Simulation of binary star
University of Copenhagen/Jørgensen, Kuruwita et al.
Binary (or double) stars may in fact hinder life as we know it, new observations by the Atacama Large Millimeter/submillimeter Array (ALMA) in northern Chile, reveal.
Details of the millimeter wavelength observations of the extremely young 10,000-year-old binary star system NGC 1333-IRAS2A, as reported this week in the journal Nature indicate that planetary systems around binary stars may be very different from those around single stars.
“Binarity in the infant stages of stars may strongly affect the emerging planets around them and their composition,” Jes Kristian Jorgensen, the paper’s lead author and an astronomer at the University of Copenhagen in Denmark, told me. We show that by combining very detailed ALMA observations with state-of-the-art computer simulations, he says.
What is known is that nearly half of all sunlike stars in our galaxy are binary or lie in multiple stellar systems. As a result, if planetary systems that form around double stars inherently face more challenges than those which form around single stars like our Sun, then prospects for ubiquitous life in our galaxy could be overly optimistic.
As for NGC 1333-IRAS2A?
It’s too young to have formed planets. Located about one thousand light years distant in the Perseus molecular cloud, NGC 1333-IRAS2A is surrounded by a disc consisting of gas and dust with two stellar components separated only by some 200 astronomical units, or about five times the distance between here and Pluto.
NGC 1333-IRAS2A is also not yet burning hydrogen. However, a central gaseous core where deuterium burning is taking place (deuterium fusing with hydrogen to form helium-3).
Array Operations Site, Radioastronomical observatory, Chile, 2013.
Flickr Vision
Will it become a sunlike binary?
We think that the two components of the binary system each likely will evolve into stars with masses roughly like the Sun, says Jorgensen. Whether they in fact remain a gravitationally bound binary system is not entirely clear, he says.
One of the most novel aspects of the team’s observations involved a seemingly, cyclic brightening of each proto-stellar component of the binary system. This is thought to be caused by large amounts of infalling gas and dust from the protoplanetary disk and onto the two stellar components of the binary system.
The two stars encircle each other, and at given intervals their joint gravity will affect the surrounding gas and dust disc in a way which causes huge amounts of material to fall towards the star, says Jorgensen. These bursts will tear the gas and dust disc apart, he says.
How will this brightening bursts affect planet formation?
The bursts may increase the temperatures in the proto-stellar disks causing ices covering dust grains to sublimate (or pass directly from a solid to a gas), says Jorgensen. This, in turn, may make it more difficult for them to stick together and grow to larger planetesimals and eventual planets, he says.
These bursts may also push these respective planetary systems so-called snow lines farther out. The snow line is the line of demarcation where a planetary system is cold enough for volatile compounds such as water, ammonia, and methane to condense into solid ice grains.
In our own Solar System researchers speculate that it is the location of this snow line that has given us the division between the smaller rocky planets in the inner Solar System vs. the larger giant planets in the outer Solar System, says Jorgensen. So, the occurrence of such bursts may strongly affect the “architecture” of the emerging planetary systems compared to those around single stars, he says.
If this stellar binarity pushes the snow line outwards, would it make it more difficult to have an inner solar system like ours?
It would mean that the giant planets would form further out which in turn might affect the overall structure and evolution of the planetary system, says Jorgensen. Jupiter’s current location affects our rocky planets’ orbits; causing them to be circular and stable, he says.
