Posted on by Fraser Cain

Sites to Look for Life on Mars

OMEGA instrument has identified clay beds which supported life in the past. Image credit: ESA/OMEGA. Click to enlarge
ESA’s Mars Express spacecraft has completed an extensive map of minerals across the surface of Mars, pointing at the places future rovers might want to search for life. This new analysis shows that lakes and oceans might have been present on Mars, but they disappeared more than 4 billion years ago. That wouldn’t have given life much time to get a serious foothold before the whole planet became a desert. So these pockets of hydrated minerals would be the best places to try and find evidence of past life.

By mapping minerals on the surface of Mars using the European Space Agency’s Mars Express spacecraft, scientists have discovered the three ages of Martian geological history – as reported in today’s issue of Science – and found valuable clues as to where life might have developed.

The new work shows that large bodies of standing water might only have been present on Mars in the remote past, before four thousand million years ago, if they were present at all. Within half a billion years, these conditions had faded away.

The results come from the Observatoire pour la Mineralogie, l’Eau, les Glaces et l’Activite (OMEGA) instrument on board Mars Express. In one Martian year (687 Earth days) of operation, OMEGA mapped 90 percent of the surface, allowing the identification of a variety of minerals and the processes by which they have been altered during the course of Martian history. The maps have allowed a team of scientists, led by Professor Jean-Pierre Bibring, Institut d’Astrophysique Spatiale (IAS), Orsay (France), to identify three geological eras for Mars.

The earliest, named by the authors as the ‘phyllosian’ era, occurred between 4.5-4.2 thousand million years ago, soon after the planet formed. The environment was possibly warm and moist at this time, allowing the formation of large-scale clay beds, many of which survive today.

The second era, the ‘theiikian’, took place between 4.2 and 3.8 billion years ago. It was prompted by planet-wide volcanic eruptions that drove global climate change. In particular, the sulphur these eruptions belched into the atmosphere reacted with the water to produce acid rain, which altered the composition of the surface rocks where it fell.

Finally, there was the ‘siderikian’, the longest lasting of the Martian eras. It began sometime around 3.8-3.5 billion years ago and continues today. There is little water involved in this era; instead, the rocks appear to have been altered during slow weathering by the tenuous Martian atmosphere. This process gave Mars its red colour.

The eras are named after the Greek words for the predominant minerals formed within them. The one most likely to have supported life was the phyllosian, when clay beds could have formed at the bottom of lakes and seas, providing the damp conditions in which the processes of life could begin.

However, there are still question marks. The team points out that the clay beds might have been formed underground, rather than in lakebeds.

“Hydrothermal activity below the surface, the impact of water-bearing asteroids, even the natural cooling of the planet could all have promoted the formation of clay below Mars’s surface. If so, the surface conditions may always have been cold and dry,” said Bibring.

After this initial period, water largely disappeared from the planet’s surface either by seeping underground or being lost into space. Except for a few localised transient water events, Mars became the dry, cold desert seen by spacecraft today. This new identification of clay beds on Mars provides high-priority targets for future Mars landers that seek to investigate whether Mars once harboured life.

“If living organisms formed, the clay material would be where this biochemical development took place, offering exciting places for future exploration because the cold Martian conditions could have preserved most of the record of biological molecules up to the present day,” concluded Bibring.

Original Source: ESA Portal

Posted on by Fraser Cain

A Crescent Saturn

Saturn crescent with Mimas, Rhea and Tethys. Image credit: NASA/JPL/SSI. Click to enlarge
This view of Saturn shows a thick crescent of the planet bathed in sunlight with the rest in shadow. Three moons are visible in this photograph: Mimas, Ryea and Tethys. Cassini took this photograph on March 11, 2006 when it was approximately 2.8 million kilometers (1.8 million miles) from Saturn.

The tilted crescent of Saturn displays lacy cloud bands here along with a bright equatorial region and threadlike ring shadows on the northern hemisphere.

Three moons are visible here. Mimas (397 kilometers, or 247 miles across) at left and faint, is aligned with the ringplane. At right are Rhea (1,528 kilometers, or 949 miles across, at top) and Tethys (1,071 kilometers, or 665 miles across, below Rhea).

The image was taken in polarized infrared light with the Cassini spacecraft wide-angle camera on March 11, 2006, at a distance of approximately 2.8 million kilometers (1.8 million miles) from Saturn. The image scale is 166 kilometers (103 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

Storms Never End on Saturn

The Dragon storm. Image credit: NASA/JPL/SSI Click to enlarge
On Earth we have hurricane season, and a welcome break in between. On Saturn, it’s always hurricane season. Hurricanes here on Earth are caused by warm ocean temperatures heated by the Sun that feed energy and water up into the storm clouds. On Saturn, the energy comes from the internal heat of the planet, which is still slowly shrinking after its formation billions of years ago.

On Saturn, it may be a very long wait for the calm after a storm. As big and destructive as hurricanes on Earth can be, at least they don’t last long. Not like those on Saturn, where storms may rage for months or years. Viewed from space, hurricanes on Earth and the huge atmospheric disturbances observed on Saturn look similar. But their differences are greater and offer intriguing insights into the inner workings of the ringed world being investigated by scientists on NASA’s Cassini mission.

Earth’s hurricanes and Saturn’s storms each have swirling clouds, convection, rain and strong rotating winds. “Hurricanes on Earth are low pressure centers at the ground and high pressures at the top where the storms flatten out,” says Dr. Andrew Ingersoll, member of the Cassini imaging team and professor of planetary science at the California Institute of Technology in Pasadena, Calif. “Storms on Saturn could be like hurricanes if what we’re seeing is the top of the clouds.”

The frequency of storms on Saturn seems to be about the same as on Earth, and the fraction of planet occupied by storms is also similar. Not surprisingly, since Saturn is so much larger than Earth — nine Earths would fit across its equator — its storms are bigger. Hurricane Katrina stretched more than 380 kilometers (240 miles) across, for example, while two storms the Cassini spacecraft spotted in February 2002 each extend more than 1,000 kilometers (620 miles) in diameter, about the size of Texas or France.

On Earth, hurricane winds can exceed 240 kilometers per hour (150 miles per hour), similar to the speed of the jet stream, just about the fastest wind on the planet. Though spinning furiously, hurricanes travel along at a much slower pace — eight to 32 kilometers per hour (five to 20 miles per hour). Saturn is different because its jet stream is much stronger. “Saturn’s a very windy place,” says Ingersoll. “The jet stream on Saturn blows ten times faster than on Earth, up to a thousand miles per hour.” Saturn’s winds are like conveyor belts between which storms appear to roll like ball bearings, he explains. “While we don’t know the wind speeds within the storms, a good guess is that they are slower than the winds in the jet stream.”

What most distinguish storms on Saturn from those on Earth are the forces that drive them and physical differences between the two planets.

The heat that drives hurricanes on Earth comes from the oceans, vast reservoirs of solar energy. The oceans are also the source of moisture for convection, which draws energy from the ocean into the atmosphere and creates storm clouds and driving rainfall. Hurricanes quickly fade once they make landfall, once the plug is pulled on their power source.

The fuel for Saturn’s storms is quite different. The interior of the planet acts like an ocean and stores energy, but the energy does not come from the sun. “Saturn makes it own heat, which it got when the pieces that made the planet crashed together during the violent history of the early solar system,” says Ingersoll.

Saturn’s atmosphere has all the ingredients necessary for hurricane-like storms including heat and water vapor, he continues, so there’s no need for that first step in hurricane development where the ocean evaporates. And, without a solid surface like Earth’s ocean, Saturn’s storms behave very differently.

“You’d think that when two storms merge, for example, that you’d get a bigger storm,” says Ingersoll, “but they seem to stay the same size. They can also split apart. They may go on forever, merging and splitting.”

Scientists will be able to study Saturn’s storms more closely next year, when the Cassini spacecraft tours a region in the southern hemisphere mission scientists that call storm alley.

With the exception of a few storms, like the dramatic Dragon Storm observed by the Cassini spacecraft last year, most of Saturn’s storms are unnamed, unlike those on Earth. That may change, says Ingersoll, when scientists get to know them better.

Original Source: NASA News Release

Posted on by Fraser Cain

The Hunt for Gravity Waves


As part of his general theory of relativity, Einstein predicted that mass should emit gravity waves. They’ll be weak, though, so it would take very massive objects to produce waves detectable here on Earth. One experiment working towards their detection is the Laser Interferometer Gravitational-Wave Observatory (or LIGO). It should be able to detect the most powerful gravity waves as they pass through the Earth. And a space-based observatory planned for launch in 2015 called LISA should be stronger still.

Scientists are close to actually see gravitational waves. Image credit: NASA
Gravity is a familiar force. It’s the reason for fear of heights. It holds the moon to the Earth, the Earth to the sun. It keeps beer from floating out of our glasses.

But how? Is the Earth sending secret messages to the moon?

Well, yes — sort of.

Eanna Flanagan, Cornell associate professor of physics and astronomy, has devoted his life to understanding gravity since he was a student at University College Dublin in his native Ireland. Now, nearly two decades after leaving Ireland to study for his doctorate under the famous relativist Kip Thorne at the California Institute of Technology, his work focuses on predicting the size and shape of gravitational waves — an elusive phenomenon forecast by Einstein’s 1916 Theory of General Relativity but which have never been directly detected.

In 1974, Princeton University astronomers Russell Hulse and Joseph H. Taylor Jr. indirectly measured the influence of gravity waves on co-orbiting neutron stars, a discovery that earned them the 1993 Nobel Prize in physics. Thanks to the recent work of Flanagan and his colleagues, scientists are now on the verge of seeing the first gravity waves directly.

Sound cannot exist in a vacuum. It requires a medium, such as air or water, through which to deliver its message. Similarly, gravity cannot exist in nothingness. It, too, needs a medium through which to deliver its message. Einstein theorized that that medium is space and time, or the “spacetime fabric.”

Changes in pressure — a thump on a drum, a vibrating vocal cord — produce sound waves, ripples in air. According to Einstein’s theory, changes in mass — the collision of two stars, dust landing on a bookshelf — produce gravity waves, ripples in spacetime.

Because most everyday objects have mass, gravity waves should be all around us. So why can’t we find any?

“The strongest gravity waves will cause measurable disturbances on Earth 1,000 times smaller than an atomic nucleus,” explained Flanagan. “Detecting them is a huge technical challenge.”

The response to that challenge is LIGO, the Laser Interferometer Gravitational-Wave Observatory, a colossal experiment involving a collaboration of more than 300 scientists.

LIGO consists of two installations nearly 2,000 miles apart — one in Hanford, Wash., and one in Livingston, La. Each facility is shaped like a giant “L,” with two 2.5-mile-long arms made of 4-foot-diameter vacuum pipes encased in concrete. Ultra-stable laser beams traverse the pipes, bouncing between mirrors at the end of each arm. Scientists expect a passing gravity wave to stretch one arm and squeeze the other, causing the two lasers to travel slightly different distances.

The difference can then be measured by “interfering” the lasers where the arms intersect. It is comparable to two cars speeding perpendicularly toward a crossroads. If they travel the same speed and distance, they will always crash. But if the distances are different, they might miss. Flanagan and his colleagues are hoping for a miss.

Furthermore, exactly how much the lasers hit or miss will provide information about the characteristics and origin of the gravitational wave. Flanagan’s role is to predict these characteristics so that his colleagues at LIGO know what to look for.

Due to technological limits, LIGO is only capable of sensing gravitational waves of certain frequencies from powerful sources, including supernova explosions in the Milky Way and rapidly spinning or co-orbiting neutron stars in either the Milky Way or distant galaxies.

To expand potential sources, NASA and the European Space Agency are already planning LIGO’s successor, LISA, the Laser Interferometer Space Antenna. LISA is similar in concept to LIGO, except the lasers will bounce among three satellites 3 million miles apart trailing the Earth in orbit around the sun. As a result, LISA will be able to detect waves at lower frequencies than LIGO, such as those produced by the collision of a neutron star with a black hole or the collision of two black holes. LISA is scheduled for launch in 2015.

Flanagan and collaborators at the Massachusetts Institute of Technology recently deciphered the gravitational wave signature that results when a supermassive black hole swallows a sun-sized neutron star. It is a signature that will be important for LISA to recognize.

“When LISA flies we should see hundreds of these things,” noted Flanagan. “We will be able to measure how space and time are warped, and how space is supposed to be twisted around by a black hole. We see electromagnetic radiation, and we think it’s probably a black hole — but that’s about as far as we’ve got. It will be very exciting to finally see that relativity actually works.”

But, he warned, “It may not work. Astronomers observe that the expansion of the universe is accelerating. One explanation is that general relativity needs to be modified: Einstein was mostly right, but in some regimes things could work differently.”

Thomas Oberst is a science writer intern at the Cornell News Service.

Original Source: Cornell University

Posted on by Fraser Cain

Twin Open Clusters by Hubble

Star clusters in small magellanic cloud. Image credit: ESA/NASA. Click to enlarge
The Hubble Space Telescope has captured these stunning images of open star clusters NGC 265 and NGC 290 in the Small Magellanic Cloud. The two clusters are about 200,000 light years away, and are roughly 65 light-years across. Clusters like this contain young stars roughly the same age, and born from the same cloud of interstellar gas. These clusters will eventually be broken apart by the gravity of other stars, gas clouds and clusters.

NASA’s Hubble Space Telescope has captured the most detailed images to date of the open star clusters NGC 265 and NGC 290 in the Small Magellanic Cloud – two sparkling sets of gemstones in the southern sky.

These images, taken with Hubble’s Advanced Camera for Surveys, show a myriad of stars in crystal clear detail. The brilliant open star clusters are located about 200,000 light-years away and are roughly 65 light-years across.

Star clusters can be held together tightly by gravity, as is the case with densely packed crowds of hundreds of thousands of stars, called globular clusters. Or, they can be more loosely bound, irregularly shaped groupings of up to several thousands of stars, like the open clusters shown in this image.

The stars in these open clusters are all relatively young and were born from the same cloud of interstellar gas. Just as old school-friends drift apart after graduation, the stars in an open cluster will only remain together for a limited time and gradually disperse into space, pulled away by the gravitational tugs of other passing clusters and clouds of gas. Most open clusters dissolve within a few hundred million years, whereas the more tightly bound globular clusters can exist for many billions of years.

Open star clusters make excellent astronomical laboratories. The stars may have different masses, but all are at about the same distance, move in the same general direction, and have approximately the same age and chemical composition. They can be studied and compared to find out more about stellar evolution, the ages of such clusters, and much more.

The Small Magellanic Cloud, which hosts the two star clusters, is one of the small satellite galaxies of the Milky Way. It can be seen with the unaided eye as a hazy patch in the constellation Tucana (the Toucan) in the Southern Hemisphere. The Small Magellanic Cloud is rich in gas nebulae and star clusters. It is most likely that this irregular galaxy has been disrupted through repeated interactions with the Milky Way, resulting in the vigorous star-forming activity seen throughout the cloud. NGC 265 and NGC 290 may very well owe their existence to these close encounters with the Milky Way.

The images were taken in October and November 2004 through F435W, F555W, and F814W filters (shown in blue, green, and red, respectively).

Original Source: HubbleSite News Release

Posted on by Fraser Cain

What’s Up This Week – April 18 – April 23, 2006

M102: “The Spindle Galaxy”. Image credit: NOAO/AURA/NSF . Click to enlarge.
Greetings, fellow SkyWatchers! This week begins with a meteor shower, but quickly turns galaxy hunt as we sail the galactic realm of the Virgo Cluster. If all you ask is a tall ship and a star to steer it by – then weigh anchor, because…

Here’s what’s up!

Tuesday, April 18 – Tonight let’s have a look at the Leo Trio – a superb group of two Messier galaxies and NGC 3628. Located some 35 million light years away, they make up their own smaller collection – the M66 galaxy group. All three may be framed together at low power and can best be located by first centering on Theta Leonis and sweeping a little more than a finger-width south to 73 Leonis. By putting star 73 less than a degree west, you will first see 9.5 magnitude M65 enter the low power field. M65 will soon be followed by brighter, larger and more face-on 9.0 magnitude M65. Both were discovered by Charles Messier on March 1, 1780. Larger and fainter yet is the irregular galaxy NGC 3628, which can be included in the low power field by shifting the pair south. Despite having a similar apparent magnitude, one look at this low surface brightness galaxy and you will easily forgive the famed comet hunter and his hard-working friend for missing it!

Want a challenge? Center your scope on 73 Leonis again and shift slightly more than half a degree southwest. Look for mid-sized 11th magnitude NGC 3593. Something even more difficult? How about 12th magnitude galaxy NGC 3596. This face-on spiral galaxy is also of low surface brightness and requires a large scope. Start at bright Chertan and shift less than a degree south-southeast to locate it.

Wednesday, April 19 – Tonight is an ideal time to study “Bode’s Galaxies” – now high in the northwest of the constellation of Ursa Major. To find this extraordinary pair of small scope studies, first locate Phecda (Beta) and 2 Dubhe (Alpha). Draw a line between this bright pair and extend that line an equal distance northwest beyond Alpha. Both galaxies are visible in large finderscopes or binoculars – but if you overextend, look for faint 24 Ursa Majoris and drop a finger-width southeast.

Discovered in December 1774 by J.E. Bode, these two deep sky favorites hold secrets between themselves. Photographed as early as March, 1899, the pair is central to a group of galaxies encompassing the northern circumpolar constellations Ursa Major and Camelopardalis. In small scopes and low powers, the two galaxies give the appearance of “Cat’s eyes” glowing in the night. Mid-sized scopes reveal the spiral nature of the brighter more southerly M81, while mottling can be seen in the irregular spindle shaped M82.

Center on M81 and make a shift of less than a degree southeast. This reveals two 8th magnitude stars forming a right triangle with 10th magnitude face-on spiral galaxy NGC 3077. More difficult is larger and fainter NGC 2976 – a tough find for even mid-aperture due to its low surface brightness and lack of a bright core. To locate the NGC 2976, return to M81 and shift the grand spiral slightly west about a degree and a half.

All four galaxies are part of the M81 group – a small galaxy cluster located some 12 million light years away. M81 and M82 are bound together in a powerful gravitational embrace. Only a few million years ago the two had a close encounter of a most difficult kind – one that largely devastated the structure of the less massive M82 but left its heavier companion completely intact with unrivaled spiral structure of great symmetry and beauty.

Thursday, April 20 – Are you ready to explore further? Then hold on to your star charts and get ready to be lost… The Coma Berenices galaxy group now enters the scene and there are so many galaxies visible that the hard part is being sure of what you are looking at! To get your bearings, start at Denebola (Beta Leonis) and move due east 6.5 degrees to the star 6 Coma Berenices. Once centered on 6 Comae, shift back toward Denebola a half degree to view one of the faintest of the Messier galaxies – M98 – a large near edge-on spiral. Discovered along with M99 and 100 by Pierre M?chain on March 15, 1781, the three discoveries became Messier’s last entries in the original published 3rd edition of his catalog. Although the view of 10th magnitude M98 may be disappointing through smaller scopes, this galaxy comes into its own using larger instruments where its nicely defined and expansive edge-on appearance becomes obvious.

By re-centering 6 Comae in the field and shifting less than one degree southeast, our next study – 9.8 magnitude spiral galaxy M99 – can be reliably identified. Should you go the same distance due east instead, you will encounter 11.5 magnitude NGC 4262. While due south this same distance you will find 11.2 magnitude NGC 4212 and its 13th magnitude neighbor – IC 3061. Although scopes can reveal M99 is a spiral today, it was Lord Rosse (in the spring of 1846) who first recognized the spiral nature of some galaxies.

M100, last on the originally published list, is found by again centering on 6 Comae. At low power, move 2 degrees northeast along a line of finder scope stars. M100 – at magnitude 9.4 – appears no brighter on the surface than M99 due to its greater apparent size. Like M99, M100 was included in Lord Rosse’s original 1850’s list of 14 spiral nebulae. Although face-on in presentation, M100 has two widely displaced and asymmetric spiral arms that can be detected visually through large scopes. Observers using mid-sized scopes should also look for 11.8 magnitude NGC 4312 south of M100. It’s also possible to see 13th magnitude IC 783 roughly that same distance due west.

Friday, April 21 – With dark sky to spare, tonight we continue our explorations of the Coma Berenices galaxy group – part of the larger Virgo supercluster of galaxies lying perpendicular to the plane of our own Milky Way galaxy.

Begin by first centering 6 Comae in the finder, then shift north-northeast 3 degrees to the disparate double, 11 Comae. Shift a little more than a degree due east to one of the brighter Messier galaxies in the Virgo cluster – 9th magnitude M85. In photographs, M85 looks like a giant elliptical galaxy but it’s a lenticular spiral completely devoid of arm structure. Located some 60 million light years away, this luminous mass of stars is relatively free of dust and has a diameter of 125,000 light years. M85 is larger than our own Milky Way, and more densely packed with stars.

A breath west of M85 is tiny 11th magnitude NGC 4394 – an easy study in moderately sized scopes. Slightly more than a degree in the opposite direction is larger 11th magnitude NGC 4293 – another round galaxy but one having a brighter core.

Before you call it a night, take a look east. Brilliant Jupiter is now taking up a year-long residence in Libra. You’ll need to wait for the planet to rise higher in the later evening to get a good view.

Saturday, April 22 – Today celebrates the birthday of Sir Harold Jeffreys. Born in 1891, Jeffreys was an early astrogeophysicist and the first person to envision an Earth with a fluid core in its center. Jeffreys also helped improve our understanding of tidal friction, overall planetary structure, and the origins of the solar system.

Up before dawn? Then enjoy the peak of the Lyrid meteor shower! Since the radiant originates near Vega, improve your odds of spotting them when the constellation Lyra is as high as possible. The Lyrid stream comes from parent comet Thatcher and produces about 15 bright, long-lasting meteors per hour.

Plan tonight to head into the Coma-Virgo galaxy cluster for more challenges. This time we’ll approach from Vindemiatrix (Epsilon Virginis) and move west-northwest along a chain of bright galaxies in the direction of distant Denebola. We’ll start with “Messier-quality” NGC 4762 followed by the M60, M59 and M58. Ready to starhop?

Our first stop lies a little more than a finger width west-northwest of Vindemiatrix: NGC 4762 is a 10.2 magnitude edge-on galaxy with a nearby 10.6 magnitude neighbor, NGC 4762. Most scopes show reveal a faint, thick lens-shaped patch of light oriented north-south. Like dozens of other bright NGC studies, NGC 4762 could have been discovered by Messier and friends in the eighteenth century – but wasn’t!

Continuing west-northwest another finger width reveals M60 – one of the brightest (magnitude 8.8) Coma-Virgo cluster members. This mid-sized elliptical galaxy condenses toward a bright core and shares the field with a pair of nearby companions (11.4 magnitude NGC 4647 and 11.3 magnitude NGC 4638). A touch west-northwest of the M60 group is a fainter (9.8) flattened elliptical galaxy M59. A bit further west is 10.9 magnitude galaxy NGC 4606 – a faint spindle of luminosity. All five of these galaxies can fit into a single low power field of view and will appear roughly as a line of nebulous islands hopping east to west!

Returning slightly east to center again on M59, we shift the scope a degree slightly north and further west to 9.8 magnitude M58. This small, face-on barred spiral is an original discovery of Messier – who found it along with M59 and 60 – while following a comet in the spring of 1779. Unknown to Messier was that the galaxies designated M59 and M60 in his log had already been discovered 4 days earlier (on April 11) by Johann Gottfried Koehler while pursuing the same comet!

Sunday, April 23 – Up early? Then be aware that the Moon occults Uranus. Check IOTA for details! Pioneering quantum physicist Max Planck was born this day in 1858. In 1900, Plank developed the equation explaining the distribution of light emitted by a theoretical “blackbody.” (Planck’s equation describes the relationship between the temperature of a body that absorbs all radiation falling on it – regardless of wavelength – and the wavelength of light radiated from that same body.) Interestingly, almost all the light seen in the heavens originates as “blackbody radiation” from the surface gases of stars. And where does the “absorbed light” come from? Nuclear fusion and the type of light that is far too vibrant for the human eye to see…

In honor of this principle, let’s turn our telescopes on the combined light of trillions of stars as we continue our exploration of the Coma-Virgo realm of galaxies leading up to the light of M87!

To begin tonight’s galaxy hop, start at Nu and extend a line to equal magnitude Omicron Virginis. Continuing the distance between Nu and Omicron places NGC 4429 at the northeast edge of a low power field. Fainter NGC 4371 may be seen less than a degree away northwest of NGC 4429. At magnitude 10.2, NGC 4429 appears about as luminous as previously studied M98. This near edge-on galaxy shows wispy spiral extensions and a bright star-like core.

Now move 1.5 degrees north for bright (magnitude 8.6) giant elliptical galaxy M87 – capital of the Coma-Virgo galaxy cluster. Look also for its 11.2 magnitude companion NGC 4478. Long exposure photographs of M87 reveal this 120,000 light year diameter radiant globe of luminosity is an “all stars” phenomenon. No matter what direction you might observe this giant from, you’d get almost precisely the same view – it’s similar to a massive globular cluster! M87 has collected tens of thousands of globular clusters, numerous smaller galaxies, and converted almost all of its matter to stars – a galaxy with a total mass exceeding several trillion suns.

Once you’ve located M87 it’s time to turn east-southeast (towards Vindemiatrix) for M58, M59, and M60. West-northwest is the direction of the “twin lenticular galaxies” – M84 and 86 – with their own galactic “field of dreams” – a place where large scopes can frame as many as a dozen galaxies in a single one degree field. Just a finger-width north of M87, you can find 9.5 magnitude tilted spiral M88 – looking like a “distant cousin” to the Great Galaxy in Andromeda seen from 60,000 million light years away. Had enough? No? Then head less than a degree west of M88 to find 10.2 magnitude barred spiral M91 in the same low power field. Less than a finger-width south-southeast of M91 is 9.5 magnitude M90 – another tilted spiral and one of eight galaxies (beginning with M84) found and later added to Messier’s list on the same productive night of March 18, 1781 (which also included the M92 globular cluster in Hercules.) How’s that for a night out under the stars?

May all your journeys be at light speed… ~Tammy Plotnerwith Jeff Barbour.

Posted on by Fraser Cain

Astrophoto: Zodiacal Light by Tony and Daphne Hallas


Zodiacal Light by Tony and Daphne Hallas

The night sky, from a dark location, is filled with many sights full of wonder to urban dwellers: the slow moving glint of a satellite solar array, the flash and occasional sonic repercussion of a meteor flailing overhead, the arc of combined luminosity from the Milky Way’s remote suns and the glow from high altitude cirrus present in Earth’s atmosphere. But at certain times of the year a few hours after sunset or before sunrise, a soft triangular shape will appear from the horizon extending upward that may lead you to believe the moon or the sun is about to rise. This explanation has passed through the minds of observers since antiquity and is called the false dawn… but, it is another thing altogether.

The Sun rules over a vast empire in the sky and around it circles a cortege of loyal subjects – noble planets with waists of varying proportion, their attendant moons in tow like guards and helpful servants, countless asteroids which make up the sky’s gentry and intermittent tourists on holiday from the kingdom’s outer provinces- the comets. But in between the sun and just outside the influence of Earth’s orbit is a vast cloud of interplanetary dust– crumbs fallen from the table during the feast of the solar system’s creation. Each tiny particle may be separated from its neighbor by up to five miles, thus this nebula is very thin. But its presence is apparent when sunlight glints off each fragment and you are standing beneath an exceptionally dark, clear night sky at the right time of the year.

Because the dust that creates this phenomenon resides within the same plane as the planets, it projects itself against the same constellations that the planets also pass, thus it is now known as the Zodiacal Light.

For those in the Northern Hemisphere, the best time to see this unique apparition is a few hours after sunset in the west between February and March and a few hours before dawn during October, over in the east. If you live in the Southern Hemisphere the best western view is during the evening from August to September or in the east during the early morning hours throughout April.

Over time, the dust that forms this cloud slowly spirals inward toward the sun. It is believed that the cloud regenerates itself from the debris that results in the collision of larger orbiting particles and from the tails of comets.

This exceptional picture of the Zodiacal Light was recently produced by Tony and Daphne Hallas from a location at Modoc Plateau, which lies in the northeast corner of California as well as parts of Oregon and Nevada. This area is one of the darkest sites in the continental United States and is home to a mile-high expanse of lava flows, cinder cones, pine forests and seasonal lakes. Daphne and Tony took this image with a Canon 20D digital camera using a 16-35mm f/2.8 lens.

Do you have photos you’d like to share? Post them to the Universe Today astrophotography forum or email them, and we might feature one in Universe Today.

Written by R. Jay GaBany

Posted on by Fraser Cain

Building an Antimatter Spaceship

A spacecraft powered by a positron reactor would resemble this artist's concept of the Mars Reference Mission spacecraft. Credit: NASA

If you’re looking to build a powerful spaceship, nothing’s better than antimatter. It’s lightweight, extremely powerful and could generate tremendous velocity. However, it’s enormously expensive to create, volatile, and releases torrents of destructive gamma rays. NASA’s Institute for Advanced Concepts is funding a team of researchers to try and design an antimatter-powered spacecraft that could avoid some of those problems.

Most self-respecting starships in science fiction stories use anti matter as fuel for a good reason – it’s the most potent fuel known. While tons of chemical fuel are needed to propel a human mission to Mars, just tens of milligrams of antimatter will do (a milligram is about one-thousandth the weight of a piece of the original M&M candy).

However, in reality this power comes with a price. Some antimatter reactions produce blasts of high energy gamma rays. Gamma rays are like X-rays on steroids. They penetrate matter and break apart molecules in cells, so they are not healthy to be around. High-energy gamma rays can also make the engines radioactive by fragmenting atoms of the engine material.

The NASA Institute for Advanced Concepts (NIAC) is funding a team of researchers working on a new design for an antimatter-powered spaceship that avoids this nasty side effect by producing gamma rays with much lower energy.

Antimatter is sometimes called the mirror image of normal matter because while it looks just like ordinary matter, some properties are reversed. For example, normal electrons, the familiar particles that carry electric current in everything from cell phones to plasma TVs, have a negative electric charge. Anti-electrons have a positive charge, so scientists dubbed them “positrons”.

When antimatter meets matter, both annihilate in a flash of energy. This complete conversion to energy is what makes antimatter so powerful. Even the nuclear reactions that power atomic bombs come in a distant second, with only about three percent of their mass converted to energy.

Previous antimatter-powered spaceship designs employed antiprotons, which produce high-energy gamma rays when they annihilate. The new design will use positrons, which make gamma rays with about 400 times less energy.

The NIAC research is a preliminary study to see if the idea is feasible. If it looks promising, and funds are available to successfully develop the technology, a positron-powered spaceship would have a couple advantages over the existing plans for a human mission to Mars, called the Mars Reference Mission.

“The most significant advantage is more safety,” said Dr. Gerald Smith of Positronics Research, LLC, in Santa Fe, New Mexico. The current Reference Mission calls for a nuclear reactor to propel the spaceship to Mars. This is desirable because nuclear propulsion reduces travel time to Mars, increasing safety for the crew by reducing their exposure to cosmic rays. Also, a chemically-powered spacecraft weighs much more and costs a lot more to launch. The reactor also provides ample power for the three-year mission. But nuclear reactors are complex, so more things could potentially go wrong during the mission. “However, the positron reactor offers the same advantages but is relatively simple,” said Smith, lead researcher for the NIAC study.

Also, nuclear reactors are radioactive even after their fuel is used up. After the ship arrives at Mars, Reference Mission plans are to direct the reactor into an orbit that will not encounter Earth for at least a million years, when the residual radiation will be reduced to safe levels. However, there is no leftover radiation in a positron reactor after the fuel is used up, so there is no safety concern if the spent positron reactor should accidentally re-enter Earth’s atmosphere, according to the team.

It will be safer to launch as well. If a rocket carrying a nuclear reactor explodes, it could release radioactive particles into the atmosphere. “Our positron spacecraft would release a flash of gamma-rays if it exploded, but the gamma rays would be gone in an instant. There would be no radioactive particles to drift on the wind. The flash would also be confined to a relatively small area. The danger zone would be about a kilometer (about a half-mile) around the spacecraft. An ordinary large chemically-powered rocket has a danger zone of about the same size, due to the big fireball that would result from its explosion,” said Smith.

Another significant advantage is speed. The Reference Mission spacecraft would take astronauts to Mars in about 180 days. “Our advanced designs, like the gas core and the ablative engine concepts, could take astronauts to Mars in half that time, and perhaps even in as little as 45 days,” said Kirby Meyer, an engineer with Positronics Research on the study.

Advanced engines do this by running hot, which increases their efficiency or “specific impulse” (Isp). Isp is the “miles per gallon” of rocketry: the higher the Isp, the faster you can go before you use up your fuel supply. The best chemical rockets, like NASA’s Space Shuttle main engine, max out at around 450 seconds, which means a pound of fuel will produce a pound of thrust for 450 seconds. A nuclear or positron reactor can make over 900 seconds. The ablative engine, which slowly vaporizes itself to produce thrust, could go as high as 5,000 seconds.

One technical challenge to making a positron spacecraft a reality is the cost to produce the positrons. Because of its spectacular effect on normal matter, there is not a lot of antimatter sitting around. In space, it is created in collisions of high-speed particles called cosmic rays. On Earth, it has to be created in particle accelerators, immense machines that smash atoms together. The machines are normally used to discover how the universe works on a deep, fundamental level, but they can be harnessed as antimatter factories.

“A rough estimate to produce the 10 milligrams of positrons needed for a human Mars mission is about 250 million dollars using technology that is currently under development,” said Smith. This cost might seem high, but it has to be considered against the extra cost to launch a heavier chemical rocket (current launch costs are about $10,000 per pound) or the cost to fuel and make safe a nuclear reactor. “Based on the experience with nuclear technology, it seems reasonable to expect positron production cost to go down with more research,” added Smith.

Another challenge is storing enough positrons in a small space. Because they annihilate normal matter, you can’t just stuff them in a bottle. Instead, they have to be contained with electric and magnetic fields. “We feel confident that with a dedicated research and development program, these challenges can be overcome,” said Smith.

If this is so, perhaps the first humans to reach Mars will arrive in spaceships powered by the same source that fired starships across the universes of our science fiction dreams.

Original Source: NASA News Release

Posted on by Fraser Cain

Titan and Epimetheus Behind the Rings

Titan and small Epimetheus behind Saturn’s rings. Image credit: NASA/JPL/SSI. Click to enlarge
This Cassini photograph shows Saturn’s large, smoggy moon Titan partly obscured by the planet’s rings. Another of Saturn’s moons, tiny Epimetheus, is visible as a dot just to the left of Titan. Cassini took this photograph on March 9, 2006 when it was approximately 4.1 million kilometers (2.5 million miles) from Titan.

This poetic scene shows the giant, smog-enshrouded moon Titan behind Saturn’s nearly edge-on rings. Much smaller Epimetheus (116 kilometers, or 72 miles across) is just visible to the left of Titan (5,150 kilometers, or 3,200 miles across).

The image was taken in visible light with the Cassini spacecraft narrow-angle camera on March 9, 2006, at a distance of approximately 4.1 million kilometers (2.5 million miles) from Titan. The image scale is 25 kilometers (16 miles) per pixel on Titan. The brightness of Epimetheus was enhanced for visibility.

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

Mars Reconnaissance Orbiter Adjusts its Orbit

The large Argyre Basin in Mars’ southern hemisphere. Image credit: NASA/JPL/MSSS. Click to enlarge
NASA’s Mars Reconnaissance Orbiter has sent back some new test images of the Martian surface, at a resolution of 2.5 metres/pixel. Once it reaches its final science orbit, the spacecraft will be 10 times closer to the planet, and the images will be even higher resolution. The spacecraft fired its thrusters on Wednesday to adjust its orbit so that it passed through Mars’ atmosphere. This maneuver is called aerobraking, and the spacecraft will make many of these passes over the next 6 months.

Researchers today released the first Mars images from two of the three science cameras on NASA’s Mars Reconnaissance Orbiter.

Images taken by the orbiter’s Context Camera and Mars Color Imager during the first tests of those instruments at Mars confirm the performance capability of the cameras. The test images were taken from nearly 10 times as far from the planet as the spacecraft will be once it finishes reshaping its orbit. Test images from the third camera of the science payload were released previously.

“The test images show that both cameras will meet or exceed their performance requirements once they’re in the low-altitude science orbit. We’re looking forward to that time with great anticipation,” said Dr. Michael Malin of Malin Space Science Systems, San Diego. Malin is team leader for the context camera and principal investigator for the Mars Color Imager.

The cameras took the test images two weeks after the orbiter’s March 10 arrival at Mars and before the start of “aerobraking,” a process of reshaping the orbit by using controlled contact with Mars’ atmosphere. This week, the spacecraft is dipping into Mars’ upper atmosphere as it approaches the altitude range that it will use for shrinking its orbit gradually over the next six months.

The orbiter is currently flying in very elongated loops around Mars. Each circuit lasts about 35 hours and takes the spacecraft about 27,000 miles (43,000 kilometers) away from the planet before swinging back in close.

On Wednesday, a short burn of intermediate sized thrusters while the orbiter was at the most distant point nudged the spacecraft to pass from approximately 70 miles (112 kilometers) to within 66 miles (107 kilometers) of Mars’ surface.

“This brings us well into Mars’ upper atmosphere for the drag pass and will enable the mission to start reducing the orbit to its final science altitude,” said Dan Johnston of NASA’s Jet Propulsion Laboratory, Pasadena, Calif., deputy mission manager.

After hundreds of passes through the upper atmosphere, the drag will gradually reduce the far point of the orbit until the spacecraft is in a nearly circular orbit every two hours.

After the spacecraft gets into the proper orbit for its primary science phase, the six science instruments on board will begin their systematic examination of Mars. The Mars Color Imager will view the planet’s entire atmosphere and surface every day to monitor changes in clouds, wind-blown dust, polar caps and other variable features.

Images from the Context Camera will have a resolution of 20 feet (6 meters) per pixel, allowing surface features as small as a basketball court to be discerned. The images will cover swaths 18.6 miles (30 kilometers) wide.

The Context Camera will show how smaller areas examined by the High Resolution Imaging Science Experiment Camera — which will have the best resolution ever achieved from Mars orbit — and by the mineral-identifying Compact Reconnaissance Imaging Spectrometer fit into the broader landscape. It will also allow scientists to watch for small-scale changes, such as newly cut gullies, in the broader coverage area.

The new test images from the Context Camera and the Mars Color Imager are available online at www.nasa.gov/mro , www.msss.com/mro/ctx/images/2006/04/13/ and www.msss.com/mro/marci/images/2006/04/13/ .

For more detailed information about Mars Reconnaissance Orbiter, see http://mars.jpl.nasa.gov/mro .

NASA’s Mars Reconnaissance Orbiter is managed by JPL, a division of the California Institute of Technology, Pasadena, for the NASA Science Mission Directorate, Washington. Lockheed Martin Space Systems, Denver, is the prime contractor.

Original Source: NASA News Release