Twice the Astronomy Love as Twins are Born in the Depths of Space

Binary stars may be common throughout the galaxy, but a question which has long puzzled astronomers concerns their birth — do they form together, or do they come together through the force of gravity? New observations from the Atacama Large Millimeter/submillimeter Array (ALMA) observatory show a pair of binary protostars forming together from a cloud of gas and dust.

Located 5,500 light years away from our own solar system, IRAS 07299–1651 contains two massive young stars — a massive primary star and a smaller partner. The two orbit each other once every 570 years, at a distance of 27 billion kilometers (16.8 billion miles), roughly six times the distance between the Sun and Neptune, or 180 times the distance between the Earth and Sun. Together, the stars have a combined mass at least 18 times that of our own parent star.

“Our observations clearly show that the division into binary stars takes place early on, while they are still in their infancy. What is important now is to look at other examples to see whether this is a unique situation or something that is common for the birth of all massive stars,” said Yichen Zhang, leader of the team which made the discovery.

IRAS 07299–1651 as seen by the ALMA network of radio telescopes. In this image, gas and dust moving toward the stars is shown in green, while material moving toward us is blue and that moving away from us is pictured in red. The inset image shows the larger primary star (in blue) moving in our direction, while the smaller protostar (red) travels away from our point of view. The cross marks their common center of gravity. Image credit: RIKEN, ALMA (ESO/NAOJ/NRAO), Zhang et al.

These massive clouds from which stars form make it difficult to see protostars. Radio waves can escape the dim, but radio telescopes are usually unable to separate the members of binary pairs as the coalesce. The ALMA observatory utilizes next-generation technology, collecting data from radio telescopes around the world, revealing this process.

The nearest star system to our own world is a binary pair, Alpha Centauri A and B, shown here in a photograph from the Hubble Space Telescope. This pair also has a small third companion, Proxima Centauri, which orbits the two main stars. Image credit: ESA/Hubble/NASA

“Massive stars are important throughout the universe, including for producing the heavy elements that make up our Earth and are in our bodies, but their formation mechanism is literally shrouded in mystery, being so deeply embedded in dusty clouds,” said Jonathan Tan, an astronomer at the University of Virginia.

Planets surrounding binary stars, a favorite setting for science fiction authors, are typically thought of as unlikely places to find life, as planetary orbits can be unstable, and the degree of heating can vary greatly. However, new computer simulations suggest these systems may be home to habitable worlds, as a gravitational pull from a third star can pull binary pairs together, increasing the size of the habitable zone around stars, where liquid water can pool on the surface of a planet.

The IRAS 07299–1651 system, found in the constellation Puppis, is seen as the protoplanetary disk fragments into two pieces, creating the binary pair. This results in a situation where the smaller of the stars is siphoning material off its larger partner, and at some time in the future, the pair should be nearly identical twins.