Asteroid 2024 YRâ‚„: James Webb space telescope to determine the danger
In eight years' time, an asteroid dozens of meters in size could hit the Earth. One of our best instruments is now to determine how big it actually is.
(Image: Adriana Manrique Gutierrez, NASA Animator)
The James Webb Space Telescope will study the near-Earth asteroid 2024 YR4 to gain clarity about its size and orbit. The aim is not only to determine whether it could hit the Earth in eight years' time, but also how dangerous this would actually be. This has now been announced by the European Space Agency ESA. For days now, such an impact cannot be ruled out, despite 375 observations. At the same time, it is still unclear how large the celestial body really is. Estimates still range from 40 to 90 meters in diameter, which would have very different consequences in the event of an impact.
Impact still extremely unlikely
As the ESA summarizes, the calculated impact probability of the asteroid is still around 2 percent. This means that it will miss the Earth with 98 percent certainty. At the same time, an impact would only cause damage locally or at most regionally, depending on how large it is. Nevertheless, the situation is so serious that it requires the attention of those who deal with planetary defense. However, these people have to make do with limited data because the size of the asteroid can only be roughly determined with observations from the Earth's surface. For example, the asteroid could be smaller if it reflects a lot of light, or it could be larger and comparatively dark.
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The James Webb Space Telescope can examine 2024 YR4 in the infrared spectrum, i.e., to determine its thermal radiation. This enables a much more precise size measurement. To this end, the space telescope will focus on the asteroid for the first time at the beginning of March and then again in May. This will not only make changes in thermal radiation visible. Those responsible are also planning a final measurement of the exact orbit. After that, the asteroid will not be observable for several years. The analyses with the space telescope will take place within the framework of observation time reserved for time-critical campaigns.
Risk greater than it has been for a long time
2024 YR4 was discovered on December 27 using a telescope in Chile. Follow-up observations then revealed that an impact of the asteroid cannot be ruled out when it encounters the Earth on December 22, 2032. This is why the asteroid has been at the top of ESA and NASA's lists of the most dangerous celestial bodies for days. Before the weekend, the calculated risk had risen to up to 2.3 percent, but is now slightly lower again. It is still most likely that the danger can soon be completely ruled out. This has always been the case with similar objects.
On the so-called Turin Scale for classifying the danger posed by asteroids, 2024 YR4 remains at class 3. This means that it is not only currently considered the most dangerous, but only one asteroid has reached a higher class in the past: (99942) Apophis reached class 4 shortly after its discovery at the end of 2004, but is now no longer considered dangerous. No other asteroid has reached class 3 until 2024 YR4. This also means that the asteroid is not only of interest to astronomers, but also deserves attention from the public and official bodies.
Because of the potential risk posed by 2024 YR4, two organizations recognized by the United Nations have already begun their work. In addition to the International Asteroid Warning Network (IAWN) coordinated by NASA, this is the Space Mission Planning Advisory Group (SPMAG) at ESA. This group discussed the celestial body at a meeting and decided that it should continue to be observed and investigated. Possible countermeasures are already being discussed, but it is still too early for concrete proposals. If an impact in 2032 cannot be completely ruled out even at the beginning of May, this assessment will be reviewed.
(mho)
