A bright comet that has been encountered in years has arrived, and it can be observed before sunrise in early July

Beijing News Express (reporter Zhang Lu) Bright comets visible to the naked eye are rare to see? Recently, a comet numbered C/2020 F3 (NEOWISE) will pass by Earth, triggering the "enthusiasm" of astronomical enthusiasts. "This is the most noteworthy astronomical hotspot in recent times." According to Kou Wen, a senior engineer at the Beijing Planetarium, in early July, the comet will rise an hour before sunrise and the public can observe it in the northeast direction of the sky. After the 15th, the comet will appear in the low western sky after dark, and it is recommended that the public use binoculars for observation.

A comet with a "long tail" appeared in the sky. Photo/Kouvin

In July, a "dark horse" comet appears

Comets are a class of small bodies in the solar system, the main component of which is water ice. According to Kou Wen, a senior engineer at the Beijing Planetarium, the comet's orbit is relatively special, most of the time at the edge of the solar system, and it is frozen when it is far away from the sun, known as a "dirty snowball".

When it travels near the Sun, it becomes active by solar radiation. At this time, the nucleus of the comet, which is only a few kilometers to a dozen kilometers in diameter, will spew out thin material to form a coma, which appears to become larger. Influenced by the solar wind, comets release volatile gases and blow dust, forming a tail. When the distance between the comet and the sun and the earth is more appropriate, people on the earth can see it.

There are not many comets, but bright comets visible to the naked eye shine in the sky are very rare. Kou wen said that the last time people in the northern hemisphere impressed people was 1997's Comet Hairp. "The last time I observed a bright comet was Comet ISON in 2013. For the public, the appearance of comets is an astronomical phenomenon that occurs once in more than a decade. ”

He said that the forecast of comets is not as accurate as that of solar and lunar eclipses, and everyone does not have a thorough grasp of their laws at present. This year, two comets have been predicted to be very bright, and everyone is looking forward to it, but they are both splitting and disintegrating when they are close to the sun, and they have already "disappeared" before they can be lit up.

Just when everyone regrets, the NEOWISE comet, which was first detected at the end of March this year, ushered in a "highlight" moment in July, surprising everyone with the trend of "dark horse".

Beginning in the middle of the year will appear in the western sky

The comet does not cross the sky like a meteor, and when viewed from Earth, it is relatively fixed in its position on the canopy during the observable period of time each day.

Comet NEOWISE is closest to the Sun in early July, about 40 million kilometers, and is theoretically its most active and brightest, Kouvin said. In early July, the comet rises about an hour before sunrise, allowing the public to look northeast to the sky. The comet is about first magnitude brighter and looks brighter than expected, but its observation conditions are not optimal due to the morning light, and the comet is visible for a shorter time because the sky will soon light up.

Currently, the comet has withstood the heating of the sun and is slowly approaching Earth. In mid-July, after about 15 days, the comet will appear low in the west after dark and will not be visible two hours after sunset. "At this time, although the comet's brightness is dimmed, it is higher in height and appears on the black canopy, and the observation conditions are more favorable." On July 23, Kouvin said, the comet will pass through perihelion, 100 million kilometers from Earth. In the near future, you can use binoculars to observe places that are less affected by city lights.

Comets last differently, with Comet Hairp in 1997 "lingering" for several months. Covin predicts that the NEOWISE comet will stay for about a month.

There is no scientific basis for considering comets "unlucky"

How are comets numbered and named? It is reported that the number of comets is in half a month, all the letters I and Z in English are removed, and the remaining 24 letters are in order, such as A in the first half of January, B in the second half of January, and then the comets found in the same half month are arranged in the same half month with 1 and 2 and other digits. The comet is designated C/2020 F3, indicating that it is the third comet to be discovered in the second half of March 2020.

"Comets can also be named after discoverers, and now many observations are viewed with telescopes, and comets can also be named after telescopes and so on." The comet is named after the survey program to discover it, called NEOWISE.

Because of their long tails, comets are known as "broomstick stars" and were thought to bring disaster in ancient times. "It's just superstition, in ancient times, comets looked different from other stars, and appeared irregularly, which could cause panic in everyone and thus be associated with unlucky things." In fact, there is no scientific basis for saying that the comet caused a disaster, and for astronomy enthusiasts, everyone is looking forward to the arrival of the comet." Kou wen said.

Beijing News reporter Zhang Lu

Edited by Li Guojun Proofreader Li Xiangling