Neutrinos are notoriously fussy particles. Hundreds of trillions go through a person’s body every second, but they hardly seem to interact with anything (although they actually do a lot). Even harder to find are the “high energy” neutrinos, which are believed to be the result of some of the most violent events in the universe. Now, researchers using NASA’s Swift telescope have for the first time found a high-energy neutrino from one type of this violent event – a tidal disturbance. But something was wrong.
Tidal disruptions occur when a black hole begins to tear a star apart. As part of the gravitational dance of these two massive objects, beams of particles can sometimes break out of the black hole when they swallow a stream of particles from the star. Astrophysicists have theorized that high-energy neutrinos could be generated in these jets, but one has not yet been observed.
Image from AT2019dsg circled in red. This galaxy, 690 million light years away, which could not be seen with the naked eye, was likely the source of a neutrino due to a tidal perturbation event occurring therein.
Photo credit: ZTF / Caltech Optical Observatories
One of these tidal faults is practically known as AT2019dsg, which was found in April 2019 by the Zwicky Transient Facility (ZTF), part of the Palomar Observatory. It is located in the constellation Delphinus in a galaxy about 690 million light-years away known (again practically) as 2MASX J20570298 + 1412165. Sometimes astronomers are great at coming up with quirky names or acronyms, but it seems that the sheer magnitude of the number of galaxies itself is taxing their copious naming creativity.
When AT2019dsg was first observed, astronomers followed a protocol they had established for observing tidal disturbances – they trained more observatories on it. In this case, visible, ultraviolet, and X-rays were provided by Swift, ESA’s XMM-Newtonian telescope also took X-ray data, and NRAO’s Very Large Array and MeerKAT telescope, operated by the South African Radio Astronomy Observatory, took on data on the radio.
In a NASA video discussing the process, the neutrino is traced back to its point of origin.
Photo credit: NASA’s Goddard Space Flight Center
With so much observation focused on a particular event, it was one of the most studied places in the entire universe. The brightness of the event peaked with no neutrinos associated with it. That is, until the IceCube Neutrino Observatory told the NSF they had captured a high-energy neutrino, and with the help of a team from the ZTF, they tracked the patch of sky where the neutrino came from to the same patch that AT2019dsg was on.
The only problem was that the neutrino appeared 5 months after the peak brightness of the tidal disturbance, long after some current theory suggested it was being generated. And no jets were observed, leading astronomers to believe that it was highly unlikely that a high-energy neutrino would have formed as part of the event.
UT video about IceCube, the neutrino observatory where the neutrino was originally detected by AT2019dsg.
But there it was, and the scientists calculated that there was a 1 in 500 chance of coming from something other than AT2019dsg in this part of the sky. Hence, new theories need to be developed to explain the discrepancy.
One of the clearest theories put forward by Walter Winter and Cecilia Lunardini of German Electron Synchrotron (DESY) and Arizona State University suggests that the presence of jets may have been masked by a cloud of debris. In this case, the neutrino-forming jets could have been present at the event, we simply would not have seen them. Your theory would also explain well why 98% of the X-ray brightness of the event disappeared in just 160 days. Another team led by doctoral student Robert Stein from DESY has a different idea: They believe that rapid cooling could explain the rapid decline in the observed X-rays.
Representation of the tidal disturbance event in the galaxy F01004-2237, similar to AT2019dsg. The release of gravitational energy as the star’s debris is accumulated by the black hole causes a flare in the galaxy’s optical light.
Credit and Copyright: Mark Garlick.
In any event, finding such a high-energy neutrino from a tidal perturbation event is a new advance in science and a tribute to the multispectral observational power exerted on the tiny patch of sky in which it was contained. As always, more data is needed to confirm either the theory for the existence (or lack of it) of the jets believed to be causing these neutrino bursts. If no jet was actually formed in the context of AT2019dsg, the finding is all the more interesting as the question arises: What then actually led to the creation of the neutrino?
NASA – NASA’s Swift helps bind neutrinos to the star-annihilating black hole
Natural Astronomy – A tidal disruption event that coincides with a high energy neutrino
Sci-News – Astrophysicists detect high energy neutrino from a tidal disturbance event
UT – Astronomers watch a star become spaghettified by a black hole
Lead Image Credit:
Depiction of a tidal disturbance event from the NASA video linked below.
Photo credit: NASA’s Goddard Space Flight Center