October 12, 1915. On this date, the Scottish-born astronomer Robert Innes, at the Union Observatory in Johannesburg, South Africa, announced the discovery of what we now know as the nearest star to our sun. That star is Proxima Centauri, one of three known stars in the Alpha Centauri system, with the other two stars being Alpha Centauri A and B. He announced his discovery in a paper dated October 12, 1915, titled A Faint Star of Large Proper Motion.
Formerly, before this announcement, astronomers believed that Alpha Centauri was the closest star to our solar system.
However, Proxima – a relatively small red dwarf star – is closer at a distance of about 4.24 light-years. Conversely, Alpha Centauri lies 4.36 light-years away.
By the way, SAASTA – the South African Agency for Science and Technology Advancement – celebrated Proxima’s centenary in 2015. And at its website, SAASTA explained:
Although Innes had thoroughly observed Alpha Centauri, with his vast experience and passion for observing double stars he suspected that Alpha Centauri might have a companion. Innes compared photographic plates taken five years apart and observed that a certain faint star had moved. He found that this movement was about the same as that of Alpha Centauri.
After further investigation, he concluded that it was closer to the sun than Alpha. In 1917 he proposed the new star should be called Proxima Centauri, proxima being the Latin word for ‘nearest.’
Proxima Centauri has 3 known exoplanets
Today, Proxima remains the closest star to Earth, but it is too dim to see without optical aid. Also, Proxima Centauri has three confirmed planets, known as Proxima Centauri b, c and d. So these three exoplanets are the nearest planets outside our solar system. Interestingly, Proxima b orbits inside the star’s habitable zone.
Bottom line: October 12, 1915, was the date of the publication of a paper announcing that the little star Proxima Centauri – in the Alpha Centauri system – is the nearest star to our sun.
Our Editor-in-Chief Deborah Byrd works to keep all the astronomy balls in the air between EarthSky's website, YouTube page and social media platforms. She's the primary editor of our popular daily newsletter and a frequent host of EarthSky livestreams. Deborah created the EarthSky radio series in 1991 and founded EarthSky.org in 1994. Prior to that, she had worked for the University of Texas McDonald Observatory since 1976, and created and produced their Star Date radio series. She has won a galaxy of awards from the broadcasting and science communities, including having an asteroid named 3505 Byrd in her honor. In 2020, she won the Education Prize from the American Astronomical Society, the largest organization of professional astronomers in North America. A science communicator and educator since 1976, Byrd believes in science as a force for good in the world and a vital tool for the 21st century. "Being an EarthSky editor is like hosting a big global party for cool nature-lovers," she says.
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