."

The paper, "Obliquity Variations of Habitable Zone Planets Kepler 62-f and Kepler 186-f," is published online in The Astronomical Journal.

Explore further: Orbital variations can trigger 'snowball' states in habitable zones around sunlike stars

More information: Yutong Shan et al. Obliquity Variations of Habitable Zone Planets Kepler-62f and Kepler-186f, The Astronomical Journal (2018). DOI: 10.3847/1538-3881/aabfd1

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wduckss
2.3 / 5 (3) Jun 29, 2018
The process of forming planets (bodies) must be identical. If the conclusion incorporate :
"The conclusion would be that it is a very complex and dynamic pattern related to the processes of objects' creation – it is constantly moving and growing. The complexity of objects is related to the space temperature, the mass of an object and the total sum of tidal forces. Furthermore, the complexity is influenced by the position of an object related to the planet, Sun, as well as the asteroid belt. The important role also belongs to time when object got captured, for how long the object had been near Sun (perihelion) and at what distance.
The goal of this article is to eliminate the biblical-style of thinking" disappear speculation. https://www.acade...r_system
rodkeh
1 / 5 (5) Jun 29, 2018
These idiots have no clue. The Earth is a very unique planet, chances of finding another is highly unlikely. Until these nitwits are able to understand the climate on this planet, they will never know what constitutes Earth-like.

When will we see a return to real science and put an end to all this fakery!
rrwillsj
4 / 5 (4) Jun 29, 2018
rk, you are complaining that others are making mistaken conclusions based on too little data. By committing the same error.

"Conclusions" are not valid until supporting evidence is collected, analyzed and verified through a variety of redundant experiments.

Usually resulting in bitter factional disputes of which "conclusions" are to be accepted as definite. And brawling over who gets to share the credit, the accolades and increased funding.
rodkeh
1.8 / 5 (5) Jun 29, 2018
rr, I make no such error. The scientific facts speak for themselves. These so called scientists are just more ignorant frauds claiming to know thing they have no clue of.
TrollBane
5 / 5 (4) Jun 29, 2018
"The scientific facts speak for themselves" Apparently they do so because you say they do. But perhaps I speak prematurely. Care to point us to where your detailed, insightful critique of their work is published?
rodkeh
1 / 5 (4) Jun 29, 2018
What good would that do? You couldn't understand it.
humy
5 / 5 (6) Jun 29, 2018
These idiots have no clue. The Earth is a very unique planet, chances of finding another is highly unlikely.
rodkeh

You are the idiot that has no clue, not they. Nobody is trying to find another Earth; just merely a vaguely Earth-like planet. And the scientists have already found several such vaguely Earth-like planets. So it apparently isn't "highly unlikely".

rodkeh
1 / 5 (3) Jun 29, 2018
humy

You're an idiot!
Those frauds have no clue of what constitutes Earth-like. They would have to first of all, have some idea of how our planet's climate works, to be able to know, which they don't.
TrollBane
5 / 5 (4) Jun 29, 2018
"What good would that do? You couldn't understand it." "You're an idiot!" "Those frauds..." Resorting to thinly-disguised -- or blatant -- insults is not how adults support an intellectual argument. Then again, you still haven't come close to trying to make an actual intellectual argument.
rrwillsj
3 / 5 (2) Jun 29, 2018
What baffles me? Is all these vast conspiracies to deny the self-ordained genius such as rodkeh, of public recognition and awards.

I mean, come on now, Rod! If the MIB wanted you suppressed? They are too stupid to simply disappear this site's entire cohort of similar mindless loons?

I am now sympathizing with those conspiracies. It must be exhausting to have to thwart your attempts to inform the masses of your hidden greatness. Over centuries and across the continents.

"Witherever thou goest! They have to goest?" What a drag! A job requiring anyone to have to chase all of you loons about.

And I thought kindergarten teachers had a tough profession!
rodkeh
1.7 / 5 (6) Jun 29, 2018
TB
I have long ago given up on finding anyone out there with two living brain cell to rub together. You twits have never had an original thought in your whole lives and you even lack the education to make up for it.
rodkeh
1.8 / 5 (5) Jun 30, 2018
rr
Evidently most things baffle you.
wduckss
1 / 5 (1) Jun 30, 2018
Do not get away from the topic. Exoplanets are far away, our ability to reach the truth (by observation) is minimal. That's the reality.
The problem is the people from the minimum "evidence", real sensation, and claim that they are exact evidence and the end of the story.
The only option is good to examine our system and without any desire for sensation, give evidence.
rrwillsj
3.3 / 5 (3) Jun 30, 2018
wd, yes, examining our system with 4 failed worlds out of 5 possibilities. Should give us a rough idea of what the odds are for discovering a Living World in star systems with stars similar to our Solar System and our Sun.

There is not enough data to extrapolate beyond that.

Each and every claim of Living Worlds has too be treated as a hoax based on falsified data. And will need extra-ordinary levels of proofs to confirm such extra-ordinary claims.

Yeah, you got caught robbing a bank. I will disregard the evidence proving that you were just helping out a buddy make his car payments.

TrollBane
5 / 5 (1) Jun 30, 2018
rodkeh can only hope of some day becoming anything more than an infected pimple on the backside of the body politic. He/she/it's credibility is what that sounds like when you read that fast. ;)

I wonder if he's tried the mail order black belt gambit yet? Perhaps that's a project for next month.
rodkeh
1 / 5 (3) Jun 30, 2018
TB
Pathetic!
wduckss
1 / 5 (1) Jul 01, 2018
rr, The approach to the problem (which you have outlined) is not good. You read (I have an impression) of just speculation. When you put the problem on the foundation of physics, everything looks different. The two articles (which I attach) are free of sensation, the foundation of the articles is the physics of star systems (without formulas). http://www.svemir...tructure & http://www.svemir...e-causal
Our system and little good will give most of the data.
humy
5 / 5 (3) Jul 01, 2018
humy

You're an idiot!
Those frauds have no clue of what constitutes Earth-like.

What constitutes "Earth-like" is up to the arbitrary definition and how Earth-like you want Earth-like to be and in exactly what ways. So, no, they aren't frauds because there isn't any non-arbitrary scientific definition of "Earth-like" and they don't pretend there is.
Ojorf
2.6 / 5 (5) Jul 01, 2018
rr, I make no such error. The scientific facts speak for themselves. These so called scientists are just more ignorant frauds claiming to know thing they have no clue of.


Ha ha, that IS funny. The scientists who gather the facts are ignorant of them, makes sense.

Those frauds have no clue of what constitutes Earth-like. They would have to first of all, have some idea of how our planet's climate works, to be able to know, which they don't.

Again, the people with the facts and the knowledge don't know anything? Ignorant fraud comes to mind.

Anyway, since loosely 'earth like' means 'life as we know it' could have evolved and survive somewhere, the conditions are, in a sense, fairly broad. Hence the habitable ZONE. We know plenty about the earths climate, it's the exoplanets climate we are unsure about, due to the limited data available.

As you say "You're an idiot!"
Ojorf
1.8 / 5 (4) Jul 01, 2018
I have long ago given up on finding anyone out there with two living brain cell to rub together. You twits have never had an original thought in your whole lives and you even lack the education to make up for it.


And you have a stupid name, aa, na, naaaaa!
rrwillsj
1 / 5 (1) Jul 01, 2018
ducks, goodwill is nice. But you cannot be courteous to false claims or even unsubstantiated claims.

The definitive proof of my opinion are orbiting our Sun. Out of five small, rocky worlds, only one is a Living World. And that is a "Best Case" baseline for searching other star systems for equivalent Living Worlds.

There seems to be an agreement among a number of the commentators that there is a good probability for a multitude of Archean-type planets of primitive micro-organisms.

With an underlying rapacious greed to populate those wolds with Earth-Life.

This would be an unconscionable act of hubris. Any such planet discovered would be unique treasure of truly alien life. It would be a crime to poison a world for no reason better than avarice!

Observe, even sample if correct safety precautions are strictly observed and enforced. Then let them go to evolve their own destiny in the future.
rodkeh
1 / 5 (3) Jul 01, 2018
humy

You're an idiot!
Those frauds have no clue of what constitutes Earth-like.

What constitutes "Earth-like" is up to the arbitrary definition and how Earth-like you want Earth-like to be and in exactly what ways. So, no, they aren't frauds because there isn't any non-arbitrary scientific definition of "Earth-like" and they don't pretend there is.

They have no clue so all they could do is pretend. As you say they have no clue of what constitutes Earth-like, because they don't even have an arbitrary definition! They have nothing to compare and nothing to compare it to.
They are stupid, ignorant Americans calling themselves scientists!
wduckss
1 / 5 (2) Jul 01, 2018
rr, Do not introduce physics into speculative discussions. Instead of the number of planets (bodies), observe the processes that form the planets (offered links).
It is not worth saying: there is or no life (all articles of such content are out). The limit beyond which no life is -130 ° C (biology) (Enceladus, Europe etc). (For Mars, look https://www.acade...correct)
The Wrong Ideas About Life Creating Zones http://www.svemir...tml#Life
rrwillsj
1 / 5 (1) Jul 01, 2018
ducks those opinions are even more speculative then mine. Based solely on wishful thinking. Without a shred of evidence for the opinionator's conjectures.

There are two planets in the Earth's orbit around Sol. Earth is the Living World. Luna is deader than polished brass spittoon!

Greed drives the gullible punter to place stupid bets. The dead horse you are daydreaming of betting om? Will not be winning, place or even show in anymore races. No matter the unbelievable odds offered you by the bookie.

Waiting for the horse you bet your rent on to show up for the race? Wave bhuy-by as the knackers wagon hauls your nag away. Tear up the tickets into confeti as you cry into your beer.
humy
5 / 5 (1) Jul 02, 2018

What constitutes "Earth-like" is up to the arbitrary definition and how Earth-like you want Earth-like to be and in exactly what ways. So, no, they aren't frauds because there isn't any non-arbitrary scientific definition of "Earth-like" and they don't pretend there is.

They have no clue so all they could do is pretend. As you say they have no clue of what constitutes Earth-like, because they don't even have an arbitrary definition!

Wrong; scientists define what they mean.
It is only you that has no clue.

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