Greenbank Radio Telescope Archives

On October 19th, 2017, the Panoramic Survey Telescope and Rapid Response System-1 (Pan-STARRS-1) in Hawaii announced the first-ever detection of an interstellar object, named 1I/2017 U1 (aka. ‘Oumuamua). After originally hypothesizing that it was a comet, observations performed by the European Southern Observatory (ESO) and other astronomers indicated that it was likely a strange-looking asteroid measuring about 400 meters (1312 ft) long.

Since that time, multiple surveys have been conducted to determine the true nature of this asteroid, which have included studies of its composition to Breakthrough Listen‘s proposal to listen to it for signs of radio transmissions. And according to the latest findings, it seems that ‘Oumuamua may actually be more icy than previously thought (thus indicated that it is a comet) and is not an alien spacecraft as some had hoped.

The first set of findings were presented in a study that was recently published in the scientific journal Nature, titled “Spectroscopy and thermal modelling of the first interstellar object 1I/2017 U1 ‘Oumuamua“. The study was led by Alan Fitzsimmons of Queen’s University Belfast, and included members from The Open University in Milton Keynes, the Institute for Astronomy (IfA) at the University of Hawaii, and the European Southern Observatory (ESO).

*‘Oumuamua, as imaged by the William Herschel Telescope on October 29th, 2017. Credit: Queen’s University Belfast/William Herschel Telescope*

As they indicate in their study, the team relied on information from the ESO’s Very Large Telescope in Chile and the William Herschel Telescope in La Palma. Using these instruments, they were able to obtain spectra from sunlight reflected off of ‘Oumuamua within 48 hours of the discovery. This revealed vital information about the composition of the object, and pointed towards it being icy rather than rocky. As Fitzsimmons explained in op-ed piece in The Conversation:

“Our data revealed its surface was red in visible light but appeared more neutral or grey in infra-red light. Previous laboratory experiments have shown this is the kind of reading you’d expect from a surface made of comet ices and dust that had been exposed to interstellar space for millions or billions of years. High-energy particles called cosmic rays dry out the surface by removing the ices. These particles also drive chemical reactions in the remaining material to form a crust of chemically organic (carbon-based) compounds.”

These findings not only addressed a long-standing question about ‘Oumuamua true nature, it also addresses the mystery of why the object did not experience outgassing as it neared our Sun. Typically, comets experience sublimation as they get closer to a star, which results in the formation of a gaseous envelope (aka. “halo”). The presence of an outer layer of carbon-rich material would explain why this didn’t happen ‘Oumuamua.

They further conclude that the red layer of material could be the result of its interstellar journey. As Fitzsommons explained, “another study using the Gemini North telescope in Hawaii showed its color is similar to some ‘trans-Neptunian objects’ orbiting in the outskirts of our solar system, whose surfaces may have been similarly transformed.” This red coloring is due to the presence of tholins, which form when organic molecules like methane are exposed to ultra-violet radiation.

Similarly, another enduring mystery about this object was resolved thanks to the recent efforts of Breakthrough Listen. As part of Breakthrough Initiatives’ attempts to explore the Universe and search for signs of Extra-Terrestrial Intelligence (ETI), this project recently conducted a survey of ‘Oumuamua to determine if there were any signs of radio communications coming from it.

While previous studies had all indicated that the object was natural in origin, this survey was more about validating the sophisticated instruments that Listen relies upon. The observation campaign began on Wednesday, December 13th, at 3:00 pm EST (12:00 PST) using the Robert C. Byrd Greenbank Radio Telescope, the world’s premiere single-dish radio telescope located in West Virginia.

The observations period was divided into four “epochs” (based on the object’s rotational period), the first of which ran from 3:45 pm to 9:45 pm ET (12:45 pm to 6:45 pm PST) on Dec 13th, and last for ten hours. During this time, the observation team monitored ‘Oumuamua across four radio bands, ranging from the 1 to 12 GHz bands. In addition to calibrating the instrument, the survey accumulated 90 terabytes of raw data over after observing ‘Oumuamua itself for two hours.

The initial results and data were released last week (Dec. 13th) and are available through the Breakthrough Listen archive. As Andrew Siemion – the Director of Berkeley SETI Research Center who took part in the survey – indicated in a Breakthrough Initiatives press release:

“It is great to see data pouring in from observations of this novel and interesting source. Our team is excited to see what additional observations and analyses will reveal”.

So far, no signals have been detected, but the analysis is far from complete. This is being conducted by Listen’s “turboSETI” pipeline, which combs the data for narrow bandwidth signals that are drifting in frequency. This consists of filtering out interference signals from human sources, then matching the rate at which signals drift relative to the expected drift caused by ‘Oumuamua’s own motion.

In so doing, the software attempts to identify any signals that might be coming from ‘Oumuamua itself. So far, data from the S-band receiver (frequencies ranging from 1.7 to 2.6 GHz) has been processed, and analysis of the remaining three bands – which corresponds to receivers L, X, and C is ongoing. But at the moment, the results seem to indicate that ‘Oumuamua is indeed a natural object – and an interstellar comet to boot.

This is certainly bad news for those who were hoping that ‘Oumuamua might be a massive cylinder-shaped generation ship or some alien space probe sent to communicate with the whales! I guess first contact – and hence, proof we are NOT alone in the Universe – is something we’ll have to wait a little longer for.

Further Reading: The Conversation, Nature, Breakthrough Initiatives

On October 19th, 2017, the Panoramic Survey Telescope and Rapid Response System-1 (Pan-STARRS-1) in Hawaii announced the first-ever detection of an interstellar asteroid, named 1I/2017 U1 (aka. ‘Oumuamua). Based on subsequent measurements of its shape (highly elongated and thin), there was some speculation that it might actually be an interstellar spacecraft (the name “Rama” ring a bell?).

For this reason, there are those who would like to study this object before it heads back out into interstellar space. While groups like Project Lyra propose sending a mission to rendezvous with it, Breakthrough Initiatives (BI) also announced its plans to study the object using Breakthrough Listen. As part of its mission to search for extra-terrestrial communications, this project will use the Greenbank Radio Telescope to listen to ‘Oumuamua for signs of radio transmissions.

Observations of ‘Oumuamua’s orbit revealed that it made its closest pass to our Sun back in September of 2017, and has been on its way back to interstellar space ever since. When it was observed back in October, it was passing Earth at a distance of about 85 times the distance between Earth and the Moon, and was traveling at a peak velocity of about 315,430 km/h (196,000 mph).

This indicated that, unlike the many Near-Earth Objects (NEOs) that periodically cross Earth’s orbit, this asteroid was not gravitationally bound to the Sun. In November, astronomers using the ESO’s Very Large Telescope (VLT) at the Paranal Observatory in Chile were also able to determine the brightness and color of the asteroid, which allowed for precise calculations of its size and shape.

Basically, they determined that it was 400 meters (1312 ft) long and very narrow, indicating that it was shaped somewhat like a cigar. What’s more, the idea of a cigar or needle-shaped spacecraft is a time-honored concept when it comes to science fiction and space exploration. Such a ship would minimize friction and damage from interstellar gas and dust, and could rotate to provide artificial gravity.

For all of these reasons, it is understandable why some responded to news of this asteroid by making comparisons to a certain science fiction novel. That would be Arthur C. Clarke’s Rendezvous with Rama, a story of a cylindrical space ship that travels through the Solar System while on its way to another star. While a natural origin is the more likely scenario, there is no consensus on what the origin this object might be – other than the theory that it came from the direction of Vega.

Hence why Breakthrough Listen intends to explore ‘Oumuamua to determine whether it is truly an asteroid or an artifact. Established in January of 2016, Listen is the largest scientific research program aimed at finding evidence of extra-terrestrial intelligence with established SETI methods. These include using radio observatories to survey 1,000,000 of the closest stars (and 100 of the closest galaxies) to Earth over the course of ten years.

*Breakthrough Listen will monitor the 1 million closest stars to Earth over a ten year period. Credit: Breakthrough Initiatives*

Listen’s observation campaign will begin on Wednesday, December 13th, at 3:00 pm EST (12:00 PST), using the Greenbank Radio Telescope. This 100-meter telescope is the world’s premiere single-dish radio telescope and is capable of operating at millimeter and submillimeter wavelengths. It is also the mainstay of the NSF-funded Green Bank Observatory, located in West Virginia.

The first phase of observations will last a total of 10 hours, ranging from the 1 to 12 GHz bands, and will broken down into four “epochs” (based on the object’s rotational period). At present, ‘Oumuamua is about 2 astronomical units (AUs) – or 299,200,000 km; 185,900,000 mi – away from Earth, putting it at twice the distance between the Earth and the Sun. This places it well beyond the orbit of Mars, and over halfway between Mars and Jupiter.

At this distance, the Green Bank Telescope will take less than a minute to detect an omni-directional transmitter with the power of a cellphone. In other words, if there is a alien signal coming from this object, Breakthrough Listen is sure to sniff it out in no time! As Andrew Siemion, Director of Berkeley SETI Research Center and a member of Breakthrough Listen, explained in a BI press statement:

“‘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.”

Even if there are no signals to be heard, and no other evidence of extra-terrestrial intelligence is detected, the observations themselves are a opportunity for scientists and the field of radio astronomy in general. The project will observe ‘Oumuamua in portions of the radio spectrum that it has not yet been observed at, and is expected to yield information about the possibility of water ice or the presence of a “coma” (i.e. gaseous envelop) around the object.

During the previous survey, data gathered using the VLT’s FOcal Reducer and low dispersion Spectrograph (FORS) indicated that ‘Oumuamua was likely a dense and rocky asteroid with a high metal content and little in the way of water ice. Updated information provided by the Greenbank Telescope could therefore confirm or cast doubt on this, thus reopening the possibility that it is actually a comet.

Regardless of what it finds, this survey is likely to be a feather in the cap of Breakthrough Listen, which already demonstrated it’s worth in terms of non-SETI astronomy this past summer. At that time, and using the Green Bank Radio Telescope, the Listen science team at UC Berkeley observed 15 Fast Radio Bursts (FRBs) for the fist time coming from a dwarf galaxy three billion light-years from Earth.

Still, I think we can all agree that an extra-terrestrial spaceship would be the most exciting possibility (and perhaps the most frightening!). And it is very safe to say that some of us will be awaiting the results of the survey with baited breath. Luckily, we’ll only have to wait two more days to see if humanity is still alone in the Universe or not! Stay tuned!

Further Reading: Breakthrough Initiatives

Tag: Greenbank Radio Telescope

Updates on ‘Oumuamua. Maybe it’s a Comet, Actually. Oh, and no Word From Aliens.

Breakthrough Listen is Going to Scan ‘Oumuamua, You Know, Just to be Sure it’s Just an Asteroid and Not a Spaceship.