# What is the distance to the closest star similar to our Sun? [closed]

My question was inspired by this nice question. But, I recall the phenomenon of strange objects appearing on our sky, and then moving away with a velocity that seems not yet attainable by manmade machines. Was this phenomenon understood? It doesn't seem so.

Or, let me ask otherwise, is it known what is the star closest to our Sun and similar to it in mass, age, and luminosity? What is the distance to it?

• Would Skeptics be a better home for this question (v1)? – Qmechanic Feb 16 '15 at 22:21
• @Qmechanic why should be a better home? What has my question about the closest similar star to do with skeptics? – Sofia Feb 16 '15 at 22:45
• Well, we don't yet know what properties of a star "permits" a planet like the Earth. So I'll take a guess at Proxima Cen, since I would not be surprised if any star could host a small rocky planet. You also don't specify whether chemical composition similarity is a requirement. – ProfRob Feb 17 '15 at 0:23
• No. Not at all! That is why "solar twin" projects are difficult. They try to find stars that have the same mass and the same chemical composition of the Sun (and a similar age, though this is hard to determine accurately). Stars are born with different chemical compositions. – ProfRob Feb 17 '15 at 0:30
• Even the very first population III stars contained He. And all stars born since are born with a fraction of "metals". Where did you think the iron, calcium, sodium etc came from in the Sun? They are not made there. Or how did you think the Sun could have formed just from H, but all the planets contain heavier elements? – ProfRob Feb 17 '15 at 0:46

Or, let me ask otherwise, is it known what is the star closest to our Sun and similar to it in mass, age, and luminosity? What is the distance to it?

I can answer this part, not the UFO part.

Alpha Centauri A and B, the closest stars to the Sun after Proxima Centauri, are the closest Sun-like stars. A is a G2 star, just like our Sun; B is a K1 V star - a bit cooler, but still similar.

Here are some comparisons:

Mass

Sun - $1 \text{ M}_{\odot}$; A - $1.1 \text{ M}_{\odot}$, B - $0.9 \text{ M}_{\odot}$

Luminosity

Sun - $1 \text{ L}_{\odot}$; A - $1.5 \text{ L}_{\odot}$, B - $0.5 \text{ L}_{\odot}$

Photosphere temperature

Sun - 5778 K; A - 5790 K, B - 5260 K

Those numbers are really, really similar. And the system is only 4.37 light-years away.

If you want a really good solar analog, though, you have to go a bit further. Epsilon Eridani is your best option. It's 10.5 light-year away - a lot further than Alpha Centauri - and it's a K2V star; it's actually not a lot like the Sun. It appears to have an exoplanet, though.

Of course, there is some discussion of an exoplanet around Alpha Centauri B, too, but the claims have not been fully substantiated. The reason that the Alpha Centauri system isn't the best for life is that it's a binary star system - which we're clearly not in! Either A or B by itself would be a good starting point for a solar system; together, they aren't.

Even more exciting than Epsilon Eridani is Tau Ceti, a G-type star which may have up to five exoplanets and perhaps even a few in the habitable zone. It's 12 light-years away and has a huge debris disk around it, which could be an issue for life. But still, it's not too bad.

• Very interesting. Then, reaching them, is only matter of spaceships' velocities, and of having intermediate stations, as the flight to them takes long time. – Sofia Feb 16 '15 at 23:07
• @Sofia Exactly. – HDE 226868 Feb 16 '15 at 23:08
• I also understand that traveling at high velocity, the distance, from the point of view of the spaceship's voyagers, becomes shorter. In short, less years to travel. Still, high velocities need huge resources of energies, and also it's ridiculous to think that the human life is enough for such a travel. – Sofia Feb 16 '15 at 23:16
• @Sofia That's true. – HDE 226868 Feb 16 '15 at 23:18