Long-exposure Cassini NAC image of Saturn's D ring system (NASA/JPL-Caltech/SSI)
The closest to the planet itself, the hazy arcs of Saturn’s D ring may lack the reflective brilliance and sharply-defined edges of the other main rings, but they nevertheless possess their own ethereal beauty and mysteries. Here, the Cassini spacecraft has managed to capture the soft bands of the D ring in a long-exposure image acquired on April 2, 2013 — so long an exposure, in fact, that background stars seen through the rings appear as long vertical streaks, a testament to the ring’s dimness as well as the spacecraft’s continuing movement.
Beginning 8,768 km (5,448 miles) above the tops of Saturn’s clouds, the D ring is the innermost and thinnest segment of Saturn’s main ring system. Nearly transparent, the D ring extends about 7,500 km (4,660 miles) before transitioning to the considerably brighter C ring, which is over twice as wide.
The innermost portion of the C ring can be seen above along the left side. Saturn’s shadow blankets the lower right corner.
The cause of the alternating light-and-dark bands observed within the D ring isn’t yet known, but they may be the result of an impact by a comet or large meteor that set up recurring waves of material.
The view was acquired at a distance of approximately 510,000 kilometers (317,000 miles) from Saturn and at a phase angle of 147 degrees. Image scale is 2 miles (3 kilometers) per pixel.
Opportunity captures a panoramic view of the road ahead to the raised rim of Solander Point (at left) which is some 0.8 mile (1.3 km) away. Arrival is targeted for August. It features a thick strata of ancient rocks which may harbor clay minerals indicative of a habitable zone and northerly tilted slopes to maximize power generation from the solar panels during upcoming 6th winter season at Endeavour crater rim. This navcam photo mosaic was taken on Sol 3330, June 6, 2013. Credit: NASA/JPL/Cornell//Marco Di Lorenzo/Ken Kremer (kenkremer.com)
On the cusp of the 10th anniversary since launching to the Red Planet, NASA’s long lived Opportunity rover has discovered a habitable zone on Mars that once coursed with ‘drinkable water’ and possesses the chemical ingredients necessary to support a path to potential Martian microbes.
At a rock called “Esperance”, Opportunity found a cache of phyllosilicate clay minerals that typically form in neutral, drinkable water that is not extremely acidic or basic.
The finding ranks as “One of my personal Top 5 discoveries of the mission,” said Steve Squyres of Cornell University, Ithaca, N.Y., principal investigator for NASA’s rover mission at a media briefing.
And despite her advancing age Opportunity remains healthy after surviving in excess of an incredible 3333 Sols, or days, trekking across the alien and ever harsh Martian crater plains.
Furthermore the intrepid robot just sat sail on a southerly course for a new destination called “Solander Point” where researches hope to find more even evidence of habitable environments since they already spotted deeper stakes of ancient rocks transformed by water eons ago. See our current photo mosaics showing Solander Point as Opportunity roves across the crater floor – above and below by Marco Di Lorenzo and Ken Kremer.
After weeks of trying, the rover deployed the robotic arm to drill at a sweet spot inside “Esperance” and collected convincing X-Ray spectroscopic data in the area she just investigated in May 2013 around the eroded rim of giant Endeavour Crater.
“Esperance is rich in clay minerals and shows powerful evidence of water alteration,” Squyres elaborated.
“This is the most powerful evidence we found for neutral pH water.”
“Clay minerals only tend to form at a more neutral pH. This is water you could drink,” Squyres gushed.
These finding represent the most favorable conditions for biology that Opportunity has yet seen in the rock histories it has encountered after nearly a decade roving the Red Planet.
“This is water that was much more favorable for things like pre-biotic chemistry – the kind of chemistry that could lead to the origin of life,” Squyres stated.
Opportunity snapped this color view of ‘Solander Point’ on June 1, 2013 (Sol 3325) looking south to her next destination which she should reach in August. The solar powered robot will spend the upcoming 6th winter season on northerly tilted slopes exploring the thick strata of ancient rocks. Credit: NASA/JPL-Caltech/Cornell Univ./Arizona State Univ.
Esperance is unlike any rock previously investigated by Opportunity; rich in aluminum, which is strongly indicative of clay minerals, perhaps like montmorillonite.
Most rocks inspected to date by Opportunity were formed in an environment of highly acidic water that is extremely harsh to most life forms.
“If you look at all of the water-related discoveries that have been made by Opportunity, the vast majority of them point to water that was a very low pH – it was acid,” Squyres explained.
Esperance was found on ‘Cape York’, a hilly segment of the western rim of Endeavour crater which spans 14 miles (22 km) across. The robot arrived at the edge of Endeavour crater in mid-2011 and will spend her remaining life driving around the scientifically rich crater rim segments.
The pale rock in the upper center of this image, about the size of a human forearm, includes a target called “Esperance,” which was inspected by NASA’s Mars Exploration Rover Opportunity. Data from the rover’s alpha particle X-ray spectrometer (APXS) indicate that Esperance’s composition is higher in aluminum and silica, and lower in calcium and iron, than other rocks Opportunity has examined in more than nine years on Mars. Preliminary interpretation points to clay mineral content due to intensive alteration by water. Credit: NASA/JPL-Caltech/Cornell/Arizona State Univ
NASA’s new Curiosity rover also recently discovered clay minerals and a habitable environment at Gale Crater – on the other side of Mars – stemming from a time when Mars was warmer and wetter billions of years ago.
Over time Mars became the cold and dry place it is today. Scientists hope the rovers provide clues to Mars dramatic transformation.
The solar powered rover is now driving as quick as possible to reach the northerly tilled slopes of ‘Solander Point’ in August, before the onset of the next Martian winter.
‘Solander Point’ offers a much taller stack of geological layering than ‘Cape York.’ Both areas are raised segments of the western rim of Endeavour Crater.
“There’s a lot to explore there. In effect, it’s a whole new mission,” said Ray Arvidson, the mission’s deputy principal scientific investigator from Washington University in St. Louis, Mo.
‘Esperance’ Target Examined by Opportunity in May 2013. The pale rock called “Esperance,” has a high concentration of clay minerals formed in near neutral water indcating a spot favorable for life. Credit: NASA/JPL-Caltech/Cornell Univ./Arizona State Univ.
Opportunity and her twin “Spirit” were launched to Mars on planned 90 day missions.
Both rovers have far exceeded everyone’s wildest expectations. Spirit endured more than 6 years inside Gusev Crater until succumbing to the bone chilling Martian winter in 2011.
NASA’s Opportunity Mars rover discovered clay minerals at Cape York ridge along the rim of Endeavour crater – seen in this photo mosaic – which stands as the most favorable location for Martian biology discovered during her entire nearly 10 year long mission to Mars. Opportunity also established a new American driving record for a vehicle on another world on May 15, 2013 (Sol 3309) and made history by driving ahead from this point at Cape York. This navcam photo mosaic shows the view forward to her next destinations of Solander Point and Cape Tribulation along the lengthy rim of huge Endeavour crater spanning 14 miles (22 km) in diameter.
Credit: NASA/JPL/Cornell/Ken Kremer (kenkremer.com)/Marco Di Lorenzo
Opportunity has lasted more than 37 times beyond the three month “warranty”.
“This is like your car not lasting 200,000 miles, or even a million miles. You’re talking about a car that lasts 2 million miles without an oil change,” Callas said. “At this point, how long Opportunity lasts is anyone’s guess.”
“Remember, the rover continues to operate in a very hostile environment, where we have extreme temperature changes every day, and the rover could have a catastrophic failure at anytime,” said John Callas, of NASA’s Jet Propulsion Laboratory, Pasadena, Calif., project manager for the Mars Exploration Rover Project.
“So every day is a gift.”
And don’t forget to “Send Your Name to Mars” aboard NASA’s MAVEN orbiter- details here. Deadline: July 1, 2013
June 23: “Send your Name to Mars on MAVEN” and “CIBER Astro Sat, LADEE Lunar & Antares Rocket Launches from Virginia”; Rodeway Inn, Chincoteague, VA, 8 PM
Opportunity captures the eerie Martian scenery looking south across Botany Bay from the southern tip of Cape York to her next destination – Solander Point, about 1 mile (1.6 km) away. This navcam photo mosaic was taken on Sol 3317, May 23, 2013. Credit: NASA/JPL/Cornell//Marco Di Lorenzo/Ken Kremer (kenkremer.com)Traverse Map for NASA’s Opportunity rover from 2004 to 2013.
This map shows the entire path the rover has driven during more than 9 years and over 3330 Sols, or Martian days, since landing inside Eagle Crater on Jan 24, 2004 to current location heading south to Solander Point from Cape York ridge at the western rim of Endeavour Crater.
Credit: NASA/JPL/Cornell/ASU/Marco Di Lorenzo/Ken Kremer
This article comes from our archive, but we updated it with this video.
Saturn is my absolute favorite object in the night sky. When I was a child, I had a dog-eared book on the Solar System, which I read over and over, stopping and staring with wonder at the section on Saturn. How could a planet have rings of ice? What would it be like to fly out and visit the planet, to see the rings with your own eyes. How did it get all those strange moons?
When I was 14, I purchased my first telescope, a 4-inch Newtonian from a local company in Vancouver. It was summer, and one of the first planets, appearing just after sunset was Saturn. And my telescope had just enough power and magnification to resolve the planet and its famous rings. In fact, when I first looked at Saturn through the eyepiece, I couldn’t believe that I was now seeing the planet with my own eyes. It didn’t look quite like the photographs, but my imagination could fill in the gaps.
From those first observations, my fascination with astronomy and Saturn only grew, leading me to a career in science journalism. It’s funny to think how far I’ve come, and how I can trace everything back to those warm summer nights, looking at Saturn.
Think you know everything about Saturn? Think again. Here are 10 facts about Saturn, some you may know, and some you probably didn’t know.
1. Saturn is the least dense planet in the Solar System
Saturn has a density of 0.687 grams/cubic centimeter. Just for comparison, water is 1 g/cm3 and the Earth is 5.52. Since Saturn is less dense than water, it would actually float like an apple if you could find a pool large enough. Of course, why you’d want to ruin a pool with all that hydrogen, helium and ices…
2. Saturn is a flattened ball
Saturn spins so quickly on its axis that the planet flattens itself out into an oblate spheroid. Seriously, you see this by eye when you look at a picture of Saturn; it looks like someone squished the planet a little. Of course, it’s the rapid spinning that’s squishing it, causing the equator to bulge out.
While the distance from the center to the poles is 54,000 km, the distance from the center to the equator is 60,300 km. In other words, locations on the equator are approximately 6,300 km more distant from the center than the poles.
We have a similar phenomenon here on Earth, where points on the equator are more distant from the center of the Earth, but on Saturn, it’s much more extreme.
Cassini’s drawings of Saturn
3. The first astronomers thought the rings were moons.
When Galileo first turned his rudimentary telescope on Saturn in 1610, he could see Saturn and its rings, but he didn’t know what he was looking at. He though that the rings might actually be two large moons stuck to either side of Saturn – ears maybe?
It wasn’t until 1655 that the Dutch astronomer Christian Huygens used a better telescope to observe Saturn. He had the resolution to realize that the moons on either side of Saturn were actually rings: “a thin, flat ring, nowhere touching, and inclined to the ecliptic.” Huygens was also the first person to discover Saturn’s largest moon, Titan.
Voyager 2. Credit: NASA
4. Saturn has only been visited 4 times by spacecraft
Only 4 spacecraft sent from Earth have ever visited Saturn, and three of these were just brief flybys. The first was Pioneer 11, in 1979, which flew within 20,000 km of Saturn. Next came Voyager 1 in 1980, and then Voyager 2 in 1981. It wasn’t until Cassini’s arrival in 2004 that a spacecraft actually went into orbit around Saturn and captured photographs of the planet and its rings and moons.
Unfortunately, there are no future plans to send any more spacecraft to Saturn. A few missions have been proposed, including such radical concepts as a sailboat that could traverse the liquid methane lakes on Titan.
5. Saturn has 62 moons
Jupiter has 67 discovered moons, but Saturn is a close second with 62. Some of these are large, like Titan, the second largest moon in the Solar System. But most are tiny – just a few km across, and they have no official names. In fact, the last few were discovered by NASA’s Cassini orbiter just a few years ago. More will probably be discovered in the coming years.
6. The length of a day on Saturn was a mystery until recently
Determining the rotation speed of Saturn was actually very difficult to do, because the planet doesn’t have a solid surface. Unlike Mercury, you can’t just watch to see how long it takes for a specific crater to rotate back into view; astronomers needed to come up with a clever solution: the magnetic field.
To determine the rotational speed of Saturn, astronomers had to measure the rotation of the planet’s magnetic field. By one measurement, Saturn takes 10 hours and 14 minutes to turn on its orbit, but when Cassini approached Saturn, it clocked the rotation at 10 hours and 45 minutes. Astronomers now agree on an average day of 10 hours, 32 minutes and 35 seconds.
Saturn. NASA/JPL/Caltech
7. Saturn’s rings could be old, or they could be young.
It’s possible that Saturn’s rings have been around since the beginning of the Solar System – around 4.54 billion years ago. Or maybe they’re relatively brand new compared to the age of Saturn. Astronomers still don’t fully understand the origin of Saturn’s rings.
They might have formed recently, when a 300-km ice moon was torn apart by Saturn’s gravity, forming a ring around the planet.
It’s also possible that they’re the left over material when Saturn formed in the solar nebula. The material in the rings might have gotten jostled by Saturn’s gravity, and never could pull together into a cohesive Moon.
But astronomers have also found that the ring material looks just too clean to have formed so long ago, and could be as young as 100 million years old. It’s all just a big mystery.
Credit: NASA/JPL-Caltech/Space Science Institute
8. Sometimes the rings disappear
Well, they don’t actually disappear, but they look like they’re going away. Saturn’s axis is tilted, just like Earth. From our point of view, we see Saturn’s changing position as it takes its 30 year journey around the Sun. Sometimes, the rings are fully open, and we see them in all their glory, but other times we see the rings edge on – it looks like they’ve disappeared. This happened in 2008-2009, and will happen again in 2024-2025.
9. You can see Saturn with your own eyes
Saturn appears as one of the 5 planets visible with the unaided eye. If Saturn is in the sky at night, you can head outside and see it. To see the rings and the ball of the planet itself, you’ll want to peer through a telescope. But you can amaze your friends and family by pointing out that bright star in the sky, and let them know they’re looking at Saturn.
10. There could be life near Saturn
Not life on Saturn; the planet is way too hostile to support life. But there could be life on one of Saturn’s moons: Enceladus.
Water vapour geysers on Enceladus. Credit: NASA/JPL
NASA’s Cassini spacecraft recently discovered ice geysers blasting out of Enceladus’ southern pole. This means that some process is keep the moon warm enough that water can remain a liquid underneath the surface. And wherever we find liquid water on Earth, we find life.
Canadian Space Agency employees welcomed astronaut Chris Hadfield as he walked in the building. Credit: Canadian Space Agency.
In a somewhat surprise announcement, Canadian astronaut — and social media icon — Chris Hadfield announced his retirement from the astronaut corps, just weeks after he returned home from his highly successful expedition to the International Space Station.
The wildly popular Hadfield made the announcement at the Canadian Space Agency headquarters near Montreal on Monday. He had called a press conference there to share highlights from his five-month mission, but also announced his retirement as well as his plans to return to live in Canada after spending much of his 21-year astronaut career at Johnson Space Center in Houston or Star City in Russia.
“I’m making good on a promise I made my wife nearly 30 years ago — that yes, eventually, we would be moving back to Canada,” Hadfield said during the press conference.
In posting the above image on Twitter, he said that saying “goodbye to these good people today was much harder than I expected.”
The 53-year-old Hadfield sent a nearly constant stream of magnificent images, informative videos and ebullient Tweets during his pre-flight training and his Expedition 34/35, as well as hosting numerous interviews and educational events with school groups via webcasts from the ISS. With over a million followers on Twitter, his words were read – and widely retweeted — by people around the world.
“I am extremely proud to have shared my experience,” Hadfield said in a statement from the CSA. “I will continue to reinforce the importance of space exploration through public speaking and will continue to visit Canadian schools through the CSA.”
“Chris Hadfield made space exploration history by becoming the first Canadian to command the International Space Station, a feat that instilled pride from coast-to-coast-to-coast,” said Candian Parliamentary Secretary Chris Alexander. “His efforts have affirmed our country’s world-renowned space expertise. I would like to personally thank Chris for his commitment to bringing the spirit of discovery not only to all Canadians, but to the world.”
A rocky region of Portinho da Arrábida, Portugal, with the center of Milky Way behind it, visible at dawn. Credit and copyright: Miguel Claro
Ever seen the arc of the Milky Way in daylight? Astrophotographer Miguel Claro came as close as possible by capturing this view of ‘Via Lactea’ at dawn on May 11, 2013, with the stars of Saggitarius and Scorpius clearly visible, while the sky is slowly turning blue. The image was taken with a rocky region of the resort area of Portinho da Arrábida, in Portugal, visible in the foreground. Also visible is the Red Supergiant star Antares.
Want to get your astrophoto featured on Universe Today? Join our Flickr group or send us your images by email (this means you’re giving us permission to post them). Please explain what’s in the picture, when you took it, the equipment you used, etc.
The season for noctilucent “night-shining” clouds is arriving in the northern hemisphere, when wispy, glowing tendrils of high-altitude ice crystals may be seen around the upper latitudes, shining long after the Sun has set. Found about 83 km (51 miles) up, noctilucent clouds (also called polar mesospheric clouds) are the highest cloud formations in the atmosphere. They’ve been associated with rocket launches and space shuttle re-entries and are now thought to also be associated with meteor activity… and for some reason, this year they showed up a week early.
Noctilucent clouds (NLCs) form between 76 to 85 kilometers (47 to 53 miles) above Earth’s surface when there is just enough water vapor to freeze into ice crystals. The icy clouds are illuminated by the Sun when it is just below the horizon, after darkness has fallen, giving them their night-shining properties. This year NASA’s AIM spacecraft, which is orbiting Earth on a mission to study high-altitude ice, started seeing noctilucent clouds on May 13th.
AIM map of noctilucent clouds over the north pole on June 8 (Credit: LASP/University of Colorado)
“The 2013 season is remarkable because it started in the northern hemisphere a week earlier than any other season that AIM has observed,” reports Cora Randall of the Laboratory for Atmospheric and Space Physics at the University of Colorado. “This is quite possibly earlier than ever before.”
The early start is extra-puzzling because of the solar cycle. Researchers have long known that NLCs tend to peak during solar minimum and bottom-out during solar maximum — a fairly strong anti-correlation. “If anything, we would have expected a later start this year because the solar cycle is near its maximum,” Randall says. “So much for expectations.”
Read more on the NASA AIM page here, and watch the Science@NASA video below for the full story. (Also, check out some very nice NLC photos taken last week in the UK by Stuart Atkinson at Cumbrian Sky.)
Looking west at sunset from latitude 30 degrees north. The ecliptic and Mercury's orbit along with a 10 degree field of view outlined for reference. All graphics created by the author using Starry Night).
If you’ve never seen Mercury, this week is a great time to try.
Over the past few weeks, observers worldwide have been following the outstanding tight triple conjunction of Mercury, Venus and Jupiter low to the west at dusk.
Jupiter has exited the evening sky, headed for conjunction with the Sun on June 19th. I caught what was probably our last glimpse of Jupiter for the season clinging to the murky horizon through binoculars just last week. If you’re “Jonesin’ for Jove,” you can follow its progress this week through superior conjunction as it transits the Solar Heliospheric Observatory’s LASCO C3 camera.
This leaves the two innermost worlds of our fair solar system visible low to the west at dusk. And tonight, they’re joined by a very slender waxing crescent Moon, just over two days after New phase.
The Moon, Venus and Mercury as seen from 30 degrees north tonight at 9PM EDT.
The evening of June 10th finds a 4% illuminated Moon passing just over 5 degrees (about 10 Full Moon diameters) south of Venus and Mercury. Venus will be the first to appear as the sky darkens, shining at magnitude -3.9 and Mercury will shine about 40 times fainter above it at magnitude +0.3.
Ashen light, also known as Earthshine will also be apparent on the darkened limb of the Moon. Another old-time term for this phenomenon is “the Old Moon in the New Moon’s Arms.” Ashen light is caused by sunlight being reflected off of the Earth and illuminating the nighttime Earthward facing portion of the Moon. Just how prominent this effect appears can vary depending on the total amount of cloud cover on the Earth’s Moonward facing side.
….and the orientation of the Moon, Mercury and Venus on the night of June 12th and ~9PM EDT.
This week sets the stage for the best dusk apparition of Mercury for northern hemisphere viewers in 2013. Orbiting the Sun every 88 Earth days, we see Mercury either favorably placed east of the Sun in the dusk sky or west of the Sun in the dawn sky roughly six times a year. Mercury’s orbit is markedly elliptical, and thus not all apparitions are created the same. An elongation near perihelion, when Mercury is 46 million kilometers from the Sun, can mean its only 17.9 degrees away from the Sun as viewed from the Earth. An elongation near aphelion, 69.8 million kilometers distant, has a maximum angular separation of 27.8 degrees.
This week’s greatest elongation of 24.3 degrees occurs on June 12th. It’s not the most extreme value for 2013, but does have another factor going for it; the angle of the ecliptic. As we approach the solstice of June 21st, the plane of the solar system as traced out by the orbit of the Earth is at a favorable angle relative to the horizon. Thus, an observer from 35 degrees north latitude sees Mercury 18.4 degrees above the horizon at sunset, while an observer at a similar latitude in the southern hemisphere only sees it slightly lower at 16.9 degrees.
Venus and the Moon make great guides to locate Mercury over the next few nights. It’s said that Copernicus himself never saw Mercury with his own eyes, though this oft repeated tale is probably apocryphal.
We also get a shot at a skewed “emoticon conjunction” tonight, not quite a “smiley face” (: as occurred between Jupiter, Venus and the Moon in 2008, but more of a “? :” Stick around until February 13th, 2056 and you’ll see a much tighter version of the same thing! A time exposure of a pass of the International Space Station placed near Mercury and Venus could result in a planetary “meh” conjunction akin to a “/:” Hey, just throwing that obscure challenge out there. Sure, there’s no scientific value to such alignments, except as testimony that the universe may just have a skewed sense of humor…
Through the telescope, Venus currently shows a 10” diameter gibbous phase, while Mercury is only slightly smaller at 8” and is just under half illuminated. No detail can be discerned on either world, as a backyard telescope will give you the same blank view of both worlds that vexed astronomers for centuries. These worlds had to await the dawn of the space age to give up their secrets. NASA’s MESSENGER spacecraft entered a permanent orbit around Mercury in 2011, and continues to return some outstanding science.
Both planets are catching up to us from the far side of their orbits. Mercury will pass within 2 degrees of Venus on June 20th, making for a fine wide field view in binoculars.
And now for the wow factor of what you’re seeing tonight. The Moon just passed apogee on June 9th and is currently about 416,500 kilometers or just over one light second distant. Mercury meanwhile, is 0.86 astronomical units (A.U.), or almost 133 million kilometers, or about 7 light minutes away. Finally, Venus is currently farther away from the Earth than the Sun at 1.59 A.U.s, or about 13.7 light minutes distant.
All this makes for a great show in the dusk skies this week. And yes, lunar apogee just after New sets us up for the closest Full Moon of 2013 (aka the internet sensation known as the “Super Moon”) on June 23rd. More to come on that soon!
The rare and rarely heard of meteor shower called the Gamma Delphinids will appear to radiate from the constellation Delphinus (del-FINE-us) the Dolphin high in the southern sky shortly before dawn tomorrow morning June 11. This map shows the sky facing south at 3:30 a.m. local time. Delphinus is near the bottom of the bright 3-star figure the Summer Triangle. Stellarium
Back on June 11, 1930 three members of the American Meteor Society (AMS) in Maryland saw a half-hour-long bright outburst of meteors from the little constellation Delphinus the Dolphin. No one had predicted the shower, but it came out of nowhere and hasn’t been seen since. Attempts to catch a repeat performance in subsequent years met with no success.
That may change tomorrow morning, June 11, 2013. Peter Jenniskins, research scientist with the SETI Institute and NASA Ames Research Center, has examined dust outbursts from long-period comets and suggests the Gamma Delphinids may return for a brief moment of splendor, as Earth passes through this stream of cometary debris not seen since 1930.
Bright meteors photographed in Ohio during the Eta Aquarid meteor shower in 2012. The Gamma Delphinids may send similar bright meteors our way tomorrow morning. Credit: John Chumack
The expected time of maximum activity is 4:30 a.m. Eastern Daylight Time, 3:30 a.m. Central, 2:30 a.m. Mountain and 1:30 a.m. Pacific. These times are ideal for the Americas where Delphinus is high in southern sky at the peak time. Robert Lunsford of the AMS recommends starting your Gamma Delphinid vigil 2 hours ahead of time in case the shower’s early. If these meteors really do happen, you’ll see them anywhere in the sky, but they’ll all trace back to a point near the star Gamma Delphini in the dolphin’s nose.
The map above shows the worldwide possible visibility for the gamma Delphinid shower. Visibility will be best in the bright green areas, which have the highest radiant elevation. Unshaded areas on the map will not have a view of the shower. Credit: Geert Barentsen, International Meteor Organization
No one knows how strong the shower might be or even the duration though it’s likely to be brief. Time estimate range from one hour to 15 minutes. Lunsford expects bright meteors to appear a minute or two apart. If you’re game, split the difference and set up in a comfy lawn chair facing south an hour before the expected maximum. Should you see any of these rare dolphin tears, consider e-mailing a report to: [email protected]
Tonight June 10-11 from 10 p.m. – 2 a.m. CDT, Dr. Bill Cooke of NASA’s Meteoroid Environment Office will take your questions via live web chat. He’ll offer viewing tips about the shower and include a live Ustream telescope view of the skies over Huntsville, Ala.
If you shoot video or images and want to help improve our understanding of this elusive meteor shower, you can upload them to the Office’s Flickr group and also to Universe Today’s Flickr group. We’ll post images if this meteor shower proves to show up!
The Big Bang Theory: A history of the Universe starting from a singularity and expanding ever since. Credit: grandunificationtheory.com
Observations of the kaboom that built our universe — known as the Big Bang — is better matching up with theory thanks to new work released from one of the twin 33-foot (10-meter) W.M. Keck Observatory telescopes in Hawaii.
For two decades, scientists were puzzled at a lithium isotope discrepancy observed in the oldest stars in our universe, which formed close to the Big Bang’s occurrence about 13.8 billion years ago. Li-6 was about 200 times more than predicted, and there was 3-5 times less Li-7 — if you go by astronomical theory of the Big Bang.
The fresh work, however, showed that these past observations came up with the strange numbers due to lower-quality data that, in its simplifications, created more lithium isotopes detections than are actually present. Keck’s observations found no discrepancy.
Artist’s conception of a metal-poor star. Astronomers modelled a portion of its surface to figure out its abundance of lithium-6, an element that was previously in discrepancy between Big Bang theory and observations of old stars. Credit: Karin Lind, Davide De Martin.
“Understanding the birth of our universe is pivotal for the understanding of the later formation of all its constituents, ourselves included,” stated lead researcher Karin Lind, who was with the Max Planck Institute for Astrophysics in Munich when the work was performed.
“The Big Bang model sets the initial conditions for structure formation and explains our presence in an expanding universe dominated by dark matter and energy,” added Lind, who is now with the University of Cambridge.
To be sure, it is difficult to measure lithium-6 and lithium-7 because their spectroscopic “signatures” are pretty hard to see. It takes a large telescope to be able to do it. Also, modelling the data can lead to accidental detections of lithium because some of the processes within these old stars appear similar to a lithium signature.
Keck used a high-resolution spectrometer to get the images and gazed at each star for several hours to ensure astronomers got all the photons it needed to do analysis. Modelling the data took several more weeks of work on a supercomputer.
M31 and M33 are two of the nearest spiral galaxies, and can form the basis for determining distances to more remote spiral galaxies and constraining the expansion rate of the Universe (the Hubble constant). Hence the relevance and importance of several new studies that employed near-infrared data to establish solid distances for M31 (Andromeda) and M33 (Triangulum) (e.g., Gieren et al. 2013), and aimed to reduce existing uncertainties tied to the fundamental parameters for those galaxies. Indeed, reliable distances for M31 and M33 are particularly important in light of the new Hubble constant estimate from the Planck satellite, which is offset relative to certain other results, and that difference hinders efforts to ascertain the nature of dark energy (the mysterious force theorized as causing the Universe’s accelerated expansion).
Gieren et al. remarked that, “a number of new distance determinations to M33 … span a surprisingly large interval … which is a cause of serious concern. As the second-nearest spiral galaxy, an accurate determination of [M33’s] distance is a crucial step in the process of building the cosmic distance ladder.” Concerning M31, Riess et al. 2012 likewise remarked that “M31, the nearest analogue of the Milky Way Galaxy, has long provided important clues to understanding the scale of the Universe.“
The new Gieren and Riess et al. distances are based on near-infrared observations, which are pertinent because radiation from that part of the electromagnetic spectrum is less sensitive than optical data to absorption by dust located along our sight-line (see the figure below). Properly accounting for the impact of dust is a principal problem in cosmic distance scale work, since it causes targets to appear dimmer. “different assumptions about [dust obscuration] are a prime source for the discrepancies among the various distance determinations for M33.” noted Gieren et al., and the same is true for the distance to M31 (see Riess et al.).
Optical and near-infrared images highlight how dust obscures light emitted from targets along the sight-line, and that the level of obscuration is wavelength dependent. New distances established for M31 and M33 are based on near-infrared observations, which are less sensitive to that obscuration (image credit: Alves et al. 2001).
The Gieren and Riess et al. distances to M33 and M31, respectively, were inferred from observations of Cepheids. Cepheids are a class of variable stars that exhibit periodic brightness variations (they pulsate radially). Cepheids can be used as distance indicators because their pulsation period and mean luminosity are correlated. That relationship was discovered by Henrietta Leavitt in the early 1900s. A pseudo period-luminosity relation derived for M31 Cepheids is presented below.
Gieren et al. observed 26 Cepheids in M33 and established a distance of ~2,740,000 lightyears. The team added that, “As the first modern near-infraredCepheid study [of] M33 since … some 30 years … we consider this work as long overdue …” Astronomers often cite distances to objects in lightyears, which defines the time required for light emitted from the source to reach the observer. Despite the (finite) speed of light being 300,000,000 m/s, the rays must traverse “astronomical” distances. Gazing into space affords one the unique opportunity to peer back in time.
A relation exists between a Cepheid’s periodic brightness variations and its mean luminosity. Astronomers use that trend, which was discovered in the early 1900s by Henrietta Leavitt, to establish distances to galaxies hosting Cepheids. In the above figure the horizontal axis features the pulsation period, and the vertical axis defines a proxy for luminosity (image credit: Fig 2 from Riess et al., arXiv/ApJ).
The distances to M33 shown below convey seminal points in the evolution of humanity’s knowledge. The scatter near the 1920s stems partly from a debate concerning whether the Milky Way and the Universe are synonymous. In other words, do galaxies exist beyond the Milky Way? The topic is immortalized in the famed great debate (1920) featuring H. Shapley and H. Curtis (the latter argued for an extragalactic scale). The offset between the pre-1930 and post-1980 data result in part from a nearly two-fold increase in the cosmic distance scale recognized circa 1950 (see also Feast 2000). Also evident is the scatter associated with the post-1980 distances, which merely reinforces the importance of the new high-precision distance estimates.
Riess et al. obtained data for some 70 Cepheids and determined a distance for M31 of ~2,450,000 lightyears. The latter is corroborated by a new study by Contreras Ramos et al. 2013 (d~2,540,000 ly), whose distance estimate relied on data for stars in a M31 globular cluster.
A subset of the distances deduced for M33, as compiled from estimates featured in the NASA/IPAC Extragalactic Database (Steer & Madore). On the vertical axis is the distance to the galaxy in units of lightyears, and the year is cited on the horizontal axis. The red arrow and black datum indicate the new near-infrared based distance from Gieren et al. (image credit: DM).
Gieren et al. used the 8.2-m Very Large Telescope (Yepun) to image stars in M33, and deduce the distance to that galaxy (image credit: G. Hüdepohl/ESO).
