Have you ever wondered what the universe looked like when it was much younger than today? How did galaxies form and evolve over billions of years? How can we see objects that are so far away and faint that they are beyond the reach of our eyes and telescopes?
These are some of the questions that scientists are trying to answer with the help of the James Webb Space Telescope, the most powerful and advanced space observatory ever built. Webb, which was launched in December 2021, is designed to observe the universe in infrared light, which can penetrate through dust and gas that block visible light. Webb can also see objects that are very distant and redshifted, meaning that their light is stretched by the expansion of the universe.
One of the first images taken by Webb is a stunning view of a galaxy cluster called El Gordo, which means “the Fat One” in Spanish. This image reveals hundreds of galaxies, some never seen before, and some distorted by the gravity of El Gordo. In this article, we will explain what El Gordo is, why it is interesting, and what we can learn from this image.
What is El Gordo and why is it interesting?
El Gordo is a cluster of hundreds of galaxies that existed when the universe was 6.2 billion years old, making it a cosmic teenager. It is the most massive cluster known to exist at that time, weighing as much as three quadrillion suns. El Gordo is also very hot, with a temperature of about 100 million degrees Celsius.
El Gordo is interesting for several reasons. First, it is a rare example of a massive galaxy cluster in the early universe, which can help us understand how such structures formed and grew over time. Second, it is a result of a violent collision between two smaller clusters, which can tell us about the dynamics and physics of such events. Third, it acts as a natural, cosmic magnifying glass through a phenomenon known as gravitational lensing.
Gravitational lensing is an effect of Einstein’s theory of general relativity, which says that mass curves space and time. When a massive object like El Gordo lies between us and a distant object, its gravity bends and distorts the light of the distant object, much like an eyeglass lens. This allows us to see distant and faint galaxies that would otherwise be invisible. Gravitational lensing also magnifies and stretches the images of these galaxies, making them easier to study.
What are the Thin One and the Fishhook?
The image of El Gordo shows two prominent features that are lensed background galaxies. The first one is called the Thin One, located just below and left of the image center. It is a spiral galaxy that is stretched and elongated by the lensing effect. The second one is called the Fishhook, a red swoosh at upper right. It is a disk galaxy that is twisted and curved by the lensing effect.
The light from these galaxies took 10.6 billion years to reach us, meaning that we are seeing them as they were when the universe was only 3 billion years old. This gives us a glimpse into the past, when galaxies were forming and changing rapidly.
The Thin One and the Fishhook are remarkable for their size and shape. The Thin One is about 26,000 light-years in diameter, which is about one-fourth the size of our Milky Way galaxy. The Fishhook is even smaller, with a diameter of only 13,000 light-years. These galaxies are much smaller than typical galaxies today, which suggests that they were still growing and merging with other galaxies at that time.
The shape of these galaxies is also unusual. The Thin One has a very thin disk with no bulge or bar in its center, unlike most spiral galaxies today. The Fishhook has a very warped disk with no spiral arms or symmetry, unlike most disk galaxies today. These shapes indicate that these galaxies were experiencing strong gravitational forces and tidal interactions with other galaxies or with El Gordo itself.
What can we learn from this image?
By analyzing the image, scientists were able to learn more about the background galaxies and their evolution. They found that star formation was already rapidly declining in the galaxy’s center, a process known as quenching. Quenching means that something stops or slows down the formation of new stars in a galaxy, either by removing or heating up the gas that fuels star formation, or by preventing new gas from entering the galaxy.
Scientists also found that the galaxy had a lot of dust in its center, which reddened its color and obscured its light. Dust is composed of tiny particles of carbon, silicon, iron, and other elements that are produced by dying stars or supernova explosions. Dust can tell us about the history and chemistry of a galaxy, as well as the types and ages of its stars.
These findings suggest that the galaxy was undergoing some environmental or internal changes that affected its star formation and dust content. For example, the galaxy could have been influenced by the radiation or winds from a nearby quasar, a supermassive black hole that emits powerful jets of energy. Or, the galaxy could have been involved in a merger or collision with another galaxy, which could have triggered star formation and dust production, but also disrupted the gas supply and stability of the galaxy.
Conclusion
In conclusion, this image of El Gordo is a remarkable example of how gravitational lensing can reveal distant and dusty objects never seen before, and provide a bounty of fresh science. It shows us how galaxies looked and behaved when the universe was much younger than today, and how they changed over time. It also demonstrates the power and potential of the James Webb Space Telescope for exploring the mysteries of the cosmos.
