Russian space agency Roscosmos published spectacular photos of Comet NEOWISE (C/2020 F3) and noctilucent clouds or polar mesospheric clouds (PMCs) above our beautiful planet Earth. This is something we’ve never seen before (a comet and ).

Forming about 45-55 miles (75-90 km) above polar regions in summer, noctilucent clouds are the Earth’s uppermost clouds and are only visible around twilight. PMCs are composed of ice crystals that glow bright blue or white when reflecting sunlight.

The photos below are taken by the Russian cosmonaut Ivan Vagner.

Noctilucent clouds need a combination of three factors: sufficient water steam, very low temperatures, and the presence of the smallest dust particles that condensed water, turning into ice crystals. Sunlight gives the clouds their characteristic electric blue and white color.

Comet NEOWISE and Noctilucent Clouds
Comet NEOWISE and Noctilucent Clouds. Photo by Cosmonaut Ivan Vagner (Roscosmos)
Comet NEOWISE and Noctilucent Clouds
Comet NEOWISE and Noctilucent Clouds. Photo by Cosmonaut Ivan Vagner (Roscosmos)
Comet NEOWISE and Noctilucent Clouds
Comet NEOWISE and Noctilucent Clouds. Photo by Cosmonaut Ivan Vagner (Roscosmos)
Comet NEOWISE and Noctilucent Clouds. Photo by Cosmonaut Ivan Vagner (Roscosmos)
C/2020 F3 (NEOWISE), or Comet NEOWISE is a newly-discovered comet. It was discovered on March 27, 2020, by the NEOWISE space telescope (a NASA infrared-wavelength astronomical space telescope launched in December 2009 and placed in hibernation mode in February 2011 and re-activated in 2013).

Comet NEOWISE

C/2020 F3 (NEOWISE) or Comet NEOWISE is a long-period comet (see notes 1) with a near-parabolic orbit (see notes 2) discovered on March 27, 2020.

It is known for being the brightest comet in the northern hemisphere since Comet Hale-Bopp in 1997 (which was dubbed the great comet of 1997).

Comet NEOWISE was widely photographed by professional and amateur observers and was even spotted by people living near city centers and areas with light pollution.

Comet NEOWISE was named after the NEOWISE project – the asteroid-hunting portion of NASA’s Wide-field Infrared Survey Explorer (WISE) mission. It was discovered by astronomers during the NEOWISE mission.

WISE was launched in December 2009 and surveyed the full sky in four infrared wavelength bands (3.4, 4.6, 12, and 22 μm) until the frozen hydrogen cooling of the telescope was depleted in September 2010. The survey continued as NEOWISE for an additional four months using the two shortest wavelength detectors.

The spacecraft was placed into hibernation in February 2011, after completing its search of the inner solar system.

During its primary mission, NEOWISE delivered infrared detections of more than 158,000 minor planets to the scientific community, including more than 34,000 new discoveries. NEOWISE data have been used to set limits on the numbers, orbits, sizes, and probable compositions of asteroids throughout our solar system, and enabled the discovery of the first known Earth Trojan asteroid.

NEOWISE then has been brought out of hibernation to learn more about the population of near-Earth objects and comets that could pose an impact hazard to the Earth.

As of mid-July 2021, NEOWISE is 25% through the 16th sky coverage since the start of the Reactivation mission.

Notes

  1. Long-period comets have highly eccentric orbits around Sun. Their periods range from 200 years to thousands or even millions of years.
  2. A parabolic trajectory is an orbit with the eccentricity equal to 1 and is an unbound orbit that is exactly on the border between elliptical and hyperbolic. When moving away from the source it is called an escape orbit, otherwise a capture orbit (see the image below).
Hyperbolic trajectory
Examples of orbital trajectories with various eccentricities. The green path in this image is an example of a parabolic trajectory. By ScottAlanHill, English Wikipedia, CC BY-SA 3.0, Link

Sources

M. Özgür Nevres
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