Habitable Planets With Earth-Like Biospheres May Be Much Rarer Than Thought

SciTechDaily ^ | 6/26/2021 | By Royal Astronomical Society

[LibWhacker]

Habitable Planets With Earth-Like Biospheres May Be Much Rarer Than Thought

TOPICS:AstrobiologyAstronomyAstrophysicsExoplanetRoyal Astronomical Society

By Royal Astronomical Society June 26, 2021

A new analysis of known exoplanets has revealed that Earth-like conditions on potentially habitable planets may be much rarer than previously thought. The work focuses on the conditions required for oxygen-based photosynthesis to develop on a planet, which would enable complex biospheres of the type found on Earth. The study was recently published in the Monthly Notices of the Royal Astronomical Society.

The number of confirmed planets in our own Milky Way galaxy now numbers into the thousands. However, planets that are both Earth-like and in the habitable zone — the region around a star where the temperature is just right for liquid water to exist on the surface — are much less common.

At the moment, only a handful of such rocky and potentially habitable exoplanets are known. However the new research indicates that none of these has the theoretical conditions to sustain an Earth-like biosphere by means of ‘oxygenic’ photosynthesis — the mechanism plants on Earth use to convert light and carbon dioxide into oxygen and nutrients.

Only one of those planets comes close to receiving the stellar radiation necessary to sustain a large biosphere: Kepler-442b, a rocky planet about twice the mass of the Earth, orbiting a moderately hot star around 1,200 light-years away.

An artistic representation of the potentially habitable planet Kepler 422-b (left), compared with Earth (right). Credit: Ph03nix1986 / Wikimedia Commons

The study looked in detail at how much energy is received by a planet from its host star, and whether living organisms would be able to efficiently produce nutrients and molecular oxygen, both essential elements for complex life as we know it, via normal oxygenic photosynthesis.

By calculating the amount of photosynthetically active radiation (PAR) that a planet receives from its star, the team discovered that stars around half the temperature of our Sun cannot sustain Earth-like biospheres because they do not provide enough energy in the correct wavelength range. Oxygenic photosynthesis would still be possible, but such planets could not sustain a rich biosphere.

Planets around even cooler stars known as red dwarfs, which smolder at roughly a third of our Sun’s temperature, could not receive enough energy to even activate photosynthesis. Stars that are hotter than our Sun are much brighter, and emit up to ten times more radiation in the necessary range for effective photosynthesis than red dwarfs, however generally do not live long enough for complex life to evolve.

“Since red dwarfs are by far the most common type of star in our galaxy, this result indicates that Earth-like conditions on other planets may be much less common than we might hope,” comments Prof. Giovanni Covone of the University of Naples, lead author of the study.

He adds: “This study puts strong constraints on the parameter space for complex life, so unfortunately it appears that the “sweet spot” for hosting a rich Earth-like biosphere is not so wide.”

Future missions such as the James Webb Space Telescope (JWST), due for launch later this year, will have the sensitivity to look to distant worlds around other stars and shed new light on what it really takes for a planet to host life as we know it.

Reference: “Efficiency of the oxygenic photosynthesis on Earth-like planets in the habitable zone” by Giovanni Covone, Riccardo M Ienco, Luca Cacciapuoti and Laura Inno, 19 May 2021, Monthly Notices of the Royal Astronomical Society.
DOI: 10.1093/mnras/stab1357

[Fungi]

Really? An idiotic or intuitive premise?

[Fungi]

Nice pictures though—try some sourdough.

[wildcard_redneck]

Absence of evidence is not evidence of absence. Currently our level of sensing technology is only capable of detecting very large planets and can see earth size planets only under perfect circumstances and close distances.

[jonrick46]

The project, called the Solar Gravity Lens, or SGL will use Albert Einstein’s idea that said, over a century ago, that gravity can bend and magnify light—a concept known as gravitational lensing. The gravitational field of the sun will create an immense lens. It will require precise navigation, communications over long distances, and the need for a sunshade to keep our own Sun’s light from entering the telescope. A coronagraph would also be required to block the light from the exoplanet parent’s star. Getting to the focal point will be challenging but the results will be spectacular. We will see these exoplanets in great detail. Once we determine which exoplanets have promising features, how will be get there? Think the Star Trek warp drive. Scientist have discovered how we can make a warp drive possible so men can travel to distant planets in minutes. Those strange UFOs we are observing may have discovered the way to make warp drive work already.

[ocrp1982]

No. Really? The people who think this is not the case use the sheer volume of the galaxies and the number of galaxies in the universe to make the case that there are innumerable Earth-like planets. This is pure speculation. There is not one such other planet that has ever been identified.
In fact, of all the supposed Earth-like planets they thought they identified, upon closer examination, not one is even close.
Not claiming another does not exist anywhere. Just stating not one to date has been identified despite claims that there are a very great many based upon the sheer volume of stars, planets, galaxies, etc.. in the known universe.

[Nateman]

Oxygen is a reactive element. So is Fluorine. In only a very rare case has elemental Fluorine been found anywhere. Elemental Oxygen, however , is all over the place. It takes energy to split the water molecule and yet plants throw that energy away by releasing oxygen. We take it for granted but wasting energy is not something evolution would normally favor. Fortunately for animals burning that oxygen gives them enough energy to move around. It also makes fire possible. I figure oxygen filled atmospheres must be quite rare.

[who_would_fardels_bear]

Lots of star systems have multiple stars. If the stars are of similar size then the planetary orbits will be chaotic and the planets will spend large amounts of time far from and close to the stars making life nearly impossible.

If one of the stars is a red dwarf, then the radiation from that planet will regularly kill off any life that happened to get started.

If the planets are in stable orbits too far or too close to a single star then life appears impossible, from what we know of our own solar system. Even if life is able to get started under water in iced over planets, then those life forms will have no access to fire and will most likely not evolve past dolphin-like intelligence.

If a planet happens to be in a favorable orbit around a single star, then whatever intelligent life might start there will soon devolve to the point where thy consider Lady Gaga music and Superhero movies as adult entertainment. From there it is not too long to Idiocracy and societal collapse.

[The Right Edge]

... AND that’s why we have to act on “climate change”! Blah, Blah, Blah...

[a fool in paradise]

Aliens are not on Earth just to do butt stuff.

They want our planet.

[jmacusa]

Wow. That’s pretty... amazing. You went from the impossibility of life, to life barely sentient to life suffering a moral and societal collapse in just a few paragraphs.

Remarkable.

[wardaddy]

We’ve always known this actually at least since radio telescopes came bout and we could see ...

Woke science lives to denigrate God and believers

This notion is not new

Out existence is indeed unique

All the galaxy and solar system variables in place

[DannyTN]

If we get rid of all the carbon dioxide in the atmosphere, we can stop the oxygen photosynthesis and be like all the other planets.

[MadMax, the Grinning Reaper]

We now how to retitle an old 50’s book by science writer Walter Sullivan entitled “We Are Not Alone” to “We Are Alone”. Sullivan was an honest science writer and did think far ahead into what could lie in outer space.

If he was alive today, and saw the Democrats in Congress, he would definitely write a follow-up book entitled: “We Are Not Alone:Just Look at the Alien Life-Forms in Congress Today”.

[HighSierra5]

I couldn’t have said it better myself. It’s obvious to anyone with a soul how magnificent this creation is. Everything is perfectly designed for life to exist here. And you have to include the entire solar system along with our moon. Next time you kick back on one of those perfect days and take a deep breath of clean air,thank God. Thank you God.

[LesbianThespianGymnasticMidget]

There is a teeny weensy tiny problem with warp drive in
current theory. It takes ALL the energy in the universe to accomplish.

[bagster]

In fact, of all the supposed Earth-like planets they thought they identified, upon closer examination, not one is even close.

Apparently, you never watched Star Trek.

#HistoricalDocument

[bagster]

Aliens are not on Earth just to do butt stuff. They want our planet.

[fso301]

Absence of evidence is not evidence of absence. Currently our level of sensing technology is only capable of detecting very large planets and can see earth size planets only under perfect circumstances and close distances.

Understood but even with better technology, using the total number of stars as basis for assuming life as we know it must be common is a false assumption because type G stars such as out own are uncommon throughout the universe comprising roughly seven percent of the total.

So, right off the bat, you have to make a ~93 percent reduction from the total number of stars.

To be more precise, class G stars come in 12 basic variants, our sun being a type G2V.

Galaxies have what are thought to be habitable zones. Most stars within a galaxy lay outside the habitable zone. What this means is an exact clone of our solar system would not support life unless it was located within the habitable zone of a galaxy. This eliminates another huge swath of stars.

But then we must reduce the candidate field even further due to solar systems having their own habitable zone. Planets too close, or too far away from their sun will not support life.

And we are just getting started listing all the factors that reduce the cosmic field to those solar systems thought as most conducive to supporting life as we know it.

[phoneman08]

Not to mention that it took almost four billion years for simple life to evolve into complex life on this Goldilocks planet of ours.

It took billions of years for Mitochondria to establish a symbiotic with that early simple life to enable every living thing on the planet to use oxygen efficiently.