James Webb Space Telescope will study asteroid 2024 YR4 – Rocket Science
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Asteroid 2024 YR4 was discovered on 27 December 2024. As of 10 February 2025, it has an approximately 98% chance of safely passing Earth on 22 December 2032. Astronomers are working to reduce our uncertainty about the asteroid’s orbit and rule out any impact risk, but it will fade from view from Earth in a few months’ time, and a small chance of impact may persist until it becomes visible again in 2028.
The chance of impact is very slim, and the asteroid is small enough that the effects of any potential impact would be on a local scale, but the situation is significant enough to warrant the attention of the global planetary defence community
What do we hope to learn by studying the asteroid with Webb?
Astronomers around the world are using powerful telescopes to measure the asteroid’s orbit as accurately as possible. But knowing its orbit will only tell us if the asteroid could impact Earth, not how significant an impact could be.
To accurately assess the hazard posed by asteroid 2024 YR4, we need a more precise estimate of its size. Our current estimate, 40—90 m, has not changed much since the asteroid was first discovered in December 2024, despite many follow-up observations.
This is because astronomers are currently limited to studying the asteroid via the visible light it reflects from the Sun. In general, the brighter the asteroid, the larger it is, but this relationship strongly depends on how reflective the asteroid’s surface is. 2024 YR4 could be 40 m across and very reflective, or 90 m across and not very reflective.
It is very important that we improve our size estimate for 2024 YR4: the hazard represented by a 40 m asteroid is very different from that of a 90 m asteroid.
Webb is able to study the infrared light (heat) that 2024 YR4 emits, rather than the visible light it reflects. Infrared observations can offer a much better estimate of an asteroid’s size, as explained in an article recently published in the journal Nature, co-authored by members of ESA’s Planetary Defence Office.
Astronomers will use Webb’s MIRI instrument to get a much more precise estimate of the asteroid’s size. This, in turn, will be used by ESA, NASA, and other organisations to more confidently assess the hazard and determine any necessary response.
Observations made using Webb’s NIRCam instrument will complement MIRI’s thermal data and will also provide additional measurements of the asteroid’s position once it is beyond the reach of Earth-based telescopes.
When will the observations of 2024 YR4 take place?
The first round of observations will take place in early March, just as the asteroid becomes observable by Webb and is at its brightest. The second round of observations will take place in May. Astronomers will use these later observations to study how the temperature of 2024 YR4 has changed as it has moved further away from the Sun and to provide the final measurements of the asteroid’s orbit until it returns into view in 2028.
Who requested the observations?
Each year, a small amount of Webb’s observational time is reserved for ‘Director’s Discretionary Time’. This time is set aside for time-critical or new discoveries made after the annual Webb proposal deadline that cannot wait for the next proposal cycle.
An international team of astronomers from institutions including ESA’s Planetary Defence Office submitted a proposal to use some of this time to study 2024 YR4. This proposal has now been accepted. The total observation time will amount to around four hours. The resulting data will be publicly available.
🔴#BREAKING: Scientists just ran a simulation of Asteroid Bennu slamming into Earth… and the results are terrifying!☄️ #asteroide
— OrbitalToday.com (@SpaceBiz1) February 10, 2025
🪨 👉Here’s what would happen if this 1,610-foot space rock actually hit us: https://t.co/tiroRMq5Sr pic.twitter.com/uR5WBP4XgA
Asteroid Bennu is a larger rock floating in space and according to experts has a 0.037% chance of colliding with Earth in the next 157 years. Some climate scientists in South Korea have created a stimulation of this asteroid hitting Earth to better understand the damage it could cause.
Possible Effects Of Asteroid Bennu Colliding with Earth
In a recently published document, Lan Dai and Axel Timmermann explain the results of their asteroid Bennu stimulation, hence highlighting the potential damage to Earth. Asteroid Bennu is about 500 meters in size, which is considerably small to much larger asteroids that are under observation.
Regardless of its size, this asteroid is capable of inflicting significant damage to the Earth. To better understand the effects of this collision, Lan and Axel used an Aleph supercomputer to stimulate the collision of a 500-meter asteroid on Earth.
From the document, we learn that a “potential collision of such medium-sized asteroids can inject massive amounts of dust into the atmosphere, with unknown consequences for terrestrial and marine ecosystems.” After the collision, about 400 million tons of dust escape into the Earth’s stratosphere; this leads to “disruptions in climate, atmospheric chemistry, and global photosynthesis.”
The simulation gives off a 4°C drop in the global mean temperature and a 15% drop in global precipitation. As for the productivity of both terrestrial and marine organisms, the stimulation gave a 36% and 25% decline respectively.
The effects of drastic temperature change will not only affect the condition of life but also the productivity of the soil, hence driving “massive disruptions in global food security.” So while the collision of this 500-meter asteroid might not be the end of Earth, its after-effects will bring serious changes to our home planet.
Some Hope For The Earth Following The Asteroid Bennu Collision
While the effects of this collision as shown by the stimulation are very scary, there is some hope for Earth. Following the collision of Asteroid Bennu on Earth in the stimulation, algae living in water bodies rapidly bounced back within months.
The rapid bounce back of algae after the collision is a result of the iron dust from the asteroid ejected after impact. With the abundance of algae, zooplankton will be able to thrive hence giving a glimpse of hope to other marine life.
As a result of this, the “reduction in terrestrial productivity” might be offset by the boost in marine productivity. Humans as well as other terrestrial life can then rely on the thriving marine life for sustenance following the asteroid collision.
Last Updated: 10th Feb 2025
There is a lot of talk about the increasing probability of the asteroid "2024 YR4" colliding with the Earth. This is quite natural, because even if it turns out that it will not collide in the end, the probability of collision will increase as the orbital precision improves. The purple horizontal line indicates the range of the asteroid's passage. © ︎ESA https://esa.int/ESA_Multimedia小惑星「2024 YR4」の地球衝突の確率が上がっていることが話題になっています。これはごく自然なことで、もし最終的に衝突しないことがわかっても、軌道精度が向上する過程で、衝突確率が上がってしまうからです。紫色の横線が通過する範囲を示しています。©︎ESA https://t.co/7hSn4eicEC pic.twitter.com/q4WIuJ8T7o
— 藤井大地 (@dfuji1) February 7, 2025
Here are 70 clones of #asteroid 2024 YR4 that do hit Earth, highlighting the impact risk corridor. There are some big cities along that line: #Bogota, #Lagos, #Mumbai. pic.twitter.com/FjgJ9gVsbB
— Tony Dunn (@tony873004) February 10, 2025
The probability of a collision with the Earth on December 22, 2032 is 2.4% (about double the probability at the time of discovery), and the Earth just before impact is seen from 2024 YR4, an asteroid with an estimated diameter of 54m. If it collides, it will enter the atmosphere at a speed of 17.3km per second, and will become a super fireball that will shine more than 100 times brighter than the Sun. [Caution] It has not been confirmed that it will collide with the Earth. It was discovered on December 25, 2024, and the observation period was short, so the accuracy of the orbit determination is low, so caution is required as the collision probability will change in the future. #planetarydefense #地球防衛 #Asteroid #火球2032年12月22日に地球に衝突する確率が2.4% (発見当時の約2倍に上昇)、推定直径54mの小惑星 2024 YR4から見た衝突直前の地球. 衝突した場合、大気圏突入速度は秒速 17.3kmとなり、太陽の100倍以上明るく輝くスーパー大火球になる. [注意] 地球衝突が確定した訳ではない.… pic.twitter.com/czSOn4nrAK
— 天文学者 阿部新助 Dr. Avell (@AvellSky) February 10, 2025
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