Maximum rain will occur at dawn on the 22nd and will have up to 15 meteors per hour in Brazil

It will take place at dawn on this Thursday (22), the maximum of Líridas, one of the main annual meteor showers. Líridas is considered a medium-intensity rain, which usually generates up to 18 meteors per hour in favorable locations. It is also the first of the main annual rains to occur after the "drought" of meteors that occurs after Quadrantids, which has its maximum on January 3. For ending this drought and also because Quadrantidas is practically not visible from the Brazil, for many, Líridas is considered the first of the great meteor showers of the year.

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Composite image of lyrid and sporadic meteors over New Mexico in 2012. Credits: NASA / MSFC / Danielle Moser
Composite image of lyrid and sporadic meteors over New Mexico in 2012.
Credits: NASA / MSFC / Danielle Moser

Líridas is the oldest known meteor shower, being reported for more than 2700 years by the Chinese. It occurs when the Land through the cloud of debris left by the Cometa C / 1861 G1 - Thatcher. For us Brazilians it is not such an intense rain. Here, we will have somewhere between 7 and 15 meteors per hour, but only in dark places, far from large urban centers. Still, it is an excellent opportunity to end abstinence from meteor watchers.

A meteor shower is an astronomical spectacle of the most democratic. It can be observed by anyone who has reasonable vision and access to some piece of heaven. You don't need telescopes, cameras or any special equipment. Just be willing to lose a few hours of sleep and look at the sky.

Meteors and Meteor Showers

A meteor, popularly known as a 'shooting star', is nothing more than a luminous phenomenon that occurs when a small fragment of space rock passes through our atmosphere at a very high speed. When this occurs, this fragment compresses and heats the atmospheric gas in front of you very quickly, forming a plasma bubble (heated and ionized gas) that shines like a lamp for a very short time, from a fraction of a second to, at most, a few seconds.

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Meteors are common phenomena and can be seen frequently every night. However, at certain times of the year, the Earth crosses an area of ​​the sky that has a greater amount of debris left by comets or asteroids. When this occurs, several of these fragments reach the atmosphere at the same time, forming the meteor showers.

All the meteors of the same rain reach the atmosphere in parallel to each other. That's because they follow roughly the same orbit as the comet or asteroid that gave rise to them. However, due to the perspective effect, for an observer on Earth, these meteors appear to originate from the same point in the sky, called radiant. In the case of Líridas, this radiant is in the Lira Constellation. So the name of this rain is Lyrids, because the meteors apparently come from the Lira Constellation.

Parallel meteors seen in perspective. Credits: BRAMON
Parallel meteors seen in perspective. Credits: BRAMON

Lyrids This Year

As the radiant of this rain is in the Lira, which is a Constellation of the Northern region of the Sky, it is best observed in the countries of the Northern Hemisphere, where it should present up to 18 meteors per hour. Here in Brazil, the further north the observer is, the more meteors will have a chance to see.

For much of the country, lyrids (as the Lyrid meteors are called) can be observed from midnight, but still in low intensity due to the presence of the Crescent Moon and the low elevation of the radiant in the sky. After the moon sets (around 1 am) and as the radiant becomes higher in the sky, the amount of meteors increases, until it reaches its most intense moment in the late morning, when up to 15 can be contemplated meteors per hour, depending on where the observer is.

Average rate of meteors per hour for Lyrids in 2021 under ideal observation conditions
Average rate of meteors per hour for Lyrids in 2021 under ideal observation conditions

All of these rates are estimated considering ideal observation conditions, that is, a cloudless night in a place away from the lights of big cities. These lights are harmful because they overshadow the faintest stars and meteors, so if you're in a city, try turning off as many lights as you can, or hope for a blackout that night!

As has been seen previously, Líridas is not a very intense meteor shower. But in fact, it is somewhat unpredictable, known to have outbreaks, that is, an increase in the rate of meteors per hour in certain years. So it was in 1982, when American observers were surprised by an outbreak of more than 100 meteors per hour. Japanese in 1945 and Greeks in 1922 also reported something similar. No 'outbreak' is planned for this year, but we will be rooting for Líridas to surprise us!

Lyrid meteors recorded from the Las Campanas Observatory in Chile. Credits: Yuri Beletsky
Lyrid meteors recorded from the Las Campanas Observatory in Chile. Credits: Yuri Beletsky

How to observe

Líridas is one of the most targeted meteor showers of the year. It takes place between April 16 and 25, which is the time when the Earth crosses the debris trail left by Comet C / 1861 G1 (Thatcher) in previous passages through the Inner Solar System. The most intense moment of this rain will be in the night between April 21st (Wednesday) and April 22nd (Thursday), when we pass through the densest region of this trail. That night is, without a doubt, the best time to observe Líridas, especially in the wee hours of the morning of the 22nd, when the meteor activity will be more intense. In the following night, (between 22 and 23 April), it will also be possible to observe some lyrids in the late morning, but in less intensity.

Lyrid Meteors over Lake Seč in the Czech Republic in 2020. Credits: Petr Horálek
Lyrid Meteors over Lake Seč in the Czech Republic in 2020. Credits: Petr Horalek

For much of Brazil, meteors will start to appear after midnight and will intensify until dawn. But if you are not in the mood to accompany the whole night, the ideal is to wake up around 02:03 or XNUMX:XNUMX in the morning and stay until it starts to get light.

The ideal spot for observation is anyone who is far from the lights of large urban centers, which in addition to obfuscating the faintest meteors, also diminish the sensitivity of our vision. Of course, in the midst of a pandemic, it is important to avoid group activities, and many people will prefer not to leave the house. Even so, it is possible to observe a meteor shower being in an urban area.

For this, it is necessary to look for a place as dark as possible and that has a good view of the sky. Try to turn off the lights around and block the lights that you can't turn off. This will help your vision to adapt to low light conditions making it more sensitive.

Although the Líridas radiant stays in the Lira Constellation, you don't need to be looking in the direction of this Constellation to see its meteors, as they will appear in all parts of the sky, just appearing to come from the direction of the Constellation, as shown in the image below.

Dawn sky on April 22, with the Líridas radiant close to the star Vega
Dawn sky on April 22, with the Líridas radiant close to the star Vega

So, those who are willing to sacrifice a few hours of sleep to accompany this phenomenon, just hope for a long time at night, look for a comfortable and suitable place to look at the sky and wait for the meteors.

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