This article has been reviewed according to Science X's editorial process and policies. Editors have highlighted the following attributes while ensuring the content's credibility: Welcome back to our series on Interstellar Travel, where we look at the many proposals made for sending missions to the stars since the dawn of the Space Age. In our first installment, we examined how Cold War-era developments in nuclear weapons and rockets paralleled advances in space exploration, resulting in proposals for nuclear rockets.
We then examined how the creation of thermonuclear weapons led to applications in fusion propulsion. Then we looked at how the discovery and creation of positrons and antiprotons fueled proposals for spacecraft driven by antimatter propulsion. In our fourth installment, we addressed the most practical options for sending missions to interstellar space, including solar sails, magnetic sails and directed-energy propulsion (DEP).
In our fifth installment, we'll examine the most exotic proposals ever made that could (in theory) enable interstellar spaceflight someday. As we explored in a previous article, a ship relying on conventional propulsion methods would take thousands of years. And while theoretical methods exist that could shorten transits to a few decades, they would be very expensive to build and require tremendous amounts of propellant.
Alas, there are always those long-shot proposals, the kind that straddle the line between science fiction and fact, that still give us hope. Among them are the warp drive, wormhole travel and using black holes to achieve velocities approaching the speed of light. As noted in our inaugural installment, there is no shortage of planets beyond the solar system (exoplanets) that are well worth exploring.
To date, scientists have confirmed the existence of 6,354 exoplanets in 4,756 star systems. In fact, that number has increased since this series began on July 31. At that time, the census was 6,333 confirmed exoplanets in 4,747 systems.
Doing the math, that means that 21 more exoplanets in nine star systems have been confirmed in less than a month. What's more, while "Earth-like" (rocky) planets are rare, with the total still at 222 confirmations, they are surprisingly abundant in our stellar neighborhood. In fact, within 50 light-years of Earth, there are 31 known terrestrial planets, 30 of which orbit low-mass, M-type red dwarf stars.
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