Chapter 1: The Discovery

In an intriguing revelation, two research teams—one affiliated with Caltech and the other with the University of Toronto—have identified a supermassive black hole that consumed a star several decades ago, a phenomenon that had remained unnoticed until now. The investigation was sparked by two high school interns who were analyzing archived data from radio telescopes and stumbled upon an unusual object. This object was notably bright in the 1980s but had significantly dimmed by 2017.

Every galaxy, including our Milky Way, houses a supermassive black hole at its core, exerting gravitational influence over the surrounding stars. Typically, these stars maintain stable orbits, but occasionally, one ventures too close and falls victim to the black hole in a dramatic process known as ‘spaghettification’ or the ‘noodle effect.’

“The gravitational forces near the black hole can shred these unfortunate stars apart, transforming them into elongated streams that spiral into the black hole,” explained Vikram Ravi, an assistant professor at Caltech and the lead author of the study. “This is a chaotic event—stars do not vanish without a trace.”

As stars are consumed, their remnants orbit the black hole, emitting various wavelengths of light detectable by telescopes. In some instances, these remnants are expelled in powerful jets that produce radio waves. The occurrence of a black hole devouring a star is termed a tidal disruption event (TDE).

Section 1.1: New Insights from Radio Waves

Ravi and his colleagues have identified what seems to be a new TDE by examining archival data from radio telescope observations. This finding is particularly notable because, out of approximately 100 TDEs documented to date, this is only the second identified using radio waves. The first was discovered in 2020 by Marin Anderson, a postdoctoral researcher at the Jet Propulsion Laboratory (JPL), which is managed by Caltech on behalf of NASA.

“TDEs are usually detected through optical and X-ray observations, yet these techniques may overlook some events, especially those obscured by dust,” Ravi pointed out. “Our research highlights the potential of radio emissions in uncovering TDEs.”

The same TDE was also detected by astronomers at the University of Toronto, prompting a collaborative effort to publish their findings.

“An impressive array of radio observations is now available, enhancing our chances of discovering more sources of radio emissions,” noted co-author Hannah Dykaar from the University of Toronto. “Interestingly, neither of the two TDE candidates found via radio waves originated from the types of galaxies typically associated with TDEs. Identifying more of these radio TDEs could provide answers to ongoing questions regarding their galactic origins and prevalence in the universe.”

Section 1.2: The Role of Young Scientists

The newly identified TDE, designated J1533+2727, was first detected by Ravi’s team after two high school interns from Cambridge, Massachusetts, sifted through decades of radio data collected by the Karl G. Jansky Very Large Array (VLA).

Interns Ginevra Zaccagnini and Jackson Codd collaborated with Ravi from 2018 to 2019. By comparing radio observations taken years apart, they discovered that the object, J1533+2727, was relatively bright in the mid-1990s but had dramatically faded by 2017.

Like detectives piecing together an old mystery, they delved into the archives of the NRAO’s Green Bank 300-foot telescope and found that the object was even more luminous in 1986 and 1987, before the telescope’s collapse in 1988. The brightness of J1533+2727 has diminished by a factor of 500 since its peak in the mid-1980s.

All gathered evidence, including new data from the VLA, leads researchers to conclude that this TDE occurred when a supermassive black hole in a galaxy located 500 million light-years away consumed a star, subsequently expelling a jet traveling at nearly the speed of light. This jet is classified as a relativistic jet, and so far, only three other TDEs have been associated with such jets, all found in galaxies much farther away.

“This marks the first identification of a relativistic TDE candidate in the nearby universe, suggesting that these radio TDEs might be more common than previously assumed,” Ravi stated.

Chapter 2: TDEs as a Tool for Astronomical Research

The first video showcases the remarkable moment when a black hole consumes a star, highlighting the phenomenon captured for the first time.

This second video explores the dynamics of a black hole devouring a star, shedding light on the intricate processes involved in such cosmic events.

TDEs serve as essential instruments for probing supermassive black holes. Originally theorized in the 1980s, the first discovery occurred in the 1990s. With over 100 TDEs identified, they have emerged as powerful tools for examining the elusive phenomena surrounding black holes.

Caltech graduate student Jean Somalwar aims to discover more TDEs emitting radio waves through the VLA. Somalwar and her team recently reported one candidate, which is either a TDE or an enigmatic flash from an active supermassive black hole. Additionally, Somalwar, a new member of Ravi’s team, is leveraging data from the Zwicky Transient Facility (ZTF) at Caltech’s Palomar Observatory to find more TDEs emitting visible light. The ZTF routinely scans the night sky and has already identified over 15 such TDEs.

“TDEs illuminate extreme regions at the centers of galaxies that would otherwise remain hidden from view,” Somalwar remarked. “They have become invaluable research tools in recent years.”

Ravi and Somalwar presented their findings virtually on January 10 during the 239th meeting of the American Astronomical Society. Their study, conducted in collaboration with the University of Toronto, has been accepted for publication in The Astrophysical Journal and is currently available on arxiv.org. This article is based on a press release from Caltech.