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Object Name: Cl0939+47 (Abell 851) Telescope: Subaru Telescope / Cassegrain Focus Instrument: CISCO (J, K' ), Suprime-Cam (R) Filter: R (red), J (1.25 micron), K' (2.15 micron) Color: Blue (R), Green (J), Red (K') Date: UT 1999 Jan 13 (R), Jan 14 (J), Jan 12 (K') Exposure: 3600 sec (R), 2400 sec (J), 2400 sec (K') Field of View: 120 arcsec by 145 arcsec Orientation: North up, east left Position: RA(J2000.0)=09h43m, DEC(J2000.0)=+46d59m

Explanation:
Galaxies are not evenly distributed throughout the Universe, but tend to reside in structures ranging from groups of a few galaxies to massive clusters containing thousands of galaxies. This image of the distant cluster Abell 851, located five billion light years away from us, is about two million light years across. While the nearest sizable galaxy to our own, M 31 in Andromeda, is about two million light years away with mostly empty space in between, the same volume of space in Abell 851 is filled with many galaxies with a wide range of colors and sizes. Almost every object in this image is a galaxy, with there being only a few stars from our own Milky Way. All galaxy clusters contain bright, red elliptical galaxies, but distant clusters such as this also possess fainter blue galaxies, which are not seen in nearby ones. Both types are clearly visible in this color image, formed from optical and infrared images taken with Subaru' s Suprime-Cam and CISCO cameras. The depth and excellent quality of this image reveal a wealth of information never before seen from the ground.

By studying clusters of galaxies, astronomers hope to understand how individual galaxies form and evolve, as well as the history of the clusters themselves. Theoretical models predict that if the Universe contains enough material to stop its present expansion, then most clusters should have formed very recently. On the other hand, large numbers of distant, old clusters would imply that gravity is insufficient to overcome this expansion.

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Object Name: Hickson Compact Group 40 Telescope: Subaru Telescope / Cassegrain Focus Instrument: CISCO Filter: J (1.25 micron), K' (2.15 micron) Color: Blue (J), Green ([J+K' ]/2), Red (K') Date: UT 1999 Jan 14 (J), Jan 12 (K') Exposure: 480 sec (J), 480 sec (K') Field of View: 1.9 arcmin by 2.9 arcmin Orientation: North up, east left Position: RA(J2000.0)=9h36m24.1s, DEC(J2000.0)=-4d37m39s

Explanation:
Single, isolated galaxies are rather rare in the Universe. They tend to form groups or clusters. A system with two galaxies is called a binary galaxy, a system containing more than two but less than several dozen galaxies is called a group, and a big system containing more than this is called a cluster. There are groups of galaxies in which the members are in so small a space that they appear to be touching each other. These are called compact groups of galaxies.

The image shown here is a compact group of galaxies at a distance of 300 million light years in the constellation of Hydra. It is the 40th group in Hickson's catalog and is therefore called Hickson Compact Group (HCG) 40. From top to bottom, the 5 galaxies in the group are a spiral, an elliptical, two more spirals, and a lenticular (S0). They clearly appear to be touching each other.

Interactions often occur in compact groups where galaxies are located so close to each other. Evidence of tidal interaction as a result of mutual gravitational attraction is actually seen in all 3 spiral galaxies in this group. The S0 galaxy at the bottom also show evidence of interaction at its nucleus. Computer simulations show that, as a result of gravitational interaction, galaxies merge to form 1 or 2 giant galaxies in a time scale short compared to the age of the Universe. We may be observing such a merger here. Two blueish white dots in the image are stars in our own Galaxy. Small reddish objects are galaxies located billions of light years away. They appear redder than the members of HCG40 because of the Doppler effect caused by the expansion of the Universe.

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Object Name: Jupiter and Saturn Telescope: Subaru Telescope / Cassegrain Focus Instrument: CAC Filter: B (Blue), V (visible), R (red) Color: Blue (B), Green (V), Red (R) Date: UT 1999 Jan 22 Exposure: 0.1 sec for each of the B, V, and R filters (with an ND filter), except for the Saturn's B-band image taken with a 0.5 sec exposure Field of View: 50 arcsec by 50 arcsec

Explanation:
Left: Jupiter Jupiter is the largest planet in the solar system with a diameter 11 times larger than that of the Earth. The image shows a complex feature of time variable bands, running parallel to the equator. The famous Great Red Spot is seen as an elliptical feature at the bottom right. Its diameter is twice that of the Earth. A black spot seen in the lower center is Ganymede, the third Jovian satellite. It looks dark because its reflectivity (albedo) is small compared to that of Jupiter. Ganymede's shadow is located beyond the surface of Jupiter when this observation was made. Images were taken at UT 5:34 for B, 5:39 for V, and 5:43 for R.

Right: Saturn Saturn is the second largest planet in the solar system with a diameter 9 times larger than that of the Earth. The image shows time variable bands running parallel to the equator. These are similar to those seen on Jupiter, but are simpler in appearance. Saturn's rings have a diameter of 2.26 times larger than that of Saturn. The rings consist of three major ringlets, called the A, B, and C rings from outside to inside. The C ring is too faint to be seen in this image. The gap between the A and B rings is called Cassini's Division, after its discoverer. Images were taken at UT 6:22 for B, 6:27 for V, and 6:34 for R.

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Object Name: Part of Andromeda Galaxy (M31) Telescope: Subaru Telescope / Cassegrain Focus Instrument: Suprime-Cam Filter: R (red) Color: Grayscale Date: UT 1999 Jan 13 Exposure: 900 sec Field of View: 3 acmin by 4 arcmin Orientation: North is upper-right, east is upper-left Position: RA(J2000.0)=0h40m33.51s, DEC(J2000.0)=+40d44m45s

Explanation:
The Andromeda galaxy (Messier 31) is an assembly of some 100 billions of stars and is a spiral galaxy similar to our own Galaxy. It is located 2.5 million light years away, and is one of our nearest neighbors. This image, taken with a red filter, shows just a tiny part (corresponding to the white rectangle in the attached sheet) of the Andromeda galaxy, whose total apparent size is about 3 degrees. The image shows many points of light which are individual stars in the Andromeda galaxy, and appears very like our own Milky Way galaxy when observed with a small telescope. It is difficult to resolve each of these stars from the ground, but the high angular resolution and sensitivity of the Subaru Telescope enables us to resolve these stars with one short exposure. The bright region from the lower-left to upper-right is part of the spiral structure, wheremany young stars are shining brightly.

This image was taken with a large optical camera called Suprime-Cam, which is equipped with six 2048x4096 CCDs specially tuned for astronomical observations. Vertical and horizontal black stripes are gaps between the CCD chips and faulty pixels. Many such exposures, taken with the telescope pointing slightly changed, can be combined to remove these features and produce beautiful images.

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Object Name: NGC4051 Telescope: Subaru Telescope / Cassegrain Focus Instrument: Suprime-Cam (Wide field camera for visible light) Filter: R-band Color: Grayscale Date: UT 1999 Jan 13 Exposure: 2 min Field of View: 3 arcmin by 4 arcmin Orientation: North is right, east is up Position: RA(J2000.0)=12h3m9.6s, DEC(J2000.0)=+44d31m53s

Explanation:
NGC4051 is a spiral galaxy in the constellation Ursa Major at the distance of 35 million light years. This galaxy belongs to a class called Seyfert 1 galaxies, because of its bright non-stellar nucleus. NGC4051 is among the six classical Seyfert galaxies studied by the astronomer Carl Seyfert in 1943, though its nuclear activity is the lowest among Seyfert 1 galaxies. NGC4051 is morphologically classified as intermediate between barred and un-barred. Its galactic plane is seen inclined to us at about 40 degrees. Three grand-design spiral arms are seen emanating from the ends of a weak bar. This picture taken with the Subaru Telescope reveals numerous HII regions along the sprial arms. These are hot ionized clouds of hydrogen gas formed around newly born stars, and demonstrate the superb resolution of the Subaru Telescope.

Narrow stripes seen in the picture are due to the gaps between the CCD chips in Suptime-Cam. At the center of the galaxy there is a bright non-stellar nucleus, which cannot be seen in this long-exposure picture as it is buried in the light of surrounding stars.

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Object Name: Orion Nebula Telescope: Subaru Telescope / Cassegrain Focus Instrument: CISCO Filter: J (1.25 micron), K' (2.15 micron), H 2 -line (2.12 micron) Color: Blue (J), Green (K'), Red (H 2 -line) Date: UT 1999 Jan 14 (J), Jan 12 (K'), Jan 14 (H 2 -line narrow band filter) Exposure: 68 sec (J), 338 sec (K'), 30 sec (H 2 -line) Field of View: 4.1 arcmin by 4.8 arcmin Orientation: North up, east left Position: RA(J2000.0)=5h35m15s, DEC(J2000.0)=-5d23m29s

Explanation:
This is an infrared image of the the famous Orion nebula (Messier 42), located 1500 light years away. At the center of the image is the Trapezium, a group of four bright stars. Many stars seen around the Trapezium are young stars embedded in the Orion molecular cloud located behind the Orion nebula. Many of them are seen only at infrared wavelengths. Blue, faint, and diffuse emission extending over the entire region is due to hot gas ionized by strong ultraviolet radiation emitted by the Trapezium stars. The bright bar seen in the lower left part of the image is an ionization front.

Above the Trapezium, a butterfly-like red feature is seen in the image, containing the Kleinman-Low (KL) nebula which is deeply embedded in the Orion molecular cloud. At the center of the KL nebula is a star called IRc2, which is in the process of forming. This star is believed to be 30 times more massive than the Sun, and its activities are the cause of the big butterfly feature.

This false-color image was synthesized from three images taken with J (1.25 micron), K' (2.15 micron), and H 2 -line (2.12 micron, narrow band) filters, assigning blue for J, green for K', and red for H 2 -line images. Nine images of contiguous fields were obtained with CISCO, which has a 2 arcmin by 2 arcmin field of view, and were combined to make this image. Some ghost (false) images from very bright stars are seen.

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Object Name: Orion KL Region Telescope: Subaru Telescope / Cassegrain Focus Instrument: CISCO Filter: H 2 -line (2.12 micron), N204 (2.04 micron) Color: Grayscale (Reddish) Date: UT 1999 Jan 14 Exposure: 30 sec Field of View: 2 arcmin by 2 arcmin Orientation: North up, east left

Explanation:
This is an enlarged image of the region around the Kleinman-Low nebula in the Orion cloud located 1500 light years away. This image is taken in light at 2.12 micron, which is emitted by warm molecular hydrogen gas with an absolute temperature of 2000 K. This is Subaru's first image in the light of a single emission line, demonstrating its high resolution capability. Although not seen in this image, at the center of the giant butterfly-like feature is IRc2, a star 30 times more massive than the sun which is in the process of forming. A strong wind with a speed of more than 100 kilometers per second is blowing out from IRc2, evacuating the butterfly-like cavity and allowing infrared light to escape. Many finger-like features are seen radially emanating from the Orion KL region, produced when the strong stellar wind from IRc2 collides with the surrounding cold material, heating it to around 2000 K and causing the hydrogen molecules to emit light. The vertical and horizontal stripes and moire patterns are artifacts of the initial data processing. Two separate images were combined to produce this image, and the black and white dots are a result of this process.

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Object Name: PG1115+080 (Gravitational Lens) Telescope: Subaru Telescope / Cassegrain Focus Instrument: CISCO (J, K'), Suprime-Cam (R) Filter: R (red), J (1.25 micron), K' (2.15 micron) Color: Blue (R), Green (J), Red (K') Date: UT 1999 Jan 13 (R), Jan 14 (J), Jan 12 (K') Exposure: 420 sec (R), 35 sec (J), 275 sec (K') Field of View: 4.7 arcsec by 5 arcsec Orientation: North up, east left

Explanation:
Einstein's Theory of General Relativity predicts that the gravitational pull from massive objects is able to deflect rays of light in the same way as do lenses. Many examples of this "gravitational lensing" have been discovered, where light from a distant object is deflected by an intervening galaxy or group of galaxies whose gravity deforms the space around them. Subaru has observed one such object, known as PG1115+080, where a distant quasar (10 billion light years away) is located almost directly behind a much closer galaxy (3 billion light years away). When the alignment is as good as this, light can take multiple routes from the quasar to the observer, and many images are seen. The left panel, a combination of optical and near-infrared images, shows four bright images of the quasar around the central, red galaxy which is acting as the lens. The excellent image quality obtained by Subaru (0.33 arcsec FWHM for this image) clearly separates all the images. The panel on the right shows faint, extended light suggestive of a ring which is expected when the source and lensing galaxy are this closely aligned. Astronomers can use the relative brightness and position of the individual images in a gravitationally-lensed system to determine how rapidly the Universe is expanding and whether it will continue to expand forever, or if it will eventually slow down and collapse in a Big Crunch.

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Object Name: The Most Distant Quasar at z=5.0 Telescope: Subaru Telescope / Cassegrain Focus Instrument: CISCO Filter: J (1.25 micron), K' (2.15 micron) Color: Blue (J), Green ([J+K']/2), Red (K') Date: UT 1999 January 14 Exposure: 800 sec (J), 1600 sec (K' ) Field of View: 110 arcsec x 110 arcsec Orientation: North up, east left

Explanation:
Quasars are the most energetic objects in the Universe. The brightest of them outshine entire galaxies, and are believed to be powered by black holes which weigh more than a billion Suns, yet are not much larger than the solar system. Their extreme luminosities make them easy to see at great distances, and the quasar at the center of this image, discovered by the Sloan Digital Sky Survey, is the most distant currently known (14 billion light years away), and one of only a handful of objects at the edge of the Universe. We see such objects at a time when the Universe was only about one billion years old, compared to its present age of 15 billion years, because of the time it takes the light to reach us. Due to the expansion of the Universe, distant objects appear to be moving away from us very rapidly, and the Doppler shift causes us to see light from this quasar at a frequency six times lower than that at which it was emitted. Therefore, although this image was taken by Subaru's infrared camera CISCO, we are actually looking at ultraviolet light from the quasar.

Astronomers speculate that for massive objects like quasars to form so soon after the Big Bang, they must lie in especially dense regions of the early Universe. For this reason, it is believed that galaxies should be forming in the space around distant quasars, and large telescope such as Subaru can be used to look for such objects. However, the faint, red galaxies which can be seen in this image are located much closer to us.

(Note: The information is correct as of the release date.)