Out in the universe, many forms of stellar interaction take place, from collisions to stars being thrown out of stellar clusters. Now, the Atacama Large Millimeter/submillimeter Array (ALMA) has snapped an image of a different kind of interaction, and it is truly stunning.
The beautiful observation shows the star system HD101584, where a dramatic stellar clash took place. One of the stars in the system became a red giant. This is a fate that stars like the Sun experience towards the end of their life after they have run out of hydrogen to burn in their core. At that point, they start burning helium and swell up, becoming much larger and consequently less dense.
Stars can stay as red giants for a really long time, slowly losing material and eventually leaving behind nothing but their exposed core, which is what we refer to as a white dwarf. But this is not what happened to this red giant. And the fault is in its companion star. As the red giant swelled, it engulfed its lower-mass companion. In doing so, it sent the companion on a spiral towards the larger star’s core without colliding with it.
As described in detail in Astronomy & Astrophysics, this interaction pushed the red giant into releasing a major outburst of material. This pushed its outer layers outward, leaving its core exposed for the researchers to see.
“The star system HD101584 is special in the sense that this ‘death process’ was terminated prematurely and dramatically as a nearby low-mass companion star was engulfed by the giant,” lead author Hans Olofsson, of the Chalmers University of Technology, said in a statement.
The particular interaction between the stars, the release of energetic jets of gas, and the layer the red giant previously shed are responsible for the breathtaking composition that was observed by ALMA. But this is about more than just beauty. The observations are giving us unique insights into the eventual demise of red giants.
“Currently, we can describe the death processes common to many Sun-like stars, but we cannot explain why or exactly how they happen," added co-author Sofia Ramstedt from Uppsala University. "HD101584 gives us important clues to solve this puzzle since it is currently in a short transitional phase between better studied evolutionary stages. With detailed images of the environment of HD101584 we can make the connection between the giant star it was before, and the stellar remnant it will soon become.”