Posted on by Fraser Cain

Astrophoto: Comet Schwassmann-Wachmann by Andrea Tamanti

Comet Schwassmann-Wachmann by Andrea Tamanti
Arnold Schwassmann and Arno Arthur Wachmann were two German astronomers credited with the discovery of three comets during the first third of the last century. Near the middle of this month, their third discovery will pass by Earth, twenty five times more distant than the Moon, on its latest five and a third year orbit from near the Sun to the distance of Jupiter.

Its small nucleus is approximately two tenths of a mile across – a size that is generally incapable of producing a spectacular show as it swings by Earth. Yet, two orbits ago, in 1995, the comet did something unexpected – it brightened considerably as it was observed breaking apart. This year, this comet will pass closer to Earth than any in the past twenty-five years. But this is no typical cometary flyby – Comet Schwassmann-Wachmann 3 has become a swarm of small comets!

During the 1995 passage, the nucleus of this comet split apart into three objects traveling single file but when it passed Earth during the fall of 2000, four separate nuclei were observed. Images captured in late March of this year revealed eight individual pieces and by April 10, scientists could see nineteen fragments and many of these were spawning even smaller pieces. Each piece is a mini-comet with its own star-like nucleus and tail.

Closest approach to the Sun will occur on June 7. But on May 8, a few days before their closest approach to Earth, the pieces of Comet Schwassmann-Wachmann will pass very close to the Ring Nebula in the constellation Lyra. Some fragments may even appear to pass over this famous night sky landmark. For folks living near Paris, this will occur around 5AM in the morning and for those who live on the southeast coast of the United States, a good view of this event will be happen about 11PM on May 7.

This excellent close up picture is of the comet’s “C” fragment- one of the three first seen in 1995. It was taken by Andrea Tamanti on April 24, 2006 at about 2AM local time from his home about 20 miles outside Rome, Italy. Andrea used a ten-inch Schmidt-Cassegrain telescope and a 1.3 mega pixel astronomical camera. Four separate exposures totaling 36 minutes were required to produce this full color image.

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

Shifting Northern Hazes on Titan

The hazy atmosphere of Titan. Image credit: NASA/JPL/SSI. Click to enlarge
This beautiful photograph shows how the hazy atmosphere on Saturn’s moon Titan is broken up into many layers. Titan’s north pole is at the upper left in this picture. Cassini took this image on March 16, 2006 when it was approximately 1.2 million kilometers (800,000 miles) from Titan.

The complex and dynamic atmosphere of Titan displays multiple haze layers near the north pole in this view, which also provides an excellent look at the detached stratospheric haze layer that surrounds the moon at lower latitudes.

North on Titan (5,150 kilometers, or 3,200 miles across) is up and rotated 20 degrees to the left.

The image was taken with the Cassini spacecraft narrow-angle camera on March 16, 2006, using a filter sensitive to wavelengths of ultraviolet light centered at 338 nanometers. The image was obtained at a distance of approximately 1.2 million kilometers (800,000 miles) from Titan and at a Sun-Titan-spacecraft, or phase, angle of 68 degrees. Image scale is 7 kilometers (5 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

Astronomers Look Inside a Neutron Star

The surface patterns for different torsional modes. Image credit: Max Planck. Click to enlarge
A massive explosion on the surface of a neutron star gave astronomers an opportunity to peer inside its surface, similar to how geologists understand the structure of the Earth beneath our feet. The explosion jolted the neutron star, and set it ringing like a bell. The vibrations then passed through layers of different density – slushy or solid – changing the X-rays streaming off. Astronomers calculated that it has a thicker crust approximately 1.6 km (1 mile) deep, matching theoretical estimates.

A US-German team of scientists from the Max Planck Institute for Astrophysics and NASA have used NASA’s Rossi X-ray Timing Explorer to estimate the depth of the crust on a neutron star, the densest object known in the universe. The crust, they say, is approximately 1.6 kilometres deep and so tightly packed that a teaspoon of this material would weigh about 10 million tonnes on Earth.

This measurement, the first of its kind, came courtesy of a massive explosion on a neutron star in December 2004. Vibrations from the explosion revealed details about the star’s composition. The technique is analogous to seismology, the study of seismic waves from earthquakes and explosions, which reveal the structure of the Earth’s crust and interior.

This new seismology technique provides a way to probe a neutron star’s interior, a place of great mystery and speculation. Pressure and density are so intense here that the core might harbour exotic particles thought to have existed only at the moment of the Big Bang.

Dr Anna Watts, of the Max Planck Institute for Astrophysics in Garching, carried out this research in collaboration with Dr. Tod Strohmayer of NASA’s Goddard Space Flight Center in Greenbelt, Maryland.

“We think this explosion, the biggest of its kind ever observed, really jolted the star and literally started it ringing like a bell,” said Strohmayer. “The vibrations created in the explosion, although faint, provide very specific clues about what these bizarre objects are made of. Just like a bell, a neutron star’s ring depends on how waves pass through layers of differing density, either slushy or solid.”

A neutron star is the core remains of a star once several times more massive than the sun. A neutron star contains about 1.4 solar masses of material crammed into a sphere only about 20 kilometres across. The two scientists examined a neutron star named SGR 1806-20, which is situated about 40,000 light years from Earth in the constellation Sagittarius. The object is in a subclass of highly magnetic neutron stars called magnetars.

On December 27, 2004, the surface of SGR 1806-20 experienced an unprecedented explosion, the brightest event ever seen from beyond our solar system. The explosion, called a hyperflare, was caused by a sudden change in the star’s powerful magnetic field that cracked the crust, likely producing a massive starquake. The event was detected by many space observatories, including the Rossi Explorer, which observed the X-ray light emitted.

Strohmayer and Watts think that the oscillations are evidence of global torsional vibrations within the star’s crust. These vibrations are analogous to the S-waves observed during terrestrial earthquakes, like a wave moving through a rope. Their study, building on observations of vibrations from this source by Dr. GianLuca Israel of Italy’s National Institute of Astrophysics, found several new frequencies during the hyperflare.

Watts and Strohmayer subsequently confirmed their measurements using NASA’s Ramaty High Energy Solar Spectroscopic Imager, a solar observatory that also recorded the hyperflare, and found the first evidence for a high-frequency oscillation at 625 Hz, indicative of waves traversing the crust vertically.

The abundance of frequencies – similar to a chord, as opposed to a single note – enabled the scientists to estimate the depth of the neutron star crust. This is based on a comparison of frequencies from waves travelling around the star’s crust and from those travelling radially through it. The diameter of a neutron star is uncertain, but based on the estimate of about 20 kilometres across, the crust would be about 1.6 kilometres deep. This figure, based on the observed frequencies, is in line with theoretical estimates.

Starquake seismology holds great promise for determining many neutron star properties. Strohmayer and Watts have analyzed archived Rossi data from a dimmer 1998 magnetar hyperflare (from SGR 1900+14) and found telltale oscillations here too, although not strong enough to determine the crust thickness.

A larger neutron star explosion detected in X-rays might reveal deeper secrets, such as the nature of matter at the star’s core. One exciting possibility is that the core might contain free quarks. Quarks are the building blocks of protons and neutrons, and under normal conditions are always tightly bound together. Finding evidence for free quarks would aid in understanding the true nature of matter and energy. Laboratories on Earth, including massive particle accelerators, cannot generate the energies needed to reveal free quarks.

“Neutron stars are great laboratories for the study of extreme physics,” said Watts. “We’d love to be able to crack one open, but since that’s probably not going to happen, observing the effects of a magnetar hyperflare on a neutron star is perhaps the next best thing.”

Original Source: Max Planck Society

Posted on by Fraser Cain

Merging Galaxies Surrounded by Newborn Stars

The cores of the two galaxies NGC 2207 and IC 2163. Image credit: NASA. Click to enlarge
The two “eyes” in this photograph are actually the cores of two merging galaxies; as viewed by NASA’s Spitzer Space Telescope. The galaxies are called NGC 2207 and IC 2163, and the surrounding material is their twisted spiral arms. Dotted along these arms are knotted clusters of newborn stars, created when the two galaxies smashed into each other. The pair is located 140 million light-years away in the Canis Major constellation, and they’ll eventually become a single galaxy in another 500 million years.

A pair of dancing galaxies appears dressed for a cosmic masquerade in a new image from NASA’s Spitzer Space Telescope.

The infrared picture shows what looks like two icy blue eyes staring through an elaborate, swirling red mask. These “eyes” are actually the cores of two merging galaxies, called NGC 2207 and IC 2163, which recently met and began to twirl around each other.

The “mask” is made up of the galaxies’ twisted spiral arms. Dotted along the arms, like strings of decorative pearls, are dusty clusters of newborn stars. This is the first time that clusters of this type, called “beads on a string” by astronomers, have been seen in NGC 2207 and IC 2163.

“This is the most elaborate case of beading we’ve seen in galaxies,” said Dr. Debra Elmegreen of Vassar College in Poughkeepsie, N.Y. “They are evenly spaced and sized along the arms of both galaxies.”

Elmegreen is lead author of a paper describing the Spitzer observations in the May 1 issue of the Astrophysical Journal.

Astronomers say the beads were formed when the galactic duo first met. “The galaxies shook each other, causing gas and dust to move around and collect into pockets dense enough to collapse gravitationally,” said Dr. Kartik Sheth of NASA’s Spitzer Science Center at the California Institute of Technology in Pasadena. Once this material condensed into thick bead-like clouds, stars of various sizes began to pop up within them.

Spitzer’s infrared camera was able to see the dusty clouds for the first time because they glow with infrared light. The hot, young stars housed inside the clouds heat up the dust, which then radiates at infrared wavelengths. This dust is false-colored red in the image, while stars are represented in blue.

The Spitzer data also reveal an unusually bright bead adorning the left side of the “mask.” This dazzling orb is so packed full of dusty materials that it accounts for five percent of the total infrared light coming from both galaxies. Elmegreen’s team thinks the central stars in this dense cluster might have merged to become a black hole.

Visible-light images of the galaxies show stars located inside the beads, but the beads themselves are invisible. In those pictures, the galaxies look more like a set of owl-like eyes with “feathers” of scattered stars.

NGC 2207 and IC 2163 are located 140 million light-years away in the Canis Major constellation. The two galaxies will meld into one in about 500 million years, bringing their masquerade days to an end.

Other authors of this research include Bruce Elmegreen of IBM Watson Research Center, Yorktown Heights, N.Y., Michele Kaufman of Ohio State University, Columbus; Curt Struck of Iowa State, Ames; Magnus Thomasson of Onsala Space Observatory, Sweden; and Elias Brinks of the University of Hertfordshire, United Kingdom.

The Jet Propulsion Laboratory manages the Spitzer Space Telescope mission for NASA’s Science Mission Directorate, Washington. Science operations are conducted at the Spitzer Science Center at Caltech. JPL is a division of Caltech. Spitzer’s infrared array camera was built by NASA’s Goddard Space Flight Center, Greenbelt, Md. The instrument’s principal investigator is Dr. Giovanni Fazio of the Harvard-Smithsonian Center for Astrophysics.

Original Source: Spitzer Space Telescope

Posted on by Fraser Cain

How Do Fossil Galaxy Clusters Form so Quickly?

Fossil galaxy cluster as observed by XMM-Newton. Image credit: ESA. Click to enlarge
Galaxies start small, but grow over time as they merge with other galaxies. After a while, however, the nearby space runs out of galaxies to merge with. All that’s left is one large galaxy called a fossil group, which sits inside an even larger halo of dark matter. Astronomers are puzzled at how these fossil groups are able to form rapidly – some shouldn’t be able to do it in the lifetime of the Universe. New observations from Chandra and ESA’s XMM-Newton observatories have provided new clues about how these clusters collapse and form.

Taking advantage of the high sensitivity of ESA’s XMM-Newton and the sharp vision of NASA’s Chandra X-Ray space observatories, astronomers have studied the behaviour of massive fossil galaxy clusters, trying to find out how they find the time to form.

Many galaxies reside in galaxy groups, where they experience close encounters with their neighbours and interact gravitationally with the dark matter – mass which permeates the whole intergalactic space but is not directly visible because it doesn’t emit radiation.

These interactions cause large galaxies to spiral slowly towards the centre of the group, where they can merge to form a single giant central galaxy, which progressively swallows all its neighbours.

If this process runs to completion, and no new galaxies fall into the group, then the result is an object dubbed a ‘fossil group’, in which almost all the stars are collected into a single giant galaxy, which sits at the centre of a group-sized dark matter halo. The presence of this halo can be inferred from the presence of extensive hot gas, which fills the gravitational potential wells of many groups and emits X-rays.

A group of international astronomers studied in detail the physical features of the most massive and hot known fossil group, with the main aim to solve a puzzle and understand the formation of massive fossils. In fact, according to simple theoretical models, they simply could not have formed in the time available to them!

The fossil group investigated, called ‘RX J1416.4+2315’, is dominated by a single elliptical galaxy located one and a half thousand million light years away from us, and it is 500 thousand million times more luminous than the Sun.

The XMM-Newton and Chandra X-ray observations, combined with optical and infrared analyses, revealed that group sits within a hot gas halo extending over three million light years and heated to a temperature of 50 million degrees, mainly due to shock heating as a result of gravitational collapse.

Such a high temperature, about as twice as the previously estimated values, is usually characteristic of galaxy clusters. Another interesting feature of the whole cluster system is its large mass, reaching over 300 trillion solar masses. Only about two percent of it in the form of stars in galaxies, and 15 percent in the form of hot gas emitting X-rays. The major contributor to the mass of the system is the invisible dark matter, which gravitationally binds the other components.

According to calculations, a fossil cluster as massive as RX J1416.4+2315 would have not had the time to form during the whole age of the universe. The key process in the formation of such fossil groups is the process known as ‘dynamical friction’, whereby a large galaxy loses its orbital energy to the surrounding dark matter. This process is less effective when galaxies are moving more quickly, which they do in massive ‘clusters’ of galaxies.

This, in principle, sets an upper limit to the size and mass of fossil groups. The exact limits are, however, still unknown since the geometry and mass distribution of groups may differ from that assumed in simple theoretical models.

“Simple models to describe the dynamical friction assume that the merging galaxies move along circular orbits around the centre of the cluster mass”, says Habib Khosroshahi from the University of Birmingham (UK), first author of the results. “Instead, if we assume that galaxies fall towards the centre of the developing cluster in an asymmetric way, such as along a filament, the dynamic friction and so the cluster formation process may occur in a shorter time scale,” he continues. Such a hypothesis is supported by the highly elongated X-ray emission we observed in RX J1416.4+2315, to sustain the idea of a collapse along a dominant filament.”

The optical brightness of the central dominant galaxy in this fossil is similar to that of brightest galaxies in large clusters (called ‘BCGs’). According to the astronomers, this implies that such galaxies could have originated in fossil groups around which the cluster builds up later. This offers an alternative mechanism for the formation of BCGs compared to the existing scenarios in which BCGs form within clusters during or after the cluster collapse.

“The study of massive fossil groups such as RX J1416.4+2315 is important to test our understanding of the formation of structure in the universe,” adds Khosroshahi. “Cosmological simulations are underway which attempt to reproduce the properties we observe, in order to understand how these extreme systems develop,” he concludes.

Original Source: ESA News Release

Posted on by Fraser Cain

Pheonix Mars Lander is Coming Together

Artist’s concept of Phoenix spacecraft. Image credit: NASA. Click to enlarge
NASA’s next mission to the Red Planet, the Phoenix Mars Lander, is coming together in preparation for its August 2007 launch. Engineers are now incorporating many of its subsystems, including the flight computer, power systems and science instruments. If all goes well, the spacecraft will land near Mars’ north polar ice cap, and analyze samples that it scoops up from the icy soil.

NASA’s Phoenix Mars Lander, the next mission to the surface of Mars, is beginning a new phase in preparation for a launch in August 2007.

As part of this “assembly, test and launch operations” phase, Phoenix team members are beginning to add complex subsystems such as the flight computer, power systems and science instruments to the main structure of the spacecraft. The work combines efforts of Lockheed Martin Space Systems, Denver; the University of Arizona, Tucson; and NASA’s Jet Propulsion Laboratory, Pasadena, Calif.

“All the subsystems and instruments from a wide range of suppliers are tested separately, but now we are beginning the vital stage of assembling them together and testing how they will function with each other,” said JPL’s Barry Goldstein, project manager for Phoenix.

Phoenix will land near the red planet’s north polar ice cap to analyze scooped-up samples of icy soil.

“We know there is plenty of water frozen into the surface layer of Mars at high latitudes. We’ve designed Phoenix to tell us more about this region as a possible habitat for life,” said the University of Arizona’s Peter Smith, principal investigator for the mission.

Phoenix is the first mission of NASA’s Mars Scout Program of competitively proposed, relatively low-cost missions to Mars. The program is currently soliciting proposals for a 2011 Scout mission.

The Phoenix proposal, selected in 2003, saves expense by using a lander structure, subsystem components and protective aeroshell originally built for a 2001 lander mission that was canceled while in development. The budget for the Phoenix mission, including launch, is $386 million.

The spacecraft will land using descent thrusters just prior to touchdown, rather than airbags like those used by the current Mars Exploration Rovers. As Phoenix parachutes through Mars’ lower atmosphere in May 2008, a descent camera will take images for providing geological context about the landing site.

The robotic arm being built for Phoenix will be about 2 meters (7 feet) long, jointed at the elbow and wrist, and equipped with a camera and scoop. It will dig as deep as about 50 centimeters (20 inches) and deliver samples to instruments on the spacecraft deck that will analyze physical and chemical properties of the ices and other materials. A stereo color camera will examine the landing site’s terrain and provide positioning information for the arm. The Canadian Space Agency is providing a suite of weather instruments for Phoenix.

“The propulsion system and the wiring harness have been added to the vehicle,” said Ed Sedivy, Phoenix program manager for Lockheed Martin. “We will be loading flight software onto the flight computer in the next few days. The flight software is much more mature than typical for a planetary program at this stage. As soon as the flight computer is mated up, we can apply external power to the vehicle.”

Navigation components, such as star trackers, and communication subsystems will become part of the spacecraft in coming weeks, followed by science instruments in the summer.

Phoenix will be shipped to NASA’s Kennedy Space Center, Florida, in May 2007, for final preparations leading up to launch. Before that, testing in Colorado will subject the spacecraft to expected operational environments. This includes thermal and vacuum tests simulating the 10-month trip to Mars and conditions on Mars’ surface. Meanwhile, the mission is preparing a test facility in Tucson for practicing and testing procedures for operating the spacecraft on Mars.

JPL, a division of the California Institute of Technology, Pasadena, manages Phoenix for NASA’s Science Mission Directorate.

For information about NASA and agency programs on the Web, visit http://www.nasa.gov . For information about the Phoenix Mission to Mars on the Web, visit http://phoenix.lpl.arizona.edu.

Original Source: NASA News Release

Posted on by Fraser Cain

Nanedi Valles on Mars

This image, taken by ESA’s Mars Express spacecraft, shows the Nanedi Valles region of Mars. These steep sided channels range in width from a few hundred meters to more than 5km (3 miles) across, and look like they were formed by quickly flowing water. But their origin is debated by researchers. Some think that liquid flowed under the surface and the ground collapsed above it, while others think that water did once flow on the surface.

These images, taken by the High Resolution Stereo Camera (HRSC) on board ESA’s Mars Express spacecraft, show the Nanedi Valles valley system, a steep-sided feature that may have been formed in part by free-flowing water.

The HRSC obtained these images on 3 October 2004 during orbit 905 at a ground resolution of approximately 18 metres per pixel. The images have been rotated 90 degrees clockwise, so that north is to the right.

They show the region of Nanedi Valles, a roughly 800-kilometre valley extending southwest-northeast and lying at approximately 6.0 degrees North and 312 degrees East in the region of Xanthe Terra, southwest of Chryse Planitia.

In the colour image, Nanedi Valles ranges from approximately 0.8- to 5.0-kilometre wide and extends to a maximum of about 500 metres below the surrounding plains. This valley is relatively flat-floored and steep-sloped, and exhibits meanders and a merging of two branches in the north.

The origin of these striking features remains heavily debated.

***image4:left***Some researchers point to sapping (erosion caused by ground-water outflow), while others suggest that flow of liquid beneath an ice cover or collapse of the surface in association with liquid flow is responsible for the valley’s formation.

While the debate continues, it seems likely that some sort of continuous flow rather than a single flooding event created these features.

By studying Nanedi Valles, scientists hope to better understand the climatic evolution of the Red Planet. The stereo and colour capabilities of the HRSC camera enable scientists to study the planet’s morphology, while researchers can analyse reflected light at different wavelengths to better recognise the various geologic units within a scene.

The colour images have been derived from the three HRSC colour channels and the nadir channel. The anaglyph image was calculated from the nadir and one stereo channel.

Original Source: ESA Mars Express

Posted on by Fraser Cain

Starburst Galaxy M82 by Hubble

Cigar galaxy M82 captured by Hubble. Image credit: NASA/ESA/STScI. Click to enlarge
To celebrate 16 years of observations by the Hubble Space Telescope, NASA and ESA have released this image of galaxy M82 (aka the Cigar Galaxy). Located 12 million light-years away in the constellation Ursa Major, it’s an amazing example of a starburst galaxy. New stars are being born at the heart of M82 at a rate of 10 times what we see in our own Milky Way galaxy. The combined solar winds from all these stars creates a galactic “superwind” that compresses gas further out in the disk and leads to even more star formation.

To celebrate the NASA-ESA Hubble Space Telescope’s 16 years of success, the two space agencies are releasing the sharpest wide-angle view ever obtained of Messier 82 (M82), a galaxy remarkable for its webs of shredded clouds and flame-like plumes of glowing hydrogen blasting out from its central regions.

Located 12 million light-years away, M82 appears high in the northern spring sky in the direction of the constellation Ursa Major, the Great Bear. It is also called the ‘Cigar Galaxy’ because of the elongated elliptical shape produced by the tilt of its starry disk relative to our line of sight.

As shown in this mosaic image, M82 is a magnificent starburst galaxy. Throughout its central region young stars are being born ten times faster than they are inside in our Milky Way Galaxy.

These numerous hot new stars not only emit radiation but also charged particles that form the so-called stellar wind. Stellar winds streaming from these stars combine to form a galactic ‘superwind’.

The superwind compresses enough gas to trigger the ignition of millions more stars and blasts out towering plumes of hot ionised hydrogen gas, above and below the disk of the galaxy (seen in red in the image).

In M82 young stars are crammed into star clusters. These then congregate by the dozen to make the bright patches or ‘starburst clumps’ seen in the central parts of M82. The individual clusters in the clumps can only be distinguished in the ultra-sharp Hubble images.

Most of the pale objects sprinkled around the main body of M82 that look like fuzzy stars are actually star clusters about 20 light-years across and containing up to a million stars.

The rapid rate of star formation in this galaxy will eventually be self-limiting. When star formation becomes too vigorous, it destroys the material needed to make more stars. So the starburst will eventually subside, probably in a few tens of millions of years.

The observation was made in March 2006 with the Advanced Camera for Surveys’ Wide Field Channel. Astronomers assembled the six-image composite mosaic by combining exposures taken with four coloured filters. These capture starlight from visible and infrared wavelengths as well as the light from the glowing hydrogen filaments.

Original Source: ESA News Release

Posted on by Fraser Cain

Astrophoto: The Ring Nebula by Stefan Heutz

The Ring Nebula by Stefan Heutz. Click to enlarge
When stars similar to our Sun have exhausted their nuclear fuel, they release their outer layer into a beautiful expanding sphere that resembles a planet through a small telescope. The Ring Nebula, pictured here, is one of the most famous examples in the northern sky. But it’s not a sphere. There is another geometry that more accurately explains its beautiful appearance.

Riding high in the northern sky near the bright white star Vega, the Ring Nebula is one of the most favorite deep sky objects targeted visually by backyard stargazers. It can be seen through telescopes with apertures as small as four inches. But larger telescopes can reveal the faint planet sized central star that created this night sky spectacle. The Ring Nebula was discovered about 200 years ago by French astronomer Charles Messier, an avid comet hunter, and made its way into his catalog used to keep track of false comets as item number 57.

Recent imagery by the Hubble Space Telescope has confirmed that the Ring Nebula is not spherical in shape; it is more like a tube that is slightly constricted in the middle so that it resembles a stretched hourglass. By chance alone, Earth is positioned so that we can look almost straight through from one end. Tubular shapes like this are common throughout the universe because thick disks of gas tend to expand outward very slowly leaving the material free to become extended perpendicularly. One of the other more spectacular examples of this shape is exhibited by the Little Dumbbell Nebula. It’s located in the constellation of Perseus and is positioned so that we have a side view.

The diameter of the nebula’s walls is approximately one light year across. The view we see is actually quite ancient because the light reaching our eyes today departed for Earth about 2,000 years ago.

This beautiful image represents one of the best views taken from our planet’s surface. It was produced by German astro-photographer Stefan Heutz from his backyard imaging location though an eleven-inch Schmidt-Cassegrain telescope and a 1.5 mega-pixel camera. The light for this image was gathered on June 7, 2005 and represents 46 minutes of total exposure.

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

What’s Up This Week – April 24 – April 30, 2006

M3 – Credit: S. Kalfa and K. Honeycutt/Indiana University/WIYN/NAOA/NSF

Greetings fellow SkyWatchers! If you haven’t had a chance to observe Comet 73/P Schwassmann-Wachmann yet, right now is a good time as it sweeps through Coma Berenices. This week hosts galaxy studies and meteor showers, so enjoy darker skies – because…

Here’s what’s up!

Monday, April 24 – Before dawn, Venus and the Moon have a very close encounter. Today in 1970, China launched its first satellite – the beginnings of a national space program that later saw its first “taikonaut” in space.

Tonight, let’s use our binoculars and telescopes and take a break from galaxy quest. An alternative is to find one of the best northern hemisphere globular clusters – M3. You can locate M3 easily by identifying Cor Caroli (Alpha Canes Venatici) and Arcturus. Sweep your binoculars along a line halfway between the two and you will uncover this condensed beauty just east of Beta Comae. With added inches and magnification, the stars are out to play!

Discovered by Charles Messier on May 3, 1764, this condensed ball of approximately a half million stars is one of the oldest formations in our galaxy. At 35-40,000 light years distant, this awesome globular cluster spans 220 light years and is believed to be 10 billion years old.

Tuesday, April 25 – Today marks the 15th anniversary of the deployment of the Hubble Space Telescope (HST). While everyone in the astronomical community is aware of what this magnificent telescope “sees,” did you know that you can see it with just your eyes? The HST as a satellite can be tracked and observed. Visit the website Heavens-Above and enter your location. This will provide you with a list of times for visible satellite passes from your locale. Although you can’t see a detailed view of the satellite itself from Earth, it’s great fun to use binoculars and watch the Sun glint off all those highly polished surfaces!

Keep a watch on the skies tonight as the Mu Virginid meteor shower reaches its peak of 7 to 10 visible trails per hour. With the dark skies this evening, you might catch one of these medium speed meteors radiating from a point near the constellation of Libra.

Tonight is another “Missed Messier” – 8.9 magnitude NGC 3521. Often ignored by observers because of its isolated location in southern Leo, this tilted galaxy is a “must see” and fine representative of the grand spiral tradition. A delight even in small instruments, the galaxy reveals definite spiral structure in larger scopes and has been compared to M63 in overall structure.

To locate NGC 3521, start at Sigma Leonis and head almost three degrees south to 10.3 magnitude NGC 3640. Power up for a view of this oval-shaped elliptical beauty – then resume your quest for NGC 3521 by heading south-southwest another 1.5 degrees to 75 Leonis. Continue a little more than a finger-width south-southwest to 69 Leonis. NGC 3521 is located a finger-width due west of 69 Leonis.

Now that’s “star hopping’!

Wednesday, April 26 – If you’re up before dawn this morning, be sure to look for Mercury just slightly south of the Moon! On this date in 1920, the Shaply-Curtis debate raged in Washington DC on the nature and distance of spiral nebulae. Shaply contended that all such were part of one huge galaxy – the Milky Way, while Curtis maintained that they were distant galaxies all their own.

Thirteen years later on the same date, Arno Penzias was born. Penzias went on to become a Nobel Prize winner for his part in the discovery of cosmic microwave background radiation (CMBR) through the use of a simple horn-shaped antenna. Their discovery helped further our understanding of cosmology in ways that Shaply and Curtis could have never dreamed!

By 1850, Lord Rosse had used the 72 inch speculum-mirrored “Leviathon at Parsontown” (Birr Castle, Ireland) to catalogue fourteen previously indecipherable glowing clouds in deep space as “spiral nebulae.” The very first one resolved was originally a discovery of Charles Messier – found while chasing a comet on the night of October 13, 1773. That discovery, M51, had to wait 72 years until large reflecting telescopes unveiled its spiral form. It would take another 75 years before M51’s extragalactic nature became an indisputable fact!

Interestingly, observers have now become so accustomed to seeing spiral structure in brighter galaxies that even mid-sized scopes can see M51 – the Whirlpool Galaxy – as a “Grand Spiral.” Tonight see what Rosse saw for yourself.

Start in Ursa Major by locating Mizar (Zeta) and Alkaid (Eta), then rotate the line between these two 90 degrees south using Eta as the pivot. With the line oriented to the southwest, cut it in half. With good conditions and a mid-sized scope, you can be initiated into the mystery of the spiral nebulae – nebulae whose individual stars had to await the development of very large professional scopes and long-exposure photography to reveal their stellar nature to the questing human imagination!

Thursday, April 27 -Tonight is New Moon and a great time to “go deep!”

Start with M87 and fade a degree west for the and neighboring M86. These two massive galaxies can be revealed with almost any optical aid. They appear as a matched set of isolated ellipticals – but on an exceptional night, even small scopes will show much more to this region. The western member of the pair ? the M84 – appears slightly brighter and visibly smaller than the M86 yet the nucleus of M86 is broader, and less intensely brilliant. In large scopes, these two galaxies “leap” out of the eyepiece even at modest magnifications yet reveal no additional structure.

The most fascinating characteristic of the area becomes apparent when looking around M84 and M86. Within the same low power field, no less than five additional galaxies may be made out in a 6″ scope. Forming an easy triangle with the two Messiers, lies southern NGC 4388. At magnitude 11, this edge-on spiral shows a dim star-like core, and reveals classic edge-on structure at double the aperture. In the midst of the triangle formed by the two Messiers and NGC 4388, is 12th magnitude NGC 4387. This dim galaxy will only display a faintly stellar nucleus at mid-aperture, while larger scopes will see a very small face-on spiral with a bright nucleus. Just north of M86 is even dimmer NGC 4402. Like NGC 4388, NGC 4402 demands higher magnifications for positive identification through modest aperture scopes, and at large power you may notice a dust lane with the central core as a curved “bar” of light.

We’ve now gone as “deep” as we can. East of M86 are two brighter NGC galaxies – 4435 and 4438. Through a 6″ scope, NGC 4435 is easily picked out at low power with its simple star-like core and wispy round mantle. NGC 4438 is dim, but even with large aperture elliptical galaxies tend to be rather uninteresting creatures. The beauty of? NGC 4435 and? 4438 are simply their proximity to each other. NGC 4435 shows true elliptical structure, evenly illuminated and visibly faded toward the edges. But, 4438 is quite a different story! This elliptical is much more elongated. A highly conspicuous wisp of galactic material can be seen stretching back toward the brighter, nearby galaxy pair M84/86.

Friday, April 28 – Today was a busy day in astronomical history. Isaac Newton published his Principia in 1686. Newton was an obscure mathematician and early physicist who developed a new form of mathematics to describe planetary motion. In 1774, Francis Baily was born. Baily went on to revise star catalogs and explain the phenomenon now known as “Baily’s Beads” – seen at the start and end of a total solar eclipse. 1900 saw the birth of Jan Hendrick Oort, who quantified the Milky Way’s rotation and envisioned a vast, spherical area of comets outside the solar system now called the Oort Cloud. Today (in 1906) was also the birth date of Bart Jan Bok who studied the structure and dynamics of the Milky Way galaxy and like Oort had a class of objects – Bok Globules – named after him.

And the Milky Way is nowhere to be found! This is the reason we can see so many galaxies during the spring season. The great realm of galaxies we call the “Coma-Virgo Galaxy Cluster” has more in common with our own galaxy than simply not being hidden by the vast array of stars, gas, and dust. Our galaxy and its neighbors (making up the “Local Group”) are inexorably being drawn toward this massive assemblage of island universes based on forces first described by Isaac Newton. Yes, we are slipping. Slipping into a vast gravity well whose center is the giant elliptical galaxy M87!

For skywatchers, no equipment is necessary to enjoy the Alpha Bootid meteor shower tonight. Pull up a comfortable seat and face toward orange Arcturus climbing skyward 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.

Saturday, April 29 -Tonight see if you can spot the tender beginnings of the Moon after sunset. Observers take pleasure in sweeping the sky with small scopes and binoculars in hopes of finding the thinnest possible lunar crescent. This technique is also employed to turn up “the inferior planets” – Venus and Mercury. But both planets rise just before the Sun! If you rise early, look for them both about an hour before dawn.

Tonight let’s take advantage of dark sky and track down one of the most distant observable studies in the Universe that can be seen in amateur equipment – 2 billion light year distant quasar 3C273. You will need aperture – at least 8″ – and a star chart showing the detailed field in which the quasar is located. This study is so distant that we can only see its super-luminous radiant core looking precisely like a faint 13th magnitude blue star!

Start by re-locating M61 and drop 2.5 degrees southeast for the approximate location of a quasar 3c273 – the incredibly luminous core of a brilliant galaxy possessed of a super-supermassive black hole of more than 500 million solar masses. A galaxy whose brilliance is such that it would almost outshine our own Sun were it placed 33 light years (1 parsec) away and outshine all the light of the Milky Way galaxy 100 times over!

To verify 3C273, you will need a detailed star chart. But knowing you’re looking at one of the most distant objects an amateur can see makes it worth the hunt!

Sunday, April 30 – Karl 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 heliotrope. 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. It’s stuffed with wonderful features such as the Tarantula Nebula – the largest diffuse nebula known in the Universe. It also holds many star clusters, so get out those telescopes and binoculars and explore for your friends in the northern hemisphere!

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