A New Celestial Object: Rubies

By Max Garsten;

Chapter Head; Choate Rosemary Hall, CT

When the James Webb Space Telescope began peering into the distant universe, astronomers expected to see the first faint galaxies and stars. But surprisingly, the astronomers also found tiny red dots that don't match any known celestial object. Researchers have been calling them little red dots (LRDs), or informally “rubies” (Nature, Ahart, 2025). These objects, seen with light from a universe less than two billion years old, have sparked debate about their origin and identity.

In the JWST infrared images, rubies look like small, sharp, red dots. The longer wavelengths found from rubies indicate either much solar dust or powerful embedded energy sources. Through inferring the stellar masses of the rubies, researchers believe some rubies are as massive as large galaxies today. However, the mass of a ruby is squeezed into an incredibly small volume (Nature, Ahart, 2025). Further research points to the interesting possibility that some rubies might be quenched galaxies. These are galaxies that formed their stars in one short burst (de Graaff et al., 2024). This research suggests that rubies are like the “seeds” of the large galaxies closer to us. The rubies could serve as snapshots during a brief phase of galactic evolution (de Graaff et al., 2024; Nature, Ahart, 2025).​

However, rubies might not all follow the same laws, or at least researchers don’t agree on what rubies truly are. Another possible explanation is that the rubies are supermassive black holes growing rapidly within a dense host galaxy (Nature, Ahart, 2025). Researchers who provide this explanation believe that the observed light is created by gas spiraling into a black hole. Then that gas is reddened by surrounding dust and compressed into a small space. This could mimic the appearance of an ultra-compact galaxy (Nature, Ahart, 2025).

Another possibility is that rubies are actually a blending of multiple objects, like galaxies and black holes close together, and that JWST can’t distinguish between these objects, creating the illusion of one red object (Nature, Ahart, 2025). A key problem in the LDR research is comparing the hypothesis of “massive compact galaxy,” “black-hole–dominated nucleus,” and “multiple blended objects” (Nature, Ahart, 2025; de Graaff et al., 2024).​

No matter which of the explanations for rubies prevails, they are already reframing how we think of the early universe. If the rubies really are quenched galaxies, then dense and “red and dead” galaxies already existed during the infancy of the universe. (de Graaff et al., 2024) This would force researchers to create models that accommodate such early bursts of star formation. However, if rubies are instead the supermassive black holes wrapped up within a host galaxy, then the rubies could be a more efficient pathway for those black holes to have formed, which would change astronomers beliefs about how quickly black holes can grow (Nature, Ahart, 2025; de Graaff et al., 2024).​

In order to truly uncover the identity of rubies, astronomers are planning on doing more observation through the JWST that could help separate the reddened old stars from the light of black holes (Nature, Ahart, 2025). High quality spectra will likely refine our understanding of the ruby systems. Studying multiple wavelengths, such as x-ray and radio waves, might be able to reveal more about the energy flow of the system (Nature, Ahart, 2025). With further research rubies will hopefully shift from mysterious red dots to important parts in understanding the story of the early universe.

Works Cited

de Graaff, A., et al. (2024). Efficient formation of a massive quiescent galaxy at red

shift 4.9. Nature Astronomy (as cited in Nature, Ahart, 2025).​

Nature, Ahart, 2025. Mysterious cosmic “dots” are baffling astronomers. What are they? Nature.