A meteor? A meteor? A meteoroid. In the last minutes of Saturday, the sky over Portugal and Spain lit up for brief moments. There was a warning of Civil Protection and GNR patrols on the ground looking for fragments, near Castro Daire, but for a short time. Images of the event marked the entire Sunday morning on social networks.

In the morning it became clear what it was about: the scientific explanation and details arrived. However, there are still some doubts about this type of phenomenon. Common, but also rare. Let’s understand why.

What phenomenon was this?

The phenomenon observed with less than fifteen minutes left until Sunday the 19th was caused by a meteoroid. It is a rock that, in this case, broke off from a comet somewhere in space and then entered the Earth’s atmosphere. It passed that barrier at 161 thousand kilometers per hour, that is, 45 kilometers per second. It caught fire as soon as it crossed the atmospheric barrier, with which it came into contact, thus becoming incandescent and gaining the brightness that can be seen in the sky. Several images of the moment immediately began to be shared on social networks.

The first news about the meteoroid in the Portuguese sky is at 11:50 p.m. Shortly after midnight, Civil Protection opened a file for the fall of a meteorite (we will explain the differences) in the Pinheiro region, Castro Daire, Viseu district. There were still GNR patrols in the Pereira area and the Montemuro mountain range, particularly in the surrounding wind farms, because some people “reported seeing a flash in an antenna area.” This alert was removed shortly after and is very rare. The search for fallen fragments was abandoned due to reports of an explosion.

Did it hit the Earth?

No. Geophysicist Rui Gonçalves, interviewed by Agência Lusa, maintains that it is necessary to gather more data to be able to calculate the trajectory and only then conclude if a fragment, a meteorite, fell and where.

The opinion differs from the conclusion presented by the Institute of Astrophysics of Andalusia, which centralizes the information obtained by the detectors of the SMART project (a network that monitors the atmosphere to evaluate the impact of possible objects in the solar system) and which is a specialist in analyzing these episodes. It was this institute that on Sunday morning provided all the scientific information about the phenomenon.

According to astrophysicist José María Madiedo, head of the institute’s SMART project, the meteoroid did not reach the ground. It will have become extinct at a height of 54 kilometers, over the Atlantic Ocean, already above the area of ​​Porto and Braga, after a low journey (very low, less than 10 degrees) of about 500 kilometers in which it crossed Portugal towards the northwest. since it entered the atmosphere in the Badajoz area, at 122 kilometers above sea level.

However, on its way, the incandescent rock suffered several explosions that can be seen in the video released by the institute. This means that the stone breaks, fragments (at which point it becomes even brighter and noises can be heard) and these fragments or debris can reach the ground.

For Rádio Observador, researcher and astrophysicist Nuno Peixinho admits that “there may be fragments that, when released, could have fallen.” But he considers that “the probability is low.” The Andalusian Institute of Astrophysics affirms that this did not happen.

But after all, wasn’t it a meteorite?

No. A meteoroid is a rock that sails in space and can originate from a comet, a planet and even an asteroid. When a meteoroid enters the Earth’s atmosphere, it is called a meteor. However, if it does not disintegrate in the atmosphere and hit the ground, it cannot be called a meteorite. Only if it falls does it receive its name.

Normally, these rocks enter the Earth’s atmosphere at a speed of more than 72 thousand kilometers per hour. In this case, this speed was double, which is significant. And they become visible when they are about 100 kilometers above sea level. Meteoroids can originate in interstellar space, but they often originate in the asteroid belt, the region between Mars and Jupiter, where at least 40,000 asteroids travel.

Where did it enter the atmosphere and what route did it take?

The meteoroid entered the atmosphere at Don Benito, near Badajoz, in southwestern Spain, at about 161,000 kilometers per hour and at an altitude of 122 kilometers. The trajectory was almost parallel and close to the Earth, 10 degrees. Data from the Institute of Astrophysics of Andalusia also add that the meteoroid then traveled about 500 kilometers to the northwest, crossing Portugal. But it was visible in many other areas, from Madrid to Cádiz, in northern Spain, from Évora to Lisbon, through central Portugal, to Porto, Viana do Castelo and Braga.

The Institute’s video allows us to see the areas where it could have been seen.

Where was it seen?

In Spain there are reports from Madrid, Cádiz, Jaén and Galicia. In Portugal, the meteoroid was seen from Lisbon, Coruche, Santarém, Porto, Braga, Vila Real and Viseu, at least.

Geophysicist Rui Gonçalves goes further and indicates that the phenomenon was observed from the French coast to the south of the Algarve. Once again, the YouTube video of the Andalusian Institute of Astrophysics clearly shows the route and coverage radius to observe the phenomenon.

Why do the testimonies speak of a blue or green light when the rock passes?

According to astrophysicist José María Madiedo, the meteoroid was so bright that it could be seen 800 kilometers away. Some people saw a green light and others a blue light as they passed by.

Researcher Nuno Peixinho had already explained to the Lusa agency that, due to the speed they reach, the rocks reach such a high temperature that “this temperature vaporizes everything”: “As they move at several kilometers per second, against the air, The pressure that makes it in the atmosphere that the temperatures easily reach 25,000 degrees, and at that temperature it vaporizes everything.”

This process results in the trail of light seen in the Portuguese and Spanish skies, and which depends on the chemical composition of the rock. For Rádio Observador, the expert adds that when nickel vaporizes “it gives a green color.” Magnesium, “when vaporized, gives a blue color.” Thus, everything indicates that the meteoroid “would contain nickel and magnesium, which, in fact, is quite common in these rocks that come from space,” he says.

If the meteoroid has sodium in its chemical composition, then it should emit yellow light. If it is composed of calcium it will have a violet light and if it is composed of nitrogen and/or oxygen it will show a red light.

What impacts were recorded?

In addition to the intense luminosity, the Portuguese Institute of the Sea and the Atmosphere tells the Observer that “some tremor was detected in the seismic network due to the shock wave.” Some social media users report hearing an explosion. According to Nuno Peixinho, quoted by CNN, this noise “only means that it was big.” That is, a rock that already has a significant size.

“Shaking and making noise is normal, because it is the shock wave. It’s like a supersonic plane passing by. For some reason, the military is prohibited from flying planes at speeds faster than the speed of sound over cities. If they passed they would cause damage, such as broken glass, for example,” he explains. The rock that crossed the Portuguese skies this Saturday was traveling at low altitude and at high speed.

“There was a lot of energy in the atmosphere. It wasn’t big enough or close enough to, for example, break glass. But he was already big,” adds Nuno Peixinho.

There is danger?

Could have. As the rock moves forward, some fragments break loose. They are normally small in size, simple rubble, dust, because they fall apart when they break due to the speed at which the stone travels. But that is not always the case. They can be larger and sometimes fall on houses or structures, causing damage.

About a year ago, in the United States of America, a meteorite measuring about 10 by 15 centimeters crashed into a house during the night. The family, who were not injured, said the roof had been hit by a burning black object the size of a potato. At the time, experts believed the meteorite had broken off from Halley’s Comet.

In 2021, a similar situation occurred in Canada. A woman woke up in the middle of the night to the sound of a meteorite that had passed through the ceiling and landed on the bed where she was sleeping, without injuring her.

Is this rare to happen?

No. An example of this is the well-known — and frequent — “star showers,” which are, in reality, meteorites that enter the Earth’s atmosphere at high speed. Every day, 25 million meteorites, micrometeoroids (small grains of sand), and other space debris fall to Earth’s soil. According to CNN, in the last 10 years the Earth has been hit by at least 26 meteorites. The largest in the last 100 years fell in Russia, in February 2013: 1,500 people were injured and more than seven thousand homes were damaged, causing what became known as the Chelyabinsk meteor. It was 17 meters in diameter.

Speaking to Rádio Observador, researcher Nuno Peixinho assures that “every year there are always several of these large meteors around the world.” But since Portugal is “a smaller country,” “we see this phenomenon less frequently,” he summarizes. However, the rock that marked Saturday night would have been of a certain size and entered the atmosphere at high speed, in addition to moving at a very low altitude. This type of box, known as a bolide, is rarer and is characterized by being extremely shiny and beautiful.

The last time a large meteor “invaded” the Portuguese skies was in March. The “fireball” entered the atmosphere at 60 thousand kilometers per hour. At that time, some people said they saw a large flash and felt their houses shake. Before, in January of this year, a meteor had already crossed the skies of Portugal. Once again, entry into the atmosphere occurred across Spain, near Badajoz, at about 89,000 kilometers per hour. Both events were also recorded by the SMART project of the Andalusian institute.