Elusive sprite lightning captured from an airplane above Boulder, Colorado as part of a sprite observing campaign. Credit and copyright: Jason Ahrns.
Mysterious red sprite lightning is intriguing: sprites occur only at high altitudes above thunderstorms, only last for a thousandth of a second and emit light in the red portion of the visible spectrum. Therefore, studying sprites has been notoriously difficult for atmospheric scientists. Astrophotographer Jason Ahrns has had the chance to be part of a sprite observing campaign, and with a special airplane from the National Center for Atmospheric Research’s Research Aircraft Facility in Boulder, Colorado, has been on flights to try and observe red sprite lightning from the air.
Jason had some success on a recent flight, and was able to capture a sprite (above) on high speed film. Below you can see a movie of it at 10,000 frames per second:
Pretty amazing!
Scientists say that while sprites have likely occurred on Earth for millions of years, they were first discovered and documented only by accident in 1989 when a researcher studying stars was calibrating a camera pointed at the distant atmosphere where sprites occur.
Sprites usually appear as several clusters of red tendrils above a lighting flash followed by a breakup into smaller streaks. The brightest region of a sprite is typically seen at altitudes of 65-75 km (40-45 miles), but often as high as 90 km (55 miles) into the atmosphere.
Some of the latest research shows that only a specific type of lightning is the trigger that initiates sprites aloft.
You can read more (and see more images) about Jason’s experiences with sprites at his website.
A wintertime rising gibbous Moon. (Image credit: Art Explosion).
A team from the University of Birmingham recently announced an astronomical discovery in Scotland marking the beginnings of recorded time.
Announced last month in the Journal of Internet Archaeology, the Mesolithic monument consists of a series of pits near Aberdeenshire, Scotland. Estimated to date from 8,000 B.C., this 10,000 year old structure would pre-date calendars discovered in the Fertile Crescent region of the Middle East by over 5,000 years.
Originally unearthed by the National Trust for Scotland in 2004, the site is designated as Warren Field near the town of Crathes. It consists of 12 pits in an arc 54 metres long that seem to correspond with 12 lunar months, plus an added correction to bring the calendar back into sync with the solar year on the date of the winter solstice.
A diagram of the Warren Field site, showing the 12 pits (below) and the alignment with the phases of the Moon plus the rising of the winter solstice Sun. Note: the scale should read “0-10 metres.” (Credit: The University of Birmingham).
“The evidence suggests that hunter-gatherer societies in Scotland had both the need and sophistication to track time across the years, to correct for seasonal drift of the lunar year” said team leader and professor of Landscape Archaeology at the University of Birmingham Vince Gaffney.
We talked last week about the necessity of timekeeping as cultures moved from a hunter-gatherer to agrarian lifestyle. Such abilities as marking the passage of the lunar cycles or the heliacal rising of the star Sirius gave cultures the edge needed to dominate in their day.
For context, the pyramids on the plains of Giza date from around 2500 B.C., The Ice Man on display in Bolzano Italy dates from 3,300 B.C., and the end of the last Ice Age was around 20,000 to 10,000 years ago, about the time that the calendar was constructed.
“We have been taking photographs of the Scottish landscape for nearly 40 years, recording thousands of archaeological sites that would never have been detected from the ground,” said manager of Aerial projects of the Royal Commission of Aerial Survey Projects Dave Cowley. “It’s remarkable to think that our aerial survey may have helped to find the place where time was invented.”
The site at Warren Field was initially discovered during an aerial survey of the region.
Vince Gaffney, professor of Landscape and Archaeology at University of Birmingham in Warren Field, Crathes, Aberdeenshire where the discovery was made. (Credit: The University of Birmingham).
The use of such a complex calendar by an ancient society also came as a revelation to researchers. Emeritus Professor of Archaeoastronomy at the University of Leicester Clive Ruggles notes that the site “represents a combination of several different cycles which can be used to track time symbolically and practically.”
The lunar synodic period, or the span of time that it takes for the Moon to return to the same phase (i.e., New-to-New, Full-to-Full, etc) is approximately 29.5 days. Many cultures used a strictly lunar-based calendar composed of 12 synodic months. The Islamic calendar is an example of this sort of timekeeping still in use today.
However, a 12 month lunar calendar also falls out of sync with our modern Gregorian calendar by 11 days (12 on leap years) per year.
The familiar Gregorian calendar is at the other extreme, a calendar that is strictly solar-based. The Gregorian calendar was introduced in 1582 and is still in use today. This reconciled the 11 minute per year difference between the Julian calendar and the mean solar year, which by the time of Pope Gregory’s reform had already caused the calendar to “drift” by 10 days since the 1st Council of Nicaea 325 AD.
Artist’s conception of the Warren Field site during the winter solstice. (Credit: The University of Birmingham). Credit: The University of Birmingham
Surprisingly, the calendar discovered at Warren Field may be of a third and more complex variety, a luni-solar calendar. This employs the use of intercalary periods, also known as embolismic months to bring the lunar and solar calendar back into sync.
The modern Jewish calendar is an example of a luni-solar hybrid, which adds an extra month (known as the 2nd Adar or Adar Sheni) every 2-3 years. This will next occur in March 2014.
The Greek astronomer Meton of Athens noted in 5th century B.C. that 235 synodic periods very nearly add up to 19 years, to within a few hours. Today, this period bears his name, and is known as a metonic cycle. The Babylonian astronomers were aware of this as well, and with the discovery at Warren Field, it seems that ancient astronomers in Scotland may have been moving in this direction of advanced understanding as well.
It’s interesting to note that the site at Warren Field also predates Stonehenge, the most famous ancient structure in the United Kingdom by about 6,000 years. 10,000 years ago would have also seen the Earth’s rotational north celestial pole pointed near the +3.9th magnitude star Rukbalgethi Shemali (Tau Herculis) in the modern day constellation of Hercules. This is due to the 26,000 year wobble of our planet’s axis known as the precession of the equinoxes.
The precession of the north celestial pole over millennia. (Credit: Wikimedia Commons graphic under a Creative Commons Attribution 2.5 Generic license. Author: Tau’olunga).
The Full Moon nearest the winter solstice also marks the “Long Nights Moon,” when the Full Moon occupies a space where the Sun resides during the summer months and rides high above the horizon for northern observers all night. The ancients knew of the five degree tilt that our Moon has in relation to the ecliptic and how it can ride exceptionally high in the sky every 18.6 years. We’re currently headed towards a ‘shallow year’ in 2015, where the Moon rides low in relation to the ecliptic. From there, the Moon’s path in the sky will get progressively higher each year, peaking again in 2024.
Who built the Warren Field ruins along the scenic Dee Valley of Scotland? What other surprises are in store as researchers excavate the site? One thing is for certain: the ancients were astute students of the sky. It’s fascinating to realize how much of our own history has yet to be told!
Why don’t we have insects the size of horses? Why do bubbles form spheres? Why does it take so much energy to broadcast to every star? Let’s take a look at some non-linear mathematical relationships and see how they impact your day-to-day life.
And the podcast is also available as a video, as Fraser and Pamela now record Astronomy Cast as part of a Google+ Hangout (usually recorded every Monday at 3 pm Eastern Time):
The magnetic flux of the Sun through the solar cycle (credit: Ian O'Neill)
The Sun’s magnetic field will likely reverse sometime in the next three to four months. No, this is not the next doomsday prediction scenario. It really will happen. But there’s nothing to fear because in reality the Sun’s magnetic field changes regularly, about every 11 years.
The flip-flopping of the Sun’s magnetic field takes place at the peak of each solar activity cycle when the Sun’s internal magnetic dynamo reorients itself. When the field reversal happens, the magnetic field weakens, then dies down to zero before emerging again with a reversed polarity.
While this is not a catastrophic event, the reversal will have effects, said solar physicist Todd Hoeksema, the director of Stanford University’s Wilcox Solar Observatory, who monitors the Sun’s polar magnetic fields. “This change will have ripple effects throughout the Solar System,” he said.
When solar physicists talk about solar field reversals, their conversation often centers on the “current sheet.” The current sheet is a sprawling surface jutting outward from the sun’s equator where the Sun’s slowly-rotating magnetic field induces an electrical current. The current itself is small, only one ten-billionth of an amp per square meter (0.0000000001 amps/m2), but there’s a lot of it: the amperage flows through a region 10,000 km thick and billions of kilometers wide. Electrically speaking, the entire heliosphere is organized around this enormous sheet.
During field reversals, the current sheet becomes very wavy, and as Earth orbits the Sun, we dip in and out of the current sheet. This means we can see an uptick in space weather, with any solar storms affecting Earth more. So, there may be more auroras in our near future.
Cosmic rays are also affected. These are high-energy particles accelerated to nearly light speed by supernova explosions and other violent events in the galaxy. Cosmic rays are a danger to astronauts and space probes, and some researchers say they might affect the cloudiness and climate of Earth. The current sheet acts as a barrier to cosmic rays, deflecting them as they attempt to penetrate the inner solar system. The good news is that a wavy sheet acts as a better shield against these energetic particles from deep space.
Scientists say the Sun’s north pole is already quite far along losing its polarity, with the south pole coming along behind.
“The sun’s north pole has already changed sign, while the south pole is racing to catch up,” said Phil Scherrer, another solar physicst at Standford. “Soon, however, both poles will be reversed, and the second half of Solar Max will be underway.”
Curiosity accomplished Historic 1st drilling into Martian rock at John Klein outcrop on Feb 8, 2013 (Sol 182), shown in this context mosaic view of the Yellowknife Bay basin taken on Jan. 26 (Sol 169). The robotic arm is pressing down on the surface at John Klein outcrop of veined hydrated minerals – dramatically back dropped with her ultimate destination; Mount Sharp. Credit: NASA/JPL-Caltech/Ken Kremer/Marco Di Lorenzo
NASA and the Jet Propulsion Laboratory are hosting a live webcast on Tuesday, August 6 starting at 14:45 UTC (10:45 a.m. EDT) to celebrate the one year anniversary of the Curiosity rover landing on Mars. Update: We’ve now inserted the replay from NASA TV, and it’s a great recap of the excitement of landing and the discoveries of past year, and you’ll hear from all the major science and engineering names from the MSL mission.
You can ask questions for the team on Twitter and G+ during the broadcast, just use #AskNASA to pose your question.
Curiosity team members will share remembrances about the dramatic landing night and the overall mission. Immediately following that program, NASA will carry a live public event from NASA Headquarters in Washington. That event will feature NASA officials and crew members aboard the International Space Station as they observe the rover anniversary and discuss how its activities and other robotic projects are helping prepare for a human mission to Mars and an asteroid.
Also, below, is the replay of events held at NASA HQ to celebrate the anniversary:
The Moon rises surrounded by noctilucent clouds, as seen from the International Space Station. Credit: NASA/ASI/ESA. Via Luca Parmitano on Twitter.
Recently, Italian astronaut Luca Parmitano spent a “night flight” in the Cupola of the International Space Station in hopes of capturing night-time images of his home country from space. But he saw so much more, including this incredible image of the crescent Moon rising among bright blue noctilucent clouds. These wispy and mysterious clouds appear in Earth’s mesosphere — a region extending from 30 to 53 miles (48-85 km) high in the atmosphere — at twilight, usually in early summer. They can be seen from Earth’s northern hemisphere and, obviously, are visible from space too.
You can read about Parmitano’s night flight and see more of the images he took at his Volare blog. At the close of his image-taking night flight he says, “It’s late, and tomorrow will be a long day. With those lights still filling my eyes, I slowly close the seven windows and cross the Station to return to my sleeping pod. Not even dreams could replace the beautiful reality that revolves, oblivious, beneath us.”
Opportunity rover’s 1st mountain climbing goal is dead ahead in this up close view of Solander Point along the eroded rim of Endeavour Crater. Opportunity will soon ascend the mountain in search of minerals signatures indicative of a past Martian habitable environment. This navcam panoramic mosaic was assembled from raw images taken on Sol 3385 (Aug 2, 2013). Credit: NASA/JPL/Cornell/Marco Di Lorenzo/Ken Kremer (kenkremer.com)
Opportunity rover’s 1st mountain climbing goal is dead ahead in this up close view of Solander Point at Endeavour Crater. Opportunity will ascend the mountain looking for clues indicative of a Martian habitable environment. This navcam panoramic mosaic was assembled from raw images taken on Sol 3385 (Aug 2, 2013).
Credit: NASA/JPL/Cornell/Marco Di Lorenzo/Ken Kremer (kenkremer.com)[/caption]
NASA’s most powerful Mars orbiter has been given the green light today (Aug. 5) to capture new high resolution spectral scans that are absolutely crucial for directing the long lived Opportunity rover’s hunt for signatures of habitability atop the intriguing mountain she will soon ascend.
In a plan only recently approved by NASA, engineers are aiming the CRISM mineral mapping spectrometer aboard the Mars Reconnaissance Orbiter (MRO) circling overhead to collect high resolution survey scans of Solander Point – Opportunity’s 1st mountain climbing goal along the rim of huge Endeavour Crater.
“New CRISM observations centered over Solander Point will be acquired on Aug. 5, 2013,” Ray Arvidson told Universe Today exclusively. Arvidson is the mission’s deputy principal scientific investigator from Washington University in St. Louis, Mo.
NASA’s decade old rover Opportunity is about to make ‘landfall’ at the base of Solander Point, the Martian mountain she will scale in search of the chemical ingredients that could sustain Martian microbes.
So the new spectral data can’t come back to Earth soon enough.
Currently, the science team lacks the same quality of high resolution CRISM data from Solander Point that they had at a prior stop at Cape York. And that data was crucial because it allowed the rover to be precisely targeted – and thereby discover a habitable zone, Arvidson told me.
“CRISM collected lots of overlapping measurements at Cape York to sharpen the image resolution to 5 meters per pixel to find the phyllosilicate smectite [clay minerals] signatures at Matejivic Hill on Cape York.”
“We don’t have that at Solander Point. We only have 18 meters per pixel data. And at that resolution you can’t tell if the phyllosilicate smectite [clay minerals] outcrops are present.”
Today’s new survey from Mars orbit will vastly improve the spectral resolution – from 18 meters per pixel down to 5 meters per pixel.
“5 meter per pixel CRISM resolution is expected in the along-track direction over Solander Point by commanding the gimbaled optical system to oversample that much,” Arvidson explained.
Opportunity rover’s view from very near the foothills of Solander Point looking along the rim and vast expanse of Endeavour Crater. Solander Point is the 1st Martian Mountain NASA’s Opportunity will climb and the rovers next destination. Solander Point may harbor clay minerals indicative of a past Martian habitable environment. This navcam mosaic was assembled from raw images taken on Sol 3374 (July 21, 2013). Credit: NASA/JPL/Cornell/Marco Di Lorenzo/Ken Kremer (kenkremer.com)
The new CRISM spectral survey from Mars is essential to enable the science team to carefully study the alien, unexplored terrain in detail and locate the clay minerals and other water bearing minerals, even before the rover arrives.
Clay minerals form in neutral pH water conducive to life.
Opportunity would then be commanded to drive to preselected sites to conduct “ground truth” forays at Solander.
That’s just like was done at Cape York and the “Esperance” rock loaded with clay minerals that turned into one of the “Top 5 discoveries of the mission” according to Arvidson and Steve Squyres, Opportunity’s Science Principal Investigator of Cornell.
But it took some cajoling and inter team negotiations to convince everyone to move forward with the special but crucial CRISM imaging plan.
Since MRO is getting on in age – it launched in 2005 – NASA and the spacecraft managers have to carefully consider special requests such as this one which involves slewing the MRO spacecraft instruments and therefore entails some health risks to the vehicle.
“CRISM has been operating at Mars since 2006 and sometimes the optics on a gimble have actuators that get stuck a little bit and don’t sweep as fully as planned.”
Nevertheless, Arvidson told me a few weeks ago he was hopeful to get approval.
“I suspect I can talk the team into it.”
And eventually he did! And informed me for the readers of Universe Today.
The fact that the Opportunity scientists already scored a ‘Science Home Run’ with their prior CRISM targeting request at Cape York certainly aided their cause immensely.
The new approved CRISM measurements due to be captured today will give Opportunity the best chance to be targeted to the most promising mineral outcrops, and as quickly as possible.
“With the coordinated observations from CRISM and Opportunity we will go into Solander Point a lot smarter!”
“And we’ll have a pretty good idea of what to look for and where,” Arvidson told me.
Opportunity snap up close view of the base of Solander Point and mountain slopes she will ascend soon. This hi res pancam camera mosaic was assembled from raw images taken on Sol 3385 (Aug 2, 2013). Credit: NASA/JPL/Cornell/ASU/Marco Di Lorenzo/Ken Kremer (kenkremer.com)
Today marks Opportunity’s 3389th Sol or Martian day roving Mars. Merely 90 days were expected!
Having completed her investigation of the rocky crater plains, the rover continues to drive south.
Any day now Opportunity will drive onto the Bench surrounding Solander and start a new phase of the mission.
Since she basically arrived at Solander with plenty of power and ahead of schedule prior to the onset of the 6th Martian winter, the robot has some spare time to investigate the foothills before ascending the north facing slopes.
“We will be examining the bench and then working our way counterclockwise to reach the steep slopes associated with the Noachian outcrops that are part of the Endeavour rim,” Arvidson said.
Ken Kremer Opportunity rover location in the latest MRO/HiRISE color image. The green line shows more or less the route we hope to take to the base of Solander point. Since it is only a couple of hundred meters away, we could be there is a couple of drives. Maybe by the end of next week. The label say “3374” but this is also roughly the location through 3379. Credit: NASA/JPL/Larry Crumpler
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 3387 Sols, or Martian days, since landing inside Eagle Crater on Jan 24, 2004 to current location near foothills of Solander Point at the western rim of Endeavour Crater. Opportunity discovered clay minerals at Esperance – indicative of a habitable zone. Credit: NASA/JPL/Cornell/ASU/Marco Di Lorenzo/Ken Kremer
When tiny grains of dust impact our atmosphere, they leave a trail of glowing material, like a streak of light across the sky.
This is a meteor, or a shooting star.
On any night, you can go outside, watch the sky, and be guaranteed to see one. Individual meteors start as meteoroids – pieces of rock smaller than a pebble flying around the Solar System.
Even though they’re tiny, these objects can be moving at tens of thousands of kilometers per hour. When they hit Earth’s atmosphere, they release tremendous amounts of energy, burning up above an altitude of 50 kilometers.
As they disintegrate, they leave a trail of superheated gas and rocky sparks which last for a moment in the sky, and then cool down and disappear from view.
Throughout the year there are several meteor showers, when the number of meteors streaking through the sky increases dramatically. This happens when the Earth passes through the trail of dust left by a comet or asteroid.
Meteor showers are when night sky puts on a special show, and it’s a time to gather your friends and family together and enjoy the spectacle.
Some showers produce only a trickle of objects, while others, like the famous Perseid meteor shower, can dependably bring dozens of meteors each hour.
Meteor Burst – Credit: NASAIf the trail is dense enough, we can get what is called a meteor storm. The most powerful meteor storms in history truly made it look like the sky was falling. The Leonids in 1833 produced hundreds of thousands per hour.
Meteor showers take their name from the constellation from where they appear to originate. For example, the Perseids trace a trail back to the constellation Perseus; although you can see them anywhere across the sky.
You can see meteors any time of the year, and you don’t need any special equipment to enjoy an average meteor shower. But here are some ways you can improve your experience.
You’ll want to find a location with as clear a view to the horizon in as many directions as possible. An open field is great. Lie on your back, or on a reclining chair, look up to the sky
… and be patient.
A bright fireball meteor in twilight. The Lyrids, like all meteor showers, offer up the occasional fireball among a mix of fainter meteors. Credit: John ChumackYou probably won’t see a meteor right away, but after a few minutes, you should see your first one.
The longer you look, the more you’ll see, and the better chance you’ll have of seeing a bolide or fireball; a very bright meteor that streaks across the sky, leaving a trail that can last for a long time.
You can see meteors any time that it’s dark, but the most impressive ones happen in the early morning, when your location on Earth is ploughing directly into the space dust.
You also want the darkest skies you can get, far away from city light pollution, and many hours after the Sun has gone down.
Enjoy the early evening meteors, but then set your alarm and get up around 4 in the morning to see the real sky show.
The radiant for the Persieds, looking to the NE from latitide ~30N at around 2AM local. Created by the Author in Starry Night).If I could only see one meteor shower every year, it would have to be the Perseids. These come when the Earth passes through the tail of Comet Swift-Tuttle, and peak around August 12th every year. It’s not always the most active shower, but it’s warm outside in the Northern hemisphere, and this is a fun activity to do with your friends and family.
Remnants of a gamma-ray burst (called GRB 130603B) are visible in these Hubble Space Telescope pictures. Credit: NASA, ESA, and Z. Levay (STScI/AURA)
As astute readers of Universe Today, you likely know what a supernova is: a stellar explosion that signals the end game for certain kinds of stars. Above, however, is a picture of a kilonova, which happens when two really dense objects come together.
This fireball arose after a short-term (1/10 of a second) gamma-ray burst came into view of the Swift space telescope on June 3. Nine days later, the Hubble Space Telescope looked at the same area to see if there were any remnants, and spotted a faint red object that was confirmed in independent observations.
It’s the first time astronomers have been able to see a connection between gamma-ray bursts and kilonovas, although it was predicted before. They’re saying this is the first evidence that short-duration gamma ray bursts arise as two super-dense stellar objects come together.
So what’s the connection? Astronomers suspect it’s this sequence of events:
Two binary neutron stars (really dense stars) start to move closer to each other;
The system sends out gravitational radiation that make ripples in space-time;
These waves make the stars move even closer together;
In the milliseconds before the explosion, the two stars “merge into a death spiral that kicks out highly radioactive material,” as NASA states, with material that gets warmer, gets bigger and sends out light;
The kilonova occurs with the detonation of a white dwarf. While it’s bright, 1,000 times brighter than a nova, it’s only 1/10th to 1/100th the brightness of an average supernova.
An artistic image of the explosion of a star leading to a gamma-ray burst. (Source: FUW/Tentaris/Maciej Fro?ow)
“This observation finally solves the mystery of the origin of short gamma ray bursts,” stated Nial Tanvir of the University of Leicester in the United Kingdom, who is also the lead author.
“Many astronomers, including our group, have already provided a great deal of evidence that long-duration gamma ray bursts (those lasting more than two seconds) are produced by the collapse of extremely massive stars. But we only had weak circumstantial evidence that short bursts were produced by the merger of compact objects. This result now appears to provide definitive proof supporting that scenario.”
