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Forum:Free Space
Topic:A/2017 U1: Interstellar visitor to solar system
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SpaceAholicOne could imagine an interstellar probe on an energy efficient gravity assisted trajectory making a flyby much analogous to our interplanetary flyby missions. On such a large scale (both in terms of velocity and proximity,) 15 million miles is very close.
BlackarrowCould it be Rama?
denali414HA! Or the monolith...
moorouge...or just a very naughty piece of rock.
BlackarrowIt's interesting that this interstellar rock has almost doubled its velocity by stealing a little energy from our Solar System.
SolarplexusThe Initiative for Interstellar Studies (i4is) is happy to announce a new project: Project Lyra, a mission to A/2017 U1, the interstellar asteroid.

Lyra is the star constellation from which the interstellar asteroid A/2017 U1 came from. According to current information, the object is smaller than 400m in diameter and is currently traveling at 44km/s with respect to the sun, much faster than any human-made object to date.

What can be more exciting than chasing this object with a spacecraft and making observations from a close distance? What secrets are hidden on this visitor from our galaxy? The velocity of the object makes it challenging to reach but this challenge might lead to new, innovative mission concepts.

SpaceAholicTechnology proposed for application in conjunction with Breakthrough Starshot is probably the only currently viable means to overtake and collect data against A/2017U1. Ion propulsion might eventually get there but we would be waiting a heck of a long time.
Robert PearlmanEuropean Southern Observatory (ESO)
ESO Observations Show First Interstellar Asteroid is Like Nothing Seen Before

VLT reveals dark, reddish and highly-elongated object

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 (ʻOumuamua).

"We had to act quickly," explains team member Olivier Hainaut from ESO in Garching, Germany. "ʻOumuamua 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 ʻOumuamua 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 ʻOumuamua 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 ʻOumuamua 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. ʻOumuamua 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 ʻOumuamua 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!"

Robert PearlmanInternational Astronomical Union (IAU) release
New Designation Scheme for Interstellar Objects

The discovery of A/2017 U1 has presented a slight nomenclature problem. Since both the original and future barycentric orbits for this object are significantly hyperbolic, this object is not bound to our solar system and the current apparition is likely to be the only time that the object is observable.

Due to the unique nature of this object, there is pressure to assign a name. The minor-planet designation scheme does not allow a name to be assigned to this object based on the brief arc of observation.

Recent e-mail exchanges between the IAU General Secretary, the IAU Division F President, the co-chairs of the IAU Working Group on Small Body Nomenclature and the Minor Planet Center have discussed this nomenclature issue. A solution has been proposed that solves the problem. A new series of small-body designations for interstellar objects will be introduced: the I numbers. This new sequence will be similar in form to the comet numbering system and assignment of the numbers will be handled by the Minor Planet Center.

Provisional designations for interstellar objects will be handled using the C/ or A/ prefix (as appropriate), with the designation using the comet system.

Accordingly, the object A/2017 U1 receives the permanent designation 1I and the name ʻOumuamua. The name, which was chosen by the Pan-STARRS team, is of Hawaiian origin and reflects the way this object is like a scout or messenger sent from the distant past to reach out to us (ʻou means reach out for, and mua, with the second mua placing emphasis, means first, in advance of).

Correct forms for referring to this object are therefore: 1I; 1I/2017 U1; 1I/ʻOumuamua; and 1I/2017 U1 (ʻOumuamua).

This first interstellar object is being handled as a special case. A small committee of the WGSBN will be created to codify the circumstances under which an object will qualify for an I-number and the rules that will apply to the names, bearing in mind the precedent set by this case. A formal report will follow their deliberations.

SpaceAholicFrom Wired, The Physics Behind the Strange Interstellar Asteroid 'Oumuamua:
If you want to learn the answers to more "how do you know"-type questions about 'Oumuamua, check out this awesome NASA FAQ. But if you want to calculate some answers for yourself — well, just keep reading.
SpaceAholicScientists are about to listen very closely for radio signals from our solar system's first known interstellar visitor, Scientific American reports.
So far limited observations of 'Oumuamua, using facilities such as the SETI Institute's Allen Telescope Array, have turned up nothing. But this Wednesday at 3 p.m. Eastern time, the Breakthrough Listen project will aim the West Virgina-based 100-meter Green Bank Telescope at 'Oumuamua for 10 hours of observations in a wide range of radio frequencies, scanning the object across its entire rotation in search of any signals.
denali414Hopefully SETI can get more data from the Greenbank telescope today...
Hart Sastrowardoyo
quote:
Originally posted by SpaceAholic:
Scientists are about to listen very closely for radio signals from our solar system's first known interstellar visitor...
Nuh-uh. Just ask Commander Branch at Epsilon IX what happened when they tried to scan an object....
PhilipAny ideas if the 300m Arecibo dish on Puerto Rico was used to analyze the shape of this thing?

Moreover, the Chinese already operate a 500m FAST radio telescope. Radar can be used to get an idea of the exact shape of an asteroid and its rotational behavior!

Robert PearlmanBreakthrough Listen release
Breakthrough Listen Releases Initial Results and Data from Observations of 'Oumuamua

No evidence of artificial signals emanating from the object so far detected by the Green Bank Telescope, but monitoring and analysis continue. Initial data are available for public inspection in the Breakthrough Listen archive.

Breakthrough Listen – the initiative to find signs of intelligent life in the universe – is reporting preliminary results and making initial data available from its observations of the "interstellar visitor" 'Oumuamua.

The initial block of observations (the first of a planned four blocks) ran from 3:45pm to 9:45pm ET on Wednesday, December 13, using the Breakthrough Listen backend instrument on the Robert C. Byrd Green Bank Telescope in West Virginia. Listen observed 'Oumuamua across four radio bands (corresponding to four of the radio receivers available at Green Bank, denoted L, S, X, and C), spanning billions of individual channels across the 1 to 12 GHz range.

In addition to calibration observations, the instrument accumulated 90 TB of raw data over a 2 hour observation of 'Oumuamua itself. A search for signals that may be of artificial origin has begun, but despite the impressive computational power of the Breakthrough Listen computing cluster at Green Bank, the large data volumes mean that this will take some time to complete.

"It is great to see data pouring in from observations of this novel and interesting source," said Andrew Siemion, Director of Berkeley SETI Research Center. "Our team is excited to see what additional observations and analyses will reveal"

The Breakthrough Listen "turboSETI" pipeline combs the data for narrow bandwidth signals that are drifting in frequency. By matching the rate at which these signals drift to the expected drift due to the motion of 'Oumuamua (in addition to rejecting interfering signals from human technology that do not match the sky position of the primary target), the software attempts to identify any signals that might be coming from 'Oumuamua itself.

No such signals have been detected, although the analysis is not yet complete. So far, data from the S-band receiver (covering frequencies from 1.7 to 2.6 GHz) has been processed, and analysis of the remaining three bands is ongoing. A subset of the S-band data is now available for public inspection in the Breakthrough Listen archive, and additional data will be added as it becomes available.

The data is stored in specialized formats, and analyzing it may be challenging for non-experts. We invite those who are interested to study the tutorial material provided by the Breakthrough Listen science team at the University of California, Berkeley, SETI Research Center and to assist with the analysis not only of this intriguing object, but of the entire Breakthrough Listen dataset.

Robert Pearlman
quote:
Originally posted by Philip:
Any ideas if the 300m Arecibo dish on Puerto Rico was used to analyze the shape of this thing?
At last update (last month), Arecibo is still running off of backup generators and has months of repairs remaining before it can resume normal operations after Hurricane Maria.
Robert Pearlman'Oumuamua is an icy comet rather than a rocky asteroid, reports Nature.
Careful observations of 'Oumuamua's orbit showed that as the object flew through space, something continually nudged it a tiny bit farther from the Sun than expected. That something was probably ice that warmed up and sprayed gas into space. This process is characteristic of a comet, rather than an asteroid, even though 'Oumuamua never displayed the glorious tail of gas and dust that accompanies most comets.

"It's an unusual comet, and that's pretty exciting," says Karen Meech, an astronomer at the University of Hawaii in Honolulu. She and her colleagues, led by astronomer Marco Micheli of the European Space Agency in Frascati, Italy, report the discovery on 27 June in Nature.

Blackarrow
...as the object flew through space, something continually nudged it a tiny bit farther from the Sun than expected. That something was probably ice that warmed up and sprayed gas into space.
...or reaction control jets? It WAS Rama!
GilbertWe should be on the lookout for two more...
SpaceAholicCould Oumuamua be an extra-terrestrial solar sail?
...there has also been some speculation that based on its shape, 'Oumuamua might actually be an interstellar spacecraft (Breakthrough Listen even monitored it for signs of radio signals!). A new study by a pair of astronomers from the Harvard Smithsonian Center for Astrophysics (CfA) has taken it a step further, suggesting that 'Oumuamua may actually be a light sail of extra-terrestrial origin.

The study – "Could Solar Radiation Pressure Explain 'Oumuamua's Peculiar Acceleration?", which recently appeared online – was conducted by Shmuel Bialy and Prof. Abraham Loeb. Whereas Bialy is a postdoctoral researcher at the CfA's Institute for Theory and Computation (ITC), Prof. Loeb is the director of the ITC, the Frank B. Baird Jr. Professor of Science at Harvard University, and the head chair of the Breakthrough Starshot Advisory Committee.

Robert PearlmanNASA release
NASA Learns More About Interstellar Visitor 'Oumuamua

In November 2017, scientists pointed NASA's Spitzer Space Telescope toward the object known as 'Oumuamua — the first known interstellar object to visit our solar system. The infrared Spitzer was one of many telescopes pointed at 'Oumuamua in the weeks after its discovery that October.

'Oumuamua was too faint for Spitzer to detect when it looked more than two months after the object's closest aproach to Earth in early September. However, the "non-detection" puts a new limit on how large the strange object can be. The results are reported in a new study published Nov. 14 in the Astronomical Journal and coauthored by scientists at NASA's Jet Propulsion Laboratory in Pasadena, California.

The new size limit is consistent with the findings of a research paper published earlier this year, which suggested that outgassing was responsible for the slight changes in 'Oumuamua's speed and direction as it was tracked last year: The authors of that paper conclude the expelled gas acted like a small thruster gently pushing the object. That determination was dependent on 'Oumuamua being relatively smaller than typical solar system comets. (The conclusion that 'Oumuamua 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 Spitzer might show," said David Trilling, lead author on the new study and a professor of astronomy at Northern Arizona University. "The fact that 'Oumuamua was too small for Spitzer to detect is actually a very valuable result."

'Oumuamua was first detected by the University of Hawaii's Pan-STARRS 1 telescope on Haleakala, Hawaii (the object's name is a Hawaiian word 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 the sunlight reflected off 'Oumuamua's surface. Large variations in the object's brightness suggested that 'Oumuamua is highly elongated and probably less than half a mile (2,600 feet, or 800 meters) in its longest dimension.

But Spitzer tracks asteroids and comets using the infrared energy, or heat, that they radiate, which can provide more specific information about an object's size than optical observations of reflected sunlight alone would.

The fact that 'Oumuamua was too faint for Spitzer to detect sets a limit on the object's total surface area. However, since the non-detection can't be used to infer shape, the size limits are presented as what 'Oumuamua's diameter would be if it were spherical. Using three separate models that make slightly different assumptions about the object's composition, Spitzer's non-detection limited 'Oumuamua's "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 stems from the assumptions about 'Oumuamua's 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 comets that reside in our 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 determine the temperature of a comet or asteroid; in turn, this can be used to determine the reflectivity of the object's 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's albedo can change throughout its lifetime. When it passes close to the Sun, a comet's ice warms and turns directly into a gas, sweeping dust and dirt off the comet's surface and revealing more reflective ice.

'Oumuamua had been traveling through interstellar space for millions of years, far from any star that could refresh its surface. But it may have had its surface refreshed through such "outgassing" when it made an extremely close approach to our Sun, a little more than five weeks before it was discovered. In addition to sweeping away dust and dirt, some of the released gas may have covered the surface of 'Oumuamua with a reflective coat of ice and snow — a phenomenon that's also been observed in comets in our solar system.

'Oumuamua is on its way out of our solar system — almost as far from 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."

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