Posted on by Fraser Cain

DIRECTV Satellite Lofted From Sea Launch

Sea Launch Company today successfully delivered DIRECTV?s Spaceway F1 satellite to orbit, completing the launch of the heaviest commercial satellite to date. Early data indicate the spacecraft is in excellent condition.

The Sea Launch Zenit-3SL rocket lifted off at 12:31:30 am PDT (07:31:30 GMT), precisely on schedule, 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 6,080 kg (13,376 lb) Spaceway satellite into geosynchronous transfer orbit, on its way to a final orbital position of 102.8 degrees West Longitude. A ground station in South Africa acquired the spacecraft?s first signal less than an hour after liftoff, as planned.

The Boeing 702 model spacecraft, with a design life of 12 years, was manufactured at Boeing?s Satellite Development Center in El Segundo, Calif. It includes a flexible payload with a fully steerable downlink antenna that can be reconfigured on orbit to seamlessly address market conditions.

Following acquisition of the spacecraft?s signal, Jim Maser, president and general manager of Sea Launch, congratulated Boeing and DIRECTV. ?Successfully launching the heaviest commercial satellite to date is a tremendous achievement for everyone involved,? Maser said. It was extremely satisfying for us to provide another great launch for DIRECTV and for Boeing and we look forward to many more in the future. And, once again, our accomplished Sea Launch team has raised the bar ? not only for Sea Launch ? but also for the entire launch industry. We are all especially proud of this latest success. We are the commercial heavy weight champions of the world!?

Sea Launch Company, LLC, headquartered in Long Beach, Calif., and marketed through Boeing Launch Services (www.boeing.com/launch), 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: Sea Launch News Release

Posted on by Fraser Cain

Global Warming Could Be Risky for Satellites Too

Image credit: NASA
Climate change is widely attributed to the build-up of greenhouse gases, such as carbon dioxide, in the Earth’s atmosphere. However, scientists from the School of Engineering Sciences at the University of Southampton have shown that the impact of carbon dioxide is being felt in space too.

Dr Hugh Lewis from the School will present a paper to the Fourth European Conference on Space Debris at the European Space Operations Centre (ESOC) in Germany this week indicating that increasing levels of CO2 are causing the amount of space debris orbiting the Earth to increase faster than previously thought.

Whilst CO2 is causing a global rise in temperature at the Earth’s surface, it has the opposite effect in the upper part of the atmosphere known as the thermosphere. Here, in a region of space that contains the International Space Station and many other satellites, the temperature and the atmospheric density are falling rapidly.

Evidence from the Naval Research Laboratory in the USA suggests that the atmospheric density at these heights could be halved in the next 100 years. At first glance, this is good news for satellite operators: it will take longer for their satellites to re-enter the atmosphere. However, the research conducted at the University of Southampton in collaboration with QinetiQ shows that in the later half of this century satellites would be at greater risk from collisions with orbiting debris.

Collisions between objects orbiting the Earth can release as much energy as ten sticks of dynamite because of the enormous speeds involved, around ten kilometres per second. These events can subsequently produce hundreds of thousands of objects larger than 1cm – each one a collision risk to satellites and used rocket stages.

According to the research team’s initial predictions a process known as ‘collision cascading’ – where the number of collisions in orbit increases exponentially – could occur much more quickly in the region of space between 200 km and 2,000 km above the Earth in response to rising CO2 levels. Simulations of a ‘business as usual’ scenario, where satellites are launched and destroyed at the rate they are now, show a 17 per cent increase in the number of collisions and a 30 per cent increase in the number of objects larger than 1cm by the end of the 21st century.

Dr Lewis stresses that steps are already being taken to diminish the threat posed by orbiting debris. The Inter-Agency Space Debris Coordination Committee (IADC), an international governmental forum that coordinates activities related to the issues of debris in space, has produced a set of guidelines that identify mitigation options. Whilst Dr Lewis’ research has implications for these guidelines, he believes that they will remain effective measures: ‘We are only now beginning to understand the impact that polluting the atmosphere is having on space, but our knowledge of the problems posed by space debris is reliable,’ he commented.

The research was undertaken by Dr Lewis, with Dr Graham Swinerd and Charlotte Ellis of the School of Engineering Sciences, and Dr Clare Martin of QinetiQ.

Original Source: University of Southampton News Release

Posted on by Fraser Cain

What’s Up This Week – Apr 25 – May 1, 2005

Image credit: NOAO/AURA/NSF
Monday, April 25 – Today marks the 15th anniversary of the deployment of Hubble Space Telescope. While everyone in the astronomical community is well aware of what this magnificent telescope “sees”, did you know that you can see it with just your eyes? The HST is a satellite that can be tracked and observed. Visit Heaven’s Above and enter your location. This page will provide you with a list of visible passes for your area. Although you can’t see details of the scope itself, it’s great fun to track with binoculars or see the Sun glinting off its surface in a scope.

Before the Moon rises tonight, let’s use our binoculars and telescopes to hunt down one of the best globular clusters for the northern hemisphere – M3. You can locate it easily by identifying last week’s study stars, Cor Caroli and Arcturus. Sweep your binoculars in a line between the two and you will discover this ancient beauty about halfway between the pair just east of Beta Comae. The more aperture you use – the more stars you will resolve.

Discovered by Charles Messier on May 3, 1764, this ball of approximately a half million stars is one of the oldest formations in our galaxy. At around 35-40,000 light years away, this awesome globular cluster spans about 220 light years and is believed to be as much as 10 billion years old. To get a grasp on that concept – our own Sun is less than half that age!

Keep a watch on the skies tonight as the Mu Virginid meteor shower reaches its peak at 7 to 10 per hour. Although the rising Moon will hamper observations, you still might catch one of these medium speed meteors radiating from a point near the constellation of Libra.

Tuesday, April 26 – This morning Mercury will reach its greatest western elongation. Southern hemisphere views are highly favoured for this apparition, and you may spot the swift inner planet just before dawn about a handspan above the east/northeast horizon.

On this date in 1920, the Shapely-Curtis debate raged in Washington on the nature and distance of spiral nebula. Shapely claimed they were part of one huge galaxy to which we all belonged, while Curtis maintained they were distant galaxies of their own. Thirteen years later on the same date, Arno Penzias was born. He went on to become a Nobel Prize winner for his part in the discovery of the cosmic microwave background radiation through a simple horn antenna. His discovery helped further our understanding of cosmology in ways that Shapely and Curtis could have never dreamed.

Before the Moon rises tonight, why not take the telescopic challenge to view one of the largest and finest of face-on spiral galaxies? Located about a fist’s width east of last week’s study – Mizar and Alcor – you will find the large, diffuse M101 to be easily within range of the average mid-sized scope. At magnitude 9, you can spot it in larger binoculars, but will require at least a 10″ scope to detect its knotted arms.

For all of Europe and northeastern Africa, the Moon will occult Antares tonight. Be sure to check IOTA for precise times in your area. On this same universal date, it will also occult bright Sigma Scorpii for those in northwestern Australia.

Wednesday, April 27 – Let’s return to the binoculars and small telescopes tonight to find a fantastic galactic cluster known as the M67. Easily located by either going about a fist’s width south of the M44 or a thumb’s width west of Alpha Cancri – this rich, 2500 light year distant open cluster has a stellar population unlike any other. Located about 1500 light years above the plane of the galaxy, the M67 defies the rules by residing in an area not known for galactic clusters – and double defies them by containing population stars similar to a globular cluster. These stars are an indicator of great age, and the M67 may very well be near 10 million years old. For very small binoculars, this beautiful open cluster will appear almost galaxy-like, while progressively larger instruments will resolve it completely.

Thursday, April 28 – Now is your chance to get a first look at the returning Venus. Immediately after sunset, look for it very low on the west/northwest horizon. Try using binoculars to assist you.

Today was a very busy day in astronomy history. Newton published his Principia in 1686 on April 28. In 1774, Francis Baily was born – who went on to revise star catalogs and explain the phenomenon at the beginning and ending of a total solar eclipse which we know as “Baily’s Beads”. 1900 saw the birth of Jan Hendrick Oort, who quantified the Milky Way’s rotation characteristics and envisioned the vast, spherical area of comets outside our solar system that we call the Oort Cloud. Last, but not least was the birth of Bart Jan Bok in 1906 who studied the structure and dynamics of the Milky Way.

Tonight let’s take a look at a visitor from the Oort Cloud, comet 9P/Temple 1. Located just north of Epsilon Virginis, this 10th magnitude comet could be within range of large binoculars, but I would suggest a telescope since there will be many nearby galaxies that could resemble a cometary signature in such a wide field. Even at the eyepiece, this comet will strongly resemble a faint, face-on spiral – but don’t worry – it’s by far brighter than anything nearby. As 9P/Temple 1 is nearing it’s closest approach to the Earth, this will be an outstanding comet to watch in the weeks ahead. Think “Deep Impact”….

For skywatchers, no equipment is necessary to enjoy the Alpha Bootid meteor shower. Pull up a comfortable seat and face orange Arcturus as it climbs the sky in the east. These slow meteors have a fall rate of 6 to 10 per hour and leave very fine trails, making an evening of quiet contemplation most enjoyable.

Friday, April 29 – The Moon is at perigee, its closest approach to Earth – and as luck would have it, reaches maximum libration at 21:00 UT, tipping the north pole our way. If this doesn’t sound very exciting, think of SMART-1 currently up there looking for eternal sunlight! Although the Moon won’t rise until around local midnight, if you’re up late have a go at extreme northern features like Peary, Byrd, Gioja, Main, Challis and Scoresby.

Saturday, April 30 – Frederich Gauss was born on this day in 1777, Known as the “Prince of Mathematics”, Gauss contributed to the field of astronomy in many ways – from computing asteroid orbits to inventing the helioptrope. Out of Gauss’ many endeavors, he is most recognized for his work in magnetism. We understand the term “gauss” as a magnetic unit – a refrigerator magnet carries about 100 gauss while an average sunspot might go up to a 4000. On the most extreme ends of the magnetic scale, the Earth produces about 0.5 gauss at its poles, while a magnetar can produce as much as 10 to the 15th power in gauss units!

While we cannot directly observe a magnetar, those living in the Southern Hemisphere can view a region of the sky where magnetars are known to exist – the Large Magellanic Cloud. Located in the constellation of Dorado, this unaided eye gem is visible even during full moonlight. Stuffed with wonderful features such as the “Tarantula Nebula” – the largest diffuse nebula known in the Universe – and many star clusters, I urge you to get out your telescopes and binoculars and explore…

For southwestern Europe, the Moon will occult 4.5 magnitude star, 59 Saggitarius, on this universal date. Please check the IOTA webpage for details specific to your area.

Sunday, May 1 – On this day in 1949 Gerard Kuiper discovered Nereid, a satellite of Neptune. If you’re up before dawn, you can easily find Neptune less than 2 degrees northwest of bright Mars. While it can be see in binoculars as a bluish “star”, it takes around a 150mm telescope and some magnification to resolve its disc. Today’s imaging technology can even reveal its moons!

Tonight will mark the peak of the Phi Bootid meteor shower whose radiant is near the constellation of Hercules. While the best time to view a meteor shower is around 2:00 a.m. local time, you will have best success watching for these meteors during the late evening before moonrise. The average fall rate is about 6 per hour.

Keep those scopes warm – dark skies are on their way back again! May all your travels be at Light Speed…. ~Tammy Plotner

Posted on by Fraser Cain

Expedition 10 Lands Safely

After traveling more than 78 million miles aboard the International Space Station, Expedition 10 Commander and NASA ISS Science Officer Leroy Chiao and Flight Engineer Salizhan Sharipov returned to Earth today. With them was European Space Agency Astronaut Roberto Vittori, who had spent eight days aboard the orbiting complex doing research.

After a flawless descent by the ISS Soyuz 9 spacecraft, Chiao, Sharipov and Vittori landed on target in north-central Kazakhstan, about 53 miles (85 kilometers) northeast of Arkalyk, at 5:08 p.m. CDT. Recovery forces arrived at the site within minutes of the touchdown. The area was saturated from recent rains and melting winter snow, so the first members of the recovery team to reach the scene decided to fly the crew to Arkalyk to meet with remaining members of the recovery team.

The crew’s friends and families are expected to greet them upon their arrival at Star City, Russia, about eight hours after landing. Chiao and Sharipov will remain in Star City for a few weeks of post-flight debriefings and medical exams before returning to Houston in mid-May.

Chiao and Sharipov spent 192 days, 19 hours and 2 minutes in space. They launched on Oct. 13, on the same Soyuz spacecraft that brought them home. For six months, the pair maintained systems and conducted scientific research onboard the Station.

Among their accomplishments on the Station was replacing critical hardware in the Joint Quest Airlock, repairing U.S. spacesuits, submitting a scientific research paper on ultrasound use in space and voting for the first time in an American Presidential election from space. They completed two spacewalks, including experiment installation and tasks that prepared the Station for the arrival of a new European cargo ship next year.

Aboard the Station, the Expedition 11 crew, Commander Sergei Krikalev and Flight Engineer and NASA Station Science Officer John Phillips, are beginning a six-month mission that will include the resumption of Space Shuttle flights and two spacewalks from the Station. Expedition 11 is scheduled to return to Earth on Oct. 7, 2005.

Krikalev and Phillips will have light duty for the next three days as they rest after completing a busy handover period. For the past week, they have been learning about Station operations from the two men who called the ship home since October. Chiao and Sharipov briefed Krikalev and Phillips on day-to-day operations and gave them hands-on opportunities at Station maintenance: Chiao and Phillips restored functionality of the Quest for future spacewalks and practiced operating the Canadarm2 robotic arm.

Information on the crew’s activities aboard the Station, future launch dates, as well as Station sighting opportunities from anywhere on the Earth, is available on the Internet at:

http://www.nasa.gov/station

Original Source: NASA News Release

Posted on by Fraser Cain

Spitzer Discovers Early Galaxy Forming Region

The Spitzer Space Telescope (SST) is the fourth and final instrument in NASA’s Great Observatories series. The SST followed the Hubble Space Telescope (HST), Chandra X-Ray, and Compton Gamma Ray Observatories into space on August 25th, 2003. Placed in Earth-trailing heliocentric (solar) orbit, and working under a 2.5 plus year charter within NASA’s Origins Program, the SST revealed first public light in May of 2004 – giving the world a spectacular infrared view of the face-on grand spiral galaxy M51 in Canes Venatici.

Lord Rosse first described M51 as a “spiral nebula” in 1845. It wasn’t until Edwin Hubble resolved faint variable stars within another “M” – M31 – that M51 and other “spiral nebulae” achieved a rank equal with our own Milky Way – Galaxy!

But to name a thing is not to explain it. One of the toughest things to explain about anything is “How did it get to be what it is?”

Well before the release of SST’s image of M51, astronomers had already been given a “heads-up” on a rare instance of a class of distant objects in the heavens – an expansive region of gas and dust glowing faintly yet unattended by stellar light – just the kind of study that could revolutionize the way astronomers understand galaxy formation. NASA’s Origins Program had made a major hit and now the problem was to advance the runner to home using other sources of data…

In a paper entitled “Discovery of a Large ~ 200kpc Gaseous Nebula at z=~2.7 with the Spitzer Space Telescope” (published March 29, 2005), astrophysicist Arjun Dey of the National Optical Astronomy Observatory (NOAO) and colleagues from other organizations (including the SST operations center at the Jet Propulsion Laboratory) pulled together data from across the lower half of the em spectrum – radio to visible light – to paint a picture of early galaxy cluster formation associated with this excited (and exciting) region of dust and gas located some 11.3 BLY’s away in time and space.

In the words of the team, “We report the discovery of a very large spatially extended nebula associated with a luminous mid-infrared source.” To you and me that means they discovered “a long ago, and far away womb of early galactic birth”.

The object (SST24 J1434110+331733) was originally mapped using the SST’s MIPS and IRAC detectors during a mid-infrared survey of spring?s constellation Bootes in late January 2004. After data reduction by JPL personnel, it became clear that SST24 could offer some extremely significant insights into that mysterious era of galactic unfolding when young galaxies are ensconced in the stuff of star formation. But to penetrate this stuff would require expanding the picture of the region using light from across the em spectrum.

In part the need to have other looks at SST24 was driven by the limited aperture of SST’s 0.84 meter mirror and those long wavelengths associated with infrared light. At best, the SST revealed the central third of the nebulosity. (Instruments aboard the SST are limited to 6 arc seconds detail resolution.) Three onboard detectors (the Infrared Array Camera -IRAC, Infrared Spectrograph – IRS, and Multiband Imaging Photometer for Spitzer – MIPS) image and analyze infrared light in the mid to far-infrared wavelengths (3.6-160 micrometers).

Although light observed using the three SST instruments mostly originates from “warm” objects (gases and dust), light from near-optical sources can also be seen after expansionary redshift over vast distances. Interestingly, one particular bright line in that same “near-optical light” was first flagged for astronomical use by astrophysicist Lyman Spitzer – namesake of the SST itself – one of the leading 20th century proponents of infrared astronomy.

Joined with data from other instruments, Dey and his team put together a compelling case for an active galactic nuclei (AGN) within SST24. If verified such an AGN would demonstrate that black holes play an important role in early galaxy evolution. Such an example may very well revolutionize our understanding of galaxy formation by making AGN’s more the cause – rather than the effect – of galaxy group formation…

Visual data used by the team associated with SST24 was collected using the 4m and 2.1m telescopes of the NOAO in Kitt Peak, Arizona. These instruments improved SST resolution by a factor of almost eight times. Other data available in optical light extended the picture of SST24’s energy output. During May and June of 2004, spectrographic information on SST24 (along with foreground and background objects) was gathered in finely-tuned and precisely oriented 1 arc second strips through the 10 meter Keck I instrument on Mauna Kea, Hawaii.

From the paper’s abstract, “The bright mid-infrared source was first detected in observations made using the Spitzer Space Telescope. Existing broad-band imaging data from the NOAO Deep Wide-Field Survey revealed the mid-infrared source to be associated with a diffuse, spatially-extended, optical counterpart… Spectroscopy and further imaging … reveals the optical source is almost purely line-emitting nebula with little if any, detectable diffuse continuum emission.”

Typically, mature galaxies display a full spectrum of light generated by blackbody radiation from stellar photospheres. Such broadband spectra are usually reinforced by narrow, bright emission lines associated with atomic excitation. But SST24’s spectrum is dominated by a single narrow band of radiation. That band – though redshifted some 3.7 times due to 11.3 BLY’s of recession – associates with the “Lyman Alpha” frequency emitted by hydrogen gas. Usually such Lyman-alpha clouds irradiate by stimulation from distant background quasars. But in the case of SST24, another mechanism may be involved – a black hole source within the nebula itself.

In piecing together SST24’s structure, the science team determined that its AGN is offset from the center of the cloud by nearly one-tenth the cloud’s full extent. Although it is unclear what impact this offset has on galaxy formation, the fact of it must be incorporated into how we model galaxy group formation in the future.

Spectrographic shifts in Lyman alpha light also indicate that the central 100 KLY region of SST24 slowly revolves and contains the mass equivalent of some 6 trillion suns – some 5x that of our own Milky Way and Whirlpool (M51) galaxies combined. SST24 includes a region of space easily encompassing the entire Milky Way and all twelve satellite galaxies.

But SST24 is not totally devoid of star formation. The team reports that “a young star forming galaxy lies near the northern end of the nebula.” That galaxy is reddened by dust, has the same redshift as the Lyman-alpha radiation, plus broad-band radiation associated with star formation. This galaxy gives no indication of having an AGN. Because of this we may soon learn that AGN?s may not play a role essential to the formation of all galaxies.

Although radio-frequency examination of SST24 is difficult (due to resolution issues at long wavelengths), the team points out that its mid-infrared to radio-wave density ratio, “shows remarkable similarity to starburst galaxies…” For this reason parts of SST24 mat be passing through an era of rapid stellar evolution that could quickly lead to the revelation of a full-blown galaxy rich with luminous breeder stars…

SST24 is not the only Lyman-alpha cloud ever detected, but those few discovered are thought extraordinary by the science team: “The rarity of these >100kpc lyman-alpha clouds, their association with powerful AGN and galaxy overdensities, and their energetics all suggest that these regions are the formation sites of the most massive galaxies. If so, understanding the physical conditions and energetics of these systems can provide important insights into the massive galaxy formation process.”

Written by Jeff Barbour

Posted on by Fraser Cain

Wallpaper: 15 Years of Hubble

When NASA’s Hubble Space Telescope was launched in 1990, astronomers anticipated great discoveries, ranging from finding black holes to looking back billions of years toward the beginning of time. Now, 15 years later, the versatile telescope continues to deliver exciting new science, including helping to prove the existence of dark energy, tracing enigmatic gamma-ray bursts to distant galaxies, and sampling the atmospheres of far-flung planets. To celebrate Hubble’s 15th anniversary, new breathtaking images will be released of a majestic spiral galaxy teeming with newborn stars and an eerie-looking spire of gas and dust.

The new image of the well-known spiral galaxy M51 (known as the Whirlpool Galaxy), showcases a spiral galaxy’s classic features, from its curving arms, where newborn stars reside, to its yellowish central core, a home for older stars. A feature of considerable added interest is the companion galaxy located at the end of one of the spiral arms. The new photograph of the Eagle Nebula shows a tall, dense tower of gas that is being sculpted by ultraviolet light from a group of massive, hot stars.

The pictures are among the largest and sharpest views taken by Hubble. The images, taken by Hubble’s Advanced Camera for Surveys, are 20 times larger than a photograph taken by a typical digital camera. The new images are so sharp that they could be enlarged to billboard size and still retain the stunning details.

Mural-sized images of both celestial objects will be unveiled at 100 museums, planetariums, and science centers across the country, from Guam to Maine. The 4-foot-by-6-foot image of M51 and the 3-foot-by-6-foot photograph of the Eagle Nebula will be on display at all the sites. A list of these sites is available on http://hubblesite.org/about_us/unveiling.shtml.

If you cannot see the pictures at a museum or planetarium, catch them on the new “Gallery” at http://hubblesite.org/gallery. Views of M51 and the Eagle Nebula, along with more than 1,000 other glorious Hubble images, can be savored from the comfort of your home. If you want some Hubble pictures to hang in your home, then go to “Astronomy Print Shop.” Choose from a list of Hubble images that are specially formatted for printing. Select the image, the size you want (from 4 inches by 6 inches to 16 inches by 20 inches), and download it. Then take it to your favorite print shop to make a copy suitable for framing.

Looking for information about Hubble and its discoveries that is written for children? Then go to the Amazing Space education website at http://amazing-space.stsci.edu. Children can read a story tailored just for them on Hubble’s 15th anniversary, entitled “Hubble’s Picture Book of the Universe.” The story is under “The Star Witness,” a section of the website offering Hubble news written for children. Children also can take a journey through the eras of telescope history by going to Amazing Space’s “Online Explorations” and clicking on “Telescopes from the Ground Up.” This newest addition to Amazing Space traces the fascinating history of telescope evolution from the technological advancements to the people who made the telescopes.

Hubble was placed into Earth-orbit on April 25, 1990. For the first time, a large telescope that sees in visible light began orbiting above Earth’s distorting atmosphere, which blurs starlight and makes images appear fuzzy. Astronomers anticipated great discoveries from Hubble. The telescope has delivered as promised and continues serving up new discoveries. During its 15 years of viewing the universe, the telescope has taken more than 700,000 snapshots of celestial objects such as galaxies, dying stars, and giant gas clouds, the birthplace of stars. Astronomers are looking forward to more great discoveries by Hubble.

Original Source: Hubble News Release

Posted on by Mark Mortimer

Book Review: Night Sky Atlas

Of course the stars have been with people since people have been on Earth. Wandering along the ecliptic in an annual cycle allowed those with good memories to see the stars arc across the night sky, disappear and then reappear perhaps months later. Those with a good imagination then came along and, perhaps after reviewing the shapes of clouds, went on to name groups of stars; Leo the lion, the Big Dipper and Orion the hunter. These names represent the basic coordinates in star maps and also the basic orientation for astronomers when discussing their latest night time observations. A star map is essential for quickly learning this built up information and, with its knowledge, provides a common basis for discussing night time delights.

Robin Scagell in his book provides maps of the night skies. First he outlines the coordinate system; orbits, declination, right ascension, and ecliptics. Maps in semi-circular segments then illustrate the stars. A group of six illustrate the northern hemisphere. One pair gives a north and south view for a January evening at about midnight and with a false horizon drawn for a number of latitudes. Another shows May and a third pair shows September. Three other pairs show the segments if viewed from the southern hemisphere. These maps are quite small about 10 cm in diameter and show the constellations, names of significant stars and a washed area that represents the contribution from the Milky Way.

The main value of this book is the use of these guide maps with following detailed maps. Much like a road map that has blow ups with greater details, each of the semi-circular segments has four or five links to higher fidelity maps. And these higher fidelity maps are the purpose for the book’s larger format as these are each also a semicircle of diameter about 30 cm. Now it’s a bit curious as to how semi-circles divided to semi-circles, perhaps there’s a fair amount of overlap. Anyway these higher fidelity maps each appear twice. The first shows stars in black on a white background as well as constellation boundaries. The second is a photo-realistic image (stars as white dots on a black background) which show the night sky as a viewer would see it. In total there are eight pairs of these higher fidelity maps.

Following the maps are sections on what to see, sort of like a tourist’s map for a city. The moon gets large attention with lots of clear, fine scale photographs. Four, full page quarter circle maps provide place names on a shaded relief. The sun and each planet also have write-ups and pictures though, not surprisingly, the amount of information is inversely proportional to the distance from Earth. Of course these have no maps as no amateur astronomer has equipment able to discern geographic features except perhaps a little of Mars (the ice caps).

The final chapter of the book does get back into maps. Fifty of the most important constellations (presumably according to the author) have a small map (about 10cm by 10cm) alongside a write-up of the interesting features; galaxies, nebulae and other deep sky objects. This is a particularly good chapter with in-depth information much as a large city map presents details on tourist sections and popular sites. Once centring a constellation in the eyepiece of your favourite telescope, using this map quickly allows a viewer to identify features as well as their relative positions. Hence the constellation Pegasus becomes the stars Sadalbari, Matar and Enif. And thus the learning of the night sky via the maps in this book, quickens.

As an atlas this book is good but not great. I put it to the test, went out, got my bearings using the Big Dipper and then looked in the book. Note I’m no expert. However, this being April made the large scale maps very difficult. The nearest map (May at Midnight) did not do my view justice. Going to the higher fidelity maps was no help as I couldn’t get an appreciation of the scale. However, starting with the constellation Big Dipper (or Ursa Major), I was able to learn more about the local sky group. More large scale maps would have helped. Also, in looking at the higher fidelity maps, I only referred to the high contrast, black on white views; never the photo-realistic ones. Nevertheless this book is an effective night sky atlas for those looking without aid or those using binoculars or small telescopes.

Travelling to visit the grandparents, planning for a vacation or going out to view stars at night all have much better results when undertaken with an appropriate map. Robin Scagell in his book, Night Sky Atlas provides the guidance for viewing the moon, planets, stars and other deep sky objects. So don’t get lost in the big, diamond endowed, velvet cloth that descends over us every evening, get this book and travel away.

See more reviews or order a copy online from Amazon.com

Review by Mark Mortimer.

Posted on by Fraser Cain

Hot Spots Seen on Neutron Stars

Thanks to data from ESA?s XMM-Newton spacecraft, European astronomers have observed for the first time rotating ?hot spots? on the surfaces of three nearby neutron stars.

This result provides a breakthrough in understanding the ?thermal geography? of neutron stars, and provides the first measurement of very small-sized features on objects hundreds to thousands light-years away. The spots vary in size from that of a football field to that of a golf course.

Neutron stars are extremely dense and fast-rotating stars mainly composed of neutrons. They are extremely hot when they are born, being remnants of supernovae explosions. Their surface temperature is thought to gradually cool down with time, decreasing to less than one million degrees after 100 000 years.

However, astrophysicists had proposed the existence of physical mechanisms by which the electromagnetic energy emitted by neutron stars could be funnelled back into their surface in certain regions. Such regions, or ?hot spots?, would then be reheated and reach temperatures much higher than the rest of the cooling surface. Such peculiar ?thermal geography? of neutron stars, although speculated, could never be observed directly before.

Using XMM-Newton data, a team of European astronomers have observed rotating hot spots on three isolated neutron stars that are well-known X-ray and gamma-ray emitters. The three observed neutron stars are ?PSR B0656-14?, ?PSR B1055-52?, and ?Geminga?, respectively at about 800, 2000 and 500 light-years away from us.

As for normal stars, the temperature of a neutron star is measured through its colour that indicates the energy the star emits. The astronomers have divided the neutron star surfaces into ten wedges and have measured the temperature of each wedge. By doing so, they could observe rise and fall of emission from the star?s surface, as the hot spots disappear and appear again while the star rotates. It is also the first time that surface details ranging in size from less than 100 metres to about one kilometre are identified on the surface of objects hundreds to thousands light-years away.

The team think that the hot spots are most probably linked to the polar regions of the neutron stars. This is where the star?s magnetic field funnels charged particles back towards the surface, in a way somehow similar to the ?Northern lights?, or aurorae, seen at the poles of planets which have magnetic fields, such as Earth, Jupiter and Saturn.

?This result is a first, and a key to understand the internal structure, the dominant role of the magnetic field treading the star interior and its magnetosphere, and the complex phenomenology of neutron stars,? says Patrizia Caraveo, of the Istituto Nazionale di Astrofisica (IASF), Milan, Italy.

?It has been possible only thanks to the new capabilities provided by the ESA XMM-Newton observatory. We look forward to applying our method to many more magnetically isolated neutron stars,? concludes Caraveo.

However, there is still a puzzle for the astronomers. If the three ?musketeers? are predicted to have polar caps of comparable dimensions, why then are the hot spots observed in the three cases so different in size, ranging from 60 metres to one kilometre? What mechanisms rule the difference? Or does this mean some of the current predictions on neutron stars magnetic fields need to be revised?

The result, by Andrea De Luca, Patrizia Caraveo, Sandro Mereghetti, Matteo Negroni (IASF) and Giovanni Bignami of CESR, Toulouse and University of Pavia, is published in the 20 April 05 issue of the Astrophysical Journal (http://www.journals.uchicago.edu/ApJ, vol. 623:1051-1069).

Original Source: ESA News Release

Posted on by Fraser Cain

Earthquake Should Show a Gravity Scar

Image credit: ESA
A new ESA study predicts that the devastating Sumatran earthquake, which resulted in the tragic tsunami of 26 December 2004, will have left a ?scar? on Earth?s gravity that could be detected by a sensitive new satellite, due for launch next year.

The Sumatran earthquake measured 9 on the Richter scale and caused widespread devastation and death when it struck unexpectedly late last year. Thankfully, earthquakes of this magnitude are rare events, taking place perhaps once every two decades.

Seismological data suggests that, during the event, the seafloor on either side of a fault line running for 1000 km along the bottom of the Indian Ocean dramatically changed height, producing a ledge, 6 metres high. Such a large-scale movement will change the gravitational field of the Earth. Roberto Sabadini and Giorgio Dalla Via, University of Milan, and colleagues have calculated this change. They found that the Earth?s gravity altered, in an instant, by as much as is expected from six years’ worth of melting at the Patagonian Ice Fields in southernmost South America.

It may seem surprising that Earth?s gravity is not equally strong at all points of the globe. Instead, it varies by a small fraction due to the presence of such things as mountains or deep ocean trenches. The tides and ocean circulation patterns also affect the gravity, as does the rotation of the Earth itself, which bulges out the planet?s equator and makes its diameter 21 kilometres wider than the pole-to-pole distance.

In order to measure the deviations from the average level of gravity, Earth scientists invented the concept of the geoid. This is a bit like a hi-tech version of ?sea level?, which is often used to give an absolute height measure. Today?s modern measurements need something more accurate, however.

The geoid is a hypothetical surface, on which the gravitational pull of the Earth is the same everywhere. It wraps itself around the Earth, moving away from the real surface when it is over areas of greater density and therefore stronger gravity. Over less dense regions, the geoid moves closer to the real surface.

When material is moved around, either instantaneously in an earthquake or gradually as in a melting ice field, the Earth?s gravity in the local region changes and so does the height of the geoid. In the Sumatran earthquake, Sabadini and Dalla Via found that the total geoid movement was some 18 mm ? a lot for a geoid!

ESA?s Gravity Field and Ocean Circulation Explorer (GOCE) is designed to sensitively investigate the gravitational field of the Earth from orbit. As the spacecraft passes over regions of stronger and weaker gravitational pull, it will bob up and down. Such deviations are far below the perceptible limits of humans but GOCE is equipped with a device called a gradiometer than can detect these ultra-subtle differences. By measuring the deviations in the geoid, scientists can gain a unique window into our planet.

?This work is at the frontier of geophysics and the perfect complement to seismology,? says Sabadini, ?Seismology is good for detecting the slip of earthquake faults and the location of the epicentre, geoid monitoring can determine how much mass is actually being moved around.?

It can also be used in the quest to understand climate change as ocean circulation also affects the geoid. Changes in climate, which in turn affect the ocean circulation pattern, will show up as a yearly change in the geoid. With so much to offer, the GOCE satellite is scheduled to launch in 2006. A paper on the Sumatran Earthquake by Roberto Sabadini, Giorgio Dalla Via, Masja Hoogland, Abdelkrim Aoudia is published in EOS, the journal of the American Geophysical Union.

Original Source: ESA News Release

Posted on by Fraser Cain

False Colour Titan

This false-color composite was created with images taken during the Cassini spacecraft’s closest flyby of Titan on April 16, 2005.

It was created by combining two infrared images (taken at 938 and 889 nanometers) with a visible light image (taken at 420 nanometers). Green represents areas where Cassini is able to see down to the surface. Red represents areas high in Titan’s stratosphere where atmospheric methane is absorbing sunlight. Blue along the moon’s outer edge represents visible violet wavelengths at which the upper atmosphere and detached hazes are better seen.

A similar false-color image showing the opposite hemisphere of Titan was created from images taken during Cassini’s first close flyby of the smoggy moon in October 2004 (see PIA06139). At that time, clouds could be seen near Titan’s south pole, but in these more recent observations no clouds are seen.

North on Titan is up and tilted 30 degrees to the right.

The images used to create this composite were taken with the Cassini spacecraft wide angle camera on April 16, 2005, at distances ranging from approximately 173,000 to 168,200 kilometers (107,500 to 104,500 miles) from Titan and from a Sun-Titan-spacecraft, or phase, angle of 56 degrees. Resolution in the images approximately 10 kilometers 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 team is based at the Space Science Institute, Boulder, Colo.

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

Original Source: NASA/JPL News Release