Since its launch on Christmas Day 2021, the James Webb Space Telescope has proven its worth year after year. 2024 is no exception. Here are just five times the ultra-powerful telescope has reshaped our understanding of the universe.
Large galaxies
THE James Webb Telescope was designed, in part, to search for the first galaxies in the universe. These galaxies are so far away from us that the expansion of the cosmos has shifted their light toward the redder, or infrared, part of the electromagnetic spectrum.
Astronomers used the observatory to find these ancient galaxies, and what they found, time and time again, were galaxies that were bigger and brighter than we expected. What is at stake here is our understanding of how galaxies form. The early universe appears to be a much more active place than we thought.
Galaxies appear and grow very quickly, in just a few hundred million years. Cosmologists don’t understand how galaxy growth processes can evolve so quickly, and astronomers hope that future observations from the James Webb Telescope will reveal the clues needed to solve this riddle.
Big black holes
JWST has spotted gigantic black holes this year. In May, astronomers I witnessed two massive beastseach weighing about 50 million times the mass of the sun, in the midst of a collision when the cosmos was about 740 million years old.
The large black holes of the early universe are even more difficult to explain than the large galaxies. Indeed, the only known way for black holes to form is through the death of massive stars, which leave behind black holes weighing up to several times the mass of the sun. From there, these tiny seeds must consume surrounding matter at a staggering rate and coalesce quite frequently to reach supermassive status at such an early cosmological age.
Astronomers don’t know what astrophysical processes can explain why these black holes got so big so early – but JWST could help answer that question, too.
Hubble voltage
Over the past decade, cosmologists have been losing sleep over a problem known as Hubble tension. Different methods for estimating the present expansion rate of the universeknown as the Hubble rate or Hubble constant, returns slightly different numbers.
The main difference is that the measurements taken from the early universe are slightly larger than those taken from the later universe. Astronomers have floated hundreds of proposals to resolve these tensions, ranging from trivial measurement errors to rewriting our understanding of dark energy.
At present, there is no commonly accepted explanation for this tension. And this year, the James Webb Telescope didn’t help after confirming that yes, Virginia, Hubble tension is real. So… thank you?
Carbon neutral
Life as we know it requires at least five key ingredients: hydrogen, oxygen, carbon, nitrogen and phosphorus. Take one away and the fundamental biochemical processes that make life possible would cease. Hydrogen was created in the first minutes of the Big Bang. The rest can only be done in the hearts of the stars. These ingredients only enter interstellar space – where they can participate in the formation of new stars and new solar systems – once these stars die.
A planet like Earth, rich enough in these elements to make life possible, is the product of several generations of stellar lives and deaths spanning billions of years. So it was a surprise when astronomers used the James Webb Telescope to find a carbon cloud formed only 350 million years after the Big Bang.
This pushes back the time when life could have first appeared in the cosmos. If a large amount of carbon was present in a cloud, then the other key ingredients were probably floating as well. And all of these elements could have shaped a planet before the universe was even half a billion years old. We don’t yet know if life existed at the time, but this discovery is a major clue that it was possible.
The first generation
The James Webb Telescope is an instrument of firsts: first galaxies, first black holes, first building blocks of life. But the real cosmic Holy Grail is finding the first stars. In the particular nomenclature of astronomy, the first generation of stars is known as Population III stars. No known Population III stars exist in the current universe, and astronomers suspect that no stars from this generation lived long.
These stars would be very different from modern populations, which require heavier elements to moderate their fusion reactions. But the first generation only had primordial hydrogen and helium to work with. These stars formed even before the first galaxies and ushered in the cosmic dawn – the first starlight in the cosmos.
Finding the first stars would be monumental, and this year, astronomers may have done it. The researchers discovered subtle hints of Population III stars in the combined light of the GN-z11 galaxya galaxy living only 430 million years after the Big Bang. Even if this galaxy existed long after the first stars appeared, it could retain a remnant population of these ancient sparklers. The discovery is still provisional, but if confirmed, it could go down in history as the most important discovery of the James Webb telescope.