Interstellar object discovered in the solar system oumuamua

Exciting Visit of Interstellar Object Oumuamua Will Make You Feel Eerie

This artist’s impression shows the first interstellar asteroid: `Oumuamua'.
This artist’s impression shows the first interstellar asteroid: `Oumuamua’.
European Southern Observatory/M. Kornmesser/Source/Creative Commons Attribution-Share Alike 4.0 International.

The First Interstellar Object Discovered in the Solar System

Isn’t it fascinating to think that an interstellar object traveling for millions and billions of years in Space can visit us one day? That’s exactly what happened on 19 October 2017.

Oumuamua is the first interstellar object to be discovered in the Solar System. It was a totally fascinating discovery unlike anything in the Solar System before. Research suggests that it was moving alone in the vast Milky Way galaxy for millions of years without orbiting any star until luck had it come into our Solar System.

A direct proof for an Interstellar Visit

Astronomers had expected such interstellar visitors, now there’s direct proof they exist. Research suggests it came from the direction of Star Vega in the constellation Lyra. But when Oumuamua was there 3 lakh years ago, the star Vega was not in that position in the sky.

Astronomers estimate that interstellar visitors like this come into the inner Solar System once per year, but they are too faint to be discovered, but recent telescopes are too powerful enough to discover them. It looks like a cigar – a Cosmic cigar about 400m long! It is slightly reddish in color due to irradiation from cosmic rays for millions of years. It was also thought to be an alien spaceship! But later analysis by astronomers reported it was a natural object.

This animation shows the trajectory of interstellar object Oumuamua as it passed through the inner Solar System in September/ October 2017.
This animation shows the trajectory of Oumuamua as it passed through the inner Solar System in September/ October 2017.
NASA. Source.

Dimensions and Properties of Oumuamua

Oumuamua was estimated to be between 100m to 1km long. Its width and thickness are estimated to range between 35m and 167m. Oumuamua doesn’t rotate on its principal axis, rather tumbles. Its rotation period is reported to be above 8 hours. There is a debate on the shape and structure of the Oumuamua asteroid.

Various research on Oumuamua is undertaken using the light curve measurements. It lacks the coma, usually present in a comet. There are also studies saying that Oumuamua has lost a lot of mass since it entered and left the solar system. There is a debate on whether Oumuamua is composed of Nitrogen ice or Hydrogen ice.

Naming the first Interstellar Object Discovered

Before the official name was given to this object, the name Rama was suggested which is the name of the alien spacecraft discovered under similar circumstances in the 1973 science fiction novel Rendevous with Rama by the writer Arthur C. Clarke.

It was discovered on 19 October 2017 by the Pan-STARRS1 telescope in Hawaii as a part of NASA’s Near-Earth Object Observations (NEOO) Program. As soon as it was discovered, powerful telescopes all around the world, such as ESO’s Very Large Telescope in Chile were turned to see this interstellar visitor. It was named ‘Oumuamua’, a Hawaiian name, by its discoverers which means “a messenger from afar arriving first”.

Is this Interstellar object a comet?

It was initially thought to be a comet, but it showed no signs of cometary activity as it neared the Sun. It was also thought to be an asteroid. But when the astronomers found that it was accelerating slightly, it was found to behave more like a comet.

ʻOumuamua’s eccentricity is so high that it could not have been caused by an encounter with any of the planets in the Solar System. Even if there are undiscovered planets in the Solar System they cannot match the Oumuamua’s trajectory or its speed. Hence Oumuamua was confirmed to be of interstellar origin. 

Where did this Interstellar object originate from?

There is the various hypothesis put forward regarding the origin of this interstellar visitor. It was found to be absolutely inert with no dust around it. The analysis points out that this interstellar visitor may be made up of rock/ metals but not water/ice. It has 10x length as its width, this aspect ratio is bigger than any asteroid or comet discovered so far!

Its brightness also varies by a factor of 10!! No asteroid or comet discovered so far has such a change in its brightness. It spins on its axis once in 7.3 hours. It flew past the Sun on 9 September 2017 at a speed of 87.3 km/s!! Its trajectory was found to be highly hyperbolic. It flew past Mars’s and Jupiter’s orbit in November 2017 and May 2018 respectively.

Space Missions Planned to Study Oumuamua

Several spacecraft missions were also considered to study Oumuamua in the timeframe of 5 to 25 years. Our only known interstellar visitor has left our Solar System and is traveling in the direction of the constellation Pegasus. Initiative for Interstellar Studies (i4is) started Project Lyra to check the feasibility of a mission to Oumuamua. Many more studies were done to check if a mission to Oumuamua on its way out of the Solar System is possible.

Various radical kinds of spacecraft propulsion were also considered including solar sail, laser electric and laser propulsion techniques for spacecrafts.

What was the most surprising thing for you about this Interstellar object? Comment below.


1. In Depth │Oumuamua – NASA Solar System Exploration. (2019, December 19). Retrieved from

2. Wright, Jason T.; Jones, Hugh R.A. (2018). “On Distinguishing Interstellar Objects Like ʻOumuamua From Products of Solar System Scattering”. Research Notes of the AAS1 (1): 38. arXiv:1712.06044Bibcode:2017RNAAS…1a..38Wdoi:10.3847/2515-5172/aa9f23S2CID119467366.

3. de la Fuente Marcos, Carlos; de la Fuente Marcos, Raúl; Aarseth, Sverre J. (2018). “Where the Solar system meets the solar neighbourhood: patterns in the distribution of radiants of observed hyperbolic minor bodies”. Monthly Notices of the Royal Astronomical Society Letters476 (1): L1–L5. arXiv:1802.00778Bibcode:2018MNRAS.476L…1Ddoi:10.1093/mnrasl/sly019S2CID 119405023.

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