On the 19th of October 2017, an object was observed accelerating rapidly away from our Sun. The discovery was made by PAN-STARRS (panoramic survey telescope and rapid response system). These are a group of telescopes that constantly observe the sky for variable and accelerating objects like asteroids or comets.
Initially the messenger was thought to be a new asteroid or comet but after a month of observation it became clear that this object was from outside our solar system. Comets and asteroids that are involved in the orbital mechanics of our Sun take clear and predictable paths through our local space time. This object was certainly an oddball and has caused quite a cosmic conversation.
This is the first object from another solar system that has come to visit. It has been called 1I, 1 being first and I meaning interstellar. The first interstellar object to come to visit us. Another name given has been Oumuamua from the Hawaiian meaning “arriving quickly from afar”.
So what does it look like? It has a very irregular elongated shape. Some estimates say 400m long and 40m in height and diameter. Definitely unlike most objects observed. Most of the worlds great telescopes had a chance to look at it but it looks like a faint dot. It’s actual shape and size are quite difficult to determine and many artistic impressions have swamped social media newsfeeds.
Oumuamua doesn’t have a tail and a lack thereof shows it has a rocky surface like an asteroid as opposed to a comet. It’s tumbling movement observed by astronomers points to a collision at some point in its life, there isn’t any friction in outer space to slow it down. In the same way there is no friction to slow the American flag on the moon after it was screwed into the surface.
All objects in our solar system have an elliptical orbit – Keplars Laws. Earth does, the planets do and visiting comets and asteroids from the outer solar system do. Although our visitor doesn’t! Our Earth elliptical value is 0.0167 giving us a nearly circular orbit. Elliptical eccentricity value of zero gives a perfect circle. Haley’s Comet has a value of 0.967, it comes from afar, gets very close to the sun and accelerates away again to return decades later.
Oumuamua has an eccentricity of 1.2! So it won’t orbit the sun as opposed to being deflected back out of the solar system again due to the Suns gravity. Oumuamua is travelling so fast that it can escape the pull of the sun. It’s highest velocity was recorded as 87km per second on approach to the Sun.
So where did our visitor come from? There are already hypotheses of its origin. One being that it originated in either our Kuiper Belt or Oort Cloud. Given it’s speed, it’s possible it received a cosmic kick from a huge object on the way in toward us. Computer simulations have shown it could have originated in another star system and was ejected at high speed. Or even formed in the Oort Cloud of another solar system.
Another guess is that it has been travelling for a soul crushingly long time. In planet formation, matter can be ejected from the protoplanetary disk under the violent conditions needed to fuse matter together to form a planet. The early Universe was full of protoplanetary disks when planets were forming around their host stars. It has been theorised in the past that fields of debris can exist around galaxies and our Sun is now at a stage it is approaching such a debris field in its own orbit around the centre of the galaxy.
So what now? Oumuamua is now leaving our solar system and should leave in around 20,000 years. In a few weeks, it will be invisible to our telescopes. With newer telescopes we may be able to detect more of these objects. We were lucky to detect this one and could have had other visitors and not noticed. Failing all of these logical explanations it could be aliens.