A nebula (seen in cyan) that is about two million light-years across. It was found surrounding the bright quasar UM287 (center). Credit: S. Cantalupo (UCSC)
Funny how a single quasar can illuminate — literally and figuratively — some of the mysteries of the universe. From two million light-years away, astronomers spotted a quasar (likely a galaxy with a supermassive black hole in its center) shining on a nearby collection of gas or nebula. The result is likely showing off the filaments thought to connect galaxies in our universe, the team said.
“This is a very exceptional object: it’s huge, at least twice as large as any nebula detected before, and it extends well beyond the galactic environment of the quasar,” stated Sebastiano Cantalupo, a postdoctoral fellow at the University of California Santa Cruz who led the research.
The find illuminated by quasar UM287 could reveal more about how galaxies are connected with the rest of the “cosmic web” of matter, astronomers said. While these filaments were predicted in cosmological simulations, this is the first time they’ve been spotted in a telescope.
“Gravity causes ordinary matter to follow the distribution of dark matter, so filaments of diffuse, ionized gas are expected to trace a pattern similar to that seen in dark matter simulations,” UCSC stated.
A graphic showing how matter in the universe could be distributed. Some astronomers believe matter is sprinkled as a a “cosmic web” of filaments. The larger section shows a dark-matter simulation (by Anatoly Klypin and Joel Primack) and the inset a smaller portion, 10 million light-years across, from another simulation that also includes gas (S. Cantalupo). Credit: S. Cantalupo (UCSC), Joel Primack (UCSC) and Anatoly Klypin (NMSU).
Astronomers added that it was lucky that the quasar happened to be shining in the right direction to illuminate the gas, acting as a sort of “cosmic flashlight” that could show us more of the underlying matter. UM287 is making the gas glow in a similar way that fluorescent light bulbs behave on Earth, the team added.
“This quasar is illuminating diffuse gas on scales well beyond any we’ve seen before, giving us the first picture of extended gas between galaxies,” stated J. Xavier Prochaska, coauthor and professor of astronomy and astrophysics at UC Santa Cruz. “It provides a terrific insight into the overall structure of our universe.”
Dots (circled) in this image show the first asteroid spotted by NASA's Near-Earth Object Wide-field Infrared Survey Explorer (NEOWISE) after the mission came out of hibernation. Credit: NASA
If anything, NASA’s asteroid-hunting spacecraft seems to be refreshed after going into forced hibernation for 2.5 years. In the first 25 days since it started seeking small solar system bodies in earnest again, the Near-Earth Object Wide-field Infrared Survey Explorer (NEOWISE) found three new objects and detected an additional 854, NASA said Thursday (Jan. 23).
Luckily for people interested in this field, Amy Mainzer (the principal investigator for this mission) has been tweeting out discoveries as they come — and other observations besides. “Just passed our @WISE_Mission post-restart review. I believe the technical term is “Yee haw!!” she wrote Jan. 21. Below are a couple of illustrated examples of discoveries from her Twitter feed. Click on the pictures for larger versions.
In a release, NASA added that NEOWISE is “observing and characterizing” one NEO a day, which means not only looking at the object, but probing its size and composition. Astronomers know of about 10,500 NEOs, but of those only 10% (or about 1,500) have physical measurements cataloged as well. NEOWISE investigators aim to make hundreds of more of these measurements.
The mission (originally called WISE) launched in December 2009 to examine the universe in infrared light. After completely mapping the sky, it ran out of coolant it needed to do this work in 2010. It then shifted to examining comets and asteroids before being put into hibernation in February 2011. Read more about its mission history in this past Universe Today article.
A direct image of a brown dwarf companion (arrowed) taken at the Keck Observatory. (Credit: Crepp et al. 2014 APJ).
A recent find announced by astronomers may go a long ways towards understanding a crucial “missing link” between planets and stars.
The team, led by Friemann Assistant Professor of Physics at the University of Notre Dame’s Justin R. Crepp, recently released an image of a brown dwarf companion to a star 98 light years or 30 parsecs distant. This discovery marks the first time that a T-dwarf orbiting a Sun-like star with known radial velocity acceleration measurement has been directly imaged.
Located in the constellation Eridanus, the object weighs in at about 52 Jupiter masses, and orbits a 0.95 Sol mass star 51 Astronomical Units (AUs) distant once every 320-1900 years. Note that this wide discrepancy stems from the fact that even though we’ve been following the object for some 17 years since 1996, we’ve yet to ascertain whether we’ve caught it near apastron or periastron yet: we just haven’t been watching it long enough.
The T-dwarf, known as HD 19467 B, may become a benchmark in the study of sub-stellar mass objects that span the often murky bridge between true stars shining via nuclear fusion and ordinary high mass planets.
Brown dwarfs are classified as spectral classes M, L, T, and Y and are generally quoted as having a mass of between 13 to 80 Jupiters. Brown dwarfs utilize a portion of the proton-proton chain fusion reaction to create energy, known as deuterium burning. Low mass red dwarf stars have a mass range of 80 to 628 Jupiters or 0.75% to 60% the mass of our Sun. The Sun has just over 1,000 times Jupiter’s mass.
Researchers used data from the TaRgeting bENchmark-objects with Doppler Spectroscopy (TRENDS) high-contrast imaging survey, and backed it up with more precise measurements courtesy of the Keck observatory’s High-Resolution Echelle Spectrometer or HIRES instrument.
An artist’s conception of a T-type brown dwarf. (Credit: Tyrogthekreeper under a Wikimedia Commons Attribution-Share Alike 3.0 Unported license).
TRENDS uses adaptive optics, which relies on precise flexing the telescope mirror several thousands of times a second to compensate for the blurring effects of the atmosphere. Brown dwarfs shine mainly in the infrared, and objects such as HD 19467 B are hard to discern due to their close proximity to their host star. In this particular instance, for example, HD 19467 B was over 10,000 times fainter than its primary star, and located only a little over an arc second away.
“This object is old and cold and will ultimately garner much attention as one of the most well-studied and scrutinized brown dwarfs detected to date,” Crepp said in a recent Keck observatory press release. “With continued follow-up observations, we can use it as a laboratory to test theoretical atmospheric models. Eventually we want to directly image and acquire the spectrum of Earth-like planets. Then, from the spectrum, we should be able to tell what the planet is made of, what its mass is, radius, age, etc… basically all of its relevant properties.
Discovery of an Earth-sized exoplanet orbiting in a star’s habitable zone is currently the “holy grail” of exoplanet science. Direct observation also allows us to pin down those key factors, as well as obtain a spectrum of an exoplanet, where detection techniques such as radial velocity analysis only allow us to peg an upper mass limit on the unseen companion object.
This also means that several exoplanet candidates in the current tally of 1074 known worlds beyond our solar system also push into the lower end of the mass limit for substellar objects, and may in fact be low mass brown dwarfs as well.
Another key player in the discovery was the Near-Infrared Camera (second generation) or NIRC2. This camera works in concert with the adaptive optics system on the Keck II telescope to achieve images in the near infrared with a better resolution than Hubble at optical wavelengths, perfect for brown dwarf hunting. NIRC2 is most well known for its analysis of stellar regions near the supermassive black hole at the core of our galaxy, and has obtained some outstanding images of objects in our solar system as well.
The hexagonal primary mirror of the Keck II telescope. (Credit: SiOwl. A Wikimedia Commons image under a Creative Commons Attribution 3.0 Unported license).
What is the significance of the find? Free floating “rogue” brown dwarfs have been directly imaged before, such as the pair named WISE J104915.57-531906 which are 6.5 light years distant and were spotted last year. A lone 6.5 Jupiter mass exoplanet PSO J318.5-22 was also found last year by the PanSTARRS survey searching for brown dwarfs.
“This is the first directly imaged T-dwarf (very cold brown dwarf) for which we have dynamical information independent of its brightness and spectrum,” team lead researcher Justin Crepp told Universe Today.
Analysis of brown dwarfs is significant to exoplanet science as well.
“They serve as an essential link between our understanding of stars and planets,” Mr. Crepp said. “The colder, the better.”
And just as there has been a controversy over the past decade concerning “planethood” at the low end of the mass scale, we could easily see the debate applied to the higher end range, as objects are discovered that blur the line… perhaps, by the 23rd century, we’ll finally have a Star Trek-esque classifications scheme in place so that we can make statements such as “Captain, we’ve entered orbit around an M-class planet…”
Something that’s always been fascinating in terms of red and brown dwarf stars is also the possibility that a solitary brown dwarf closer to our solar system than Alpha Centauri could have thus far escaped detection. And no, Nibiru conspiracy theorists need not apply. Mr. Crepp notes that while possible, such an object is unlikely to have escaped detection by infrared surveys such as WISE. But what a discovery that’d be!
A composite image (X-ray and optical wavelengths) showing galaxy cluster RX J1532.9+3021 and the black hole at its center. Credit: X-ray: NASA/CXC/Stanford/J.Hlavacek-Larrondo et al, Optical: NASA/ESA/STScI/M.Postman & CLASH team
Got gas? The black hole in galaxy cluster RX J1532.9+3021 is keeping it all for itself and stopping trillions of stars from coming to be, according to new research. You can see data above from NASA’s Chandra X-ray Observatory (purple) and the Hubble Space Telescope (yellow).
The drama is taking place about 3.9 billion light-years from Earth, showing an extreme phenomenon that has been noted in other galaxies on smaller scales, Chandra officials stated.
“The large amount of hot gas near the center of the cluster presents a puzzle,” a statement read. “Hot gas glowing with X-rays should cool, and the dense gas in the center of the cluster should cool the fastest. The pressure in this cool central gas is then expected to drop, causing gas further out to sink in towards the galaxy, forming trillions of stars along the way. However, astronomers have found no such evidence for this burst of stars forming at the center of this cluster.”
Black hole with disc and jets visualization courtesy of ESA
What’s blocking the stars (according to data from Chandra and the National Science Foundation’s Karl G. Jansky Very Large Array) could be supersonic jets blasting from the black hole and shoving the gas in the area away, forming cavities on either side of the galaxy. These cavities, by the way, are immense — at 100,000 light-years across each, this makes them about as wide as our home galaxy, the Milky Way.
The big question is where that power came from. Perhaps the black hole is “ultramassive” (10 billion times of the sun) and has ample mass to shoot out those jets without eating itself up and producing radiation. Or, the black hole could be smaller (a billion times that of the sun) but spinning quickly, which would allow it to send out those jets.
Jupiter as imaged by Michael Phillips on July 25th, 2009.
Jupiter is a happening place in the solar system. While bashful Mars only puts on a good show once every two year opposition period, and inner worlds such as Mercury and Venus yield no surface details to backyard observers at all, the cloud tops of Jupiter display a wealth of changing detail in even modest backyard telescopes.
And this month is a great time to start observing Jupiter, as the largest planet in our solar system just passed opposition on January 5th. Recently, veteran astrophotographer Michael Phillips amazed us here at Universe Today once again with a stunning time-lapse sequence of Jupiter and its moons Ganymede and Io. Now, he’s outdone himself with a new full rotation compilation of the gas giant planet.
The capture is simply mesmerizing to sit and watch. At 9.9 hours, Jupiter has the fastest rotational period of any planet in our solar system. In fact, with Jupiter currently visible low to the east at sunset, it’s possible to follow it through one rotation in the span of a single long January winter night.
We caught up with Michael recently and asked him about this amazing capture. The sequence was actually accomplished over the span of five successive evenings. This made it challenging to stitch together using a sophisticated program known as WINJupos.
“While this is possible on a long winter night when it is darker longer, I typically find it easier to do over multiple nights than one long sleepless night,” Michael told Universe Today. “If you wait too many days between observations, the features will change significantly, and then two nights will not match up clearly. The seams that result from using multiple nights are tricky to stick together. I created multiple non-overlapping seams and tried to blend them out against one another as layers in my image editing software. The result is smoother, but not quite the same as a single observation.”
A 14” f/4.5 Newtonian reflecting telescope was used for the captures. “Similar weather conditions and camera settings help quite a bit to make the multiple nights’ segments match up better,” Michael noted. “Keeping the same settings, using the same location away from my house in the corner of the yard (to reduce local atmospheric turbulence) night after night gives consistent results after removing the variability of the weather.”
Planetary photography also requires special considerations prior to imaging, such as getting Jupiter high enough in the sky and at specific longitudes to get full coverage in the rotation sequence.
“I try to consider the local weather patterns and atmospheric stability (seeing), but in reality, I pushed myself to get out as much and often as I could,” Michael told Universe Today. “Typically, I try to wait until Jupiter is at the highest in the sky, as the result is looking through less atmosphere and thus more stable conditions. Sometimes, the planets jiggle around and you just want to scream ‘SIT STILL!’ Basically around the time of opposition I go out as often as it’s clear, as those are opportunities that you don’t get back again until next year.”
Jupiter reaches opposition just over once every 13 months, moving roughly one constellation eastward each time. 2013 was an “oppositionless” year for Jupiter, which won’t occur again until 2025. Michael also notes that from his observing location at 35 degrees north latitude, Jupiter currently peaks at an altitude of 77 degrees above the horizon when it transits the local meridian. “I wasn’t going to squander it waiting for perfect conditions!”
In fact, Jupiter is currently in a region in the astronomical constellation of Gemini that will be occupied by the Sun in just over five months time during the June Solstice. Currently at a declination of around 22 degrees 45’ north, Jupiter won’t appear this high in the northern sky near opposition again until 2026.
It’s also amazing to consider the kind of results that backyard observers like Michael Phillips are now routinely accomplishing. It’s an interesting exercise to compare Michael’s capture side-by-side with a sequence captured by NASA’s New Horizons spacecraft during its 2006 flyby of Jupiter:
Both sequences capture a wealth of detail, including the enormous Great Red Spot, the Northern and Southern Equatorial Belts, and numerous white spots and smaller swirls and eddies in the Jovian atmosphere.
To date, six spacecraft (Pioneer 10 and 11, Voyagers 1 and 2, New Horizons and Cassini) have made flybys of Jupiter, and one, Galileo, orbited the planet until its demise in 2003. Juno is the next in this legacy, and will be inserted into orbit around Jupiter in July 2016.
Now is the time to get out and observe and image Jupiter and its moons, as it moves higher into the sky on successive evenings towards eastern quadrature on April 1st, 2014.
Congrats to Michael Phillips on an amazing sequence!
Before and after photos of the bright galaxy M81 showing the appearance of a brand new supernova. The object is located 54" west and 21" south of the galaxy's center. Credit: E. Guido, N. Howes, M. Nicolini
Wow! Now here’s a supernova bright enough for even small telescope observers to see. And it’s in a bright galaxy in Ursa Major well placed for viewing during evening hours in the northern hemisphere. Doesn’t get much better than that! The new object was discovered last night by S.J. Fossey; news of the outburst first appeared on the Central Bureau for Astronomical Telegrams “Transient Objects Confirmation Page”
An animation showing a comparison between the confirmation image of supernova in M82 by the team from the Remanzacco Observatory and archive image by a 2-meter telescope FTN – LCOGT from November 22, 2013. Click on the image for a larger version. Credit: E. Guido, N. Howes, M. Nicolini.
Astronomers are saying this new supernova is currently at magnitude +11 to +12, so its definitely not visible with the naked eye. You’ll need a 4 inch telescope at least to be able to see it. That said, at 12 million light years away, this is (at the moment) the brightest, closest supernova since SN 1993 J kaboomed in neighboring galaxy M81 21 years ago in 1993. M81 and M82, along with NGC 3077, form a close-knit interacting group.
Another view of the galaxy M82 with the new bright supernova photographed earlier today. M82 glows at magnitude 8.4 and a popular object for telescopes of every size. Credit: Leonid Elenin
It’s amazing it wasn’t found and reported sooner (update — see below, as perhaps it was!). M82 is a popular target for beginning and amateur astronomers; pre-discovery observations show it had already brightened to magnitude 13.9 on the 16th, 13.3 on the 17th and 12.2 on the 19th. Cold winter weather and clouds to blame?
This is the starburst galaxy M82 imaged by Hubble in 2006, with approximate location of the new supernova noted. Image credit: NASA/ESA and the Hubble Heritage team, image notation by Jason Major.
M82 is a bright, striking edge-on spiral galaxy bright enough to see in binoculars. Known as the Cigar or Starburst Galaxy because of its shape and a large, active starburst region in its core, it’s only 12 million light years from Earth and home to two previous supernovae in 2004 and 2008. Neither of those came anywhere close to the being as bright as the discovery, and it’s very possible the new object will become brighter yet.
Evolution of a Type Ia supernova. A superdense white dwarf star draws matter from a companion star, reaches a critical limit and then burns catastrophically. Credit: NASA/CXC/M. Weiss
PSN J09554214+6940260 is a Type Ia supernova. Type Ia (one-a), a dry term describing one of the most catastrophic events in the universe. Here a superdense white dwarf, a star only about the size of Earth but with the gravitational power of a sun-size star, pulls hydrogen gas from a nearby companion down to its surface where it adds to the star’s weight.
When the dwarf packs enough pounds to reach a mass 1.4 times that of the sun, it can no longer support itself. The star suddenly collapses, heats to incredible temperatures and burns up explosively in a runaway fusion reaction. What we see here on Earth is the sudden appearance of a brand new star within the galaxy’s disk. Of course, it’s not really a new star, but rather the end of an aged one.
This map shows the sky facing north-northeast at 8 p.m. local time in late January. The supernova is located about a “fist” above the Dipper Bowl in M82. Right next door is the equally bright M81 galaxy. It’s easy to tell them apart. M81 is round with a bright core; M82 looks like a streak mark. See detailed map below. Stellarium
I know you’re as excited as I am to get a look at this spectacular new star the next clear night, so I’ve prepared a couple maps to help you find the galaxy. The best time to see the supernova is as soon as the sky gets dark when it’s already up in the northeastern sky above the Dipper Bowl, but since it’s circumpolar for mid-latitude observers, you can check it out any time of night.
To find M82, look about 7 degrees (not quite a fist held at arm’s length) above the Bowl to find 23 UMa, an easy naked eye star. From there you can star hop to a little triangle and over to a pair of stars (the “line”). M82 and M81 are about half a degree below the line. Stellarium
My maps show its position for around 8 o’clock. When you dial in the galaxy in your telescope, look for a starry point along its long axis west and south of the nucleus. All the fury of this fantastic blast is concentrated in that meek spark of light glimmering in the galactic haze.
UPDATE: Sketch of M82 and its supernova, now designated SN 2014J, made at 9 p.m. CST Jan. 22 with a 15-inch (37 cm) telescope. A perfect arc of 3 stars (left) takes you right to it. The object is the only bright star shining in the galaxy. Amazingly easy to see. Numbers shown are magnitudes from the AAVSO – use them to help you gauge 2014J’s brightness changes. Credit: Bob King
UPDATE: Fraser and team from the Virtual Star Party actually imaged M82 on Sunday evening, and you can see it in the video below at the 22 minute mark. It really looks like a bright spot is showing up — and that’s about a day before it was announced. Did they catch it? In the video the galaxy appears upside down as compared to the images here:
Screenshot from the January 19 Virtual Star Party (right) compared to image from Meineko Sakura of the Tao Astronomical Observatory of the new supernova.
Some of the most amazing celestial sights are hidden from our view in the daytime sky. Or are they? We recently challenged readers to try and follow the planet Venus through inferior conjunction as it passed between the Earth and the Sun on January 11th. Unlike the previous pass on June 6th, 2012 when Venus made its last transit of the Sun for the 21st century, the 2014 solar conjunction offered an outstanding chance to trace Venus’s path just five degrees from the Sun from the dusk and into the dawn sky.
Expert astrophotographers Shahrin Ahmad based in Sri Damansara, Malaysia and Paul Stewart observing from New Zealand took up that daily challenge as Venus neared the limb of the Sun, with amazing results. Now, Shahrin has also produced an amazing time-lapse sequence of Venus passing through inferior conjunction.
You can actually see the illuminated “horns” of Venus as they thin, extend, and rotate around the limb as the planet passes the Sun.
And it’s what’s more incredible is that the capture was completed in the daytime. But such a feat isn’t for the unskilled. Shahrin told Universe Today of the special safety precautions he had to take to acquire Venus so close to the Sun:
“Since Venus was getting closer each day towards conjunction, I found it far too dangerous to find visually, either using the main telescope or the finderscope.”
Instead, Shahrin relies on computerized software named Cartes du Ciel to drive his Skywatcher EQ6 mount and pinpoint Venus in the daytime sky.
“The sky in Kuala Lumpur is never clear from here, thus it rarely appears dark blue, making it almost impossible to spot Venus visually, especially when it is less than 10 degrees from the Sun.”
Shahrin elaborated further on his special solar safety precautions:
“I always start with all covers in place and the solar filter on the main telescope. I will slew the telescope to the Sun, make some slight repositioning adjustments, and then synchronize the telescope to the new position. After ensuring the Sun is visible and centered on the computer screen, I slew to Venus. Once the mount has stopped in position, I remove the solar filter and replace it with a makeshift cardboard extender mounted on the existing dew-shield. This ensures that any direct sunlight is totally blocked from entering the optics.”
Shahrin notes that 90% of the time, Venus with appear on the computer screen after aligning. Otherwise, a brief spiral search of the field will slide it into view.
Shahrin observes from his ShahGazer Observatory, a roll-off-roof observatory just outside of Kuala Lumpur. He used the Skywatcher 120ED refractor pictured for the captures, with a 2x Barlow lens to achieve a focal length of 1800mm. Shahrin’s main camera is a QHY CCD IMG132e, and the rig is mounted on a Skywatcher EQ6.
A closeup of Sharin’s barlow and camera rig. Credit: Shahrin Ahmad.
“The experience of being able to track Venus approaching inferior conjunction over the Sun afterwards is exhilarating,” Shahrin told Universe Today. “It felt like watching and waiting for a total eclipse of the Sun, but in slow motion!”
Shahrin also counts himself lucky to have had a string of clear days leading up to and after inferior conjunction.
Shahrin’s capture of Venus 5 degrees from the Sun just 8 hours before inferior conjunction may also be a record. That’s a closer apparent separation than our visual sighting of Venus 7 hours and 45 minutes after inferior conjunction on January 16th 1998 as seen from North Pole Alaska, when the planet passed 5.5 degrees from the limb of the Sun.
“I’ve also noticed that in some of the photos, we can see a slight ‘glint’ of sunshine on part of Venus’ atmosphere,” Shahrin noted to Universe Today. “(This sighting) was actually confirmed by the RASC Edmonton Centre in Canada via their Twitter feed.”
An amazing capture, indeed. Venus is now back in the realm of visibility for us mere mortal backyard observers low in the dawn sky, shining at a brilliant magnitude -4.3. Expect it to vault up in a hurry for northern hemisphere observers as the favorable angle of the ecliptic will give it a boost in the dawn. Venus is also headed towards a spectacular 0.2 degree conjunction with Jupiter this summer on August 18th: expect UFO sightings to rise correspondingly. The Indian Army even briefly mistook the pair for Chinese spy drones early last year.
The waning crescent Moon approaches Venus on the morning of January 28th, 2014. Created using Stellarium.
Venus will spend most of 2014 in the dawn sky and is headed for superior conjunction on October 25th, 2014. Venus spent a similar span in the dawn for the majority 2006, and will do so again in 2022. It’s all part of the 8-year cycle of Venus, a span over which apparitions of the planet roughly repeat. And the next shot we’ll have at inferior conjunction? That’ll be on August 15th, 2015 for favoring the southern hemisphere and March 25th, 2017 once again favoring the northern, when the planet very nearly passes as far from the Sun as it can appear at inferior conjunction at 8 degrees.
Congrats to Shahrin on his amazing capture!
-Follow the stargazing adventures of Sharin Ahmad on Google+ and as @shahgazer on Twitter
Three stages of the evolution of the galaxy simulation used to model the Milky Way. (Credit: AIP)
For decades astronomers have puzzled over the many details concerning the formation of the Milky Way Galaxy. Now a group of scientists headed by Ivan Minchev from the Leibniz Institute for Astrophysics Potsdam (AIP) have managed to retrace our galaxy’s formative periods with more detail than ever before. This newly published information has been gathered through careful observation of stars located near the Sun and points to a rather “moving” history.
To achieve these latest results, astronomers observed stars perpendicular to the galactic disc and their vertical motion. Just to shake things up, these stars also had their ages considered. Because it is nearly impossible to directly determine a star’s true age, they rattled the cage of chemical composition. Stars which show an increase in the ratio of magnesium to iron ([Mg/Fe]) appear to have a greater age. These determinations of stars close to the Sun were made with highly accurate information gathered by the RAdial Velocity Experiment (RAVE). According to previous findings, “the older a star is, the faster it moves up and down through the disc”. This no longer seemed to be true. Apparently the rules were broken by stars with the highest magnesium-to-iron ratios. Despite what astronomers thought would happen, they observed these particular stars slowing their roll… their vertical speed decreasing dramatically.
So what’s going on here? To help figure out these curious findings, the researchers turned to computer modeling. By running a simulation of the Milky Way’s evolutionary patterns, they were able to discern the origin of these older, slower stars. According to the simulation, they came to the conclusion that small galactic collisions might be responsible for the results they had directly observed.
Smashing into, or combining with, a smaller galaxy isn’t new to the Milky Way. It is widely accepted that our galaxy has been the receptor of galactic collisions many times during its course of history. Despite what might appear to be a very violent event, these incidents aren’t very good at shaking up the massive regions near the galactic center. However, they stir things up in the spiral arms! Here star formation is triggered and these stars move away from the core towards our galaxy’s outer edge – and near our Sun.
In a process known as “radial migration”, older stars, ones with high values of magnesium-to-iron ratio, are pushed outward and display low up-and-down velocities. Is this why the elderly, near-by stars have diminished vertical velocities? Were they forced from the galactic center by virtue of a collision event? Astronomers speculate this to be the best answer. By comparison, the differences in speed between stars born near the Sun and those forced away shows just how massive and how many merging galaxies once shook up the Milky Way.
Says AIP scientist Ivan Minchev: “Our results will enable us to trace the history of our home galaxy more accurately than ever before. By looking at the chemical composition of stars around us, and how fast they move, we can deduce the properties of satellite galaxies interacting with the Milky Way throughout its lifetime. This can lead to an improved understanding of how the Milky Way may have evolved into the galaxy we see today.”
An occultation occurs when one foreground celestial object completely obscures another. Technically, a total solar eclipse is an occultation of the Sun by the Moon, although it’s never referred to as such. The term finds modern usage mainly for the blocking of stars and planets by the Moon. Very occasionally, an asteroid or planet can occult a distant star as well.
And yes, the modern astronomical term “occultation” traces its hoary roots back to the days when astronomy was intertwined with the pseudoscience of astrology. To this day, the term still makes some folks wonder if astronomers are secretly casting horoscopes. Trust us, you’re still on a solid astronomical footing to use the term “occultation.”
Unfortunately, the January 25thoccultation of Saturn by the Moon will only grace part of Antarctica, southern Argentina and Chile, and the Falkland Islands post-sunrise. The rest of us still will see a very photogenic pass of Saturn near the waning crescent Moon on the morning of Saturday, January 25th. The Moon will pass just about a degree — two times its apparent width — south of Saturn for northern hemisphere observers.
The footprint for the January 25th occultation of Saturn by the Moon. dashed lines indicate where the events occurs in the daytime sky. (Created using Occult 4.0.11 software)
Both the Moon and Saturn will reside in the astronomical constellation of Libra this weekend during closest passage. The pair will rise around 2 AM local. After their brief tryst, the Moon will head towards New on January 30th while Saturn will continue to rise successively earlier as its heads towards opposition and the start of evening Saturn observing season on May 10th, 2014.
January 2014 is also notable for having two New Moons, an occurrence informally known as a Black Moon. This occurs again this year in March, and February 2014 is devoid of a New Moon. February is the only month that can be “missing a Moon phase” as it’s the only one shorter the synodic period of 29.5 days, in which the Moon returns to like phase.
Saturn as imaged by the author in 2012.
In the telescope, Saturn will present a +0.8 magnitude disk 16” across (38” with rings from tip-to-tip). Saturn’s rings are tipped open to our line of sight by about 22 degrees in 2014, and are widening towards a maximum of 27 degrees in 2016 through 2017. If you have an equatorial telescope with tracking capability, it may be possible this weekend to follow Saturn up into the daytime sky. Though Saturn isn’t quite bright enough to see in the daytime unaided, it might just be possible to spy using binoculars on the 25th using the nearby crescent Moon as a guide. Saturn is a tough daytime target to be sure, but it’s not impossible to acquire with a little skill and patience.
The current cycle of occultations of Saturn began on December 1st, 2013 and ends on November 22nd, 2014. The cycle will move progressively northward through the year.
The Moon and Saturn put on a repeat performance over almost the same exact location (this time in darkness) on April 17th, 2014, and the best event in the cycle for North America will be the August 31st daytime occultation of Saturn by the waxing crescent Moon.
Now for the wow factor of what you’re seeing. On Saturday morning, the Moon is just over 371,000 kilometres distant, or a little over a light second away. Saturn is over four thousand times more remote at just over 10.1 astronomical units (AUs) distant, which works out to 1.5 billion kilometres, or over 83 light minutes away. And although the Moon is over a 112 times larger in apparent diameter than Saturn as seen from the Earth, the globe of Saturn is actually over 34 times bigger.
Saturn and the Moon crossing the local meridian shortly after sunset on January 25th. Created using Starry Night Education Software.
And though we’ve been to the Moon lots since the dawn of the Space Age, only two spacecraft (Voyagers 1 and 2) have made brief flybys of the ringed world, and only one – Cassini – has orbited it. Note that China’s Chang’e-3 lander and rover are about to experience their second sunset this weekend as well from the lunar surface since landing on the Moon last month.
And although lots of planets get occulted by the Moon in 2014, no stars brighter than +1st magnitude lie in its path. In fact, the next cycle of bright star occultations by the Moon doesn’t resume until the Moon meets Aldebaran in January 29th, 2015.
There are, however, over a 100 lesser events involving the Moon occulting naked eye stars worldwide in 2014. Two such events occur this week as well, when the 48% illuminated Moon occults the +4.5th magnitude star Lambda Virginis for west-central South America on the morning of January 24th, and the occultation of the +2.8th magnitude star Alpha Librae (Zubenelgenubi) for central Asia on January 25th.
Don’t miss these celestial events, and be sure to send those pics in to Universe Today… there’s something for everyone happening in the sky this week worldwide!
Little by little we’re getting sharper, clearer pictures from the Chinese Chang’e 3 moon mission. Yesterday the lander beamed back a series of new photos taken with its panoramic camera. Stitched together, they give us a more detailed and colorful look of the rover’s surroundings in northern Mare Imbrium. I’ve ordered the images starting with a nice crisp view of the Yutu rover; from there we turn by degree to the right across the five frames. The final mosaic unfortunately doesn’t have the resolution yet of the other images. Perhaps one will be published soon.
The lander’s solar panels stand out in the foreground with a smattering of small craters nearby. Credit: Chinanews.comRight of the rover we see more panels and a radio communications dish. Credit: Chinanews.comA larger crater surrounded by what appears to be excavated impact ejecta is visible near the horizon at upper right. Credit: Chinanews.comYutu’s tracks and another crater with ejecta stand out in this final image. Credit: Chinanews.com
Complete, if small, panorama stitched from the single images. Credit: Chinanews.com
One thing that stands out to my eye when looking at the photos is the brown color of the lunar surface soil or regolith. Color images of the moon’s surface by the Apollo astronauts along with their verbal descriptions indicate a uniform gray color punctuated in rare spots by patches of more colorful soils.
Apollo 15 astronauts salutes next to the American flag in 1971. The moon’s regolith or soil appears a variety of shades of gray. Credit: NASA
The famous orange soil scooped up by Apollo 17 astronaut Eugene Cernan comes to mind. Because Apollo visited six different moonscapes – all essentially gray – it makes me wonder if the color balance in the Chinese images might be off. Or did Chang’e 3 just happen to land on browner soils?
The orange soil found by Apollo 17 astronauts really stands out against a uniform gray moonscape. Credit: NASA
