Aliens could be common on planets orbiting stars similar in size to our own sun, according to new research.
Nearly half of such stars come in pairs, known as binary systems. Their combined energy extends the habitable region further away, making it larger. They heat each other’s worlds, as well as their own, meaning they have a greater chance of being orbited by one that has liquid water.
The project leader, Professor Jes Kristian Jorgensen, of the University of Copenhagen in Denmark, said: “The result is exciting since the search for extraterrestrial life will be equipped with several new, extremely powerful instruments within the coming years.
“This enhances the significance of understanding how planets are formed around different types of stars. Such results may pinpoint places which would be especially interesting to probe for the existence of life.”
The discovery is based on observations, made by the Alma telescopes in Chile, of a young binary star about 1,000 light years from Earth. Named NGC 1333-IRAS2A, it is surrounded by a disc of gas and dust. The international team created computer simulations of the star, going backwards and forwards in time.
Co-author Dr Rajika Kuruwita, also from Copenhagen University, said: “The observations allow us to zoom in on the stars and study how dust and gas move towards the disc. The simulations will tell us which physics are at play, and how the stars have evolved up till the snapshot we observe, and their future evolution.”
Notably, the movement of gas and dust does not follow a continuous pattern. For “relatively” short spells over thousands of years, it becomes very strong. The binary star becomes up to a hundred times brighter – until it returns to its usual state.
Presumably, the cyclic pattern can be explained by duality. The two stars encircle each other. At given intervals, their joint gravity will affect the surrounding disc in a way that causes huge amounts of material to fall towards the star.
Dr Kuruwita said: “The falling material will trigger a significant heating. The heat will make the star much brighter than usual. These bursts will tear the gas and dust disc apart. While the disc will build up again, the bursts may still influence the structure of the later planetary system.”
The stellar system, described in Nature, is still too young for planets to have formed.
Prof Jorgensen said: “Comets are likely to play a key role in creating possibilities for life to evolve. Comets often have a high content of ice, with presence of organic molecules. It can well be imagined that the organic molecules are preserved in comets during epochs where a planet is barren, and that later comet impacts will introduce the molecules to the planet’s surface.
“The heating caused by the bursts will trigger evaporation of dust grains and the ice surrounding them. This may alter the chemical composition of the material from which planets are formed.
“The wavelengths covered by Alma allow us to see quite complex organic molecules, so molecules with nine to 12 atoms and containing carbon. Such molecules can be building blocks for more complex molecules, which are key to life as we know it. For example, amino acids, which have been fund in comets.”
Alma (Atacama Large Millimetre/submillimetre Array) has 66 telescopes operating in coordination. This allows for much better resolution than could have been obtained by a single telescope.
The new James Webb Space Telescope (JWST) launched last Christmas will soon join in the search for extraterrestrial life. By the end of the decade it will be complemented by the ELT (European Large Telescope) and the extremely powerful SKA (Square Kilometre Array).
The ELT, with its 39-metre mirror, will be the biggest optical telescope in the world, and will observe the atmospheric conditions of exoplanets outside the solar system. SKA will consist of thousands of telescopes working in coordination in South Africa and Australia, and will have longer wavelengths than Alma.
Prof Jorgensen said: “The SKA will allow for observing large organic molecules directly. The James Webb Space Telescope operates in the infrared, which is especially well suited for observing molecules in ice. Finally, we continue to have Alma, which is especially well suited for observing molecules in gas form. Combining the different sources will provide a wealth of exciting results.”
