Why Do Astronomers Observe the Universe Using Different Radio Bands?
Radio light is available in an array of hues. These hues are represented by radio bands, and each band tells a different narrative about the cosmos it inhabits.
Radio astronomers look at the cosmos via a variety of wavelength bands. Using wavelengths as broad as 4 meters down to less than one centimeter, the VLA can gather a tremendous amount of data. For the ALMA radio telescope, scientists used frequencies ranging from a few millimeters to three-tenths of a meter. However, radio telescopes utilize a wide variety of wavelengths for a reason. For this, we need to look at the many ways things produce radio waves and how that light interacts with interstellar gas and dust.
Ionized gas is often used to generate long radio wavelengths like those detected by the VLA's Band 4. It shows us where the hot plasma in our galaxy is situated. The majority of neutral gas is transparent at these long wavelengths, making them very useful. That's good news since it implies that very little of the light is lost in transit. Certain atoms and molecules produce light with shorter wavelengths. The 21-centimeter line produced by neutral hydrogen is one of the most significant. Since hydrogen is the universe's most abundant element, seeing a galaxy's matter distribution at this wavelength.
Wavelengths between 10 cm and 20 cm are ideal (VLASS). Radio galaxies and supermassive black hole jets shine brightly in this region. VLASS has photographed approximately 10 million radio sources by scanning the sky at these wavelengths.
Synchrotron radiation is a technique used to produce ultra-short-wavelength light. Magnetic fields cause electrons to spiral along the magnetic field lines when they race past them at high speeds. As a result, they give out radioactive light. Magnetic fields around black holes may be mapped with the use of synchrotron radiation. A maser, often known as a microwave laser, is another technique that generates light in this wavelength range. In interstellar space, water pockets may produce coherent light with a wavelength of 1.3 centimeters. We are best acquainted with laser pointers, which emit coherent red light. Water masers have the advantage of casting a narrow band of light, making them ideal for measuring the expansion rate of the cosmos.
The study of cold gas and dust benefits significantly from the use of millimeter-wavelength radio waves. Many millimeter-sized dust grains are floating about in interstellar space, and they produce light at a wavelength on the order of their size. It may not be easy to see because our atmosphere absorbs so much of the morning at these short wavelengths. However, they are crucial for the study of young planetary systems since they contain essential information. While observing young stars with ALMA, scientists discovered gaps forming inside disks of gas and dust resulting from planets forming in their orbits. It's changing how we think about how planets originate in the universe.
ALMA's Band 6 catches the light with wavelengths ranging from 1.1 mm to 1.4 mm, making it one of the most intriguing radio bands. Molecular dispersion in planetary nebulae has been studied using this technique. Red giant stars produce heat. As a side benefit, it was also utilized to capture a picture of the galaxy's supermassive black hole, known as M87's heart. This first direct picture of a black hole was created by combining data collected by the Event Horizon Telescope (EHT), which utilized Band 6 receivers on radio telescopes all around the globe to gather data.
Our eyes cannot see radio light. Therefore it's simple to believe that all radio light is the same mistakenly. On the other hand, radio has a rainbow of hues, much like visible light, and radio astronomy is most effective when all the colors of the rainbow are used.