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Scientific Background

JELT is expect to take advantage its large primary mirror diameter to perform :
high-resolution imaging using adaptive optics (AO), and high-dispersion spectroscopy on faint objects.

JELT is also anticipated to play a complementary role in next-generation space missions such as James Webb Space Telescope (JWST) and Space Infrared Telescope for Cosmology and Astrophysics (SPICA) projects, which will perform wide-field surveys in infrared wavelength. Scientific goals for JELT are briefly presented here based on current research trends and future planning.

It should be noted that topics presented here are just a part of achievement realized with capability of JELT. Historically, such observational innovation has always brought with it unexpected new discoveries, suggesting that JELT may discover completely unknown classes of objects. Frontiers of science will also be expanded during construction of JELT, and new research targets are expected to emerge. The context in which construction of the 8-10m telescopes took place in the 1980s and '90s can be readily seen in science cases proposed in the blue-book for Subaru Telescope :

Determination of cosmological parameters
- Loh & Spillar test
- Hubble Diagram
- SN Ia and q0 parameter
- θ-z relation

Search for dark matter
- M/L in cluster of galaxies
- Large-scale structure at high redshifts

Birth and evolution of galaxies
- Discovery of protogalaxies (Lyα emitters, QSO absorbers)
- Origin of the Hubble sequence
- Structure of the galaxy and its evolution

Formation of stars and planetary systems
- Distribution of interstellar medium and its characteristics
- Origin of dust and its characteristics
- Molecular clouds
- Formation and evolution of protoplanetary disks
- Discovery of extra-solar planets
- Characteristics of protostars
- Starbursts
- Connection between starburst and AGNs
- Solar planets
- Organic systems in space and origins of life

High-density objects
- Birth and evolution of AGNs
- Structure of AGNs
- Measurement of cosmological parameters using gravitational lensing

Stellar evolution and nucleosynthesis
- Search for population III stars
- Nucleosynthesis of supernovae
- Stellar seismology

While active research continues in most of the areas shown above, there has been substantial progress in a range of new areas that were not conceived in the design of the 8m-class telescopes. For example, no high-redshift populations such as Lyman Break galaxies, extremely red objects, and submillimeter galaxies had yet been discovered, nor had gamma ray bursts. Little was known about an early history of the universe, and of course, there had been no sign of dark energy. The relationship between mass of supermassive black holes at the center of galaxies and bulge mass was also unknown, and extra-solar planets had not been detected. Nobody dreamed of heteromorphous planets such as hot Jupiters. Even in the solar neighborhood, the existence of outer-rim objects such as Edgeworth Kuiper Belt Objects was not expected.

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