Proxima Centauri discovered on this date

Proxima Centauri and other nearby stars.
Our sun’s closest neighbors among the stars, including Proxima Centauri. Image via NASA PhotoJournal.

Discovery of Proxima Centauri announced in 1915

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 about 4.24 light-years away. Conversely, Alpha Centauri is 4.36 light-years away.

The 100-year-anniversary celebration

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, however, to see without optical aid. Also, Proxima Centauri has three confirmed planets. The planets are known as Proxima Centauri b, c and d. Indeed, these three exoplanets are the nearest planets to our solar system. By the way, Proxima b orbits inside the star’s habitable zone.

Dense star field with two bright stars and a tiny red circle around a dimmer one that only stands out a bit.
View larger. | The 2 bright stars here are Alpha and Beta Centauri. The red circle shows the location of Proxima. It is much dimmer than its companions. Therefore, it is more difficulte to see from Earth. But, at just over one parsec away, it is the closest star to our sun. Also, sitting in the southern constellation Centaurus the Centaur, it is most likely gravitationally bound to the bright star on the right: Alpha Centauri. Image via Skatebiker/ Wiki Commons/ CC Share Alike 3.0.

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.

October 12, 2022

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Deborah Byrd

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