☀️ — Hypervelocity stars : a way to travel faster

Translated from « Archipel de pensées » 2018 

In this micro-paper, I propose an original way to achieve intergalactic travel using hypervelocity stars. This could also be used for travel inside a galaxy, like the Milky Way. To address the question of intergalactic travel, we will first recall what a hypervelocity star is.

This kind of star, named hypervelocity stars are stars that move at an abnormally high speed. These hypervelocity stars move so quickly that they can free themselves from the gravitational pull of a galaxy. The fastest hypervelocity star recorded moves at 1200 km/s {1], an order of magnitude that is difficult to imagine. By comparison, fast stars move at 800 km/s, and our Sun moves "only" at 230 km/s around the center of our galaxy [Ibid]. In 2019 a team even found a hypervelocity star going near 1700 km/s [2].

Their creation might come from a binary star system expelling its twin in a supernovae [3].

Researchers at the Harvard-Smithsonian Center for Astrophysics have performed numerical simulations to find out what would happen to the planets orbiting these stars in the scenario where one of the stars was ejected [4]. The results show that the planets themselves could be torn from their star, and acquire dizzying speeds, of the order of 15 to 50 million km/h. However, there is also a chance that these planets would remain in orbit around their star, and therefore that they would be animated by the same speed. This alternative scenario has also been predicted by numerical simulations.

The idea put forward in this document proposes the colonization of exoplanets located around a hypervelocity star to move quickly in the Milky Way, or even to another galaxy. With a view to rapid exploration of the Milky Way, humanity could choose to install a human colony on a planet in orbit around a hypervelocity star on a desired exploration trajectory.

The speed of 1200 km/s represents 0.4% of the speed of light (C), in comparison, the fastest maned space propulsion system is currently of 20 km/s or 6 hundredths of a thousandth of the speed of light (6×10-5%). A hypervelocity star of this category is therefore 10,000 times faster than our most advanced means of propulsion. In this way, even if the time scale remains astronomical, it would be possible to move through the Milky Way more quickly, and even seed new colonies on the trajectory of the hypervelocity star.

Another interesting point, some hypervelocity stars observed come from the neighboring dwarf galaxy: the Large Magellanic Cloud. This hypothesis as to their origin was confirmed thanks to numerical simulations carried out by Douglas Boubert of the Institute of Astronomy in Cambridge in England, by calculating the trajectories that these hypervelocity stars would have taken [5]. The Large Magellanic Cloud would have ejected more than 10,000 stars in the direction of the Milky Way over the last 2 billion years. According to researcher Douglas Boubert : 

"If this scenario is correct, there should be a whole bunch of hypervelocity stars between the current position of the Large Magellanic Cloud and the constellation of Leo" 

So theoretically, if we make sure to take the right trajectory, the idea of moving to another galaxy using hypervelocity stars conceivable — or, that other intelligent species would be do it to come to the Milky Way. It would then be necessary to colonize one or more planets in orbit around this hypervelocity star before it leaves the galaxy, and then prepare for a long journey.

To develop this idea further, an advanced civilization could choose to immerse itself in a "stasis", a sleep on the scale of an entire species, for the entire time of the journey, and wake up once it arrives in the new galaxy, which it can then colonize.