From Spitzer via Manu Garcia: “Umuamua intergalactic visitor”.

From Manu Garcia, a friend from IAC.

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From Spitzer

NASA learns more about the interstellar visitors’ Oumuamua.

An artistic concept of interstellar asteroid 1I / 2017 U1 ( ‘Oumuamua) while passing through the solar system after its discovery in October 2017. The observations of’ Oumuamua indicate that must be very long due to its dramatic brightness variations as fell space. Image Credit: European Southern Observatory / M. Kornmesser.

‘Oumuamua was too weak to detect when Spitzer looked more than two months after the closest to Earth the object approach in early September. However, the “no detection” put a new limit on the size of the foreign object. The results are reported in a new study published today in Astronomical Journal and coauthor of scientists at the Jet Propulsion Laboratory of NASA in Pasadena, California, The Astronomical Journal.

The new size limit is consistent with the findings of a research paper published earlier this year, suggesting that the degassing was responsible for slight changes in speed and direction of ‘Oumuamua as were screened last year: authors of this paper concluded that the expelled gas acted as a small pusher gently pushing the object. That determination depended on ‘Oumuamua is relatively smaller than typical comets in the solar system. (The conclusion that ‘Oumuamua experienced degassing suggested consisted of frozen gases, comet-like.)

‘Oumuamua has been full of surprises from the first day, so we were eager to see what Spitzer could show,” said David Trilling, senior author of the new study and a professor of astronomy at the University of Northern Arizona. “The fact that ‘Oumuamua was too small to detect what Spitzer is actually a very valuable result.”

‘Oumuamua was first detected by the Pan-STARRS 1 telescope at the University of Hawaii at Haleakala, Hawaii (the object name is a Hawaiian word meaning “visitor from afar come first”) in October 2017, while the telescope was looking for asteroids near Earth.

Pann-STARSR1 Telescope, U Hawaii, Mauna Kea, Hawaii, USA, Altitude 3,052 m (10,013 ft)

Subsequent detailed observations made by multiple ground-based telescopes and the Hubble Space Telescope detected NASA sunlight reflected on the surface of Oumuamua.

NASA/ESA Hubble Telescope

Large variations in the brightness of the object suggested that ‘Oumuamua is highly elongated and probably less than half a mile (2,600 feet or 800 meters) at its longest dimension.

But Spitzer tracks asteroids and comets using infrared energy, or heat, radiating, which can provide more specific information about the size of an object optical observations of sunlight reflected.

The fact that ‘Oumuamua was too weak to detect Spitzer sets a limit on the total surface area of ​​the object. However, since non-detection can not be used to infer the shape, size limits are presented as what the diameter if spherical Oumuamua. Using three separate models that slightly different assumptions about the composition of the object, the non-detection of Spitzer limited the “spherical diameter” of Oumuamua to 1,440 feet (440 meters), 460 feet (140 meters) or perhaps as little as 320 feet (100 meters) . The wide range of results stems from assumptions about the composition of ‘Oumuamua, which influences how visible (or weak) would seem to Spitzer if a particular size.

Scientists have concluded that the vents on the surface of ‘Oumuamua must have emitted gas jets, which gave the object a slight increase in speed, the researchers detected by measuring the position of the object as it passed through the earth in 2017. Credit: NASA / JPL -Caltech.

Small but thoughtful.

The new study also suggests that ‘Oumuamua can be up to 10 times more reflective than comets reside in our solar system, a surprising result, according to the authors of the article. Because infrared light is largely the heat radiation produced by the “hot” objects, can be used to determine the temperature of a comet or asteroid; in turn, this can be used to determine the reflectivity of the object surface, which scientists call albedo. Like a dark shirt to sunlight warms up faster than a light, an object with low reflectivity retains more heat than an object with high reflectivity. So a lower temperature means higher albedo.

The albedo of a comet can change throughout your life. When passing near the Sun, ice comet is heated and converted directly into a gas, sweeping dust and dirt from the surface of the comet and revealing more reflective ice.

‘Oumuamua has been traveling through interstellar space for millions of years, far from any star that could cool its surface. But it may have had its renewed surface through such “degassing” when he made an extremely close approach to the Sun, a little more than five weeks before it was discovered. In addition to sweep the dust and dirt of the released gas may have covered the surface of ‘Oumuamua with a reflective layer of ice and snow, a phenomenon also observed in comets of our solar system.

‘Oumuamua are leaving our solar system, almost as far from the Sun as the orbit of Saturn, and is far beyond the reach of existing telescopes.

“Usually, if we get a measure of a comet is something strange, we go back and measure again until we understand what we’re seeing,” said Davide Farnocchia, Study Center Near-Earth Object (CNEOS) at JPL . and co-author on both papers. “But this is gone forever, probably know as much as ever know.”

Links of interest:

The VLT reveals a dark red and very elongated object.
The first interstellar visitor Solar System dazzles scientists.
ESO’s VLT sees `Oumuamua gaining momentum.
Hubble sees’ Oumuamua is getting a boost, the new findings indicate that interstellar nomad is a comet.
Chasing ‘Oumuamua.
A new study shows what interstellar visitors’ Oumuamua can teach.

See the full article here .


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