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----------------------------- 2209 - Oumuamua - Asteroid from another solar system
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- We learn a lot about the Universe when we get a chance to observe other bodies interacting with its laws. We think the Earth is flat until we see the sailing ship sink over the horizon. We learn other lessons when cosmic interlopers come by our solar system and act differently than other orbiting bodies.
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- We are fortunate to observe an interloper asteroid that has entered our solar system coming from another solar system in our home Milky Way galaxy. This strange object I will call an asteroid is named Oumuamua that came to us from a solar system.
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- On October 19, 2017 astronomers in Hawaii discovered this interloper asteroid . When first discovered it was moving westward in the sky at 6.2 degrees of arc per day.
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- Tracking this orbit astronomers soon realized Oumuamua could not have originated in our solar system. After this interloper swung around our Sun it would again escape our solar system and never return.
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- Oumuamua’s Hawaiian for ”scout” because someone else may be spying on us??? Ok this is probably not an alien spaceship?
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- After tracking this interloper for over a year astronomers can begin to characterize it. Its brightness was measured precisely to determine which could represent either its reflectivity or its distance away from us. Making an estimate that its reflectivity to be 4% similar to other comets, we could calculate it distance.
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- Its brightness varied by a factor of 10 over several hours. With this data astronomers could conclude that it was an elongated object about 2,600 feet by 260 feet and perhaps cigar shaped.
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- The rotation was complex, not simply periodic. It must have been tumbling around more than one axis of rotation. This is not at all what you would typically see with comets.
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- Spectrometry measurements were made to identify the chemistry content of this interloper. Each chemical element has a fingerprint of light that it reflects or emits The conclusion was that its chemistry was markedly different than any other comet that had ever been measured. Another clue that it came to us from a different solar system outside our own.
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- A planetary system in a different solar system could naturally form distinctly different chemical composition from our own.
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- Is the cigar-shaped interstellar object ‘Oumuamua a comet or an asteroid? In the latest installment of this ongoing debate, the mysterious object is far too rotationally stable to have comet-like ejections of gas. This conclusion is at odds with a previous study of ‘Oumuamua, which suggested that the trajectory of the object is being affected by out gassing. Whether ‘Oumuamua is a comet or an asteroid could have important implications for understanding where the object came from.
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- In October 2017 the Hawaii-based Pan-STARRS survey telescope spotted a highly elongated, 2600 foot long object that astronomers soon realized had originated from outside the solar system.
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- Named after the Hawaiian word for “scout” to commemorate its interstellar voyage, ‘Oumuamua has both a highly eccentric orbit and a shiny surface, leading some astronomers to identify the object as a comet. However, the lack of a coma of gas and dust around ‘Oumuamua suggested to others that it is an asteroid.
- Oumuamua’s trajectory through the solar system cannot be explained by gravitational forces alone. Rather the object is being accelerated by the propulsive effect of gas being released as the object is heated by the Sun.
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- Such outgasing is a hallmark of a comet. If Oumuamua is ejecting gas like a comet, the resulting torques on its cigar like form would cause its rate of rotation to accelerate rapidly. In just a few days rotational forces would tear the object apart. In contrast, the data show that Oumuamua’s rotation is stable over timescales of many months. This suggests that gas is not being ejected.
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- When combined with the lack of an observed coma around Oumuamua, it should not be classified as a comet. This could have important implications regarding the origins of the object.
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- Unlike asteroids, comets in the solar system have highly eccentric orbits making it much more likely that a comet could be ejected into interstellar space. Asteroids, on the other hand, tend to have tighter and more circular orbits.
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- Therefore, if Oumuamua came from an extra solar planetary system like our solar system, it is much more likely to have begun its journey as a comet. The ejection of an asteroid from an extra solar system is much less likely and could involve a violent event such as the explosion of a star.
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- December 14, 2018
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-------------------------- Friday, December 14, 2018 --------------------------
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