JWST found hundreds of ‘little red dots’ in the ancient cosmos, we are yet to know what they are.

Astrophysicists exploring the faraway universe with the James Webb Space Telescope (JWST), NASA’s most commanding telescope, have found a class of galaxies that gives competition to even the most skillful creatures in mimicry — like the mimic octopus. This creature can mimic other marine animals to evade predators. Require to be a flatfish? No problem. A sea snake? Easy.

When astrophysicists analyzed the first JWST images of the remote parts of the cosmos, they noticed a never-before-seen group of galaxies. These galaxies — some hundreds of them and termed the Little Red Dots — are very red and compact, and visible only during around 1 billion years of cosmic history. Just like the mimic octopus, the Little Red Dots confuse astronomers, as they look like different astrophysical objects. They’re either immensely heavy galaxies or modestly sized ones, each holding a supermassive black hole (SMBH) at its core.

One thing is absolutely certain, the typical Little Red Dot is small, with a radius of only 2% of that of our Milky Way galaxy. Some are even slighter. Astrophysicists who study distant galaxies and black holes are quite naturally interested in understanding the nature of these little galaxies. What powers their light and what are they, actually?

The mimicking contest

Astrophysicists analyze the light our telescopes receive from distant galaxies to assess their physical properties, for instance the number of stars they contain. We can use the properties of their light to study these galaxies (Little Red Dots) and figure out if they’re made up of lots of stars or if they have a black hole inside them. Light that come to our telescopes varies in wavelength from long radio waves to energetic gamma rays. Astrophysicists break the light down into the diverse frequencies and visualize them with a chart, called a spectrum. Sometimes, the spectrum has emission lines, which are ranges of frequencies where far more strong light emission occurs. In this case, we can utilize the spectrum’s shape to guess whether the galaxy is harboring a SMBH and estimate its mass. Likewise, studying X-ray emisson from the galaxy can disclose a supermassive black hole’s presence.

As the ultimate experts of disguise, the Little Red Dots appear as diverse astrophysical objects, depending on whether astrophysicists choose to study them using X-rays, emission lines or something else. The information astrophysicists have gathered so far from the Little Red Dots’ spectra and emission lines has led to two differing models explaining their nature. These objects are either host to a supermassive black hole or they are extremely dense galaxies containing billions of stars.