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This interstellar asteroid accelerates



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By Steven Spence

@TheStevenSpence

First asteroid of its kind

In October 2017, Oumuamua became – or 1I / 2017 U1 – The first human-proven interstellar asteroid It also changed the way comets and asteroids are named: The technical names of the comets begin with the letter C, while asteroids carry the letter A. After Oumuamua's discovery, the International Astronomical Union led the Letter I to designate interstellar objects.

What do we know about Oumuamua?

Oumuamua, meaning " a distant ambassador who first arrived" in Hawaiian, was launched on 19 October 2017 by the Pan-STARRS1 Telescope University of Hawaii discovered. The telescope is part of a NASA-funded program to discover and track asteroids and comets near Earth orbit. At first, the scientists were not sure what the object was. It was first classified as a comet while details of its orbit and composition were still being worked out. Later, scientists decided to reclassify it as an asteroid because of the lack of visible comet activity. Scientists were also unable to measure cyanide gas emission, which is typically observed in the outgassing of comets formed in our solar system.

Oumuamua has a complex rotational movement. It spins about its axis approximately every seven hours and 20 minutes. The asteroid is also unusually shaped. Based on variations in the observed brightness and rotation of the asteroid, models indicate that the asteroid is approximately five times as long (~ 800 meters) as its diameter (~ 160 meters).

Oumuamua has a matte red color. Scientists believe that its surface was reddened by cosmic radiation as it moved through interstellar space. The object is dense and rocky or metallic, with little dust or ice discovered. In the telescopes no coma of dust and gas from Oumuamua is visible, as would be the case with a typical comet.

Interstellar origin of the asteroid

Oumuamua moves in an open hyperbolic path with an eccentricity of 1.2 3 through our solar system, which is why astronomers quickly identified it as an interstellar object. Orbital trajectory calculations indicate that the asteroid from the direction of Vega occurred in the constellation Lyra. It leaves the solar system on a trajectory that brings it into the large square of the constellation Pegasus.

Oumuamua moves too fast (~ 26 km / s) to be absorbed by the sun. In perihelion, his closest approach to the sun, Oumuamua moved 87.7 km / s. The asteroid moved so fast that in just 73 minutes, it would have covered the average distance from Earth to the Moon! By comparison, the Apollo flights to the Moon took about three days to get from Earth orbit to the Moon's orbit. New Horizons, the spaceship sent to Pluto, returned the distance in eight hours. For example, if we could travel to the moon at a typical speed of 130 km / h, it would take about 123 days nonstop to get there.

  This diagram shows the orbit of the interstellar object Oumuamua as it passes through the solar system. It shows the predicted path of & # 39; oumuamua and the new course taking into account the new measured speed of the object.
The orbit of the interstellar object Oumuamua as it passes through the solar system. It shows the predicted path of Oumuamua and the new course taking into account the new measured speed of the object. Credit: ESA

Oumuamua has accelerated

As stated in a paper recently published in Nature the author Marco Micheli of the European Space Agency the asteroid has not moved as expected. In fact, it passed the orbit of Jupiter earlier than predicted, indicating that it was accelerating along its trajectory. Oumuamua was about 100,000 km further than could be explained on purely gravitational interactions. That sounds like a huge distance, but at the speed of the asteroid, this difference is about 64 minutes earlier than Jupiter. At its average distance from the Sun, Jupiter is about 774 million km (~ 43 light minutes) away from the Sun. A gap of 100,000 km is only 0.01%, which does not sound like much, but is measurable. In space, small percentages in absolute numbers can quickly become large numbers.

Astronomers have spent weeks analyzing the discrepancy between Oumuamua's observed trajectory data and the predicted position. In their work published on June 27, 2018 in Nature Marco Micheli and his colleagues reported how they identified the reason for the acceleration of Oumuamua. After excluding effects of "solar radiation pressure, drag- and friction-like forces, interaction with solar wind for a highly magnetized object and geometric effects" due to the shape of the asteroid, they concluded that Oumuamua accelerated "outgassing" due to "comets". This means that Oumuamua vented gases much like a comet.

Asteroid leaves the solar system

Oumuamua passed the Jupiter Railway at the beginning of May 2018. It will cross the Saturn Railway in January 2019, Uranus in August 2020 and Neptune in June 2024. By the end of 2025, Oumuamua will reach the outer edge of the Kuiper belt and then the Heliopause boundary – the edge of the solar system – sometime in November 2038.

– Steven contributes to photography and general science at GotScience. He keeps his little garden free from ladybugs, lavender and sometimes soap. Steven is interested in astronomy, dinosaurs, birds of prey, and everything related to Calvin and Hobbes .

Selected Image: An artist image of Oumuamua, the first interstellar object discovered by our solar system. Credit: ESA / Hubble, NASA, ESO, M. Kornmesser

References

International Astronomical Union [IAU]. (2017, November 17). The IAU approved a new type of designation for interstellar objects [Press release].

Landau, E . (2018, June 27). Hunt down & # 39; Oumuamua. Jet Propulsion Laboratory News .

Micheli, M., Farnocchia, D., Meech, K.J., Buie, M.W., Hainaut, O.R., Prialnik, D .. , & Petropoulos, A. (2018). Non-gravitational acceleration in the trajectory of 1I / 2017 U1 (& # 39; oumuamua) . Nature, 559 223-226

National Aerospace Authority [NASA]. (2018, June 27). The first known interstellar object of our solar system is unexpectedly accelerated [Press release].

Orbital eccentricity . (n. d.) In Wikipedia .

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