A group of international astronomers recently discovered a galaxy that has undergone a classification change due to unique activity in its core. The galaxy, formerly known as PBC J2333.9-2343, has been reclassified as a giant radio galaxy four million light-years across. This new discovery was published in the Monthly Notices of the Royal Astronomical Society.

Not a radio galaxy, but a blazar

The galaxy, which was previously classified as a radio galaxy, is now classified as a blazar, according to the researchers. blazer is an active galactic nucleus (AGN) with a relativistic jet moving at close to the speed of light directed at the observer. A blazar is an extremely high-energy object and is considered one of the most powerful phenomena in the universe.

Meanwhile, another object that was initially mistaken for a galaxy has been identified as a black hole going straight to Earth. This object, named SDSS J103027.09+052455.0, was identified using data from the Sloan Digital Sky Survey. It was originally classified as a galaxy because of its bright core, but observations from Gran Telescopio Canarias in Spain revealed a black hole surrounded by a disk of gas.

What was the reason for the category change?

On PBC J2333.9-2343, the jet is heading straight for Earth from the plane of the sky, reversing its direction at an angle of up to 90 degrees. This resulted in radiation across the electromagnetic spectrum, causing the galaxy to change its classification. Astronomers used various electromagnetic spectral observations to learn more about the mysterious galaxy. They observed PBC J2333.9-2343 using radio, optical, infrared, X-ray, ultraviolet, and gamma-ray telescopes.

The team then compared the properties of PBC J2333.9-2343 with a large sample of blazar and non-blazar galaxies provided by the Rapid Event Classification for Machine Learning (ALeRCE) project in Chile, as well as data from the Zwicky Transient Facility. (ZTF) and End System Asteroid Earth Collision Alert (ATLAS).

Finally

The team concluded that there is a bright blazar in the center of the galaxy and two petals in the outer regions of the jet. These leaves are associated with old jets and are no longer fed by emissions from the core. Structures closer to the core represent younger and more active jets, while these are remnants of past radioactivity.

The team does not yet know what caused the sharp change in the direction of the jets. They suggest it could be a merger event with another galaxy, a relatively large object, or a powerful burst of intense activity in the galactic core after a rest period. The lead author of the paper and a research fellow at the Millennium Institute for Astrophysics, Dr. Lorena Hernández-Garcia said:

“Our hypothesis was that the relativistic jet of the supermassive black hole changed its direction, and we had to make many observations to confirm this idea. Seeing that the core no longer feeds the particles means they are remnants of past activity, while structures closer to the core represent younger and more active jets.”