Seoul National University researchers have released the first observation video from the “7-Dimensional Telescope (English name: 7-Dimensional Telescope, abbreviation: 7DT)” for the first time.
The 7-dimensional telescope is a world-class multi-telescope system being built at the El Sauce Observatory in the Andes Mountains of Chile, led by Professor Lim Myung-shin’s team at Seoul National University. In October 2023, 50% of the construction of the 7D telescope was completed, and observational research using it is currently underway.
Recently, with the development of astronomical observation technology, it has become possible to observe the universe at any moment as if it were a video. Accordingly, gravitational wave events[1]supernova[2]A large number of newly discovered sudden astronomical objects or variable astronomical objects that change their brightness and color at any moment have been discovered.
In order to properly understand the characteristics of these sudden or variable celestial bodies, the spectrum is observed by dividing light into various colors.[4] Observation is essential. However, existing observation techniques only allow spectral observation of a very small number of celestial bodies (usually 1, up to 1,000) within the telescope’s field of view, making it difficult to quickly track the characteristics of numerous celestial bodies that change over time. .
To overcome these difficulties in existing research, Professor Lim Myung-shin’s research team developed a ‘7-dimensional telescope’ that can simultaneously obtain spectra for all 60 million pixels in the telescope’s field of view. This is the first attempt in the world.
The 7th Dimension Telescope consists of 20 0.5m aperture wide-field telescopes. Each telescope is equipped with a camera equipped with a high-performance complementary metal-oxide-semiconductor (CMOS) sensor with 60 million pixels and two or more mid-band filters. So far, installation of 10 of the 20 telescopes planned has been completed.
The characteristic of a 7-dimensional telescope is about 1.2 square degrees.[4]The purpose is to simultaneously capture a wide field of view in up to 40 colors (wavelengths). Each telescope observes two different wavelengths of light through a mid-band filter, allowing the spectrum of all pixels in the field of view to be obtained simultaneously.
It is expected that many difficult problems in astronomy can be solved by using a 7-dimensional telescope. An example of such a difficult problem is the ‘Hubble tension’. The Hubble constant is a quantitative indicator of how fast the universe is expanding.[5]It’s called. However, recently, the Hubble constant has been measured as two different values outside the error range depending on the measurement method, which is called the Hubble constant conflict.
One way to resolve the Hubble constant conflict is to use gravitational wave events. By observing with a 7-dimensional telescope, it is possible to quickly find kilonovas, which are the electromagnetic wave counterparts of gravitational wave events, and at the same time measure their recession speed. The distance to the kilonova can be measured using gravitational waves, and by comparing the recession speed and distance obtained in this way, it is possible to measure the Hubble constant using a method completely independent of the existing method.
Another photo showing the size of the field of view of a 7D telescope. In addition to the full moon shown in Figure 5, the James Webb Telescope’s field of view (based on the NIRCAM camera field of view) is also compared. The field of view of the 7D telescope is approximately 1,000 times that of the James Webb Telescope imaging observation device. [Credit: 서울대학교 중력파우주연구단]
Gravitational wave observations alone can only provide a very rough idea of where the gravitational wave event occurred in the sky. To accurately determine the location of a gravitational wave source, visible light and spectral observations of kilonovae corresponding to gravitational wave events are essential. However, using existing observation techniques, it was difficult to distinguish kilonovas from the numerous variable astronomical objects or noise signals in the estimated location of a very wide gravitational wave event. However, using a 7-dimensional telescope, you can obtain the spectra of all celestial bodies in a wide field of view at once, making it easy to find kilonovas from thousands or tens of thousands of noise signals.
In addition, the 7D telescope is expected to be active in various fields such as galaxy evolution, research on the growth process of supermassive black hole objects, research on the origins of solar system objects, and stellar evolution.
The video released this time was obtained through 7D telescope test observations that began on October 10, 2023. A total of three have been revealed: the Sculptor Galaxy (NGC 253 Galaxy), the Helix Nebula, and the Trifid Nebula. In particular, in the case of the spiral nebula, the colorful appearance observed at various wavelengths was revealed. The colorful appearance of the spiral nebula is due to various elements such as hydrogen, oxygen, sulfur, and helium, and the intensity of light in each color (wavelength) indicates the temperature and chemical composition of the gas that makes up the spiral nebula.
An image of the Trifid Nebula taken by a 7-dimensional telescope. Red is the color produced by hydrogen ionized by the strong starlight of newborn stars, and blue is the color that appears when nearby interstellar clouds reflect starlight. Bright spots in the red and blue nebulae are massive newborn stars. [필터 및 노출시간: 파랑: g(900초), 녹색: r(900초), 빨강: m650(1,800초)] [Credit: 서울대학교 중력파우주연구단/백승학(서울대)]
- Sculptor Galaxy (aka NGC 253 Galaxy): A spiral galaxy located about 10 million light-years away. The galaxy is so named because it is located near the constellation Sculptor. Among the galaxies visible in the southern hemisphere, stars are actively forming and it is one of the galaxies with a fairly large apparent size, making it a useful galaxy for studying galaxy evolution.
- Helix Nebula (aka NGC 7923): It is a celestial body in the ‘planetary nebula’ stage that appears at the end of the star’s evolution process and is located about 650 light-years away from Earth. When a star reaches the end of its life, it ejects a large amount of gas, and these gases appear as clouds distributed around the star, forming a ‘planetary nebula’.
- Trifid Nebula (aka M20 or NGC 6514): A celestial body where an open cluster, an emission nebula, and a reflection nebula are gathered in one place. It is located in the star formation region of the Scutum-Centarum arm, one of the spiral arms of our Galaxy. there is. It is located in the northwest of Sagittarius in the sky and is about 4,100 light-years away from Earth. It is a celestial body frequently observed with the Hubble Space Telescope to study the birth of stars.
#Terminology
[1] These are gravitational waves caused by a celestial body with very strong gravity moving through space and time. In September 2015, mankind became the first to successfully detect gravitational waves when detecting gravitational waves generated from a black hole merger event, for which the 2017 Nobel Prize in Physics was awarded.
[2] When a star dies and explodes, it glows very brightly.
[3] The sunlight that passes through a prism and is divided into rainbow lights is also a type of spectrum.
[4] It corresponds to the field of view of about six full moons, which is about 1,000 times the field of view of the James Webb Space Telescope’s NIRCAM camera.
5) The Hubble constant is the distance of a celestial body divided by the speed at which the celestial body is moving away (retreat speed).
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