Universe Today

May 12, 2011December 24, 2015 by Jason Major

The Flip Side of Exoplanet Orbits

New research reveals the possible cause of retrograde "hot Jupiters"

[/caption]

It was once thought that our planet was part of a “typical” solar system. Inner rocky worlds, outlying gas giants, some asteroids and comets sprinkled in for good measure. All rotating around a central star in more or less the same direction. Typical.

But after seeing what’s actually out there, it turns out ours may not be so typical after all…

Astronomers researching exoplanetary systems – many discovered with NASA’s Kepler Observatory – have found quite a few containing “hot Jupiters” that orbit their parent star very closely. (A hot Jupiter is the term used for a gas giant – like Jupiter – that resides in an orbit very close to its star, is usually tidally locked, and thus gets very, very hot.) These worlds are like nothing seen in our own solar system…and it’s now known that some actually have retrograde orbits – that is, orbiting their star in the opposite direction.

“That’s really weird, and it’s even weirder because the planet is so close to the star. How can one be spinning one way and the other orbiting exactly the other way? It’s crazy. It so obviously violates our most basic picture of planet and star formation.”

– Frederic A. Rasio, theoretical astrophysicist, Northwestern University

Now retrograde movement does exist in our solar system. Venus rotates in a retrograde direction, so the Sun rises in the west and sets in the east, and a few moons of the outer planets orbit “backwards” relative to the other moons. But none of the planets in our system have retrograde orbits; they all move around the Sun in the same direction that the Sun rotates. This is due to the principle of conservation of angular momentum, whereby the initial motion of the disk of gas that condensed to form our Sun and afterwards the planets is reflected in the current direction of orbital motions. Bottom line: the direction they moved when they were formed is (generally) the direction they move today, 4.6 billion years later. Newtonian physics is okay with this, and so are we. So why are we now finding planets that blatantly flaunt these rules?

The answer may be: peer pressure.

Or, more accurately, powerful tidal forces created by neighboring massive planets and the star itself.

By fine-tuning existing orbital mechanics calculations and creating computer simulations out of them, researchers have been able to show that large gas planets can be affected by a neighboring massive planet in such a way as to have their orbits drastically elongated, sending them spiraling closer in toward their star, making them very hot and, eventually, even flip them around. It’s just basic physics where energy is transferred between objects over time.

It just so happens that the objects in question are huge planets and the time scale is billions of years. Eventually something has to give. In this case it’s orbital direction.

“We had thought our solar system was typical in the universe, but from day one everything has looked weird in the extrasolar planetary systems. That makes us the oddball really. Learning about these other systems provides a context for how special our system is. We certainly seem to live in a special place.”

– Frederic A. Rasio

Yes, it certainly does seem that way.

The research was funded by the National Science Foundation. Details of the discovery are published in the May 12th issue of the journal Nature.

Read the press release here.

Main image credit: Jason Major. Created from SDO (AIA 304) image of the Sun from October 17, 2010 (NASA/SDO and the AIA science team) and an image of Jupiter taken by the Cassini-Huygens spacecraft on October 23, 2000 (NASA/JPL/SSI).

May 11, 2011December 24, 2015 by Nancy Atkinson

Crab Nebula Erupts in a Superflare

NASA's Chandra X-ray Observatory reveals the complex X-ray-emitting central region of the Crab Nebula. This image is 9.8 light-years across. Chandra observations were not compatible with the study of the nebula's X-ray variations. Credit: NASA/CXC/SAO/F. Seward et al.

[/caption]

From a NASA press release:

The famous Crab Nebula supernova remnant has erupted in an enormous flare five times more powerful than any flare previously seen from the object. On April 12, NASA’s Fermi Gamma-ray Space Telescope first detected the outburst, which lasted six days. Several other satellites also made observations, which has astonished astronomers by revealing unexpected changes in X-ray emission the Crab, once thought to be the steadiest high-energy source in the sky.

The nebula is the wreckage of an exploded star that emitted light which reached Earth in the year 1054. It is located 6,500 light-years away in the constellation Taurus. At the heart of an expanding gas cloud lies what is left of the original star’s core, a superdense neutron star that spins 30 times a second. With each rotation, the star swings intense beams of radiation toward Earth, creating the pulsed emission characteristic of spinning neutron stars (also known as pulsars).

Apart from these pulses, astrophysicists believed the Crab Nebula was a virtually constant source of high-energy radiation. But in January, scientists associated with several orbiting observatories, including NASA’s Fermi, Swift and Rossi X-ray Timing Explorer, reported long-term brightness changes at X-ray energies.

X-ray data from NASA's Fermi, RXTE, and Swift satellites and the European Space Agency's International Gamma-Ray Astrophysics Laboratory (INTEGRAL) confirm that the Crab Nebula's output has declined about 7 percent in two years at energies from 15,000 to 50,000 electron volts. They also show that the Crab has brightened or faded by as much as 3.5 percent a year since 1999. Fermi's Large Area Telescope (LAT) has detected powerful gamma-ray flares (magenta lines) as well. (Image credit: NASA's Goddard Space Flight Center)

“The Crab Nebula hosts high-energy variability that we’re only now fully appreciating,” said Rolf Buehler, a member of the Fermi Large Area Telescope (LAT) team at the Kavli Institute for Particle Astrophysics and Cosmology, a facility jointly located at the Department of Energy’s SLAC National Accelerator Laboratory and Stanford University.

Since 2009, Fermi and the Italian Space Agency’s AGILE satellite have detected several short-lived gamma-ray flares at energies greater than 100 million electron volts (eV) — hundreds of times higher than the nebula’s observed X-ray variations. For comparison, visible light has energies between 2 and 3 eV.

On April 12, Fermi’s LAT, and later AGILE, detected a flare that grew about 30 times more energetic than the nebula’s normal gamma-ray output and about five times more powerful than previous outbursts. On April 16, an even brighter flare erupted, but within a couple of days, the unusual activity completely faded out.

“These superflares are the most intense outbursts we’ve seen to date, and they are all extremely puzzling events,” said Alice Harding at NASA’s Goddard Space Flight Center in Greenbelt, Md. “We think they are caused by sudden rearrangements of the magnetic field not far from the neutron star, but exactly where that’s happening remains a mystery.”

The Crab’s high-energy emissions are thought to be the result of physical processes that tap into the neutron star’s rapid spin. Theorists generally agree the flares must arise within about one-third of a light-year from the neutron star, but efforts to locate them more precisely have proven unsuccessful so far.

Since September 2010, NASA’s Chandra X-ray Observatory routinely has monitored the nebula in an effort to identify X-ray emission associated with the outbursts. When Fermi scientists alerted astronomers to the onset of a new flare, Martin Weisskopf and Allyn Tennant at NASA’s Marshall Space Flight Center in Huntsville, Ala., triggered a set of pre-planned observations using Chandra.

It was also observed by NASA’s Rossi X-Ray Timing Explorer (RXTE) and Swift satellites and the European Space Agency’s International Gamma-Ray Astrophysics Laboratory (INTEGRAL). The results confirm a real intensity decline of about 7 percent at energies between 15,000 to 50,000 eV over two years. They also show that the Crab has brightened and faded by as much as 3.5 percent a year since 1999.

“Thanks to the Fermi alert, we were fortunate that our planned observations actually occurred when the flares were brightest in gamma rays,” Weisskopf said. “Despite Chandra’s excellent resolution, we detected no obvious changes in the X-ray structures in the nebula and surrounding the pulsar that could be clearly associated with the flare.”

Scientists think the flares occur as the intense magnetic field near the pulsar undergoes sudden restructuring. Such changes can accelerate particles like electrons to velocities near the speed of light. As these high-speed electrons interact with the magnetic field, they emit gamma rays.

To account for the observed emission, scientists say the electrons must have energies 100 times greater than can be achieved in any particle accelerator on Earth. This makes them the highest-energy electrons known to be associated with any galactic source. Based on the rise and fall of gamma rays during the April outbursts, scientists estimate that the size of the emitting region must be comparable in size to the solar system.

May 11, 2011January 18, 2016 by Nancy Atkinson

NanoSail-D Caught on Video

When you have an automated video camera, it’s amazing what you can pick up in the night sky. Dr. Robert Suggs used the Automated Lunar and Meteor Observatory at Marshall Space Flight Center to catch NanoSail-D on video as it slipped across the sky back on March 2nd, 2011. This video is from the small finder camera for the observatory and the solar sail appears just how it would be seen by the naked eye. The NanoSail-D twitter feed said that this video is actually upside down. “I am actually sailing out of the trees and higher into the night sky,” the solar sail Tweeted. The same facility also captured images of NanoSail-d with 80mm and 14″ telescopes.

NanoSail-D won’t be visible for very much longer, just a couple of weeks or less until it will burn up in the atmosphere. See our previous article on how to observe NanoSail-D before it de-orbits.

Source: NanoSail-D website

May 11, 2011December 24, 2015 by Steve Nerlich

Photopic Sky Survey

[/caption]

The Photopic Sky Survey, the largest true-color all-sky survey – along with a constellation and star name overlay option – is available here.

For more detail on how it was created read on…

Nick Risinger decided to take a little break from work and embark on a 45,000 miles by air and 15,000 by land journey – along with his Dad, brother and a carload of astrophotography gear – to capture the biggest true color picture of the universe ever. As you do…

The requirement for the long journey is all about trying to snap the whole universe from the surface of a rotating planetary body in a solar orbit – and with a tilted axis yet. So what might be seen in the northern hemisphere isn’t always visible from the south. Likewise with the seasons, what may be overhead in the summer is below the horizon in the winter.

On top of that, there are issues of light pollution and weather to contend with – so you can’t just stop anywhere and snap away at the sky. Nonetheless, with a navigational computer to ensure accuracy and over the course of one year – Risinger broke the sky down into 624 areas (each 12 degrees wide) and captured each portion through 60 exposures. Four short, medium, and long shots with each of six cameras were taken to help reduce noise, satellite trails, and other inaccuracies.

Nick Risinger preparing an array of cameras in Colorado to shoot part of the five gigapixel Photopic Sky Survey image. Credit: Risinger/Photopic Sky Survey.

Further reading: Photopic Sky Survey home page (includes a description of the hardware and software used).

May 11, 2011April 13, 2022 by Ken Kremer

Dawn Begins Approach to Asteroid Vesta and Snaps First Images

Dawn's First Glimpse of Vesta – Processed. This image, processed to show the true size of the giant asteroid Vesta, shows Vesta in front of a spectacular background of stars. It was obtained by the framing camera aboard NASA's Dawn spacecraft on May 3, 2011, from a distance of about 1.2 million kilometers (750,000 miles). Since Vesta is so bright that it outshines its starry background, Dawn team members commanded a long exposure time to make the stars visible. They corrected the resulting exaggerated size of Vesta by superimposing a short exposure image of the target asteroid, showing its true size. Vesta is the small, bright pearl in the middle of the image. Image credit: NASA/JPL-Caltech/UCLA/MPS/DLR/IDA

[/caption]

NASA’s revolutionary Dawn Asteroid Orbiter has begun the final approach phase to the giant asteroid Vesta and snapped its first science image. The image was taken on May 3, when Dawn was approximately 1.21 million kilometers (752,000 miles) distant from Vesta using the science imager known as the Framing Camera.

Besides the pure delight of seeing Vesta up close for the first time, the images play a crucial role in navigating Dawn precisely through space and successfully achieve orbit around the protoplanet that nearly formed into a full fledged planet.

Vesta is the second most massive object in the Asteroid Belt and is 530 kilometers (330 miles) in diameter.

Dawn launch on September 27, 2007 by a Delta II rocket from Cape Canaveral Air Force Station, Florida. Credit: Ken Kremer

Dawn should be captured into orbit about Vesta around July 16 as the engineering team works to maneuver the spacecraft to match the asteroids path around the sun using the exotic ion thrusters. Using the background stars in the framing camera images, they will be able to determine Dawn’s location in space relative to the stars in order to precisely navigate the spacecrafts trajectory towards Vesta.

“After plying the seas of space for more than a billion miles, the Dawn team finally spotted its target,” said Carol Raymond, Dawn’s deputy principal investigator at NASA’s Jet Propulsion Laboratory in Pasadena, Calif. “This first image hints of detailed portraits to come from Dawn’s upcoming visit.”

The best images of Vesta to date were taken by the Hubble Space Telescope. Jim Adams, Deputy Director of Planetary Science, told me that the images from Dawn’s Framing Camera will exceed those from Hubble in a few weeks.

Dawn will initially enter a highly elliptical polar orbit around Vesta and start collecting science data in August from an altitude of approximately 1,700 miles (2,700 kilometers). The orbit will be lowered in stages to collect high resolution data as Dawn spends about a year collecting data from its three science instruments.

Dawn's First Glimpse of Vesta -- Unprocessed
This image shows the first, unprocessed image obtained by NASA's Dawn spacecraft of the giant asteroid Vesta in front of a background of stars. It was obtained by Dawn's framing camera on May 3, 2011, from a distance of about 1.2 million kilometers (750,000 miles). Vesta is inside the white glow at the center of the image. The giant asteroid reflects so much sunlight that its size is dramatically exaggerated at this exposure. Image credit: NASA/JPL-Caltech/UCLA/MPS/DLR/IDA

Thereafter Dawn will be targeted to Ceres, the largest object in the Asteroid Belt which it will reach in 2015.

Dawn is an international mission.

The framing cameras have been developed and built under the leadership of the Max Planck Institute for Solar System Research, Katlenburg-Lindau, Germany, with significant contributions by the German Aerospace Center (DLR) Institute of Planetary Research, Berlin, and in coordination with the Institute of Computer and Communication Network Engineering, Braunschweig. The framing camera project is funded by the Max Planck Society, DLR, and NASA.

The Visible and Infrared mapping camera was provided by the Italian Space Agency. The Gamma Ray Detector was supplied by Los Alamos National Labotatory.

Read more about Dawn in my prior story:
Revolutionary Dawn Closing in on Asteroid Vesta with Opened Eyes

Dawn spacecraft under construction in cleanroom. Picture shows close up view of two science instrument; the twin Framing Cameras at top (white rectangles) and VIR Spectrometer at right. Credit: Ken Kremer

May 11, 2011December 24, 2015 by Jon Voisey

Energizing the Filaments of NGC 1275

[/caption]

When examining clusters of galaxies, astronomers often find massive elliptical galaxies lurking at the centers. In some of these, long filaments of gas and dust extend outwards from the core. One of the best examples of this is the relatively nearby galaxy NGC 1275 which lies in the constellation of Perseus. In this galaxy these tendrils are exceptionally narrow, only about 200 light years across, but as long as 20,000 light years in length. While many groups have studied them, their nature is a topic of much debate. The structures tend to be far removed from star forming regions which can cause the gas to glow. So what energy source powers these gaseous ribbons?

Answering this question is the goal of a recent paper by a team of astronomers led by Andrew Fabian at Cambridge University. Previous studies have explored the spectra of these filaments. Although the filaments have strong Hα emission, created by warm hydrogen gas, the spectra of these tendrils are unlike any nebulae within our own galaxy. The closest resemblance to galactic objects was the Crab Nebula, the remnant of a supernova that was witnessed in 1054 AD. Additionally, the spectra also reveal the presence of molecules such as carbon monoxide and H₂.

Another, previous challenge astronomers faced with these tendrils was explaining their formation. Since molecules were present, it meant the gas was cooler than the surrounding gas. In this case, the clouds should collapse due to their self gravity to form more stars than are actually present. But surrounding these tendrils is ionized plasma which should interact with the cold gas, heating it and causing it to disperse. While these two forces would counteract one another, it is impossible to consider that they would balance each other perfectly in one case, let alone for the numerous tendrils in numerous central galaxies.

This problem was apparently solved in 2008, when Fabian published a paper in Nature suggesting that these filaments were being columnated by extremely weak magnetic fields (only 0.01% the strength of Earth’s). These field lines could prevent the warmer plasma from directly entering the cold filaments since, upon interaction with the magnetic field, they would be redirected. But could this property help to explain the lesser degree of heating that still causes the emission spectra? Fabian’s team thinks so.

In the new paper, they suggests that some of the particles of the surrounding plasma do eventually penetrate the cold tendrils which explains some of the heating. However, this flow of charged particles also affects the field lines themselves inducing turbulence which also heats the gas. These effects make up the main bulk of the observed spectra. But the tendrils also exhibit an anomalous amount of X-ray flux. The team proposes that some of this is due to charge exchange in which the ionized gas entering the filaments steals electrons from the cold gas. Unfortunately, the interactions are expected to be too infrequent to explain all of the observed X-rays leaving this portion of the spectrum not fully explained by the new model.

In this article I’ve used the words “magnetic field”, “charge”, and “plasma” throughout, so of course the Electric Universe crowd is going to come flocking, declaring this validates everything they’ve ever said, just as they did when magnetic fields were first implicated in 2008. So before closing completely, I want to take a bit to consider how this new study conforms to their predictions. In general, the study agrees with their claims. However, that doesn’t mean their claims are correct. Rather, it implies they’re worthlessly vague and can be made to fit any circumstance that even briefly mentions such words as I listed above.

The EU supporters consistently refuse to provide any quantitative models which could provide true discriminating tests for their propositions. Instead, they leave the claims suspiciously vague and insist that complex physics is completely understandable with no more understanding than high school level E&M. As a result, the mere scale of their claims is horrifically inconsistent wherein they propose things like the paltry field in this article, or the slight charge on lunar craters are indicative of overwhelming currents powering stars and entire galaxies.

So while articles like this one do reinforce the EU position that electromagnetics does play a role in astronomy, it does not support the grandiose claims on entirely different scales. In the meantime, astronomers don’t argue that electromagnetic effects don’t exist (like EU supporters frequently claim). Rather, we analyze them and appreciate them for what they are: Generally weak effects that are important here and there, but they’re not some all powerful energy field pervading the universe.

May 10, 2011December 24, 2015 by VirtualAstro

Dawn Planetary Delights

[/caption]
During the month of May, four bright Planets will grace the morning sky just before dawn.

The planets Venus, Jupiter, Mercury and Mars will be involved in a series of conjunctions (close together) and will finally be joined by the thin crescent moon at the end of the month.

Twice during May some of the planets will converge to form a trio, where 3 planets will fit in an imaginary circle roughly 5 degrees across.

On the 11th Mercury, Venus and Jupiter will be within 2.5 degrees of each other, forming a very tight trio and on the 21st another trio will be formed by Mercury, Venus and Mars.

Dawn Planets 21st May Credit: Adrian West

On the 29th, 30th, and 31st, the waning crescent moon will arrive, moving past Jupiter, Mars, Venus and Mercury stretched out in a line across the eastern sky.

Unfortunately, these gatherings will be a challenge especially for observers in high latitudes, as the ecliptic in May is very shallow and low to the horizon. But if all you need is a challenge to get you out observing, then here’s your chance!

Venus and Jupiter should be easy objects to see, but Mercury and Mars will be very difficult, along with the crescent moon due to the onset of daylight.

Be careful as you will be viewing objects close to the sun. Never ever look at the sun with the naked eye, binoculars or a telescope as this will permanently damage your eyes or blind you. Viewing the sun can only be done with specialist solar telescopes and equipment.

May 10, 2011April 13, 2022 by Ken Kremer

50th Anniversary Ceremony Recreates First US Manned Spaceflight by Alan Shepard

Speakers at the May 5, 2011 celebration marking the 50th Anniversary of Alan Shepard’s first flight in space by an American astronaut included NASA officials and astronauts, Alan Shepard’s family and news media and community organizers. The event took place at the very launch pad from which Shepard blasted into space from Cape Canaveral Air Force Station, Florida, on May 5, 1961. Credit: Ken Kremer

[/caption]
NASA celebrated the 50th anniversary of the first American manned spaceflight at a special ceremony on May 5, 2011 which recreated every moment of that short suborbital flight by the late Mercury astronaut Alan B. Shepard. The event unfolded from the very spot and launch pad 5/6 where he blasted off from Cape Canaveral Air Force Station, Florida on May 5, 1961.

Shepard’s entire 15 ½ minute suborbital spaceflight aboard the “Freedom 7” capsule was replayed in a multimedia audio and video presentation that was projected on a Jumbotron erected off to the side of an 82 foot tall replica of his Mercury-Redstone 3 rocket.

Three daughters of Alan Shepard (Laura Churchley, Julie Jenkins and Alice Wackermann) pose in front of 82-foot- tall replica of Mercury-Redstone rocket which Shepard rode to space 50 years ago. Credit: Ken Kremer

The recreation was precisely timed to coincide with the exact events of the historic mission from the launch at 9:34 a.m. to the ocean splashdown some 15 minutes later at 9:49 a.m. just as they occurred 40 years ago on May 5, 1961.

The multimedia replay began at the T minus 5 minute mark in the countdown with restored voice tapes and film footage and included every single word spoken by Shepard, live views from inside his “Freedom 7” capsule, shots of the Earth below, the spaceship descending by parachute and the naval recovery vessels.

The memorial event took place at Alan Shepard’s launch pad at Cape Canaveral to recall and honor the results and legacy of the flight.

Fellow “Original 7” Mercury astronaut Scott Carpenter did a lively play by play commentary of all the events of Shepard’s flight as it was broadcast on the Jumbotron. Carpenter was the 2nd American to orbit the Earth after John Glenn.

A crowd of more than 700 folks attended including top NASA officials and spaceflight dignitaries; NASA Administrator Charles Bolden, Kennedy Space Center Director Bob Cabana, fellow Mercury astronaut Scott Carpenter; 20 members of Shepard ‘s family including his three daughters; Jack King, former chief of NASA’s Public Information Office; Bob Moser, former Chief Test Conductor, many people who worked on Project Mercury, Florida Space Coast community leaders as well as numerous space exploration fans who journeyed here from all across the globe.

Apollo 16 Moonwalker Charlie Duke, a friend and colleague of Shepard was also on hand for the festivities.

Speakers at the May 5, 2011 celebration marking the 50th Anniversary of Alan Shepard’s first flight in space from Cape Canaveral Air Force Station, Florida, on May 5, 1961. Credit: Ken Kremer

“In the audience today, we have more than 100 workers from the Mercury era who devoted their lives to flying humans safely in space,” said Kennedy Space Center Director Bob Cabana.

“You should be extremely proud of what you did for our country and for humankind,” Cabana added, as he asked them to stand and be applauded and thanked for their service by the audience.

The 50th anniversary commemoration was sponsored by NASA and local space historians and community officials.

“I remember every time he spoke, he always gave credit to everyone in NASA who built the good ships that brought him home to us safely,” said Shepard’s daughter Laura Churchley. “We thank you all very much.”

“To me — and I’ve gone through hundreds of launches and done countdowns in hundreds of launches — the first is always very special,” said Jack King. “I must admit, it’s the only one when I was misty-eyed. The first American in space! I couldn’t be prouder. And I couldn’t be prouder for being a part of it.”

Project Mercury Astronaut Scott Carpenter and Hugh Harris, Shepard event organizer and NASA shuttle launch commentator. Carpenter is one of only two surviving “Original 7” Mercury astronauts.
Credit: Ken Kremer

The ceremony was organized by Hugh Harris, retired NASA space shuttle Launch commentator, and longtime NBC Newsman Jay Barbree who is the only journalist to cover every American manned space mission.

NASA Administrator Charles Bolden salutes Alan Shepard and all the space workers who made Shepard’s historic mission possible at the 50th anniversary event on May 5, 2011 celebrating this milestone achievement in human history. Credit: Ken Kremer

“It’s an honor to share this day with so many people who helped NASA pioneer human spaceflight and enable the agency’s many accomplishments throughout our existence,” NASA Administrator Charles Bolden said. “I salute all of you.”

Shepard’s flight blasted off barely three weeks after Cosmonaut Yuri Gagarin became the first human to orbit the Earth on April 12, 1961.

The successful outcome of Shepard’s mission emboldened then President Kennedy to declare that America “should commit itself to achieving the goal, before this decade is out, of landing a man on the moon and returning him safely to the Earth,” just three weeks later on May 20, 1961.

Alan Shepard later became the fifth human to set foot on the Moon as Commander of the Apollo 14 mission. Apollo 14 blasted off on Jan. 31, 1971.

Shepard was the only member of the “Original 7” Mercury astronauts to walk on the moon and did so along with Lunar Module Pilot Edgar Mitchell. They touched down in the Fra Mauro region originally intended as the landing site for Apollo 13.

Kudos to Harris and Barbree for an outstanding effort taking everyone back in time and staging a thrilling “You are There!” experience to relive the events as they unfolded 50 years ago.

Over 100 space workers from the Mercury era attended the Alan Shepard ceremony and posed for a group photo on the 50th anniversary of the historic flight. Credit: Ken Kremer

NASA Administrator Charles Bolden and Ken Kremer
chat following the 50th Anniversary memorial event recreating Alan Shepard’s first manned spaceflight by an American astronaut. Bolden is a former astronaut and flew 4 times on the Space Shuttle and helped deploy the Hubble Space Telescope. Credit: Ken Kremer

Apollo 16 Moonwalker Charlie Duke and Ken Kremer speak at Alan Shepard ceremony.
Credit: Ken Kremer

82-foot- tall replica of Mercury-Redstone rocket which blasted Alan Shepard to space 50 years ago on May 5, 1961 from Cape Canaveral Air Force Station. Credit: Ken Kremer

May 10, 2011 by Fraser Cain

Trying out Disqus for Comments

You might have noticed that the comments for Universe Today look and behave a little differently today. That’s because we’re testing out a commenting platform called Disqus. If everything works out, it should provide a more feature rich, better looking, spam-defending comment system. The other cool thing is that it’s integrated with the rest of the Disqus network. Once you create a profile, you can write comments on thousands of other websites without having to create a profile on each one – something like this is going to be the future, so we might as well get on board now. Since Disqus is focused on creating the best possible commenting system, we should get carried along as they make improvements.

It’s still importing comments in from the WordPress system, so that’s going to take a few hours/days. Once that’s done, comments made in Disqus will be mirrored within WordPress, so we can always retreat to that system if this doesn’t work.

There’s one important decision that I still haven’t resolved yet: Who Can Comment? It can be set so anybody can reply to an article, which means there will be a lot of SPAM, but a lot of comments. I can tighten it down more (the current setting), so only registered users can comment. Or I can tighten it down even further so that users need to validate their email. I’m leaning towards the tightest control already, since I had a few nasty SPAM comments come in when I had it on the most open settings.

Anyway, let me know if you run into any problems. Let me know if things are displaying strangely for you, or you’re having trouble registering with the system.

Fraser Cain
Publisher
Universe Today

May 10, 2011December 24, 2015 by Jon Voisey

Examining the Great Wall

Several superclusters revealed by the 2dF Galaxy Redshift Survey.

[/caption]

Structure exists on nearly all scales in the universe. Matter clumps under its own gravity into planets, stars, galaxies, clusters, and superclusters. Beyond even these in scale are the filaments and voids. The largest of these filaments is known as the Sloan Great Wall. This giant string of galaxies is 1.4 billion light years across making it the largest known structure in the universe. Yet surprisingly, the Great Wall has never been studied in detail. Superclusters within it have been examined, but the wall as a whole has only come into consideration in a new paper from a team led by astronomers at Tartu Observatory in Estonia.

The Sloan Great Wall was first discovered in 2003 from the Sloan Digital Sky Survey (SDSS). The survey mapped the position of hundreds of millions of galaxies revealing the large scale structure of the universe and uncovering the Great Wall.

Within it, the wall contains several interesting superclusters. The largest of these SCl 126 has been shown previously to be unusual compared to superclusters within other large scale structures. SCl 126 is described as having an exceptionally rich core of galaxies with tendrils of galaxies trailing away from it like an enormous “spider”. Typical superclusters have many smaller clusters connected by these threads. This pattern is exemplified by one of the other rich superclusters in the wall, SCl 111. If the wall is examined in only its densest portions, the tendrils extending away from these cores are quite simple, but as the team explored lower densities, sub filaments became apparent.

Another way the team examined the Great Wall was by looking at the arrangement of different types of galaxies. In particular, the team looked for Bright Red Galaxies (BRGs) and found that these galaxies are often found together in groups with at least five BRGs present. These galaxies were often the brightest of the galaxies within their own groups. As a whole, the groups with BRGs tended to have more galaxies which were more luminous, and have a greater variety of velocities. The team suggests that this increased velocity dispersion is a result of a higher rate of interactions among galaxies than in other clusters. This is especially true for SCl 126 where many galaxies are actively merging. Within SCl 126, these BRG groups were evenly distributed between the core and the outskirts while in SCl 111, these groups tended to congregate towards the high density regions. In both of these superclusters, spiral galaxies comprised about 1/3 of the BRGs.

The study of such properties will help astronomers to test cosmological models that predict galactic structure formation. The authors note that models have generally done a good job of being able to account for structures similar to SCl 111 and most other superclusters we have observed in the universe. However, they fall short in creating superclusters with the size, morphology and distribution of SCl 126. These formations arise from density fluctuations initially present during the Big Bang. As such, understanding the structures they formed will help astronomers to understand these perturbations in greater detail and, in turn, what physics would be necessary to achieve them. To help achieve this, the authors intend to continue mapping the morphology of the Sloan Great Wall as well as other superclusters to compare their features.