By NASA // November 17, 2018
In 2017, NASA's Spitzer Space Telescope discovered the object known as' Oumuamua
(NASA) – In November 2017, pointed scientists NASA's Spitzer Space Telescope Oumuamua – the first known interstellar object to visit our solar system. The infrared spitzer was one of the many telescopes pointed at umu Oumuamua in the weeks after its discovery that October.
Umu Oumuamua was too faint for Spitzer to detect when it looked more than two months after the closest approach to Earth in early September. However, the "non-detection" puts a new limit on how large the can object is.
The results of a recent study published today in the Astronomical Journal and co-authored by NASA's Jet Propulsion Laboratory in Pasadena, California.
This year, the new limit is consistent with the findings of this research paper, which suggested that the change was' slight changes in 'O' speed and direction were tracked last year: The authors of the paper conclude the expelled gas acted like a small thruster gently pushing the object.
That determination is dependent on you being relatively smaller than typical solar system comets. (The conclusion that umu Oumuam experienced outgassing suggested that it was composed of frozen gases, similar to a comet.)
"‘ Oumuamua has been full of surprises from day one, so we were eager to see what the Spitzer might show, "said David Trilling, lead author of the new study and a professor of astronomy at Northern Arizona University. "The fact that umu Oumuamua was too small for Spitzer."
'Oumuamua was first detected by the University of Hawaii's Pan-STARRS 1 telescope on Haleakala, Hawaii meaning "visitor from afar arriving first"), in October 2017 while the telescope was surveying for near-Earth asteroids .
Subsequent detailed observations conducted by multiple ground-based telescopes and NASA's Hubble Space Telescope detected sunlight reflected off Oumuamua's surface. Large variations in the brightness object are suggested that ‘Oumuamua is highly elongated and probably less than half a mile (2,600 feet, or 800 meters) in its longest dimension.
But the tracks of asteroids and comets using infrared energy, or heat, that they can provide more specific information about an object's size than optical observations of reflected sunlight alone would.
The fact that umu Oumuamua was too faint for Spitzer to detect sets of limits on the total surface area. However, since the non-detection can not be used to infer shapes, the size limits are presented as what umu Oumuamua's diameter would be if it were spherical.
Using three separate models that make different different assumptions about the object's composition, 'Oumuamua's Spitzer's non-detection limited "spherical diameter" to 1,440 feet (440 meters), 460 feet (140 meters) or perhaps as little as 320 feet (100 meters) . The wide range of results from the assumptions about "Ouuuuuu composition", which influences how visible (or faint) it would appear to Spitzer were it a particular size.
Small but Reflective
The new study also suggests that Oumuamua may be up to 10 times more reflective than the concept that resides in the solar system – a surprising result, according to the paper's authors.
Because infrared light is largely heat radiation produced by "warm" objects, it can be used to make a cold or asteroid; in turn, this can be used to reflectivity of the objects surface – what scientists call Albedo. Just as a dark T-shirt in sunlight heats up more quickly than a light one, an object with low reflectivity retains more heat than an object with high reflectivity. So a lower temperature means a higher albedo.
A comet albedo can change throughout its lifetime. When it comes to the sun, the comet 's ice warms and turns directly into the gas, the dust and dirt off the comet' s surface and revealing more reflective ice.
Umu Oumuamua has been traveling through interstellar space for millions of years, far from any star that could refresh its surface. But it may have had a refreshed through "outgassing" when it was made very close to the sun, a little more than five weeks before it was discovered. The dust of the dust and dirt, some of the gas has covered the surface of Oumuamua with a reflective coat of ice and snow-a phenomenon that also has been observed in comets in our solar system.
Umu Oumuamua is on its way out of our solar system – almost as far as the Sun as Saturn's orbit – and is well beyond the reach of any existing telescopes.
"Usually, if we get a measurement from a comet that's kind of weird, we go back and measure it again until we understand what we're seeing," said Davide Farnocchia, of the Center for Near Earth Object Studies (CNEOS) at JPL and a coauthor on both papers. "But this one is gone forever; we probably know as much about it as we're ever going to know. "
JPL manages the Spitzer Space Telescope mission for NASA's Science Mission Directorate in Washington. The Science and Technology Center at Caltech in Pasadena, California.
Spacecraft operations are based at Lockheed Martin Space Systems Company in Littleton, Colorado. Data are archived at the Infrared Science Archive housed at IPAC at Caltech. Caltech manages JPL for NASA.
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