An infrared camera aboard NASA’s Cassini spacecraft has discovered a unique aurora lighting up Saturn’s polar cap. The mysterious new aurora is unlike any other known in our solar system. “We’ve never seen an aurora like this elsewhere,” said Tom Stallard, an RCUK Academic Fellow working with Cassini data at the University of Leicester. Stallard is lead author of a paper released today (13th
November) in the journal Nature. “It’s not just a ring of aurorae like those we’ve seen at Jupiter or Earth. This one covers an enormous area across the pole. Our current ideas on what forms Saturn’s aurorae predict that this region should be empty, so finding such a bright one here is a fantastic surprise.”
Aurorae are caused when charged particles stream along the magnetic field of a planet and into its atmosphere. On Earth these charged particles come from the solar wind – a stream of particles that
emanates from the Sun.
Jupiter’s main auroral ring, caused by interactions internal to Jupiter’s magnetic environment, is constant in size. Saturn’s main aurora, which is caused by the solar wind, changes size dramatically as the wind varies. The newly observed aurora at Saturn, however, doesn’t fit into either category.
“Saturn’s unique auroral features are telling us there is something special and unforeseen about this planet’s magnetosphere and the way it interacts with the solar wind and the planet’s atmosphere,” said
Nick Achilleos, Cassini scientist on the Cassini magnetometer team at the University College London. “Trying to explain its origin will no doubt lead us to physics which uniquely operates in the environment of Saturn.” Saturn's aurora in Ultraviolet from Hubble.Credits: J.T. Trauger (Jet Propulsion Laboratory) and NASA.
The new infrared aurora appears in a region hidden from NASA’s Hubble Space Telescope, which has provided views of Saturn’s ultraviolet aurora. Cassini observed it when the spacecraft flew near Saturn’s polar region. In infrared light, the aurora sometimes fills the region from around 82 degrees north all the way over the pole. This new aurora is also constantly changing, even disappearing within a 45 minute-period.
The constellation of Hydrus was originally created by Petrus Plancius from the observations of Dutch sea navigators Pieter Dirkszoon Keyser and Frederick de Houtman when exploring the southern hemisphere and should not be confused with its more northerly counterpart – Hydra. Hydruss’ stellar patterns became known when it appeared on a celestial globe in 1597 and was considered a constellation when it was added to Johann Bayer’s Uranometria catalog in 1603. It survived the years to become one of the 88 modern constellations recognized by the International Astronomical Union. Hydrus is a southern circumpolar constellation and covers approximately 243 square degrees of sky. It contains 3 major stars which make up its asterism and 19 stars which have Bayer/Flamsteed designations. Hydrus is bordered by the constellations of Dorado, Eridanus, Horologium, Mensa, Octans, Phoenix, Reticulum and Tucana. It can be seen by observers located at at latitudes between +8° and ?90° and is best visible at culmination during the month of November.
Because Hydrus wasn’t visible to the ancient Greeks or Romans, no mythology surrounds this constellation. It is, however, just another example of how constellation names and figures can sometimes repeat themselves, like Ursa Major and Minor, Canis Major and Minor, Pegasus and Equuleus, Leo and Lynx… Perhaps the ancient Maori had legends about this handful of stars! To them, the Hydrus was the water snake who killed crocodiles by entering into their mouths and killing them from the inside…
Let’s begin our binocular tour with the second brightest of the stars – Alpha Hydri – the “a” symbol on our map. Once upon a time in the year 2900 BC, this happy little F class dwarf star had the honor of being the southern pole star. Thanks to the precession of the equinoxes, it has long since moved away, but continues to be of interest as it gears up to become a red giant star. Rotating completely on its axis about every 26 hours, all of Alpha’s exterior activity happens acoustically rather than magnetically. Why? Because 71 light year distant Alpha has a high metal content!
Now, drop south for Beta Hydri – the “B” symbol on our map. In binoculars you’ll see a nice visual double star. Beta is located 24.4 light years from our solar system and right now serves the distinction of being the brightest star closest to the south celestial pole. What’s special about it? What you’re looking at is nearly a duplicate of our own Sun. While it is just slightly larger and brighter, Beta is most definitely a subgiant near or at the end of its hydrogen fusing life – on its way to becoming a red giant no larger than the orbit of Earth. Its maximum rotation period is 29 days, very near to that of the 24 day cycle of Sol and its evolutionary fate appears to be similar – a “one day” white dwarf star.
Hop north and east for Gamma Hydri – the “Y” shape on our map. If you think you’re seeing red compared the the soft yellow-white of the other stars – you’re right. Gamma is a luminous class M red giant star that has signed off core hydrogen fusion and is approaching the end of its life span. While it is not terribly large – not even the size of the orbit of Mercury compared to our Sun, Gamma puts out some real stellar luminosity – shining 650 times brighter than Sol. This may be because it is firing up its helium to fuse carbon and oxygen… or it may have depleted its helium and is about to toss off its outer envelope and become a dead, white dwarf!
Before we move on, let’s head back north… Stopping first to pay our respects to visual double star Pi 1 Hydri – a non-interacting pair of 6th magnitude giants. Look closely because Pi 1 is red and Pi 2 is orange! Now, hop east to Eta 2 – the “n 2” symbol on our map. What’s so special about Eta 2? First off, Eta Hydri is a double star – a true binary star consisting of a blue-white dwarf called Eta 1 and a yellow giant star, Eta 2. But hey, that’s not what really fun. What’s really run is there is a giant planet orbiting around Eta 2! It’s about 217 light years from Earth and it goes by the very unromantic name of HD 11977 b. Sure, it’s about six and a half times the size of Jupiter, which puts it right up there at dead star size… But hey! It’s a planet! This means at least a few intermediate-mass stars could host substellar companions – either planets or brown dwarfs. When later measured by Doppler, science proved HD 11977 b was clearly within the planetary mass and became the first to be accurately determined.
Are you ready for a true telescope challenge? Hydra isn’t precisely known for bright objects, so our first is IC 1717 (RA 01h 32m 30.0s Dec -67 32′ 12.0″). What is it? Well… nothing. The only thing we really know for sure it that something was there when Dreyer cataloged this position because Dreyer was exceedingly good at his job. Maybe it was a comet… Maybe it was something variable. It never hurts to look!
Just in case you have an small telescope, you might want to try NGC 1466 (RA 03:44.5 Dec -71:41). This 11.5 magnitude globular cluster doesn’t belong to the Milky Way Galaxy… it belongs to the Large Magellanic Cloud. Even that far away, science has been able to spot that it has 44 RR Lyra type variable stars and is every bit as old as the galaxy halo to which it belongs!
For large telescopes, try NGC 1511 (RA 3:59.5 Dec -67:38), too. This ‘object’ is actually a triple set of galaxies whose co-ordinates are so close to one another that they almost appear as one unit. Interacting galaxies? You bet. This galaxy collision is a process that’s been going on for a billion years and will eventually become a giant elliptical galaxy at then end. Chances are NGC 1511 has already absorbed at least one galaxy in its past. According to scientists, “the peculiar optical ridge to the east of NGC 1511 is probably the stellar remnant of a galaxy completely disrupted by interactions with NGC 1511”.
Chandrayaan-1's first picture of the Moon. Credit: ISRO
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UPDATE: The Indian Space Research Organization (ISRO) announced on 11/12 that the 100 km science orbit has been successfully achieved. Congrats to the Chandrayaan-1 team!
India’s space agency released the first picture of the Moon taken by the Chandrayaan-1 spacecraft. While it’s not a superlative image, as Emily Lakdawalla from the Planetary Society blog says, it is a milestone. Emily also explained that this photo has a resolution more than 3,000 times poorer than the eventual science images will have because the camera on Chandrayaan-1 was designed to take images from an a 100-kilometer science orbit (this image was taken on Nov. 4 at 311,200 kilometers away from the Moon). And today, the spacecraft got closer to that final science orbit by firing its engines for 31 seconds, reducing its perigee (nearest distance to the moon) from 187 km to 101 km.
Chandrayaan-1’s orbit is still elliptical, and its apogee (farthest distance from the moon) is now 255 km. In this orbit, Chandrayaan-1, takes two hours and nine minutes to go around the Moon. On Wednesday evening, the Spacecraft Control Centre at Bangalore will issue commands for the spacecraft to fire its engines again to reduce the apogee to 100 km, putting the spacecraft into its final science orbit.
Then, on either Nov. 14 or 15, the Moon Impact Probe will be released. It weighs 35 kg, and once released will take about 25 minutes to impact. It will hit a pre-selected location (Chandrayaan-1 Twitter says to keep an eye on Shackleton Crater), and the primary objective is to demonstrate the technologies required for landing the probe at a desired location on the Moon and to qualify some of the technologies related to future soft landing missions.
Saturn's moon Prometheus collides with the F Ring. Credit: NASA/JPL/Space Science Institute
This is absolutely astounding! The Cassini spacecraft captured a collision between Saturn’s moon Prometheus and the F ring, which creates a “streamer;” material being pulled from the ring by the moon’s gravity, leaving behind a dark channel. There’s even a movie of the event! The creation of these streamers and channels occurs in a cycle that repeats during each of Prometheus’ orbits. During its 14.7 hour orbit of Saturn, when Prometheus reaches apoapse, or where it is farthest away from Saturn and closest to the F ring, the oblong moon draws a streamer of material from the ring. But since Prometheus orbits faster than the material in the ring, this new streamer is pulled from a different location in the ring about 3.2 degrees (in longitude) ahead of the previous one. In this way, a whole series of streamer-channels is created along the F ring, and Cassini has captured more images showing what are called streamer-channels.
New images, as the one below, again look at the streamer-channels. This image looks toward the unilluminated side of the rings from about 36 degrees above the ringplane. The image was taken in visible light with the Cassini spacecraft narrow-angle camera on September 30, 2008. The view was acquired at a distance of approximately 970,000 kilometers (602,000 miles) from Saturn and at a Sun-ring-spacecraft, or phase, angle of 45 degrees. Image scale is 5 kilometers (3 miles) per pixel.
In some observations, 10 to 15 streamer-channels can easily be seen in the F ring at one time (at left). Eventually, a streamer-channel disappears as shearing forces (i.e., Keplerian shear) act to disperse the constituent dust particles.
The movie shows just under half of a complete streamer-channel cycle. The dark frames in the movie represent the period during which Prometheus and the F ring pass through Saturn’s shadow. The images in the movie were acquired by the Cassini spacecraft narrow-angle camera on November 23 and 24, 2006. The movie sequence consists of 72 clear spectral filter images taken every 10.5 minutes over a period of about 12.5 hours.
Crystals (insets) found in planetary disks. Credit: Caltech
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The Spitzer Space Telescope has, for the first time, detected tiny quartz-like crystals sprinkled in young planetary systems. This surprises astronomers, because these crystals, which are types of silica minerals called cristobalite and tridymite, require flash heating events, such as shock waves, to order to form. So what is going on in these planetary disks to create this type of materials? The findings suggest that shock waves from swirling gas and dust are responsible for creating the stuff of planets throughout the universe. “Spitzer has given us a better idea of how the raw materials of planets are produced very early on,” said William Forrest of the University of Rochester, N.Y “By studying these other star systems, we can learn about the very beginnings of our own planets 4.6 billion years ago.” The big question is, though, with these crystals, can astronomers foretell the future? (Just kidding)
Planets are born out of swirling pancake-like disks of dust and gas that surround young stars. They start out as mere grains of dust swimming around in a disk of gas and dust, before lumping together to form full-fledged planets. During the early stages of planet development, the dust grains crystallize and adhere together, while the disk itself starts to settle and flatten. This occurs in the first millions of years of a star’s life.
When Forrest and his colleagues used Spitzer to examine five young planet-forming disks about 400 light-years away, they detected the signature of silica crystals. Silica is made of only silicon and oxygen and is the main ingredient in glass. When melted and crystallized, it can make the large hexagonal quartz crystals often sold as mystical tokens. When heated to even higher temperatures, it can also form small crystals like those commonly found around volcanoes.
It is this high-temperature form of silica crystals, specifically cristobalite and tridymite, that Forrest’s team found in planet-forming disks around other stars for the first time. “Cristobalite and tridymite are essentially high-temperature forms of quartz,” said Sargent. “If you heat quartz crystals, you’ll get these compounds.”
In fact, the crystals require temperatures as high as 1,220 Kelvin (about 1,740 degrees Fahrenheit) to form. But young planet-forming disks are only about 100 to 1,000 Kelvin (about minus 280 degrees Fahrenheit to 1,340 Fahrenheit) — too cold to make the crystals. Because the crystals require heating followed by rapid cooling to form, astronomers theorized that shock waves could be the cause.
Shock waves, or supersonic waves of pressure, are thought to be created in planet-forming disks when clouds of gas swirling around at high speeds collide. Some theorists think that shock waves might also accompany the formation of giant planets.
So maybe astronomers will be able to predict the type of planets in this newly forming solar system!
The findings are in agreement with local evidence from our own solar system. Spherical pebbles, called chondrules, found in ancient meteorites that fell to Earth are also thought to have been crystallized by shock waves in our solar system’s young planet-forming disk. In addition, NASA’s Stardust mission found tridymite minerals in comet Wild 2.
Forrest and University of Rochester graduate student Ben Sargent led the research, which will be published in the Astrophysical Journal.
Submillimeter astronomy used to be known as the last unexplored wavelength frontier. But this new image from the Atacama Pathfinder Experiment (APEX) telescope reveals the awesome power of submillimetre-wavelength astronomy, and shows another new frontier: a birthplace of new stars. An expanding bubble of ionized gas about ten light-years across is causing the surrounding material to collapse into dense clumps, creating new stars. Submillimetre light is the key to revealing some of the coldest material in the Universe, such as these cold, dense clouds.
The region, called RCW120, is about 4,200 light years from Earth, towards the constellation of Scorpius. A hot, massive star in its centre is emitting huge amounts of ultraviolet radiation, which ionizes the surrounding gas, stripping the electrons from hydrogen atoms and producing the characteristic red glow of so-called H-alpha emission.
As this ionized region expands into space, the associated shock wave sweeps up a layer of the surrounding cold interstellar gas and cosmic dust. This layer becomes unstable and collapses under its own gravity into dense clumps, forming cold, dense clouds of hydrogen where new stars are born. However, as the clouds are still very cold, with temperatures of around -250? Celsius, their faint heat glow can only be seen at submillimetre wavelengths. Submillimetre light is therefore vital in studying the earliest stages of the birth and life of stars.
The submillimeter waveband between the far-infrared and microwave wavebands.
The submillimetre-wavelength data were taken with the LABOCA camera on the 12-m Atacama Pathfinder Experiment (APEX) telescope, located on the 5000 m high plateau of Chajnantor in the Chilean Atacama desert. With LABOCA’s high sensitivity, astronomers were able to detect clumps of cold gas four times fainter than previously possible. Since the brightness of the clumps is a measure of their mass, this also means that astronomers can now study the formation of less massive stars than they could before.
The next generation of submillimeter telescopes is also being built on the plateau of Chajnantor. ALMA, the Atacama Large Millimeter/submillimeter Array will use over sixty 12-m antennas, linked together over distances of more than 16 km, to form a single, giant telescope. It is slated to be completed in 2012.
The sprawling constellation of Hydra was one of the 48 constellations listed by Ptolemy and endures today to be the largest of the 88 modern constellations adopted by the International Astronomical Union. Spanning an incredible 1303 square degrees of night sky and containing 17 primary stars in the asterism, Hydra contain 75 stars with Bayer/Flamsteed designations. It is bordered by the constellations of Antlia, Cancer, Canis Minor, Centaurus, Corvus, Crater, Leo, Libra, Lupus, Monoceros, Puppis, Pyxis, Sextans and Virgo. Position south of the ecliptic plane, Hydra is visible to all observers at latitudes between +54° and ?83° and is best seen at culmination during the month of April.
In mythology, Hydra represents the Snake – not much of a stretch of the imagination given all the twists, turns and distance this constellation takes across the sky. According to legend, Apollo sent the Raven, Corvus, off with the Cup (Crater) to fetch a drink. When the Raven spent his time waiting for a fig to ripen instead of returning with Apollo’s refreshment, he realized he’d made a mistake and grabbed a water snake to offer to the sky god as atonement for his tardiness. Infuriated, Apollo tossed the whole lot of them into the sky where they remain until this day… Some legends also refer to Hydra as one of the many labors of Hercules, too!
Shall we begin with a binocular tour of Hydra? Then let’s start first with the small asterism of stars which marks the “head” of Hydra located between bright stars Regulus and Procyon. When you’ve picked out this distorted circlet, focus your attention on the northernmost of these stars – Epsilon – the backward “3” on our map. While to binoculars it might seem rather ordinary, Epsilon is actually a fantastic multiple star system with at least five members! The primary is a yellow-white giant star with a white subgiant star orbiting so close that it is considered a spectroscopic binary star. A bit further away is another binary pair, the G and F star… and further away yet is a class M dwarf star. Be sure to take out your telescope and have a look….
Now move southeast for the brightest star in Hydra – Alpha – the “a” symbol on our map. Its name is Alphard and it is located about 175 light years away from Earth. Shining in a very soft orange color, this giant star reaches temperatures of about 4000 degrees Kelvin and if at home in our solar system would be about 400 times brighter than our Sun. What makes Alphard unique? Its barium content. At one time Alphard, too, was a binary star, but its massive companion is long gone. Alphard happily collected its by-products of nuclear fusion and left us with evidence of what once was!
Keep your binoculars handy and use the two points of reference you’ve just learned to find our next target – Messier 48. By connecting Epsilon and Alpha as the base of an imaginary triangle with the top pointed southwest, aim your binoculars at the apex and behold one very nice – and very bright – open star cluster. Discovered by Charles Messier in 1771 and also cataloged as NGC 2548, you might even be able to distinguish this stellar field as a hazy spot unaided from a dark sky location. With an estimated age of about 300 million years, you’ll see a very large group of about 50 stars which can resolve into as many as 80 members in larger telescopes. When you see M48, you can thank Caroline Herschel for fixing Messier’s position mistake on this one!
Hop along to Lambda Hydrae – the upside down “Y” on our map. Lambda is a visual double star in binoculars, but it is also a true spectroscopic binary star as well. As you continue south, then east and pass by Xi (the squiggle), keep in mind Xi is unique, too. Xi is an evolved giant star with solar-like oscillations… the very first time science has proved the existence of vibrations in a giant star 10 times the size of our Sun! If you place Xi to the western edge of the field in binoculars, you’ll also see 5th magnitude Beta Hydrae, too. Seeing two there instead of one? You should. Beta is a visual double star and the pair are only separated by about half a magnitude.
Now head northeast towards Gamma, but stop by Messier 68 along the way. This class X globular cluster was discovered by Charles Messier on April 9, 1780, but was resolved into stars by Sir William Herschel who said; “A beautiful cluster of stars, extremely rich, and so compressed that most of the stars are blended together; it is near 3′ broad and about 4′ long, but chiefly round, and there are very few scattered stars about.” M68 will look like a small, round fuzzy in binoculars, but larger telescopes will resolve this 33,000 light-year distant Milky Way resident out!
Are you ready for Gamma Hydrae? It’s the “Y” shape on our map. If you got lost, just use the lower two stars of Corvus to point east towards it. Gamma is located about 132 light years away from our solar system and shines approximately 105 times brighter than Sol. In the not-to-distant past, Gamma decided to shut down its hydrogen fusion factory, which means it may possess a dead helium core. What’s in Gamma’s future? Chances are it will grow larger and less luminous as the core shrinks – then it will fire up to fuse carbon and oxygen. When it does it will become six times brighter and five times bigger! If you’re looking with a telescope and see another star there, you’re right… but it’s an optical companion.
To the east of Gamma is R Hydrae. Now here is one classy variable star! Located about 2000 years away from Earth, R Hydrae’s changes take a period of 389 days to happen, but they happen in a big way. The magnitude of this crazy star jumps from a very dim and telescopic only 11.0 to an easy unaided eye 3.2! R is the third Mira-type variable discovered and may have been noted as early as 1662 by Johannes Hevelius. R Hydra is also special because it has a “declining period” – it has changed its times by 100 days in the last couple of hundred years. So what’s happening? A helium shell is building up around the exterior – just waiting for the day to reach a critical mass and ignite, creating more carbon and oxygen. This is called a “helium shell flash” and it signals the end of life for the giant star. Eventually the layers will just expand into space and the carbon-oxygen core will shine as a white dwarf star. Look around while you’re there… Because you just might spot a companion!
Now drop almost due south for Messier 83 (RA 13:37.0 Dec -29:52). In binoculars this superb spiral galaxy will appear as a soft round glow, but telescopes will reveal wonderful spiral galaxy structure (dependent on observer latitude). With a classification somewhere between a normal and barred spiral galaxy, large telescopes can expect to at least see three traces of spiral arm structure. For astrophotographers, you’ll find terrific star forming regions will appear and dark dust lanes follow the spiral structure throughout the disk.
Ready to do a telescope object in Hydra? Then look no further than NGC 3242 (RA 10:24.8 Dec -18:38). This 8th magnitude planetary nebula is best known as the “Ghost of Jupiter” for its magnificent size! Be sure to look for a double halo structure and the 11th magnitude central star. Even small telescopes will catch a faint blue color to this superb object!
For larger telescopes, let’s try some galaxies. First off, NGC 3621 (RA 11:18.3 Dec -32:49) located about about 3 degrees west/southwest of Xi. You’ll find this fairly larger and bright spiral galaxy sitting inside a box of faint stars! Need a pair of galaxies? Then try NGC 3923 and NGC 3904 (RA 11 h 51 min Dec – 28 48′). Use low magnification and a wide field eyepiece to capture this spiral and elliptical galaxy in the same view.
There’s plenty more deep sky in the constellation of Hydra to be explored, so be sure to get a good star chart and charm the “Snake”!
If you’ve got a clear view of the skies, and happen ti live in the southern hemisphere, there’s a relatively obscure constellation you should probably check out. It’s known as Horologium, a region of the sky that is named after an important historic personality, one who is largely responsible for how we measure time.
The constellation of Horologium was one of 14 created by Nicolas Louis de Lacaille to chart southern hemisphere skies. Originally named “Horologium Oscillitorium” to honor Christiaan Huygens – the inventor of the pendulum clock – it was later shortened to its present named when adopted as one of the 88 modern constellations by the IAU.
Horologium spans 249 square degrees of sky and consists of 6 mains stars in the asterism, with 10 Bayer/Flamsteed designated stars. It is bordered by the constellations of Eridanus, Hydrus, Reticulum, Dorado and Caelum. Horologium is visible to all observers at latitudes between +30° and ?90° and is best seen at culmination during the month of December.
The constellation Horologium, as seen by the naked eye in the southern hemisphere. Credit: AlltheSky.com
Horologium was named to honor Christiaan Huygens, the Dutch mathematician, astronomer and physicist. While traveling in the southern hemisphere and charting the heavens, Nicholas de Lacaille (who loved all things science) found this dim constellation reminded him of Huygen’s newly invented pendulum clock.
Huygens clock incorporated the first harmonic oscillator – increasing the accuracy to within 15 seconds per day. His “horological innovation” so impressed Lacaille that he found the pattern for this invention in the stars.
Horologium is bordered by five different constellations: Eridanus (the Po River), Caelum (the chisel), Reticulum (the reticle), Dorado (the dolphinfish/swordfish), and Hydrus (the male water snake).
Spring driven pendulum clock, designed by Christiaan Huygens (1657) and copy of the Horologium Oscillatorium, Museum Boerhaave, Leiden. Credit: Flickr/Rob Koopman
The official constellation boundaries are defined by a twenty-two sided polygon. Covering a total of 249 square degrees, Horologium ranks 58th in area out of the 88 modern constellations.
With almost no bright stars to claim, stargazing at Horologium can be a bit tricky. But with binoculars, a telescope, and a chart, there are plenty of opportunities for some picturesque views. Let’s start by taking a look in binoculars with Alpha Horologii – the “a” symbol on our map.
Located about 193 light years from Earth, this very normal K1 orange giant star – quietly fusing its core helium into carbon and oxygen. Nearby is Delta, the “8” symbol. It, too is rather ordinary. Delta is a spectroscopic binary star, located about 175 light years away.
So, with very little in the constellation in the way of stars, what is there to do with a telescope? First of all, there’s NGC 1261 (RA: 03:12:15.3; Dec: -55:13:01). This 8th magnitude globular cluster is very well condensed and is at home in a very picturesque field. Small wonder it made the Caldwell list at number 87. Look for a very bright core region and well resolved chains of stars at the edges of this pretty star cluster.
Globular Cluster NGC 1261 as observed from the New Technology Telescope at La Silla, Chile. Credit: ESO
For larger telescopes, try NGC 1512 (RA 4:03.9 Dec -43:21). At slightly brighter than magnitude 11, this barred spiral galaxy belongs to the Dorado group and is located about 30 million light years away. While you won’t find much details here, NASA’s Galaxy Evolution Explorer show spiral galaxy NGC 1512 sitting slightly northwest of elliptical galaxy NGC 1510.
The two galaxies are currently separated by a mere 68,000 light-years, leading many astronomers to suspect that a close encounter is currently in progress. The overlapping of two tightly wound spiral arm segments makes up the light blue inner ring of NGC 1512. Meanwhile, the galaxy’s outer spiral arm is being distorted by strong gravitational interactions with NGC 1510.
Another challenge? Then try NGC 1433 (RA 3:42.0 Dec -47:13). This magnitude 10 galaxy is an example of a ringed barred spiral. While physically you may only notice a bright nucleus and the soft bar, the stars orbiting the disk of this galaxy shows its internal motions photographically. A small elliptical ring can develop near the nucleus – blue proof of star formation. Always keep a watch, because this galaxy had a supernova event in 1985.
Capturing the world's attention: Phoenix (NASA/UA)
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The Phoenix Mars Lander has not communicated since Nov. 2, and engineers from the mission assume the vehicle is now completely out of power. Therefore, at a news conference today, mission managers announced the Phoenix the mission is now officially over. “At this time we’re pretty convinced the vehicle is no longer available for us to use, and we’re declaring the end of the mission,” said Barry Goldstein, Phoenix project manager. “We’ve been surprised by this vehicle before, and we’re still listening. We’ll try to hail Phoenix, but no one has the expectation we’ll hear from it again. We’re completely proud of what we’ve accomplished. We’ve achieved all of the science goals and then some.”
But there’s still more to come from Phoenix, as scientists can now focus fully on analyzing the science data returned by the lander. Could Phoenix have found possible organic substances on Mars?
Peter Smith, Principal Investigator for Phoenix, didn’t rule out the possibility. “We haven’t analyzed the data at that level yet,” he said. “These are subtle signatures. We have the data sets that could reveal that. But until we actually do the work, we can’t say we didn’t find it…I’m still holding out hope here. Its’ really a question of what is the truth on Mars, and we’re trying to make sure we get the right answer here and not come rushing out with a quick analysis. This is very tricky stuff and the data sets are quite complex in regards to organics.”
Tests done by Phoenix didn’t reveal the acid soils Smith and his team were expecting to find, but alkaline salts and perchlorates, which are possible energy sources and nutrients for microbes. Smith doesn’t think there’s anything alive on Mars now, its just too cold. “It’s possible that in a warmer and wetter period on it Mars, it could have been habitable,” he said.
As anticipated, the seasonal decline in sunshine at the arctic landing site is not providing enough sunlight for the solar arrays to collect the power necessary to charge batteries that operate the lander’s instruments. And a dust storm at the landing site made the sunlight decrease even further, ending the mission a little sooner than the team had hoped.
As for any possibility of re-contacting the lander next year when spring returns to Mars’ northern arctic, Goldstein didn’t rule it out, but said its not very likely. “By the mid October (2009) time frame, there would be enough sunlight hitting the solar arrays to create power,” he said. “But its highly unlikely the vehicle will come back. It will be encased in CO2 ice, in temperatures under -150 C. The solar arrays will likely crack and fall off the vehicle,… the electronics will become brittle and break, so the wiring boards won’t work. But this vehicle has behaved so superlatively, we’ll look again in October.”
Look for an official epitaph for Phoenix from Universe Today soon.
The constellation of Hercules belongs to one of the 48 originals plotted by Ptolemy and has survived time to become one of the 88 modern constellations adopted by the International Astronomical Union. Spanning an impressing 1225 square degrees of sky and containing 22 stars in the asterism, it has 106 Bayer/Flamsteed designated stellar designations. Hercules is bordered by the constellations of Draco, Bootes, Corona Borealis, Serpens Caput, Ophiuchus, Aquila, Sagitta, Vulpecula and Lyra. It is visible to all observers at latitudes between +90° and ?50° and is best seen at culmination during the month of July. There is one annual meteor shower associated with Hercules, the Tau Herculids, which peak on or near June 3. The radiant, or point of origin, is near the Hercules/Corona Borealis border and the meteor shower itself last about a month beginning around two weeks before and lasting about two weeks after the peak date. Most of these meteors are quite faint and at maximum, expect to see no more than 15 per hour average.
The mythology surrounding Hercules is a long and very colorful one. He was considered the greatest of all heroes – both Greek and Roman. The legendary strong man was supposed to be the son of Zeus; immortal, yet forever challenged by Hera by his circumstance of birth. His tasks were many: killing a lion with a hide that could not be punctured, destroying the many headed Hydra, cleaning out nasty stables, fighting birds with knife-like feathers, capturing a bull that breathed fire, taming horses that ate flesh, stealing cattle from monsters, stealing golden apples, fighting dragons, snatching a three-headed dog, loosing the love of his life, accidentally killing his teacher and so much more… It is no wonder that Hercules is so often depicted as kneeling in the sky! Even an immortal would be tired from so much… But at last, Hercules earned his place in the stars and he remains there to this day… The fifth largest constellation in the night sky.
Because the constellation of Hercules has no particularly bright stars, it is sometimes difficult to navigate through with binoculars until you learn a few “key” ingredients. There is a large asterism which is fairly easy to recognize that forms a lopsided box, referred to as the “keystone”. The northeast corner is Pi. The northwest corner is Eta. The southeast corner is Epsilon. The southwest corner is Zeta. Always remember when you look at a star chart that north and south are up and down… But east is to the left and west is to the right! To find the “keystone”, let bright Vega guide you…. just start by looking southwest.
Have you found Pi Herculis, yet? If you’re seeing two stars in your binoculars and you’re not sure which one, Pi is the slightly redder and slightly brighter of the pair. Situated about 370 light years from Earth, Pi Herculis is a cool, red supergiant star that was born about 140 million years ago. Although you can’t see it, Pi also has an orbiting substellar companion about 27 times larger than Jupiter there, too! Now, drop south for Epsilon – another binary star. Chances are good this pair of twin stars are almost identical to each other – about twice the size and mass of our Sun – and orbit each other so closely they nearly touch.
Don’t stop moving south. Our next stop is Gamma Herculis, the “8” shape on our map. Gamma is also a very cool star – one with a dead helium core that’s waiting to become a red giant. In maybe 8 million or so years, it will begin to fuse helium into carbon and become much brighter than it is tonight. If you see a faint companion star, it is only an optical one in binoculars – but Gamma is also a genuine binary star.
Next stop? Further south for Alpha – the “a” shape on our map. Now here is a great star! Named Rasalgethi and located about 380 light years away, here we have one of the finest double stars in the night sky. The primary star is a magnificent red class M supergiant that’s over 475 more luminous than our Sun and whose size would fill up our solar system clear out to the orbit of the asteroid belt. But that’s not all… Aim a telescope at Rasalgethi and you’ll see it has a fifth magnitude companion five seconds of arc away. It is also a binary star – an F2 giant with a close orbiting dwarf star companion. Surrounding this whole system is an envelope of gas expelled from the primary star’s incredible solar winds… Enjoy the unusual red and green hues of this colorful double star! And keep watching… Because Rasalgethi is also an irregular variable star – whose brightness changes from magnitude 2.7 to 4.0 within a period of about three months.
Next up? Return to the “keystone” and the northwest corner for Eta – the “n” shape on our map. Shining away about 50 times brighter than our own Sun at a distance of 112 light years, there is nothing particularly impressive about Eta, except where it leads. Begin moving your optics slowly south towards Zeta and you will encounter the “Great Hercules Cluster” – M13! Easily seen in binoculars, sometimes visible to the unaided eye in a dark sky location and absolutely magnificent in any telescope, Messier 13 is perhaps the most famous of all northern globular clusters. Located about 25,000 light years away and home to more than half a million stars, this 12 billion year old system spans no more than 100 light years across. Also known as NGC 6205, this impressive ball of stars was first discovered by Edmund Halley in 1714 and catalogued by Charles Messier on June 1, 1764. If you aren’t impressed, then take the words of Kurt Vonnegut to heart: “”Every passing hour brings the Solar System forty-three thousand miles closer to Globular Cluster M13 in Hercules — and still there are some misfits who insist that there is no such thing as progress.”
Ready for more? Then take another look at Eta and Pi and form an imaginary triangle on the sky using these two stars as the base. The apex is very near where you will find another amazing globular cluster for binoculars or small telescopes – Messier 92. First discovered by Johann Elert Bode in 1777 and independently rediscovered by Charles Messier on March 18, 1781, M92 is a 16 billion year old beauty – formed back at the Milky Way Galaxy’s beginnings. Hiding in there are 16 variable stars and one rare eclipsing binary. What a treat to have two such bright objects so near to one another!
Ready for an alternative binocular tour of Hercules? Then let’s use what you’ve learned. Start by locating magnificent M13 and move 3 degrees northwest – about a binocular field. What you will find is a splendid loose open cluster of stars known as Dolidze/Dzimselejsvili (DoDz) 5 – and it looks much like a miniature of the constellation Hercules. Just slightly more than 4 degrees to its east and just about a degree south of Eta Herculis is DoDz 6, which contains a perfect diamond pattern and an asterism of brighter stars resembling the constellation of Sagitta. Now we’re going to move across the constellation of Hercules towards Lyra. East of the “keystone” is a tight configuration of three stars – Omicron, Nu, and Xi. About the same distance separating these stars northeast you will find DoDz 9. You’ll see a pretty open cluster of around two dozen mixed magnitude stars. Now look again at the “keystone” and identify Lambda and Delta to the south. About midway between them and slightly southeast you will discover the stellar field of DoDz 8. This last is easy – all you need to do is return to Alpha. Move about 1 degree northwest (Rasalgethi will stay in the field) to discover the star-studded open cluster DoDz 7. These great open clusters are very much off the beaten path and will add a new dimension to binocular and fast-telescope observing!
Would you like a challenge? Then go back to M13 with a large telescope and take a look about 40 arc minutes to the northeast for NGC 6207 (RA 16:43.1 Dec +36:50). At near magnitude 12, this small spiral galaxy isn’t for everyone, but it’s always a smile a bonus when you’re in the area, despite the lack of details. Try NGC 6210 (RA 16:44.5 Dec +23:49), too. This bright planetary nebula is suited for all telescopes and takes magnification very well. Look for a blue/green color in larger telescopes, and adding a nebula filter can sometimes reveal some subtle details of a shell around this one. But be sure to take the filter out if you want to catch the central star!
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