Astronomers at the Massachusetts Institute of Technology have discovered a peculiar pair of stars in which a low-mass red dwarf star steadily removes gas from a brown dwarf star companion orbiting around it.
While planetary objects and companion stars always have stable and detached orbits, most often the collision ends in the swallowing of the companion by the host star.
From analyzing photometric observations taken at very frequent cadences, the balanced binary system was found to be bound into an unusually tight 86.65-minute orbit.
It is a rare discovery that confirms certain low-mass processes take billions of years for complete consumption of gas and not destruction.
Determining a balanced binary system via photometric measurements
When analyzing archived data from sky survey databases, astrophysicists discovered an optical pattern of periodic signals coming from a star system located about 300 light years away.
There were light curve variations, which seemed to be consistent but could not be classified within the existing models of eclipsing binary systems.
The mass was measured and found to have a balanced system consisting of a small red dwarf and a substellar brown dwarf.
The stars were so close to each other that the entire orbit would easily fit within the diameter of our sun.
Finding stable mass transfer rather than fast stellar ingestion
According to the laws of stellar physics, when a satellite comes too close to a star, tidal forces always lead to a catastrophic orbital disruption.
The process of rapid inspiral results in larger stars consuming incoming planets or substellar objects relatively quickly.
Timing analysis shows no signs of an accelerated spiral motion and hence demonstrates that the system is extremely stable over a long period of time as mass transfer occurs.
Gas from the overfilling brown dwarf flows to the main red dwarf continuously without disturbing the orbital motion.
Stable mass transfer violates conventional concepts about the ultimate destruction of close companions of stars.
Gas stream mapping and location of hot spots on the red dwarf surface
The material is removed from the brown dwarf donor object, which crosses the thin bridge to crash against the primary.
The incoming streams of the gas fall onto the surface of the star with enormous kinetic energy, thus forming a hot spot.
Due to the rotation of the star, the hot spot becomes visible and invisible at regular intervals, producing light curve variation.
The tidal effects are very efficient in converting angular momentum back into orbital motion, which ensures that there will be no acceleration of the primary.
Atmospheric flows transfer heat throughout the surface of the primary to even out its optical light curves.
Calculation of billions of years of stellar cannibalism
Determination of the rate of mass transfer enables astronomers to estimate the future evolutionary path of this special binary system.
This small red dwarf is taking in material slowly but steadily from its dying substellar companion.
With such a low rate of consumption, it can easily go on for hundreds of thousands to billions of years of sustained feeding, according to the Massachusetts Institute of Technology.
Slow mass loss of substellar bodies can sustain their lives for a much longer period than previously thought possible by scientists.
As reported by Nature Astronomy, longer periods of life provide important insights into the evolution of low-mass stars in our local galactic community.
Further study into possible modes of interaction between low-mass companions
Uncovering this rare mass-transfer system has inspired researchers to comb through larger sky survey databases for hidden analogs.
Astronomers aim to focus on such binary systems using state-of-the-art telescopes on Earth and in space.
The detection of more such systems would help us understand how tidal synchronization and mass transfer work under different conditions through fresh searches.
The discovery of more balanced systems of low-mass stars will change our views about planet-star interactions and orbital migration.
Observational results have shown that there is always something left in stellar evolution for us to discover.
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