In fiction, flying through space with the Millennium Falcon in Star Wars required celestial calculations performed by computers or astromech droids, such as R2-D2. But, when we talk about reality, it is difficult to develop something similar. However, Coryn Bailer-Jones, member of the Max Plank Institute for Astronomy (Germany), has taken the first step towards fulfilling the dream of interstellar travel.
At the moment, the object that we have sent the furthest into the Universe is the Voyager 1 space probe. To date, we have been able to update its position through radars and radio signals connected to the Earth. However, this tracking system is similar to a giant umbilical cord. Once the spacecraft is out of signal range, or if the signal is interrupted, Voyager 1 has no internal way to navigate. This will eventually happen, and then the probe will wander through space for hundreds of millions of years without our knowing about it.
Sail in a sea of stars
If we plan the idea of sending ships into deep space, we need a way to navigate between the stars without connecting to Earth. One technique that is being considered is pulsars, which are the remains of dead stars created from supernova explosions.
These pulsars rotate with known frequencies at known distances and could be used as ‘interstellar GPS satellites’. But experts debate how accurate this system is: spacecraft should rely on a handful of pulsars and space dust or gas that could introduce errors into their calculations.
For this reason, Bailer-Jones proposes a method for celestial navigation that has been used for centuries in the oceans: the sextant. This astronomical instrument used at sea is used to measure the “angular distance” between the Sun or another star and the horizon in order to calculate the position on Earth.
In interstellar space the technique would vary somewhat by measuring the angular distance between the stars and their change in position over time in relation to the motion of the spacecraft. This also happens when the Earth orbits around the Sun, since the position of the stars varies depending on the point from which we observe them.
In terrestrial observation, quasars, which are bright stars that are too far away astronomically, are practically invisible. Unlike this, in a spacecraft in the middle of deep space the stars would be closer to make measurements and would show a greater parallax effect.
Also, the closer the moving craft is to the stars, the more evident its own motion will be over time. The change in the apparent position of the star in space due to actual motion relative to the ship is known as aberration.
Both parallax and aberration can provide data for space navigation. The parallax would give the real-time position of the spacecraft in 3D space and the aberration would give the speed of the spacecraft in relation to the movement of these stars.
For this method to work, the spacecraft should have a star chart of positions and stellar velocities already known and mapped from Earth using data from star chart missions, such as Gaia and Hipparcos.
The Bailer-Jones simulation
Therefore, according to Bailer-Jones, the spacecraft would operate on existing star charts, with data on the directions and expected speeds of the stars relative to it. Simulations of this idea positioned the spacecraft between 1 and 10 light years from Earth, a higher estimate than the distance our first attempts at interstellar travel will travel.
Keep in mind that the closest star to Earth (apart from the Sun) is Proxima Centauri, which is 4.2 light years away. If we want to travel to another solar system, we probably need to fly at a good fraction of the speed of light. Therefore, the simulation wants to investigate how that would affect navigation and if it would be possible.
To this day, we are still a long way from these investigations going from being simple simulations to something real. However, it seems that experts like Bailer-Jones are not giving up on someone fulfilling their dream of traveling aboard the Millennium Falcon.
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