It is one of the most important stars in the sky. This is partly because, by coincidence, it is surrounded by a dazzling
reflection nebula. Pulsating
RS Puppis, the brightest star in the image center, is some ten times more massive than our Sun and on average 15,000 times more luminous. In fact,
RS Pup is a Cepheid type
variable star, a class of stars whose
brightness is used to estimate distances to nearby galaxies as one of the first steps in establishing the
cosmic distance scale.
As RS Pup pulsates over a period of about 40 days, its regular changes in brightness are also seen along the nebula delayed in time, effectively
a light echo. Using measurements of the time delay and angular size of the nebula, the known
speed of light allows astronomers to geometrically determine the distance to
RS Pup to be 6,500 light-years, with a remarkably small error of plus or minus 90 light-years. An impressive achievement for stellar astronomy, the
echo-measured distance also more accurately establishes the true brightness of
RS Pup, and by extension other Cepheid stars, improving the knowledge
of distances to
galaxies beyond the Milky Way. The
above image was taken by the
Hubble Space Telescope and digitally processed by a volunteer.
Evrim Ağacı
