Space is big-really big. And if you want to navigate our deep interstellar space well, Milky Way Galaxy, you will need some kind of reliable system. The new proposal tries to make this method as simple as possible. That is, it uses a pair of stars to provide a frame of reference for the galaxy.
Within our solar system, interplanetary spacecraft EarthBase system for navigation. When sending a radio signal to a spacecraft to respond, you can use the time delay of the response to calculate the distance. It is also possible to monitor a spacecraft in the sky, and by combining all the information (position in the sky and distance from the earth), it is possible to identify the position of the spacecraft in the solar system and provide that information to the spacecraft itself. I can.
gallery: Vision of interstellar navigation
You can also use Doppler shift Of those radio waves to estimate the speed at which spacecraft move away from Earth. By using dishes scattered around the globe, you can measure the delay of a spacecraft’s signal to reach one dish and another. Combining that data with location information, the spacecraft is completely 6-dimensionally locked. That is, 3D position and 3D velocity.
This method relies on a network of ground radar systems, all of which are in constant communication with the spacecraft. This technology works with spacecraft in the solar system and barely NASA twins. Voyager spacecraft..
However, interstellar missions require a new approach. You need to navigate autonomously. In principle, these spacecraft can use onboard systems such as watches and gyroscopes, but interstellar missions last for at least decades, and due to small errors and uncertainties in the onboard systems, they are definitely in their space. The ship is off course.
There is also an option to use PulsarA rotating object that appears to flicker or pulsate at regular intervals. Each pulsar has its own rotation period, so these objects act as reliable beacons for deep space missions. However, this only works in relatively small bubbles near the solar system. This is because the rotation period measurements can be contaminated by interstellar dust.
Second star from the right
Therefore, interstellar spacecraft need an easy and reliable way to estimate their position in the galaxy.New paper Recently posted to the preprint server arXiv.org Provides such a solution. In other words, it is the star itself.
This technique is based on a very old concept. parallaxWhen you poke your finger in front of your nose and close your eyes, your finger appears to wiggle. The change in apparent position arises from a new perspective when switching from eye to eye. If you do the same movement while looking at a distant object, the object will shake much less.
It was parallax that allowed scientists to first measure distance. PerformerAnd it is through parallax that a spacecraft wandering far away from the house can get its direction. Before launch, load the spacecraft with an accurate map of all known stars near the galaxy. Then, as the spacecraft moves away from the solar system, it measures the relative distance between multiple star pairs. As the spacecraft moves, stars closer to the spacecraft appear to move significantly, while distant stars remain relatively fixed.
By measuring multiple star pairs and comparing their measurements to the original Earth-based catalog, the spacecraft can figure out which stars are which stars and how far they are from them. Can be given an accurate 3D position within the galaxy.
Obtaining the speed of a spacecraft is a bit complicated and relies on the strange quirks of special relativity. Because of the finiteness of Speed of light, If you are moving fast enough, the object may appear to be in a different position than it really is. Specifically, the position of the object is displayed shifted in the direction of movement. This effect is called aberration and can be measured from the earth. As our planet orbits the Sun, the stars appear to slowly sway back and forth in the sky.
As long as the spacecraft is moving fast enough (and if you want the interstellar mission to last for decades instead of thousands), the onboard system will measure this anomaly. can do. By recording which star is from the expected position and how much, the spacecraft can calculate its 3D velocity.
Taking parallax measurements allows the spacecraft to recover full 6-dimensional coordinates within the galaxy. I know where it is and where it goes.
How accurate is this technique?According to the treatise, if the spacecraft can measure the position of exactly 20 stars with an accuracy of less than 1 second (1 second is 1/60 of a 1/1 arc, 1/60 degrees itself), then within the galaxy. Position with an accuracy of 3 Astronomical unit Keep (AU) and its speed within 2 kilometers / second (1.2 miles / second). One AU is equal to the average distance between the Earth and the Sun (about 93 million miles (150 million km)), so 3 AU is about 279 million miles (450 million km). It sounds a lot, but it’s peanuts compared to the thousands of AU between the stars.
We have the exact location of more than 20 stars, so we can load a catalog of hundreds of millions of stars for use on that voyage on a spacecraft. Each of the spacecraft’s measurements helps to pinpoint its location more accurately.
All you need now is an interstellar probe.
Paul M. Satter Is an astrophysicist Ohio State University, many Ask an alien When”Space radio, “And” authorYour place in space“.” Satter contributed this article Space.com Expert Voices: Op-Ed & Insights..
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