On October 19, 2017, the first detected interstellar object flew past Earth on its way out of the Solar System. Less than two years later, a second object was detected, an easily identifiable interstellar comet designated 2I / Borisov.
The appearance of these two objects verified earlier theoretical work that concluded that interstellar objects (ISO) regularly enter our Solar System.
The question of how often this happens has been the subject of considerable investigation since then. According to a new study led by researchers from the Interstellar Studies Initiative (i4is), approximately seven ISOs enter our Solar System each year and follow predictable orbits while they are here.
This research could allow us to send a spaceship to encounter one of these objects in the near future.
The research describing these findings was conducted by multiple researchers at i4is, a nonprofit organization dedicated to conducting interstellar flight in the very near future.
They were joined by researchers from the Florida Institute of Technology, the Harvard Institute for Theory and Computing (ITC), the University of Texas at Austin, the Technical University of Munich and the Observatoire de Paris.
The study of ‘Oumuamua in October 2017 triggered 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 implied a large population of such objects.
The detection of 2I / Borisov in 2019 confirmed what many astronomers already suspected: that ISOs enter our Solar System quite regularly.
In addition to being an i4is physicist (and the lead author of the study), Marshall Eubanks is the chief scientist at Space Initiatives Inc. and the 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]Just by proving they exist, it has had a profound impact, creating a field of study almost out of nowhere (a field that funding authorities are only beginning to recognize). Interstellar objects give us the opportunity to study, and in the future literally touch, exobbodies decades before the first possible missions to even the closest stars, such as Proxima Centauri. “
This led to multiple mission proposals that could meet future ISOs that were spotted passing through our system. One such proposal was Project Lyra, which i4is researchers shared in a 2017 study (supported by Asteroid Initiatives LLC).
There’s also ESA’s Comet Interceptor mission, which they plan to launch in 2029 to encounter a long-period comet.
“We started working on potential missions to interstellar objects in 2017, right after the discovery of ‘Oumuamua and initially we focused quite a bit on chasing that specific object, in contrast to Seligman & Laughlin, who focused on ISOs that could be discovered in the future, Eubanks said.
“The Comet Interceptor mission would fall into a similar category (build and wait).”
Since the ISOs were formed in another star system, the opportunity to study them closely would offer scientists an idea of the conditions that are present there. In fact, studying ISOs is the best alternative to sending interstellar probes to neighboring star systems.
Of course, any mission of this type involves many technical challenges, not to mention the need for advance warning. As Eubanks explained:
“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, such as those that would be necessary to get to 1I / ‘Oumuamua. It is very little. Chase missions will likely encounter a retreating ISO; they will almost certainly be limited to fast flyovers. Encounter missions, missions to equalize speeds and orbit or land the ISO, will need advance warning. “
To illustrate, when astronomers first became aware of ‘Oumuamua, it was only after the object had already gotten closer to the Sun (also known as the perihelion pass) and had passed close to 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.
In the case of 2I / Borisov, it was spotted on August 30, 2019 by amateur astronomer and telescope maker Gennadiy Borisov, about three months before it reached perihelion (December 8, 2019).
But for future missions to meet them, it is imperative to know as much as possible about how often ISOs arrive and how quickly they travel when they do.
For the sake of their study, Eubanks and his colleagues sought to put better restrictions on these two variables. To do this, they started by considering how the speed of an interstellar object is influenced by the local standard of rest (LSR), the average motion of stars, gas, and dust in the Milky Way in the vicinity of the Sun:
“We assume that the ISOs come from or are formed by stars and their planetary systems, and that after being alone they share the same galactic dynamics as the stars. We use the two known ISOs, 1I / ‘Oumuamua and 2I / Borisov, and the efficiency of past and current astronomical studies to estimate the number of these objects in the galaxy, and stellar velocity estimates from the Gaia mission to estimate the velocity dispersion that we should expect. “
What they found was that in an average year, the Solar System would be visited by up to seven ISOs that are similar to an asteroid. Meanwhile, objects like 2I / Borisov (comets) would be rarer, appearing once every 10 to 20 years.
Furthermore, they found that many of these objects would move at speeds greater than those of ‘Oumuamua, which was moving at more than 26 km / s before and after receiving a boost from the Sun.
Knowing these parameters will help scientists prepare for potential ISO rendezvous missions, something Eubanks and his colleagues covered in more detail in a previous study: “Interstellar now! Missions to explore nearby interstellar objects.”
As Universe Today reported at the time of its launch, the study addressed a broader range of potential ISOs and the feasibility of achieving them.
Meanwhile, this latest study provides basic information that will support the planning and implementation of these missions. In addition to Project Lyra and ESA’s Comet Interceptor, there are numerous proposals for spacecraft that could encounter interstellar objects (or even do interstellar travel themselves).
These include Project Dragonfly, a small spacecraft, and a 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 introduced by Yuri Milner and Breakthrough Initiatives that also calls for a small spaceship to be sent to Alpha Centauri using a light sail and a powerful laser array.
This proposal has been articulated in recent years by Prof. Abraham Loeb and Prof. Manasvi Lingam. While Leob is the founder of the ITC and chair of the Starshot Advisory Committee, Lingham is a longtime ITC researcher and co-author of “Interstellar Now!” and this last article.
In addition to going interstellar, these concepts have been proposed as a possible way to “chase objects” entering our Solar System.
One way or another, we will soon peak in other star systems! And knowing how to intercept and study objects that periodically kick us is a good way to start!
This article was originally published by Universe Today. Read the original article.