Posted on by Fraser Cain

Star on the Run

Artist illustration of a star ejected from the Large Magellanic Cloud. Image credit: ESO. Click to enlarge.
Observations with Kueyen, one of the 8.2m telescopes composing the ESO Very Large Telescope (VLT), have led to the discovery of a short-lived massive star that is moving at a very high speed through the outer halo of the Milky Way galaxy and into intergalactic space. This finding could provide evidence for a previously unknown massive black hole in the heart of the Milky Way’s closest neighbour, the Large Magellanic Cloud.

The star, named HE 0437-5439, was discovered by the Hamburg/ESO sky survey [1] , a project aimed at detecting quasars but which discovered many faint blue stars as well. Scientists [2] at the Dr. Remeis-Sternwarte (University of Erlangen-Nürnberg, Germany) and the Centre for Astrophysics Research (University of Hertfordshire, UK) found what is likely to be a hot massive main-sequence star, far out in the halo.

This came as a great surprise. Massive stars have lifetimes of only some tens or hundreds of million years, short lived for astronomical standards, but the halo does not usually host stars as young as this. In fact, it contains the oldest stars in the Milky Way that are more than ten billion years old. Massive stars are usually found in or near star forming regions in the Galactic disc such as the famous Orion nebula: HE 0437-5439 is indeed similar to the trapezium stars that make the Orion nebula shine.

Data were obtained with the ESO VLT and its high resolution UVES spectrograph. This allowed the chemical composition to be measured which turned out to be similar to that of the Sun, confirming that HE0437-5439 is a young star. Its mass is eight times larger than that of the Sun and the star is only 30 million years old. It is almost 200,000 light years away from us in the direction of the Doradus Constellation (“the Swordfish”).

Even more exciting was the fact that the data indicated the star to be receding at a velocity of 723 km/s, or 2.6 million kilometres per hour. HE0437-5439 moves so fast that the gravitational attraction of the Milky Way is too small to keep it bound to the Galaxy. Hence the hyper-velocity star will escape into intergalactic space.

As the star is moving so fast, it must have been born far away from its present position and accelerated to where we observe it today. What accelerated the star to such a high speed? Calculations carried out already in the late 1980s showed that a so-called massive black hole (SMBH), i.e. a black hole a million times as massive as the Sun, or larger, could provide the enormous acceleration. If a binary star approaches the SMBH, one star falls towards the SMBH while its companion is ejected. The Galactic Centre of the Milky Way hosts such a black hole of about 2.5 million solar masses, and this might have accelerated HE0437-5439.

But the necessary travel time was found to be more than three times the age of the star. Hence the star is too young to have travelled all the way from the Galactic centre to its present location. Either the star is older than it appears or it was born and accelerated elsewhere.

A different clue to the origin of HE0457-5439 comes from its position in the sky. HE0437-5439 is 16 degrees away from the Large Magellanic Cloud (LMC), one of the nearest neighbouring galaxies to the Milky Way. This galaxy lies at a distance of 156,000 light years. HE0457-5439 is even more distant than the LMC and is much closer to the LMC than to the galaxy. The astronomers showed that the star could have reached its present position within its lifetime if it were ejected from the centre of the LMC. This, in turn, would provide evidence for the existence of a SMBH in the LMC.

Another explanation would require the star to be the result of the merging of two stars, belonging to so-called blue stragglers class of stars, which are older than standard evolution models predict them to be. Indeed, its age could then be as much as the lifetime of a 4 solar mass star which is more than 6 times the lifetime of an 8 solar mass star.

The astronomers propose two additional observations to distinguish between the two options. The abundance of certain elements in stars belonging to the LMC is only half that of the Sun. A more precise measurement with UVES would indicate whether the star has a metal abundance appropriate to LMC stars or not. The second is to measure how much the star moves in the transverse direction on the sky, using astrometric measurements.

The research presented here is detailed in a paper to be published in Astrophysical Journal Letters.

Notes
[1]: The Hamburg/ESO sky survey is a collaborative project of the Hamburger Sternwarte and ESO to provide spectral information for half of the southern sky using photographic plates taken with the now retired ESO-Schmidt telescope. These plates were digitized at Hamburger Sternwarte.

[2]: The astronomers are Heinz Edelmann (Dr. Remeis-Sternwarte of the University of Erlangen-Nürnberg, Germany, now at University of Texas, Austin, USA), Ralf Napiwotzki (Centre for Astrophysics Research, University of Hertfordshire, UK), Uli Heber (Dr. Remeis-Sternwarte of the University of Erlangen-Nürnberg, Germany), Norbert Christlieb and Dieter Reimers (Hamburger Sternwarte, Germany).

Original Source: ESO News Release

Posted on by Fraser Cain

Dione Beneath the Rings

Dione underneath Saturn’s wispy F ring. Image credit: NASA/JPL/SSI. Click to enlarge.
Saturn’s moon Dione is about to swing around the edge of the thin F ring in this color view. More than one thin strand of the F ring’s tight spiral can be seen here.

The terrain seen on Dione is on the moon’s Saturn-facing hemisphere. The diameter of Dione is 1,126 kilometers (700 miles).

Images taken using infrared, green and ultraviolet spectral filters were composited to create this color view. The images were taken with the Cassini spacecraft narrow-angle camera on Sept. 20, 2005, at a distance of approximately 2 million kilometers (1.2 million miles) from Dione and at a Sun-Dione-spacecraft, or phase, angle of 48 degrees. The image scale is 12 kilometers (7 miles) per pixel.

The Cassini-Huygens mission is a cooperative project of NASA, the European Space Agency and the Italian Space Agency. The Jet Propulsion Laboratory, a division of the California Institute of Technology in Pasadena, manages the mission for NASA’s Science Mission Directorate, Washington, D.C. The Cassini orbiter and its two onboard cameras were designed, developed and assembled at JPL. The imaging operations center is based at the Space Science Institute in Boulder, Colo.

For more information about the Cassini-Huygens mission visit http://saturn.jpl.nasa.gov . The Cassini imaging team homepage is at http://ciclops.org .

Original Source: NASA/JPL/SSI News Release

Posted on by Fraser Cain

Inmarsat-4 Blasts Off from Sea Launch

Zenit-3SL blasting off from the Odyssey Launch Platform. Image credit: Boeing. Click to enlarge.
Sea Launch Company today successfully delivered the Inmarsat-4 (I-4) communications satellite to geosynchronous transfer orbit (GTO). Early data indicate the spacecraft is in excellent condition.

A Zenit-3SL vehicle lifted off at 6:07 am PT (14:07 GMT), from the Odyssey Launch Platform, positioned at 154 degrees West Longitude. All systems performed nominally throughout the flight. The Block DM-SL upper stage inserted the 5,958 kg (13,108 lb.) satellite to geosynchronous transfer orbit, on its way to a final orbital position of 53 degrees West Longitude. A ground station at Lake Cowichan, in British Columbia, acquired the first signal from the satellite less than 25 minutes after spacecraft separation, as planned.

Inmarsat-4 is designed to provide high-speed mobile service to people throughout the Americas during its 13-year service life. It is one in a series of satellites designed to support the Broadband Global Area Network (BGAN) for high-speed delivery of Internet and intranet content and solutions, video-on-demand, videoconferencing, fax, e-mail, phone and LAN access. One of a family of three similar spacecraft, this Inmarsat-4 F2 satellite carries a single global beam that covers up to a third of the Earth’s surface, 19 wide spot beams and 228 narrow spot beams. It has a total end-of-life power of 13kW.

Following acquisition of the spacecraft’s signal, Jim Maser, president and general manager of Sea Launch, congratulated Inmarsat and EADS Astrium. “We have marked several milestones in this mission such as our first mission for Inmarsat and our first European-built spacecraft, and our successful mission is the most significant milestone of all! Our customer is satisfied that we have met all of their requirements,” Maser said. “Once again, we have done what we said we would do. We look forward to future missions with Inmarsat as well as with EADS Astrium. I want to thank every member of the Sea Launch team for making this mission success possible.”

Andrew Sukawaty, Chairman and Chief Executive of Inmarsat plc (LSE:ISAT), said, “We thank the team at Sea Launch for this innovative and highly professional launch. Years of preparation have come together. With the launch of our second I-4 satellite, we look forward to offering up to half megabit internet connection covering up to 90% of the Earth’s land mass – truly Broadband for a mobile planet.”

Sea Launch Company, LLC, headquartered in Long Beach, Calif., is the world’s most reliable heavy-lift commercial launch service. This international partnership offers the most direct and cost-effective route to geostationary orbit. With the advantage of a launch site on the Equator, the reliable Zenit-3SL rocket can lift a heavier spacecraft mass or provide longer life on orbit, offering best value plus schedule assurance. For additional information and images of this successfully completed mission, visit the Sea Launch website at: www.sea-launch.com

Original Source: Boeing News Release

Posted on by Fraser Cain

Expedition 12 Completes First Spacewalk

Expedition 12 Flight Engineer Valery Tokarev and Commander Bill McArthur. Image credit: NASA. Click to enlarge.
NASA astronaut Bill McArthur and Russian cosmonaut Valery Tokarev performed the first spacewalk of their six-month stay on the international space station. They installed a new camera and discarded an inactive science probe.

McArthur, the Expedition 12 commander, and Tokarev, the expedition flight engineer, began their spacewalk from the Quest Airlock at 10:32 a.m. EST. The spacewalk lasted five hours, 22 minutes. Their spacewalk was the first using U.S. space suits since April 2003.

It started about an hour later than planned, because the crew had to re-pressurize the Quest airlock to open a misaligned valve. The valve was in the interior portion of the two-chambered module. With the valve properly positioned, they again depressurized the outer chamber to begin their work outside.

Once out the door, the crew easily made up the time. They completed all primary tasks and some get-ahead jobs. They installed a television camera on the outboard end of the port truss segment. The camera will be an important aid during future assembly work when additional truss segments are added to the port side of the complex.

The crew retrieved the camera’s stand from an external tool platform attached to Quest, brought the equipment out to the port truss, installed the camera and hardware on its stand. The camera was powered and provided its first views from space just before 1 p.m. EST.

Next, flight controllers asked the crew to complete a get-ahead task by removing a failed electronics box called a Rotary Joint Motor Controller. The controller will be returned on the next space shuttle mission so engineers can determine why it failed. The analysis will be used to evaluate similar hardware shipped to the station.

The pair then moved hand over hand to the highest point of the station, the P6 truss. It’s approximately 50 feet above the U.S. Destiny Lab. McArthur removed an old experiment called the Floating Potential Probe from its stand and pushed it away from the station. It is expected to burn up in the Earth’s atmosphere in about 100 days.

The experiment was installed during an assembly mission in 2000 to characterize the electrical environment around the station’s solar arrays. Imagery from the last shuttle showed pieces of the experiment were missing or out of place. Since it was no longer used, it was removed and discarded.

The crew moved ahead with the final get-ahead task before calling it a day. They quickly removed a failed circuit breaker from the Mobile Transporter and installed a new one. Called a Remote Power Control Module, the breaker provides power for redundant heating on the transporter. The transporter is a type of space rail car that moves along the station’s truss structure.

With all tasks completed, McArthur and Tokarev entered the airlock and began re-pressurizing it at 3:54 p.m. EST. It was the 63rd spacewalk in support of station assembly and maintenance; the 35th staged from the station; and 18th staged from Quest. It was the third spacewalk for McArthur and the first for Tokarev.

Original Source: NASA News Release

Posted on by Fraser Cain

Ultraviolet Haze at Titan

Thin haze around Titan. Image credit: NASA/JPL/SSI. Click to enlarge.
Looking back toward the sun brings out the thin haze that hovers 500 kilometers (310 miles) above Saturn’s moon Titan.

The haze is composed of small particles whose diameter is comparable to the wavelength of light, which is ultraviolet light centered at 338 nanometers. Particles of this scale scatter sunlight most effectively in the direction opposite to the direction of sunlight. Scientists are still trying to understand what processes produce this thin, high-altitude haze layer.

North on Titan is up and tilted 10 degrees to the right. Titan is 5,150 kilometers (3,200 miles) across.

This image was taken with the Cassini spacecraft narrow-angle camera on Sept. 24, 2005, at a distance of approximately 917,000 kilometers (570,000 miles) from Titan and at a Sun-Titan-spacecraft, or phase, angle of 145 degrees. Image scale is 5 kilometers (3 miles) per pixel.

The Cassini-Huygens mission is a cooperative project of NASA, the European Space Agency and the Italian Space Agency. The Jet Propulsion Laboratory, a division of the California Institute of Technology in Pasadena, manages the mission for NASA’s Science Mission Directorate, Washington, D.C. The Cassini orbiter and its two onboard cameras were designed, developed and assembled at JPL. The imaging operations center is based at the Space Science Institute in Boulder, Colo.

For more information about the Cassini-Huygens mission visit http://saturn.jpl.nasa.gov . The Cassini imaging team homepage is at http://ciclops.org .

Original Source: NASA/JPL/SSI News Release

Posted on by Fraser Cain

What’s Up This Week – November 7 – November 13, 2005

Our Moon. Image credit: Blackett Observatory. Click to enlarge.
Monday, November 7 – Tonight Mars is at opposition, meaning that it rises just as Sol sets. Be sure to be outside at twilight to catch the awesome appearance of Venus to the west/southwest and Mars rivaling it in the east. You don’t want to miss this outstanding pair.

While the bright planets will try to steal the show, no place on the lunar surface can steal your heart like the Caucasus Mountains. Located tonight along the terminator in the north, stop and really take the time to appreciate their beauty. Like the earthly Caucasus which stretches 1500 kilometers between the Black and Caspian Seas, these stunning mountains extend 500 kilometers between the lunar “seas” of Mare Frigoris and Mare Serenitatis. While most of us could never climb to the 5642 meter summit of Mt. Eibrus, we can match that with our eyes as we power up to look at small crater Callipus caught in Caucasus’ midst. The highest peak is to its west and rises to a stunning 5303 meters above the desolate surface.

Climb the mountains. Their slopes, enclaves and plateaus were formed by the same volcanic process as those bordering Asia Minor. Look for Aristoteles and Eudoxus to the north-east, sitting like small countries along the borders. Where your imagination takes you is 384,000 kilometers away…

Tuesday, November 8 – Born on this day 1656, the great Edmund Halley made his mark on history as he became best known for determining the orbital period of the comet which bears his name. English scientist Halley, had many talents however, and in 1718 discovered what were referred to as “fixed stars”, actually displayed proper motion. If it were not for Halley, Sir Isaac Newton may never have published his now famous work on the laws of gravity and motion. Tonight let’s honor Halley by observing one of the all time greatest of double stars in motion – Almach.

Gamma Andromedae is the last in the chain of bright stars that extends from the northern-eastern corner of the “Square of Pegasus”. It may have been discovered to be a double as early as 1788, but F.W. Struve was the first to record its measurements in 1830. To even the smallest of telescopes, its golden primary is easily separated from the blue-green secondary, but for larger scopes – there’s something more.

In 1842, Struve discovered the companion star is itself a very close double of similar magnitude and spectral type. In 1982 they reached their maximum separation of .5, but it is possible to see them as companion stars thanks to their highly ellipitcal orbits. The brighter of the two is also a spectroscopic binary, making this a quadruple system. The light you see tonight from this beautifully colored pair left 3 years after Halley’s death.

Wednesday, November 9 – Be sure to take binoculars out just after sunset to catch Antares and Mercury within two degrees of each other. Both will be very low on the horizon, so don’t wait too long…

Tonight the Moon will be closest to Earth, so let’s get a good close look at striking trio of craters just south of central along the terminator. The smallest and youngest of the three is Arzachel at the southern end of the chain and far larger and older Ptolemy is to the north. Look closely at central crater Alphonsus, for it is the only crater to have photographic proof that changes do occur on the lunar surface. On October 26, 1956 a photo was taken showing a strange cloud just east of its central peak. Russian astronomer, Nikolai Kozyrev was fascinated and doggedly observed and photographed a changing Alphonsus until he had a huge success of the night of November 2, 1958. In taking a series of spectrograms (not an easy feat for those times and equipment), he successfully captured unmistakable evidence of a cloud of carbon molecule “outgassing”. Spaseba!

Today is the birthdate of Carl Sagan. Born in 1934 Sagan was an American planetologist, exobiologist, popularizer of science and astronomy, and novelist. His influential work and enthusiasm inspired us all. In his memory, tonight we’ll have a look at Melotte 25.

Most of you will recognize this expansive open cluster as the V-shaped group that forms the “head” of Taurus – more commonly referred to as the Hyades. Hundreds of mixed magnitude stars are contained inside this fist-sized cluster. The brightest true member is Theta 2, followed by its slightly dimmer counterpart – Theta 1. You’ll find this pair easily with binoculars just south of orange Aldeberan, which is merely a foreground star in this stellar play. At roughly 150 light years away, it’s the closest open cluster known after the Ursa Major group. At 400 million years old, it moves away from us and perhaps carries the spirit of Sagan with it… “We are all just star stuff.”

Thursday, November 10 – Tonight no crater on the Moon will call louder than the mighty Copernicus – so let’s answer.

With its thick walls and central peak, it is wonderfully picturesque, but what’s around the mound? To the north is two part crater – Gay-Lussac. Look for its stunning rimae cutting diagonally away to the southwest. To the south is an even smaller double crater – Fauth. If you want a true challenge, power up to the max. Look inside of Copernicus on the east wall for the very tiny strike of crater A!

Friday, November 11 – A true observer was born on this day 1875. His name was Vesto Slipher, who spent some very quality time with the 60″ and 100″ telescopes on Mt. Wilson. Slipher was the first to photograph galaxy spectra and measure their redshifts, which led to the discovery of the expansion of the universe by Edwin Hubble.

Tonight let’s take a look at a galaxy as we head once again towards Andromeda and M31. Although the moonlight will prevent us from seeing great details, it is still quite amazing to know that we are able to see across 2.2 million light years. Containing over 300 billion stars, its one of the largest galaxies known. In 1912, Slipher analyzed it spectroscopically to discover its blue shift: “The magnitude of this velocity, which is the greatest hitherto observed, raises the question whether the velocity-like displacement might not be due to some other cause, but I believe we have at the moment we have no other interpretation for it. Hence we may conclude the Andromeda Nebula is approaching the solar system with a velocity of about 3000 kilometers per second.”

Saturday, November 12 – Wouldn’t we all have loved to have been there in 1949 when the first scientific observations were made with the Palomar 5-meter (200-inch) telescope? Or to have seen what Voyager 1 saw as it made its closest approach to Saturn on this date in 1980? Or even better, to have been around in 1833 – the night of the Great Leonid Meteor Shower! But this is here and now, so let’s make our own mark on the night sky as we view the Northern Taurid meteor shower.

Already making headlines around the world for producing extremely bright fireballs known as bolides, this particular stream belongs to debris left by periodic comet Encke. According to meteor experts Asher and Clube, 2005 could quite possibly be the year we pass through the “swarm” – a particularly rocky pocket of materials capable of producing these spectacular meteors. Although the Moon will greatly interfere with fainter members, a bolide can be spotted even through hazy cloud cover!

While you’re out, be sure to also keep watch for members of the Pegasid meteor shower, whose radiant is roughly near Square. This stream endures from mid-October until late November and used to be quite spectacular. Watch for the peak on November 17.

Sunday, November 13 – Today is the birthday of James Clerk Maxwell. Born in 1831, Maxwell was a leading English theoretician in electromagnetism and the nature of light. On this day in 1971, Mariner 9 becomes the first spaceprobe to orbit Mars.

Tonight let’s have a look at again at orbiting Mars. Depending on your observing time, perhaps you’ll catch the deep wedge of Syrtis Major punctuated by the Hellas Basin. For another, it might be the “moose antler” look of Mare Cimmerium or the red fields of Amazonis. Still others might catch the “fingers” of Mare Erythraeum reaching toward Chryse… No matter what time you look, it’s time well spent.

Until next week? May all your journeys be at light speed… ~Tammy Plotner

Posted on by Fraser Cain

Massive B-15A Iceberg Breaks Up

B-15A Iceberg breaking up. Image credit: ESA. Click to enlarge.
After five years of being the world’s largest free-floating object, the B-15A iceberg has broken into smaller pieces off Antarctica’s Cape Adare.

ESA’s Envisat satellite’s Advanced Synthetic Aperture Radar (ASAR) is sensitive to ice, and has been tracking the movement of the drifting ice object continuously since the beginning of this year. Its latest imagery reveals the bottle-shaped iceberg split into nine knife-shaped icebergs and a myriad of smaller pieces on 27-28 October, the largest being formed by fractures along the long axis of the original single iceberg.

Measuring – until last week – around 115 kilometres in length with an area exceeding 2500 square kilometres, the B-15A tabular iceberg had apparently run aground off Cape Adare, the northernmost corner of the Victoria Land Coast. This stranding appears to have led to flexing and straining which resulted in the break-up.

“The long knife-shaped pieces suggest the iceberg has split along existing lines of weakness within the iceberg,” says Mark Drinkwater of ESA’s Ocean and Ice Unit. “These would have been pre-existing fractures and crevasses in the ice shelf.”

These new icebergs, named by the US National Oceanic and Atmospheric Administration (NOAA) National Ice Center, will retain their parent’s title: the three largest island-sized pieces have been called B-15M, B-15N and B-15P.

B-15A was the largest remaining section of the even larger B-15 iceberg that calved from the nearby Ross Ice Shelf in March 2000 before breaking up into smaller sections off McMurdo Island.

Since then its B-15A section drifted into McMurdo Sound, where its presence blocked ocean currents and led to a build-up of sea ice that decimated local penguin colonies, deprived of open waters for feeding. During the spring of this year prevailing currents took B-15A slowly past the Drygalski ice tongue. A full-fledged collision failed to take place, but a glancing blow broke the end off Drygalski in mid-April.

The iceberg sailed on to have a less-destructive close encounter with the Aviator Glacier ice tongue at Lady Newnes Bay before becoming stranded off Cape Adare in mid-October.

Radar monitoring of Antarctic ice
ASAR is extremely useful for tracking changes in polar ice. ASAR can peer through the thickest polar clouds and work through local day and night. And because it measures surface texture, the instrument is also extremely sensitive to different types of ice – so the radar image clearly delineates the older, rougher surface of icebergs from surrounding sea ice, while optical sensors simply show a continuity of snow-covered ice.

Envisat’s ASAR instrument monitors Antarctica in two different modes: Global Monitoring Mode (GMM) provides 400-kilometre swath one-kilometre resolution images, enabling rapid mosaicking of the whole of Antarctica to monitor changes in sea ice extent, ice shelves and iceberg movement.

Wide Swath Mode (WSM) possesses the same swath but with 150-metre resolution for a detailed view of areas of particular interest.

ASAR GMM images are routinely provided to a variety of users including the National Ice Center, responsible for tracking icebergs worldwide.

Original Source: ESA News Release

Posted on by Fraser Cain

Landmarks on Titan

Cassini image of Titan with place names. Image credit: NASA/JPL/SSI. Click to enlarge.
Like an ancient mariner charting the coastline of an unexplored wilderness, Cassini’s repeated encounters with Titan are turning a mysterious world into a more familiar place.

During a Titan flyby on Oct. 28, 2005, the spacecraft’s narrow-angle camera acquired multiple images that were combined to create the mosaic presented here. Provisional names applied to Titan’s features are shown; an unannotated version of the mosaic is also available.

The mosaic is a high resolution close-up of two contrasting regions: dark Shangri-La and bright Xanadu. This view has a resolution of 1 kilometer (0.6 mile) per pixel and is centered at 2.5 degrees north latitude, 145 degrees west longitude, near the feature called Santorini Facula. The mosaic is composed of 10 images obtained on Oct. 28, 2005, each processed to enhance surface detail. It is an orthographic projection, rotated so that north on Titan is up.

The Cassini-Huygens mission is a cooperative project of NASA, the European Space Agency and the Italian Space Agency. The Jet Propulsion Laboratory, a division of the California Institute of Technology in Pasadena, manages the mission for NASA’s Science Mission Directorate, Washington, D.C. The Cassini orbiter and its two onboard cameras were designed, developed and assembled at JPL. The imaging operations center is based at the Space Science Institute in Boulder, Colo.

For more information about the Cassini-Huygens mission visit http://saturn.jpl.nasa.gov. The Cassini imaging team homepage is at http://ciclops.org.

Original Source: NASA/JPL/SSI News Release

Posted on by Fraser Cain

Inmarsat Launch Delayed

Artist illustration of Inmarsat 4. Image credit: Inmarsat. Click to enlarge.
The launch Inmarsat-4 F2, one of the largest and most powerful communications satellites ever built has been reschedule for Tuesday 8 November.

The six-tonne UK-built craft is due to be lofted by a Zenit-3SL rocket from a floating platform in the Pacific Ocean. It should have flown on Saturday but a software glitch led to an automated halt in the countdown sequence. Flight controllers say they are now happy to go for a Tuesday launch after investigating the technical problem.

Lift-off is now scheduled at the opening of a 29-minute window at 1407 GMT. Inmarsat-4 F2 is the second of three satellites designed to improve global communications systems.

The first satellite, which covers most of Europe, Africa, the Middle East, Asia and the Indian Ocean, was launched from Cape Canaveral in March. The second will improve and extend communications across South America, most of North America, the Atlantic Ocean and part of the Pacific Ocean.

The two satellites will support the London-based sat-com Inmarsat company’s global broadband network, BGan.

Their onboard technology is designed to allow people to set up virtual offices anywhere around the world via high-speed broadband connections and new 3G phone technology. The spacecraft, each the size of a London bus, should continue functioning for about 15 years. They were built largely at the EADS-Astrium facilities in Stevenage and Portsmouth, UK.

The Inmarsat-4 F2 is going up from waters close to Kiritimati (Christmas Island) on the equator.

It is using the innovative Sea Launch system, which employs a converted oil drilling platform as a launch pad. It is towed into position from its California base.

Original Source: BNSC News Release

Posted on by Fraser Cain

ESO Image of Robert’s Quartet

Robert’s Quartet. Image credit: ESO. Click to enlarge.
ESO PR Photo 34a/05 shows in amazing details a group of galaxies known as Robert’s Quartet [1]. The image is based on data collected with the FORS2 multi-mode instrument on ESO’s Very Large Telescope.

Robert’s Quartet is a family of four very different galaxies, located at a distance of about 160 million light-years, close to the centre of the southern constellation of the Phoenix. Its members are NGC 87, NGC 88, NGC 89 and NGC 92, discovered by John Herschel in the 1830s. NGC 87 (upper right) is an irregular galaxy similar to the satellites of our Milky Way, the Magellanic Clouds. NGC 88 (centre) is a spiral galaxy with an external diffuse envelope, most probably composed of gas. NGC 89 (lower middle) is another spiral galaxy with two large spiral arms. The largest member of the system, NGC 92 (left), is a spiral Sa galaxy with an unusual appearance. One of its arms, about 100,000 light-years long, has been distorted by interactions and contains a large quantity of dust.

The quartet is one of the finest examples of compact groups of galaxies. Because such groups contain four to eight galaxies in a very small region, they are excellent laboratories for the study of galaxy interactions and their effects, in particular on the formation of stars.

Using another set of VLT data also obtained with FORS2, astronomers [2] were able to study the properties of regions of active star formation (“HII regions” [3]) in the sister members of Robert’s Quartet. They found more than 200 of such regions in NGC 92, with a size between 500 and 1,500 light-years. For NGC 87, they detected 56 HII regions, while the two other galaxies appear to have far fewer of them. For NGC 88, however, they found two plume-like features, while NGC 89 presents a ring of enhanced stellar activity. The system is thus clearly showing increased star formation activity, most probably as the result of the interaction between its members. The sisters clearly belong to a perturbed family.

The quartet has a total visual magnitude of almost 13, i.e. it is about 600 times fainter than the faintest object that can be seen with the unaided eye. The brightest member of the group has a magnitude of about 14. On the sky, the four galaxies are all within a circle of radius of 1.6 arcmin, corresponding to about 75,000 light-years.

Notes
[1]: The group of galaxies was known as a Compact Group since 1977 by J.A. Rose, under the designation Rose 34. Robert’s Quartet is also known under the less poetic name of AM 0018-485 from the Catalogue of Southern Peculiar Galaxies and Associations, compiled in 1987 by astronomers Halton “Chip” Arp and Barry Madore. But who is Robert then? As discovered by Australian amateur astronomer Mike Kerr, Arp and Madore named Robert’s Quartet after Robert Freedman who generated many of the updated positions of galaxies in the catalogue. The astronomers clearly had a very good sense of humour as the catalogue also contains a system of galaxies called Wendy (ESO 147- 8; for Wendy Freedman) and another called the Conjugal galaxy (ESO 384- 53)!

[2]: The astronomers are S. Temporin (University of Innsbruck, Austria), S. Ciroi and P. Rafanelli (University of Padova, Italy), A. Iovino (INAF-Brera Astronomical Observatory, Italy), E. Pompei (ESO), and M. Radovich (INAF-Capodimonte Astronomical Observatory, Italy). (The article describing this result is available in PDF format at http://www.ast.cam.ac.uk/%7Esb2004/posters/files/Temporin.pdf)

[3]: The radiation of young hot stars embedded in an interstellar cloud is able to heat the surrounding gas, resulting in the apparition of an emission nebula that shines mostly in the light of ionized hydrogen (H) atoms. Such nebulae are therefore often referred to as “HII regions”. The well-known Orion Nebula is an outstanding example of that type of nebula.

Original Source: ESO News Release