Weekly Space Image: Creation of an ‘Artificial Star’ in Hawaii by Astronomers


The Gemini North telescope, located at the Gemini Observatory on the summit of Mauna Kea in Hawaii, has become an instrumental tool for astronomers due to its adaptive optics. The telescope’s advanced features allow it to overcome the common problem faced by large telescopes: the twinkling of stars. This twinkling is caused by light passing through Earth’s turbulent atmosphere, resulting in blurred and moving images, a situation referred to as poor “seeing” by astronomers. This effect can interfere with astronomical observations for extended periods.

However, the Gemini North telescope, like many contemporary ground-based telescopes, utilizes adaptive optics to amend distortions caused by Earth’s atmosphere. A yellow laser, known as TOPTICA, generates an artificial star on the sodium gas traces in the atmosphere, approximately 50 miles above the Earth. Computers then minutely alter the telescope’s mirrors to correct any distortions.

The combination of lasers and computational power allows ground-based telescopes like Gemini North to achieve resolutions equal to, and at times surpassing, those of formidable space-based telescopes such as the Hubble Space Telescope and the James Webb Space Telescope (JWST). Once the blurring effect of Earth’s atmosphere is neutralized, Gemini North, with its larger mirrors, can capture higher-resolution images of stars, planets, and galaxies. For instance, the mirror of Gemini North measures 26.6 feet in diameter, compared to JWST’s 21.3 feet.

Astronomers anticipate that these adaptive optics will enable ground-based telescopes to directly image exoplanets. Nevertheless, images captured by the telescope may sometimes appear misleading. For instance, the orange TOPTICA laser may seem brighter than it actually is in long-exposure images. As a result, images may display star trails that are not typically visible to the naked eye.

In conclusion, the Gemini North telescope’s utilization of adaptive optics and computational power has revolutionized ground-based astronomical observations. By overcoming the distortions caused by Earth’s atmosphere, it has opened new opportunities for astronomical research, including the direct imaging of exoplanets. Despite the occasional misleading images due to long-exposure settings, the telescope represents a significant advancement in the field of astronomy.



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