Chinese astronomers have investigated quasar candidates from the DESI Legacy Surveys (DESI-LS) photometry catalog. As a result, they detected 19 strongly-lensed, dual and projected quasars. The finding was reported in a paper published Jan. 15 on the arXiv pre-print server.

Quasars, or quasi-stellar objects (QSOs), are active galactic nuclei (AGN) of very high luminosity powered by supermassive black holes (SMBHs), emitting electromagnetic radiation observable in radio, infrared, visible, ultraviolet and X-ray wavelengths. They are among the brightest and most distant objects in the known universe, and serve as fundamental tools for numerous studies in astrophysics as well as cosmology.

Two quasars observed with a small separation can be, in some cases, lensed quasars—where the light from a single quasar is bent, resulting in two images of the same quasar. More often, such objects are dual quasars, which means that they are at similar redshift and physically interacting. However, the most common scenario is projected quasars—coincidentally appearing very close to each other along the line of sight, but actually at different redshifts.

In some cases, the black hole will even spew jets of plasma, millions of light-years across intergalactic space. The plasma gas is so hot that it’s essentially a soup of electrons moving close to the speed of light. These plasma jets glow at radio frequencies, so they can be seen with a radio telescope and are, aptly, named radio galaxies. In a recent episode of the astronomy podcast The Cosmic Savannah, I likened their appearance to two glow sticks (the plasma jets) poking out of a ball of sticky tack (the galaxy). Astronomers hypothesise that the plasma jets keep expanding outwards as time passes, eventually growing so large that they become giant radio galaxies.

Millions of normally sized radio galaxies are known to science. But by 2020 only about 800 giant radio galaxies had been found, nearly 50 years since they had been initially discovered. They were considered rare. However, a new generation of radio telescopes, including South Africa’s MeerKAT, have turned this idea on its head: in the past five years about 11,000 giants have been discovered.

MeerKAT’s newest giant radio galaxy find is extraordinary. The plasma jets of this cosmic giant span 3.3 million light-years from end to end – over 32 times the size of the Milky Way. I’m one of the lead researchers who made the discovery. We’ve nicknamed it Inkathazo, meaning “trouble” in South Africa’s isiXhosa and isiZulu languages. That’s because it’s been a bit troublesome to understand the physics behind what’s going on with Inkathazo.

In an article published in Physical Review Letters on Thursday, scientists carried out an innovative study testing the existence of mirror asymmetries in our universe by studying the handedness of the gravitational-wave emission from black-hole mergers detected by Advanced LIGO and Virgo.

The pillar of modern cosmology—known as the Cosmological Principle—states that, when observed at large scales, the universe is isotropic and homogeneous. This is, all observers in the universe will roughly observe the same structures regardless of where they are or where they look. As a consequence, the universe must not display a preference for stuff that rotates clock or anti-clockwise but, which is known as “mirror symmetry.”

Einstein’s theory of gravity, known as General Relativity, predicts that massive bodies can produce a type of radiation known as gravitational waves, which consist of distortions of spacetime that travel away from their sources at the speed of light. Such waves are produced in some of the most violent events in the universe, like supernovae, black-hole mergers or the big bang itself.

Two detected gravitational waves hint at the presence of ancient black holes in space.

Across cosmic history, powerful forces have acted on matter, reshaping the universe into an increasingly complex web of structures. Now, new research led by Joshua Kim and Mathew Madhavacheril at the University of Pennsylvania and their collaborators at Lawrence Berkeley National Laboratory suggests our universe has become “messier and more complicated” over the roughly 13.8 billion years it’s been around, or rather, the distribution of matter over the years is less “clumpy” than it should be expected.

“Our work cross-correlated two types of datasets from complementary, but very distinct, surveys,” says Madhavacheril, “and what we found was that, for the most part, the story of structure formation is remarkably consistent with the predictions from Einstein’s gravity. We did see a hint for a small discrepancy in the amount of expected clumpiness in recent epochs, around four billion years ago, which could be interesting to pursue.”

The data, which was published in the Journal of Cosmology and Astroparticle Physics and the preprint server arXiv, comes from the Atacama Cosmology Telescope’s (ACT) final data release (DR6) and the Dark Energy Spectroscopic Instrument’s (DESI) Year 1.