Comet NEOWISE has a sodium tail

(ORDO NEWS) — The brightness of the comet is difficult to predict because of the complexity of surface degassing, so any understanding of surface processes is useful to scientists. NEOWISE, formally known as C / 2020 F3, is a relatively bright object in the sky for observers in the Northern Hemisphere, but no one knows how the brightness of the comet will change as it approaches the Sun.

Images of the comet were obtained on July 8 using the Input / Output facility of the Institute of Planetary Sciences, which detected sodium in the tail.

NEOWISE and its like comets are made of dust, gas and plasma (ionized gas). When comets fly to the Sun from interstellar space or from the outer Solar system, sunlight causes the ice in the comet to turn directly into gas. When ice disappears, it pulls material from the surface of the comet.

Scientists can already sense cometary activity by looking at the dust coming from the comet, which can move faster if the particles are tiny and more easily affected by sunlight. Slower particles are usually larger and harder to move around. These individual particles affect the shape of the dust tail.

Like dust, atomic sodium is also exposed to sunlight, although it has more specific changes.

“Its momentum comes from a very specific wavelength of yellow light — the same color as streetlights with sodium vapor,” said research team member Jeffrey Morgenthaler, senior research fellow at PSI.

“Thanks to acceleration under intense sunlight, the sodium tail takes on a shape different from that seen in out-of-band filtered images, where reflected light from dust predominates. For comparison, the sodium tail is narrower, longer and directed directly from the sun, ”added Carl Schmidt, co-author and research fellow at Boston University.

The effect of sunlight on sodium atoms is stronger than its effect on dust and other gases that come from comets. However, due to solar emissions, it is difficult to see the sodium tail. Famous examples of sodium-tailed comets include Hale-Bopp (the famous comet of 1997) and the notorious comet ISON, which disintegrated during the passage of perihelion in 2013.

Morgenthaler and Schmidt will continue to monitor NEOWISE. They also use Monte Carlo computer models to simulate the tail of sodium, to estimate the rate and rate of degassing.


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