BEIJING — Using China’s gigantic optical telescope, astronomers have discovered a record number of small compact galaxies outside the Milky Way where star formation is taking place at a rapid pace.

With the help of the Large Sky Area Multi-Object Fiber Spectroscopic Telescope (LAMOST), a team of researchers under the aegis of the National Astronomical Observatories of the Chinese Academy of Sciences has discovered 1,417 new compact galaxies, almost twice as many as previously known. The study was recently published in The Astrophysical Journal.

“This is the largest sample of new compact galaxies discovered at one time to date,” lead researcher Luo Ali said Tuesday, adding that the previous world observation record was just 800 members.

Apart from the sample number, the study of the universe has attracted wide media coverage as these newly discovered galaxies were named after vegetables and fruits, mainly based on their colors and shapes.

The discovery included 739 Green Pea galaxies, 270 Blueberry galaxies and 388 Purple Grape galaxies, Luo said.

“The Green Pea galaxy, for example, looked round and dense like beans, and appeared green on pseudocolor images, so they were named ‘Green Pea galaxies’,” Luo added.

About 1.5 billion to 5 billion light-years away, the Green Pea galaxies are less than a tenth the size and less than a hundredth the mass of the Milky Way, but they have a very high star formation rate, which is about 10 times that of the Milky Way.

“Such an impressive star formation rate was common in the early universe but rare nowadays,” said Liu Siqi, a member of the research team.

Liu believes that the research on Green Pea galaxies will provide a new perspective for understanding the formation and evolution of galaxies in the early universe.

Blueberry galaxies are closest to Earth and more compact than the Green Pea galaxies, while the Purple Grape galaxies are somewhere between the other two galaxies or more distant than the Green Pea galaxies.

Some Chinese media outlets dubbed the discovery an “extragalactic fruit and vegetable garden.” But researchers say these bright-colored galaxies are small and faint, making observations very difficult and constrained.

Luo noted that these new compact galaxies range in mass from about 310,000 to 10 billion solar masses, with the farthest one being about 9 billion light-years away.

Known as Guo Shoujing Telescope in China, LAMOST went into operation in 2008 to gather high-quality spectra, an important collection of data that helps astronomers concerned with celestial bodies’ chemical composition, density, atmosphere and magnetism. It has helped discover hitherto the most massive stellar black hole and the most lithium-rich giant star ever known.

As LAMOST extragalactic survey continues, more compact galaxies will be discovered, which will open more possibilities for understanding the formation and evolution of galaxies in the early universe, Luo said.

作者 admin_philip