It is safe to say that the universe is unimaginably vast. For example, the comoving distance between Earth to the edge of the observable universe is about 46.5 billion light-years in any direction. In other words, it would take a spaceship, traveling at the speed of light, which is about 186,000 miles per second, at least 46.5 billion years to reach the universe’s edge.
The distances between stars also frequently exceed many light-years, with distances so vast even a journey at the speed of light could prove impossible to make, at least for now.
Fortunately for humanity, which someday hopes to find another habitable planet orbiting a star much like the Sun, Earth is much closer to other stars than many realize. The planet’s nearest stellar neighbor with potentially habitable planets, Alpha Centauri, is in fact “only” 4.37 light-years away from Earth, and it’s also exactly like the Sun.
Alpha Centauri appears from Earth to alternate in color between white and yellow. However, like the Sun, it’s a spectral type G2 V or yellow star, though there’s more to the star than meets the eye.
How Many Alpha Centauri Stars Exist?
When referring to Earth’s closest stellar neighbor as a star, it’s important to note that there are two stars known as “Alpha Centauri.” They are named Alpha Centauri A and Alpha Centauri B, though only A is yellow like the Sun. Alpha Centauri B is orange with a spectral type of K1. This duo’s orbits are relatively close to each other, as interstellar distances go. They form a binary or pair of stars that appear as one to the naked eye.
A third Centauri, Proxima, may be gravitationally bound to Centauri A and Centauri B. Proxima Centauri, however, is a dim, red dwarf star with a spectral type of M5. It is much fainter, lower in temperature, and smaller than the Sun, making it unsuitable for humanity’s purposes. Proxima shines so faintly astronomers had difficulty finding it, even though it lies only 4.22 light-years distant from Earth.
What Does Alpha Centauri’s Color Denote?
Alpha Centauri A’s yellow color means that it’s like Earth’s Sun in temperature. At 5,800 Kelvin or nearly 10,000 F, Centauri A may seem hot. Keep in mind, though, that any planets orbiting it will be much cooler because they’re relatively far away. Like Earth, Centauri’s planets would probably be far enough away that the heat from the star may not be a deal-breaker. Life on Earth also forms under a yellow sun.
Because it’s yellow, the Sun offers the ideal combination of color and temperature necessary for life to take hold and expand. Without a star-like Alpha Centauri A providing the right color and temperature range, it could be challenging, if not impossible, for carbon-based life on one of its planets to either form or sustain itself. A planet orbiting Centauri A at just the right distance, then, would benefit from the spectral color and heat given off by this star.
What Makes Alpha Centauri Promising?
Stars must pass five tests to be promising candidates for hosting Earth-like life. Alpha Centauri A appears to meet all five of those tests successfully, and here’s why:
- It’s both mature and stable, meaning it’s a main-sequence star that fuses hydrogen into helium at its core. Such a particular fusion of hydrogen and helium allows Centauri A to give off the right amount of light and heat.
- Because it has an abundance of hydrogen, Alpha Centauri A will also live a long time, giving life a good chance to arise and then take hold. Older and much cooler and younger and much hotter stars are too inhospitable for life to thrive.
- Alpha Centauri A’s stability is also crucial. Because it’s so stable, its brightness won’t increase or decrease enough to freeze or fry any life that develops or arrives on the right planet in that solar system.
Is Alpha Centauri’s Age Important?
Alpha Centauri A has already been around for 5 to 6 billion years and will live billions of years more. There may be a chance that life could exist somewhere in that solar system. But what if life doesn’t already exist around Alpha Centauri A? The star’s rays are both nourishing and sustaining, and life could flourish there once it arrives.
Consider that stars like Centauri A possess enough heavy elements such as carbon, nitrogen, oxygen, and iron to allow rocky or terrestrial planets to form. Humans aren’t naturally adapted to live in space, except perhaps in large structures with artificial gravity environments.
Even with artificial gravity of some sort, though, people will still require terrestrial planets of the right mass and gravity to live comfortably and thrive and continue moving throughout the galaxy. Other life forms humans bring along with them to Centauri A will also need the same life-sustaining Sun and its collection of terrestrial or rocky planets.
Does Alpha Centauri A Have Planets?
So far, scientists have discovered thousands of planets orbiting a variety of stars. However, most of the ones found by astronomers and other scientists are many light-years away from Earth.
They are likely out of reach of humanity for now. At present, scientists also can’t confirm that Alpha Centauri A even has planets. However, observers will soon turn many more telescopes on the binary star system and closely examine it.
Once such scrutiny occurs, scientists should eventually detect any planets orbiting one or both suns. Scientists also argue that life conditions around Alpha Centauri A are about the same or even better than around Earth’s Sun.
Lower levels of dangerous X-ray radiation from Centauri A exist around that solar system’s “habitable zone” for planets, which improves the chances of life appearing.
However, Alpha Centauri is a binary star system. Any planets near either of the two stars, such as one possibly orbiting Centauri A, must not be too far away from their star, or their orbits would be fatally affected by the other nearby Sun.
Can Humanity Reach Alpha Centauri?
Alpha Centauri star system does lie close to Earth and its Sun, at least compared to the Milky Way Galaxy and the universe. However, 4.37 light-years, or 25 trillion miles, is still a massive distance away from this planet.
Even our fastest non-human-crewed spacecraft, the Parker Solar Probe, is traveling only at a relatively slow 153,454 miles per hour.
The fastest a human-crewed spacecraft has traveled through space was Apollo 10 and its three astronauts as they returned from the Moon, and it only hit a peak of 24,790 mph.
Still, maybe humans will soon create a spacecraft capable of traveling at an impressive 4.5% the speed of light, or 8,333 miles per second.
However, those space travelers would still need at least 100 years to reach Alpha Centauri A and B and any planets orbiting either star.