The convoluted birth of a triple star
The astronomer Rafael Bachiller reveals to us in this series the most spectacular phenomena of the Cosmos. Pulsating research topics, astronomical adventures and scientific news about the Universe analyzed in depth.
Observations with the giant radio telescope ALMA show that a triple system of forming stars is accompanied by large spiral arms that act like conveyor belts, funneling material from interstellar space toward the stars that are being born.
infrared
In the constellation of Taurus, about 460 light-years away, are the closest interstellar clouds in which we can observe the birth of low-mass stars like our Sun.. The vast majority of these stars are not born one by one, but as members of small swarms (so-called open clusters) or in the form of multiple systems.
IRAS04239 is one of these multiple systems: it is made up of three protostars that, together, emit intense infrared radiation. In fact, when it was captured by the small IRAS space telescope in 1983, this emission is what allowed the discovery of the stellar system.. Being located at a short distance from Earth, the IRAS04239 system can be observed with a high level of detail, which makes it possible to study star formation phenomena in all their details.
streamers
Astronomer Jeong-Eun Lee, from the University of Seoul, has coordinated an international team that has used the giant radio telescope ALMA to observe the emission of the molecular gas in which the IRA043239 system is embedded.. However, the emission of different molecules of that gas can be used to delineate some areas or others.
IRAS04239: observations and simulation
Lee's team used the emission of sulfur monoxide (SO) to study regions that were particularly dense and, quite possibly, subjected to the passage of shock waves.. Such waves would be responsible for ejecting sulfur into the gas phase, which is preferably usually found in solid grains of interstellar dust.
Well, by following the trace of these emissions, the astronomers observed that the emission is concentrated in three large filaments that, like spiral arms, connect the surrounding interstellar medium with the protostars.. These filaments look like streamers made of gas that stretch up to 400 times the Earth-Sun distance.
The protostars in IRAS04239 are still in formation, they continue to accumulate material from the natal cloud, which allows them to continue to fatten.. Observations indicate that the way they accumulate this material is through such filaments or streamers that act as great conveyor belts that channel the material from the cloud to the surfaces of the stars.
supercomputers
To test these ideas, the team of astronomers performed numerical calculations that simulate the formation of multiple stars taking into account that they are within their natal cloud and that the stars can interact with the gas in the cloud.. These are very complex calculations as they must take into account a wide variety of physical phenomena (gravitation, turbulence, magnetic fields, etc.). Therefore, for this type of work, you have to resort to large supercomputers.
Lee and colleagues used the largest machines at the National Astronomical Observatory of Japan (NAOJ) Center for Computational Astrophysics.. In simulations, they observed how naturally disturbed gas in the region surrounding a forming triple system ends up exciting shock waves that trigger the formation of spiral arms.. And they confirmed that such filaments act as channels that supply gas to the forming stars from the parent cloud.. The gas velocities that emerge from the simulations agree well with those measured in the observations, which confirms that these calculations are a good representation of the real situation.
This work illustrates very well how the synergies of ALMA observations and numerical simulations can shed a lot of light on the formation of very complex systems such as IRAS04239, which should allow discerning between different star formation theories.. Observation and theoretical interpretation are the two essential facets of astrophysical research: one would be of little use without the other.
The article by Lee et al. entitled Triple spiral arms of a triple protostar system imaged in molecular lines has just been published in the prestigious American magazine The Astrophysical Journal and can be consulted at this link.
Rafael Bachiller is director of the National Astronomical Observatory (National Geographic Institute) and academic of the Royal Academy of Doctors of Spain.