As the opening of 2022, the first large-scale meteor shower, the Quadrantids Meteor Shower, is approaching sunrise in the early morning of January 4, and the maximum ZHR (Zenithal Hourly Rate, the number of meteors that can be seen per hour when the radiation point is directly above the head under ideal viewing conditions) will reach 120, are you ready to watch?
Liu Xingyu (not)
The quadrant is a de-canceled constellation name after which the meteor shower radiation point is located at the junction of Draco, Shepherd, Ursa Major and Vicaris, making it a great fit for meteor showers observed in the Northern Hemisphere.
Image from Xinhua Net
The meteor shower is talking to you
Not only is it visually stunning, but the meteor shower is also sound!
When the meteor screamed across the atmosphere, it was nothing more than a silent show for us on the ground. Most meteors burn tens of kilometers above the surface, and when the sonic boom reaches our ears, it is already a few minutes after the meteors cross the night sky.
Reports of meteors over the years have mostly described it as a strange hissing sound in the air, like someone frying bacon. And because sound travels so slowly, even if the phenomenon is directly associated with meteors, these reports are often dismissed or hissed on Earth itself.
But researchers from Sandia National Laboratory and the Czech Academy of Sciences explained the mechanism behind the mysterious crackling sound. The study was published in The Nature journal Science Reports.
These sounds do not come from the impact of the meteor squeezing the air as it enters the atmosphere, with the particles of the air, but from the heat emitted when the meteor burns.
Meteors burn at temperatures comparable to those of the Sun, releasing more energy than they can reach the Earth's surface in the form of electromagnetic energy, the so-called thermal effect of electromagnetic radiation.
When certain objects absorb energy pulses, they heat up and expand rapidly, then collide with the surrounding air to produce a crackling sound.
The researchers tested the idea in an attenuated chamber capable of blocking out all external sounds. They aimed at a variety of different objects, including wood, paint, felt and wigs, with LED lights and microphones, all capturing the sounds described by meteor observers — bang, hiss, sand. When the LED light flashed at a frequency of 1000 Hz, the object emitted a 25 decibel sound, which was large enough for people to hear.
The experiment also confirmed the researchers' hypothesis that meteors are likely to transfer heat from the upper part of the atmosphere all the way to objects on the ground, which in turn makes a noise.
Originally in 1880, Alexander Graham Bell discovered that taking a slotted wheel to quickly cut off a beam of sunlight would make certain objects sound. This phenomenon is called the photoacoustic effect, which occurs when rapid energy pulses heat an object and push the air around it, while moving air particles are monitored in the form of sound waves.
Twinkling meteors
Most meteors do not burn steadily when they turn into fireballs, but rather a series of high-speed flashes. Since the process only lasts about a millisecond, we don't notice how fast it is at all.
The "Fireball Net", an astronomical organization owned by the Institute of Astronomy of the Czech Academy of Sciences, used a high-speed photometer to observe, and after tracking the light curves of more than 100 fireballs, it was found that the seemingly stable flame was actually a series of flashes. These pulses are similar to the flashes Bell saw in his experiments, and their energy is likely large enough to excite molecules of certain objects on Earth to jump to higher energy states.
They also found that materials that absorb light quickly but have poor heat conduction produce the closest sound, including dark clothes, hair, leaves, grass and a series of objects that match the sizzling sound in mid-air.
Experimental models show that as long as their pulses match the frequencies our ears can receive, meteors of the same brightness as the moon should be able to produce a photoacoustic effect that is audible to the human ear.
So, if you're lucky enough to spot a meteor, listen carefully, it may be talking to you.
Meteors and meteor showers are not the same
We often say meteors or meteor showers, but they don't just have a quantitative difference.
A meteor is a trail of light produced by a meteoroid entering and rubbing against earth's atmosphere, and when a group of meteors meets Earth, a meteor shower is formed.
Meteor swarms are often clumps of material formed by the eruptions of comets, and their orbits are very similar and nearly parallel.
Tonight, wrap up in a thick cotton coat and "listen" to the sound of the meteor shower with your important people and make your first wish for the New Year!
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