Observations and simulations led by the Max Planck Institute indicate that the star system IRS 16SW is creating compact clumps of gas, which are moving towards Sagittarius A* and contributing to its nutrition.
The supermassive black hole at the center of the Milky Way, Sagittarius A*, is not in a vacuum. Stars, gas, and dust swirl around it in an extreme gravitational field. Over the years, small, dense clumps of gas have been detected near it, but their origin remains unclear. New research led by the Max Planck Institute for Extraterrestrial Physics (MPE) offers a solution: a massive binary star system, IRS 16SW, may be creating these clumps of gas and gradually sending them toward the black hole (mpe.mpg.de).
The study, published in the journal Astronomy & Astrophysics under the title “The gas streamer G1–2–3 in the Galactic center”, focuses on a family of gas clouds called G1, G2 and G2t. These are not huge clouds like familiar nebulae, but compact clumps of ionized gas, whose mass is estimated to be only a few Earth masses. Despite their modest size, they are important because they may explain how material continues to reach Sagittarius A*’s surroundings and maintain its current activity. (aanda.org)
G cloud family near Sagittarius A*
The G2 object was discovered in 2012 as a cloud of ionized gas emitting light from hydrogen and helium lines, a sign of hot gas mixed with dust. It orbits Sagittarius A* in an elongated orbit, and a faint trailing structure, designated G2t, was discovered alongside it. Later, when old observations were reexamined, the G1 object was also found, moving on a similar orbit. The researchers suggest that these objects are not separate cases, but part of a common gas stream known as 1-2-3G.
According to the researchers' calculations, if a single lump of gas, roughly the mass of Earth, were to fall in once a decade, that could be enough to fuel Sagittarius A*'s current level of activity. So the question of where the lumps come from is not a trivial one. It concerns the way supermassive black holes gain material even when they are not in a particularly active phase.
To reconstruct the movement of the clouds, the team used the SINFONI and ERIS spectrographs, which operate in the infrared and use adaptive optics. The researchers focused on the Brackett-γ emission line of hydrogen, and measured the positions and velocities of the gas clumps. The analysis showed that G1, G2, and G2t move in orbits with very similar shapes and directions. The likelihood that three unrelated objects would share such similar orbital characteristics is very small, so the likely conclusion is a common origin.
Possible source: the star system IRS 16SW
When the researchers traced the stream's path back, both in space and in its radial velocity, they came up with a promising candidate: IRS 16SW. It is a massive "contact binary" star system, located in a disk of young stars orbiting Sagittarius A*. The small differences in the orbits of the gas clumps can be explained by the orbital motion of the binary system itself.
The main support for this conclusion came from hydrodynamic simulations. The simulations showed that stellar winds from such a binary system can collide with the surrounding material and create a shock zone. In this zone, the gas is compressed, accumulated, and finally broken off as separate clumps. The clumps then continue on more inward trajectories, similar to what is observed in the 1-2-3G stream.
The finding offers a dynamic picture of the center of the galaxy. The young, massive stars in the region are not just neighbors of the black hole. They may be part of its feeding mechanism. Their stellar winds, usually seen as a phenomenon related to stellar evolution, here become a conduit for transferring material into the black hole's environment.
What does this teach us about black holes??
Sagittarius A* is considered a relatively “quiet” supermassive black hole. It does not swallow material at a high rate like active galactic nuclei in distant galaxies. Precisely for this reason, it serves as a close laboratory for understanding weak and delicate feeding processes. If small clumps of gas can maintain its activity over time, this provides an important model for understanding similar black holes in other galaxies.
The study connects three areas that are usually studied separately: the evolution of massive stars, the motion of gas in an extreme gravitational field, and the feeding of black holes. In the case of the center of the Milky Way, all three processes occur in the same dense and dynamic region. Therefore, the discovery of the possible origin of the G1–2–3 clumps is not just the solution to a local mystery. It suggests a relatively simple mechanism by which massive stars can feed material into a supermassive black hole even without a dramatic event of a collision or starburst.
The paper, published in Astronomy & Astrophysics, volume 707, paper A79, was written by Stefan Gilsen, Frank Eisenhower, Jorge Cuaderra, Reinhard Ganzel and colleagues. According to the publication details, the research is based on infrared observations and simulations of the movement of gas in the center of the galaxy.
FAQ short:
What did the new study reveal?
The study suggests that the binary star system IRS 16SW is creating small clumps of gas that are moving toward the black hole Sagittarius A*.
from them G1, G2 and-G2t?
These are compact clumps of gas discovered near the center of the Milky Way, moving in similar orbits around the supermassive black hole.
why is it important?
The finding suggests a possible mechanism for feeding a relatively “quiet” supermassive black hole using winds from nearby massive stars.
Does the black hole swallow the binary star itself??
No. According to the study, the binary star is not being swallowed. It may be creating clumps of gas through stellar winds, and these clumps then move towards the black hole's surroundings.
for the scientific article DOI: 10.1051/0004-6361/202555808
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