Research prompts a rethink of Milky Way’s shape

Galaxy’s structure is much more ordinary and not as unique as earlier thought, study suggests

The conventional view of the Milky Way galaxy as having four arms may be incorrect, according to a new study which attempts to discover the true shape of our abode in the universe.

As telescope technology improved, researchers discovered that the vast majority of galaxies exist in one of three main shapes – spiral, irregular and elliptical – with most having two main arms with spirals splitting into smaller arms.

For decades, astronomers have understood the Milky Way galaxy as having a spiral shape with a central bulge and four main spiraling arms with smaller branches – a structure thought to be rare.

However, in spite of much work, the overall spiral structure morphology of the Milky Way has remained unclear, said scientists, including those from the Chinese Academy of Sciences.

The new study, published in The Astrophysical Journal, suggests it is more likely that the galaxy’s shape has only two main arms.

Researchers analysed data from a new generation of space instruments to accurately measure the distances to stars that emit microwaves.

They used the data they obtained to map 200 such stars in the Milky Way.

Scientists also used data from the European Space Agency’s Gaia space observatory that is used to map the location of stars in relation to Earth and to each other.

When scientists fit the arrangement of the stars from their latest analysis onto a spiral, they found the Milky Way may not have the shape that it was previously thought to have.

Researchers say based on their more accurate map of the Milky Way that

The galaxy is likely a “barred spiral” and the other more distant arms have split to form minor arms, said scientists, based on their map of the Milky Way,

These shorter arms seem more distant, irregular and disconnected from the main structure.

The new findings point to the galaxy having multiple-arm morphology and a two-arm symmetry, with the Perseus and Norma constellations in the innards, extending to the outer regions where there are several long, irregular arms, including the Centaurus, Sagittarius and Carina constellations.

The overall findings hint that the Milky Way’s structure may not be as unique as previously thought.

Finding whether the Norma and Perseus constellation arms begin at the ends of the central bar in future studies may help decode the shape further, scientists said.

“The morphology of the Milky Way is similar to those of most multiple-arm galaxies in the universe,” they wrote in the study.