Brightest Star in the Galaxy Has New Competition
A contender for the title of brightest star in our Milky Way galaxy has
been unearthed in the dusty metropolis of the galaxy's center.
Nicknamed the "Peony nebula star," the bright stellar bulb was revealed by
NASA's Spitzer Space Telescope and other ground-based telescopes. It blazes
with the light of an estimated 3.2 million suns.
The reigning "brightest star" champion is Eta Carina, with a whopping solar
wattage of 4.7 million suns. But according to astronomers, it's hard to pin
down an exact brightness, or luminosity, for these scorching stars, so they
could potentially shine with a similar amount of light.
"The Peony nebula star is a fascinating creature. It appears to be the
second-brightest star that we now know of in the galaxy, and it's located
deep into the galaxy's center," said Lidia Oskinova of Potsdam University in
Germany. "There are probably other stars just as bright if not brighter in our
galaxy that remain hidden from view." Oskinova is principal investigator for
the research and second author of a paper appearing in a future issue of the
journal Astronomy and Astrophysics.
Scientists already knew about the Peony nebula star, but because of its sheltered
location in the dusty central hub of our galaxy, its extreme luminosity was not
revealed until now. Spitzer's dust-piercing infrared eyes can see straight into
the heart of our galaxy, into regions impenetrable by visible light. Likewise,
infrared data from the European Southern Observatory's New Technology Telescope
in Chile were integral in calculating the Peony nebula star's luminosity.
"Infrared astronomy opens extraordinary views into the environment of the central
region of our galaxy," said Oskinova.
The brightest stars in the universe are also the biggest. Astronomers estimate
the Peony nebula star kicked off its life with a hefty mass of roughly 150 to 200
times that of our sun. Stars this massive are rare and puzzle astronomers because
they push the limits required for stars to form. Theory predicts that if a star
starts out too massive, it can't hold itself together and must break into a double
or multiple stars instead.
Not only is the Peony nebula star hefty, it also has a wide girth. It is a type of
giant blue star called a Wolf-Rayet star, with a diameter roughly 100 times that of
our sun. That means this star, if placed where our sun is, would extend out to about
the orbit of Mercury.
With so much mass, the star barely keeps itself together. It sheds an enormous amount
of stellar matter in the form of strong winds over its relatively short lifetime of a
few million years. This matter is pushed so hard by strong radiation from the star
that the winds speed up to about 1.6 million kilometers per hour (one million miles
per hour) in only a few hours.
Ultimately, the Peony nebula star will blow up in a fantastic explosion of cosmic
proportions called a supernova. In fact, Oskinova and her colleagues say that the
star is ripe for exploding soon, which in astronomical terms mean anytime from now
to millions of years from now.
"When this star blows up, it will evaporate any planets orbiting stars in the vicinity,"
said Oskinova. "Farther out from the star, the explosion could actually trigger the
birth of new stars."
In addition to the star itself, the astronomers noted a cloud of dust and gas, called
a nebula, surrounding the star. The team nicknamed this cloud the Peony nebula because
it resembles the ornate flower.
"The nebula was probably created from the spray of dust leaking off the massive Peony
nebula star," said Andreas Barniske of Potsdam University, lead author of the study.
Wolf-Rainer Hamann, also of Potsdam University, is another co-author of the paper and
the principal investigator of a Spitzer program enabling this research.
NASA's Jet Propulsion Laboratory, Pasadena, Calif., manages the Spitzer Space Telescope
mission for NASA's Science Mission Directorate, Washington. Science operations are
conducted at the Spitzer Science Center at the California Institute of Technology,
also in Pasadena. Caltech manages JPL for NASA. Spitzer's infrared spectrograph, which
was used to determine the luminosity of the Peony nebula star, was built by Cornell
University, Ithaca, N.Y. Its development was led by Jim Houck of Cornell. For more
information about Spitzer, visit http://www.spitzer.caltech.edu/spitzer
Media contact: Whitney Clavin 818-354-4673
Jet Propulsion Laboratory, Pasadena, Calif.