Tag: alien civilizations

ARE ROGUE WORLDS THE ULTIMATE ABODE FOR LIFE?

On By AlessandraIn Extrasolar Planets, S.E.T.I.1 Comment

The search for extraterrestrial life has captivated humanity for centuries. Countless questions arise in our quest to discover if we are alone in the vast universe. The Drake Equation, a mathematical formula introduced by astronomer Frank Drake in 1961, attempts to estimate the number of civilizations within our Milky Way Galaxy. However, recent scientific discoveries have unveiled a new intriguing possibility – rogue worlds. These wandering bodies, expelled from their original solar systems, may hold the potential for harboring life. In this blog post, we will explore the fascinating intersection of the Drake Equation and the enigmatic realm of rogue worlds, exploring the tantalizing notion of life beyond our home planet.

The original form of the equation is the following:

N = R* f(p) n(e) f(i) f(l) f (c) L

• N is the number of civilizations trying to communicate with us right now;

• R* is the rate of star formation in stars per year;

• f(p) is the fraction of those stars which have planetary systems;

• n(e) is the number of Goldilocks (i.e., Earth-type) planets in a planetary system);

• f(l) is the fraction of habitable planets that are inhabited;

• f(i) is the fraction of inhabited planets that possess intelligent technological civilizations;

• f (c) is the fraction of intelligent technological civilizations that choose to emit detectable signals;

• L is the length of time signals will be sent.

The first three factors are astronomical, the fourth and fifth are biological, and the last two factors are social. There are several issues with the equation. Among these:

(1) The uncertainties are large enough for the astronomical factors and increase as one progresses from the astronomical to the biological to the social.

(2) Most factors depend on theoretical insights of star and planet formation, new discoveries about exoplanets, and varying subjective opinions on the evolution of life and intelligence. The presumed longevity of civilization must also be taken into account.

(3) The equation has many hidden assumptions: a uniform star formation rate (SFR) over the Galaxy’s lifetime and a steady state of civilization birth and death. 

(4) No matter what value one chooses for R*, the assumption is always that a habitable planet must have a star. However, rogue worlds (bodies that have been thrown out of their own nascent solar system) wander around the Galaxy unattached to a star.

This last item has recently awakened great interest in the scientific community.

Theoretical calculations (Imagined Life, by James S. Trefil and Michael Summers, 2019) suggest that:

“[…] the number of rogues might be between twice and thousands of times the number of conventional planets. Interstellar space must be littered with them!”

Also, rogue planets need not be uninteresting ice balls with no life and energy. Lacking direct radiation from a star, a world can be heated by the residual power from its formation and the radioactive decay of elements in its interior. If provided with one or more moons, the planet can draw energy from a process known as tidal heating (which is responsible for the subsurface oceans on some of Jupiter and Saturn’s moons).

All in all, rogue planets can be compared to (Imagined Life by James S. Trefil and Michael Summers, 2019):

“[…] houses whose lights have been turned off but whose furnaces are still operating.”

Interestingly, rogue planets had been predicted as early as the 1930s by American horror and S.F. author Howard Phillips Lovecraft.

In his short story: The Haunter of the Dark, he wrote:

“[…] remember Yuggoth, and more distant Shaggai, and the ultimate void of the black planets… […].”

When the planet Pluto had just been discovered by Clyde Tombaugh (1906-97) at Lowell Observatory (Flagstaff, Arizona), he wrote another short story: The Whisperer in Darkness.

Here are a few quotes: 

“[…] Their main immediate abode is a still undiscovered and almost lightless planet at the very edge of our solar system – beyond Neptune and the ninth in distance from the [S]un. It is, as we have inferred, the object mystically hinted at as ‘Yuggoth’ in certain ancient and forbidden writings; […] I would not be surprised if astronomers become sufficiently sensitive to these thought-currents to discover Yuggoth when the Outer Ones wish them to do so. But Yuggoth, of course, is only the stepping-stone. The main body of the beings inhabits strangely organised abysses wholly beyond the utmost reach of any human imagination.”

And also:

“[…] Those wild hills are surely the outpost of a frightful cosmic race – as I doubt all the less since reading that a new ninth planet has been glimpsed beyond Neptune, just as those influences had said it would be glimpsed. Astronomers, with a hideous appropriateness they little suspect, have named this thing ‘Pluto.’ I feel, beyond question, that it is nothing less than nighted Yuggoth […].”

What would life be like on a rogue planet?

According to Imagined Life, by J.S. Trefil and M. Summers:

“It’s dark. Not midnight-on-a-side-street dark, but trapped-in-a-cave dark. And no wonder—there’s no sun in the sky, for this is a rogue world, one that circles no star. There is a moon up there somewhere, but without a source of light for it to reflect, it’s just a darker patch in the sky. Whatever life forms live on this planet had better be able to see in infrared because there’s simply no other light to be had. You’re wearing infrared sensors, fortunately, and you spot a few of these creatures scurrying back to the planet’s subterranean tunnels, where they can bask in the heat emanating from the planet’s interior. […]”

Life on a dark planet has been described by British author Arthur C. Clarke in his 1950 short story: A Walk in the Dark:

“[…] Here at the edge of the Galaxy, the stars were so few and scattered that their light was negligible. […]” 

“[…] Here at this outpost of the Universe, the sky held perhaps a hundred faintly gleaming points of light, as useless as the five ridiculous moons on which no one had ever bothered to land. […]” 

“[…] No one could deny that the tunnels out in the wasteland were rather puzzling, but everyone believed them to be volcanic vents. Though, of course, life often crept into such places. With a shudder, he remembered the giant polyps that had snared the first explorers of Vargon III […]

The Drake Equation is not meant to give a precise answer but to stimulate scientific discussion and exploration. It is based on several factors that affect the likelihood of finding intelligent life, such as the rate of star formation, the fraction of stars with planets, the fraction of planets suitable for life, and the fraction of civilizations that develop radio technology. Each factor is multiplied by the previous one, resulting in the number of detectable civilizations in our galaxy. However, many of these factors are uncertain, and different assumptions can lead to different outcomes. For example, some estimates suggest that there could be millions of civilizations in our Galaxy, while others suggest that we might be the only one.

According to a recent study, under the strictest set of assumptions, where life forms between 4.5 billion and 5.5 billion years after star formation, there are likely between four and 211 civilizations in the Milky Way today capable of communicating with others, with 36 the most likely figure. Another study yielded two main results: an optimistic one and a pessimistic one. In the optimistic situation, the researchers suggested the aforementioned 42,777 communicating extraterrestrial intelligent civilizations (CETIs) with an error margin of plus 267 and minus 369, and they would need to survive 2,000 years on average to communicate with us.

The Drake Equation is a fascinating way to explore the possibilities of extraterrestrial life and communication. It helps us understand what we know and don’t know about our place in the universe. It also inspires us to keep searching for signs of other civilizations and to wonder what they might be like.

Read more about this topic in this post and this other post.

IS THE UNIVERSE AN AWFUL WASTE OF SPACE?

On By AlessandraIn Extrasolar Planets, S.E.T.I.

“The universe is a pretty big place. If it’s just us, it seems like an awful waste of space.” 

This quote is attributed to Carl Sagan from his novel Contact (1985). It is often interpreted as reflecting Sagan’s optimism and belief in the possibility of extraterrestrial life. He strongly advocated for the search for extraterrestrial intelligence (SETI) and believed that the discovery of intelligent life beyond Earth would have profound implications for humanity.

In other words, Sagan suggested that if the Universe is so vast and we are the only intelligent life in it, it would be a shame to waste all that space on just one civilization.

A recent estimate (Conselice C.J. et al. 2016) says the observable Universe contains two trillion – or two million million – galaxies. Of course, this is a huge number, which math buffs can probably better appreciate if I translate it into scientific notation:

two trillion = two million million = one thousand billion = 2 x 1012

Even if we neglect 99.9999% of the Universe and consider only the Milky Way, we are left with a staggering number of about 100 to 400 billion stars.

Of course, these hundreds of billion stars vastly differ in age, mass, and chemical composition.

According to the stellar luminosity function:

A small percentage of stars are massive, young, and very bright (the so-called O, B, and A spectral types, with colors ranging from ultraviolet/white to blue);

A relatively large number of stars are medium-sized (the F and G spectral types, yellow to orange in color). Our “dull” Sun is one of them;

The majority of stars are small, old, low-mass stars (the K, M spectral types, a.k.a. red dwarfs);

Many stars are brown dwarfs (dark, spherical lumps of stellar material that never reached the star stage).

In the last few decades, roughly from the early nineties, it has become known that most, if not all, stars possess planets. Our Sun has eight major ones (excluding the KBOs or Kuiper Belt Objects). The former planet Pluto, now demoted to “dwarf planet,” is one).

Just like stars, planets also show a vast range of types.

I found a helpful classification in Imagined Life: A Speculative Scientific Journey among the Exoplanets in Search of Intelligent Aliens, Ice Creatures, and Supergravity Animals by James S. Trefil and Michael Summers. We can envisage the following kinds of exoplanetary environments as the most promising for alien hunters:

(1) Goldilocks Planets: planets like Earth, located at a distance from their star that allows them to have oceans of liquid water on their surface for extended periods;

(2) Subsurface Ocean Worlds: planets on which oceans of liquid water are bounded below by solid rock and above by ice. Examples in our solar system: the planet Pluto and several moons of Jupiter, Saturn, Uranus, and Neptune);

(3) Rogue Worlds: planets without a parent star. Such planets have been ejected from their solar system of origin and now wander through space. An example is OTS 44, a free-floating planetary-mass object located at 550 light-years, with approximately the mass of Jupiter;

(4) Water Worlds: planets with no dry land at all. That’s what a post-apocalyptic Earth would look like. (See, e.g., Kevin Reynolds’ 1995 movie Waterworld);

(5) Tidally Locked Worlds: planets that always present the same face to their star, much as the Moon does with Earth. Their peculiarity is that one side is perennially hot, while the other is an eternal Antarctica;

(6) Super-Earths: planets whose size falls between Earth and Neptune. Given their mass, the main characteristic of these planets is their intense gravity. Creatures must live in oceans or evolve a strategy to deal with this crushing force. A nice fictionalization of this is Edmond Hamilton‘s Starwolf series (1967-68), where Morgan Chane, the son of a human missionary family, grows up in a heavier-than-Earth world.

If these worlds exist, and there’s a tiny chance some might be inhabited, well… I want to see them. I’ll probably never do it in person (sadly, I’m not an astronaut). However, I can still dream about them, hoping someone will get there someday.

I wish someone to be able to say, just like the replicant Roy Batty in Ridley Scott’s 1982 movie Blade Runner:

“I’ve seen things you people wouldn’t believe.
Attack ships on fire off the shoulder of Orion.
I watched C-beams glitter in the dark near the Tannhauser Gate.
All those moments will be lost in time, like tears in the rain.
Time to die.”

Read more about this topic in this post and this other post.