Open version: https://www.removepaywall.com/search?url=https://www.scientificamerican.com/article/how-many-planets-could-fit-in-the-solar-system/

According to research by a team of international scientists published in the Monthly Notices of the Royal Astronomical Society (MNRAS), yes, you can have more than two planets share an orbit.

Astonishingly, many more can coexist!

First, the researchers used the mathematics of orbital mechanics to simulate the physics of two Earth-sized planets orbiting a sunlike star at 150 million kilometers (the real life Earth-sun distance) and showed they can persist in such horseshoe orbits for billions of years! Then the team added more and more planets to see what would happen.

When two planets meet up with each other, they swap orbits, as is already understood. But eventually one will then approach the third planet. When it does, they swap orbits and move apart. Eventually one of those two meets up with the first planet, and the whole situation repeats. This happens with every planet-on-planet encounter.

Incredibly, the scientists found this to be true if they had as many as 24 Earth-sized planets packed into a single orbit! Twenty-four!

Still, it seems to work in the simulations; any planet can’t get very far along its path without meeting another, and when the two do so, they swap positions and continue on until the next encounter with the next planet down the line, constantly sliding around and jockeying for position.

The scientists even tried this in a simulation of our own solar system, which, they found, could support the addition of an extra couple of Earths or Venuses—or another Mercury or Mars.

Creating a system like this isn’t easy. It’s possible that a very thick ring of dust around a star could form several planets in the same orbit simultaneously, though conditions would have to be rather fine-tuned to allow that to happen. Also, planets can migrate toward and away from their host star on much grander scales as they interact gravitationally. And if enough smaller planets get tossed around by this process, they could also end up in shared orbits.

Detecting such planetary systems from Earth is possible, too. One way we find planets now is through the transit method, in which a planet passing directly in front of its star creates a mini eclipse, as seen from Earth.

If several transits occur in sequence when we should only see one for that particular orbit, that would be a sign. Also, the fact that planets in this arrangement slide along their orbit and swap positions means that their positions in that orbit change, which, in turn, changes the timing of the transits. That would be detectable, too, even if all of the planets don’t actually join the transit parade.

Delightfully, the authors of the MNRAS study speculate that there is another way to form these systems: building them on purpose. Having multiple worlds all in one orbit might be handy for interplanetary travel.

And while moving them around physically is a daunting task, a sufficiently technologically advanced alien civilization might feel that it’s worth the effort. If we ever were to find such a system, well, that would be interesting, wouldn’t it?

A moon lost in interstellar darkness may still be able to hold on to liquid water, no star required.

A modeling study suggests that some exomoons orbiting rogue planets could stay warm for billions of years, even after their host worlds are thrown out of their star systems and into the cold of deep space.

The finding challenges the familiar idea that potentially habitable worlds must receive light from a nearby star.

Instead, the study points to a different engine for habitability — heat generated inside a moon by tidal stress, then trapped by a thick hydrogen atmosphere.

Rogue planets drift through space without orbiting a star. Astronomers think many of them were thrown out of their original planetary systems during violent gravitational encounters.

When a giant planet gets ejected, the orbits of its moons can become stretched into more elongated shapes.

As the moon moves closer to and farther from its host planet, the planet’s gravity repeatedly squeezes and flexes the moon’s interior.

That process, called tidal heating, can generate a steady supply of internal heat. Jupiter’s moon Io offers a familiar example: tidal forces make it the most volcanically active body in the solar system.

Europa and Enceladus also show how internal heat can keep water-rich worlds active far from the sun.

Earlier studies had already suggested that rogue-planet moons might stay warm enough for liquid water if they built up thick carbon dioxide atmospheres. But those models ran into a serious problem. In the deep cold expected around free-floating planets, carbon dioxide can condense out of the air.

Once that happens, the atmosphere can collapse, and much of the moon’s heat escapes into space.

The new study tackles that problem by swapping carbon dioxide for hydrogen. Hydrogen is the lightest element, and in Earth’s thin atmosphere it does very little to trap heat. Under very high pressure, though, hydrogen behaves differently. When hydrogen molecules crowd together and collide, they briefly form pairs and clusters that can absorb infrared radiation.

Scientists call this process collision-induced absorption. In plain terms, a dense hydrogen atmosphere can act like a surprisingly strong heat blanket.

TRAPPIST-1e is one of the most interesting potentially habitable exoplanets we’ve discovered. It’s roughly Earth-sized, located about 40 light-years away, and orbits within its star’s habitable zone.
However, it likely experiences tidal locking, meaning one side permanently faces its star while the other remains in darkness. We also still don’t know whether it has a substantial atmosphere or liquid water.
If TRAPPIST-1e does support life, what do you think it would most likely look like? Would it be limited to microorganisms living in oceans or underground, or could more complex organisms eventually evolve?
And considering the unusual conditions around red dwarf stars, could a planet like TRAPPIST-1e ever develop intelligent life, or would its environment make that extremely unlikely?
I’m curious whether scientists and astronomy enthusiasts think TRAPPIST-1e is genuinely promising for life, or whether we’re being too optimistic about planets in habitable zones.

Open version: https://archive.is/yIYpb

Scientists believe there are planets outside our solar system where life is even more abundant and sustainable.

A few years ago, in a lab in Berlin, the astrobiologist Iva Vilović was thrilled when she observed garden cress sprouting under a light designed to mimic a “K-dwarf” star — an orange-hued star that’s cooler and slower burning than our yellow sun. To her surprise, the cress grew even faster and taller than it did under simulated sunlight.

Her results suggested that photosynthesis, the process that supplies the energy for Earth’s entire food web, can happen on planets orbiting these orange stars.

“K-dwarf light is a very, very interesting light source, and it should be considered, if not prioritized, for any type of search for extraterrestrial life, in my opinion,” said Dr. Vilović, now at the Leibniz Institute for Astrophysics in Potsdam, Germany.

In particular, alien life may thrive in the light of these stars on planets that are slightly larger than Earth, known as super-Earths. Scientists like Dr. Vilović believe super-Earths that orbit K-dwarfs might, in fact, be the liveliest places in the galaxy — perhaps even more suitable for life than here.

Scientists call these “superhabitable worlds,” planets that would allow carbon-based life to persist longer and become even more complex and diverse than on Earth.

A superhabitable world — as scientists imagine it — is about 20 to 30 percent wider and twice as massive as Earth, and is placed at the right distance from its star for water to flow on its surface.

The stronger gravity of this bigger Earth would hold on tighter to ambient molecules than Earth does, giving the planet a thicker atmosphere and a warmer and more stable climate, fueling the growth of extraterrestrial plants and animals (or their equivalents).

The super-Earth’s bigger iron core would erect a stronger magnetic field around it, better blocking cosmic radiation.

As for the superhabitable planet’s surface, picture paradise. An enlarged orb would be rounder and smoother than Earth, as its stronger gravity erodes continental shelves and fills in trenches. Water would spill evenly over its surface as shallow lakes and seas.

On Earth, tropical islands and shallow seas are among the most biodiverse habitats. Now imagine a whole world of balmy archipelagos and reefs. The islands would burst with biological activity, their diverse topographies and geographic isolation fueling explosions of distinct species.

Light would reach clear to the seafloor, powering abundant alien algae and plants to feed a booming marine ecosystem.

As for that light, it might be the orange glow of the planet’s K-dwarf star.

It was in the 2010s when astronomers began contemplating planets that are a little bigger, and a little nicer, than Earth, and where to find them.

The whole idea was spurred in part by a question from John Armstrong a professor at Weber State University in Utah, who asked in the comments section of an astrobiology seminar on YouTube: “Shouldn’t there be planets more habitable than Earth?”

That got another astronomer, René Heller, who is now at the Max Planck Institute for Solar System Research in Germany, thinking. In the quest to discover chemical signs of life on distant worlds, he thought, astronomers have focused on finding “Earth twins,” rocky, watery, Earth-size planets orbiting sun-like stars.

But when it comes to hosting life, Earth may not be the ideal archetype. After all, the fact that we’re not located at a special place in the cosmos (that we revolve around the sun, not that it revolves around us) is what the Copernican revolution was all about.

“It occurred to me that currently, humanity is looking for Earthlike planets with the same anthropocentric bias,” Dr. Heller said. “Of course, Earth is special to us. But from a universal perspective, why should Earth be a reference?”

In fact, Earth is only marginally habitable. Most astrobiologists think water must be present on a planet’s surface for life to arise there, and indeed the first bacteria appeared on Earth almost as soon as water pooled on its cooling surface roughly four billion years ago.

But if Earth were just 2 percent closer to the sun, that pooling wouldn’t have happened. Instead, all of Earth’s water would have boiled away. We got lucky. But our luck will run out. The sun is expanding and brightening. Scientists calculate that in another half-billion years or so, Earth will be too hot to sustain complex life like plants and animals.

For Dr. Heller, the hunt for more habitable worlds is about “finding out if we are alone, if we could have been found, if there’s someone to talk to,” he said.

“Although I am not, at least in my everyday life, a very spiritual person,” he added, “it’s nevertheless something that at least drives me — this question, Could there be someone?”

He contacted Dr. Armstrong, and together they wrote a 2014 paper introducing the hypothesis of superhabitable worlds, which the two envisioned as archipelago-covered super-Earths. They were proposing a new target for telescopes.

“Superhabitable worlds must be considered for future follow-up observations of signs of extraterrestrial life,” they wrote.

In the paper, Dr. Heller and Dr. Armstrong reasoned that cool, petite K-dwarfs would be better host stars for superhabitable worlds than sun-like stars because they burn through their hydrogen fuel more slowly and brighten much more gradually.

Our sun has only five billion years’ worth of hydrogen left before it will suddenly balloon and redden, becoming a red giant that will engulf the Earth. K-dwarfs, by contrast, shine steadily for tens of billions of years.

This means life on a superhabitable planet orbiting a K-dwarf has far longer to evolve into ever more complex life forms.

What kinds of life forms? We can only imagine. All we know is earthlings have grown increasingly complex and sophisticated over the past four billion years, culminating so far in human-level intelligence.

“K-dwarfs do seem to be everyone’s sweet-spot star,” said Johanna Teske, a planetary scientist at the Carnegie Institution for Science in Washington, D.C. Planets that can sustain liquid water sit closer to K-dwarfs than they do to sun-like stars, so they are easier to observe with telescopes.

Astronomers search for life on planets tens or hundreds of light-years away by looking for gases in their atmospheres that may indicate biological activity.

Current instruments, such as the James Webb Space Telescope, are mostly capable of checking the skies of rocky planets that tightly orbit tiny red stars called M-dwarfs. So far, most of these planets have been revealed as bare rocks, stripped skyless by their aggressive, nearby stars.

Probing the skies of potential superhabitable planets — namely, super-Earths orbiting at the right distances around K-dwarfs — should become feasible in future.

The first step is to find nearby candidates. Dr. Heller is a leader of the European Space Agency’s Plato mission, a space telescope launching in 2027 with the purpose of detecting potentially habitable planets, including super-Earths orbiting K-dwarfs.

“We will probably find a few of them — maybe a dozen,” Dr. Heller said. “But we won’t learn much about them.”

Follow-up observations from other telescopes should reveal more about the chemical makeup of these planets’ skies. The Webb telescope might be able to investigate the skies of some potentially superhabitable super-Earths in the coming years.

The Extremely Large Telescope, which measures 39 meters across and is currently under construction in Chile, will be capable of seeing more of them. Even more extensive and definitive observations will become possible with the Habitable Worlds Observatory, a NASA space mission planned for the 2040s.

For Dr. Vilović, the pursuit of superhabitable planets is, in part, “an idealistic dream of a world that has beautiful conditions that are not being influenced by humans in a negative way,” she said.

She thinks it’s also about a “drive to find extremes” — the most extreme version of the kind of life we know and understand.

As for whether the dream is also a reality, Dr. Vilović feels good about the odds. “I like to believe that statistically speaking, in the realm of the universe, it is likely that life exists — especially on superhabitable planets,” she said.

A leopard-spotted rock that could prove whether life ever existed beyond Earth is sitting in a tube on Mars.

NASA’s Perseverance rover grabbed up the sample, called Sapphire Canyon, from rocky outcrops on the edges of the Neretva Vallis, a valley sculpted by rivers that once flowed into an ancient lake in Jezero Crater more than 3 billion years ago.

The rover landed at the dried lakebed in February 2021 for expressly this purpose, hunting for rocks created or modified by water in the past, which would have had the best chance of preserving evidence of life.

Members of the Perseverance science team have said the Sapphire Canyon sample, about the size of a chalk stick, is exactly the type of rock they hoped the rover would discover.

“This is the first time I think we’ve found something that qualifies as a ‘potential biosignature’” on Mars, said Adrian Broz, a member of Perseverance’s science team and a postdoctoral researcher in the Planetary Surface Processes Lab at Purdue University in Indiana.

“It’s currently sealed inside of Perseverance rover’s chassis, and it sits there quietly and awaits return to Earth.”

But the sample might not make it to our planet, at least not anytime soon.

The Mars Sample Return program, a joint venture by NASA and the European Space Agency to ferry the promising cache back to Earth, attracted intense scrutiny for its high price tag and complex design.

After sinking billions of dollars into the endeavor, NASA paused and began reassessing the program in 2024 before canceling it entirely — with no clear alternative in sight.

“While Perseverance’s samples remain safely stored on Mars, NASA is exploring a range of potential return options that could offer simpler and more affordable approaches than the original Mars Sample Return plan, including possible commercial or international contributions,” the agency said in a statement shared with CNN in July.

NASA’s leaders still haven’t revealed a path forward.

I have basically no background in biology. I have spiky depth of knowledge in astrophysics, and a degree in electrical engineering, so please don't rip me to shreds if the following premise is objectively impossible.

I am writing a trauma epic into humanity's far future (30k years from present day) utilizing mostly known science to yield plausible technology in my world building for this. The only handwave being the ontological transfer for global consciousness downclocking within an ultra high relativeistic spaceships to enable human scale rapid transit at interstellar distances. I have built my world on a hybrid of loud and landaur engineering principles.

In chapter 9, far off the interstellar laser highway infrastructure - my protagonist ends up on the only earth-like colonized world in the whole story (most are toxic, vacuum, hostile, etc.).

I have decided to craft this currently unnamed world as a world that is only 45% covered with deep oceans (up to 29km deep in trenches). The land is a super contenent that stretches over both poles. The land has flora (plant like and tree like structures except its not wood its a chitonous-like material.

The haunting thing is: there is no land fauna. Only ocean fauna but not near the shallow shores.

Because I am about maximum plausability in my world building; is such a planet possible by any such mechanism, no matter how bizarre?

World specs are:

Atmosphere: 1.02 Atm

Gravity: 0.89g

Atmospheric Composition: 78.5%, nitrogen, 20.5% oxygen, 0.9% argon, 0.05% CO2, 0.05% trace gases

Land to Water Ratio: 55% L to 45% W

Maximum peak: 16.88km

Minima Trench: 29.1km

See also: The publication in the Monthly Notices of the Royal Astronomical Society.

Hi all,

I'm a CC student seeking an A.S. in biology at the moment, with intention to transfer into a biochemistry B.S. + astrophysics (or geology--uncertain as of right now) minor/dual major soon (again, I'm undecided, and wouldn't mind input here).

Not accounting for research/internship experience, is this a good step in the right direction towards an astrobiology PhD?

I'm particularly interested in UWashington's astrobiology graduate program, if anyone has experience with them! I've had a keen interest in extremophile and exoplanet research for the past near decade.

I'm well aware astrobiology is incredibly lucrative, and chose biology as it's a long-term passion of mine. Just curious on what I could do, and where I could go to strengthen my background.

A  century-old mystery in Venus’s clouds just became more intriguing, as scientists calculated how strongly the unidentified material behind its dark ultraviolet patterns must absorb light.

The results sharply narrow the possibilities and could help future spacecraft determine whether the mysterious substance is organic, inorganic, or something unexpected...

Scientists have placed new limits on the mysterious substance responsible for Venus’s dark ultraviolet cloud markings, which have puzzled researchers for about a century

Venus appears pale yellow in visible light, but ultraviolet images reveal dramatic dark and bright patterns moving with the planet’s upper sulfuric acid clouds. Scientists have known about these markings for roughly a century, yet the chemical identity of the material responsible—the “unknown absorber”—remains unresolved.

An international research team has now placed new quantitative constraints on the properties of this mysterious absorber.

By combining observations of Venus with radiative-transfer modeling, the researchers estimated how strongly the liquid inside Venus’s cloud droplets would need to absorb light to reproduce the planet’s observed ultraviolet and blue reflectance.

The study, published in Astrobiology, approached the mystery from a new perspective. It used a model to answer a question posed by lead author Dr. Jan SPACEK: If we were to collect Venus’s cloud droplets into a spectrometric cuvette, how would the re-formed bulk liquid appear?

Scientists may have found a clue to one of the biggest mysteries surrounding the origin of life: how fragile RNA molecules could gather and survive before cells existed.

New research shows that RNA is unusually good at assembling into tiny liquid-like droplets that concentrate molecules and can harden into protective, gel-like structures.

Remarkably, much of this behavior may come down to a single oxygen-containing chemical group that RNA has but DNA lacks.

I’m a high school senior trying to figure out what I want to study in college. I honestly don’t know if I want to become a doctor, work in a lab, or pursue research, but I know that I love biology. I’ve realized, though, that I enjoy learning about astrobiology much more than general biology, especially topics involving the origins of life, extremophiles, and the possibility of life beyond Earth.

I’m considering majoring in astrobiology because it’s something I’m genuinely excited to learn about, but I’m worried about limiting my career options. Would it be possible to major in astrobiology while completing the prerequisites for medical school? And how versatile is an astrobiology degree if I eventually decide to pursue laboratory work or research instead of medicine?

I’d love to hear from anyone who studied astrobiology or a related field, especially those who were also considering multiple career paths when choosing their major.