Nearly half of all stars the size of the Sun are binary. According to new study from the University of Copenhagen, planetary systems orbiting binary stars may be significantly different from those orbiting single stars. This suggests new areas to look for extraterrestrial life.
Because the only known planet with life, Earth, orbits the Sun, planetary systems around similar-sized stars are ideal candidates for astronomers looking for extraterrestrial life. A binary star is nearly every second star in that category. A new study from the University of Copenhagen found that planetary systems form quite differently around binary stars than they do around single stars like the Sun.
“The outcome is intriguing because the quest for extraterrestrial life will be aided by several new, incredibly powerful tools in the coming years. This emphasizes the importance of understanding how planets develop around various types of stars. Such findings could suggest to locations where it would be particularly fascinating to look for signs of life” According to the project’s director, Professor Jes Kristian Jrgensen of the Niels Bohr Institute at the University of Copenhagen.
The project’s findings, which included astronomers from Taiwan and the United States, were published in the journal Nature.
The observations allow us to focus in on the stars and investigate how dust and gas travel towards the disc. The simulations will tell us which physics are at work, how the stars grew up to the snapshot we see, and how they will evolve in the future.
Rajika L. Kuruwita
Bursts shape the planetary system
The latest discovery is based on observations obtained by the ALMA telescopes in Chile of a young binary star roughly 1,000 lightyears from Earth. NGC 1333-IRAS2A is encircled by a disc of gas and dust. The observations can only offer researchers with a snapshot of the binary star system’s evolution at a specific point in time. However, the team has supplemented the observations with computer models that go both backwards and forwards in time.
“The observations allow us to focus in on the stars and investigate how dust and gas travel towards the disc. The simulations will tell us which physics are at work, how the stars grew up to the snapshot we see, and how they will evolve in the future” explains Niels Bohr Institute Postdoc Rajika L. Kuruwita, the article’s second author.
Notably, gas and dust flow does not follow a consistent pattern. The movement gets very strong at specific points in time, usually for relatively short periods of ten to one hundred years per thousand years. The binary star brightens ten to one hundred times before returning to its original state.
The cyclic pattern is most likely explained by the binary star’s duality. The two stars round each other, and their combined gravity affects the surrounding gas and dust disc at regular intervals, causing massive amounts of material to descend towards the star.
“The falling debris will cause a large amount of warmth. “The heat will cause the star to shine much brighter than usual,” Rajika L. Kuruwita explains, adding, “These bursts will break the gas and dust disc apart.” While the disc will rebuild, the bursts may still have an impact on the formation of the subsequent planetary system.”
Comets carry building blocks for life
The observed stellar system is still too young for planets to have formed. The team hopes to obtain more observational time at ALMA, allowing to investigate the formation of planetary systems.
Not only planets but also comets will be in focus:
“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,” says Jes Kristian Jørgensen.
Understanding the role of the bursts is important in this context:
“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.”
Thus, chemistry is a part of the research scope:
“The wavelengths covered by ALMA allow us to see quite complex organic molecules, so molecules with 9-12 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.”
Powerful tools join the search for life in space
ALMA (Atacama Large Millimeter/submillimeter Array) is not a single instrument but 66 telescopes operating in coordination. This allows for a much better resolution than could have been obtained by a single telescope.
The new James Webb Space Telescope (JWST) will join the quest for extraterrestrial life very soon. JWST will be joined near the end of the decade by the ELT (European Large Telescope) and the immensely powerful SKA (Square Kilometer Array), all of which are scheduled to begin observations in 2027. The ELT will be the largest optical telescope in the world, with a 39-meter mirror, and will be able to observe the atmospheric conditions of exoplanets (planets outside the Solar System, ed.). SKA will be made up of thousands of telescopes in South Africa and Australia that will work together to produce longer wavelengths than ALMA.
“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,” Jes Kristian Jørgensen concludes.
Background
The researchers used the ALMA telescopes in Chile to study the binary star system NGC 1333-IRAS2A in the Perseus molecular cloud. The distance between Earth and the binary star is approximately 1,000 lightyears, which is a very tiny distance in astronomical terms. It is a fairly young star, having formed 10,000 years ago.
The binary system’s two stars are 200 astronomical units (AUs) apart. An AU is the distance between Earth and the Sun. In comparison, Neptune, the Solar System’s furthest planet, is 30 AUs from the Sun.
