Asteroid is a rocky body that look like stars, is smaller than a planet and larger than a meteoroid, which orbits the Sun in an orbit interior to that of Neptune.

Asteroid viewed from Earth, these bodies look like stars.

The name “asteroid: star shape” was given by John Herschel, the son of the famous astronomer William Herschel.

Violent visitors uninvited.

Thousands of asteroids cross the skies. Some pass far from Earth, others just skim it and a few fall into it.

Review of five of them. Three recent ones, one old and one very old.

Asteroid in the Canary Islands

On the night of March 8, 2015, off the coast of Gran Canaria, a fireball was sighted that ended up falling into the sea.

The asteroid that was seen in GranCanaria Credit: web “”.

Asteroid 2012 DA14

This small near-Earth asteroid  passed very close to Earth on February 15 2012. So close that it will pass inside the ring of geosynchronous weather and communications satellites.

Although its orbit is perfectly known, it has not stopped causing concern in the population.

2012 DA14
Asteroid was named 2012 DA14. Credit: NASA, web

The exact calculation of its trajectory and the distance at which it would pass in its closest approach to Earth was carried out in NASA’s JPL laboratory in Pasadena”.

Daniel López, astrophotographer author of the website Cielos del Teide, recorded this incursion into our skies.

This video was nominated by NASA as the best of those published on that occasion.

A meteorite hit Chelyabinsk

Chelyabinsk is a city located at 61º north latitude and has more than one million inhabitants. In terms of population, it is the ninth city in Russia.

On February 15, 2013, an unexpected visitor, in the form of a meteorite, fell in Russia, impacting the city of Chelyabinsk.

This meteorite was not detected before entering the atmosphere, but the great igneous ball and the explosion were recorded on video by security cameras and by the mobile phones of many citizens.

This is the largest meteorite recorded in the last hundred years. Credit: web “”.

Three thousand buildings were seriously damaged and there were more than a thousand injured.

According to the first data collected and those revealed by NASA, it is estimated that the meteor was about 15 meters in diameter, weighed about 10,000 tons and penetrated the Earth’s atmosphere at about 64,000 km / hour, 18 km per second.

The meteorite it entered the atmosphere at 18 km / s and released a total energy of about 500 kilotons.

At the moment not all the data of its trajectory are known, but it is believed that the meteorite comes from the asteroid belt located between Mars and Jupiter.

Asteroid that fell on Tunguska

In the early morning of June 30, 1908, a powerful explosion shook the entire region around Tunguska, near the Podkamennaya River, in Siberia.

Artist’s impression of the asteroid that fell on Tunguska Credit: NASA, web “”

Because no fragments were recovered, various theories have been published. It is speculated that it was a fireball about 37 meters in diameter, possibly rocky and that it detonated in midair.

The proven fact is that there was a great fire and that an area of ​​2,150 km² was covered by trees that were felled, which broke windows 400 km away.

The asteroid destroyed a great area. Credit: NASA, web “”

For several days, nights were so bright in parts of Russia and Europe that it was readable after sunset without the need for artificial light.

The most accepted theory is that a small asteroid composed of ice and dust, exploded before reaching Earth and was completely vaporized by the friction with the Earth’s atmosphere.

The asteroid that caused the extinction of the dinosaurs

It is known that many times in the past there has been the fall of asteroids greater than 50 m in diameter.

One of them killed the dinosaurs and killed more than 90% of species and living beings.

Using rock cores from Chicxulub crater, geologists piece together a new timeline of the destruction that followed impact. Credit:, web “”.

About 251 million years ago, a mass extinction occurred on Earth.

This event defines the boundary between the Permian and Triassic periods. It was the largest extinction ever on Earth; 96% of the marine species and 70% of the terrestrial vertebrate species disappeared there.

Only 10% of the species present survived at the end of the Permian.

For a long time the Earth was only a desert wasteland whose dominant species on land were extingt.

Where do asteroids come from?

The Hungarian astronomer, Baron Franz Xaver von Zach (1754 -1832) born in Pest, Hungary, was appointed in 1791 as Director of the new Seeberg Observatory, in Gotha, Germany.

Von Zach organized a group of 24 astronomers, dedicated to the objective of preparing a systematic search for the “lost planet” which, according to the prediction of the Titius-Bode law, must be located between Mars and Jupiter.

Von Zach
Franz Xaver von Zach Hungarian astronomr. Credit: web , “”

According to the Titius-Bode law, formulated in 1766, and without knowing why,

  • by adding the number 4 to each number in this series: 0, 3, 6, 12, 24, 48, 96, 192 and 384 ,
  • then dividing each result by 10, you can have the different distances of the planets from the Sun,
  • the value of 1 (one) corresponding to the Earth, a figure equivalent to an Astronomical Unit (ua = 150 million kilometers, which is the from the Earth to the Sun).

    Titius Law
    Titius-Bode law. Credit: web “”

At that time, only the classical planets Mercury, Venus, Earth, Mars, Jupiter and Saturn that are distant from the Sun were known: 0.38; 0.72; 1; 1.52; 5.2; 9.54 ua (asteroids unknown, at an average of 2.7 ua).

On January 1, 1801, the monk Giuseppe Piazzi, from Palermo, was reviewing a catalog of stars and saw “something like a comet.”

Other astronomers calculated the orbit of the object, which they named Ceres, and found that it responded to the location of the planet they were looking for.

Asteroid Belt

In the following years, a total of 463 asteroids were discovered, of which all but one – Eros – always move between Mars and Jupiter, in what is now called the asteroid belt.

The discovery of these asteroids made the dream of finding the lost planet vanish: we assume that it is in pieces.

The belt is at a distance from the Sun between 300 and 525 million kilometers.

asteroid belt
This illustration shows our solar-system model: a Jupiter-size planet moves slightly inward but is just outside the asteroid belt. Credit: image and caption NASA/ESA, web “”.

Asteroids in this belt take between 3 and 6 years to go around the Sun.

But the belt is not a perfectly defined strip: many asteroids have orbits that take them to the inner regions of the Solar System, even closer to the Sun than the Earth is.

The asteroid Ceres

Since August 2006, Ceres has been classified as a dwarf planet like Pluto, Eris, Makemake and Haumea.

Smaller objects fall into the category of asteroids or “minor bodies in the solar system.”

An Unusual Mountain on Asteroid Ceres. Credit: NASA, JPL-Caltech, UCLA, MPS/DLR/IDA. Web “”

Today it is estimated that in the main belt alone, there are about two million asteroids that have a diameter of 1 km or more.

Trojan Asteroids

Asteroids In the image below, between Mars and Jupiter, the asteroid belt is clearly visible.

They are about 2,000,000 asteroids.

It can be seen that in the orbit of Jupiter there are a small number of asteroids that move on the orbit of this planet.

They are called “Trojan asteroids.”

ASteroids trojan
Trojan asteroids. Credit: web “”

The planet Mars also has a Trojan asteroid.

There are 5 known Neptune Trojan asteroids. It is called “centaur asteroids” to those found in the outer part of the Solar System orbiting between the great planets: Saturn and Uranus.

Trojans Initially, asteroids were given character names: Liberatrix, Eros, Zamenhoff, Mr. Spock, etc. Even names of cities or countries: Barcelona, ​​Uganda, China. Snoopy.

When their number increased, it became necessary to use more modern forms.

The modern notation of asteroids is the one used by the “Center for Minor Planets” which assigns them a key that indicates the year, month and order of discovery.

This denomination consists of a number, which is the year, and two letters: the first indicates the fortnight in which the sighting occurred and the second reflects the sequence within the fortnight.

Thus, 1989 BC indicates that it was discovered in 1989, in the first half of January (A) and that it was the third (C) discovered in that period.

When the orbit of an asteroid is established with sufficient precision to predict its future trajectory, it is assigned that key and, later, a permanent name chosen by the discoverer and approved by a committee of the International Astronomical Union.

The Center for Minor Planets that works at the Smithsonian Astrophysics Observatory, under the auspices of the International Astronomical Union.

Near Earth Asteroids

Asteroids several asteroids passed “close” to Earth.

One of them was about 560 meters in diameter and was traveling at more than 16,000 km per hour.

Osiris Rex
Artist’s depiction of OSIRIS-REx the spacecraft  searching for other Trojan asteroids near Earth. Credit: NASA. Web “”

Another of the potentially dangerous meteorites passed only 7,000,000 km.

Considering that the Moon is about 384,000 km away from Earth, it can be said that the asteroid passed at a distance of approximately 17 times the distance that separates the Earth from the Moon.

Anyway, this is considered too close. The European Space Agency keeps a constant watch on more than 700 asteroids that could be dangerous for us.

Potentially hazardous asteroids

Among the thousands and thousands asteroids there are those that are very dark (albedo less than 0.04) similar in this to meteorites, others that are very bright, others that are very red, perhaps due to the presence of materials with a large amount of carbon, others show signs of containing large amounts of silicon, nickel and iron.

Some asteroids have satellites or small moons around them.

This is the case of the asteroid Silvia, which has two satellites rotating around it: Romulus and Remus.

Romulus was discovered on February 18, 2001 with the Keck II telescope on Mauna Kea. It is 18 km in diameter and orbits 1,370 km from Silvia.

Rowing is 7 km in diameter and turns at a distance of 710 km from Silvia.

Artist rendering of the triple system : Romulus, Sylvia, and Remus. Credit: ESO, web “”.

Romulo Remo There are some asteroids that are especially worrisome due to their proximity to Earth and that, under certain conditions, it would be possible to impact our planet.

So serious is the threat that it was decided to catalog and track these potentially dangerous asteroids.

To them some comets have been added that, although lower in mass, would also cause very serious disorders if they hit the Earth.

There are about 4,000 objects of this type, cataloged as NEO (Near Earth Objects) and are subject to permanent monitoring by the International Spaceward Association.

In Spain there is a center dedicated almost exclusively to this topic that is located in the Astronomical Observatory of La Sagra, located in the middle of the mountain (at a height of 1,580 m) near Puebla de Don Fadrique, in the province of Granada.

Despite the budget shortage, it is believed that through ingenuity and work the different Spaceguard Surveys have cataloged at least half of the objects with a diameter greater than 1 km.

How to prevent dangerous asteroids

If a NEO approaches less than 7,500,000 kilometers from Earth, it is classified as potentially dangerous.

There are currently about 800 asteroids considered potentially dangerous.

The calculations of the trajectorias and each approach to the Earth of the asteroids have great uncertainties, because their orbital elements are not known with total precision.

Any prediction is subject to a considerable margin of error and precision observations are required continuously.

Hence the importance of large projects that coordinate systematic observations of the sky and the maintenance of updated databases.

For example, it was thought that the asteroid 1950 DA could impact Earth in the year 2880. However, better knowledge of its orbital elements has allowed observers to report that such an event will not occur.

There are asteroids that when approaching the Earth remain captured by the Earth’s gravity for a few years and then move away again. Two bodies of this type are currently known: the 2003 YN107 and the 2004 GU9.

On March 18, 2004, the asteroid 2004 FH, with a diameter of 30 meters, passed close to Earth and then moved away from it. At its closest point it was 43,000 km. Its orbit changed due to the effect of the Earth’s attraction.

The asteroid Apophis

There is an asteroid that has attracted the attention of the media: the asteroid Apophis.

As is the most worrying case for public opinion, on this website I dedicate a special page to inform about the Apophis. Click here or on the image to see this information.

Asteroid Apophis, scientists believe there is a 1 in 1,50,000 chance that asteroid Apophis will hit earth. Credit: Pixabay. Web: “”

A large asteroid will approach Earth in the year 2040. The space rock, called 2011 GA5, is 140 meters in diameter and may get too close to our planet´

Scientists believe that if it definitely poses a real risk, there will still be time to develop a mission that could divert you from our path

2011 GAS