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Editor’s Note: Proxima Centauri is the nearest star to Earth. It’s part of the triple Alpha Centauri star system, visible as a single star from very southerly latitudes in the Northern Hemisphere and weightier seen from the Southern Hemisphere. Generally speaking, the three stars in the Alpha Centauri system are 4.4 light-years away. Proxima is the closest of the three at 4.2 light-years. But where is Proxima Centauri?
Where is Proxima Centauri?
The diagram whilom shows you where Alpha Centauri is with respect to other nearby stars. Included are stars within 12 light-years from the sun. The glows of light representing the stars are millions of times larger than the stars themselves, which would be microscopically small on this scale.
The grid serves to show Earth’s equatorial plane – the plane of our celestial equator – and moreover the scale. Note that the lines are four light-years apart. The slightly thicker line is the vernal equinox direction (the Earth-sun direction in space, virtually every March 20).
Imaginary stalks from the equatorial plane to the stars show how far north or south they are. I’ve cropped the picture so that some of the stars are off the top or bottom. But they are obscure stars you might not have heard of, with designations such as Lalande 21185, Luyten 726-8 and DX Cancri. Most stars, including most of those near to us, are smaller than our sun: red dwarfs.
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Proxima, in context
The exceptions near to us are Sirius, Procyon and Alpha Centauri.
The Alpha Centauri system – which includes the star Proxima – is the 3rd-brightest star in our sky. That is, it’s 3rd-brightest as seen from our place in space, and not counting our sun. Like the 1st- and 2nd-brightest stars – Sirius and Canopus – it is a southern star. Indeed it’s much farther south on our sky’s dome than either of those, which is why it has no traditional name in our culture (except a rather faux-traditional one, Rigil Kentaurus).
Notice the stalk to Alpha Centauri on the space diagram above. It shows it at a steep southward wile from our sun. This wile (its declination -61°) ways it doesn’t peep whilom the horizon until you go lanugo to the latitude of northern Florida.
To see it properly, you might go south of Earth’s equator.
Want to know increasingly well-nigh Proxima? Check out the video below:
More well-nigh Alpha Centauri
In a telescope, Alpha Centauri appears as a double star. Yes, it’s really triple, but Proxima is tiny and not easy to see. The other two stars in the Alpha Centauri system subsume one of the widest and easiest to “split” double stars in our sky. Here is part of my diagram of the pair with which I used to fill a space in Astronomical Calendar 2016:
Again, the symbols for the stars are vastly larger than the persons of the stars would be. It isn’t really that the B star revolves virtually the A one: they both revolve virtually their worldwide part-way of gravity.
You can see that this year of the diagram, 2016, is the year when B appeared closest to A, though in the true (untilted) orbit it will reach periastron in 2035. The undecorous lines are one second of arc apart; that’s the unveiled size of a tennis wittiness 10 miles away.
Alpha Centauri A is a star much like the sun, slightly larger and of well-nigh the same 4.6-billion-year age or slightly older. Alpha Centauri B is slightly smaller and cooler. In their elliptical orbits virtually their worldwide part-way of gravity, they range from well-nigh 11 astronomical units (sun-Earth distances) untied when closest, to 36 when uttermost apart. In other words, they range from something like the sun-Saturn to something like the sun-Pluto distance.
Proxima Centauri again
And the loftiness of the Alpha Centauri system from us is only 4.4 light-years: nearer than all other stars … except for one, Proxima, discovered in 1915 (by Robert Jones in South Africa).
Proxima is one of those numerous dwarfs whose surfaces are reddish, meaning potation and dimmer. Only well-nigh 1/7 as wide as the sun, and at a magnitude (brightness) of 11, it is well-nigh 100 times too dim to be seen with the unaided eye. Proxima is increasingly than two degrees yonder from the Alpha Centauri pair; on observatory photographs, there are thousands of preliminaries stars in between.
Yet studies of it found that it is only 4.24 light-years yonder from us, closer than the other two stars in the Alpha Centauri system.
Hence it is dubbed Proxima Centauri, with the word Proxima having the same root as the word proximity, meaning near.
The nearest stars not only have the largest parallax (apparent weedy shift as we go virtually the sun) but are liable to have large proper motion (travel wideness the starry preliminaries from year to year). Proxima is found to be still coming gradually toward us; it will be nearest, at only well-nigh three light-years, well-nigh 27,000 years into the future. And it is probably, though not quite certainly, gravitationally unseat to the Alpha Centauri pair 0.2 light-year yonder from it, in an enormous, slow orbit of something like 500,000 years. So it can be tabbed Alpha Centauri C.
Humbling distances
Yes, these are humiliating numbers, and I hesitate to crush you remoter with the reminder that a light-year is nearly 6,000,000,000,000 miles, and the loftiness wideness the Milky Way galaxy is something like 30,000 times greater than the loftiness to these our nearest neighbors in it.
Thus, plane if there is a Proximan with a telephone, and one day you receive a undeniability from her asking:
What is your name, how many legs do you have, and how many sexes are there in your world?
… It will be increasingly than four years surpassing she receives your reply and increasingly than eight surpassing you know what she thinks of it.
Bottom line: Diagram and subtitle from astronomer Guy Ottewell, showing the location in space of the Alpha Centauri system and, in particular, the star Proxima Centauri, the nearest star to Earth.