Image credit: NOAO
Monday, December 27 – No one likes to get up early, but this morning will be worth walking outside for as Mercury and Venus make a very close pairing on the horizon just before dawn. If you’re clouded out? Don’t worry. Both planets will keep their positions for several days!
With the almost full Moon rising not to long after the Sun sets, tonight let’s take the time to study another “double delight” – Gamma Arietis. Also known as Mesarthim, Gamma was one of the very first double stars to be discovered, well… rather accidentally! In 1664, Robert Hook was following a comet and stumbled upon this matched magnitude pair. At approximately 160 light years away, each of these two “white” stars are about three to four times more massive than our own Sun and are seperated by about 400 AU. Locked in an ancient embrace, the pair takes about 3,000 years to orbit each other. Since the time of their discovery, this duo’s relative orientation has remained virtually unchanged, but with the advent of modern measurement show they may have moved fractionally closer within the last 150 years. Does this mean they are drawing together? No. Like so many things we see from such a great distance, it is a matter of perspective and it is believed that we may be looking at their orbital pattern “edge-on”.
In the telescope at high power, Mesarthim is indeed a very close double, one who’s stars are precisely oriented north/south of each other. This one is quite delightful, for such similar magnitudes make them appear like “eyes” in the dark! (And if you are very, very good – you will see a tiny 9th magnitude star to the east. Fine optics and perfect stability will show this star also has a 13th magnitude companion.)
Tuesday, December 28 – Since the Moon won’t begin to rise for a short time after the skies turn dark, this would be a great opportunity to locate an easy Messier object – M34. If you remember previous study stars, Almach and Algol, you’re halfway there. Draw an imaginary line between them and look with your binoculars or finder scope just a shade north of center.
In binoculars, the M34 will show around a dozen fainter stars clustered together and perhaps a dozen more scattered around the field. Small telescopes at low power will appreciate the M34 for its resolvability and the distinctive “orange” star in the center. Larger aperture scopes will need to stay at lowest power to appreciate the 18 light year span of this 100 million year old cluster, but take the time to power up and study. You will find many challenging doubles inside!
Wednesday, December 29 – Is it gone yet? Nope. The Moon will rise a little later this evening, but we’re going to run ahead of it tonight and begin some studies in Auriga! Looking roughly like a pentagon in shape, start by identifying the brightest of these stars – Capella. Due south of it is the second brightest star, El Nath. By aiming binoculars at El Nath, go north about 1/3 the distance between the two and enjoy all the stars!
You will note two very conspicuous clusters of stars in this area, and so did Le Gentil in 1749. Binoculars will reveal the pair in the same field, as will telescopes using lowest power. The dimmest of these is the M38, and will appear vaguely cruciform in shape. At roughly 4200 light years away, larger aperture will be needed to resolve the 100 or so fainter members. About 2 1/2 degrees to the southeast you will see the much brighter M36. More easily resolved in binoculars and small scopes, this “jewel box” galactic cluster is quite young and about 100 light years closer!
There are many other fine things in this area, so scan around! We’ll be back…
Thursday, December 30 – Is it gone yet? No! The Moon will be along shortly, but not before we’ve had an opportunity to head for another northern “gem”, the M76.
Located in western Perseus just slightly less than 1 degree north/northwest of Phi, the M76 is often referred to as “The Little Dumbbell”. Originally discovered by Messier’s assistant Mechain in September of 1780, Charles didn’t get around to cataloging it for another six weeks. What a shame it took him so long to view this fine planetary nebula! Its central star is one of the hottest known, but it is its resemblance to the M27 that makes it so fascinating. Looking very much like a miniaturization of the much larger M27, the M76 is rather faint at magnitude 11, but is quite achievable in scopes of 114mm in aperture or larger. It is small, but its irregular shape makes this planetary nebula a real “class act”!
For our Southern Hemisphere friends, get thee out there and view Eta Carinae! First recorded by Halley in 1677, this nebular variable star left even the great Sir John Herschel at a loss to describe its true beauty and complexities. This “slow nova” is filled with all the wonders the we “northerners” can only dream about…
Friday, December 31 – Is it gone yet? No. The Moon will be around later tonight, but the year 2004 is just about ended. Try celebrating in a unique and inspiring way! Go observing…
In the hours before midnight, you could take a cosmic journey that spans millions of light years. In the northern hemisphere, visit with the Andromeda Galaxy again – or the Small and Large Magellanic Clouds if you live in the south. Feast your eyes on vast and wondrous displays of stars like the “Double Cluster” in Perseus, or the “Jewel Box” – Kappas Crucis star cluster. Rejoice in the birth of new stars by voyaging to the M42 – “Orion Nebula”… And remember the old by returning to the M1 – “Crab Nebula”. Take delight in the movements of our own solar system by hunting down the “Magnificent Comet Macholz”, or peeking in on Saturn’s rings. Perhaps the ISS will make a pass over your area tonight, or only a single star shine through. It may be something as spectacular as watching a meteor go down in a blaze of glory, or as quiet and contemplative as watching the Moon rise.
As we begin a New Year, just take a moment to look up at the stars and think about all the millions of years that they have been in the making and all the time that it has taken for the light to reach us. Salute!
Saturday, January 1 – Is it gone yet? No. The Moon will be on the scene later, but tonight’s goal with be a rather simple one – a star of singular beauty. Located northwest of Mu in the constellation of Lepus, is R Leporis – better known as “Hind’s Crimson Star”.
Discovered in October of 1845 by J.R. Hind, R Leporis will require optical aid to view since it is a variable that moves between approximately magnitude 6 to as low as magnitude 11 in about 432 days. As a carbon star, this particular example is well worth viewing for its intense ruby color. As R Leporis undergoes its changes, it produces amazing amounts of carbon. To understand what makes it dim, think of an oil lamp. As the carbon “soot” collects on the glass, like the star’s outer atmosphere, the light decreases until it is sloughed off and the process is repeated. At a rough distance of approximately 1500 light years, “Hind’s Crimson Star” will become an observing favorite. Enjoy!
Sunday, January 2 – Is it gone yet? No. The Moon will be around much later tonight, but the window of opportunity to view a spectacular comet is once again wide open.
Tonight the “Magnificent Comet Machholz” will be in the same field of view as 6 Tau Tauri. Having long ago achieved unaided eye brightness, C/2004 Q2 Machholz continues to delight observers the world over. The coma is easily seen in binoculars, and the twin ion and dust tails may still be observable on this date. Looking like a huge, unresolvable globular cluster, trying judging its visual magnitude for yourself by using nearby Xi and Omicron as guideposts. Defocus and compare these magnitude 4 stars to the comet’s brightness. Is the comet dimmer? Or about the same? There is no way of predicting exactly how bright comet Machholz will be in advance, but tonight you can make the call!
For very late night, or observers beginning early on the morning of January 3, keep a watch out for the annual Quadrantid meteor shower. Seeming to emanate from the constellation of Bootes, this annual shower can produce up to 60 meteors per minute, but has an unusual and unpredictable peak time. More information on the Quadrantids will be available in next week’s issue.
Until next week fellow SkyWatchers, I wish you all a peaceful and prosperous New Year. Keep looking up… I am! Light speed, ~Tammy Plotner
An unpiloted Russian cargo ship linked up the International Space Station this evening, completing a two-day Christmas journey to deliver 2.5 tons of food, fuel, oxygen, water, supplies and holiday gifts to the crew.
The ISS Progress 16 craft automatically docked to the aft port of the Zvezda Service Module at 5:58 p.m. CST (2358 GMT) as the spaceship and the Station flew 225 statute miles over Central Asia. Within minutes, hooks and latches between the two ships engaged, forming a tight seal between the two vehicles. The docking occurred about 30 minutes later than planned so that the linkup could occur over Russian ground stations with the benefit of television from the cargo ship and real-time data.
As the Progress moved in for its linkup, Expedition 10 Flight Engineer Salizhan Sharipov was at the controls of a manual docking system in Zvezda, ready to take over the Progress? final approach in the unlikely event its automated docking system encountered a problem. But the docking was flawless. Station Commander and NASA Science Officer Leroy Chiao was nearby, taking video and still photos of the Progress arrival.
Launched from the Baikonur Cosmodrome in Kazakhstan on Thursday, the Progress is loaded with 1,234 pounds of propellant, 110 pounds of oxygen and air to help maintain the Station?s atmosphere, 926 pounds of water and more than 2,700 pounds of spare parts, life support system components and experiment hardware. The manifest also includes 69 containers of food, about a 112-day supply.
After an extended sleep period this evening, the crew will be awakened Sunday morning to conduct leak checks at the hatch interface between the Progress and Zvezda. They will open the Progress hatch shortly after noon CST (1800 GMT) Sunday to begin unloading its cargo.
Among the new items that arrived at the Station are laptop computers, new spares for U.S. spacesuits and components for the arrival next year of the European Automated Transfer Vehicle cargo craft.
Information on the crew’s activities aboard the Space Station, future launch dates, as well as Station sighting opportunities from anywhere on the Earth, is available on the Internet at:
http://spaceflight.nasa.gov/
Original Source: NASA News Release
Over the past week, several independent efforts were made to search for pre-discovery observations of 2004 mn4. These efforts proved successful today when Jeff Larsen and Anne Descour of the Spacewatch Observatory near Tucson, Arizona, were able to detect and measure very faint images of asteroid 2004mn4 on archival images dating to 15 March 2004. These observations extended the observed time interval for this asteroid by three months allowing an improvement in its orbit so that an Earth impact on 13 April 2029 can now be ruled out.
As is often the case, the possibility of future Earth impacts for some near-Earth objects cannot be entirely ruled out until the uncertainties associated with their trajectories are reduced as a result of either future position observations, or in this case, heretofore unrecognized, pre-discovery observations. When these additional observations were used to update the orbit of 2004 MN4, the uncertainties associated with this object’s future positions in space were reduced to such an extent that none of the object’s possible trajectories can impact the Earth (or Moon) in 2029.
In the accompanying diagram, the most likely position of asteroid 2004 MN4 is shown at the end of the blue line near the Earth on 13 April 2029. However, since the asteroid’s position in space is not perfectly known at that time, the white dots at right angles to the blue line are possible alternate positions of the asteroid. Neither the nominal position of the asteroid, nor any of its possible alternative positions, touches the Earth, indicating that an Earth impact in 2029 is ruled out.
The passage of the asteroid by the Earth in 2029 alters its subsequent trajectory and expands the asteroid’s position uncertainty region (i.e., the line of white dots increases in extent) so the asteroid’s subsequent motion is less certain than it was prior to the 2029 close Earth approach. However, our current risk analysis for 2004 MN4 indicates that no subsequent Earth encounters in the 21st century are of any concern.
Original Source: NASA News Release
After six fruitful months exploring the interior of “Endurance Crater,” the Opportunity rover has successfully climbed out of the crater onto the surrounding flatland of Meridiani Planum. Once out, the rover examined some of its own tracks that it had laid down prior to entering the crater. It compared them side-by-side with fresh tracks in order to observe any weathering effects in the intervening 200 sols. Opportunity is now making its way toward an engineering examination of its heat shield, which is located about 200 meters (220 yards) from the edge of Endurance. Now that the vehicle is on the relatively flat plain rather than tilted toward the Sun on the north-facing inner slope of the crater, electrical output from its solar array has declined by about 15 percent. Opportunity remains in excellent health as it begins a new phase of exploration.
Sol 312 and 313 were planned in a single planning cycle. Opportunity was still inside Endurance Crater. On sol 312 the plan began with backing up and using the panoramic camera and miniature thermal emission spectrometer to observe a rock target called “Wharenhui,” which had been treated with the rock abrasion tool on earlier sols. Subsequent commands were to turn cross-slope, drive 7 meters (23 feet), turn upslope, and drive an additional 6 meters (20 feet) uphill. Opportunity performed the drive perfectly, ending up approximately 5 meters (16.4 feet) from the rim of Endurance Crater. Opportunity’s tilt went from 25 degrees pre-drive to 19 degrees post-drive.
Sol 313 was a restricted sol because results from the sol 312 drive were not available for planning sol 313. That meant that no driving or robotic-arm activities were permitted. So Opportunity performed about two hours of observations using the panoramic camera and miniature thermal emission spectrometer and then went to sleep in the early afternoon. The rover woke up to support late-afternoon and early-morning communication relays by the orbiting Mars Odyssey.
Sols 314 through 316 were planned in another single planning cycle. The plan was to complete the egress from Endurance Crater on sol 315, so sol 314 was another remote sensing sol. This would be the last full sol inside Endurance. Opportunity spent about two and a half hours observing with the panoramic camera and miniature thermal emission spectrometer. It also performed a nighttime observation with the miniature thermal emission spectrometer just before midnight. To ensure that Opportunity had adequate power, the early-morning communication-relay session with Odyssey was canceled and Opportunity went into a modified deep sleep after completing the late-night observation.
Sol 315 was the big day for Opportunity. The rover was finally going to leave Endurance Crater after spending 181 sols there! Opportunity was instructed to drive 7 meters (23 feet) up and out of the crater. It was a textbook drive. Everything went as planned and Opportunity had finally, successfully completed a long and detailed series of observations inside Endurance. Opportunity ended up on the plains of Meridiani ready to begin the next chapter of its adventures.
Sol 316 was the third sol of a three-sol plan, and because Opportunity had driven on sol 315, sol 316 was restricted to remote-sensing observations. The rover performed about two hours of remote sensing and went to sleep. Out on the plains, Opportunity went from a northerly tilt that is very good for solar exposure, to a southerly tilt that is not so good for solar exposure. The tilt was expected to be as high as 10 degrees, but Opportunity’s actual tilt was about 5 degrees. Daily output from the solar panels went from 840 watt-hours in the crater, to 730 watt-hours on the plains.
Since the team continues to be operating in restricted sol mode, sols 317 and 318 were planned together as a two-sol plan. For sol 317, the science team elected to drive toward wheel tracks that Opportunity had made before entering Endurance Crater. The rover backed up about 5 meters (16.4 feet), performed some mid-drive imaging, and then continued another 10 meters (33 feet) to put the old rover tracks into the work volume of the robotic arm. Sol 318 was another remote-sensing sol, during which Opportunity imaged its still-distant heat shield and conducted a miniature thermal emission spectrometer observation of the tracks.
After the drive, both old and new tracks were directly in front of the rover. On sol 319 Opportunity captured microscopic imager mosaics of both types of tracks, then drove about 40 meters (131 feet) closer to the heat shield, which will be examined carefully in future sols. Sol 319 ended on Dec. 17.
Original Source: NASA News Release
The European Space Agency?s Huygens probe was successfully released by NASA?s Cassini orbiter early this morning and is now on a controlled collision course toward Saturn?s largest and most mysterious moon, Titan, where on 14 January it will make a descent through one of the most intriguing atmospheres in the solar system to an unknown surface.
The separation occurred at 02:00 UTC (03:00 CET): A few minutes after separation, Cassini turned back to Earth and relayed back information about the separation. This signal then took 1 hour and 8 minutes to cross the 1.2 billion kilometres separating the Cassini spacecraft and Earth.
?Today?s release is another successful milestone in the Cassini/Huygens odyssey?, said Dr David Southwood, ESA?s Director of Science Programmes. ?This was an amicable separation after seven years of living together. Our thanks to our partners at NASA for the lift. Each spacecraft will now continue on its own but we expect they?ll keep in touch to complete this amazing mission. Now all our hopes and expectations are focused on getting the first in-situ data from a new world we?ve been dreaming of exploring for decades?.
Final stage of a seven-year odyssey
The Cassini/Huygens mission, jointly developed by NASA, ESA and the Italian space agency (ASI), began on 15 October 1997, when the composite spacecraft were launched from Cape Canaveral, Florida, atop a Titan 4B/Centaur vehicle. Together, the two probes weighed 5548 kg at launch and became the largest space mission ever sent to the outer planets. To gain sufficient velocity to reach Saturn, they had to conduct four gravity-assist manoeuvres by flying twice by Venus, once by the Earth and once by Jupiter. On 1 July Cassini/Huygens eventually became the first spacecraft to enter an orbit around Saturn.
On 17 December, while on its third orbit around the ringed planet, the Cassini orbiter performed a manoeuvre to enter a controlled collision trajectory towards Titan. As planned, a fine tuning of the trajectory took place on 22 December to place Huygens on its nominal entry trajectrory. While Huygens will remain on this trajectory till it plunges into Titan?s atmosphere on 14 January, the orbiter will perform a deflection manoeuvre on 28 December to avoid crashing onto the moon. Today?s separation was achieved by the firing of pyrotechnic devices. Under the action of push-off springs, ramps and rollers, the probe was released at a relative velocity of about 0.3 m/s with a spin rate of 7 rpm. Telemetry data confirming the separation were collected by NASA?s Deep Space Network stations in Madrid, Spain and Goldstone, California, when the telemetry playback signal from Cassini eventually reached the Earth.
The Huygens probe is now dormant and will remain so for its 20-day coast phase to Titan. Four days before its release, a triply-redundant timer was programmed in order to wake-up the probe?s systems shortly before arrival on Titan.
Exploring Titan?s atmosphere
Huygens is scheduled to enter Titan?s atmosphere at about 09:06 UTC (10:06 CET) on 14 January, entering at a relatively steep angle of 65? and a velocity of about 6 km/s. The target is over the southern hemisphere, on the day side. Protected by an ablative thermal shield, the probe will decelerate to 400 m/s within 3 minutes before it deploys a 2.6 m pilot chute at about 160 km. After 2.5 seconds this chute will pull away the probe?s aft cover and the main parachute, 8.3 m in diameter, will deploy to stabilise the probe. The front shield will then be released and the probe, whose main objective is to study Titan?s atmosphere, will open inlet ports and deploy booms to collect the scientific data. All instruments will have direct access to the atmosphere to conduct detailed in-situ measurements of its structure, dynamics and chemistry. Imagery of the surface along the track will also be acquired. These data will be transmitted directly to the Cassini orbiter, which, at the same time, will be flying over Titan at 60 000 km at closest approach. Earth-based radiotelescopes will also try to detect the signal?s tone directly.
Huygens changing its parachutes
After 15 minutes, at about 120 km, Huygens will release its main parachute and a smaller 3 m drogue chute will take over to allow a deeper plunge through the atmosphere within the lifetime of the probe?s batteries.
The descent will last about 140 minutes before Huygens impacts the surface at about 6 m/s. If the probe survives all this, its extended mission will start, consisting in direct characterisation of Titan?s surface for as long as the batteries can power the instruments and the Cassini orbiter is visible over the horizon at the landing site, i.e. not more than 130 minutes.
At that time, the Cassini orbiter will reorient its main antenna dish toward Earth in order to play back the data collected by Huygens, which will be received by NASA?s 70-m diameter antenna in Canberra, Australia, 67 minutes later. Three playbacks are planned, to ensure that all recorded data are safely transmitted to Earth. Then Cassini will continue its mission exploring Saturn and its moons, which includes multiple additional flybys of Titan in the coming months and years.
A probe deep into space and time
Bigger than Mercury and slightly smaller than Mars, Titan is unique in having a thick hazy nitrogen-rich atmosphere containing carbon-based compounds that could yield important clues about how Earth came to be habitable. The chemical makeup of the atmosphere is thought to be very similar to Earth?s before life began, although colder (-180?C) and so lacking liquid water. The in-situ results from Huygens, combined with global observations from repeated flybys of Titan by the Cassini orbiter, are thus expected to help us understand not only one of the most exotic members of our Solar System but also the evolution of the early Earth’s atmosphere and the mechanisms that led to the dawn of life on our planet.
Europe?s main contribution to the Cassini mission, the Huygens probe, was built for ESA by an industrial team led by Alcatel Space. This 320 kg spacecraft is carrying six science instruments to study the atmosphere during its descent. Laboratories and research centres from all ESA member countries, the United States, Poland and Israel have been involved in developing this science payload. The Huygens atmospheric structure instrument package (HASI) will measure temperature and pressure profiles, and characterise winds and turbulences. It will also be able to detect lightning and even to measure the conductivity and permittivity of the surface if the probe survives the impact. The gas chromatograph mass spectrometer (GCMS) will provide fine chemical analysis of the atmosphere and the aerosols collected by the aerosol collector and pyrolyser (ACP). The descent imager/spectral radiometer (DISR) will collect images, spectra and other data on the atmosphere, the radiation budget, cloud structures, aerosols and the surface. The doppler wind experiment (DWE) will provide a zonal wind profile while the surface science package (SSP) will characterise the landing site if Huygens survives the impact.
The Cassini-Huygens mission is a cooperation between NASA, the European Space Agency and ASI, the Italian space agency. The Jet Propulsion Laboratory (JPL), a division of the California Institute of Technology in Pasadena, is managing the mission for NASA?s Office of Space Science, Washington. JPL designed, developed and assembled the Cassini orbiter.
Original Source: ESA News Release
The first ground based infrared spectrum of Jupiter’s moon Amalthea reveals that it must have formed far from its current location. This new result, based on observations with the Subaru telescope and the NASA Infrared Telescope Facility by a team of researchers from the National Astronomical Observatory of Japan, the University of Hawaii, and the University of Tokyo, sheds new light on our Solar System’s turbulent past.
Planets like Earth and Jupiter formed from the disk of gas and dust swirling around the Sun at the time of its birth. Rocky planets like Earth formed in the high temperature environment close to the Sun, while large gaseous planets like Jupiter formed in the cooler regions farther away. Similarly, Jupiter, the largest planet in the solar system, probably had its own disk of gas and dust. The four moons of Jupiter discovered by Galileo (Io, Europa, Ganymede, and Callisto) are likely to have been born from this disk.
In addition to the Galilean moons, Jupiter has two other types of satellites: four small inner moons orbiting Jupiter within the orbit of Io, the inner most Galilean satellite, and at least fifty five small outer moons outside the orbit of Callisto, the outer most Galilean satellite. All the outer satellites have tell-tale orbits that reveal that they must have been captured by Jupiter during or after the formation of the planet and its larger moons.
The origin of the four small inner moons remain a mystery, however. They have orbits compatible with the hypothesis that they formed in orbit around Jupiter like the Galilean moons. On the other hand, their small irregular shapes and their comparatively low reflectivity and low densities resemble asteroids and suggest that they were captured by Jupiter’s gravitational pull just like the outer moons.
The mystery persists because of the challenge inherent in observing Jupiter’s small inner moons from Earth. The moons are small and therefore faint, and they are obscured by the bright glare from Jupiter. Although NASA’s space probes Voyager and Galileo have captured detailed images of Jupiter’s small inner moons, these data have been insufficient for resolving the question of their origin.
Naruhisa Takato from the National Astronomical Observatory of Japan and his collaborators have now had success in obtaining the first infrared spectrum of two of Jupiter’s small inner moons, Amalthea and Thebe. To obtain a spectrum over a wide range of infrared wavelengths, the group combined the strengths of two instruments on two telescopes on the summit of Mauna Kea, Hawaii. For high resolution spectroscopy at wavelengths longer than 3 ?m ,the group used the Infrared Camera and Spectrograph on the Subaru telescope. For shorter wavelengths, the group used SpeX on the NASA IRTF, which has broad wavelength coverage.
The new spectrum of Amalthea shows the characteristic signatures of water. The most likely location of this water is within water containing hydrous minerals. Such minerals typically form in low temperature environments, ruling out the possibility that Amalthea could have formed in the high temperature environment of Jupiter’s immediate neighborhood while the planet was forming and where Amalthea
now is.
If Amalthea did not form near its present location, where did it come from? The surface of Amalthea resembles regions of Callisto that are not covered by ice. This suggests that Amalthea may have been one of the many small “micro-satellites” orbiting Jupiter that was sucked into an inner orbit when the Galilean moons formed. However, the spectrum of Amalthea has similarities with asteroids orbiting the Sun, suggesting that is was a “micro-planet” that was pulled into Jupiter’s orbit when Jupiter itself was forming.
Takato says “although we think Jupiter’s moons formed as an assembly of many smaller bodies, the same way we think planets formed from ‘planetesimals’, until now we have not found any example of the original building blocks of a planet’s moon. However, our results strengthen the argument that Amalthea is one of the few remaining pieces of the material that formed the Galilean moons. Amalthea may have ended up in orbit close to Jupiter rather than get incorporated into a larger moon or Jupiter itself. If this is the case, Amalthea would be the first known example of a ‘satellitesimal.'”
Original Source: Subaru News Release
