Astronomers with the Occasion Horizon Telescope have developed a brand new approach to observe the radio sky at a number of frequencies, and it means we are going to quickly be capable to seize coloration photographs of supermassive black holes.
Colour is an fascinating factor. In physics, we will say the colour of sunshine is outlined by its frequency or wavelength. The longer the wavelength, or the decrease the frequency, the extra towards the pink finish of the spectrum mild is. Transfer towards the blue finish, and the wavelengths get shorter and the frequencies greater. Every frequency or wavelength has its personal distinctive coloration.
After all, we do not see it that method. Our eyes see coloration with three various kinds of cones in our retina, delicate to pink, inexperienced, and blue mild frequencies. Our minds then use this information to create a coloration picture. Digital cameras work equally. They’ve sensors that seize pink, inexperienced, and blue mild. Your pc display then makes use of pink, inexperienced, and blue pixels, which methods our mind into seeing a coloration picture.
Whereas we won’t see radio mild, radio telescopes can see colours, generally known as bands. A detector can seize a slender vary of frequencies, generally known as a frequency band, which has similarities to the way in which optical detectors seize colours. By observing the radio sky at completely different frequency bands, astronomers can create a “coloration” picture.
However this isn’t with out its issues. Most radio telescopes can solely observe one band at a time. So astronomers have to look at an object a number of instances at completely different bands to create a coloration picture. For a lot of objects, that is completely high quality, however for fast-changing objects or objects with a small obvious dimension, it would not work. The picture can change so rapidly which you could’t layer photographs collectively. Think about in case your telephone digicam took a tenth of a second to seize every coloration of a picture. It could be high quality for a panorama picture or selfie, however for an motion shot the completely different photographs would not line up.
That is the place this new technique is available in. The workforce used a technique generally known as frequency part switch (FPT) to beat atmospheric distortions of radio mild. By observing the radio sky on the 3mm wavelength, the workforce can observe how the ambiance distorts mild. That is much like the way in which optical telescopes use a laser to track atmospheric changes. The workforce demonstrated how they will observe the sky at each a 3mm and 1mm wavelength on the identical time and use that to appropriate and sharpen the picture gathered by the 1mm wavelength. By correcting for atmospheric distortion on this method, radio astronomers might seize successive photographs at completely different radio bands, then appropriate all of them to create a high-resolution coloration picture.
This technique remains to be in its early levels, and this newest research is only a demonstration of the approach. Nevertheless it proves the strategy can work. So future initiatives such because the next-generation EHT (ngEHT) and the Black Gap Explorer (BHEX) will be capable to construct on this technique. And which means we can see black holes reside and in coloration.
Reference: Issaoun, Sara, et al. “First Frequency Phase Transfer from the 3 mm to the 1 mm Band on an Earth-sized Baseline.” The Astronomical Journal 169.4 (2025): 229.
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