King of the planets Jupiter is never a difficult object to find in the night sky thanks to its dazzling brilliance but when opposition comes around, it is at its most spectacular. Roughly every 13 months, the Sun, Earth and Jupiter are in alignment and the giant gas planet is visible all night as it rises in the east at sunset and sets in the west at sunrise.
This year's opposition occurs on the 29th October 2011. Jupiter will shine at magnitude -2.9 with the planets disk spanning a whopping 50 arc seconds in apparent diameter. Currently located in the constellation of Aries, 12 degrees north of the celestial equator, it is an especially good apparition for Northern Hemisphere observers as Jupiter soars high in the night sky.
Only one month since the 5.9 tonne UARS (Upper Atmosphere Research Satellite) crashed harmlessly into the Pacific Ocean another large satellite is about to hit the Earth. This time the satellite is the decommissioned German space observatory named Roentgensatellit or ROSAT. It was launched on the 1st June 1990 on a Delta II rocket from Cape Canaveral to study X-ray astrophysics, and was designed to operate for 18 months. In the end ROSAT far exceeded its original planning and actually operated for over 8 years, finally shutting down on the 12th February 1999.
Like UARS, ROSAT will re-enter the Earth's atmosphere and hit either the surface or land in one of the oceans. It is predicted that this will happen sometime between the 21st and the 23rd October 2011. As was the case with UARS, ROSAT has no propulsion system on board so there's no way to control where and when it falls. Since it is currently moving around the Earth in a nearly circular orbit (altitude about 236 kilometres or 145 miles) at an inclination of 53 degrees, virtually all inhabited areas of Earth are potentially at some risk of collision.
There are two annual meteor showers associated with Halley's Comet, easily the most famous of all comets. The first is the Eta Aquariids shower which occurs in May and the second and more prolific is the Orionids.
The Orionids or Orionid meteor shower takes place every year in late October and usually lasts for about a week although occasionally longer. Sometimes, Orionid meteors may peak at rates of up to 70 per hour but normally the shower is not so active. This year's peak is predicted to be a respectable 25 meteors an hour on the night of the 21st October 2011. Also, at this time the Moon is past 3rd quarter and therefore won't significantly interfere.
The radiant of the Orionids is located in the NE part of the constellation Orion, not far from the Gemini border. Since Orion straddles the celestial equator, the Orionids are one of the few annual showers that are good for both northern and southern hemisphere observers.
When observing meteors showers it is best to wrap up warm (especially in winter), sit comfortably, preferably in a deck chair and look in the general region of the sky around the radiant. It is best not to look directly at the radiant itself as meteors can appear many degrees from it. For the Orionids, all meteor trails will trace back to the shower's radiant in the diagram shown below.
Looking deep into the Milky Way, NASA has released the clearest view yet of the mysterious heart of our galaxy. The new image is a mosaic of infrared shots taken by the Hubble Space Telescope which reveals previously undiscovered massive stars mixed in with complicated structures of super-hot ionized hydrogen gas.
This close up view of our galactic centre is not possible in visible light due to masses of dust and gas clouds blocking our view. However, infrared light can cut through these obstacles and NASA has used Hubble's Near Infrared Camera and Multi-Object Spectrometer to capture this sensational new image.
The famous variable star Mira (Omicron Ceti) has just peaked at the end of September 2011 and for the next few months will be easily visible as an "extra naked eye" star in the Constellation of Cetus.
This years peak occurred around the 24th September 2011 when Mira reached about magnitude 2.4 and for the next few months it will gradually decrease in brightness until hitting minimum about half a year later. The minimum magnitude is usually of the order of 9 so observers will require at least a good pair of binoculars and dark skies to spot it.
It is fascinating to follow a star through such an extreme brightness range, from brilliant naked-eye visibility to the edge of binocular visibility in only a matter of a few months. So don’t miss Mira this year as it is well placed for observation.
Although not yet complete, the world's most sensitive astronomical radio telescope ALMA (Atacama Large Millimeter/sub-millimeter Array) took a remarkable first photograph. The image released by the National Radio Astronomy Observatory (NRAO) to celebrate the launch of the new facility shows in sensational detail the violet collision between two galaxies.
The image is of NGC 4038 and 4039, two faint 11th magnitude galaxies also known as the Antennae Galaxies, in the constellation of Corvus. They are a pair of distorted spiral galaxies between 45 and 65 million light-years distant. It is predicted that within the next 400 million years the nuclei of the two galaxies will join together to become a single core. Eventually, observations and computer modeling suggest that the Antennae Galaxies will settle into one giant elliptical galaxy.
While visible light shows us the stars in the galaxies, ALMA's view reveals something that cannot be seen in visible light: the clouds of dense cold gas from which new stars form. This is the best submillimeter-wavelength image ever made of the Antennae Galaxies.
The Draconids meteor shower takes place every year between the 6th and 10th of October with this year's peak occurring on the night of the 8th October. Normally the maximum ZHR (Zenithal Hourly Rates) for the Draconids is feeble with only 1 to 2 meteors, but the shower does have a history of spectacular outbursts and this year it is worth looking outside as there could well be another.
The dust and debris left behind from periodic comet 21P/Giacobini-Zinner as it orbits the Sun are the source powering the Draconids meteor shower and in reference to the parent comet the meteor shower has also been unofficially known as the Giacobinids.
With an orbital period of 6.6 years, Comet Giacobini-Zinner was discovered on the 20th December 1900 in Nice by French astronomer Michel Giacobini. The comet was subsequently lost and then re-discovered two orbits later on the 23rd October 1913 by German astronomer Ernst Zinner at the Remeis Observatory in Bamberg, Bavaria.
During apparitions, Giacobini–Zinner can reach 8th magnitude in brightness although it is known to flair, for example in 1946, when the comet brightened significantly to attain 5th magnitude and naked-eye brightness.
After analysis of recent data from the NEOWISE (Near-Earth Object WISE) space mission NASA announced that we are unlikely to be wiped out by a killer asteroid in the next few centuries. The new data suggests that there are fewer large near-Earth asteroids orbiting the Sun than previously thought but we are not completely out of the woods yet!
The new data reveals only a small decline from 1,000 to 981 in the estimated number of large near-Earth asteroids, which are at least 1 kilometre (0.62 miles) across. Asteroids of this type are of particular interest as they are about the size of a small mountain and if one were to strike the Earth the consequences would result in mass species extinction and large climate and atmospheric changes. For comparison it is thought that an asteroid approximately 10 kilometres (6 miles) across wiped out the dinosaurs. Importantly, of these 981 asteroids NASA has already found nearly 93% of them. This in total amounts to 911 asteroids and none of them pose a threat to the Earth in the foreseeable future.
Like all bodies in the solar system the planets are continually moving as they orbit the Sun. When viewed from Earth an ever changing scene results as they dance on their merrily way against the backdrop of the fixed stars. Quite often two planets will appear very close together in the night sky, a planet will pass in front of a distant star or one will briefly obscure the light of a beautiful open cluster. These conjunctions and occultations can be spectacular events, rewarding for visual observers and excellent opportunities for imagers to capture a stunning photo.
One such event will take place from the 30th September until the 3rd October 2011. During this time the red planet Mars will move almost exactly through the middle of M44 the famous Beehive or Praesepe open cluster.
M44 is a large and bright showstopper open cluster. At apparent magnitude 3.4 it is easily visible to the naked eye as a nebulous patch, particularly when viewed from a dark site. Since the Beehive is a large cluster covering over 1½ degrees of sky, three times the diameter of the full moon, it is best observed with binoculars or a wide field telescope. Binoculars reveal tens of mainly white stars with a noticeable grouping in the shape of a "V" just off center. It is also a great sight in a 100mm (4-inch) telescope at 35x magnification. Here the cluster nearly fills the complete field of view with at least 50 bluish coloured stars brighter than 9th magnitude visible. The majesty of the Beehive is lost a little in larger scopes as they struggle to contain its large size but is anyway still a nice sight.
Comet hunters have not had it great over the last few years with just a couple of moderate performers mixed in with many faint examples but no real showstoppers since 2007. That was the year when the daytime comet C/2006 P1 McNaught briefly burst onto the scene, reaching an astonishing magnitude of -5. Later that year periodic comet 17P/Holmes brightened substantially and was easily visible to the naked eye as a 3rd magnitude fuzzy star in Perseus, but since then there has been little on offer.
Now two comets have caused a stir for different reasons. Although neither is a showstopper, one showed much potential but faded while the other is almost certain to put on a nice but moderate show.
Elenin Boom and Bust
A lot of early excitement was provided by comet C/2010 X1 Elenin. It was discovered on the 10th December 2010 by Russian amateur astronomer Leonid Elenin and early press speculated than Elenin may put on a good naked eye show around October 2011. At this time it should approach to within 35 million kilometers of Earth but unfortunately the latest observations suggest that the comet will be a complete washout. Elenin faded dramatically after a solar flare on the 20th August and now appears to be disintegrating and unlikely to survive for much longer.
However, all is not lost as there is another comet in the night sky that has until now attracted much less attention than Elenin but will almost certainly produce a fine performance for many months to come. The comet in question is C/2009 P1 Garradd. Gordon Garradd discovered the comet on the 13th August 2009. Like many comet discoveries these days, Garradd was searching for near-Earth objects using the Siding Spring Observatory near Coonabarabran in Australia when he captured the magnitude 17.5 comet. Since then Comet Garradd has brightened steadily and from July 2011 has been a nice target, shining at magnitude 7 and visible in telescopes of all sizes.
As comets go Garradd is unusually large and quite active. Unfortunately, it never gets very close to either the Sun or the Earth. At perihelion on the 23rd December 2011, it is 1.55 AU (230 million kilometers or 144 million miles) from the Sun. Closest approach to Earth is not much better. When this happens on the 5th March, Garradd will still be about 1.27 AU (188 million kilometers or 118 million miles) away.
NASA space officials predict that the decommissioned 5.9 tonne UARS (Upper Atmosphere Research Satellite) will re-enter the Earths atmosphere and plummet towards the surface within a day or two of Friday 23rd September 2011.
Essentially spiralling out of control, NASA has no control over the spacecraft and cannot tell exactly where it will land. They estimate that up to 26 parts of the spacecraft, one weighing 159 kilograms, will survive re-entry and hit either the Earths surface or land in one of the Oceans. However, according to the NASA the chances of a person being hit by a piece of the disintegrating satellite are small, only 1 in 3200.
The drop zone, the area where parts of the satellite could land is anywhere between 57 degrees North and 57 degrees South latitude – basically, most of the populated world. But since three quarters of Earth is covered with ocean, there is a high likelihood that the satellite will re-enter over the sea. If it does land on land, observers on the ground nearby will see a dazzling show of fireworks as UARS burns up in the Earth atmosphere.
Gas giant Uranus, the 7th planet from the Sun reaches opposition on the 26th September 2011 when it will be at its best for the year. Now is a perfect time to observe, perhaps for the first time, this far distant world.
With an apparent magnitude varying between 5.3 and 5.9, Uranus is a naked eye target. However, it is a dim world, with a small apparent size that moves so slowly it was unknown to ancient observers. For naked eye star watchers with dark skies bagging Uranus is a worthy achievement to cross off the list, but for most suburban observers, binoculars or a small telescope is required. But whatever optical instrument you use or don't use, a good star chart is an essential requirement and we have that chart for you.
Uranus was observed by Sir William Herschel on the 13th March 1781 while in the garden of his house at 19 New King Street, Bath using his 7-foot long (2.1m), 6-inch (150 mm) aperture Newtonian telescope. Herschel initially thought the planet was a comet and duly reported his discovery a few weeks later to the Royal Society. While Herschel continued to cautiously describe his new object as a comet, it soon became obvious that the new object was a planet way beyond Saturn. Herschel himself acknowledged the fact and in recognition of his achievement, King George III gave Herschel an annual stipend of £200. Such a bonus did not come without condition and the condition was that Herschel moved to Windsor with his telescopes so that the Royal Family could also look through them!
It's perhaps a little bit surprising that Uranus was not identified as a planet earlier. On many occasions before Herschel's discovery the planet was observed but it was usually mistaken as a star. John Flamsteed observed the planet on at least six times in 1690 and even catalogued it as 34 Tauri, while the French astronomer Pierre Lemonnier observed Uranus at least twelve times between 1750 and 1769 but failed to notice its true nature.
This year's opposition of Uranus takes place on the 26th September 2011 when the planet is located in the constellation of Pisces "the Fishes". At magnitude 5.7, Uranus is a visible to the naked eye under a dark sky and is an easy object for binocular or small telescope observers.
Pisces is a faint but large zodiac constellation with an area of 889 square degrees. It ranks as the 14th largest constellation. Uranus at opposition is located in a relatively sparse section of Pisces devoid of any bright stars but is relatively easy to identify once you have located the correct region of sky.
Although Pisces is faint there is an excellent starting point nearby…the Great Square of Pegasus. First locate the square and then move about 15 degrees due south to locate the circlet shape that forms one of the two historical Pisces fish. None of the stars that form the circlet are brighter than 4th magnitude, but aim for the SE corner star, mag. 4.49 λ Psc. Once there scan about 7 degrees to the east and 2 degrees south to locate Uranus, which is surrounded by a number of other similar brightness stars.
From science fiction to science fact, astronomers using the Kepler planet-hunting space telescope have announced the discovery of a "Tatooine" exoplanet that orbits around not one star but two! We have seen something similar to this before, in the science fiction world. Tatooine is the name of Luke Skywalker's home world in the movie Star Wars. This scorched desert rock orbits two yellow suns and is described by the movie’s hero as "If there's a bright center to the universe, you're on the planet that it's farthest from." A scene from the move depicts Luke Skywalker looking out towards the horizon as the two almost identical yellow stars begin to set.
Now, of course it is common place on Earth to see beautiful and spectacular sunsets that dazzle the eye as day turns into night. Now compare that with a sunset on the newly discovered planet, two stars never very far apart in the sky, one glowing yellow-orange sitting alongside its smaller deep red companion. As nighttime approaches they both gradually descend towards and then sink below the horizon producing a spectacular double sunset for anyone who may be privileged to witness it.
The long-awaited Space Shuttle replacement launch system was unveiled on the 14th September 2011 by US space agency NASA.
Florida senator Bill Nelson, himself a former Space Shuttle astronaut presented details in Washington DC, announcing that the new SLS (Space Launch System) will be "the most powerful rocket in history”. With an initial lifting capability aimed at 70,000 kilograms into LEO (low-Earth orbit) and a final target of 130,000 kilograms, the new launch system will allow NASA to once again launch massive payloads into space. By comparison, today’s most powerful launchers Europe’s Ariane 5 and NASA’s Delta IV Heavy can deliver just over 20,000 kilograms into LEO.
Unlike in the past where NASA has been accused of throwing away good tried technology, the new system builds on existing technology inherited from the Space Shuttle program. The initial design of the SLS calls for a main core section 65 metres tall with solid rocket boosters strapped to each side. Attached to the main section are five Shuttle orbiter’s engines. NASA states that the solid rocket boosters will also be taken from the Shuttle program, although later upgraded possibly to a liquid fuelled based system. Much of the external tank design would remain the same as the Shuttle's.
By using tried and tested technology, SLS benefits from reduce cost and development time allowing NASA to launch unmanned test flights as early as 2017. A later addition of an upper stage increases the height of the rocket to over 100 metres and allows it to reach its full launch capability. NASA intends its Orion astronaut capsule to sit atop the rocket and hence avoid the problems of falling debris during launch that plagued the Space Shuttle.
Using the High Accuracy Radical velocity Planet Searcher (HARPS) spectrograph instrument at the 3.6m La Silla Observatory on the outskirts of the extremely dry Chilean Atacama desert, European astronomers on Monday 12th September 2011 announced the largest ever discovery of exoplanets at one time.
In total 50 new planets beyond our solar system have been found, including 16 so-called Super-Earths. These types of planets are of special interest as they are larger than our own Earth but not as large as gas giants such as Jupiter, Saturn, Uranus and Neptune. If the right environment exists on a Super-Earth, for example positioned inside its star’s "Goldilocks" zone with appropriate surface, temperature and atmospheric conditions then a potential habitable world may exist.
But what particularly excites the astronomers about the recent discoveries is one of the 16 new Super-Earths, HD 85512 b. Located 36 light years from Earth in the constellation of Vela, HD 85512 b is estimated to have a mass of only about 3.6 times that of the Earth and a temperature of around 25 degrees Celsius. It is close enough to be just inside the "Goldilocks" zone and hence the conditions are just right for the possibility of liquid water to exist on its surface and perhaps life itself.
The manned space shuttle program may recently have ended but unmanned space missions to explore the unknown are well and truly alive. Nasa latest space probe "The Gravity Recovery and Interior Laboratory" (GRAIL) is designed to map tiny variations of the Moon gravitational field and was launched from Cape Canaveral Complex 17B on the 10th September 2011.
Costing US$500 million the aim of GRAIL is to better understand the Moon's internal structure which should help to provide insight into many lunar mysteries. These include questions such as, why does the Moon's far side lack the great maria or "seas" that are prominent on the near side.
The spacecraft actually consists of two small identical probes, named Grail-A and Grail-B, weighing 132 kg. Unlike the Apollo manned missions that took about three days to reach the Moon, GRAIL will use a much longer (via Sun-Earth Lagrange point L1) but fuel-efficient journey requiring nearly four months to reach lunar orbit.
The nearest supernova of its type to be discovered for more than 40 years is expected to reach its maximum brightness around the 8th and 9th of September 2011.
The supernova (named PTF11kly) was discovered by British astronomers on the 24th August 2011 using the famous 48-inch Schmidt telescope at Mount Palomar. Operating the telescope remotely they found a "new" 17th mag. star lying within one of the spiral arms of M101 in Ursa Major. It has now brightened significantly and as of the 8th September the supernova hovers around magnitude 10, which is bright enough to be seen with an 80mm (3.1 inch) telescope under dark skies or even with good binoculars.
Vesta one of the largest asteroids reaches opposition on the 5th August 2011. Located in the constellation of Capricornus, Vesta will attain a maximum visual magnitude of 5.6, hence naked eye visibility for keen eyed observers from a dark site.
For surburbian observers and those who are not so lucky to have particularly dark skies, Vesta is still an easy binocular / small telescope object. So if you have never seen an asteroid before, now is an excellent time to do so.
Vesta was the fourth asteroid to be discovered on the 29th March 1807 by the German astronomer Heinrich Wilhelm Olbers. Along with the other asteroids known at the time (Ceres, Pallas and Juno), Vesta was initially classified as a planet in its own right and subsequently was given its own planetary symbol. With further discoveries, all in the region between Mars and Jupiter, the general term asteroids was coined to describe them. Much later in 2006, the International Astronomical Union (IAU) defined a new classification of dwarf planet of which the largest asteroid Ceres is now a member.
Despite being only the third largest body in the main asteroid belt with a diameter of 530km (330 miles), Vesta is the brightest asteroid. It appears even brighter than the much larger dwarf planet Ceres and asteroid Pallas, which is slightly larger. This is because its approaches closer to the Earth than the other two and additionally has a much higher reflective surface. At favourable oppositions, the maximum visual magnitude of Vesta is 5.1 and therefore easily within naked eye visibility, especially from a dark site.
For opposition this year, Vesta will peak at mag 5.6.
The second faintest constellation of the zodiac Capricornus provides the backdrop for this opposition. Capricornus is located at a declination of about -20 south and therefore never rises particular high in the sky for Northern hemisphere observers. Hence the best views of Vesta are seen from the Southern hemisphere, however for all observers the opportunity exists for a short time, to glimpse with the naked eye the only asteroid that is bright enough to do so.
The Southern Cross
Despite having the smallest size of all constellations - a mere 68 square degrees - Crux is the most celebrated of all southern constellations. Its name is Latin for cross, which refers to the main asterism of the four relatively bright stars at its centre. To some the cross shape is more resembling of a kite, but whatever you think it looks like it's superb and unmistakable.
Positioned in the sky at a declination of about -60 degrees, Crux is visible from all parts of the Southern Hemisphere and for many of these observers it's circumpolar. For residents just north of the equator the cross can be spotted during late spring, low down above the southern horizon. Unfortunately, for most Northern Hemisphere observers this superb constellation never manages to climb above the horizon and can never be seen.
1. How are the charts produced?
All charts are computer generated with finishing touches applied using vector graphics program Inkscape. The star data for the charts comes from the Hipparcos and Tycho-2 Catalogues of the Hipparcos satellite, which was launched by the European Space Agency in 1989 and operational until 1993.
The Hipparcos Catalogue is a high-precision data-set of more than 100,000 stars and was published in 1997 along with the lower precision Tycho Catalogue of more than a million stars. An enhanced catalogue Tycho-2 with 2.5 million stars was published in 2000. Double stars were checked using the Washington double star catalogue. Data for deep sky objects such as nebula, galaxies, open clusters, globular clusters etc are checked against various sources.
2. Will the charts always be free?
Absolutely. All charts will be free to download and we will try to make them available in as many different formats as possible.
But it not just error correcting that we are after; we are continuously trying to improve the quality, accuracy, presentation and usefulness of the charts. Any ideas, comments or suggestions that you may have in these areas would also be very welcome.
As always, we are truly grateful for all comments that we receive and hope that you enjoy using the star charts.
Here's to dark stars!
Your freestarcharts.com team.
Our aim is to promote Astronomy for all by providing information, articles, charts for anyone who wants to learn more about the stars, galaxies, the Sun, the planets, moon, asteroids, comets and whatever may be out there.
Jupiter reaches opposition on April 7, 2017
Lyrids meteor shower peaks on the night of April 21/22
This Month's Guide
Algol eclipse dates and times for April 2017
West:- Mars (mag. +1.6), Mercury (mag. -0.2 to +2.4 - first half of month)
East:- Jupiter (mag. -2.5)
South:- Saturn (mag. +0.4)
East:- Venus (mag. -4.2 to -4.7)
East:- Venus, Neptune (mag. +8.0)
Naked eye / binoculars:-
Melotte 111 - Mel 111 - The Coma Star Cluster (Open Cluster)
Messier 44 - M44 - The Praesepe (Open Cluster)
Messier 67 - M67 - Open Cluster
Messier 51 - M51 - The Whirlpool Galaxy (Spiral Galaxy)
Messier 97 - M97 - The Owl Nebula (Planetary Nebula)
Messier 101 - M101 - The Pinwheel Galaxy (Spiral Galaxy)
Messier 65 – M65 – Spiral Galaxy
Messier 66 - M66 - Intermediate Spiral Galaxy
Messier 95 - M95 - Barred Spiral Galaxy
Messier 96 - M96 - Intermediate Spiral Galaxy
NGC 4244 - Spiral Galaxy
NGC 4565 - Needle Galaxy - Spiral Galaxy
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