Interpreting the universe! This "powerful" astronomical telescope sets a new world record!

Produced by: Science Popularization China

Author: Crossing the Stars Team

Producer: China Science Expo

When it comes to observing the universe, we cannot do without the help of astronomical telescopes. When it comes to astronomical telescopes, we have to mention this "astronomical observation artifact" - LAMOST. Recently, LAMOST has been active in everyone's vision because it broke the spectral number of 20 million for the first time.

So what exactly is LAMOST, this "powerful" astronomical telescope? How does it play the role of a cosmic "star scout"?

The field of view is large and the aperture is large

The Guo Shoujing Telescope (LAMOST, Large Sky Area Multi-Object Fiber Spectroscopic Telescope) is a new type of telescope with a large field of view and a large aperture.

As a major national scientific project, LAMOST started construction in September 2001 and was completed in October 2008. In April 2009, it passed the process appraisal organized by the Chinese Academy of Sciences and the acceptance of four professional groups including construction, finance, equipment and archives. On June 4, 2009, it successfully passed the national acceptance hosted by the National Development and Reform Commission.

The completion of LAMOST has broken through the difficult problem of achieving both a large field of view and a large aperture in astronomical telescopes. It has become the world's largest large-field telescope and another milestone in the development of optical telescopes in my country. It has significantly improved my country's independent innovation capabilities in the field of large-field multi-object fiber-optic spectroscopy equipment.

Ten million spectra doubled again in ten years, the highest in the world

Over the past decade, LAMOST has opened up and led the way for large-scale international spectral surveys, becoming a classic among international large optical telescopes.

In 2009, when accepting the project, the acceptance experts pointed out that LAMOST is a model of independent innovation in China's science and technology field. It will increase the number of celestial spectra observed by mankind by an order of magnitude to tens of millions, making China an international leader in this field.

In 2019, LAMOST became the world's first sky survey project to publish a total of over 10 million spectra.

In four years, the number of spectra acquired by LAMOST has doubled again. On March 30, 2023, the National Astronomical Observatory of the Chinese Academy of Sciences released the LAMOST DR10 (v1.0) dataset to domestic astronomers and international collaborators. The dataset contains a total of more than 22.29 million spectra, which is 2.9 times the total number of spectra released by other survey telescopes in the world. LAMOST has become the world's first survey project to release more than 20 million spectra.

Interpreting the universe and upgrading to seize the commanding heights of science

LAMOST has helped astronomers around the world achieve a number of major breakthroughs that have set new records and increased the magnitude of their research in the structure and formation and evolution of the Milky Way, the exploration of stellar physics, and the search for special and compact celestial bodies.

1. Drawing a space-time “portrait” of the Milky Way

Since ancient times, this Milky Way stretching across the sky has aroused people's endless imagination and courageous exploration. LAMOST's 20 million spectral data have laid the foundation for the "digital Milky Way", which has irreplaceable scientific significance for drawing the space-time "portrait" of the Milky Way. From "height and weight" to "appearance and figure" to "growth history", LAMOST helps astronomers depict the full picture of the Milky Way in multiple dimensions.

In 2021, astronomers used LAMOST and Gaia data to reveal that the substructures (clusters of stars) in the anti-Galactic center direction of the Milky Way originated from the outer disk of the Milky Way, rather than the remains of dwarf galaxies accreted by the Milky Way. This conclusion ended the long-standing controversy in the astronomical community about the origin of the anti-Galactic center substructures.

On March 24, 2022, the cover article of Nature published a research result of Chinese and foreign astronomers. Using the sky survey data of LAMOST and the European Space Agency's Gaia satellite, the researchers obtained the most accurate age information of 250,000 stars in the Milky Way so far, and clearly restored the growth history of the Milky Way in its infancy and adolescence from the timeline.

Schematic diagram of the early formation and evolution of the Milky Way: the Big Bang 13.8 billion years ago, the thick disk of the Milky Way began to form 13 billion years ago, the Milky Way halo formed 11 billion years ago, and the thin disk of the Milky Way has formed from 8 billion years ago to the present

(Photo source: Yu Jingchuan)

In 2022, researchers used LAMOST data to accurately measure the mass of the Milky Way to be about 550 billion times the mass of the sun, which is nearly half the average value measured by other international teams (about 1 trillion times the mass of the sun) and nearly double the accuracy. This means that the "body" of the Milky Way may be half as "slim" as traditionally believed.

LAMOST has redrawn the space-time "portrait" of the Milky Way with its new scientific discoveries.

LAMOST and the Galaxy

(Image source: National Astronomical Observatory)

2. Unraveling the Mystery of the Stellar World

Stars are the most important probes for studying astrophysics, and tracing the stories of stars throughout their life has always been a hot topic for astronomers. In recent years, LAMOST has also made great achievements in the field of stellar physics.

In early 2023, researchers published an important result using LAMOST data in Nature: for the first time, a very important basic theory in astrophysics - the "stellar initial mass function" was observed to have changed significantly with the evolutionary history and environment of the Milky Way.

3. Promoting new discoveries in the “Black Hole Hunter Program”

In 2022, the international academic journal Nature Astronomy published an important discovery of the LAMOST Black Hole Hunter Program. Based on the LAMOST time-domain survey data, the research team discovered a quiescent neutron star about 1037 light-years from Earth. This is another important achievement of the LAMOST Black Hole Hunter Program in the field of compact object searches, following the identification of a quiescent stellar-mass black hole in 2019.

Schematic diagram of the discovery of a quiet neutron star by LAMOST

(Photo source: Yu Jingchuan)

The advantage of LAMOST's large-scale sky survey allows astronomers to use radial velocity monitoring methods to discover quiet black holes, neutron stars and other compact objects, breaking the observational limitations of relying on X-rays to search for compact objects.

4. Searching for rare “stars” in the sea of ​​stars

Searching for rare celestial bodies is a very valuable task, but it is extremely difficult because of their rarity. Without a large sample of data "ocean", it is almost impossible to achieve a "needle in a haystack" search. In recent years, LAMOST has been surfing the sea of ​​stars, with precious treasures everywhere. Batches of special celestial bodies continue to appear, becoming precious "codes" to decipher the mysteries of the universe.

In 2022, leveraging the advantages of LAMOST's sky survey, astronomers discovered nine rare super-lithium-rich dwarfs at one time. One of them has a lithium content 31 times that of the sun, setting a new record for the lithium content of this type of stars.

In 2022, a Chinese research team discovered 734 extremely cold dwarfs in the LAMOST spectral data, which is currently the largest sample of extremely cold dwarfs with uniform spectral data.

5. Capturing information from the distant universe

Quasars are the brightest, continuously luminous objects in the universe and are important probes for studying the distant universe. To date, the total number of quasars confirmed by LAMOST has reached 56,176, of which 24,127 were discovered for the first time by LAMOST.

In 2022, astronomers discovered 1,547 compact galaxies in the LAMOST massive spectrum, of which 1,417 were newly discovered, including a large number of green pea galaxies, blueberry galaxies and purple grape galaxies.

The farthest of these galaxies is about 9 billion light years away from Earth. This is the largest number of compact galaxies ever discovered at one time. Before this, the largest sample of compact galaxies with spectral information only had about 800 members. These compact galaxies provide a new perspective for understanding the formation and evolution of galaxies in the early universe.

From left to right: Green Pea Galaxy, Blueberry Galaxy, and Purple Grape Galaxy

(Image source: National Astronomical Observatory)

Ten years of sky surveys covering the galaxy: Future prospects for LAMOST

The second phase of the spectral survey will end in June 2023, and the third phase of the spectral survey is scheduled to begin in September 2023.

A new journey, a new goal, and a new start. LAMOST will continue to watch the starry sky, record and witness the development of my country's first major astronomical scientific and technological infrastructure.

Editor: Guo Yaxin