Almost half of all stars in our galaxy belong to binary systems. So the famous Star Wars moments, when they show a double sunrise or sunset on Tatooine — the fictional planet where the galaxy’s greatest heroes Anakin and Luke Skywalker grew up — aren’t that great. Planetary systems of two gravitationally bound stars orbiting in closed orbits around a common center of gravity are very common objects. Moreover, as shown by a new study by Danish scientists, they should not be ignored when looking for habitable planets. It turned out that the planets orbiting these stars have a high chance of alien life appearing on them.
Under two suns
Our Earth is still the only known planet that has life. So when it comes to whether extraterrestrial life could exist somewhere, astronomers are basically looking for Earth-like planets, that is, planets orbiting a fixed parent star at the optimal distance—not too close and not too far until it was neither too cold or too cold. warm for liquid water and living things to live.
Some of the binary stars look breathtakingly beautiful against the background of the Milky Way’s star field.
However, a study by researchers at the University of Copenhagen showed that during the search for alien life, one should pay attention to binary planetary systems consisting of stars similar to the Sun. The planets orbiting these stars have a high chance of harboring extraterrestrial life.
As Danish astronomers believe, planetary systems around binary stars are formed in a completely different way than systems of single stars, and this in turn means that habitable planets in binary star systems can have completely different properties than previously thought. In addition, they are an even better place to look for extraterrestrial life, because in such star systems the area of space where life can arise on the surrounding planets is much larger. Both stars heat each other’s planets, which means that a planet with liquid water and living organisms could definitely appear around one of them, say Danish scientists.
A double star that is “only” 1,000 light years away
Jes Christian Jørgensen, head of research at the University of Copenhagen, looks forward to the future. “The result is impressive. In addition, the search for extraterrestrial life will be possible in the coming years with the help of several new, extremely powerful tools,” he notes. And in such a situation, it is all the more important to know how planets form around different types of stars – because thanks to this information, it becomes easier to identify places of particular interest when it comes to the search for extraterrestrial life, emphasizes Jorgensen.
ALMA radio telescope complex in Chile
The new discovery is based on observations made with the radio telescope complex ALMA (Atacama Large Millimeter/submillimeter Array) in the Atacama Desert in Chile. ALMA consists of 66 high-precision antennas working together at wavelengths from 3.6 to 0.32 millimeters (31 to 1000 GHz), resulting in much better resolution than could be achieved with a single telescope.
The object of observation within the framework of the new study was a young system of two stars located in the Perseus molecular cloud at a distance of about 1000 light years from Earth. From an astronomical point of view, this is pretty close. This binary star system, called NGC 1333-IRAS2A, is currently surrounded by a disk of gas and dust, and planets have yet to form around it.
Observations allowed scientists to obtain only snapshots of the evolution of a binary star system. But scientists supplemented the observations with the creation of computer models that show the development of the circumstellar disk, from which planets will form in the future: the computer simulations that were made allowed the scientists to both go back and forward in time in relation to the observed image.
Phenomena affecting the origin of life
Notably, the motion of gas and dust around NGC 1333-IRAS2A does not follow a continuous pattern. At certain times – usually within relatively short periods of ten to a hundred years, repeated every thousand years – the movement of these currents becomes very strong. As a result, the binary star system brightens ten to a hundred times until it returns to its normal state.
Scientists believe that this phenomenon is due to the duality of the star system. Two stars orbit each other and periodically their combined gravity acts on the surrounding disk of gas and dust in such a way that enormous amounts of material fall onto the stars.
“The infalling material causes significant heating. Because of this, the stars become much brighter than usual,” said Rajika L. Kuruwita, co-author of the study. According to her, “such explosions tear apart the disk. While the disk recovers, bursts can still affect the structure of the subsequent planetary system.”
Comets and the origin of life
The observable star system is still too young to form planets. When studying the formation of planetary systems, Danish scientists hope to get more results during observations with ALMA. In addition to the planets, comets will also be subject to their monitoring.
“Comets probably play a key role in the origin of life. Comets often have a high content of ice with organic molecules. And it is quite conceivable that during the epochs when the planet is still uninhabited, organic molecules are preserved in comets, and subsequent collisions with comets can bring these molecules to the surface of lifeless planets, says Jes Christian Jorgensen.
At the end of the summer of 2019, amateur astronomer Gennady Borisov discovered the first interstellar comet in the history of modern science, called 2I / Borisov, through a 65-cm telescope of his own design.
In this context, he says, it is important to understand the role of flares in young stars: the resulting heating causes dust and ice to vaporize – changing the chemical composition of the material from which planets form. And that, in turn, will require different criteria for observation than before, Jorgensen points out.
With super powerful telescopes
The new James Webb Space Telescope will soon be used to search for extraterrestrial life. And at the end of this decade, it will be complemented by the European Large Telescope (ELT) and the extremely powerful SKA (Square Kilometer Array), a radio telescope with a total antenna collection area of over one square kilometer. The SKA radio interferometer will act as an adaptive antenna array over a wide frequency range, and its size will achieve 50 times greater sensitivity than any other existing radio telescope.
ELT and SKA observations should start in 2027. SKA’s work will provide data on the universe at the age of just a few million years after the Big Bang, that is, at the moment when the first stars and galaxies began to form. SKA will enable direct observation of large organic molecules. The James Webb Space Telescope operates in infrared, which is primarily suitable for observing the molecules found in water ice. And ALMA is particularly good at finding gaseous molecules.
“Such a combination of different sources allows you to get many interesting results,” says Jes Christian Jorgensen.