My first Magazine Sky & Telescope - 04.2019 | Page 37

The allure of the closest
star system to ours infects
astronomers and venture
capitalists alike.
I
n 1831, an outbreak of scarlet fever
at the Cape of Good Hope killed the
director of the Royal Observatory.
Thomas Henderson, a promising Scot-
tish astronomer, was asked to come and
replace him. Henderson was under-
standably hesitant to leave the safety of
his home in Edinburgh for the dangers
of the remote British colony, but he ulti-
mately decided it would be good for his
career and took the job.
Henderson arrived in March 1832 at
what he described as a “dismal swamp”
and quickly started mapping the posi-
The Alpha Centauri
binary forms the
third brightest star in
the entire sky, only
surpassed by Sirius
and Canopus.
tions of hundreds of southern stars. In
his 13-month stay (he resigned after
a request for additional funding was
denied) he made a series of measure-
ments that would grant him a place in
the pantheon of astronomy. These were
precise recordings of the position of
Alpha Centauri, a binary that forms the
third brightest star in the entire sky,
only surpassed by Sirius and Canopus.
He later used the observations to mea-
sure the binary’s parallax, the apparent
shift in its position in the sky caused by
Earth’s yearly motion around the Sun
(S&T: Mar. 2019, p. 26). The parallax
revealed that this bright double star
was the closest stellar neighbor to the
solar system.
t THE CENTAUR’S HOOF The Alpha Centauri
system hovers above La Silla Observatory in
northern Chile.
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