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Aftermath of a huge planetary collision captured by telescope for the first time

An international consortium of astronomers reported the observation of two ice giant exoplanets engaging in a cataclysmic planetary collision around a star reminiscent of our Sun. This monumental event was marked by an intense blaze of light and subsequent emanation of enormous dust plumes.

Initial observation

The intrigue surrounding this star system began when an astrophysics enthusiast, while perusing the light curve of the star, discerned a peculiar pattern. The system’s brightness at infrared wavelengths exhibited a two-fold increase approximately three years prior to a noticeable dimming of the star in visible light.

Dr. Matthew Kenworthy, a co-lead author affiliated with Leiden University, recounted his astonishment at this unusual observation, admitting that the phenomenon was entirely unanticipated. The initial visible light curve data, when disseminated amongst the astronomical community, garnered the attention of other experts, prompting them to intensify the scrutiny of this star using a collective of telescopes.

The role of social media in this discovery is noteworthy. It was a post by another astronomer that highlighted the star’s increased brightness in the infrared, a phenomenon that occurred over a millennium before the observed optical fading.

Studying and naming the planetary collision

The focal star of this study was christened ASASSN-21qj, a nomenclature derived from the network of telescopes instrumental in its detection at visible wavelengths. Over the subsequent two years, the star underwent meticulous monitoring by both professional and amateur astronomers.

Their collective research led to a consensus on the most probable cause behind these observations. The infrared glow, which had been registered by NASA’s NEOWISE mission — a mission primarily oriented towards asteroid and comet detection using space telescopes — was deduced to originate from the collision of two ice giant exoplanets.

Dr. Simon Lock, another co-lead author from the University of Bristol’s Earth Sciences department, elucidated their hypothesis by referencing their computations and simulations. He explained that the characteristics and longevity of the observed glowing material were in line with what one would anticipate from an impact between two such celestial bodies.

What happens after a planetary collision

The aftermath of this planetary collision was discernible as an expansive debris cloud. As this cloud traversed in front of the star, it accounted for the dimming witnessed approximately three years post the infrared surge.

The ramifications of this collision are ongoing. Astronomers anticipate the debris cloud to eventually distribute along the orbit of the remnants of the collision. As this unfolds, light scattering from the cloud might become observable using both terrestrial telescopes and NASA’s preeminent space telescope, the JWST.

What happens next for the planets?

The astronomical community is rife with anticipation regarding the future trajectory of this system. Dr. Zoe Leinhardt, a co-author from the University of Bristol, speculated on the potential developments in the aftermath of this cosmic event. She foresees the possibility of the amassed material coalescing to engender a series of moons that will subsequently revolve around the emergent planet.

This event has provided the astronomical community with a rare and valuable opportunity to observe and understand the dynamics of exoplanet collisions. As the remnants of this colossal impact continue to evolve, astronomers globally will remain vigilant, hoping to glean further insights from this unprecedented phenomenon.

More about planetary collisions

As we learned above, planetary collisions, while sounding like the stuff of science fiction, play a crucial role in shaping our universe. These cataclysmic events have forged planets, birthed moons, and even dictated the fates of entire solar systems.

How planetary collisions occur

In the vastness of space, gravitational forces rule supreme. Planets, protoplanets, and other celestial bodies dance to this cosmic tug-of-war. Occasionally, these orbits intersect or become unstable, leading two bodies to collide. The size, speed, and angle of impact dictate the outcome of these collisions.

The birth of Earth’s moon

Our very own moon serves as a testament to these violent events. Most scientists believe that about 4.5 billion years ago, a Mars-sized body, often referred to as Theia, collided with a young Earth.

This impact threw a vast amount of debris into space, which eventually coalesced to form the Moon. This theory, known as the Giant Impact Hypothesis, explains why the Moon and Earth have similar isotopic compositions.

The creation and destruction of planets

Not all impacts result in creation; some lead to destruction. Early in our solar system’s history, rogue protoplanets likely roamed, sometimes smashing into one another. These collisions could shatter a protoplanet, disperse its materials, and prevent it from becoming a full-fledged planet.

Conversely, collisions can also build planets. Dust and rocks, through countless collisions, gradually stick together and grow. Over time, these merged bodies accumulate enough mass to clear their orbits of other debris, earning them the title of a planet.

Future planetary collisions

While massive collisions between mature planets in our solar system remain unlikely due to established and relatively stable orbits, other star systems, such as ASASSN-21qj discussed above, still experience such events. These impacts can change planetary atmospheres, influence orbits, or even form new celestial bodies.

Planetary collisions in the search for life

Collisions also play a role in our quest to find extraterrestrial life. The impact can strip a planet of its atmosphere or create conditions unsuitable for life. However, they can also deliver vital ingredients, like water, to otherwise barren worlds.

Planetary collisions, though violent and chaotic, are essential threads in the cosmic tapestry. They remind us of the dynamic nature of our universe, where creation and destruction often go hand in hand. As we continue our journey through the cosmos, understanding these events will undoubtedly shed light on our past and hint at our future.

The full study was published in the journal Nature.

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