ET phones home!

February 23, 2021

A team of researchers from the Hebrew University of Jerusalem (HUJI) led by Dr. Assaf Horesh have discovered the first evidence of radio flares emitted only long after a star is destroyed by a black hole. Published in the periodical Nature Astronomy, the discovery relied upon ultra-powerful radio telescopes to study these catastrophic cosmic events in distant galaxies called Tidal Disruption Events (TDE). While researchers had known that these events cause the release of radio flares, this latest discovery saw those flares being emitted months or even years after the stellar disruption. The team was led by Dr. Horesh from the Racah Institute of Physics at the Hebrew together with the NASA Swift space telescope director Professor Brad Cenko and Dr. Iair Arcavi from Tel-Aviv University.

"According to existing theories of how these events occur, if no radio emission has been discovered in the immediate wake of the disruption, there is no expectation that one should occur later on" says Dr. Horesh. "However, we decided to conduct one last radio observation six months after the star was destroyed, and surprisingly we discovered bright radio emission. Once we discovered this delayed radio flare, we continued collecting data over a year, during which the radio emission faded away. Moreover, we found a second delayed flare, four years after the initial stellar disruption discovery. This is the first discovery of such delayed radio flares from such events, when a star is disrupted by a black hole."

Flares are believed to be caused by a huge velocity jet launched when the star is destroyed and sucked into the black hole or as a result of the outward explosion of debris from the explosion.

The analysis of the delayed radio flares lead the research team to several conclusions.

First, they now believe that new models have to be developed to explain such a long delay of radio flare emission. Second, it is possible that such delayed radio flares are a common phenomenon, but in order to find more of them teams will need to remain focused on observations surrounding the affected areas long after the initial disruption. Third, it is possible that a substantial amount of the stellar debris is eventually accreted (pulled in) to the black hole, but only long after the star was destroyed.

"What led to the delay and what is the exact physical process responsible for such late-time emission are still open questions", says Dr. Horesh. "In light of this discovery, we are actively searching for more such delayed radio flares in other tidal disruption events."

The Hebrew University of Jerusalem

Related Black Hole Articles from Brightsurf:

Black hole or no black hole: On the outcome of neutron star collisions
A new study lead by GSI scientists and international colleagues investigates black-hole formation in neutron star mergers.

The black hole always chirps twice: New clues deciphering the shape of black holes
A team of gravitational-wave scientists led by the ARC Centre of Excellence for Gravitational Wave Discovery (OzGrav) reveal that when two black holes collide and merge, the remnant black hole 'chirps' not once, but multiple times, emitting gravitational waves--intense ripples in the fabric space and time--that inform us about its shape.

Wobbling shadow of the M87 black hole
New analysis from the Event Horizon Telescope (EHT) Collaboration reveals the behavior of the supermassive black hole in the center of the M87 galaxy across multiple years, indicating the crescent-like shadow feature appears to be wobbling.

How to have a blast like a black hole
Scientists at Osaka University have created magnetized-plasma conditions similar to those near a black hole using very intense laser pulses.

Black hole collision may have exploded with light
Astronomers have seen what appears to the first light ever detected from a black hole merger.

Black hole's heart still beating
The first confirmed heartbeat of a supermassive black hole is still going strong more than ten years after first being observed.

Black hole team discovers path to razor-sharp black hole images
A team of researchers have published new calculations that predict a striking and intricate substructure within black hole images from extreme gravitational light bending.

Planets around a black hole?
Theoreticians in two different fields defied the common knowledge that planets orbit stars like the Sun.

Black hole mergers: Cooking with gas
Gravitational wave detectors are finding black hole mergers in the universe at the rate of one per week.

Going against the flow around a supermassive black hole
At the center of a galaxy called NGC 1068, a supermassive black hole hides within a thick doughnut-shaped cloud of dust and gas.

Read More: Black Hole News and Black Hole Current Events is a participant in the Amazon Services LLC Associates Program, an affiliate advertising program designed to provide a means for sites to earn advertising fees by advertising and linking to