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On October 19, 2017, the first interstellar object ever detected flew over Earth as it exited the solar system. Less than two years later, a second object was detected, an easily identifiable interstellar comet called 2I / Borisov.
The appearance of these two objects verified previous theoretical work which concluded that interstellar objects (ISO) regularly enter our solar system.
The question of how often this happens has since been the subject of considerable research. According to a new study by researchers at the Initiative for Interstellar Studies (i4is), about seven ISOs enter our solar system each year and follow predictable orbits while they are here.
This research could allow us to send a spacecraft to the rendezvous with one of these objects in the near future.
The research that describes these results was conducted by several researchers from i4is, a non-profit organization dedicated to achieving interstellar flights in the very near future.
They were joined by researchers from the Florida Institute of Technology, the Harvard Institute for Theory and Computation (ITC), the University of Texas at Austin, the Technical University of Munich and the Observatory of Paris.
‘Oumuamua through the William Herschel telescope. (Queen’s University Belfast / William Herschel Telescope)
Oumuamua’s study in October 2017 sparked a revolution in astronomy and the study of celestial objects. Not only was it an object that had formed in another star system, but its arrival and detection involved a large population of such objects.
The detection of 2I / Borisov in 2019 confirmed what many astronomers already suspected – that ISOs are entering our solar system quite regularly.
In addition to being a physicist with i4is (and lead author of the study), Marshall Eubanks is the Chief Scientist of Space Initiatives Inc. and CEO of Asteroid Initiatives LLC. As he told Universe Today via email, the discovery of ‘Oumuamua and 2I / Borisov is significant in a way that cannot be underestimated:
“[J]By proving their existence, it has had a profound impact, creating a field of study almost from scratch (an area that funders are just starting to recognize). Interstellar objects offer us the opportunity to study, and in the future, literally touch, exobodies decades before the first possible missions, even to the closest stars, such as Proxima Centauri. “
This led to multiple proposals for missions that could meet future ISOs spotted through our system. One of those proposals was the Lyra project, which i4is researchers shared in a 2017 study (with support from Asteroid Initiatives LLC).
There’s also ESA’s Comet Interceptor mission, which they plan to launch in 2029 to encounter a long-lived comet.
“We started working on potential interstellar object missions in 2017, right after the discovery of ‘Oumuamua and initially rather focused on the pursuit of this specific object, unlike Seligman & Laughlin, which focused on ISOs that might be discovered in the future, ”says Eubanks.
“The Comet Interceptor mission would fall into a similar category (build and hold).”
Since ISOs formed in another star system, being able to study them closely would give scientists a glimpse of the conditions there. In fact, studying ISOs is the best thing to do to send interstellar probes to nearby star systems.
Of course, such a mission involves many technical challenges, not to mention the need for prior warning. As Eubanks explains:
“There are two basic types of missions here: plan and wait, or launch and wait, missions, such as ESA’s Comet Interceptor, and pursuit missions, like those that would be required to reach 1I. / ‘Oumuamua. Pursuit missions will be able to join a retreating ISO – these will almost certainly be limited to quick overflights. Rendezvous missions, missions to match speeds and orbit or land ISO, will need to be warned in advance. “
To illustrate, when astronomers first became aware of ‘Oumuamua, it was only after the object had already made its closest approach to the Sun (aka. Perihelion Passage) and made a near pass. of the earth.
Because of this, observers had only 11 days to make observations as it exited the solar system and was out of range of their instruments.
Artist’s impression of 2I / Borisov beyond our solar system. (S. DagnelloNRAO / NSF / AUI)
In the case of 2I / Borisov, amateur astronomer and telescope maker Gennadiy Borisov saw him on August 30, 2019, about three months before he reached perihelion (December 8, 2019).
But in order for future missions to join them, it’s imperative to know as much as possible about how often ISOs arrive and how fast they move when they do.
For the sake of their study, Eubanks and colleagues sought to better constrain these two variables. To do this, they started by taking into account how the speed of an interstellar object is influenced by the local resting norm (LSR) – the average motion of stars, gas, and dust in the Milky Way at proximity to the Sun:
“We assume that ISOs originate or are formed with stars and their planetary systems, and that after they are alone, they share the same galactic dynamics as stars. We use the two known ISOs, 1I / ‘Oumuamua and 2I / Borisov, and the effectiveness of past and current astronomical surveys in estimating the number of such objects in the galaxy, and the Gaia mission’s stellar speed estimates to estimate the propagation of the speed we should expect. “
What they found was that in an average year, the solar system would be visited by up to seven asteroid-like ISOs. Meanwhile, objects like 2I / Borisov (comets) are said to be rarer, appearing about once every 10 to 20 years.
They further discovered that many of these objects would move at speeds greater than those of ‘Oumuamua – which was moving more than 26 km / s before and after receiving a thrust from the Sun.
Knowing these parameters will help scientists prepare for possible ISO rendezvous missions, which Eubanks and colleagues covered in more detail in a previous study – “Interstellar Now! Missions to Explore Near Interstellar Objects “.
As Universe Today reported at the time of publication, the study looked at a wider range of potential ISOs and the possibility of reaching them.
In the meantime, this latest study provides baseline information that will support the planning and implementation of these missions. In addition to Project Lyra and ESA’s Comet interceptor, there are many proposals for spacecraft that could encounter interstellar objects (or even make the interstellar journey themselves).
These include Project Dragonfly, a small spacecraft and laser sail that was the subject of a conceptual design study organized by the Interstellar Studies Initiative (i4iS) in 2013.
Another is Breakthrough Starshot, a concept proposed by Yuri Milner and Breakthrough Initiatives that also calls for sending a tiny spaceship to Alpha Centauri using a light sail and a powerful laser array.
This proposal has been formulated in recent years by Professor Abraham Loeb and Professor Manasvi Lingam. While Leob is the Founder of ITC and Chairman of the Starshot Advisory Board, Lingham is a longtime researcher at ITC and co-author of “Interstellar Now!” and this last article.
In addition to becoming interstellar, these concepts have been proposed as a possible way to “hunt for objects” that enter our solar system.
Either way, we’ll be reaching other star systems soon! And knowing how to intercept and study the objects they throw at us periodically is a good way to start!
This article was originally published by Universe Today. Read the original article.
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