WATER VAPOR GIVES SCIENTISTS THE SPOT OF LIFE IN THE UNIVERSE
After 30 years of analyzing other solar systems, we have finally found water on a planet that could support life, but scientists have even more ambitious plans: They want hard evidence that life thrives and breathes on other planets.
There are two possibilities: either we are alone in the universe or we are not.
Both options are equally terrifying. This quote from science fiction author Arthur C. Clarke nicely sums up our current knowledge of life in the universe.
We have no hard evidence for life out there, but now humans have found about 4,000 planets in other solar systems, and as a result, astronomers believe that life can indeed be found elsewhere.
And for the first time, we now have the means to find it, if it exists.
Scientists have been mapping the orbits, sizes and masses of distant planets for the past 30 years, and now a lot of work begins to better analyze all this data.
One milestone was reached when scientists analyzed observations from the Hubble Space Telescope and found signs of water vapor in the atmosphere of one planet in another solar system.
Yet another planet had emerged that could be habitable since it orbits its star at a suitable distance and is similar in size to Earth.
Astronomers have thus found significant indicators that allow them to enter a true golden age in terms of the search for life in the universe.
NASA has found an Earth-like planet – see what it looks like here:
Where could life be?
In 1993, astronomer James Kasting defined the term “habitable zone”. Liquid water is the basis of all life as we know it.
Therefore, said Kasting, we must determine the distance from a star where the temperature implies that the water neither evaporates nor freezes.
This viable area was nicknamed the “Golden Grizzly Zone” after the adventure where the porridge could not be too hot or too cold.
The definition has since served as a benchmark for how scientists analyze other solar systems for life.
Two years after Kasting’s paper was published, astronomers discovered 51 Pegasi b, the first exoplanet orbiting a star similar to our Sun.
Light reveals water on a planet
Using the Hubble Space Telescope, astronomers have detected the starlight filtering through the atmosphere of a planet called K2-18b. The light shows signs of something scientists have dreamed of: water molecules.
The planet was discovered using a method where astronomers measure deviations in the wavelength of starlight caused by the planet’s gravitational pull on its star as it orbits it.
From these deviations of the light, the mass of the planet can be calculated. The more mass, the more part of the light “stretches” out and becomes redder, while part of it “compresses” and becomes bluer.
The gold bar area is found
Since 1995, larger and sharper telescopes have been continuously built on the ground, and advanced space telescopes have also been sent into space in the search for distant planets.
Astronomers have been able to determine not only the masses of planets, as was the case with 51 Pegasi B, but also their diameters.
1 = Too cold. 2 = Viable zone. 3 = Too cold.
Life can only thrive in the “Goldilocks Zone”
The habitable area close to a star is also called the “Golden Bear region” after the fairy tale of Goldbrá and the Three Bears. The name refers to the fact that a planet must not be too hot or too cold for water to be liquid so that life can form and develop, just as happened here on Earth. If the planet is too hot, all the water will evaporate. If the planet is too cold, the water freezes and inhibits the development of life. A planet’s temperature is determined by its distance to its star and the star’s strength. The hotter the star is the further away it is to find a habitable zone.
1 – Too hot
The temperature is so high that water would evaporate on the surface of planets in this region.
2 – Viable zone
Just like on Earth, the distance to the star is just right for water to float on the surface.
3 – Too cold
Water cannot float on the surface but can be frozen
The CHEOPS space telescope, which was launched in December 2019, is precisely to confirm the diameters of the planets that have already been discovered with the help of ground-based telescopes.
The diameter can be found using the transit method, where scientists measure how much the star’s light intensity decreases when the planet passes in front of it.
When astronomers know both the planet’s mass and size, they can calculate its density and thus whether the planet is, for example, a gas giant, such as Jupiter and Saturn, or a rocky planet such as Earth and Venus.
Currently, about 4,000 exoplanets have been discovered by telescopes such as Hubble, Kepler and Spitzer. Astronomers have a detailed record of planets, and the “Goldilocks Zone” is no longer just a concept that originated in the world of fairy tales, but a well-established phenomenon.
The CHEOPS space telescope is supposed to measure the radii of planets so that astronomers can calculate their densities.
Water vapor opens a new era
In September 2019, astronomers added a remarkable piece to the puzzle of life in the universe when a new study demonstrated water in the atmosphere of the planet K2-18b.
The planet is about 110 light-years away from our solar system and has eight times the mass of Earth and is therefore called a super-Earth.
The planet is close to its star and it only takes 33 days to make a full circle while the temperature of the globe is moderate as the star is much fainter than our sun.
And when astronomers studied K2-18b, with the help of the Hubble Space Telescope, they saw that some of the light from its star was absorbed by molecules as it passed through the planet’s atmosphere.
The wavelengths of the light that “disappeared” along the way match well with a well-known molecule that can absorb light – H 2 O.
Scientists had found water vapor in the atmosphere, and further analysis suggested that rain may be present on K2-18b.
This analysis of the presence of water vapor further confirms the concept of gold melt zones.
Although scientists are still uncertain about the conditions for life on K2-18b, the encounter marks a turning point. And thus the beginning of a new era in space research.
Now scientists are zooming in on planets that are so similar to Earth that it is possible with scientific knowledge to find signs of life there.
We have thus moved from mapping “golden planets” to making hard observations that will determine which of Arthur C Clarke’s two possibilities is correct: Are we alone – or are we not?
FIVE PLANETS WHERE LIFE COULD USE IT
Astronomers have a catalog of promising planets, as well as new, more powerful telescopes to probe for signs of life in more detail within a few years.
A super-Earth receives 6% more light than Earth
Only 12.4 light-years away from Earth is the planet GJ 273 b, which orbits a red dwarf called Luyten’s star. One year on the planet lasts 18.6 days, and the distance to the star is about a tenth of the distance between the Earth and the Sun. Nevertheless, the planet receives only 6% more sunlight than Earth, as Luyten’s star is dim. Therefore, GJ 273 b, which is a so-called super-Earth and weighs almost three times more than Earth, might be habitable if the planet has both an atmosphere and water.
A volcanic planet is an old cousin of Earth
Kepler-452b is an Earth-like exoplanet orbiting a star similar to our Sun. The planet takes 385 days to travel around its star and it is only 5% further away than the Earth is from the Sun. Kepler-452b is probably a rocky planet and experts believe that clouds and volcanoes may be found on it. These two could provide good conditions for life as it points to a planet that constantly emits gas, has an atmosphere and a constant temperature.
The newly discovered planet most closely resembles Earth
In the summer of 2019, astronomers at Göttingen University revealed that they had found two planets orbiting the dwarf star Teegarden’s Star at a distance of 12.5 light years from Earth. The one that is closer to the star and is called Teegarden b has attracted people’s interest. The planet is so close to its star that it only takes 4.9 days to complete one orbit around it. Until now, Teegarden b is the most Earth-like exoplanet in terms of, for example, diameter, density and surface temperature.
Seven sister planets can host life
In 2016, astronomers revealed the astonishing discovery of seven Earth-like exoplanets orbiting the same star, Trappist-1, just 40 light-years from Earth. Of these seven planets, astronomers at the University of Washington estimate that the fourth – Trappist-1e – is the most likely to have a climate similar to Earth’s. Trappist-1e is likely in a coordinated orbit around its star, which means it has a persistent day side and a persistent night side. The chances of finding liquid water – and thus life – are greatest at the interface between the two sides of the planet, where the temperature is neither too high nor too low.
BINOCULARS SEARCH FOREIGN CULTURE WORLDS
Soon we will be able to observe everything from the light of plants to solar cells and astronauts from alien cultures. Astronomer Avi Loeb believes that in the near future we can use new telescopes to sharpen our view of life in other solar systems.
Imagine a future where the question of whether life exists outside our solar system has been answered.
It is proven that life is found on thousands or millions of planets in space.
Methane gas from the digestive systems of primitive animals has been detected by sophisticated telescopes, and the light from spaceships of advanced civilizations has been seen.
Does this sound like hellish science fiction? 58-year-old Avi Loeb doesn’t think so at all. He is a distinguished physicist, astronomer, and fellow at Harvard’s Institute for Astronomy.
“We don’t know if there’s life elsewhere,” Avi Loeb says at the beginning when Living Science catches him on the phone in Boston.
“But we know that the actual conditions on the billions of planets in the Milky Way alone are similar to those here on Earth.”
And our nebula is just one of thousands of billions in the visible universe. Therefore, I think it is arrogant to state that we are so special and that the conditions on earth cannot be found anywhere else.
I find it completely natural that life as we know it can be found elsewhere in space – and even life that is far more advanced.”
The technological capabilities of aliens make their mark.
The most obvious sign of advanced societies may be their technological capabilities. Astronomers plan to look for so-called technological indicators – signals such as radiation from spaceships, atmospheric pollution and even street lighting in large cities on distant planets.
Intelligent aliens pollute the atmosphere
Greenhouse gases are chemical compounds between chlorine, fluorine and carbon and are formed here on earth in significant quantities through industry. Therefore, high levels of greenhouse gases in the atmosphere of a distant planet may be indicative of cultural societies that have reached a certain level of technological capability.
Street lighting reveals alien cities
The light from a major city like Tokyo would be visible if the Earth were studied from the edge of the solar system with one of our largest existing telescopes. Astronomers believe that we can use the next generation of powerful telescopes to mimic the illumination of the night side of planets in other solar systems.
Spaceships emit a strong light
Current rockets and spaceships are powered by chemical combustion, but advanced civilizations will probably use directed energy propulsion to achieve higher speeds. A powerful laser beam is fired at a light magnet and rapidly propels the vehicle forward. This powerful light from the laser can be detected with a telescope.
It’s not just that life is found out there, Avi Loeb believes, he also explains that now we’re starting to gain the technological ability to find signs of extraterrestrials.
With this, astronomy can take a giant leap in the search for life in space.
From the discovery of the first exoplanets about 30 years ago until today, we have been observing whether planets “can” have liquid water and also whether they “can” be habitable.
Now we zoom in and look for hard life signs. No more ‘can’ – now it’s about ‘are’: Is there life on this planet?
According to Avi Loeb, numerous new telescopes and advances in technology will provide us with the answer.
Is there life out there and if so: Where? Here are the ideas of renowned astronomer Frank Drake:
Also called the “father” of the search for intelligent life in the universe, astronomer Frank Drake has been an ardent advocate since the 1960s of pointing telescopes into space to find signs of advanced civilizations.
New telescopes sharpen the view
Our knowledge of exoplanets has grown a lot over the past few decades, but we still only have a vague idea of what they look like.
Our telescopes are not enough because of the vast distances in the universe. Light from distant planets is difficult to capture, especially since they are easily lost in the light of their stars.
After the discovery of water vapor on the distant planet K2-18b, astrophysicist Ingo Waldman explained to The Verge as an example how difficult it is to study a planet from 110 light years away: It is equivalent to being in New York and trying to determine the color of the wings of a flying moth for the light from a London floodlight.
An astronomer believes in life in the universe
Abraham “Avi” Loeb (b. 1962 in Israel) became a doctor in astrophysics at the age of 24 and is today an astronomer and administrator at the Institute for Astronomy in Harvard. He is well known for his fight for more funding to be given to the search for life, and especially for life outside our solar system. Avi Loeb believes that it is very arrogant to think that we humans on earth are alone in the universe. He has published four books and over 700 research papers on life in space and black holes. In 2012, Time Magazine named him one of the 25 most influential people in space science.
But the next generations of powerful telescopes will soon provide astronomers with new possibilities to better study the planets.
In Chile, the Vera C. Rubin Observatory (VCRO), for example, from 2022 is to build a detailed photo album of the night sky by taking pictures of it over a ten-year period.
The telescope is expected to discover a host of new exoplanets, and from 2025 the 39.4 meter European Extremely Large Telescope (ELT) will be able to study the planets in more detail.
The diameter of the ELT’s largest mirror is four times that of the current largest ground-based optical telescope.
And into space we have sent up the James Webb Space Telescope, which has a mirror with a diameter of 6.5 meters, which is much larger than the predecessor Hubble with its 2.4 meters.
In addition to having a mirror that can capture more light, the James Webb Telescope is designed to detect light at infrared wavelengths, unlike the Hubble Telescope, which detects ultraviolet and visible light.
Therefore, the James Webb telescope is more suitable for studying the atmospheres of distant planets.
Molecules testify to life
With the James Webb Space Telescope in Earth orbit, astronomers around the world can scrutinize the atmosphere for signs that we know from our own planet that life leaves behind.
For example, plant life’s photosynthesis and animal respiration create distinct cycles of gas that can be measured.
Astronomers call these signs signs of life, and the signs of life can – apart from, for example, oxygen from the photosynthesis of plants – be methane gas that originates from animals.
With the help of the James Webb telescope, scientists plan to rely on a high-precision optical spectroscope.
When the light from a star passes through the atmosphere of a distant planet and then reaches us, it changes along the way.
Some of the light is refracted, while some is absorbed by molecules in the atmosphere.
Certain molecules absorb light at certain wavelengths, so the composition of the light reveals whether certain molecules are there.
Molecules in the atmosphere bear witness to plant and animal life
Astronomers have found Earth’s “fingerprints” in the form of a special mixture of gas in the atmosphere. These fingerprints can be used for distant planets teeming with life.
1 – Water suggests possible life
H 2 O is dipolar, which means that the molecule can bond with many other molecules. Water can, for example, dissolve salt and mix nutrients and minerals that can travel through the cells of organisms with the help of the liquid.
2 – Oxygen is the king of the vital signs
Oxygen reacts easily with other molecules. Therefore, a lot of it is needed for it to be maintained in the atmosphere. On earth, the oxygen is renewed with the help of the plants. With infrared telescopes we can detect signs of oxygen in the atmospheres of distant planets.
3 – Methane can come from animals
On Earth, methane in the atmosphere mainly comes from the digestion of living things, from termites to microbes in the guts of marine animals. Methane in the atmosphere of a distant planet can therefore be a sign that life can be found there.
And we shouldn’t be content to find either oxygen or methane, explains astronomer Avi Loeb.
For example, if astronomers manage to measure the presence of both oxygen and methane in the atmosphere, this will be strong evidence of life.
The explanation is that methane is a so-called reducing gas that over time will remove oxygen from the atmosphere, unless the oxygen is continuously renewed, for example by plant photosynthesis.
A team of scientists at McGill University in Canada has studied the spectrum of light that can be read from the gas in the Earth’s atmosphere.
Thus they have discovered the “fingerprint of the earth”. This spectrum covers Earth’s mixture of water, methane, oxygen and carbon dioxide.
Astronomers can use the fingerprint for comparison when studying the atmospheres of distant planets.
Starlight reveals the breath of life
Materials indicative of life can be seen by analyzing the atmospheres of distant planets with a spectroscope. When a planet passes in front of its star, as seen from us, it will block some of the light, but other light will travel outside with the planet while a small part of it passes through the atmosphere before reaching Earth. On its way through the atmosphere, the light encounters molecules in different gases, and the variability of the molecules means that they absorb light at different wavelengths. When scientists analyze the atmosphere of a distant planet, they look for the wavelengths in the light spectrum – from ultraviolet to visible and infrared light – where there is the greatest drop in light intensity. Every molecule – for example water or oxygen – has its own so-called absorption spectrum, which is a series of small gaps spread over the light spectrum where the molecules absorb the most light. This can be read analytically.
Solar cells light up at night
The limit of life in astronomy is becoming an increasingly popular area of research. But Avi Loeb explains that some experts have already gone further than focusing on atmospheres and, for example, they plan to look for light from plants in the oceans of distant planets, because perhaps the vegetation there emits red light when ultraviolet light hits it from a star – a phenomenon which is called bioluminescence and is well known from our own plants.
Astronomers also call the light of the plants the “red edge” because of the color of the light, and this can also be found on a distant planet.
“We can look for this same red edge on planets orbiting other stars that may indicate the presence of vegetation on the surface,” explains Avi Loeb.
If we detect light from a plant, that alone will be a monumental achievement. But Avi Loeb believes that the search for life needs to be more ambitious than that: We should look for intelligent aliens.
For example, astronomers can use the same principle that applies to the “red edge” to search for solar cells on exoplanets.
If an extraterrestrial civilization uses solar cells as we know them, the cells will reflect light at shorter wavelengths than plants, thus providing an “artificial edge” that is more bluish than red.
“That would indicate life with intelligence, and for such life we could see the signs of life from a greater distance because they may be more powerful,” says Avi Loeb who is even thinking about a specific distant planet: Proxima b.
Self-luminous corals reveal life in the oceans
On land, corals convert harmful ultraviolet light from the sun into visible light that can be seen from great distances. By searching for this phenomenon called bioluminescence, we can find living things in the oceans of alien planets.
Coral absorbs light
Corals on Earth contain proteins to protect against the sun’s harmful ultraviolet rays and convert them into visible light. The same phenomenon can be found on distant planets, for example in the Milky Way, where a large part of the stars are red dwarfs that often emit ultraviolet flares.
Ultraviolet light converted to visible light
Photons from UV light reach the coral’s fluorescent molecules, which excite electrons – they gain energy and move to a higher energy level. When the electron falls back to its previous position, it emits energy in the form of photons with the same wavelength as visible light.
A telescope captures the light
Experts believe that the ELT’s upcoming telescope, which will have a 39-meter-wide mirror, can capture light from corals on distant planets. The ELT is ideally suited for this task as it will be the largest telescope built to capture visible and infrared light in the wavelengths emitted by corals.
The planet orbits the Sun’s neighboring star, Proxima Centauri, but is approx. 20 times closer to its star than Earth is to the Sun.
However, Proxima Centauri shines much fainter than our star.
This small distance to the star means that the planet is locked in a fixed rotation with the star so that, just like the moon, it has a dark side and a day side.
“If there is a civilization on the planet, it may have built solar cells on the day side to generate current to illuminate the darkened side or transfer heat.”
And one can easily find this out by finding deviations in the amount of light emitted by the planet, compared to the amount of light in the situation where the planet would have a completely darkened night side,” says Avi Loeb.
Lost stars may be alien cultures
Scientists have compared the starry sky in the middle of the last century with images taken by telescopes in the last five years and mapped all the stars that are visible in the old images but not in the new ones. They point out that the stars may have collapsed, but also offer the explanation that alien civilizations may have built massive structures in space that shadow the star. Among other things, they mention the so-called Dyson sphere – a “shell” consisting of solar cells around a star to capture its energy.
Street lighting across the universe
Avi Loeb knows that many astronomers criticize him for coming up with such unrealistic theories.
But he doesn’t care. He cites black holes and gravitational waves as examples of the fact that science can only confirm theories decades after they were proposed.
He himself put forward a theory in 2011, when he and his colleague Edwin Turner of Princeton University published a paper in which they calculated that the light from Tokyo at night could be seen by the Hubble telescope from the Kuiper Belt – a distant belt of meteors and asteroids which is about 100 times further away from the sun than the earth.
In the same article, the two scientists discovered that the light from, for example, a high-tech civilization – or rather, the way the light fades when the distant planet moves away from us – can be described by a completely different equation than the one that applies to the light of stars that is reflected naturally from the surface of planets.
Conventional knowledge in the field dictated that the equations would be the same, but with the paper, Loeb and his colleagues demonstrated that it is at least theoretically possible to distinguish between artificial and natural light:
“When people think they already know the answer, they don’t investigate whether it’s actually correct,” says Avi Loeb.
Astronomers boost the search for life:
In recent years, scientists have offered breakthrough discoveries and innovative methods in the search for life in space. In 2019 , astronomers at University College London discovered water for the first time on an Earth-like planet orbiting its star in the so-called golden zone, where it is neither too hot nor too cold for water to remain liquid. And the golden zone does not only apply to distances to stars , says a group of scientists from Harvard University. It also applies to the sizes of planets. They must not be too small and neither too large. Astronomers at Cornell University in the United States plan to search for luminous corals on distant planets, and NASA is now turning its attention to how we find technological civilizations in the universe.
Spacecraft emit flashes of light
Maybe we don’t have to look to such far-off places to find signs of high-tech extraterrestrials.
Perhaps they have come to us. On October 19, 2017, astronomers detected a mysterious object named ‘Oumuamua, passing through the solar system.
The object had an acceleration normally associated with comets.
But the astronomers couldn’t find any tail on the “comet,” and as a result, Avi Loeb wondered if the acceleration could come from a light magnet.
Then radiation pressure from a light source – for example a laser beam – is used to propel the spacecraft forward by sending the light to a reflecting magnet.
The technology includes the potential to propel spacecraft much faster than with modern rockets.
Perhaps, says Loeb, an alien culture has already mastered this technology, and ´Oumuamua would be a spacecraft from advanced beings.
In any case, we should be looking for signs of halos and similar phenomena—for example, with the upcoming Vera C. Rubin Telescope.
“If some beings possess such a powerful beam of light for such a light magnet, some of the light will possibly leak outside the magnet, and then we could see it if we look in that direction.
It would appear as a powerful flash of light for a short time and we could look for it,” says Avi Loeb.
If we manage to detect the reflections from solar cells on alien planets, the pollution of cultural societies or the flashes from their spacecraft, it would not only revolutionize astronomy – and probably start a new space race.
It could open up a completely new understanding of our existence in the universe, says Avi Loeb.
“If, for example, the aliens have had one billion years to develop their knowledge and technology, they could be like gods to us. Then I would ask the aliens what is the purpose of life. This is a fundamental question of humanity, and perhaps they know the answer.”
