This is a tribute to the film Don’t Look Up (2021) and a collaboration between Midnight Eclipse and Astrocenter. There will be spoilers in this post regarding the film’s plot.
Synopsis
Don’t Look Up follows the story of two astronomers who discover a new comet in the Solar system. However, they soon realize that the comet’s orbit is set to collide with Earth and race to warn the world of the impending danger. Although there has been no such catastrophic astronomical event for Earth(as of yet), there have recently been quite a few close encounters. One such example is 2022 FD1, an asteroid closest to Earth at 8500km at one point during its approach. This is less than half the distance of most US GPS satellites. Another example is the 2013 Chelyabinsk Meteor (an object entering Earth’s atmosphere), a small asteroid that exploded over a Russian city. We encourage you to further explore near-Earth objects on your own, as they’re both potential astrobiology discoveries as well as existential risks to humanity.
Comet composition
Comets are primarily composed of rock, dust, ice, and other gasses. These include carbon monoxide, CO2, ammonia, nitrogen, and methane. They’re often called “dirty snowballs” due to their composition.
Comet Structure
The comet structure is easily visible, with a head and tail, but it’s not as simple as that. The physical structure of the comet consists of a nucleus, a coma, an extended hydrogen halo, a type 1 tail, and a type 2 tail.
The nucleus, also known as the “core”, consists of ice and dust as previously mentioned. The vast majority of the comet core has a diameter of approximately 16 kilometers, and they generally get smaller in size as the comets fly closer to the sun.
A coma is a sphere-like gas that spans about 50,000 kilometers! The coma results from the gas and dust that sublimates from the high temperatures of the Sun.
Moving on from the coma, next is the extended hydrogen halo. The hydrogen halo is essentially the large glow that seems to surround the comet’s coma and nucleus. The glow is invisible to the naked eye, but can be observed through infrared telescopes and more. The halo can be about 10x bigger than the Sun. The hydrogen that makes up the glow is formed after the heat from the Sun breaks the bonds of water molecules within the comet nucleus. The split hydrogen then “explodes” into the haze that surrounds the comet.
Within the glow exists what we know as tails. There are two types of tails in many comets, known as ‘type 1’ and ‘type 2’ tails. Type 1 tails consist of the blue ion tails, and type 2 are the yellow dust tails. Due to solar ultraviolet radiation, the gasses of the nucleus tend to ionize, forming the blue tail from fluorescence. The dust tail is yellow due to the sunlight reflecting off it. The dust tail resembles a fan. Sometimes, comets have only a type 1 tail, only a type 2 tail, both tails, or no tails at all.
Comet Sources
Comets have two sources: The Kuiper Belt and the Oort Cloud. Comets with a shorter orbit period (about 200 years or less) tend to come from the Kuiper Belt, and the Oort Cloud supplies comets that have a significantly longer orbit period (200 years or more). The Kuiper Belt is the region just beyond Neptune. Pluto, perhaps the most well-known dwarf planet, is located within the Kuiper Belt. The Oort Cloud is located beyond the Kuiper Belt. An example of a comet that came from the Kuiper Belt is Halley’s Comet, and an example from the Oort Cloud is the comet Neowise.
Comet Orbit
Like planets and asteroids, comets also orbit the sun. However, their orbits don’t look like those of planets or asteroids – they’re highly elliptical. Just like all objects that orbit the sun, they follow Kepler’s laws. This means that the closer the comet is to the sun the faster it moves. The reason for their unique orbit isn’t a great mystery; it’s actually quite simple. Comets have an elliptical orbit due to gravity. Comets originate in the Kuiper Belt or the Oort Cloud, so when another star passes by the solar system its gravity pushes on the Kuiper Belt and the Oort Cloud. This causes the comets that originate there to have elliptical orbits.
Examples
As mentioned above, Halley’s comet is an example of a comet from the Kuiper Belt, and the comet Neowise is an example of a comet from the Oort Cloud. Halley’s comet is one of the most famous comets of all time. It is visible from Earth every 75 years, making it a short-period comet and very well known and popular. It was discovered by Edward Halley in 1758, but there is evidence to suggest that it was observed by ancient astronomers before him. The comet Neowise is a long-period comet meaning it has an orbit of 200 years or longer. In this case, the orbital period is 6,792 years! It was discovered on March 27, 2020, by astronomers on the NEOWISE mission.
Conclusion
So what does this all mean for the scientific accuracy of the film? Dibiasky and Mindy found a 10km diameter comet on a direct path towards Earth. Near-Earth objects themselves aren’t uncommon, as new comets and celestial objects are discovered and monitored all the time by NASA’s Center for NEO Studies and other researchers.
However, rarely are they of this size. The asteroid that caused the dinosaur extinction was slightly larger(10-15km), but the destructive capabilities of a crash are also dependent on the object’s speed at atmospheric entry. A comet of that size could very well cause climate change and mass extinction on Earth.
Additionally, the two astronomers’ efforts to warn humankind of the danger are countered by eccentric billionaire Peter Isherwell’s proposal to let the comet hit Earth as smaller pieces and mine them for precious minerals.
The possibility of a world-class billionaire dangerously exploiting natural resources for money aside, comets are mostly composed of ice and rock from the solar system as mentioned above. As such, the comet containing rare metals is not improbable. However, mining it wouldn’t be very efficient, as it would be chipped away during entry(as well as the small issue of many fragments striking inhabited areas).
Space mining may see better success focusing on relatively stationary asteroids in the Kuiper Belt or Oort Cloud. In reality, Elon Musk has expressed interest in expanding his business to include mining exotic minerals and metals found in asteroids, especially as Earth’s resources are gradually depleted.
As aeronautical technologies develop and the economy grows, space will be a new frontier of expansion and colonization for human civilization. We’d also have to be wary of the constant danger of comets and other celestial objects, as high-speed fragments can cause serious damage despite their size.
Thank you to Midnight Eclipse for making this post possible! Here is the link to their website, where they publish frequent blog posts on astronomy and space: (https://mid-night-eclipse.wixsite.com/astronomyblog/blog)
As always, I encourage you to check out the movies or books listed below for more exciting content about comets and asteroids. I'll see you in the next one!
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Bibliography
Hale, A. (2019, September 25). Comets Facts | Types, Composition, Size, Information, History & Definition. The Nine Planets. Retrieved June 22, 2022.
St. Andrews. (n.d.). Orbit of a Comet. University of St Andrews. Retrieved June 22, 2022.
Siegel, E., & Starts With a Bang. (n.d.). Ask Ethan: Why Don't Comets Orbit The Same Way Planets Do? YouTube. Retrieved June 22, 2022
Freudenrich, C. (2021, February 4). The Path of a Comet - How Comets Work | HowStuffWorks. Science | HowStuffWorks. Retrieved June 22, 2022
Halley, E. (n.d.). Halley's CometFacts - Facts Just for Parents, Teachers and Students. Facts Just for Kids. Retrieved June 22, 2022
Pultarova, T. (2022, March 28). A small asteroid's orbit is changed forever after super close Earth flyby. Space.com. Retrieved June 22, 2022
NASA. (2019, 12 19). In Depth | Comets – NASA Solar System Exploration. NASA Solar System Exploration. Retrieved June 22, 2022
Natural History Museum. (n.d.). How an asteroid ended the age of the dinosaurs. Natural History Museum. Retrieved June 22, 2022
Caltech. (n.d.). What is the size of a comet? | Cool Cosmos. Cool Cosmos. Retrieved June 22, 2022
Lang, K. R. (2010). NASA's Cosmos. NASA's Cosmos. Retrieved June 22, 2022
Other works about comets/asteroids:
Armageddon
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