This is an extremely large star that was only discovered in the last 20 years. However, in 2019, it suddenly vanished without a trace.
A “very large star” caught astronomers’ attention in the early 2000s: It seemed to be reaching a final chapter in the life story of a star, offering a rare opportunity to observe the death of a massive star in a metal-poor region.
However, by the time scientists had the chance to use the Very Large Telescope (VLT) of the European Southern Observatory (ESO) in Paranal, Chile, in 2019, it had completely disappeared without a trace.
The two leading hypotheses about what happened are either that it is still there and in the process of dying, with dimmer brightness and possibly obscured by dust, or it has died and collapsed into a black hole without going through a supernova stage. “If true, this would be the first direct discovery of a giant star ending its life in this way,” said Andrew Allan from Trinity College Dublin, Ireland, the lead of the observational team whose research was published in the Monthly Notices of the Royal Astronomical Society.
Kinman Dwarf – the star located in PHL 293B galaxy, 75 million light-years away from us – is no longer observable in the sky. Astronomers have yet to determine the reason.
The time span between the last observations by astronomers in 2011 and 2019 is significant enough for something to have happened.
We often think of cosmic events as slow-moving phenomena because their subsequent impacts are usually vast and unfold over time. However, events can actually happen faster and on a smaller scale than human predictions.
In any case, the Kinman Dwarf galaxy, or PHL 293B, is very distant (75 million light-years), far too far for astronomers to directly observe its stars.
The presence of these stars can be inferred from spectral signatures – specifically, PHL 293B from 2001 to 2011 consistently exhibited strong hydrogen signatures indicating the presence of a Luminous Blue Variable (LBV) star about 2.5 times the mass of our Sun. Astronomers suspect that some very large stars may go through their final years as LBVs.
Kinman Dwarf is one of the largest and brightest stars in the universe. Researchers discovered this anomaly while attempting to observe it in the sky to understand the cause of its death.
While LBVs are known to undergo significant changes in their spectra and brightness, they typically leave specific traces that reliably confirm their continued presence. In 2019, hydrogen signatures and such traces disappeared. Allan stated, “It would be very unusual for such a large star to disappear without producing a bright supernova explosion.”
The Kinman Dwarf galaxy, or PHL 293B, is one of the most metal-poor galaxies known. Massive stars are rarely seen in these environments. The now-missing star was considered a rare opportunity to observe the late stages of a massive star in such an environment.
Previous studies of Kinman Dwarf were extensively conducted from 2001-2011. Observations indicated that it seemed to be in the late stage of its life, with many mysteries still to unravel.
In August 2019, the research team simultaneously directed four telescopes from the ESPRESSO array towards the former location of the LBV, but they found nothing there. A few months later, they also employed the X-shooter instrument from the VLT in the search, but the results remained unchanged.
Andrea Mehner, an ESO staff member involved in the research, stated: “The ESO Science Archive allowed us to find and use data from the same object obtained in 2002 and 2009. Comparing the high-resolution UVES spectrum from 2002 with our observations from 2019 using the latest high-resolution spectra from ESO showed that this star had indeed vanished without a trace.”
Reviewing this data indicates that the LBV may have actually ended its life cycle around 2011.
The last sighting of this star was in 2011 when a team of scientists used the Very Large Telescope in Chile. At that time, they were unable to locate Kinman Dwarf. Recently, the team used X-Shooter to determine where the star went but could not find it again.
Combining the 2019 data with contemporaneous images from the Hubble Space Telescope (HST) led the authors of the report to feel that: “The LBV had been in an eruptive state at least from 2001 to 2011, after which it ended its life cycle.”
A star collapsing into a black hole without a supernova explosion would be a rare event. The paper also notes that we may simply have missed the supernova event of the star within the 8-year observation gap.
LBVs are known to be highly unstable, so it is entirely possible that the star faded into a dimmer state or generated more dust cover, making observation impossible.
