Posted on by Fraser Cain

Cassini Completes Fourth Titan Flyby

Although the Huygens probe has now pierced the murky skies of Titan and landed on its surface, much of the moon remains for the Cassini spacecraft to explore. Titan continues to present exciting puzzles.

This view of Titan uncovers new territory not previously seen at this resolution by Cassini’s cameras. The view is a composite of four nearly identical wide-angle camera images, all taken using a filter sensitive to wavelengths of infrared light centered at 939 nanometers. The individual images have been combined and contrast-enhanced in such a way as to sharpen surface features and enhance overall brightness variations.

Some of the territory in this view was covered by observations made by the Cassini synthetic aperture radar in October 2004 and February 2005. At large scales, there are similarities between the views taken by the imaging science subsystem cameras and the radar results, but there also are differences.

For example, the center of the floor of the approximately 80-kilometer-wide (50-mile) crater identified by the radar team in February (near the center in this image, see PIA07368 for the radar image) is relatively bright at 2.2 centimeters, the wavelength of the radar experiment, but dark in the near-infrared wavelengths used here by Cassini’s optical cameras. This brightness difference is also apparent for some of the surrounding material and could indicate differences in surface composition or roughness.

Such comparisons, as well as information from observations acquired by the visual and infrared mapping spectrometer at the same time as the optical camera observations, are important in trying to understand the nature of Titan’s surface materials.

The images for this composite view were taken with the Cassini spacecraft on March 31, 2005, at distances ranging from approximately 146,000 to 130,000 kilometers (91,000 to 81,000 miles) from Titan and at a Sun-Titan-spacecraft, or phase, angle of about 57 degrees. The image scale is 8 kilometers (5 miles) per pixel. Previous observations indicate that, due to Titan’s thick, hazy atmosphere, the sizes of surface features that can be resolved are a few times larger than the actual pixel scale.

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/SSI News Release

Posted on by Fraser Cain

Light Seen From Earliest Stars

UK and US astronomers have used the Spitzer Space Telescope and the Hubble Space Telescope to detect light coming from the first stars to form in some of the most distant galaxies yet seen. Speaking on Wednesday 6 April at the RAS National Astronomy Meeting in Birmingham, Dr. Andrew Bunker (University of Exeter) will discuss new evidence that the formation of the first galaxies may have got underway earlier than previously thought.

This observational work using infrared images from Spitzer Space Telescope is essential, since theoretical predictions for the history of star formation in the early Universe are highly uncertain. The team, led by Bunker and graduate student Laurence Eyles (University of Exeter), used Hubble Space Telescope data to identify remote galaxies that were suitable for further study. They then analysed archived images taken at infrared wavelengths with NASAs Spitzer Space Telescope.

These images, obtained as part of the Great Observatory Origins Deep Survey (GOODS) project and the Hubble Ultra Deep Field (UDF), covered a part of the southern sky known as the constellation of Fornax (the Oven). We used the images from the Hubble Ultra Deep Field to identify objects likely to be galaxies 95 per cent of the way across the observable Universe, explained Bunker. These images are our most sensitive picture of the Universe so far, and they enabled us to discover the faintest objects yet. Intervening gas clouds absorbed the light they emitted at visible wavelengths long before it reached Earth, but their infrared light can still be detected – and it is their infrared colours which led the researchers to believe that they lie at such immense distances.

Confirmation of their extreme remoteness was provided by the 10-metre Keck telescopes in Hawaii, the largest optical telescopes in the world. We proved these galaxies are indeed among the most distant known by using the Keck telescopes to take a spectrum, said Dr. Elizabeth Stanway (University of Wisconsin- Madison).

The Keck spectra showed that the galaxies have redshifts of about 6, which means they are so far away that light from them has taken about 13 billion years to reach us. Telescopes show them as they were when the Universe was less than a billion years old – eight billion years before the Earth and Sun formed.

The next step was to learn more about the stars within these most distant galaxies by studying new infrared images of this region of space taken by Spitzer. The Hubble images tell us about the new-born stars, but the new infrared images taken with the Spitzer Space Telescope give us extra information about the light that comes from older stars within these distant galaxies, said Laurence Eyles, who studied the Spitzer images of these objects as part of his research for a doctorate at Exeter.

This is very important, because it tells us that some of these galaxies are already 300 million years old when the Universe is very young. It could be that these were some of the first galaxies to be born, said Michelle Doherty (Institute of Astronomy, Cambridge). Using the Spitzer images, the team was able to weigh the stars in these galaxies by studying the starlight. It seems that in a couple of cases these early galaxies are nearly as massive as galaxies we see around us today, which is a bit surprising when the theory is that galaxies start small and grow by colliding and merging with other galaxies, said Dr. Mark Lacy (Spitzer Science Center).

The real puzzle is that these galaxies seem to be already quite old when the Universe was only about 5 per cent of its current age, commented Professor Richard Ellis of Caltech. This means star formation must have started very early in the history of the Universe – earlier than previously believed. The light from these first stars to ignite could have ended the Dark Ages of the Universe when the galaxies first turned on. It is also likely to have caused the gas between the galaxies to be blasted by starlight – the reionisation which has been detected in the cosmic microwave background by the WMAP satellite.

The results from WMAP and the Hubble Ultra Deep Field complement the new work done by Bunkers team with the Spitzer data. Taken together, they suggest that the Dark Ages ended sometime between 200 and 500 million years after the Big Bang, when the first stars were born.

A paper on these results has been submitted for publication in the Monthly Notices of the Royal Astronomical Society.

Original Source: RAS News Release

Posted on by Fraser Cain

Swift Measures the Distance to Two Blasts

The NASA-led Swift mission has measured the distance to two gamma-ray bursts — back to back, from opposite parts of the sky — and both were from over nine billion light years away, unleashed billions of years before the Sun and Earth formed.

These represent the mission’s first direct distance, or redshift, measurements, its latest milestone since being launched in November 2004. The distances were attained with Swift’s Ultraviolet/OpticalTelescope (UVOT).

The Swift science team said that these types of distance measurements will become routine, allowing scientists to create a map to understand where, when and how these brilliant, fleeting bursts of light are created.

“Swift will detect more gamma-ray bursts than any satellite that has come before it, and now will be able to pin down distances to many of these bursts too,” said Dr. Peter Roming, UVOT Lead Scientist at Penn State. “These two aren’t distance record-breakers, but they’re certainly from far out there. The second of the two bursts was bright enough to be seen from Earth with a good backyard telescope.”

Gamma-ray bursts are the most powerful explosions known in the Universe and are thought to signal the birth of a black hole –either through a massive star explosion or through a merger smaller black holes or neutron stars. Several appear each day from our vantage point. They are difficult to detect and study, however, because they occur randomly from any point in the sky and last only a few milliseconds to about a minute.

Swift, with three telescopes, is designed to detect bursts and turn autonomously within seconds to focus its telescopes on the burst afterglow, which can linger for hours to weeks. The UVOT is a joint product of Penn State and the Mullard Space Science Laboratory in England.

Swift detected bursts on March 18 and 19, as indicted in their names: GRB 050318 and GRB 050319. The UVOT team estimated that the redshifts are 1.44 and 3.24, respectively, which corresponds to distances of about 9.2 billion and 11.6 billion light years. (The second estimate reflects a more precise measurement made with the ground-based Nordic Optical Telescope.) Distance measurements are attained through analysis of the burst afterglow.

Swift has detected 24 bursts so far. GRB 050318 was the first burst in which the UVOT detected an afterglow. The lack of afterglow detection is interesting in its own right, Roming said, because it helps scientists understand why some bursts create certain kinds of afterglows, if any. For example, Swift’s X-ray Telescope has detected afterglows from several bursts. The UVOT detected afterglows in GRB 050318 and GRB 050319 in optical light, but not significantly in ultraviolet.

“Every burst is a little different, and when we add them all up we will begin to see the full picture,” said Dr. Keith Mason, the U.K. UVOT Lead at University College London’s Mullard Space Science Laboratory.

Mason said that UVOT distance measurements will become more precise in the upcoming months as new instruments aboard Swift are employed.

Swift is a medium-class explorer mission managed by NASA Goddard Space Flight Center in Greenbelt, Md. Swift is a NASA mission with participation of the Italian Space Agency and the Particle Physics and Astronomy Research Council in the United Kingdom. It was built in collaboration with national laboratories, universities and international partners, including Penn State; Los Alamos National Laboratory in New Mexico; Sonoma State University in California; the University of Leicester in Leicester, England; the Mullard Space Science Laboratory in Dorking, England; the Brera Observatory of the University of Milan in Italy; and the ASI Science Data Center in Rome, Italy.

More information about each of the Swift-detected gamma-ray bursts, updated every five minutes, is available on the web at: http://grb.sonoma.edu

Original Source: Penn State News Release

Posted on by Fraser Cain

Searching for Gravity Waves

For almost 100 years, scientists have been searching for direct evidence of the existence of gravity waves faint ripples in the fabric of spacetime predicted in Albert Einsteins theory of General Relativity. Today, the hunt for gravity waves has become a worldwide effort involving hundreds of scientists. A number of large, ground-based facilities have been developed in Europe, the United States and Japan, but the most sophisticated search of all will soon take place in space.

Speaking on Tuesday 5 April at the RAS National Astronomy Meeting in Birmingham, Professor Mike Cruise will describe a joint ESA-NASA project called LISA (Laser Interferometric Space Antenna). Scheduled for launch in 2012, LISA will comprise three spacecraft flying in formation around the Sun, making it the largest scientific instrument ever placed in orbit.

LISA is expected to provide the best chance of success in the search for the exciting, low frequency gravity waves, said Professor Cruise. However, the mission is one of the most complex, technological challenges ever undertaken. According to Einsteins theory, gravity waves are caused by the motion of large masses (e.g. neutron stars or black holes) in the Universe. The gravitational influence between distant objects changes as the masses move, in the same way that moving electric charges create the electromagnetic waves that radio sets and TVs can detect.

In the case of a very light atomic particle such as the electron, the motion can be very fast, so generating waves at a wide range of frequencies, including the effects we call light and X-rays. Since the objects which generate gravity waves are much larger and more massive than electrons, scientists expect to detect much lower frequency waves with periods ranging from fractions of a second to several hours.

The waves are very weak indeed. They reveal themselves as an alternating stretching and contracting of the distance between test masses which are suspended in a way that allows them to move. If two such test masses were one metre apart, then the gravity waves of the strength currently being sought would change their separation by only 10e-22 of a metre, or one ten thousandth of a millionth of a millionth of a millionth of a metre.

This change in separation is so small that preventing the test masses being disturbed by the gravitational effect of local objects, and the seismic noise or trembling of the Earth itself, is a real problem that limits the sensitivity of the detectors. Since each metre length in the distance between the test masses gives rise separately to the tiny changes being searched for, increasing the length of the separation between the masses gives rise to a greater overall change that could be detected. As a consequence, gravity wave detectors are made as large as possible.

Current ground-based detectors cover distances of a few kilometres and should be able to measure the millisecond periods of fast-rotating objects such as neutron stars left over from stellar explosions, or the collisions between objects in our local galactic neighbourhood. There is, however, a strong interest in building detectors to search for the collisions between massive black holes that take place during mergers of complete galaxies. These violent events would generate signals with very low frequencies- too low to be observed above the random seismic noise of the Earth.

The answer is to go into space, away from such disturbances. In the case of LISA, the three spacecraft will fly in formation, 5 million kilometres apart. Laser beams travelling between them will measure the changes in separation caused by gravity waves with a precision of about 10 picometres (one hundred thousandth of a millionth of a metre). Since the test masses on each spacecraft will have to be protected from various disturbances that are caused by charged particles in space, they must be housed in a vacuum chamber in the spacecraft. The precision required is 1,000 times more demanding than has ever been achieved in space before and so ESA is preparing a test flight of the laser measurement system in a mission called LISA Pathfinder, due for launch in 2008.

Scientists from the University of Birmingham, the University of Glasgow and Imperial College London are currently preparing the instrumentation for LISA Pathfinder in collaboration with ESA and colleagues in Germany, Italy, Holland, France, Spain and Switzerland. When LISA is operating in orbit, we expect to observe the Universe through the new window offered by gravity waves, said Cruise. In addition to neutron stars and massive black holes, we may be able to detect the echoes of the Big Bang from gravity waves emitted tiny fractions of a second after the event that started our Universe on its current evolution.

Original Source: RAS News Release

Posted on by Fraser Cain

Starburst Galaxies Hide Black Holes

A team of European scientists has used Virtual Observatories to compare observations of distant “starburst” galaxies made at radio and X-ray wavelengths. This is the first study to combine the highest resolution and sensitivity radio and X-ray images which penetrate the dust hiding the centres of some of these distant galaxies.

The team focused on galaxies so far away that their radiation took more than six billion years to reach us. The galaxies are seen as they were when they were less than half the age that the Universe is today.

Speaking on Tuesday 5 April at the RAS National Astronomy Meeting in Birmingham, Dr. Anita Richards (Jodrell Bank Observatory, University of Manchester) will explain how the team used the UK?s MERLIN array of radio telescopes and the Very Large Array to investigate how galaxies in the early Universe differ from those nearby.

“The more remote starburst galaxies, so called because of their high rate of star formation, typically produce 1,000 or more solar masses of stars per year – at least 50 times more than the most active star-forming galaxies in the nearby Universe,” said Dr. Richards.

“Each distant starburst region is tens of thousands of light years across, equivalent to about the inner quarter of the Milky Way – also vastly larger than any such regions found in our part of the Universe.”

The radio search took place in an area known as the Hubble Space Telescope Deep Field North – a patch of sky smaller than the full Moon that contains tens of thousands of galaxies.

Apart from Hubble, radio telescope arrays are the only instruments that can see detailed structures within these galaxies. Moreover, only radio or X-ray emissions can penetrate the dense dust in the innermost regions of some of these galaxies.

The two main sources of radio waves and X-rays are star formation and emissions from Active Galactic Nuclei (AGN) that are generated when material is sucked into a massive black hole and ejected in jets. The team found about twice as many starbursts as AGN, where these could be distinguished in radio images.

The UK AstroGrid and the European AVO ? parts of the international Virtual Observatory – were used to find counterparts for the radio sources from a variety of other data held by archives and observatories around the world. In this way it was discovered that 50 distant X-ray sources with measured redshifts had also been detected by the Chandra space observatory.

Virtual Observatory tools made it easy to calculate the intrinsic brightness of the sources, corrected for distance and redshift. However, the team found that there was no obvious relationship between radio and X-ray luminosity. This was a surprise since there is such a link in most local starburst galaxies.

Some of the faintest radio sources were found to emit the most X-rays and vice versa – suggesting that two separate mechanisms within each galaxy were generating powerful emissions at opposite extremes of the spectrum.

Members of the European Virtual Observatory team had earlier used the Chandra X-ray data and Hubble images to find 47 AGN in the Hubble Deep Field North. These appeared to be seen sideways on, so that the dusty torus surrounding the black hole blocked all but the most energetic X-rays from emerging in our direction.

“Astonishingly, only 4 of these looked like AGN in the radio observations,” said Richards. “10 had radio emissions characteristic of starbursts, 4 could not be classified, and the rest went undetected by radio telescopes.”

The 10 super-starburst/AGN hybrids tended to be at a higher redshift ? indicating that they are much further away from Earth than the rest of the radio galaxies. Over half of them were among the enigmatic ?SCUBA sources?. These objects are very bright at wavelengths just under a millimetre, probably as a result of dust being strongly heated by violent star formation, but almost invisible to most other instruments.

“We concluded that, not only were these young galaxies undergoing much more violent and extended star formation than we see today, but they were simultaneously feeding active, supermassive black holes responsible for the X-ray emission,” said Richards.

“One clue to the origin of this phenomenon is that the Hubble Space Telescope often reveals two or more distorted galaxies associated with these sources, suggesting that galaxy interactions were commoner when the Universe was young. The ensuing collisions of gas and dust clouds trigger star formation and also feed the central black hole.

“Modern starburst galaxies are not only slower at star formation, but mostly have much quieter AGN, if any. This is not surprising as the super-starbursts must run out of fuel quite quickly (by cosmological standards), when all the available material has either turned into stars or fallen into the black hole.”

Original Source: RAS News Release

Posted on by Fraser Cain

How Many Habitable Planets Could Be Out There?

How many planets like the Earth are there among the 130 or so known planetary systems beyond our own? How many of these ?Earths? could be habitable?

Recent theoretical work by Barrie Jones, Nick Sleep, and David Underwood at the Open University in Milton Keynes indicates that as many as half of the known systems could be harbouring habitable ?Earths? today.

Unfortunately, existing telescopes are not powerful enough to see these relatively small, distant ?Earths?. Orbiting close to a much brighter star, these very faint worlds resemble glow-worms hidden in the glare of a searchlight.

All of the planets that have been detected so far are giants the mass of Neptune or larger. Even so, they cannot be directly seen with ground-based instruments. Almost all of the known exoplanets have been found through the ?wobbling? motion they induce in their star as they orbit it, like a twirling dumb-bell in which the mass at one end (the star) is much greater than the mass at the other end (the giant planet).

Speaking today at the RAS National Astronomy Meeting in Birmingham, Professor Jones explained how his team used computer models to see if ?Earths? could be present in any of the currently known exoplanetary systems, and whether the gravitational buffeting from one or more giant planets in those systems would have torn them out of their orbits.

?We were particularly interested in the possible survival of ?Earths? in the habitable zone,? said Professor Jones. ?This is often called the ?Goldilocks zone?, where the temperature of an ?Earth? is just right for water to be liquid at its surface. If liquid water can exist, so could life as we know it.?

The Open University team created a mathematical model of a known exoplanetary system, with its star and giant planet(s), then launched an Earth-sized planet at some distance from the star to see if it survived.

By detailed study of a few representative exoplanetary systems, they found that each giant planet is accompanied by two ?disaster zones? – one exterior to the giant, and one interior. Within these zones, the giant?s gravity will cause a catastrophic change in the Earth-like planet?s orbit. The dramatic outcome is a collision with either the giant planet or the star, or ejection into the cold outer reaches of the system.

The team found that the locations of these disaster zones depend not only on the mass of the giant planet (a well known result) but also on the eccentricity of its orbit. They thus established rules for determining the extent of the disaster zone.

Having found the rules, they applied them to all of the known exoplanetary systems – a much quicker method than studying each system in detail. The range of distances from the star covered by its habitable zone was compared to the locations of the disaster zones to see if there was a full or partial safe haven for an Earth-like planet.

They discovered that about half of the known exoplanetary systems offer a safe haven for a period extending from the present into the past that is at least long enough for life to have developed on any such planets. This assumes that ?Earths? could have formed in the first place, which seems quite likely.

However, the situation is complicated by the fact that the habitable zone migrates outwards as the star ages, and in some cases this changes the potential for life to evolve. Thus, in some cases a safe haven might have been available only in the past, while in other cases it might exist only in the future.

These scenarios of past extinction and future birth increase to about two-thirds the proportion of the known exoplanetary systems that are potentially habitable at some time during the main-sequence lifetime of their central star.

Original Source: RAS News Release

Posted on by Fraser Cain

What’s Up This Week – Apr 4 – Apr 10, 2005

Monday, April 4 – Tonight our binocular and telescope study will take us to a place of intrigue… An interacting pair of galaxies that are easily observed in Ursa Major. Start by drawing an imaginary line between Phecda and Dubhe, and extend that just one step further into space as we explore the M81 and M82.

Discovered in December 1774 by JE Bode at Berlin and photographed as early as March 1899, these two deep sky favourites will appear as a pair to binoculars and low power telescope fields. The M81 is truly spiral perfection with its symmetrical structure and bright nucleus. Spanning approximately 36,000 light years in diameter, it is one of the densest known galaxies with one third of its mass concentrated at the core. Because it contains vast numbers of red and yellow giants, larger telescopes at power will see a golden “glow” to the structure – the combined luminosity of twenty billion suns.

Its neighbor – the M82 – is often mistaken in the small telescope for edge-on in appearance, but shows no sign of true spiral structure movement. Its light is polarized, leading science to believe it contains a super-massive magnetic field. The M82 is also a powerful radio source with huge masses of dust irradiated by stars possessing unusual spectral qualities. A violent outburst may have occurred within the galaxy as recently as 1.5 million years ago releasing the energy equivalent of several million exploding suns. Shock waves emanating from the M81 resemble the synchrotron radiation first associated with planetary nebula M1 – but on an enormous scale. Can you image a supernova remnant the size of an entire galactic core region?!

Roughly every one hundred million years, M81 and M82 make a “pass” at one another, reaching out with immensely powerful gravitational arms to intertwine the two galaxies. It is theorized that during the last interaction, M82 raised rippling density waves which circulated throughout M81. The result? Possibly the most perfectly formed spiral galaxy in all of space, but M81’s influence left M82 a broken galaxy – filled with exploded stars and colliding gas – a galaxy so violent it emits X-rays. Reactions induced by colliding dust and gas caused the birth of numerous brilliant stars – stars capable of creating dense atoms and extreme motion that causes immense magnetic fields. The end may already be envisioned for the M81 and M82. Scientists speculate within a few billion years, the two galaxies will combine, becoming indistinguishable but for the welter of radiation that the union leaves behind. We known this same fate may await our own galaxy as we combine with our largest neighbor – the Andromeda Galaxy – but don’t let that stop you from viewing the M81’s intense core and smooth spiral form – or the M82’s notched spindle shape tonight…

That’s billions of years in the future.

Tuesday, April 5 – This evening we will study another pair of galaxies that can be seen in large binoculars and are outstanding for telescopic study. Identify the triangle of stars that mark the “hips” of Leo. The southwestern star is Theta and about three finger widths to its south is Iota. If skies are transparent enough to see Eta between them, then you will have no problem locating the M65 and M66 to Eta’s east/southeast.

Discovered by Mechain in March 1780, apparently Mr. Messier didn’t notice the bright pair when a comet passed between them in 1773. At around 35 million light years away, you will find the M66 to be slightly brighter than its 200,000 light year distant western neighbor – the M65. While both are Sb classed spirals, the two couldn’t appear more different. The M65 has a bright nucleus and a smooth spiral structure with a dark dustlane at its eastern edge. The M66 has a more stellar core region with thick, bright arms that show knots to larger scopes – as well as a wonderful extension from the southern edge. If you are viewing with a larger scope, you may notice to the north of this famous pair yet another galaxy! The NGC 3628 is a similar magnitude edge-on beauty with a great dissecting dark dustlane. This pencil-slim, low surface brightness galaxy is a bit of a challenge for smaller scopes, but larger ones will find its warped central disc well worth high power study.

Congratulations! You’ve just conquered the “Leo Trio”.

Wednesday, April 6 – Tonight let’s head for another trio of galaxies that are suited best for mid-to-large aperture telescopes. Begin by heading west about a fist’s width from Regulus and identify 52 Leonis. Our mark is one and a half degrees south.

At lower power you will see a triangle of galaxies. The largest and brightest is the M105 discovered by Mechain on March 24, 1781. This dense elliptical galaxy would appear to be evenly distributed, but the Hubble Space Telescope revealed a huge area within its core to be equal to about 50 million solar masses. Companion elliptical to the northeast – NGC 3384 will reveal a bright nucleus as well as an elongated form. The most faint of this group – NGC 3389 is receding spiral and for larger scopes will reveal a “patchiness” in structure.

Continue another degree south and enjoy another galactic pair. The widely spaced M96 and M95 are part of this galaxy grouping known as Leo I. The dusty spiral – M96 – will appear as a silver oval, whose nucleus is much sharper than its faint spiral arms that contained a supernova as recently as 1998. To M96’s west, you will discover one very beautiful barred spiral – M95. While both of these were discovered by Mechain only four days earlier than the M105, it wasn’t until recent years that they became the prime target of the Hubble Space Telescope. We enjoy the M95 for its unique ring-like arms and unmistakable barred core, but the HST was looking for cephid variables and determining the Hubble Constant. While we don’t need a space telescope to view this group of galaxies, we can now appreciate knowing that we can see 38 million light years away from our own backyard!

Thursday, April 7 – On this day in 1991, the Compton Gamma Ray Observatory (GRO) was deployed by space shuttle Atlantis. After serving for more than 9 years, the CRO plunged to a fiery death in the Pacific Ocean, but we can celebrate its accomplishments by viewing a source of gamma rays – the M87.

You may be able to detect the M87’s round glow with large binoculars slightly more than a fist’s width east of Epsilon Virginis with an 8th magnitude star, but telescope users will enjoy the most massive and luminous of all known galaxies. But there is much more here than meets the eye! Also known as Virgo A, the M87 is the fifth most intense radio source in the sky – 3C 274. It is also home to more than 4000 globular clusters (the Milky Way contains about 110) and a 4,000 light year long “jet” of high speed particles that could be associated with a black hole.

Friday, April 8 – Today’s highlight is a hybrid solar eclipse! Without the cursory lecture of safe solar observing techniques, observers in parts of Costa Rica, Panama, Venezuela and Columbia will enjoy the most exciting part of the show as the Sun moves from annular to total – and back to annular again around local sunset. For observers in Central America, the Caribbean and parts of South America, you will enjoy a spectacular partial eclipse that ranges anywhere from 80 to 90% coverage. Most of Mexico will get to see about half of the Sun in shadow, while the southern United States ranges from 20 to 40%. The northern-most limit cuts across central New Jersey, Pennsylvania, Ohio, Indiana, and southern Illinois and begins a southward arc ending in southern Arizona and California. For observers south of this line, it is still worth seeing a “bite” taken out of the Sun’s edge! For a list of times and many more details, please visit “Mr. Eclipse” – Fred Espenak – at this page.

Wishing you clear skies.

(Take advantage of tonight’s new moon to just roam around and enjoy the galaxy fields of Virgo. Never stress about identifying all you see, for the pleasure is just seeing them!)

Saturday, April 9 – This morning will present a unique opportunity for those who enjoy watching Jupiter’s moons. At 04:53 UT (12:43 a.m. ESDT), Io, Europa and Calisto will form a very close dance to Jupiter’s east. This formation will last for about an hour and will be well worth watching them move slowly apart.

Let’s use tonight’s dark sky to enjoy a “Jupiter-sized” planetary nebula – the M97. Often referred to as the “Owl”, you will find this sometimes difficult object about two and a half degrees south of Beta Ursae Majoris. Discovered on February 16, 1781 by the unsung hero Mechain, its visual brightness makes it a candidate for larger binoculars, but it takes a large aperture telescope to truly appreciate.

Graced by a 14th magnitude central star – one of the hottest known – this planetary nebula is highly unusual because we cannot clearly define its distance. The “Owl” is very complex, and its appearance has often been interpreted as a cylindrical torus viewed at an acute angle. What we see as “eyes” may be the less dense ends of the cylinder. The shell itself is encased by a fainter nebula or lower ionization. While we once believed this type of formation was the result of an ancient novae, the M97 re-defines our thinking. This quiet type of emission activity may just be the result of a star’s old age… Giving the ancient “Owl” a place of honour in the north.

Sunday, April 10 – Tonight’s singular destination can be detected as a faint glow in binoculars, can be found with the smallest of telescopes, but provides a stunning view with aperture. Set your sights on bright Spica and head eleven degrees due west…

Once again discovered by Mechain, the M104 – “Sombrero” – is one of the finest examples of an edge-on galaxy in the night sky. The “Sombrero” has a huge, bulging bright core region, well-defined spiral arms and a bold, dark dustlane. The core region is highly conspicuous and contains a vastly populated globular cluster system. As the dominating member of the 104 group, this fantastic galaxy is the one of the very first discovered in redshift. At around 400 million light years away, it is receding at about 700 miles per second, but that won’t stop you from enjoying its wonderful transparent qualities and star spangled field!

Until next week? Keep looking up and enjoying the wonders of the Cosmos! Light speed… ~Tammy Plotner

Posted on by Fraser Cain

Portrait of Pandora in the Rings

Pandora is seen in this dramatic view, orbiting just beyond the outer edge of Saturn’s F ring. Several bright areas are visible within the F ring. In the main rings, the Keeler gap and the Encke gap, with a bright ringlet, are also visible. Pandora is 84 kilometers (52 miles) across.

The image was taken in visible light with the Cassini spacecraft narrow-angle camera on Feb. 18, 2005, at a distance of approximately 1.2 million kilometers (746,000 miles) from Pandora and at a Sun-Pandora-spacecraft, or phase, angle of 108 degrees. The image scale is 7 kilometers (4 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 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/SSI News Release

Posted on by Fraser Cain

And the Winner is…

Thanks to everyone who threw your name into the hat to win the Apollo 13 DVD, and the winner is… drum roll… Richard Hobbs. I received a total of 472 entries, and a lot of great emails too, so thanks for getting involved. This was fun, and I think I’ll convince publishers to send me more copies of stuff in the future so I can give it away.

Of course, if you didn’t win, you can still purchase a copy from Amazon.com.

Fraser Cain
Publisher
Universe Today

Posted on by Fraser Cain

Earth Seen in Gamma Rays

A NASA-funded scientist has produced a new type of picture of the Earth from space, which complements the familiar image of our “blue marble”. This new picture is the first detailed image of our planet radiating gamma rays, a type of light that is millions to billions of times more energetic than visible light.

The image portrays how the Earth is constantly bombarded by particles from space. These particles, called cosmic rays, hit our atmosphere and produce the gamma-ray light high above the Earth. The atmosphere blocks harmful cosmic rays and other high-energy radiation from reaching us on the Earth’s surface.

“If our eyes could see high-energy gamma rays, this is what the Earth would look like from space,” said Dr. Dirk Petry of NASA Goddard Space Flight Center in Greenbelt, Md. “Other planets — most famously, Jupiter — have a gamma-ray glow, but they are too far away from us to image in any detail.”

Petry assembled this image from seven years of data from NASA’s Compton Gamma-Ray Observatory, which was active from 1991 to 2000. The Compton Observatory orbited the Earth at an average altitude of about 260 miles (420 km). From this distance, the Earth appears as a huge disk with an angular diameter of 140 degrees. The long exposure and close distance enabled Petry to produce a gamma-ray image of surprisingly high detail. “This is essentially a seven-year exposure,” Petry said.

The gamma rays produced in the Earth’s atmosphere were detected by Compton’s EGRET instrument, short for Energetic Gamma-Ray Experiment Telescope. In fact, 60 percent of the gamma rays detected by EGRET were from Earth and not deep space. Although it makes a pretty image, local gamma-ray production interferes with observations of distant gamma-ray sources, such as black holes, pulsars, and supernova remnants.

Petry created this gamma-ray Earth image to better understand the impact of “local” cosmic-ray and gamma-ray interactions on an upcoming NASA mission called GLAST, the Gamma-ray Large Area Space Telescope. GLAST is planned for launch in 2007. Its main instrument, the Large Area Telescope, is essentially EGRET’s successor.

In 1972 and 1973 the NASA satellite SAS-II captured the first resolved image of the Earth in gamma rays, but the detectors had less exposure time (a few months) and worse energy resolution.

Petry, a member of the GLAST team at NASA Goddard, is an assistant research professor at the Joint Center for Astrophysics of the University of Maryland, Baltimore Country. A scientific paper describing his work is available at:

http://xxx.lanl.gov/abs/astro-ph/0410487

Original Source: NASA News Release