ESO - 2000

Information from the European Southern Observatory

ESO Press Release 18/00

4 September 2000 (with Addendum on 6 September)

For immediate release

Fourth Light at Paranal!

VLT YEPUN Joins ANTU, KUEYEN and MELIPAL

It was a historical moment last night (September 3 - 4, 2000) in the VLT Control Room at the Paranal Observatory , after nearly 15 years of hard work. Finally, four teams of astronomers and engineers were sitting at the terminals - and each team with access to an 8.2-m telescope!

From now on, the powerful "Paranal Quartet" will be observing night after night, with a combined mirror surface of more than 210 m 2. And beginning next year, some of them will be linked to form part of the unique VLT Interferometer with unparalleled sensitivity and image sharpness.

YEPUN "First Light"

Early in the evening, the fourth 8.2-m Unit Telescope, YEPUN , was pointed to the sky for the first time and successfully achieved "First Light".

Following a few technical exposures, a series of "first light" photos was made of several astronomical objects with the VLT Test Camera. This instrument was also used for the three previous "First Light" events for ANTU ( May 1998 ), KUEYEN ( March 1999 ) and MELIPAL ( January 2000 ).

These images served to evaluate provisionally the performance of the new telescope, mainly in terms of mechanical and optical quality. The ESO staff were very pleased with the results and pronounced YEPUN fit for the subsequent commissioning phase.

When the name YEPUN was first given to the fourth VLT Unit Telescope, it was supposed to mean "Sirius" in the Mapuche language. However, doubts have since arisen about this translation and a detailed investigation now indicates that the correct meaning is "Venus" (as the Evening Star). For a detailed explanation, please consult the essay On the Meaning of "YEPUN" , now available at the ESO website.

The first images

At 21:39 hrs local time (01:39 UT), YEPUN was turned to point in the direction of a dense Milky Way field, near the border between the constellations Sagitta (The Arrow) and Aquila (The Eagle). A guide star was acquired and the active optics system quickly optimized the mirror system. At 21:44 hrs (01:44 UT), the Test Camera at the Cassegrain focus within the M1 mirror cell was opened for 30 seconds, with the planetary nebula Hen 2-428 in the field.

The resulting "First Light" image was immediately read out and appeared on the computer screen at 21:45:53 hrs (01:45:53 UT). "Not bad! - "Very nice!" were the first, "business-as-usual"-like comments in the room. The zenith distance during this observation was 44° and the image quality was measured as 0.9 arcsec, exactly the same as that registered by the Seeing Monitoring Telescope outside the telescope building. There was some wind.

ESO PR Photo 22a/00

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Caption : ESO PR Photo 22a/00 shows a colour composite of some of the first astronomical exposures obtained by YEPUN . The object is the planetary nebula Hen 2-428 that is located at a distance of 6,000-8,000 light-years and seen in a dense sky field, only 2° from the main plane of the Milky Way. As other planetary nebulae, it is caused by a dying star (the bluish object at the centre) that shreds its outer layers. The image is based on exposures through three optical filtres: B(lue) (10 min exposure, seeing 0.9 arcsec; here rendered as blue), V(isual) (5 min; 0.9 arcsec; green) and R(ed) (3 min; 0.9 arcsec; red). The field measures 88 x 78 arcsec 2 (1 pixel = 0.09 arcsec). North is to the lower right and East is to the lower left. The 5-day old Moon was about 90° away in the sky that was accordingly bright. The zenith angle was 44°.

The ESO staff then proceeded to take a series of three photos with longer exposures through three different optical filtres. They have been combined to produce the image shown in ESO PR Photo 22a/00 .

More astronomical images were obtained in sequence, first of the dwarf galaxy NGC 6822 in the Local Group (see PR Photo 22f/00 below) and then of the spiral galaxy NGC 7793 .

All 8.2-m telescopes now in operation at Paranal

The ESO Director General, Catherine Cesarsky , who was present on Paranal during this event, congratulated the ESO staff to the great achievement, herewith bringing a major phase of the VLT project to a successful end. She was particularly impressed by the excellent optical quality that was achieved at this early moment of the commissioning tests. A measurement showed that already now, 80% of the light is concentrated within 0.22 arcsec.

The manager of the VLT project, Massimo Tarenghi , was very happy to reach this crucial project milestone, after nearly fifteen years of hard work. He also remarked that with the M2 mirror already now "in the active optics loop", the telescope was correctly compensating for the somewhat mediocre atmospheric conditions on this night.

The next major step will be the "first light" for the VLT Interferometer (VLTI) , when the light from two Unit Telescopes is combined. This event is expected in the middle of next year.

Impressions from the YEPUN "First Light" event

ESO PR Video Clip 06/00 "First Light for YEPUN" (5650 frames/3:46 min) [MPEG Video+Audio; 160x120 pix; 7.7Mb] [MPEG Video+Audio; 320x240 pix; 25.7 Mb] [RealMedia; streaming; 34kps] [RealMedia; streaming; 200kps]	ESO Video Clip 06/00 shows sequences from the Control Room at the Paranal Observatory, recorded with a fixed TV-camera in the evening of September 3 at about 23:00 hrs local time (03:00 UT), i.e., soon after the moment of "First Light" for YEPUN . The video sequences were transmitted via ESO's dedicated satellite communication link to the Headquarters in Garching for production of the clip. It begins at the moment a guide star is acquired to perform an automatic "active optics" correction of the mirrors; the associated explanation is given by Massimo Tarenghi (VLT Project Manager). The first astronomical observation is performed and the first image of the planetary nebula Hen 2-428 is discussed by the ESO Director General, Catherine Cesarsky . The next image, of the nearby dwarf galaxy NGC 6822 , arrives and is shown and commented on by the ESO Director General. Finally, Massimo Tarenghi talks about the next major step of the VLT Project. The combination of the lightbeams from two 8.2-m Unit Telescopes, planned for the summer of 2001, will mark the beginning of the VLT Interferometer.

ESO Press Photo 22b/00 [Preview; JPEG: 400 x 300; 88k] [Full size; JPEG: 1600 x 1200; 408k]	The enclosure for the fourth VLT 8.2-m Unit Telescope, YEPUN , photographed at sunset on September 3, 2000, immediately before "First Light" was successfully achieved. The upper part of the mostly subterranean Interferometric Laboratory for the VLTI is seen in front. (Digital Photo).

ESO Press Photo 22c/00 [Preview; JPEG: 400 x 300; 112k] [Full size; JPEG: 1280 x 960; 184k]	The initial tuning of the YEPUN optical system took place in the early evening of September 3, 2000, from the "observing hut" on the floor of the telescope enclosure. From left to right: Krister Wirenstrand who is responsible for the VLT Control Software, Jason Spyromilio - Head of the Commissioning Team, and Massimo Tarenghi , VLT Manager. (Digital Photo).

ESO Press Photo 22d/00 [Preview; JPEG: 400 x 300; 112k] [Full size; JPEG: 1280 x 960; 184k]	"Mission Accomplished" - The ESO Director General, Catherine Cesarsky , and the Paranal Director, Roberto Gilmozzi , face the VLT Manager, Massimo Tarenghi at the YEPUN Control Station, right after successful "First Light" for this telescope. (Digital Photo).

An aerial image of YEPUN in its enclosure is available as ESO PR Photo 43a/99.

The mechanical structure of YEPUN was first pre-assembled at the Ansaldo factory in Milan (Italy) where it served for tests while the other telescopes were erected at Paranal. An early photo ( ESO PR Photo 37/95 ) is available that was obtained during the visit of the ESO Council to Milan in December 1995, cf. ESO PR 18/95.

Paranal at sunset

ESO Press Photo 22e/00
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Wide-angle view of the Paranal Observatory at sunset. The last rays of the sun illuminate the telescope enclosures at the top of the mountain and some of the buildings at the Base Camp. The new "residencia" that will provide living space for the Paranal staff and visitors from next year is being constructed to the left. The "First Light" observations with YEPUN began soon after sunset. This photo was obtained in March 2000.

Additional photos (September 6, 2000)

ESO PR Photo 22f/00 [Preview - JPEG: 400 x 487 pix - 224k] [Normal - JPEG: 992 x 1208 pix - 1.3Mb]	Caption : ESO PR Photo 22f/00 shows a colour composite of three exposures of a field in the dwarf galaxy NGC 6822 , a member of the Local Group of Galaxies at a distance of about 2 million light-years. They were obtained by YEPUN and the VLT Test Camera at about 23:00 hrs local time on September 3 (03:00 UT on September 4), 2000. The image is based on exposures through three optical filtres: B(lue) (10 min exposure; here rendered as blue), V(isual) (5 min; green) and R(ed) (5 min; red); the seeing was 0.9 - 1.0 arcsec. Individual stars of many different colours (temperatures) are seen. The field measures about 1.5 x 1.5 arcmin 2. Another image of this galaxy was obtained earlier with ANTU and FORS1 , cf. PR Photo 10b/99.

ESO Press Photo 22g/00 [Preview; JPEG: 400 x 300; 136k] [Full size; JPEG: 1280 x 960; 224k]	Most of the crew that put together YEPUN is here photographed after the installation of the M1 mirror cell at the bottom of the mechanical structure (on July 30, 2000). Back row (left to right): Erich Bugueno (Mechanical Supervisor), Erito Flores (Maintenance Technician); front row (left to right) Peter Gray (Mechanical Engineer), German Ehrenfeld (Mechanical Engineer), Mario Tapia (Mechanical Engineer), Christian Juica (kneeling - Mechanical Technician), Nelson Montano (Maintenance Engineer), Hansel Sepulveda (Mechanical Technican) and Roberto Tamai (Mechanical Engineer). (Digital Photo).

ESO PR Photos may be reproduced, if credit is given to the European Southern Observatory.

The ESO PR Video Clips service to visitors to the ESO website provides "animated" illustrations of the ongoing work and events at the European Southern Observatory. The most recent clip was: ESO PR Video Clip 05/00 ("Portugal to Accede to ESO (27 June 2000).

Information is also available on the web about other ESO videos.

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