This is a binary star in the process of formation

Inside the Rho Ophiuchi dark nebula lies a binary system named IRAS 16293-2422 A. Though it’s already a widely-studied object, previous studies produced some conflicting results. Different observations at different wavelengths showed multiple compact sources of radiation at different locations. The thick dust was making things difficult.

This study went further than previous studies. ALMA allowed the team of researchers to pinpoint the sources within the dark nebula. Astronomers already knew about the presence of what’s known as Protostar-B in the system, a well-known object. But their observations also revealed the two compact point sources of radiation, A1 and A2, in more detail than ever before.

Both young stars are similar in mass to the Sun. A1 is just under one solar mass, while A2 is about 1.4 solar masses. Each one is embedded in its own dust disk. A2’s dust disk is somewhat larger than A1’s, and appears at an angle relative to the orientation of the Rho Ophiuchi cloud structure. That’s an unusual detail, and points to some chaos in the system. The already known Protostar B has a disk that’s face-on from our vantage point, adding to the chaotic nature.

The team had 30 years of data on this system at their disposal. They added their new observations to all of that data, and came up with some new conclusions. The two proto-stars are orbiting each other every 360 years, at an orbit that’s similar to Pluto’s full extent in our Solar System.

“This is the first time that we were able to derive the full orbital parameters of a binary system at this early stage of star formation,” said co-author Jaime Pineda, also from MPE, who contributed to the modelling.

Source: “This is a binary star in the process of formation” Universe Today, 12 June 2020. <>

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