# 2079: Alpha Centauri

 Alpha Centauri Title text: And let's be honest, it's more like two and a half stars. Proxima is barely a star and barely bound to the system.

## Explanation

 This explanation may be incomplete or incorrect: Created by an INTERGALACTIC YELPER. Please mention here why this explanation isn't complete. Do NOT delete this tag too soon.If you can address this issue, please edit the page! Thanks.
Alpha Centauri is the closest star system to our solar system, being 4.37 light-years away. As such, there are numerous ongoing plans and projects to journey to, and explore the star system. Ponytail announces such a project using a Voyager-like probe.

However, the offscreen person is against her idea, saying "Alpha Centauri sucks". The comic makes a joke on rating systems, by saying it only has 3 stars. Alpha Centauri indeed only has 3 stars, Alpha Centauri A, Alpha Centauri B, and Proxima Centauri.

Many rating systems, such as Yelp, use a star rating system, with more stars indicating higher quality. 3 stars out of 5 stars would be a "middling" rating, equating to a C grade, and 3 stars out of 10 stars would be very poor quality.

The title text refers to Proxima Centauri, a red dwarf, which is a type of low-mass star. According to the offscreen person, this barely qualifies it to be a star. Furthermore, Proxima Centauri is nearly 13,000 AU (0.21 light years) away from the other 2 stars in the system, so it was long unknown whether Proxima Centauri was gravitationally bound to the Alpha Centauri star system or not.

### Calculations

All numbers are rounded 4.367 light years / 35 years = 0.12477142857142857142857142857143 light years/year 0.12477142857142857142857142857143 light years/year = 733484485848 miles/year 733484485848 miles/year = 83,731,105 Miles/hour = 134,752,151 Kilometers/hour According to space.com the fastest spacecraft ever will be the Parker Solar Probe which will reach 430,000 mph (692,000 km/h) as it reaches its closest point orbiting the sun. This is just over half of the needed speed of the Alpha Centauri vehicle proposed in the comic. The Voyager 1 spacecraft, launched in 1977, is currently traveling at about 38,000 mph (61,000 km/h).

## Transcript

[Ponytail stands on a podium giving a presentation in front of a slide with an image of a Voyager-like satellite.]
Ponytail: Our probe can reach Alpha Centauri in under 35 years.
Offscreen voice: We should go somewhere else. Alpha Centauri sucks.
Ponytail: Huh? It's the closest most convenient system!
Offscreen: Yeah, but I checked online and it only has three stars.

# Discussion

Possible concept projects he's referencing:
https://en.wikipedia.org/wiki/2069_Alpha_Centauri_mission or https://en.wikipedia.org/wiki/Breakthrough_Starshot
172.68.65.150 18:18, 30 November 2018 (UTC)

Breakthrough Starshot sounds relevent enough to mention in the article. In 2016 an earth-like planet was discovered orbiting Proxima Centauri, which is the closest star in the universe to our sun. Other destinations are considered for the project, but the plan is to visit this planet. Expected velocity is 37,300 km/s. Estimated departure date is 2036, arriving by 2066. Significant funding exists. But some of the technologies do not quite yet. (for those who don't want to click the link) 162.158.187.25 21:06, 30 November 2018 (UTC)

Alpha century does have 3 stars: Alpha Centauri A (also named Rigil Kentaurus[15]), Alpha Centauri B (also named Toliman), and a small and faint red dwarf (Class M), Alpha Centauri C (also named Proxima Centauri[15]) https://en.wikipedia.org/wiki/Alpha_Centauri
172.68.65.150 18:18, 30 November 2018 (UTC)
I don't know what the (voices off) is complaining about. We only have one star! So Alpha Centauti is an upgrade ;-) RIIW - Ponder it (talk) 18:44, 30 November 2018 (UTC)

But if your going to upgrade, go all the way at least. (Definitely not an excuse I use to buy better PC hardware)Linker (talk) 18:49, 30 November 2018 (UTC)

Check out figure 1 on page 3 of this 2016 study: http://www.ice.csic.es/personal/iribas/Proxima_b/pdf/Proxima_habitability_II.pdf showing how likely the researchers believe there to be oceans on Proxima b. They expect us to be able to determine what's true directly in 10 years when construction of larger telescopes is completed. Most other sources I found in my brief search are very careful to say that we do not know at all whether or not there is water on this nearby exoplanet. 162.158.186.108

I (on the basis of no astrophysicists training, just being a Civil Engineer) can't help wondering that of the three planets in the Sun's Goldilocks zone* that only one has... 1. a strong enough magnetic field to prevent the solar wind stripping off a light atmosphere, that prevents the water boiling and being blown away. 2. an abnormally big moon**. 3. proven plate tectonics. 4. macro life.

And so that 2 is crucial to 1 and 3 and 3 is crucial to 4 (including 1 of course)

So why we expect liquid water everywhere is a mystery to me.

YMMV and I reserve the right to be (proved) wrong

• apparently according to various things I have read over the decades
• some believe Mars had a bigger moon (magnetic field and oceans) before it's orbit decayed and it collided.

RIIW - Ponder it (talk) 19:43, 1 December 2018 (UTC)

Hmm: 4.367 light years / 35 years = 0.12477 light years/year

The above math assumes a constant speed, and requires a speed of ~0.0001c.

Wouldn't the assumed constant speed be about 12% of light-speed instead? 0.12477 light-years/year (cancel the years) = 0.12477 c.

While conventional rockets could not carry enough fuel for an accelerating trip, what about ion propulsion? Low mass ejected at really high speeds for a long time could accelerate the space craft over the entire distance, with a turn-around halfway. 0.0625 g has been achieved by modern ion thrusters. The question is whether you could still carry enough propellant for 35 years. Nutster (talk) 10:54, 2 December 2018 (UTC)

Ion engines usually use solar panels for their energy. However, in interstellar space, there is very little light so solar panels are not very efficient. They would first have to come up with an alternative power source to circumvent that problem. 162.158.92.34 12:42, 3 December 2018 (UTC)
I was thinking nuclear power, like what is powering all the probes to the outer planets. This would just be really out-there planets. I would need to compare the power output of, for example, Cassini's reactor to the power needs of the ion drive (as well the needs of the rest of the system during the trip) to see how well that could work. Nutster (talk) 14:06, 3 December 2018 (UTC)

Little do they realize, it's 3 Michelin stars. 172.69.210.52 15:46, 2 December 2018 (UTC)

Not sure if I am the only one wanting to know how long it would take now and add it to the article; Distance to Alpha Centauri system = 4.367ly / fastest current speed 39,897km/h = 1.041 billion hours = 118757 years --162.158.91.59 12:35, 4 December 2018 (UTC)

How is the rate of acceleration determined in the calculations above? Why not decrease it a bit and let it take longer time but save energy?