A/2017 U1 - First known interstellar body

Traveling at high velocity along an extreme hyperbolic orbit and making a hairpin turn as it swung past the Sun, the now designated A/2017 U1 is the first known small body from interstellar space. A point of light centered in this 5 minute exposure recorded with the William Herschel Telescope in the Canary Islands on October 28, the interstellar visitor is asteroid-like with no signs of cometary activity. Faint background stars appear streaked because the massive 4.2 meter diameter telescope is tracking the rapidly moving A/2017 U1 in the field of view. Astronomer Rob Weryk (IfA) first recognized the moving object in nightly Pan-STARRS sky survey data on October 19. A/2017 is presently outbound, never to return to the Solar System, and already only visible from planet Earth in large optical telescopes. Though an interstellar origin has been established based on its orbit, it is still unknown how long the object could have drifted among the stars of the Milky Way. But its interstellar cruise speed would be about 26 kilometers per second. By comparison humanity's Voyager 1 spacecraft travels about 17 kilometers per second through interstellar space.

more credit from source: apod.nasa.gov/apod/ap171103.html

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read article / source: www.jpl.nasa.gov/news/news.php?feature=6983

Beautiful illustration and many more details on our guest-on-the-run:

'Oumuamua: Interstellar Asteroid

FULL IMAGE | Illustration Credit: European Southern Observatory, M. Kornmesser

article and more from source: apod.nasa.gov/apod/ap171122.html

article and caption from nasa-jpl: www.jpl.nasa.gov/news/news.php?release=2017-300

eso1737 — Science Release

ESO Observations Show First Interstellar Asteroid is Like Nothing Seen Before
VLT reveals dark, reddish and highly-elongated object

20 November 2017

For the first time ever astronomers have studied an asteroid that has entered the Solar System from interstellar space. Observations from ESO’s Very Large Telescope in Chile and other observatories around the world show that this unique object was traveling through space for millions of years before its chance encounter with our star system. It appears to be a dark, reddish, highly-elongated rocky or high-metal-content object. The new results appear in the journal Nature on 20 November 2017.

On 19 October 2017, the Pan-STARRS 1 telescope in Hawai`i picked up a faint point of light moving across the sky. It initially looked like a typical fast-moving small asteroid, but additional observations over the next couple of days allowed its orbit to be computed fairly accurately. The orbit calculations revealed beyond any doubt that this body did not originate from inside the Solar System, like all other asteroids or comets ever observed, but instead had come from interstellar space. Although originally classified as a comet, observations from ESO and elsewhere revealed no signs of cometary activity after it passed closest to the Sun in September 2017. The object was reclassified as an interstellar asteroid and named 1I/2017 U1 (`Oumuamua)

“We had to act quickly,” explains team member Olivier Hainaut from ESO in Garching, Germany. “`Oumuamua had already passed its closest point to the Sun and was heading back into interstellar space.”

ESO’s Very Large Telescope was immediately called into action to measure the object’s orbit, brightness and colour more accurately than smaller telescopes could achieve. Speed was vital as `Oumuamua was rapidly fading as it headed away from the Sun and past the Earth’s orbit, on its way out of the Solar System. There were more surprises to come.

Combining the images from the FORS instrument on the VLT using four different filters with those of other large telescopes, the team of astronomers led by Karen Meech (Institute for Astronomy, Hawai`i, USA) found that `Oumuamua varies dramatically in brightness by a factor of ten as it spins on its axis every 7.3 hours.

Karen Meech explains the significance: “This unusually large variation in brightness means that the object is highly elongated: about ten times as long as it is wide, with a complex, convoluted shape. We also found that it has a dark red colour, similar to objects in the outer Solar System, and confirmed that it is completely inert, without the faintest hint of dust around it.”

These properties suggest that `Oumuamua is dense, possibly rocky or with high metal content, lacks significant amounts of water or ice, and that its surface is now dark and reddened due to the effects of irradiation from cosmic rays over millions of years. It is estimated to be at least 400 metres long.

Preliminary orbital calculations suggested that the object had come from the approximate direction of the bright star Vega, in the northern constellation of Lyra. However, even travelling at a breakneck speed of about 95 000 kilometres/hour, it took so long for the interstellar object to make the journey to our Solar System that Vega was not near that position when the asteroid was there about 300 000 years ago. `Oumuamua may well have been wandering through the Milky Way, unattached to any star system, for hundreds of millions of years before its chance encounter with the Solar System.

Astronomers estimate that an interstellar asteroid similar to `Oumuamua passes through the inner Solar System about once per year, but they are faint and hard to spot so have been missed until now. It is only recently that survey telescopes, such as Pan-STARRS, are powerful enough to have a chance to discover them.

“We are continuing to observe this unique object,” concludes Olivier Hainaut, “and we hope to more accurately pin down where it came from and where it is going next on its tour of the galaxy. And now that we have found the first interstellar rock, we are getting ready for the next ones!”
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source / credit / contacts / more: www.eso.org/public/news/eso1737

Nov 23, 2017 2:29:04 GMT ET_Explorer said:

It reminds me of that alien probe on star trek iv

yep, or as said in nasa-apod article it's shape evokes Rama's from the novel by Arthur C. Clarke.

was already been misterious as came from interstellar regions, but that shape and details has totally roasted my integrated circuits...(:

Oddity level is rising:

...The observable interstellar object population is expected to be dominated by comet-like bodies in agreement with our spectra, yet the reported inactivity of 'Oumuamua implies a lack of surface ice. Here, we report spectroscopic characterization of ‘Oumuamua, finding it to be variable with time but similar to organically rich surfaces found in the outer Solar System. We show that this is consistent with predictions of an insulating mantle produced by long-term cosmic ray exposure. An internal icy composition cannot therefore be ruled out by the lack of activity, even though ‘Oumuamua passed within 0.25 au of the Sun.

source: www.nature.com/articles/s41550-017-0361-4

...Comet in Disguise

...studies suggest that the ice from the surface layers of such bodies evaporates because of the cosmic environment.

"What gets left transforms itself into a relatively rigid and desiccated surface held together by carbon compounds, which at the same time gives a sort of a reddish, pinkish color, and that's what we saw in our spectra."
/Alan Fitzsimmons, Queen's University, Belfast, Northern Ireland/

The astronomers ran a series of computer experiments to model the behavior of the now icy 'Oumuamua. They found that if the object's crust was only 20 inches (50 centimeters) thick, it would protect the ice at the object's core from the heat of the sun, thus preventing it from displaying the telltale signs of gas and dust leaving a comet.

"We've discovered that this is a planetesimal with a well-baked crust..."
/Michele Bannister, Queen's University, Belfast, Northern Ireland/

source: www.space.com/39129-oumuamua-interstellar-object-comet-in-disguise.html

Post title question for UFO hunters, me too only dare to accept gas hypothesis.

The Unexpected Trajectory of Interstellar Asteroid 'Oumuamua

Why is 'Oumuamua differing from its expected trajectory? Last year, 1I/2017 U1 'Oumuamua became the first known asteroid from interstellar space to pass through our Solar System. Just over a year ago, this tumbling interstellar rock even passed rather close to the Earth. The asteroid's future path should have been easy to predict given standard gravity -- but 'Oumuamua's path has proven to be slightly different. In the featured animation, 'Oumuamua is shown approaching and exiting the vicinity of our Sun, with the expected gravitational and observed trajectories labelled. The leading natural hypothesis for this unexpected deviation is internal gas jets becoming active on the Sun-warmed asteroid -- but speculation and further computer simulations are ongoing. 'Oumuamua will never return, but modern sky monitors are expected to find and track similar interstellar asteroids within the next few years.

more from source: apod.nasa.gov/apod/ap181120.html

...
Man! This is so exciting! 

If we consider an artificial origin, then there is a possibility that it is a light sail driving in the interstellar space as remnants of an advanced technological device.

Oumuamua (1I/2017 U1) is the first object of interstellar origin observed in the Solar System. Recently, \citet{Micheli2018} reported that `Oumuamua showed deviations from a Keplerian orbit at a high statistical significance. The observed trajectory is best explained by an excess radial acceleration Δa∝r−2, where r is the distance of `Oumuamua from the Sun. Such an acceleration is naturally expected for comets, driven by the evaporating material. However, recent observational and theoretical studies imply that `Oumuamua is not an active comet. We explore the possibility that the excess acceleration results from Solar radiation pressure. The required mass-to-area ratio is (m/A)≈0.1 g cm−2. For a thin sheet this requires a thickness of ≈0.3−0.9 mm. We find that although extremely thin, such an object would survive an interstellar travel over Galactic distances of ∼5 kpc, withstanding collisions with gas and dust-grains as well as stresses from rotation and tidal forces. We discuss the possible origins of such an object. Our general results apply to any light probes designed for interstellar travel.

Source: Link

The story of 'Oumuamua, the first visitor from another star system | Karen J. Meech