Observations with the MIRI instrument showed that IRS 3 is an aging, oxygen-rich giant star, surrounded by layers of dust and gas. According to the researchers' model, it is losing a mass equal to the mass of the Earth about every 18 days.
Observations of James Webb Space Telescope revealed clear signs of water molecules within the dust and gas envelope of IRS 3This is an aging star located nearby. Milky Way Center.
IRS 3 is shedding large amounts of material. The material forms a vast, multilayered shell around it, with a radius of about 10,000 astronomical units. One astronomical unit is the average distance between the Earth and the Sun.
The discovery shows that molecules and dust can survive even in the extreme environment surrounding the Sun. A* bow — the supermassive black hole at the center of the galaxy. However, the discovery of water does not indicate life or an environment suitable for life.
Close to the black hole — at least as seen from Earth
IRS 3 is located at a projected distance of about 0.17 parsecs, or about 0.55 light-years, from Arc A*. The term “projected distance” is important: the observations measure the separation between the two objects on the sky, but do not precisely determine the distance between them along the line of sight.
On a galactic scale, this is a very close environment to a black hole. The mass of Sagittarius A* is about four million times greater than the mass of the Sun. It is surrounded by stars, gas and dust, and is surrounded by a radiation field and extreme dynamical conditions.
Previous observations have already shown that Dusty objects can survive near the A* arcThe new study adds to the picture a developing star, which continues to shed dust and molecules into its surroundings.
Webb examined the fingerprint of dust and water
The researchers observed IRS 3 on April 21, 2025. They used a medium-resolution spectrometer MIRI, Webb's mid-infrared instrument. The measurement range extended from a wavelength of 4.9 to 27.9 microns.
The spectrum revealed two prominent absorption features at wavelengths of 9.7 and 18.5 microns, which the researchers attribute to different vibration modes of amorphous silicates.
Between 6 and 6.25 microns, the team also identified spectral signatures consistent with water. The researchers note that the water may be located in one of the inner layers of the mantle, about 900 astronomical units from the star. Its exact location is still unproven.
Using MIRI allows us to identify cool dust and chemical features that are difficult to see in visible light. The same instrument has previously also revealed Unexpected dust structures in the Beta Pictoris system.
Not a carbon-rich star
Previous studies have suggested that IRS 3 is a carbon-rich AGB star. AGB stars They are highly evolved stars, which are in a late stage of their lives and are shedding their outer layers.
The new spectrum changes the classification. The ratio of silicate signatures better fits oxygen-rich chemistry. The preferred model describes a star with a current mass close to six solar masses, an age of about 72 million years, and a surface temperature of about 2,800 Kelvin.
Researchers estimate that its luminosity is about 60 times greater than that of the Sun. It is relatively cold on the surface, but very bright due to its large size.
Earth's mass every 18 days — according to a model
The researchers concluded that IRS 3 is in the process of Mass loss Fast machine "Superwind". During this period, a developed star emits large amounts of gas and dust for hundreds or thousands of years.
The rate of mass loss was not measured by weighing the ejected material. The researchers calculated it from a model of the dust envelope and the structure of the bow shock around the star. The calculation assumes, among other things, a wind speed of about 15 kilometers per second.
The result is a rate of about six hundredths of a thousandth of the mass of the Sun per year. This is roughly equivalent to the mass of the Earth every 18 days.
The model includes several layers of dust. Their estimated expansion times range from about 300 to about 3,200 years. The structure may result from changes in the rate of material ejection, from an as-yet-undetected companion star, or from the influence of the A* arc. At this stage, no decision has been made between the possibilities.
Other stars may also be injecting material into the region. Previous research has suggested, for example, that The star system IRS 16SW may provide gas clouds for Sagittarius A*.
How does water manage to survive?
The environment near the center of the galaxy is exposed to radiation and processes that can break down molecules. However, a dense envelope of gas and dust can provide partial shielding.
Therefore, it cannot be concluded that the water is directly exposed to the strongest radiation in the region. It may survive within relatively dense and protected layers in the IRS 3 envelope.
The broader implication is that aging stars can continue to enrich the interstellar medium with dust and molecules even near an active galactic center. Such material may in the future be incorporated into gas clouds, stars, and new planetary systems.
The observation does not indicate the existence of life. Water is an important molecule in cosmic chemistry, but its mere presence does not indicate biological conditions.
Next Look: The Extremely Large Telescope
The researchers hope to continue studying the mantle using METIS, an infrared instrument built for the European Southern Observatory's Very Large Telescope in the Atacama Desert in Chile.
Its high resolution could help map dust layers and distinguish between recently ejected material and older material. This would allow us to examine whether the structure of the envelope is due to changes in the star itself, a companion, or the influence of the black hole's environment.
The results add to a more detailed picture of the dense region at the heart of the galaxy. Recently Euclid maps tens of millions of stars at the center of the Milky Way, whereas Event Horizon Telescope reveals the surroundings of Sagittarius A* On a much smaller scale.
Questions and Answers
What is IRS 3?
IRS 3 is an advanced AGB star near the center of the Milky Way. It is surrounded by a large envelope of dust and gas formed from material ejected during its evolution.
Is IRS 3 orbiting the black hole?
The study describes its projected distance from the A* arc. From this alone, it is not possible to determine the full three-dimensional distance or conclude that it orbits the black hole in a close orbit.
How is the mass loss rate calculated?
The researchers combined spectroscopic observations with models of the dust envelope and the bow shock. The result depends on assumptions, including a wind speed of about 15 kilometers per second.
Does the discovery of water indicate life?
No. The observation indicates that water molecules can survive in the planet's protective envelope. It does not indicate life or an environment suitable for life.
For the scientific article: Article in Astronomy & Astrophysics and arXiv, original article in SciTechDaily
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