Size matters for a telescope’s image resolution. The bigger the viewing aperture, the more light it can collect. More light helps reveal fainter cosmic objects, as well as sharpen the images themselves.
For astronomers, the best results usually come from sharing images between telescopes around the world that are linked together. However, researchers from the University of California, Los Angeles (UCLA) and the National Astronomical Observatory of Japan have now demonstrated this networked approach isn’t always necessary. To obtain the sharpest-ever look at a distant star’s deep red disk of hydrogen-alpha spectral light, all they needed was a single telescope. As they explain in their study recently published in Astrophysical Journal Letters, this achievement relied on a fine-tuned optical fiber called a photonic lantern.
In traditional cameras, their diffraction limit (or the maximum amount of detail it can capture) is hampered by the wave nature of light. A photonic lantern sidesteps these waves by first splitting the light apart into individual wavelength shapes. The team said that this process is similar to separating a single musical chord into its notes. Astronomers then used the photonic lantern to further split apart these light wavefronts by color, like a rainbow.
“This device splits the starlight according to its patterns of fluctuation, keeping subtle details that are otherwise lost,” study co-author Yoo Jung Kim said in a statement. “By reassembling the measurements of the outputs, we could reconstruct a very high-resolution image of a disk around a nearby star.”
Kim and her teammates were initially hindered by visual noise coming from Earth’s atmosphere. Similar to how a hot, sunny day can make the horizon appear wavy, their telescope kept imaging objects as if they were wiggling. The solution’s first step came in the form of adaptive optics. This process constantly cancels out the atmospheric turbulence that causes these waves in real time. However, the team soon realized that they needed additional tools..
“Even with adaptive optics, the photonic lantern was so sensitive to the wavefront fluctuations that I had to develop a new data processing technique to filter out the remaining atmospheric turbulence,” Kim recounted.
After applying this filter, the team took an unprecedented look at a star in the Canis Minor constellation named beta Canis Minoris (β CMi). Located about 162 light-years away from Earth, β CMi is encompassed by a disk of hydrogen moving incredibly fast. Due to the Doppler effect, the speedy gas swirling towards Earth glows blue, while the receding gas glows red. The color shift, in then, makes the star system’s apparent light position moves with the wavelengths
After using their new technique , the astronomers measured the star’s color-reliant imagery shifts with five times the precision of previous observations. In doing so, they also realized something unexpected: the star’s disk is lopsided. According to Kim, it’s now up to another research department to figure out why this is the case.
“We were not expecting to detect an asymmetry like this,” she said. “It will be a task for the astrophysicists modeling these systems to explain its presence.”
