The Solar System research group at the Instituto de Astrofísica de Canarias (IAC) is participating in the international programme to keep a closet track of asteroid 2024 YR4. The aim is to determine its orbit with the highest possible precision before it stops being observable by ground based and satellite telescopes in April, and so improving our value of the probability that it will impact the Earth in 2032.
In this context several telescopes of the Canary Observatories of the IAC are playing an outstanding role in this observing campaign:
The Gran Telescopio Canarias (GTC) at the Roque de los Muchachos Observatory (ORM) with its 10.4 metre primary mirror has obtained the only spectrum of the asteroid up to now, which has permitted the determination of its composition and size. Thanks to the data from the GTC the initial estimate of the diameter of the object, which had been found to be between 40 and 100 metres, was improved, giving a reduced range of between 40 and 60 metres. This work, let by IAC researcher Julia de León Cruz shows that it is a rocky asteroid, made up mainly of iron silicate and magnesium silicate.
The position in the sky of the object has also been measured, contributing to improve its known orbit. The IAC team will continue this tracking in the coming weeks, with programmed observations by the GTC. Julia also is a member of the team which will use the James Webb Space Telescope to study 2024 YR4 during March and May this year, allowing greater precision in determination of its size and composition, as well as in the determination of its orbital parameters.
There have also been observations with the Nordic Optical Telescope (2.5 metres) on the Roque de los Muchachos, taken on recent nights, by a team led by researcher Marco Michelli from the European Space Agency (ESA).These data have permitted a further improvement in the parameters of the orbit of the asteroid. Thanks to precise measurements with the 8 metre Very Large Telescope (ESO;Chile), the probability of impact, which had risen to 3%, has been reduced to a value of 1,5%, on 20th February.
The 1 metre Transient Survey Telescope (TST) at the Teide observatory was used to measure positions of the object in January, and at the present time Miquel Serra Ricart and Miguel Rodríguez Alarcón are using the new 2 metre Two-meter Twin Telescope (TTT) to try to obtain new position measurements.
As Julia de León explains, "the initial increase in the impact probability is to be expected, since the improved orbit determination narrows the determination of the region through which the asteroid may pass on 22 December 2032 when it crosses the Earth's orbit. Thus, as long as the Earth remains within that region, the value provided by the probability calculation will become larger. Most likely, once the orbit is calculated with sufficient accuracy and the region becomes smaller and smaller, the Earth will be outside the orbit and the probability of impact will become 0%."
Julia explains further that “we have to wait to obtain more data. If this happnes before May, when the asteroid will no longer be visible, we may be able to exclude any risk. If this is not possible we will have to wait until 2028, when the asteroid will be visible again, and we can take more data. In the hypothetical case that those data increase the probability of an impact significantly we will have to start thinking of a mission to try to change the orbit of the asteroid as was carried out in the DART mission, which impacted Dimorphos, the satellite of asteroid Didymos, successfully modifying its orbit."
