Relying on the massive spectral data of the Guo Shoujing Telescope (LAMOST), researchers from the National Astronomical Observatory of the Chinese Academy of Sciences and other units have newly discovered 1417 compact galaxies, including 739 green pea galaxies, 270 blueberry galaxies and 388 purple grape galaxies. The related research results were published online in The Astrophysical Journal.
“This is the research work with the largest number of newly discovered compact galaxies so far. There are only 800 compact galaxies in total that have been observed by other telescopes and confirmed by foreign scientists and published relevant research results. These galaxies are small, The brightness is dark and the observation is difficult.” Luo Ali, a researcher at the National Astronomical Observatory of the Chinese Academy of Sciences, emphasized in an interview with a reporter from Science and Technology Daily recently.
Some people may wonder why these newly discovered dense galaxies are named after vegetables and fruits?
In this regard, Roali explained: “In the images generated by the observation data, these galaxies show different colors and shapes, so astronomers use the more common fruits and vegetables in life according to their colors and shapes. Name it. For example, the Green Pea galaxy appears green on the image, is extremely dense, and looks round, like a bean.”
The researchers used LAMOST spectral data to systematically study the star formation rate, metallicity, and environment of these newly discovered compact galaxies.
“We found that these dense galaxies have higher star formation rates and lower metallicity. While normal galaxies tend to be in the environment of galaxy clusters, these dense galaxies are more distant from each other and in a more discrete cosmic environment. .” Roari said.
The discovery of the Green Pea galaxy came from the “Galaxy Zoo” program that involved astronomy enthusiasts. In classifying the different galaxies observed by the Sloan Digital Sky Survey (SDSS) by shape, amateur astronomers found 251 extremely special samples that are difficult to classify as known galaxy types. “Later, these samples were named the Green Pea Galaxy,” Roari explained.
The Green Pea galaxy has a low metallicity, a high star formation rate, and its mass can double in a few hundred million years. About 1.5 billion to 5 billion light-years away, they are less than one-tenth the size of the Milky Way and less than one-hundredth the mass of the Milky Way, but they are giving birth to stars at 10 times the rate of the Milky Way.
“Such astonishing star formation rates are very common in galaxies in the early universe, but are rare today,” said Liu Siqi, a doctoral student at the National Astronomical Observatory of the Chinese Academy of Sciences.
Typical of the compact galaxies are the blueberry galaxy, which appears blue in the image, and the purple grape galaxy, which appears purple.
Liu Siqi introduced that the Blueberry Galaxy is more compact than the Green Pea Galaxy, less than one-third of the volume of the Milky Way and less than one-ten thousandth of the mass of the Milky Way; the Blueberry Galaxy is a denser galaxy closer to us, while the Purple Grape Galaxy and ours The distance is between the Green Pea Galaxy and the Blueberry Galaxy, or farther than the Green Pea Galaxy.
“The masses of these newly discovered compact galaxies range from about 310,000 to 10 billion times the mass of the sun. Among them, the most distant galaxy from Earth is about 9 billion light-years away.” Roali added.
As the LAMOST survey continues, more green pea galaxies, blueberry galaxies and purple grape galaxies will be discovered in the future, which will open the door to revealing how stars formed in the early universe and understanding how many galaxies, including the Milky Way, evolved new window.
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