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’ll quickly be capable to seize colour photos of supermassive black holes.
Coloration is an attention-grabbing 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 gentle is. Transfer towards the blue finish, and the wavelengths get shorter and the frequencies increased. Every frequency or wavelength has its personal distinctive colour.
After all, we do not see it that approach. Our eyes see colour with three several types of cones in our retina, delicate to pink, inexperienced, and blue gentle frequencies. Our minds then use this information to create a colour picture. Digital cameras work equally. They’ve sensors that seize pink, inexperienced, and blue gentle. Your laptop display screen then makes use of pink, inexperienced, and blue pixels, which tips our mind into seeing a colour picture.
Whereas we will not see radio gentle, radio telescopes can see colours, often known as bands. A detector can seize a slim vary of frequencies, often known as a frequency band, which is analogous to the best way optical detectors seize colours. By observing the radio sky at totally different frequency bands, astronomers can create a “colour” picture.
However this isn’t with out its issues. Most radio telescopes can solely observe one band at a time. So astronomers have to watch an object a number of instances at totally different bands to create a colour picture. For a lot of objects, that is completely positive, however for fast-changing objects or objects with a small obvious measurement, it does not work. The picture can change so shortly that you would be able to’t layer photos collectively. Think about in case your cellphone digicam took a tenth of a second to seize every colour of a picture. It will be positive for a panorama photograph or selfie, however for an motion shot the totally different photos would not line up.
That is the place this new methodology is available in. The staff used a way often known as frequency part switch (FPT) to beat atmospheric distortions of radio gentle. By observing the radio sky on the 3mm wavelength, the staff can observe how the ambiance distorts gentle. That is just like the best way optical telescopes use a laser to trace atmospheric adjustments. The staff 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 approach, radio astronomers might seize successive photos at totally different radio bands, then appropriate all of them to create a high-resolution colour picture.
This methodology continues to be in its early levels, and this newest research is only a demonstration of the approach. But it surely 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 methodology. And which means we can see black holes reside and in colour.
Reference: Issaoun, Sara, et al. “First Frequency Part Switch from the three mm to the 1 mm Band on an Earth-sized Baseline.” The Astronomical Journal 169.4 (2025): 229.
