It sounds like the premise of a Michael Crichton techno-thriller or maybe a water-soaked James Cameron blockbuster in the spirit of The Abyss. But it isn’t. Astronomers at NASA believe that they really might have found water from another planetary system on an interstellar comet. If they’re correct, this would be the first time in human history that water hailing from another planetary system has been discovered within our solar system. That, as Anchorman’s Ron Burgundy might say, is kind of a big deal.
The story, at least from Earth’s point of view, began in late August this year. That’s when an amateur Ukrainian astronomer named Gennady Borisov discovered an interstellar object located near to the Gemini constellation, approximately 12,000 light years from Earth. Named 2I/Borisov after its discoverer, this comet (initially thought to an asteroid) is only the second interstellar object to ever be observed passing through our solar system. The first was ‘Oumuamua in 2017.
An artist’s rendition of the first interstellar asteroid: `Oumuamua.
Bigger and brighter than ‘Oumuamua, Borisov will be observable for at least one year. It will come around 300 million km (about 186 million miles) closer to the sun in December, giving scientists an opportunity to observe it.
Imaging the unknown
They haven’t wasted time, however. Already 2I/Borisov has been imaged by astronomers from the Institute for Astrophysics of the Canaries and, more recently, using the Hubble Space Telescope. Courtesy of a 3.5-meter telescope at the Apache Point Observatory in New Mexico, astronomers from NASA found large amounts of oxygen around the comet, suggesting water vapor as water ice is sublimated from solid into gas. Well, sort of. What they actually observed was this vapor being torn apart into separate hydrogen and oxygen molecules by ultraviolet light from the sun. One small light show for man; one potential “secrets of the universe” physics seminar for mankind.
“We obtained optical spectroscopy of interstellar comet 2I/Borisov in order to search for atomic oxygen in the coma, the temporary atmosphere of gas and dust that surrounds a comet when it gets close to the sun,” Adam McKay, a Postdoctoral Fellow at NASA’s Goddard Space Flight Center in Maryland, told Digital Trends. “Spectroscopy takes the light coming from the comet and splits it into its component colors. Atomic oxygen has a strong feature in the red-orange region of the spectrum, and we were able to detect this feature in Borisov. As oxygen in cometary comae is usually released from the breakup of water molecules, we can use the observed signature of oxygen to measure the amount of H2O present in the comet.”
A whole lot of water (probably)
Their findings suggest that the comet is currently shedding around 42 pounds of water every single second, from an area covering just over one square mile.
“For Borisov, measuring the amount of water present is critical for comparing this interstellar comet to the comets we observe in our own solar system,” McKay said. “[It is also interesting for] interpretation of other observations of this comet, including the evolution of its activity. This finding, in conjunction with observations of other molecules like [cyanide], will help address how similar or different Borisov is to solar system comets. [In turn, this] can shed light on how similar the conditions under which our planets and comets formed are to those present in other planetary systems.”
Gemini Observatory two-color composite image of C/2019 Q4 (Borisov) which is the first interstellar comet ever identified Gemini Observatory/NSF/AURA
There is a chance that this is not water, but rather oxygen coming from carbon monoxide or carbon dioxide. However, the observations made so far suggest that water is the most likely possibility. Most comets contain water. But this is the first time they’ve been able to observe this on an asteroid hailing from deep space.
“We [next] plan to obtain additional observations of atomic oxygen to observe how the water production changes as the comet moves towards the sun,” McKay continued. “We will also compare these new measurements to observations of other molecules to gain more insight into the composition of Borisov’s ices, as well as see if there are any changes in the composition of the coma.”
The next step
The NASA astronomers hope that future observations will help them better understand the role of water in driving activity on Borisov. One thing’s for sure: this is far from the end of this particular story. “More observations and modeling efforts are needed to fully understand this interstellar visitor,” he said.
Could the answers help shed life on the likelihood of life in other parts of the universe? Given how crucial water has been to life on our own planet, it’s certainly something that McKay and his colleagues will be considering every step of the way.
A paper describing the work so far, titled “Detection of a Water Tracer in Interstellar Comet 2I/Borisov,” is available to read online.