First Release of Images and Videos Taken with 7-Dimensional Telescope

Summary

A research team from the Department of Physics & Astronomy at Seoul National University has revealed first-light images of the 7-Dimensional Telescope (7DT). 7DT is a new multiple telescope system that will hunt for optical counterparts of gravitational-wave events and perform spectral mapping of the Universe. It can perform simultaneous spectral mapping of the sky at 40 wavelengths. The released images show colorful views of several celestial bodies and demonstrate the scientific capabilities of 7DT. In the coming years, 7DT is expected to study mysterious objects in the universe, such as gravitational-wave sources, supermassive black holes, new transient sources, peculiar stellar phenomena, and small bodies of the solar system. 

7DT images and videos are available in this link: Download Site for 7DT First Images and Videos

For questions, contact Myungshin Im (SNU/GWUniverse) at myungshin.im@gmail.com

• The research team from Seoul National University has released the first-light images of the 7-Dimensional Telescope (7DT) developed by the Center for the Gravitational-Wave Universe  (Center for GWUniverse; Principal Investigator: Professor Hyeong-Mok Lee of Seoul National University) and the Mid-Career Researcher program of the National Science Challenge Initiative project supported by the Ministry of Science and ICT and the National Research Foundation of Korea.

The 7-Dimensional Telescope, led by Professor Myungshin Im's team at Seoul National University, is a state-of-the-art multi-telescope system built at the El Sauce Observatory in the Andes Mountains of Chile. The construction of 50% of 7DT was completed in October 2023, and the released images were taken with this partial system. 

• Recent advancements in astronomical observation technology make it possible to observe the universe in real time, much like a video. Consequently, a multitude of transient astronomical events, such as gravitational wave sources(1) and supernovae(2), are being discovered in large numbers. These transients often exhibit sudden changes in brightness and color.

(1) Gravitational waves are ripples in spacetime caused by the movement of extremely dense celestial bodies. The detection of gravitational waves generated during the merger event of black holes in September 2015 marked humanity's first successful detection of gravitational waves, leading to the Nobel Prize in Physics award in 2017.

(2) The phenomenon of stars shining very brightly as they explode upon their death.

To properly understand the characteristics of astronomical transients, it is essential to observe their spectra(3), i.e., dividing light into multiple colors. However, traditional observational techniques only allowed for simultaneous spectral observation of a very small number of celestial bodies (usually 1, up to a maximum of 1,000) within the telescope's field of view. This posed a significant challenge in swiftly tracking the characteristics of numerous transients over a wide area in the sky.

(3) The splitting of sunlight into rainbow colors as it passes through a prism is also a type of spectrum.

• Professor Myungshin Im's research team has developed a "7-Dimensional Telescope" to overcome the difficulties of previous research. This telescope can simultaneously obtain spectra for all 60 million pixels in the field of view, representing the world-first attempt.

The 7-Dimensional Telescope consists of twenty 0.5-meter diameter wide-field telescopes. Each telescope is equipped with two or more special medium-band filters and a high-performance camera featuring a complementary metal–oxide semiconductor (CMOS) sensor with 60 million pixels. Out of the planned 20 telescopes, installation for ten telescopes has been completed.

 The distinctive feature of the 7-Dimensional Telescope lies in its ability to capture an image over a wide field of approximately 1.2 square degrees(4) simultaneously in up to 40 colors (wavelengths). Each telescope observes pairs of light with different wavelengths through the medium-band filters, allowing simultaneous acquisition of spectra for all pixels in the field of view. 

(4) This field of view is equivalent to about six full moons, approximately 1,000 times larger than the James Webb Space Telescope's NIRCAM camera

• The 7-Dimensional Telescope is expected to tackle various challenges in astronomy. One such challenge is the 'Hubble tension,' which is a recent dispute over the value of the Hubble constant (5), a quantitative indicator of how rapidly the universe is expanding. 

(5) The Hubble constant is the ratio of the velocity at which a celestial object moves away (recession velocity) to its distance from Earth.

The Hubble tension can possibly be resolved by utilizing gravitational wave events. Through simultaneous observations of spectra and images with the 7-Dimensional Telescope, one can quickly identify kilonovae - electromagnetic wave counterparts of gravitational wave events – and measure their recession velocities. By combining the recession velocities with the distance information obtained from gravitational waves, one can measure the Hubble constant independently from the conventional methods.

Due to poor determination of the location of gravitational wave events, it has been challenging to distinguish kilonovae from numerous variable objects and spurious signals. Distinguishing kilonovae from spurious objects requires spectral observations of all the sources one by one. With the 7-Dimensional Telescope, obtaining spectra for all objects within its wide field of view is possible, making it easy to pick up a kilonova amid thousands or even tens of thousands of spurious signals.

In addition to addressing the Hubble tension, the 7-Dimensional Telescope is anticipated to contribute significantly to various fields in astronomy, including the study of the galaxy evolution, supermassive black holes, the origin of solar system objects, and the evolution of stars.

Image & Video Release Contents

7DT images and videos are available in this link: Download Site for 7DT First Images and Videos

The released images and videos were obtained through the commissioning observations of the 7-Dimensional Telescope, which began on October 10, 2023. The images include three objects: the Sculptor Galaxy (NGC 253), the Helix Nebula, and the Trifid Nebula.

Especially noteworthy is the diverse appearance of the Helix Nebula observed in various wavelengths. The intricate patterns of the Helix Nebula originate from a variety of elements such as hydrogen, oxygen, sulfur, helium, and the intensity of light in each color (wavelength) reveals information about the temperature and chemical composition of the gases constituting the Helix Nebula.

(1) Sculptor Galaxy (NGC 253): Located approximately 10 million light-years away, it is a spiral galaxy near the constellation Sculptor, earning its name. This galaxy, visible from the Southern Hemisphere, is actively forming stars and is one of the largest galaxies in apparent size, which makes it useful for galaxy evolution studies.

(2) Helix Nebula (NGC 7923): Positioned about 650 light-years away, the Helix Nebula represents a celestial object in the final stages of the evolution process known as the "planetary nebula" phase. As stars reach the end of their lifespan, they expel large amounts of gas, and the dispersed clouds around the star form the unique and beautiful appearance of a planetary nebula.

(3) Trifid Nebula (M20 or NGC 6514): This object is made of an emission nebula, a reflection nebula, and a dark nebula. Located in the star-forming region of the Scutum-Centaurus arm of the Milky Way galaxy, it is situated northwest of the Archer constellation in the sky and is approximately 4,100 light-years away from Earth. The Trifid Nebula is frequently observed with telescopes such as the Hubble Space Telescope for studying the birth of stars.

□ Credits

The 7DT data used for the figures and movies were obtained with the contribution of various people below.

7DT Principal Investigator: Myungshin Im (SNU)

Project manager: Ji Hoon Kim (SNU)

Database management: Seo-Won Chang (SNU)

Data Reduction: Gregory S.-H. Paek (SNU)

Telescope Operation: Hyeonho Choi (SNU)

Data Transfer: Hongjae Moon (SNU)

and other 7DT team members

And special thanks to the staffs of ObsTech for their on-site service at the El Sauce Observatory.

Updated on 2024-02-13 by M. Im (SNU/GWUniverse)