Press release
June 18, 2024
In late 2019, the previously unremarkable galaxy SDSS1335+0728 suddenly began to shine brighter than ever. To determine the root cause, astronomers used data from several space and ground-based observatories, including the European Southern Observatory’s (ESO) Very Large Telescope (VLT), to track fluctuations in the galaxy’s brightness. In a study published today, they conclude that they are observing unprecedented changes in a galaxy—likely the result of the sudden awakening of the massive black hole at its center.
“Imagine observing a distant galaxy for years and it always seems quiet and inactive.“, says Paula Sánchez Sáez, an astronomer at ESO in Germany and first author of the study, published in Astronomy and astrophysics has been accepted.”Suddenly, its (core) shows dramatic changes in brightness that are different from any typical events we have seen before.That’s exactly what happened to SDSS1335+0728, which is now classified as an “active galactic nucleus” (AGN) – a bright, compact region powered by a massive black hole – after brightening significantly in December 2019. (1).
Certain phenomena, such as supernova explosions or tidal disruptions in which a star gets too close to a black hole and is torn apart, can cause galaxies to suddenly glow brighter. However, these fluctuations in brightness typically last only a few dozen or even a few hundred days. SDSS1335+0728 continues to brighten today, more than four years after it was first observed “brightening.” Moreover, the fluctuations observed in the galaxy, located 300 million light-years away in the constellation Virgo, are unlike any previously observed and point astronomers toward another explanation.
The team tried to understand these brightness variations using a combination of archival data and new observations from several locations, including the X-Shooter instrument on ESO’s VLT in the Atacama Desert in Chile. (2). Comparing data taken before and after December 2019, they found that SDSS1335+0728 is now emitting much more light in the ultraviolet, optical, and infrared wavelengths. The galaxy also began emitting X-rays in February 2024. “This behavior is unprecedented,” says Sánchez Sáez, also associated with the Millennium Institute of Astrophysics (MAS) in Chile.
“The most obvious explanation for this phenomenon is that we observe how the (core) of the galaxy begins to show (…) activity.“, adds co-author Lorena Hernández García of MAS and the University of Valparaíso in Chile.If true, it would be the first time we have observed the activation of a massive black hole in real time.“
Massive black holes – with masses more than a hundred thousand times greater than our Sun – exist at the centers of most galaxies, including the Milky Way.These giants are usually sleeping and not directly visible.“, says co-author Claudio Ricci of Diego Portales University, also in Chile.In the case of SDSS1335+0728, we observed the awakening of the massive black hole, which suddenly absorbed gas from its surroundings and became very bright.“
“This process (…) has never been observed beforesaid Hernández García. While previous studies have reported that dormant galaxies become active after several years, this is the first time that the process itself – the awakening of the black hole – has been observed in real time. Ricci, who is also affiliated with the Kavli Institute for Astronomy and Astrophysics at Peking University in China, adds:This could also happen to our own Sgr A*, the massive black hole (…) at the center of our galaxy“, but it is not clear what this probability is.
Further observations are needed to rule out other explanations. Another possibility is that we are observing an unusually slow tidal disruption event or even a new phenomenon. If this is indeed a tidal disruption event, it would be the longest and weakest such event ever observed.Whatever the nature of the fluctuations, (this galaxy) provides valuable information about how black holes grow and evolve.“, adds Sánchez Sáez.We assume that instruments such as (MUSE on the VLT or instruments on the future Extremely Large Telescope (ELT)) will make a crucial contribution to understanding (why the galaxy is becoming brighter).“
Endnotes
(1) The unusual brightness fluctuations of the galaxy SDSS1335+0728 were discovered by the Zwicky Transient Facility Telescope (ZTF) in the United States. Subsequently, the Automatic Learning for the Rapid Classification of Events (ALeRCE) algorithm, based in Chile, classified SDSS1335+0728 as an active galactic nucleus.
(2) The team collected archival data from NASA’s Wide-field Infrared Survey Explorer (WISE) and Galaxy Evolution Explorer (GALEX) satellites, the Two Micron All Sky Survey (2MASS), the Sloan Digital Sky Survey (SDSS), and the eROSITA instrument on IKI’s Spektr-RG space observatory and DLR. In addition to ESO’s VLT, follow-up observations were made with NASA’s Southern Astrophysical Research Telescope (SOAR), the W.M. Keck Observatory, and the Neil Gehrels Swift Observatory and Chandra X-ray Observatory.
Further information
This study was published in an article titled “SDSS1335+0728: The Awakening of a ∼106 M⊙ black hole” published in the magazine Astronomy and astrophysics (https://aanda.org/10.1051/0004-6361/202347957) has been published.
The team is composed of P. Sánchez-Sáez (European Southern Observatory, Garching, Germany (ESO) and Millenium Institute of Astrophysics, Chile (MAS)), L. Hernández-García (MAS and Instituto de Física y Astronomía, Universidad de Valparaíso, Chile (IFA-UV)), S. Bernal (IFA-UV and Millennium Nucleus on Transversal Research and Technology to Explore Supermass, Chile (TITANS)), A. Bayo (ESO), G. Calistro Rivera (ESO and Deutsche Luft- und Space Society (DLR)), FE Bauer (Instituto de Astrofísica, Pontificia Universidad Católica de Chile, Chile; Centro de Astroingeniería, Pontificia Universidad Católica de Chile, Chile; MAS; and Space Science Institute, USA), C .Ricci (Instituto de Estudios Ast rofísicos, Universidad Diego Portales, Chile (UDP) and Kavli Institute for Astronomy and Astrophysics, China), A. Merloni (Max Planck Institute for Extraterrestrial Physics, Germany (MPE)), MJ Graham (Institute of Technology of California, United States), R. Cartier (Gemini Observatory, NSF National Optical-Infrared Astronomy Research Laboratory, Chile, and UDP), P. Arévalo (IFA-UV and TITANS), RJ Assel (UDP), A. Concas (ESO and INAF – Osservatorio Astrofisico di Arcetri, Italy), D. Homan (Leibniz Institute for Astrophysics in Potsdam, Germany (AIP)), M. Krumpe (AIP), P. Lira (Departamento de Astronomía, Universidad de Chile , Chile (UChile) and TITANS), A. Malyali (MPE), ML Martínez-Aldama (Department of Astronomy, Universidad de Concepción, Chile), AM Muñoz Arancibia (MAS and Center for Mathematical Modeling, University of Chile, Chile (CMM-UChile)), A. Rau (MPE), G. Bruni ( INAF – Institute of Astrophysics and Space Planetology, Italy), F. Förster (Data and Artificial Intelligence Initiative, University of Chile, Chile; MAS; CMM UChile; and UChile), M. Pavez-Herrera (MAS ), D. Tubín-Arenas (AIP) and M. Brightman (Cahill Center for Astrophysics, California Institute of Technology, USA).
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Contact details
Paula Sanchez Saez
European Southern Observatory (ESO)
Garching near Munich, Germany
Tel: +49 89 3200 6580
E-mail: Paula.SanchezSaez@eso.org
Lorena Hernandez Garcia
Millennium Institute for Astrophysics (MAS)
Santiago, Chile
E-mail: lorena.hernandez@uv.cl
Claudio Ricci
Diego Portales University
Santiago, Chile
E-mail: claudio.ricci@mail.udp.cl
Barbara Ferreira
ESO Media Manager
Garching near Munich, Germany
Tel: +49 89 3200 6670
Mobile: +49 151 241 664 00
E-mail: press@eso.org
Markus Nielbock (press contact Germany)
ESO Science Outreach Network and House of Astronomy
Heidelberg, Germany
Tel: +49 6221 528-134
E-mail: eson-germany@eso.org
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This is a translation of ESO press release eso2409.