Visible-light astronomy

A diagram of the electromagnetic spectrum with the Earth's atmospheric transmittance (or opacity) and the types of telescopes used to image parts of the spectrum.

Visible-light astronomy encompasses a wide variety of observations via telescopes that are sensitive in the range of visible light (optical telescopes). Visible-light astronomy is part of optical astronomy, and differs from astronomies based on invisible types of light in the electromagnetic radiation spectrum, such as radio waves, infrared waves, ultraviolet waves, X-ray waves and gamma-ray waves. Visible light ranges from 380 to 750 nanometers in wavelength.

Visible-light astronomy has existed as long as people have been looking up at the night sky, although it has since improved in its observational capabilities since the invention of the telescope, which is commonly credited to Hans Lippershey, a German-Dutch spectacle-maker,[1] although Galileo played a large role in the development and creation of telescopes. Visible-light astronomy continues to advance in the modern day, with projects such as the James Webb Telescope being projected for launch in the next few years.

Since visible-light astronomy is restricted to only visible light, no equipment is necessary for simply star gazing. This means that it's the most commonly participated in type of astronomy, as well as the oldest.

History

Beginning

Before the advent of telescopes, astronomy was limited solely to unaided eyesight. Humans have been looking at stars and objects in the night sky for thousands of years, as is evident in the naming of many constellations, notably the largely Greek names used today.

Fresco by Giuseppe Bertini depicting Galileo showing the Doge of Venice how to use the telescope

Hans Lippershey, a German-Dutch spectacle-maker, is commonly credited as being the first to invent the telescope. Lippershey is the first recorded person to apply for a patent for a telescope,[1] however it is unclear if Lippershey was the first to build a telescope. Based only on uncertain descriptions of the telescope which Lippershey tried to obtain a patent for, Galileo made a telescope with about 3x magnification in the following year. Galileo later made improved versions with up to 30x magnification.[citation needed] With a Galilean telescope the observer could see magnified, upright images on the earth—it was what is commonly known as a terrestrial telescope or a spyglass. Galileo could also use it to observe the sky, and for a time was one of those who could construct telescopes good enough for that purpose. On 25 August 1609, Galileo demonstrated one of his early telescopes, with a magnification of up to 8 or 9, to Venetian lawmakers. Galileo's telescopes were also a profitable sideline; selling them to merchants who found them useful both at sea and as items of trade. He published his initial telescopic astronomical observations in March 1610 in a brief treatise entitled Sidereus Nuncius (Starry Messenger).[2]

Modern day

In the modern day, visible-light astronomy is still practiced by many amateur astronomers, especially since telescopes are much more widely available for the public, as compared to when they were first being invented. Government agencies, such as NASA, are very involved in the modern day research and observation of visible objects and celestial bodies. In the modern day, the highest quality pictures and data are obtained via space telescopes; telescopes that are outside of the Earth's atmosphere. This allows for much clearer observations, as the Earth's atmosphere is not disrupting the image and viewing quality of the telescope, meaning objects can be observed in much greater detail, and much more distant or low-light objects may be observed. Additionally, this means that observations are able to be made at any time, rather than only during the night.

One of Hubble's most famous images, Pillars of Creation, shows stars forming in the Eagle Nebula (2014 image).

Hubble Space Telescope

The Hubble Space Telescope is a space telescope created by NASA, and was launched into low Earth orbit in 1990.[3] It is still in operation today. The Hubble Space Telescope's four main instruments observe in the near ultraviolet, visible, and near infrared spectra. Hubble's images are some of the most detailed images ever taken, leading to many breakthroughs in astrophysics, such as accurately determining the rate of expansion of the universe.

James Webb Space Telescope

The James Webb Space Telescope is the formal successor the the Hubble Space Telescope.[4] It is set to launch in March 30, 2021,[5] and is "one of the most ambitious and technically complex missions NASA has ever set its focus upon."[6] The James Webb Space Telescope is a space-based telescope, and is set to orbit near the second Lagrange point of the Earth-Sun system, 1,500,000 kilometers (930,000 miles) from Earth.[7]

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