The discoveries of exoplanets in recent years have been absolutely extraordinary, and they could relatively soon be reached by our technology. At Cape Canaveral in Florida, on April 18, 2018 at 6:51pm, the Falcon Nine rocket was launched to send NASA’s Transiting Exoplanet Survey Satellite or TESS space telescope into orbit. It is a probe that scans the sky for planets about 100 light years away orbiting stars similar to our Sun.
Over the next decade, scientists expect TESS to fulfil its primary mission, which is to discover thousands of exoplanets. Exoplanets are planets that lie beyond the solar system. This is a golden age as far as discoveries are concerned. Only some 20 years ago we did not know that there were Earth-like planets in the Universe and it is hard to believe how many more things will come to light at such a pace. It is difficult to keep up with today’s discoveries: as of May 1 this year, there were 5,017 exoplanets.
Only recently, thanks to the development of satellites and high-power, high-definition telescopes, has it been possible to study neighbouring planets more accurately, particularly those capable of harbouring life. In the past, the idea that Earth-like planets could exist in the galaxy was not only inconceivable, but was also considered heretical blasphemy (Giordano Bruno’s execution was a case in point).
In the early 1990s astronomers, although with high-powered telescopes, were unable to detect distant planets. It is not easy to see an exoplanet: just imagine looking at a firefly next to a reflector. The process is extremely difficult because stars shine with their own light and planets reflect their light: generally speaking, a star is about 10 billion times brighter than a planet but, thanks to remarkable technological advances, two astronomers – Polish scientist Aleksander Wolszczan and Canadian scientist Dale Frail – detected two planets – Poltergeist and Phobetor – through a terrestrial telescope, near the newly discovered pulsar star B1257+12. The case of 51 Pegasi b (Bellerophon-Dimidium), which was spectroscopically detected by the Swiss Michel Mayor and Didier Queloz in 1995, is different. It orbits a Sun-like star (51 Pegasi) and is therefore considered to be the first exoplanet in all respects. On October 8, 2019, the two Swiss scientists received the Nobel Prize in Physics.
The search had already intensified ten years earlier, in 2009, with the launch of Kepler, the first space telescope designed to detect exoplanets. In 2018 Kepler was replaced by the aforementioned even more powerful TESS. The most interesting aspect of TESS is that it was designed for the specific purpose of detecting exoplanets using the transit method, which detects the decrease in brightness of a star’s light due to the transit of a planet. The decrease in brightness signals the transiting body and the orbit is determined, based on the frequency. It is an excellent method for finding new planets.
Although the search for exoplanets was initially aimed at establishing how many planets in the galaxy orbit the stars, the results are staggering: our galaxy has about 400 billion stars and, according to recent discoveries, on average each star hosts at least one planet: this means that there are at least 400 billion planets in our galaxy, the Milky Way.
The discovery of such a large number of exoplanets is a radical change in our knowledge of the Universe, but the idea that millions of planets might not only be able to host other life forms, but also to generate them, is even more extreme. To this end, astronomers and astrophysicists are searching for planets in a region they call the habitable zone. The habitable zone is the area around the star that enables the planet to maintain water in a liquid state. Scientists are looking for a planet in an optimal location, not too close or far from the parent star, that has enough oxygen and water to make the atmosphere, and probably even life, possible.
Scientists are astounded at the amount of planets discovered in the habitable zone that could harbour life forms: as mentioned above, there are at least 400 billion planets in our galaxy – hence even just one per cent equates to four billion planets that could potentially be habitable. The discovery of exoplanets has radically changed the way we think about the entire Universe: almost all scientists believe that other forms of life may exist. Despite the large number of habitable exoplanets, many scientists argue that only microbial or bacterial life forms could exist outside the Earth. They are wary of what they call far-fetched theories that planets could harbour more sophisticated and evolved intelligent life forms, probably equipped with more advanced technologies than ours. Japanese-born astrophysicist Michio Kaku – a summa cum laude graduate of Harvard University – said: ‘Think about it. The Universe is about 13.8 billion years old, while the Earth is only 4.6 billion years old. How many civilisations could have arisen and fallen in this time span before the formation of the Earth?”
The theory, coupled with the practical discovery that the galaxy teems with Earth-like planets, has triggered a revolution in the scientific community. It is believed that most of the planets in the habitable zone are home to life forms very similar to ours. In the Atacama Desert, Chile, in August 2016 astronomers announced the discovery of a planet orbiting the closest star to our solar system, namely Proxima Centauri. The planet in question, Proxima B, is Earth-like and close enough to its star to harbour life. Proxima B is one of the most interesting and recently discovered exoplanets: it is about 1.3 times larger than Earth. Scientists believe it is rocky and may be similar to our planet. Proxima B may be habitable and is being studied with telescopes in more detail; images will be available over the next ten years.
Despite the immense distance, an ambitious programme to study it by spacecraft is underway. The Breakthrough Starshot project is the brainchild of Israeli citizen Russian philanthropist Jurij Milner and the late, famous cosmologist, Stephen Hawking (1942-2018). Milner said: “For the first time in the history of mankind, we will not only be observing the stars, but we will also be able to reach them”. The goal of Breakthrough Starshot is to send small probes a few centimetres in size to the nearby planet. The microchip will be fitted with a sort of parachute propelled by laser beams that will inflate the sails and deposit the probe on the nearest star. The device will travel at cruising speed, but can accelerate up to 20% of the speed of light so that it will easily reach the nearest stars. Although travelling at very high speeds, the probes will take twenty years to complete the journey.
Light travels at a finite speed: the sun rays take about eight minutes to reach the Earth. Many bodies are thousands or millions or billions of light years away.
In recent years, an increasing number of astrophysicists have speculated that mankind could unravel the mysteries of interstellar space travel much sooner than previously thought. They believe the key is to use a theoretically possible structure known as wormhole: a space-time curve theorised by Albert Einstein that could make interstellar travel times not only shorter but almost instantaneous. Wormholes are capable of curving space and would play a key role in space travel. They are studied in the current theory of gravity and general relativity. A wormhole is a tunnel that connects two separate ends that are folded on themselves: they are commonly called stargates, because they enable travel over considerable distances in less time than light would take, but without exceeding the speed of light. In theory, spacecraft capable of creating wormholes could travel to distant exoplanets in a few hours or a matter of seconds, respecting Einstein’s laws.
Mount Palomar, California, October 6, 2013: a red supergiant star in the constellation Pegasus. ten times larger than the Sun, exploded in a colossal supernova. For the first time, scientists could witness the death of a supergiant star in real time but, as the dying star was 160 million light years from the Earth, astronomers witnessed an event that had happened 160 million years ago.
One of the basic concepts of astronomy is that almost everything we see happened in the past because light does not travel instantaneously. A supernova is a stellar explosion that wipes out all the planets around it, including any civilisations or life forms, but the whole process occurred in the distant past. The violent death of the star in the constellation Pegasus provides dramatic confirmation that the Universe is an ancient and dynamic unit.
Billions of years from now, our star, the Sun, will turn into a supernova and the day is inexorably approaching when we should migrate to another habitable planet. It is not reassuring that the event will occur in the very distant future, as thinking about it today will save us tomorrow.
At La Silla Observatory in Chile, in August 2011 astronomers announced the discovery of a large Earth-like planet in the constellation Orion: the planet is in the habitable zone and the star around which it orbits is very similar to ours, thus making it suitable for hosting life. Hence the goal for us earthlings is to discover a stable solar system, like the one Earth is in.
However, specific resources are needed before practice can be developed from theory. In Los Angeles, in June 2019 TransAstra Corporation announced a partnership with NASA to launch a new project into space, namely asteroid mining. TransAstra Corporation was established in 2015, at the time when entrepreneur Elon Musk with SpaceX, Amazon founder Jeff Bezos with Blue Origin, and others were devising cheap and effective ways to travel to space. By having rockets capable of going into orbit cheaply, a business could be created in space like that of mining asteroids for precious metals of great value on Earth. They are called precious metals because they are becoming scarce on Earth. Hence where can we find asteroids?
Metals such as rare earth elements, gold, copper, zinc and platinum have been mined on Earth for thousands of years and are vital to civilisation, but their supply is limited partly because they do not come from our planet. The Earth originally was a mass in a molten state: many precious metals were drawn inwards. As a result of that process, the heavy elements sank to the centre of the Earth; as they cooled down, a crust of light materials was formed.
It is widely known that without the use of metals, technology and civilisation would not have existed. Luckily for us, it is estimated that about 3.8 billion years ago trillions of asteroids crashed into the Earth, depositing a layer of heavy metals on the Earth’s crust. Those materials did not come from the Earth: they were deposited on our planet by comets and asteroids that crashed into the Earth a long time ago. All the precious metals we mine on Earth come from celestial bodies. The bombardment of asteroids deposited metals that made the Bronze Age, the Iron Age and today’s technological civilisation possible, but many metals – including the rare earth elements needed for technology – are increasingly unavailable. This is the reason why many scientists and experts believe that the asteroid belt could come in handy. An asteroid, even a small one, has more rare earth elements than have been mined on Earth in the history of mankind: it is estimated that if extractions were made from even ten of the over six thousand asteroids – whose existence is recorded in the NASA database – they would produce resources equivalent to 1.5 trillion dollars. The asteroid belt could meet our civilisation’s needs for thousands of years and centuries to come.
The most sensible choice is to build spacecraft to find asteroids, extract material and take all the advantages and benefits.
Mountain View, California, April 2013: scientists at NASA’s Ames Research Centre discovered two new potentially habitable exoplanets, Kepler 62E and 62F, thanks to the Kepler Space Telescope. Planets 62E and 62F are called water worlds because they are covered by a global, all-encompassing ocean and are promising because they are located in the habitable zone and are covered by the ocean.
This means that in a phase of expansion and space migration, not only raw materials are needed, but also water which, once broken down and split into hydrogen and oxygen, could be used as fuel with the processes that are at the forefront, which I have analysed in some of my previous contributions.
It is firmly believed that the search for life forms will further undergo a revolution very soon. On December 25, 2021, NASA launched the James Webb telescope, a space telescope for infrared astronomy, capable of analyses considered impossible until a few years ago, i.e. taking detailed, full-colour images of an exoplanet. The James Webb telescope is completely different from those in space. It gives the possibility to observe the reflected light of exoplanets and the electromagnetic spectrum in order to detect potential biological traces.
The future lies in research, the past in war. The certainty is many graves if we stand still.