[University of Cologne] Studies of the star IRS 3, located near the black hole at the centre of our galaxy, suggest that the star is emitting large quantities of gas and dust, thereby forming an exceptionally large envelope in which water molecules have been detected. The study was carried out by a team of astronomers led by PD Dr Florian Peißker from the University of Cologne’s Institute for Astrophysics.
As a member of the European James Webb Space Telescope (JWST) consortium for the observation of nearby galaxies, Peißker’s working group has studied the immediate surroundings of the supermassive black hole Sagittarius A, or Sgr A for short, at the centre of our Milky Way. The new findings were published in Astronomy & Astrophysics under the title “Dust production in the harsh environment of Sgr A* – MIRI/JWST observation of the O-rich asymptotic giant branch star IRS 3”.
For this study, the scientists used the Mid-Infrared Instrument (MIRI) of the JWST. MIRI enables observations in the mid-infrared spectrum and was developed in part at the Institute for Astrophysics. The observations focused on the star IRS 3, which is located approximately 0.6 light-years – or 42,000 astronomical units – from the black hole.
Projected stand-off distance estimate for the bow shock of IRS 3. The stand-off distance is a measure of the ambient ISM and the ram pressure of the star. Here, the green x marks the position of IRS 3 and the green circle marks the apex of the bow shock. — University of Cologne
One astronomical unit is equal to the distance from the Earth to the Sun. It would take the Voyager 1 probe, the human-made object furthest from Earth in the universe, 10,000 years to cover that distance. From an astronomical perspective, however, IRS 3 is located in the immediate vicinity of the black hole Sgr A*.
What makes this star so special is its enormous envelope, which has a radius of 10,000 astronomical units. Mature stars often show large envelopes. However, this means that IRS 3 stands alone in the immediate vicinity of Sgr A*, which is unusual given the presence of millions of other stars.
Observations made using the MIRI instrument have now made it possible to form a detailed analysis of the envelope of IRS 3. Contrary to earlier studies, the team of scientists led by Peißker discovered that the star is in a phase known as the ‘superwind’. In astrophysics, a ‘superwind’ is a phase of extremely rapid mass loss that occurs at the end of a massive star’s life. In the process, the stars eject enormous quantities of gas and dust into their surroundings over the course of centuries.
Research suggests that IRS 3 is losing the equivalent mass of Earth every 18 days, causing its envelope to grow contnuously. This explains both the size and density of the envelope, inside of which unexpected molecules were found.
Disproving the previous assumption that the radiation associated with the black hole and its surroundings impedes the survival of molecules, the scientists have used the James Webb Space Telescope to detect water in the IRS 3 envelope. This suggests that the star is actively helping to enrich the environment around Sgr A* with the fundamental building blocks of life.
Researchers in Professor Dr Lucas Labadie’s working group at the Institute for Astrophysics are currently building the next generation of instruments, which are due to come into operation in a few years’ time at the Extremely Large Telescope in Chile’s Atacama Desert. Using the so-called METIS instrument, the scientists will then be able to further unravel the mysteries of IRS 3’s envelope and the secrets it holds.
Dust production in the harsh environment of Sgr A* – MIRI/JWST observation of the O-rich asymptotic giant branch star IRS 3, Astronomy and Astrophysics (open access)
Astrobiology, Astrochemistry, biosignature,
