Explained: Its eye on dark mysteries, Rubin will reveal the cosmos like never before

Indian Express

08-07-2025

How WAS the Milky Way formed? Does our Solar System have a ninth planet? Is there an asteroid that can pose a threat to Earth? What are dark energy and dark matter?
These are some of the questions that the Vera C Rubin Observatory, which released its first test images last month, is expected to answer. Located 8,684 feet above sea level atop the Cerro Pachón mountain in the Chilean Andes, the observatory will provide comprehensive images of the night sky unlike anything astronomers have seen before.
A technical marvel
The centrepiece of the observatory is the Simonyi Survey Telescope. This device is unique for three main reasons.
WIDE FIELD OF VIEW: Astronomers typically use the size of the visible surface of the full Moon to describe a telescope's field of view. The Hubble Space Telescope observes around 1% of the full Moon's disc, and the James Webb Space Telescope around 75% — using such telescopes is like looking into space through a straw.
The Rubin's telescope, however, is so wide-eyed that it effectively observes an area of the sky equivalent to at least 40 full Moons arranged next to one another. This is made possible due to its distinct design comprising three differently curved mirrors: a primary mirror with a diameter of 8.4 metres, a secondary mirror with a diameter of 3.5 m, and a tertiary mirror with a diameter of 5 m.
The primary mirror captures celestial light and reflects it upward to the secondary mirror. The secondary mirror then bounces the light to the tertiary mirror, which is the inner part of the primary mirror. From here, the light is sent up into a camera at the centre of the secondary mirror. This complex light path allows the camera to capture a large slice of the sky in a single image.
LARGEST DIGITAL CAMERA: The telescope has the largest digital camera in the world. It is the size of a small car, weighs 2,800 kg, and boasts a staggering resolution of 3,200 megapixels (the latest iPhone 16 Pro Max has a 48-megapixel camera). The camera can produce an image so rich in detail that it would take a wall of 400 ultrahigh-definition TV screens to display it in full.
Also, the telescope is designed in such a way that the camera's image sensors (which convert light into electrical signals that form digital images) will help scientists spot objects 100 million times dimmer than those visible to the naked eye. This makes the camera sensitive enough to capture a candle from thousands of kilometres away.
The camera has six filters designed to capture light from different parts of the electromagnetic spectrum. This will help astronomers gather information about various celestial objects based on the type of light they emit. For instance, young and hot stars emit ultraviolet light, whereas faint and distant red galaxies appear in infrared light.
RAPID MOVEMENT: It is not easy to move large telescopes. They usually take around 10 minutes to adjust their position so as to ensure that sensitive components do not wobble around during the movement. Scientists have to plan what they want to observe, and when, in advance.
The Simonyi Survey Telescope is the fastest-slewing telescope in the world, and takes just five seconds to move and settle from one target to another. This speed is due to the telescope's compact structure (owing to the three-mirror design), and its mount which floats on a film of oil.
Such speed will allow the telescope to snap up to 1,000 images a night, meaning it can capture the whole sky in just three days. Unlike other observatories, scientists at Rubin will not have to choose their targets.
'In a traditional observation, you decide on a target in a part of the sky and you take your telescope there. As we [the Rubin Observatory] are going to scan the whole sky, we will not start from a standard point A, and then move sequentially to different positions. We have instead built a script that will decide where to point at what time in the night,' Kshitija Kelkar, a senior operations specialist at the Rubin Observatory, told The Indian Express on a video call.
Revolution in making
The Vera Rubin Observatory will constantly scan the sky of the southern hemisphere for 10 years, gathering 20 terabytes of astronomical data each night. The observatory's software will automatically compare new images with older ones and generate an estimated 10 million alerts per night for each change detected in the sky.
Scientists hope that this treasure trove of data will help solve some of the biggest mysteries of the universe, and discover numerous celestial objects such as comets and asteroids. On June 23, when the first test images of the observatory were released, astronomers at the Rubin Observatory said that its software had identified 2,104 brand-new asteroids — including seven near-Earth objects — with merely 10 hours of engineering data.
The observatory is expected to catalogue more than five million asteroids, and roughly 100,000 near-Earth objects over the next 10 years, tripling today's inventory. It will become fully operational by the end of the year.
Jake Kurlander, a researcher at the University of Washington, told Earth.com, 'It took 225 years of astronomical observations to detect the first 1.5 million asteroids… Rubin will double that number in less than a year.'
The observatory will also play a crucial role in expanding our knowledge about the nature of dark matter and dark energy. While galaxies, stars, and planets make up 5% of the universe, dark energy makes up about 68%, and dark matter about 27%.
Scientists have known about these entities for decades — the observatory is named after American astronomer Vera C Rubin, who provided evidence about dark matter for the first time in the 1970s — but not much is understood about dark energy and dark matter.
Kelkar said, 'Rubin will be able to produce a very high definition map of the structure of the universe that is the best possible way to understand dark matter and dark energy.'