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Our galaxy's best and brightest

NASA / JPL-Caltech
The Peony nebula star was found in the crowded, dusty center of our Milky Way
galaxy, seen here in a false-color infrared view from NASA's Spitzer Space
Telescope. Click here for higher-resolution imagery from the Spitzer team.

Scientists using NASA's Spitzer Space Telescope have uncovered a star that could be a contender for our galaxy's brightest light - and they say there might be even brighter bulbs out there, shrouded in cosmic dust.

The Peony nebula star, heralded today in an image advisory from the Spitzer team, doesn't look all that bright to the naked eye. Sirius is still the undisputed local champion, based on what we can see in the night sky. But a big factor behind Sirius' apparent brightness is its relative proximity to Earth - a mere 8.7 light-years, or roughly 50 trillion miles.

If you were to put all the stars observed in the heavens on an equal footing distance-wise, the gold medal for brightness would go to Eta Carinae, which is more than 7,500 light-years away but is thought to shine 4.7 million times brighter than our sun.

Now consider the star recently spotted by Spitzer: It's a whopping 26,093 light-years away, in the Milky Way's crowded center. The Peony nebula star (so named because it's wrapped in a flowery-looking nebula) is so shrouded in dust that you might not be able to tell just how bright it shines even if you were up closer.

L. Oskinova / Potsdam U. / NASA / JPL-Caltech
The Peony Nebula star, highlighted by a white
circle in the inset photograph from NASA's
Spitzer Space Telescope, is considered the
second-brightest star in our galaxy. Click on
the image for a larger version.


Spitzer's infrared camera was able to pierce the clouds of dust and get a better fix on the star's luminosity. Infrared readings from the European Southern Observatory in Chile were also factored into researchers' calculations.

"Infrared astronomy opens extraordinary views into the environment of the central region of our galaxy," Potsdam University astronomer Lidia Oskinova explained in today's advisory. Oskinova is the principal investigator behind the research as well as the second author of a paper about the star, due for publication in the journal Astronomy and Astrophysics.

Oskinova and her colleagues estimate that the Peony nebula star shines 3.2 million times as brightly as the sun. That would merit a silver medal, based on current standings. And because there is some uncertainty built into the luminosity estimates for the Peony as well as for Eta Carinae, it's conceivable that the two stars are roughly equal in brightness.

Astronomers estimate that the star started out with a mass 150 to 200 times that of our sun. That would be around the theoretical limit for the mass of stars. If you go much heavier, the star would break up into a multiple-star system during formation, astronomers say.

The Peony nebula star is classified as a Wolf-Rayet star, with a diameter roughly 100 times that of our sun. If it were placed where our sun is, its outer layers would extend to about the orbit of Mercury, the Spitzer team said. Such stars shed an enormous amount of material over a relatively short lifetime of a few million years. Winds of stellar radiation drive this material outward at speeds of up to 1 million mph.

ESO
The blue variable star Eta Carinae is shrouded in
dust and gas in a view from the European Southern
Observatory's Very Large Telescope. Eta Carinae is
considered the Milky Way's most luminous star. Click
on the image for a larger version.


Like Eta Carinae, the Peony nebula star appears to be on the very brink of going supernova. That's the way it is with superstars: The brightest lights often burn out the fastest.

"When this star blows up, it will evaporate any planets orbiting stars in the vicinity," Oskinova said. "Farther out from the star, the explosion could actually trigger the birth of new stars."

And that's another thing about being the best and the brightest: There's always someone waiting in the wings who may be even better and brighter. "There are probably other stars just as bright, if not brighter, in our galaxy that remain hidden from view," Oskinova said.

Other authors of the study include Andreas Barniske and Wolf-Rainer Hamann, both of Potsdam University in Germany. For more cosmic views, check out our Space Gallery.