At the core of our Milky Way galaxy lies a supermassive black hole, roughly four million times the mass of the Sun. These objects, known as supermassive black holes, grow in mass over time by consuming material that ventures too close. They are found at the center of most galaxies and are responsible for phenomena like galactic nuclei, jets, and quasars. Scientists believe these black holes formed before their host galaxies.
Until recently, however, scientists had never directly observed a black hole in action. That changed in late 2022 when researchers, through the Event Horizon Telescope (EHT) collaboration with observatories worldwide, captured the first-ever image of Sagittarius A*. Situated about 480,000 light-years away, the image reveals the black hole’s doughnut-shaped shadow and the glowing gases surrounding it.
These images are helping to test the theory that the rapid growth of supermassive black holes is tied to their ability to “eat” or accrete material. When a black hole eats, it releases electromagnetic radiation through jets that push particles away from its surface. The faster the black hole eats, the more electromagnetic radiation it blasts out, and the faster its size grows.
Scientists have long posited that this process should be slowed by something called the Eddington limit. This limit states that if a black hole’s accretion rate exceeds a certain threshold, then it should be slowed down and its growth arrested. However, the new observations show that a primordial black hole can increase even after it has passed this threshold.
To learn more about the behavior of these massive objects, astronomers turned to Webb, a space telescope launched in spring 2023. The telescope is designed to study a wide range of cosmic phenomena, from the first light in the universe to the atmospheres of exoplanets. Its combination of improved resolution, sensitivity, and wavelength coverage is expected to yield new insights into some of the most intriguing celestial objects.
But first, the telescope needs to get to work. To do so, it has to position itself about 1.5 million kilometers from Earth—that’s roughly the distance between the Earth and the Sun. The Sun telescope departed from its launch vehicle in less than 26 minutes, and after a month of fine-tuning its trajectory, it arrived at this spot called L2 in late January.
Live Science reports that this location is ideal for the telescope, as it is far enough from Earth to avoid interference from infrared radiation emitted by its atmosphere. Fortunately, the telescope has a considerable sun-shield to block the Sun from its mirrors and instruments. Once Webb is fully operational, it can take more detailed pictures of objects like Sagittarius A*. But it will also be able to probe the early universe with the help of its sophisticated infrared instrument, MIRI, which can detect faint objects despite their small sizes. This allows Webb to study how the first stars and planets formed.