Noctilucent cloud

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Noctilucent clouds, or night shining clouds, are tenuous coud-like phenomena in the upper atmosphere . They consist of ice crystals and are only visible during astronomical twilight. Noctilucent roughly means "night shining" in Latin . They are most often observed during the summer months from latitutes between 50° and 70° north and south of the Equator. They are visible only during local summer months and when the Sun is below the observer's horizon, but while the clouds are still in sunlight. Recent studies suggest that increased atmospheric methane emissions produce additional water vapor once the methane molecules reach the mesosphere - creating, or reinforcing existing noctilucent clouds.

They are the highest clouds in Earth's atmosphere, located in the , mesosphere at altitudes of around 76 to 85 km. They are too faint to be seen in daylight, and are visible only when illuminated by sunlight from below the horizon while the lower layers of the atmosphere are in Earth's shadow.


Comet Neowise

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Comet NEOWISE passed closest to the Sun on July 3, 2020 at a distance of 0.29 AU (43 million km). The comet was less than 20 degrees from the Sun from June 11, 2020 until July 9, 2020. By June 10, 2020 as the comet was being lost to the glare of the Sun, it was apparent magnitude 7. When the comet entered the field of view of SOHO LASCO C3 on June 22, 2020 the comet had brightened to magnitude 3. As of July, Comet NEOWISE has brightened to magnitude +1, far exceeding the brightness attained by C/2020 F8 (SWAN), and the comet has developed a second tail. The first tail is made of gas and the later second tail is made of dust.

Closest approach to Earth will occur July 23, 2020 at a distance of 0.69 AU (103 million km). This perihelion passage will increase the comet's orbital period from about 4500 years to about 6800 years.