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In 2023, John Silverman and his team downloaded telescope data about the depths of the Universe that had never been seen before. Silverman couldn’t directly collect the data because the telescope that was used, the James Webb Space Telescope, is orbiting the Sun around 1.5 million kilometres from Earth.
But why does the telescope have to be in outer space?
We often see historical pictures of famous astronomers peeking through handmade telescopes, scribbling observations in their notebooks. But despite everything they learned, the view of stars and galaxies through those telescopes wasn’t enough to answer some deeper questions. What are stars made of? Why do galaxies have strange shapes? To answer those questions, telescopes needed to evolve.
“The larger the telescope, the greater its resolution,” said Silverman, a professor at the University of Tokyo Kavli Institute for the Physics and Mathematics of the Universe. “You can look at where stars are forming, where there's the gas that produces those stars, and how that gas gets to the centre of galaxies. There, it can grow the black hole and also the bulge, a dense region of stars surrounding the black hole.”
Ever since he was a PhD student, Silverman has been using telescopes to find out how black holes were born. “We're looking for the relationship between the black hole and the bulge. Do they grow from a common fuel supply? To see the details of these components of galaxies, you need a large telescope.”
Basically, telescopes have become bigger to enable us to see further into the cosmos. This is important for Silverman, because his work focuses on the earliest black holes in the Universe. Even though light moves extremely quickly, the huge distances involved mean that the light from around those black holes takes a very long time to reach us. When the James Webb Space Telescope captures light from galaxies very far away, it’s looking back at those galaxies as they existed billions of years ago.
Placing the telescopes in space also eliminates a long list of problems that face land-based telescopes. For example, light is blurred and scattered by the atmosphere, and terrestrial telescopes also face interference from heat and light sources on Earth, as well as being unusable on cloudy or rainy days.
Full-scale James Webb Space Telescope model assembled on the lawn at NASA Goddard Space Flight Center.
Did you know?
The James Webb Space Telescope is located at the second Lagrange point, or L2, a point in space where the orbit stays aligned with the Earth as it moves around the Sun. This allows researchers on Earth to have continuous communication with the telescope. Currently, the telescope receives new command sequences and sends data twice a day.
The data Silverman got from the James Webb Space Telescope was about two massive galaxies hosting actively growing black holes called quasars. They’re located about 13 billion years away, in the furthest reaches of the Universe, which means the light the telescope collected left around one billion years after the Big Bang.
When gas falls into a black hole, it becomes incredibly hot and emits extremely bright light. This had created a challenge for Silverman’s team. Although these galaxies had already been discovered through the Subaru Telescope in Hawaii, the light was too bright. Even the Hubble Space Telescope couldn’t eliminate the bright light from the quasar so the researchers would be able to see the stars surrounding the black hole.
Scientists believe that there’s a relationship between a black hole and the mass of its host galaxy. By comparing black holes in galaxies nearer to Earth with the ones in the distant galaxies Silverman’s team studied, they can assemble a picture of how black holes have evolved since the early days of the Universe.
The Large and Small Magellanic Clouds, two companion galaxies to our own Milky Way galaxy, can be seen as bright smudges in the night sky in the centre of the photograph. Antennas of the Atacama Large Millimeter/submillimeter Array (ALMA) on the Chajnantor Plateau in the Chilean Andes. (Source: ESO)
The James Webb Space Telescope isn’t the first big telescope Silverman has worked with. He has also used the Atacama Large Millimeter/submillimeter Array (ALMA), a giant telescope in Chile which researchers use to study the molecular properties of gas and dust in space. ALMA also doesn’t look like the telescopes you can buy in a shop. It consists of an array of 66 giant radio antennas stretching between 7 metres and 12 metres across and spread across 16 kilometres on the Chajnantor plateau.
Silverman’s excitement is clear when he talks about working with ground-based telescopes. “Oh, I love it! As an observer, you wait for the sun to go down, and once it gets dark, you get very excited about what's possible. You can decide what you're going to do with this large telescope standing on this big mountain, high up and away from everything else, and it's nice and quiet with the whole Universe to explore.”
Silverman combines data from these telescopes in his research to take advantage of their different abilities. By comparing how the different telescopes see the same galaxies, he and his team can figure out the relationships between gases, star formation, and the black holes at the heart of galaxies.
Arp 87 is a stunning pair of interacting galaxies. Stars, gas, and dust flow from the large spiral galaxy, NGC 380 8, forming an enveloping arm around its companion. The shapes of both galaxies have been distorted by their gravitational interaction. Arp 87 is located in the constellation Leo, the Lion, approximately 300 million light-years from Earth. The corkscrew shape of the tidal material, which is also seen in other interacting galaxies, suggests that some stars and gas drawn from the larger galaxy have been caught in the gravitational pull of the smaller one. This image was taken in February 2007 with Hubble's Wide Field Planetary Camera 2 detector.
Source: ESA/Hubble
Further information
Prof John Silverman
[email protected]
Kavli Institute for the Physics and Mathematics of the Universe
Motoko Kakubayashi
[email protected]
Kavli Institute for the Physics and Mathematics of the Universe
