The Instituto de Astrofísica de Canarias (IAC) is one of the international researches centres which is following actively the asteroid 2024 YR4 which has been qualified by the United Nations (UN) as potentially dangerous, because it has a 1.5% probability of impacting the Earth during 2032.The asteroid was discovered in 2024 and has an estimated size of between 40 and 90 metres.
Given these figures, the UN has activated the protocols of planetary defence to obtain more accurate estimates of the orbit, the size and the threat which might be presented by 2024 YR4. The protocols of the UN are activated when the probability of impact is greater than 1%. In that case they activate the International Asteroid Warning Network (IAWN) presided over by NASA, and the Space Missions Planning Advisory Group (SMPAG) presided over by ESA.
The Instituto de Astrofísica de Canarias (IAC) is one of the centres of reference in this field, via its Solar System group, led by Dr. Julia de León, and Dr. Javier Licandro. The IAC participates by providing data, and in addition Dr. De León is the point of contact of ESA in Spain for NEOs (Near Earth Objects) and for Planetary Defence, which are the techniques of observation and action designed to prevent impacts of those objects on the Earth.
The IAC has been observing asteroid 2024 YR4 for several weeks from its observatories, which has permitted the acquisition of very accurate measurements of its position, and the improvement of the parameters of its orbit. In addition, even though it is so faint an object, Dr. Julia de León has been able to provide information about its composition, thanks to spectra obtained with the Gran Telescopio Canarias (GTC), the largest optical telescope in the world.
Javier Licandro explains that “It is important to obtain good knowledge of what type of asteroid it is, in terms of its composition, to get the most accurate estimate of its size:” He also reminds us that this is the second case when, after observing an object and calculating its orbit, it has been estimated that it could have a probability of more than 1% of impacting in the near future. “The first case was Apophis, which was discovered in 2004, and which when it was first observed was given a possible impact probability greater than 1%, but after tracking it and studying its orbit with higher precision, it could be shown that it would pass very close to the Earth in 2009, but that it would not make an impact. Apophis measures approximately 375 km across” explains Licandro, and adds that “in the present case the size is less, but as the probability is greater than 1%, they have initiated the tracking protocol which has been set up to study it as carefully as possible”.
Julia de León explains that with her observing programme on the GTC they have been able to show that the object is a rock made up of silicates and some metal “Knowing the composition we can infer the albedo (the fraction of light which its surface reflects) and knowing the albedo we can estimate its size” explains de León.
The IAC continues to track this object and is in contact with the other international institutions to contribute to a better determination of its size, its orbit, and the possibility of impact.
2024 YR4 was discovered by one of the telescopes of the ATLAS network, dedicated to the detection of asteroids on trajectories which could impact the Earth, of which the IAC is a part. The fifth ATLAS unit (ATLAS-Teide) has just been installed in the Teide Observatory and will soon start its scientific operations, which will put our observatories in the front line of the programmes of Planetary Defence.
