Credits: NASA/ESA/STScI
‘Oumuamua. It came from outer space. Deep outer space. It was just the first.
‘Oumuamua (properly spelled with the leading ‘ – Hawaiian word) was the first confirmed interstellar object we humans have noticed, and what a delightful dozy it was. All kinds of anomalies – and if you remember my post from 2018 (Dyson or Dust) scientists love anomalies.
When the chunk of rock managed to be noticed, it was already saying Aloha the second time on its way out. But all eyes immediately turned to it once it had been spotted on October 19. 2017. The comet had been shooting through the system for a century (because astronomy distances – it moved really fast, but takes forever), but until it got close enough to the sun to reflect light, seeing it was like finding a needle in a haystack. Then scientists had to move fast before its small size got it lost in the dark again.
The last recording of it came from Hubble (still the best eyes in the sky) on January 2, 2018. ‘Oumuamua will be chugging through the Oort cloud through at least 2196, though because of it’s strange inclination, when it will leave that mass of material is unknown.
First, let’s talk about it’s shape. Long and thin, flipping end over end, like a forgotten missile from a forgotten war. (So many sci-fi ideas from this piece of space flotsam.) Most space debris ends up round overtime – like rocks rolled by a river – between striking other material and gravity, space is full of marbles ready to be knocked together on a god’s playground.
But not the needle-shaped interstellar visitor. How did it gain that shape? Why didn’t the heat of circling the sun take off more of the long edges?
Second, the trajectory through the elliptical plane. While doing its end-over-end tumble (which didn’t help with the imaging), it traveled retrograde to the paths of the planets at a 33 degree angle. Most comets, if they are going to survive any length of time in the system, are off the typical plane. Otherwise Jupiter and its little gas siblings would sweep the visitor from the sky in short order.
Most short orbit comets (regular visitors from the Kuiper Belt) are within 30 degrees of normal and travels along the same orbit as the planets, although there are retrograde exceptions like Halley’s Comet.
The odd trajectory provided proof that the rock Wasn’t From Around Here.
Third, reflection is weird. Astronomers have a bunch of filters, which give them a lot of information. They tried infrared imaging and the object didn’t show up, like at all. (Shielding anyone?) Actual reflection is 10% rather than 3% of most comets; whatever it’s made from isn’t from Around Here. Not typical space material.
Fourth, and here is a really fun fact. It picked up speed and changed trajectory as it flew away from the sun.
Comets don’t do this. They pick up speed falling toward the sun, allowing them to break free of the gravity and keep to their elliptical orbit. But to speed up while moving away from the monster gravity well? And change where it is going?
Are we sure this is not an alien probe?
Scientists, because aliens are ALWAYS the last option, speculate that the asteroid experienced outgassing vents on the side facing the sun but because of the small size and distance, our telescopes couldn’t pick it up. This combined with the tumble changed the trajectory.
Because, yeah, something with an odd-shape will lose its materials in a manner which won’t break it in half, apply speed increase while flipping end over end, and remain needle shape. Let’s go with invisible vents.
Scientists assure us this happens with other comets. The speed increase, at least. They have seen it before with some comets. All of whom eject large amounts of dust and gas when warmed by the Sun; basically an explosion on one side sends the comet careening away from the star. Problem was ‘Oumuamua didn’t do the dust-ejection thing at all.
Those studying the speed-increase and trajectory-change phenomenon have come with six possible explanations, and the comet outgassing seemed ‘most likely’. (Kiesman 2018)
I’ll go with bad programming on some alien’s part. They matched the speed, but maybe they don’t see in the same range as us and didn’t include the visible part where it was visible to us. Our scientists looked for three different types of gases, one easy and typical and two less easy. Nothing.
Fifth, where did it come from? Coryn Bailer-Jones of the Max Planck Institute for Astronomy in Heidelberg, Germany, backtracked the path to four possible candidates. Guess what? None of the answers match up to our present understanding of expelling materials during the planet-creation process. ‘Oumuamua is traveling too fast, like a factor of ten high. Another anomaly.
But, you know, if you are going to send out a space probe to nearby planets or stars, a good space agency would slingshot the probe around stars and planets to increase speed and change direction to get aim a probe at another place to investigate. Once into space, maybe the needle unfolds to send its gather data home on its way to the next system?
But, as with WTF? star mentioned in the “Dyson or Dust”, only one example does not a database make.
Did I mention ‘Oumuamua was the first?
Guess what happened in 2019?
An amateur astronomer named Gennady Borisov spotted another comet and bounced it through the international database to see what it could be. It didn’t match anything, so boy-o got it named after him – the Borisov comet. Continued observation came back with an interesting piece of data – the orbit wasn’t elliptical. Not by a longshot. Under one is required for comets to stay in-system – even an Oort cloud comet with a million year orbit, this baby had a three trajectory.
Another interstellar object, and this one over twice as big as ‘Oumuamua and spotted on the way in. Lots of time for observation. First spotted on August 30, Borisov wouldn’t do-si-do around the sun until December 8, 2019.
After the craziness of ‘Oumuamua, scientists were hot to have another interstellar object to observe.
Borisov reflects like normal, has a round shape, the material analysis possible at distant is coming back typical to a rock from Sol’s local real estate.
So now we have one rock that is exactly like what we expected and one which is nothing like we expected. Which is the anomaly for what’s out in the Big Black?
Did our alien observers get better with their camouflage?
Only time will tell. As we continue to upgrade our telescopes and raise our awareness of Near-Earth-Objects, Humanity will figure this out.
Me. I’m impatient. I want to know the answers now. But we aren’t in the Big Black yet, so we have to wait and watch patiently for the next rock to come to us. To wash ashore from the Endless into our Solar System.
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UPDATE – 6/28/2020
From the Planetary Society Downlink 6/5/2020
The first interstellar object ever detected passing through our solar system, ‘Oumuamua, may have been an iceberg made entirely out of hydrogen, scientists say in a paper submitted to The Astrophysical Journal. ‘Oumuamua mysteriously accelerated as it left the solar system, but not in a way that matched our understanding of comets venting dust and gas. Models show a hydrogen iceberg fits the data, meaning ‘Oumuamua could have formed in a dense cloud of hydrogen and helium where stars are born, known as a giant molecular cloud. A well-known example of such a cloud is the Horsehead Nebula in Orion. (The Planetary Society, Mission Briefings, third paragraph)
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So not aliens, maybe (article is out for peer review). On the other hand, one of the questions for space exploration has been how to get a hold of hydrogen while in deep space.
Bibliography
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Greshko, Michael. “Bizarre comet from another star system just spotted.” National Geographic. 2019 September 12. https://www.nationalgeographic.com/science/article/bizarre-interstellar-comet-from-another-star-system-just-spotted – Last viewed 12/6/2019.
Kiesman, Alison. “What do we know about ‘Oumuamua?” Astronomy. 2018 November 2018. https://astronomy.com/news/2018/11/what-do-we-know-about-oumuamua – Last viewed 12/6/2019.
NASA. “Our Solar System’s First Known Interstellar Object Gets Unexpected Speed Boost.” 2018 June 27. https://www.nasa.gov/press-release/our-solar-system-s-first-known-interstellar-object-gets-unexpected-speed-boost/ – Last viewed 12/6/2019.
NASA Jet Propulsion Laboratory California Institute of Technology. “First Interstellar Asteroid Wows Scientists.” 2017 November 20. https://www.jpl.nasa.gov/videos/first-interstellar-asteroid-wows-scientists – Video last viewed 12/6/2019.
Ottewell, Guy. “Oumuamua’s path in our solar system.” EarthSky. 2017 December 27. https://earthsky.org/space/oumuamuas-solar-system-trajectory-ottewell/ – last viewed 12/6/2019.
Planetary Society, The. “Committed to Doing the Work, Mission Briefings”. The Downlink. 2020 June 5. https://www.planetary.org/the-downlink/committed-to-doing-the-work.html – last viewed 6/28/2020.
Seligman, Darryl and Gregory Laughlin. “Evidence that 1I/2017 U1 (‘Oumuamua) was composed of molecular hydrogen ice”. 2020 May 28. https://arxiv.org/pdf/2005.12932.pdf – last viewed 6/28/2020.
Strobel, Nick. “Comet Orbits — Oort Cloud and Kuiper Belt.” Astronomynotes.com (personal website). Last updated 2019 May 26. https://www.astronomynotes.com/solfluf/s8.htm – last viewed 12/6/2019.
Very thought provoking. Thanks for sharing.