China tests ‘lobster eye’ telescope to capture precise X-ray images of the universe
- Lobster Eye Imager for Astronomy (LEIA) took high-quality images, including the centre of our galaxy, Magellanic Clouds and Scorpius constellation
- LEIA technology will be used on the Chinese-European Einstein Probe to be launched in late 2023
China has successfully tested the world’s first “lobster eye” space telescope that will allow scientists to capture X-ray images of the universe with unprecedented efficiency.
At 500km (310 miles) above the Earth, the 53kg (117lb) Lobster Eye Imager for Astronomy (LEIA) took high-quality images of X-ray sources – including the centre of our galaxy, the Magellanic Clouds and the Scorpius constellation – the team reported in the peer-reviewed journal The Astrophysical Journal Letters last week.
“We are very excited about LEIA’s results. They’ve shown that our technology works, and the observation precision exceeded our expectation,” said astrophysicist Yuan Weimin, the mission’s chief scientist from the National Astronomical Observatory in Beijing.
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LEIA’s technology will be used on the Einstein Probe, a much larger telescope that is being developed by Chinese and European scientists and will be sent into orbit late next year to revolutionise understanding of the X-ray universe.
X-rays are difficult to reflect and focus because of their high penetrating power. No existing X-ray telescope could take high-resolution images of a large enough area of sky, Yuan said.
Some could scan the sky within hours, but see only the brightest sources, while others could accurately observe one specific source, but not much else.
In the 1970s, biologists discovered how crustaceans such as lobster and shrimp had developed eyes to adapt to murky living environments under water.
Lobster eyes consist of numerous tiny square-shaped tubes, all pointing to the same spherical centre. Such a structure allows light from all directions to reflect inside the tubes and converge on the retina to give the lobster an unlimited field of view.
American astronomer Roger Angel proposed using a similar mechanism to help X-ray telescopes gain a wide and deep view at the same time.
However, his concept was a formidable engineering challenge that has only become achievable in recent years, as microprocessing technologies have matured and a technique known as micropore optics has become possible.
The main telescope on the Einstein Probe will comprise 12 modules, each containing more than 30 million square micropores. The pores measure 40 micrometres along the side and are coated with an ultrathin layer of iridium to increase reflectivity.
“The surface of the pores needs to be extremely flat and smooth, with less than one nanometre of error,” Yuan said. It took his team and engineers from North Night Vision Technology, a Nanjing-based company, a decade to develop the lobster-eye technology.
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The design allows the Einstein Probe to see an area of sky as big as 10,000 full moons. In comparison, the Chandra X-ray Observatory – Nasa’s flagship X-ray telescope – can capture images less than the size of one full moon in the sky.
The team also developed complementary metal oxide semiconductor (CMOS) sensors as detectors to convert X-rays to electric signals for digital processing.
While CMOS sensors have been widely applied in mobile phone cameras, “it’s probably the first time they are used for X-ray detection in space”, Yuan said. Compared with traditional CCD (charge-coupled device) sensors, CMOS sensors were much cheaper, less demanding in terms of cooling and had fast readout speeds, he said.
Once in orbit, the Einstein Probe is expected to detect a large number of faint or distant high-energy cosmic events for the first time. It will also be a game changer in the study of supermassive black holes at the centre of most galaxies.
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The European Space Agency and the Max Planck Institute for Extraterrestrial Physics in Germany contributed hardware for the 780 million yuan (US$111.6 million) mission. The observation data would be shared with colleagues in Europe and elsewhere, Yuan said.
Although scientists in the United States, Europe and Japan had proposed similar projects, none had made it to the design phase, Yuan said. “So when the Einstein Probe lifts off, there won’t be much international competition.”
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The telescope has a design lifespan of three years, but the team is aiming for five years, according to Yuan.
As the Einstein Probe’s pathfinder mission, LEIA was launched on July 27 from northern China’s Taiyuan Satellite Launch Centre on board SATech-01, an experimental satellite.
