Every year, astronomers make breathtaking new discoveries that deepen our understanding of the universe and everything in it—and 2024 was no different.

Wendy Freedman, John & Marion Sullivan University Professor of Astronomy and Astrophysics, The University of Chicago

I found the first results from the Dark Energy Spectroscopic Instrument (DESI) exciting. The DESI group has spectra for 6 million (!) galaxies. They looked at how galaxies are distributed when you look back in cosmic time.

Einstein’s theory of gravity predicts what the large-scale distribution of galaxies should be—and it’s been tested for how structure grows over time in space.

While it would be surprising (but interesting!) if Einstein’s general theory of relativity didn’t hold up, the result rules out alternative theories of gravity and tests general relativity on very, very large scales.

And there will be much more to come from this survey as more spectra are acquired in the future.

George Efstathiou, Leverhulme Trust Emeritus Fellow, Emeritus Professor of Astrophysics, Kavli Institute for Cosmology, University of Cambridge

My favorite results of 2024 are the measurements of mass fluctuations from the Atacama Cosmological Telescope and from dark energy spectroscopic instruments.

It agrees really well with the predictions of general relativity. They provide further evidence that the universe is dominated by dark matter and dark energy.

Avi Loeb, Frank B. Baird Jr. Professor of Science, Director of the Institute for Theory and Computation, Harvard University

My favorite discovery of 2024 is Small red dotsa class of compact galaxies in early cosmic time discovered by the Webb telescope in March 2024.

Thirty years ago I published a paper predicting the existence of such galaxies based on the idea that a small fraction of all galaxies would be endowed with a small rotation that would allow the gas to self-gravitate into a small star-forming region. and could power the central supermassive black hole.

The observational discovery paper from 2024 was published here and my explanatory paper from 2024 (referring to my work 30 years ago) was published here.

Martin Rees, Fellow of Trinity College and Emeritus Professor of Cosmology and Astrophysics, University of Cambridge; Astronomer Royal

Although this is an obvious choice, I think the achievements of the James Webb telescope should be celebrated.

Thanks to its sharp angular resolution and ability to observe in the infrared band, it created a real breakthrough in our concept of newly forming galaxies.

We have a good understanding of how dark matter would clump together as the universe expanded, and we would expect the primordial gas to accumulate in the gravitational potential wells that these clumps provide.

The process by which the gas falls in is very complicated, and we expect it to be more complicated in these early systems because they are denser and the gas can cool more easily, meaning that shock waves would develop and star formation would occur more efficiently.

These galaxies have strange shapes because they have not yet reached equilibrium. (But contrary to what some authors claim, I don’t think anything in the data invalidates the long-loved “cold dark matter” cosmology. The messy physics of gas clumping together and turning into stars, but it’s amazing to have such direct insights into what it was like universe when it was only about 3 percent of its current age.)

The James Webb Telescope offered equal support for what I consider a second equally fascinating growth point in astronomy—namely, the properties of the “exoplanets” now known to orbit most of the stars in the sky.

In the long term, we hope to be able to obtain information about the atmosphere and surface structure of planets like Earth. This is a big challenge, but there is already interesting information about so-called ‘water worlds’ that are heavier than Earth but made of rock rather like Neptune in our own solar system.

This prompted some of the world’s leading microbiologists to focus on the origin of life – an unsolved problem that had been relegated to the “too difficult box” but is now being addressed because of the extraordinary motivation provided by the hope of observing other places where life could have originated