La Tercera | From Cerro Paranal, Scientists Make a Surprising Astronomical Discovery

La Tercera recently published an article about an international team of scientists led by Professor Philip Lucas of the University of Hertfordshire, with the participation of Zhen Guo, a researcher at the Institute of Physics and Astronomy of the University of Valparaiso, and Dante Minniti, Director of the Astrophysics Institute of the Universidad Andrés Bello.

After a decade of studying the Milky Way, the team made important discoveries. In particular, a new type of old giant star, which ejects a dust plume, was identified, and newborn stars were found to increase in brightness by up to 300 times over extended periods.

This work was carried out through the long-duration mapping project of the Milky Way called ‘Variables VISTA in the Milky Way’ (VVV), founded by astrophysicist Dante Minniti from UNAB. This initiative uses the VISTA telescope at the Cerro Paranal Observatory, located in Chile, to observe the galaxy with infrared light, allowing the study of stars hidden from view in visible light due to the dust and gas found in the Milky Way.

Astronomical Discoveries from Cerro Paranal

The team discovered 32 erupting protostars whose brightness increased at least 40-fold, and in some cases, more than 300-fold; 25 of these stars were found from telescopes in Chile.»This includes 16 new, rarely encountered FUor-type objects, which expanded the current catalog of such variables by more than 30%,» Dr. Guo noted. Most of the eruptions are still ongoing, allowing astronomers to analyze a large group of these mysterious events for the first time throughout their evolution, from the initial quiescent state to maximum brightness and then into the decay stage.

In addition, the study yielded something completely unexpected. 21 red stars near the center of the Milky Way showed ambiguous changes in brightness during the ten years of observation. Compared with data from previous studies, analysis of the spectra of seven stars concluded that they were a new type of red giant star.

Dr. Dante Minniti, director of the UNAB Astrophysics Institute and leader of the VVV mapping, indicated that «these old stars remain silent for years or decades and then eject dust clouds in a totally unexpected way. Then they look very red and dull for several years, to the point that sometimes we can’t see them at all.» The UNAB researcher added:

Both the gigantic explosions in baby stars and the ejections of opaque dust clouds by the highly enriched stars of the Galactic center are phenomena never seen before and open up other research areas for astronomers.

Likewise, the fact that these discoveries have been made from Cerro Paranal in the Antofagasta region highlights the position that Chile has reached in terms of astronomical capacity.

From Cerro Paranal, Scientists Make a Surprising Astronomical Discovery

Dr. Zhen Guo of the Universidad de Valparaíso and Dr. Dante Minniti of the Universidad Andrés Bello were part of the team of scientists who discovered two new types of stars. All from the Cerro Paranal Observatory in the Antofagasta Region.

After ten years of studying the Milky Way, an international team of scientists led by Professor Philip Lucas of the University of Hertfordshire recently announced two major discoveries: a new type of old giant star, which fades over several years to invisibility, and a series of newborn stars that increase in brightness by up to 300 times over long timescales.

In addition to the United Kingdom, scientists representing South Korea, Brazil, Germany, Italy, and Chile participated. Among them, doctors Zhen Guo, Radostin Kurtev, and Jura Borissova, researchers at the Institute of Physics and Astronomy (IFA) of the University of Valparaíso, and Dr. Dante Minniti, Director of the Institute of Astrophysics at Universidad Andrés Bello. The work was carried out as part of the long-duration mapping of the Milky Way called ‘VISTA Variables in the Milky Way» (VVV), founded by Dr. Minniti.

Scientists studied the Milky Way in infrared light using the VISTA visible and infrared survey telescope at the Cerro Paranal Observatoryin the Antofagasta Region, part of the European Southern Observatory (ESO).

The team monitored about one billion stars and analyzed 222 of them, which showed the greatest change in brightness. Most of these stars are hidden from view in visible light due to large amounts of dust and gas in the Milky Way, but infrared light can pass through this tangle, allowing scientists to observe them for the first time.

Artist’s impression of an eruption in the disk of matter around a newborn star. The innermost part of the disk becomes hotter than the star itself. Image: VVV Team.

Approximately two-thirds of the stars were easy to classify. For the more difficult ones, they used ESO’s giant Very Large Telescope to obtain individual spectra of many of them. A spectrum indicates how much light can be seen at different wavelengths, giving a clearer idea of what is being observed.

Dr. Zhen Guo, IFA researcher at Valparaiso University, led the spectroscopic monitoring. «Our main goal was to find rarely seen newborn stars, also called protostars, while undergoing a big outburst that can last for months, years, or even decades. These eruptions occur in the slowly rotating disk of matter forming a new solar system,» he explained.

From Cerro Paranal, Scientists Make a Surprising Astronomical Discovery

The team discovered 32 erupting protostars whose brightness increased at least 40-fold, and in some cases, more than 300-fold; 25 of these stars were found from telescopes in Chile.»This includes 16 new, rarely encountered FUor-type objects, which expanded the current catalog of such variables by more than 30%,» Dr. Guo noted. Most of the eruptions are still ongoing, allowing astronomers to analyze a large group of these mysterious events for the first time throughout their evolution, from the initial quiescent state to maximum brightness and then into the decay stage.

However, the study also yielded something completely unexpected. 21 red stars near the Milky Way’s center showed ambiguous brightness changes during the ten years of observation. Compared with data from previous studies, analysis of the spectra of seven of these stars concluded that they were a new type of red giant star.

Artist’s impression of a cloud of smoke and dust thrown up by a red giant star. The star remains bright from the left, but when viewed from the right, it fades to invisibility.

Image: VVV Team.

Dr. Dante Minniti, Director of the UNAB Astrophysics Institute and leader of the VVV mapping, indicated that «these old stars remain silent for years or decades and then unexpectedly eject dust clouds. Then they look very red and dull for several years, to the point that sometimes we can’t see them at all.»

For the UNAB researcher, these discoveries represent a major scientific breakthrough: «Both the giant explosions in baby stars and the ejections of opaque dust clouds by the highly enriched stars of the Galactic center are phenomena never seen before, and open up other areas of research for astronomers.»

A further clue to this new discovery lies in the particular location of these giant variable stars. They are concentrated in the innermost part of the Milky Way, known as the Nuclear Disk, a region where stars tend to be richer in heavy elements than elsewhere in our galaxy. That richness should make it easier for dust particles to condense from gas in the relatively cool outer layers of red giant stars.

However, how this results in expulsing dense puffs of smoke remains a mystery. Matter ejected by old stars plays a key role in the cycle of the elements, helping to form the next generation of stars and planets. This was thought to occur mainly in a well-studied type of star called a Mira variable. The discovery of this new type of matter-spewing star could have broader significance for the propagation of heavy particles in the Milky Way’s Nuclear Disc and in metal-rich regions of other galaxies.