Milky Way has only 2, not 4 arms

Living right in the heart of the Milky Way, it's hard for us to imagine the true picture of our galaxy. For years, astronomers have drawn a lovely spiral galaxy with four long arms embracing the central core, like a mother's bracelet.

Even these four arms are named Norma, Scutum-Centaurus, Sagittarius and Perseus. They are the birthplace of stars.

The picture is beautiful, but not accurate!

"For years, humans have created a map of the whole galaxy just by studying a part of it, or using a single method , " Robert Benjamin, from the University of Wisconsin, who last week gave Milky Way's new portrait, says.

"Unfortunately, when the models are compared, they don't agree. It's almost like the blind fortune tellers see elephants."

Benjamin's research shows that the Milky Way has only two arms, with a horizontal bar in the center, like in many other galaxies.

Milky Way actually has only two arms.(Photo: Discovery)

He and his colleagues used more than 800,000 infrared images captured by the Spitzer Space Telescope to create a mosaic picture rotating 130 degrees above the sky and a degree above and below the central plane of the Milky Way. It holds more than 110 million stars.

When analyzing the density of stars, the group found that Sagittarius and Norma's arms lacked seriousness, only worth fuzzy arms. The Scutum-Centaurus has enough density and Perseus, embracing the outermost part of the galaxy, is lurking in the observation frame.

At a press conference, Benjamin said the two large arms seemed to connect very closely to the top and bottom of the horizontal bar.

Sagittarius and Norma, two fuzzy arms, are considered to contain gas and young star bags, while two large arms - Scutum-Centaurus and Perseus are dense with hot young stars and red giant stars older and colder.