Originally, scientists thought that the cigar-shaped object was a very strange passing asteroid. But a number of factors have led scientists involved in the search for alien life to wonder whether it might actually be an “artifact” from an alien civilization.
Researchers involved in the Search for Extra-Terrestrial Intelligence (Seti) project are now preparing to point a powerful telescope at the bizarre object and figure out where it came from.
The mysterious object, which has been named ‘Oumuamua, is the first known interstellar visitor from another part of the galaxy to pass through the Solar System. Formally designated 1I/2017 U1, it was discovered by Robert Weryk and astronomers from the University of Hawaii using the Pan-STARRS telescope on October 19, 2017. Remarkably, the interstellar object slipped through the inner solar system a month ago unnoticed, passing within 37,600,000 km (23,400,000 miles) of the Sun on September 9th.
Scientists initially presumed that it was a comet or an asteroid. However, a number of strange characteristics have led them to wonder whether it might have actaully been intentionally formed.
The unknown object is racing swiftly through the universe at a speed of up to 196,000 mph, and it is expexted to fly unhindered as it zips right through our Sun’s gravity and out of the solar system.
Researchers have been marshaling telescopes around the world to learn as much as possible about this interloper before it slips out of visual range, never to be seen again. The flurry of activity hasn’t been limited to making observations, as officials at the International Astronomical Union struggled with what to call this body. At first astronomers thought it was a comet, based on its extreme orbit, and so the IAU’s Minor Planet Center applied the designation C/2017 U1. But when even the deepest telescopic images revealed no hint of a coma or tail, they decided it must be asteroidal, so the designation morphed to A/2017 U1.
Behind the scenes, in an unusual effort to name the new object quickly, emails zipped back and forth among the IAU’s General Secretary, its Division F president, co-chairs of the IAU’s Working Group on Small Body Nomenclature, and the Minor Planet Center. The chosen name, submitted by the team at the Pan-STARRS telescope who discovered it and announced November 6th, is ‘Oumuamua. It’s a Hawaiian construct combining ‘ou (to reach out) and mua (meaning first or in advance of). The second mua is for emphasis.
But asteroids are not catalogued by name alone, and this is the first of an entirely new class of object. So, at the suggestion of MPC associate director Gareth Williams, the IAU adopted the identifier “I”, for interstellar. “All parties involved in the discussion agreed that the proposal was suitable,” he says. “Took less than a day to sort out, announcement followed the day after.” As noted in the announcement on MPEC 2017-V17:
“Correct forms for referring to this object are therefore: 1I; 1I/2017 U1; 1I/’Oumuamua; and 1I/2017 U1 (‘Oumuamua).”
Those who work the comet and asteroid trade aren’t enamored with the use of “I” — after all, the IAU has gone out of its way to avoid using “I” and “O” in designations because they look too much like the numerals “1” and “0”. Several have suggested substituting “E” (for extrasolar) instead, but Williams defends the IAU’s decision, noting that “E” could be interpreted as “extraterrestrial”, with the implication of intelligence behind the object, and “G” (for “galactic”) is too limiting.
The characteristic of ‘Oumuamua as being from outside our solar system is its orbital eccentricity, 1.19. Recall from your high-school geometry that the eccentricity of an ellipse can’t exceed 1.0. In fact, dynamicist Bill Gray (Project Pluto) regrets that he didn’t pick up on 1I’s interstellar nature a few days sooner — his orbit-calculation software kept rejecting the eventual solution as being impossible.
The object had already dimmed to 20th magnitude by the time the Pan-STARRS 1 telescope swept it up, so observers worldwide had to scramble to get major facilities to gather more observations before the one-of-a-kind interloper becomes impossibly faint.
One lucky break came immediately after the MPC’s initial announcement. Observer Joe Masiero (Jet Propulsion Laboratory) just happened be in the middle of a run with the 5-m Hale Telescope at Palomar Observatory, and he quickly obtained a spectrum that’s reproduced below and explained in more detail here. There’s no obvious absorption that would signify the presence of, say, methane or silicate minerals.
A spectrum of ‘Oumuamua (1I/2017 U1), pictured right; acquired on October 25, 2017 with the 5-m Hale Telescope. Vertical bars indicate error bars at each measured wavelength, and the dotted line shows the overall trend to slightly brighter red and near-infrared wavelengths.
But the gentle slope, increasing toward the red (right) end, suggests that ‘Oumuamua is not a particularly good match to objects in the Kuiper Belt (which tend to be much redder). Instead, it’s the kind of spectrum that a rocky surface would exhibit after being “weathered” by long-term exposure to space radiation.
Others have attempted to record the object’s light curve and determine its rotation period. Observations by Matthew Knight (University of Maryland) and others show clear variations in the apparent brightness of about 1.2 magnitudes. Knight and his team suspect the object is highly elongated, at least three times longer than it is wide, and rotates with a period of between 3 and 5 hours.
The Hubble Space Telescope might have the final word on the character of 1I/2017 U1. A team led by Karen Meech (University of Hawaii) has been granted HST time to study the quickly disappearing interloper. “Our observations have not executed yet,” Meech says, “and the experiment requires three visits — the last of which will be at the end of the year.”
And, of course, there’s been a flurry of speculation about where ‘Oumuamua came from. Dynamicist Eric Mamajek (Jet Propulsion Laboratory) points out that object’s incoming velocity (26 km per second) is within 5 km/s of the mean galactic velocity of stars within 25 parsecs (80 light-years) of the Sun but does not match the relative velocity any of the dozen nearest systems. These characteristics all suggest that ‘Oumuamua has been drifting among the stars for a very long time, perhaps billions of years.
A statement from the 100 million dollar (£75 million) Seti project Breakthrough Listen, launched by Russian digital tech mogul Yuri Milner in 2015, said:
“Researchers working on long-distance space transportation have previously suggested that a cigar or needle shape is the most likely architecture for an interstellar spacecraft, since this would minimise friction and damage from interstellar gas and dust.
“While a natural origin is more likely, there is currently no consensus on what that origin might have been, and Breakthrough Listen is well positioned to explore the possibility that Oumuamua could be an artifact.”
The Breakthrough Listen team is using the Green Bank radio telescope in West Virginia, US, to study ‘Oumuamua, which is named after the Hawaian term for “scout” or “messenger”.
From 8pm UK time on December 12, the giant dish – the largest fully steerable radio telescope in the world – will “listen” to the object across four radio frequency bands spanning one to 12 gigahertz.
Lead scientist Dr Andrew Siemion, director of the Berkeley Seti Research Centre in California, said: “Oumuamua’s presence within our solar system affords Breakthrough Listen an opportunity to reach unprecedented sensitivities to possible artificial transmitters and demonstrate our ability to track nearby, fast-moving objects.
“Whether this object turns out to be artificial or natural, it’s a great target for Listen.”
The object is currently about two astronomical units (AU) from Earth, or twice the distance between the Earth and sun.
At this distance it would take less than a minute for the Green Bank telescope to detect an omnidirectional transmitter with the power of a mobile phone.
Even if no evidence of extraterrestrial technology is found, the search could provide important information about gases surrounding ‘Oumuamua or the presence or absence of water, say the researchers.
Breakthrough Listen aims to survey a million nearby stars and 100 nearby galaxies looking for alien signals.
Since the 1960’s, there have been more than 98 Seti projects around the world, none of which have turned up any convincing evidence of extraterrestrial civilizations.
* Expanded from original sources:
- “Update on ‘Oumuamua, Our First Interstellar Object” by Kelly Beatty, originally published on November 10, 2017 at Sky and Telescope.
- “Huge, Mysterious Object Flying Past Earth Might Be An Alien Spacecraft, Scientists Say” by Andrew Griffin, originally published on December 12, 2017 at The Independent UK.