Rainbow over the observatory photographed at Kit Peak National Astronomical Observatory in the United States | Sorae portal site to space

This rainbow appeared at Kitt Peak National Observatory in the Quinlan Mountains, Arizona, USA. It is a dazzling piece that combines a telescope that observes bright stars in the far reaches of space, and a rainbow that resembles a ladder that reaches high into the sky. Although it is a beautiful sight, there is actually a scientific relationship between rainbows and astronomical telescopes.

At Kitt Peak National Astronomical Observatory, more than 20 optical and radio telescopes, including the 4-meter Mayall telescope, are used to observe a variety of astronomical objects. Telescopes are not only used to obtain images similar to those seen with the human eye, but are also used for spectroscopic monitoring purposes to obtain the “spectrum” that indicates the brightness of each wavelength of electromagnetic waves coming from celestial objects. One way to obtain the spectrum is to scatter the light using a prism, but this mechanism is essentially the same as a rainbow that occurs when sunlight is refracted and scattered by raindrops. In other words, a rainbow can be described as a spectrum of sunlight obtained from raindrops as a natural prism.

The following image is a spectrum of the Sun taken by the McMath-Pierce Solar Telescope at Kitt Peak National Observatory. It is a collection of long and narrow band-shaped spectrum with a wavelength of 400 to 700 nanometers in a single image. As you move from left to right and from bottom to top, the wavelength of light becomes longer, in other words, the color changes from blue to red. I'm going.

A number of dark areas appear in the detailed spectrum of sunlight obtained through spectroscopic observation. This is called an “absorption line (dark line)” and is created when atoms, molecules and ions absorb electromagnetic waves of a specific wavelength. These absorption lines are also called Fraunhofer lines, after their discoverer.

In addition to absorption lines, the spectrum of celestial objects also includes bright lines called “emission lines”, which result from atoms radiating electromagnetic waves of specific wavelengths. Absorption lines and emission lines are also called “spectral lines.” Spectral lines obtained through spectroscopic observations reveal the chemical composition of an object and the direction of the line of sight.(*direction towards or away from the observer)You can know the speed of movement, etc.

[▲ فيديو مرجعي: فيديو يوضح كيف يتغير طيف النجم المضيف مع دوران الكوكب الخارجي]
(Credit: iso/l.way)

For example, in the field of extrasolar planets, which has been actively investigated in recent years, the slight oscillatory motion of the star during the planet's rotation can be interpreted as periodic changes in spectral lines. Methods for obtaining information about exoplanets based on the motion of stars are called the “radial velocity method” and the “Doppler shift method,” and they can determine the orbital period and minimum mass of the planet.

In addition, the spectrum of a star when a planet with an atmosphere undergoes a phenomenon called a “transit” in front of the star is called the transmission spectrum, and it contains only a small amount of light that has passed through the planet’s atmosphere. By comparing the transmission spectrum with the spectrum when no transit occurs, substances in the planet's atmosphere can be ascertained based on the absorption lines that appear in the transmission spectrum. In this way, modern astronomy obtains a variety of information about celestial objects through spectroscopic observations.

The image of a rainbow over the National Astronomical Observatory's Kitt Peak shown was initially published by NOIRLab as “Image of the Week” on March 20, 2024.

source

• NOIRLab – Primitive spectroscopy over KPNO

Text Editing/Syrian Studies Department