Elliott See (left) and Charlie Bassett, who were slated to fly aboard the Gemini 9 mission. Credit: NASA
On this day (Feb. 28) in 1966, the Gemini 9 prime crew was in a T-38 airplane making a final approach to a McDonnell Aircraft plant in St. Louis, Missouri. Amid deteriorating weather conditions, Elliot See tried to make a landing. His airplane collided with the factory building in which his spacecraft was under construction. The plane crashed, killing both See and his crewmate Charlie Bassett.
The accident sent shockwaves through the small astronaut corps, and also necessitated some hasty reassignments. The Gemini 9 backup crew of Tom Stafford and Eugene Cernan immediately became the prime crew and launched into space on May 17, 1966 on a mission that included a challenging spacewalk for Cernan.
But according to Deke Slayton, who was responsible for crew selections at the time, the deaths of See and Bassett even affected the Moon missions of Apollo.
“I … had a lot of plans for Charlie Bassett — after GT-9 [Gemini 9] he would have moved on to command module pilot for Frank Borman’s Apollo crew. Elliott was going to be backup commander for GT-12,” wrote Slayton in his memoir Deke!, which he created with help from Twilight Zone writer (and multiple book author) Michael Cassutt.
In Slayton’s mind, the loss of this one crew affected assignments all the way to the first crew who landed on the Moon: Neil Armstrong and Buzz Aldrin on Apollo 11. (Michael Collins was also on the mission, but remained in orbit in the command module.)
Buzz Aldrin on the Moon for Apollo 11. Credit: NASA
“All the backups were changed, and Jim Lovell and Buzz Aldrin wound up being pointed at GT-12,” Slayton wrote. “Without flying GT-12, it was very unlikely that Buzz would have been in any position to be lunar module pilot on the first landing attempt.”
It’s possible this crash could even have affected Apollo 13, which happened four years later.
Jim Lovell flew on Apollo 8 as the command module pilot. While Slayton didn’t state it, Lovell’s experience on that mission likely led to his appointment as commander for Apollo 14. Fate then shifted him forward a flight to the ill-fated Apollo 13, which was crippled by an oxygen tank explosion, after the original commander of that flight, Al Shepard, required a little more time for training.
As for See and Bassett, their remains were buried at Arlington National Cemetery, which is also home to many other fallen crews. Several crew members from Apollo 1, the Challenger disaster and the Columbia disaster have been laid to rest there.
Raw Cassini image captured on 26 Feb. 2013 (NASA/JPL/SSI)
Freshly delivered from Cassini’s wide-angle camera, this raw image gives us another look at Saturn’s north pole and the curious hexagon-shaped jet stream that encircles it, as well as the spiraling vortex of clouds at its center.
Back in November we got our first good look at Saturn’s north pole in years, now that Cassini’s orbit is once again taking it high over the ringplane. With spring progressing on Saturn’s northern hemisphere the upper latitudes are getting more and more sunlight — which stirs up storm activity in its atmosphere.
The bright tops of upper-level storm clouds speckle Saturn’s skies, and a large circular cyclone can be seen near the north pole, within the darker region contained by the hexagonal jet stream. This could be a long-lived storm, as it also seems to be in the images captured on November 27.
About 25,000 km (15,500 miles) across, Saturn’s hexagon is wide enough to fit nearly four Earths inside!
The Saturn hexagon as seen by Voyager 1 in 1980 (NASA)
The hexagon was originally discovered in images taken by the Voyager spacecraft in the early 1980s. It encircles Saturn at about 77 degrees north latitude and is estimated to whip around the planet at speeds of 354 km/h (220 mph.)
An image of the enclosure of the new 2.3-m Aristarchos telescope, sited at Helmos Observatory. Credit: P. Boumis, National Observatory of Athens.
Some 2,500 years ago, a Greek astronomer named Aristarchus certainly made some very correct assumptions when he postulated the Sun to be at the center of our known Universe and that the Earth revolved around it. Through this, he also knew that the stars were incredibly far away and now his namesake telescope, the new 2.3 meter Aristarchos, is taking that distant look from the Helmos Observatory, high atop the Peloponnese Mountains in Greece. Its purpose is to determine the distance and evolution of a mysterious star system – one which is encased in an ethereal nebula.
While looking at the demise of a possible binary star system, researchers Panos Boumis of the National Observatory of Athens and John Meaburn of the University of Manchester, set out to photograph this enigmatic study with the narrowband imaging camera onboard the Aristarchos telescope. Their target designation is planetary nebula KjPn8, and it was originally discovered during the 1950’s Palomar Sky Survey. What makes it out of the ordinary is two huge lobes, measuring a quarter of a degree across, which surround the system. This artifact was researched by Mexican astronomers at the San Pedro Martir Observatory some four decades after its revelation, but it wasn’t until the year 2000 that the Hubble Space Telescope uncovered its central star.
An image of the giant lobes of the planetary nebula KjPn 8 in the light of the emission lines of hydrogen and singly ionised nitrogen, obtained with the narrowband camera on the new 2.3-m Aristarchos telescope. Detailed measurements of the lobes have allowed the determination of their expansion velocity, distance and ages. The results indicate their origin in a remarkable eruptive binary system. Credit: P. Boumis / J. Meaburn
Dr. Boumis and Prof. Meaburn began to study this ancient cosmic artifact, concentrating on measuring the expansion with utmost accuracy. Through their work, they were unable to uncover the system’s distance and trace the history of the lobes through time. What they discovered was KjPn8 is roughly 6,000 light years away and the lobes of material have three epochs: 3200, 7200 and 50,000 years. According to the research team: “The inner lobe of material is expanding at 334 km per second, suggesting it originates in an Intermediate Luminosity Optical Transient (ILOT) event. ILOTs are caused by the transfer of material from a massive star to its less massive companion, in turn creating jets that flow in different directions. We believe that the core of KjPn8 is therefore a binary system, where every so often ILOT events lead to the ejection of material at high speed.”
It is certainly a triumph for the Aristachos Telescope and the new Greek facility. Dr. Bournis is quite proud of the conclusive results gathered by telescope – especially when the object in question cries out for more research. He comments: “Greece is one of the global birthplaces of astronomy, so it is fitting that research into the wider universe continues in the 21st century. With the new telescope we expect to contribute to that global effort for many years to come.”
A team of astronomers from South Africa have noticed a series of supermassive black holes in distant galaxies that are all spinning in the same direction. Credit: NASA/JPL-Caltech
Checking out the spin rate on a supermassive black hole is a great way for astronomers to test Einstein’s theory under extreme conditions – and take a close look at how intense gravity distorts the fabric of space-time. Now, imagine a monster … one that has a mass of about 2 million times that of our Sun, measures 2 million miles in diameter and rotating so fast that it’s nearly breaking the speed of light.
A fantasy? Not hardly. It’s a supermassive black hole located at the center of spiral galaxy NGC 1365 – and it is about to teach us a whole lot more about how black holes and galaxies mature.
What makes researchers so confident they have finally taken definitive calculations of such an incredible spin rate in a distant galaxy? Thanks to data taken by the Nuclear Spectroscopic Telescope Array, or NuSTAR, and the European Space Agency’s XMM-Newton X-ray satellites, the team of scientists has peered into the heart of NGC 1365 with x-ray eyes – taking note of the location of the event horizon – the edge of the spinning hole where surrounding space begins to be dragged into the mouth of the beast.
“We can trace matter as it swirls into a black hole using X-rays emitted from regions very close to the black hole,” said the coauthor of a new study, NuSTAR principal investigator Fiona Harrison of the California Institute of Technology in Pasadena. “The radiation we see is warped and distorted by the motions of particles and the black hole’s incredibly strong gravity.”
However, the studies didn’t stop there, they advanced to the inner edge to encompass the location of the accretion disk. Here is the “Innermost Stable Circular Orbit” – the proverbial point of no return. This region is directly related to a black hole’s spin rate. Because space-time is distorted in this area, some of it can get even closer to the ISCO before being pulled in. What makes the current data so compelling is to see deeper into the black hole through a broader range of x-rays, allowing astronomers to see beyond veiling clouds of dust which only confused past readings. These new findings show us it isn’t the dust that distorts the x-rays – but the crushing gravity.
Scientists measure the spin rates of supermassive black holes by spreading the X-ray light into different colors. Image credit: NASA/JPL-Caltech
“This is the first time anyone has accurately measured the spin of a supermassive black hole,” said lead author Guido Risaliti of the Harvard-Smithsonian Center for Astrophysics (CfA) and INAF — Arcetri Observatory.
“If I could have added one instrument to XMM-Newton, it would have been a telescope like NuSTAR,” said Norbert Schartel, XMM-Newton Project Scientist at the European Space Astronomy Center in Madrid. “The high-energy X-rays provided an essential missing puzzle piece for solving this problem.”
Even though the central black hole in NGC 1365 is a monster now, it didn’t begin as one. Like all things, including the galaxy itself, it evolved with time. Over millions of years it gained in girth as it consumed stars and gas – possibly even merging with other black holes along the way.
“The black hole’s spin is a memory, a record, of the past history of the galaxy as a whole,” explained Risaliti.
“These monsters, with masses from millions to billions of times that of the sun, are formed as small seeds in the early universe and grow by swallowing stars and gas in their host galaxies, merging with other giant black holes when galaxies collide, or both,” said the study’s lead author, Guido Risaliti of the Harvard-Smithsonian Center for Astrophysics in Cambridge, Mass., and the Italian National Institute for Astrophysics.
This new spin on black holes has shown us that a monster can emerge from “ordered accretion” – and not simply random multiple events. The team will continue their studies to see how factors other than black hole spin changes over time and continue to observe several other supermassive black holes with NuSTAR and XMM-Newton.
“This is hugely important to the field of black hole science,” said Lou Kaluzienski, NuSTAR program scientist at NASA Headquarters in Washington, D.C. “NASA and ESA telescopes tackled this problem together. In tandem with the lower-energy X-ray observations carried out with XMM-Newton, NuSTAR’s unprecedented capabilities for measuring the higher energy X-rays provided an essential, missing puzzle piece for unraveling this problem.”
Air glow (along with a lightning sprite) is visible in this image from the International Space Station. Credit: NASA
Light pollution is a two-way murky street. Not only have millions of people never seen the glow of our Milky Way in the night sky because of light pollution, but also when astronauts in the International Space Station look down at Earth, they see lights almost everywhere and a faint green or yellow air-glow — caused mostly by light pollution — hovers over the planet in a majority of the images they send back from space.
“Light pollution threatens the health of every living thing on Earth,” says a new planetarium-like video from the International Dark-Sky Association in collaboration with Loch Ness Productions, a U.S.-based full-dome planetarium show production company.
“Losing the Dark” illustrates problems caused by light pollution, with particular emphasis on how it affects night-sky visibility. But the video also offers simple solutions for mitigating light pollution, and reminds everyone it is not too late to save the starry sky.
Bob Parks, IDA Executive Director said, “Everyone who views ‘Losing the Dark’ can see how easy it is to make wise choices about outdoor lighting, and that together we can work to restore the night sky to its former glory.”
The video is narrated by astronomer Carolyn Collins Petersen, (whose voice you may recognize from past 365 Days of Astronomy podcasts), and the show is also available in full-dome versions for planetariums and science centers as a public service announcement.
“Planetariums champion the night sky already,” Collins Petersen said. “They tap into public awareness, so their audiences are a prime demographic for this message. The show gives planetarium professionals another tool to help educate the public about this critical issue. The HD version extends the message to more people through presentations by educators and dark-sky advocates.”
Space Shuttle Atlantis passes behind the Parkes radio telescope after final undocking from the International Space Station in July 2011. (Image Copyright: John Sarkissian; used with permission).
Chalk another one up for Citizen Science. Earlier this month, researchers announced the discovery of 24 new pulsars. To date, thousands of pulsars have been discovered, but what’s truly fascinating about this month’s discovery is that came from culling through old data using a new method.
A pulsar is a dense, highly magnetized, swiftly rotating remnant of a supernova explosion. Pulsars where first discovered by Jocelyn Bell Burnell and Antony Hewish in 1967. The discovery of a precisely timed radio beacon initially suggested to some that they were the product of an artificial intelligence. In fact, for a very brief time, pulsars were known as LGM’s, for “Little Green Men.” Today, we know that pulsars are the product of the natural death of massive stars.
The data set used for the discovery comes from the Parkes 64-metre radio observatory based out of New South Wales, Australia. The installation was the first to receive telemetry from the Apollo 11 astronauts on the Moon and was made famous in the movie The Dish. The Parkes Multi-Beam Pulsar Survey (PMPS) was conducted in the late 1990’s, making thousands of 35-minute recordings across the plane of the Milky Way galaxy. This survey turned up over 800 pulsars and generated 4 terabytes of data. (Just think of how large 4 terabytes was in the 90’s!)
Artist’s conception of a pulsar. (Credit: NASA/GSFC).
The nature of these discoveries presented theoretical astrophysicists with a dilemma. Namely, the number of short period and binary pulsars was lower than expected. Clearly, there were more pulsars in the data waiting to be found.
Enter Citizen Science. Using a program known as Einstein@Home, researchers were able to sift though the recordings using innovative modeling techniques to tease out 24 new pulsars from the data.
“The method… is only possible with the computing resources provided by Einstein@Home” Benjamin Knispel of the Max Planck Institute for Gravitational Physics told the MIT Technology Review in a recent interview. The study utilized over 17,000 CPU core years to complete.
Einstein@Home is a program uniquely adapted to accomplish this feat. Begun in 2005, Einstein@Home is a distributed computing project which utilizes computing power while machines are idling to search through downloaded data packets. Similar to the original distributed computing program SETI@Home which searches for extraterrestrial signals, Einstein@Home culls through data from the LIGO (Laser Interferometer Gravitational Wave Observatory) looking for gravity waves. In 2009, the Einstein@Home survey was expanded to include radio astronomy data from the Arecibo radio telescope and later the Parkes observatory.
Among the discoveries were some rare finds. For example, PSR J1748-3009 Has the highest known dispersion measure of any millisecond pulsar (The dispersion measure is the density of free electrons observed moving towards the viewer). Another find, J1750-2531 is thought to belong to a class of intermediate-mass binary pulsars. 6 of the 24 pulsars discovered were part of binary systems.
These discoveries also have implications for the ongoing hunt for gravity waves by such projects as LIGO. Specifically, a through census of binary pulsars in the galaxy will give scientists a model for the predicted rate of binary pulsar mergers. Unlike radio surveys, LIGO seeks to detect these events via the copious amount of gravity waves such mergers should generate. Begun in 2002, LIGO consists of two gravity wave observatories, one in Hanford Washington and one in Livingston Louisiana just outside of Baton Rouge. Each LIGO detector consists of two 2 kilometre Fabry-Pérot arms in an “L” configuration which allow for ultra-precise measurements of a 200 watt laser beam shot through them. Two detectors are required to pin-point the direction of an incoming gravity wave on the celestial sphere. You can see the orientation of the “L’s” on the display on the Einstein@Home screensaver. Two geographically separate detectors are also required to rule out local interference. A gravity wave from a galactic source would ripple straight through the Earth.
Such a movement would be tiny, on the order of 1/1,000th the diameter of a proton, unnoticed by all except the LIGO detectors. To date, LIGO has yet to detect gravity waves, although there have been some false alarms. Scientists regularly interject test signals into the data to see if system catches them. The lack of detection of gravity waves by LIGO has put some constraints on certain events. For example, LIGO reported a non-detection of gravity waves during the February 2007 short gamma-ray burst event GRB 070201. The event arrived from the direction of the Andromeda Galaxy, and thus was thought to have been relatively nearby in the universe. Such bursts are thought to be caused by neutron star and/or black holes mergers. The lack of detection by LIGO suggests a more distant event. LIGO should be able to detect a gravitational wave event out to 70 million light years, and Advanced LIGO (AdLIGO) is set to go online in 2014 and will increase its sensitivity tenfold.
The control room at LIGO Livingston. (Photo by Author).
Knowledge of where these potential pulsar mergers are by such discoveries as the Parkes radio survey will also give LIGO researchers clues of targets to focus on. “The search for pulsars isn’t easy, especially for these “quiet” ones that aren’t doing the equivalent of “screaming” for our attention,” Says LIGO Livingston Data Analysis and EPO Scientist Amber Stuver. The LIGO consortium developed the data analysis technique used by Einstein@Home. The direct detection of gravitational waves by LIGO or AdLIGO would be an announcement perhaps on par with CERN’s discovery of the Higgs Boson last year. This would also open up a whole new field of gravitational wave astronomy and perhaps give new stimulus to the European Space Agencies’ proposed Laser Interferometer Space Antenna (LISA) space-based gravity wave detector. Congrats to the team at Parkes on their discovery… perhaps we’ll have the first gravity wave detection announcement out of LIGO as well in years to come!
-Read the original paper on the discovery of 24 new pulsars here.
An artist's concept of how the spacecraft for the Inspiration Mars Foundation's "Mission for America" might be configured. Credit: Inspiration Mars.
Millionaire and space tourist Dennis Tito announced his plans for funding a commercial mission to Mars, and the mission will send two professional crew members – one man and one woman who will likely be a married couple – flying as private citizens on a “fast, free-return” mission, passing within 100 miles of Mars before swinging back and safely returning to Earth. The spacecraft will likely be tinier than a small Winnebago recreational vehicle. Target launch date is Jan. 5, 2018.
That date was picked because of the unique window of opportunity when the planets align for a 501-day mission to Mars and back.
“If we don’t seize the moment we might miss the chance to become a multi-planet species,” said journalist Miles O’Brien, who introduced the Inspiration Mars team at a webcast announcing the mission, “and if we don’t do that, one day humanity might cease to exist.”
Tito said there are lots of reasons to not to do a mission like this, “but sometimes you just have to lift anchor shove off. We need to stop being timid… Our goal is to send two people but take everyone along for the ride.”
Tito has started a new nonprofit organization, the Inspiration Mars Foundation, “to pursue the audacious to provide a platform for unprecedented science, engineering and education opportunities, while reaching out to American youth to expand their visions of their own futures in space exploration,” said a statement released by the Foundation.
Tito said this will be an American mission, not international.
The mission will be built around “proven, existing space transportation systems and technologies derived from industry, NASA and the International Space Station that can be available in time to support the launch date.”
Inspiration Mars has signed a Space Act Agreement with NASA, specifically the Ames Research Center (Ames), to conduct thermal protection system and technology testing and evaluation, as well as tapping into NASA’s knowledge, experience and technologies.
“We went to NASA and said we don’t want money, but want to partner with you for certain technologies,” said said Taber MacCallum, chief technology officer for Inspiration Mars. MacCallum is also CEO/CTO of Paragon Space Development Corporation, and was a member of the Biosphere 2 Design, Development, Test & Operations team, and a crew member in the first two-year mission. “NASA had a tremendous can-do spirit about this, and we are thrilled to be working with them.”
Here’s look at the mechanics of the free return trajectory:
The profile of the mission means once it launches, there’s no way to abort.
Tito said the mission will engage “the best minds in industry, government and academia to develop and integrate the space flight systems and to design innovative research, education and outreach programs for the mission. This low-cost, collaborative, philanthropic approach to tackling this dynamic challenge will showcase U.S. innovation at its best and benefit all Americans in a variety of ways.”
Inspiration Mars will also offer educational programs to inspire children.
“It is important that it is a man and a woman going on this mission because they represent humanity,” said Jane Poynter, also with Paragon and Inspiration Mars, who is married to MacCallum, and together they were part of the Biosphere-2 project. “But more importantly, it represents our children, because whether they are a boy or a girl, they will see themselves in this mission. Inspiration is the name of this mission and its mission.”
She said it would “challenge our children to live audacious lives,” and Inspiration Mars is partnering with several organizations to create educational programs.
Poynter said it would be important for the two astronauts to be married, to provide a “backbone of support for the crew psychologically.
“Imagine, it’s a really long road trip and you’re jammed into an RV and you can’t get out,” Poynter said. “There’s no microgravity … all you have to eat for over 500 days are 3,000 lbs of dehydrated food that they rehydrate with the same water over and over that will be recycled,” adding that the two crew will need the proven ability to be with each other for the long term.
But that segue ways into how the mission will be funded. While Tito will fund the mission exclusively for the next two years, beyond that it will be funded primarily through private, charitable donations, as well as government partners that can provide expertise, access to infrastructure and other technical assistance.
But media rights will be a big part of funding, Tito said. “I envision Dr. Phil talking to the husband-wife crew about marital problems on way to Mars,” he said.
But this is not a money-making endeavor, Tito said. “I won’t make any money on this – I’ll be a lot poorer after this mission.”
Speaking of money, one thing the Inspiration Mars team didn’t do at the briefing today was talk about how much the mission was going to cost. They said that whatever number they might quote today would probably end up being wrong. But they did say it would be a fraction of what the Curiosity rover mission cost, which is $2.5 billion.
The mission system will consist of a modified capsule launched out of Earth orbit using a single propulsive maneuver to achieve the Mars trajectory. An inflatable habitat module will be deployed after launch and detached prior to re-entry. Closed-loop life support and operational components will be located inside the vehicle, designed for simplicity and “hands-on” maintenance and repair.
Tito said the time is right for this mission, not only because of the orbital window of opportunity. “Investments in human space exploration technologies and operations by NASA and the space industry are converging at the right time to make this mission achievable,” he said.
Foundation officials are in talks with several U.S. commercial aerospace companies about prospective launch and crew vehicles and systems.
Asked about how they can possibly get a launch vehicle ready by 2018, Tito said, “The vehicles are there and we have time to get it together. I’m more concerned about the life support, the radiation and the re-entry systems.”
“Mars presents a challenging, but attainable goal for advancing human space exploration and knowledge, and as a result, we are committed to undertaking this mission,” MacCallum said. “Experts have reviewed the risks, rewards and aggressive schedule, finding that existing technologies and systems only need to be properly integrated, tested and prepared for flight.”
Tito explained that the “beauty of this mission is its simplicity.” The flyby architecture lowers risk, with no critical propulsive maneuvers after leaving Earth vicinity, no entry into the Mars atmosphere, no rendezvous and docking, and represents the shortest duration roundtrip mission to Mars. The 2018 launch opportunity also coincides with the 11-year solar minimum providing the lowest solar radiation exposure.
“Say, do you like mystery stories? Well we have one for you. The concept: relativity.”
Well look at that, it’s a new video from John D. Boswell — aka melodysheep — which goes into autotuned detail about one of the standard principles of astrophysics, Einstein’s theory of general relativity.
Featuring clips from Michio Kaku, Brian Cox, Neil deGrasse Tyson, Brian Greene and Lisa Randall, I’d say E=mc(awesome).
John has been entertaining science fans with his Symphony of Science mixes since 2009, when his first video in the series — “A Glorious Dawn” featuring Carl Sagan — was released. Now John’s videos are eagerly anticipated by fans (like me) who follow him on YouTube and on Twitter as @musicalscience.
“E = mc2… that is the engine that lights up the stars.”
(What does Einstein’s famous mass-energy equivalence equation mean? For a brief and basic explanation, check out the American Museum of Natural History’s page here.)
This image compresses the Vela movie sequence into a single snapshot by merging pie-slice sections from eight individual frames.
Credit: NASA/DOE/Fermi LAT Collaboration
I loved my Spirograph when I was young, and obviously Eric Charles, a physicist with the Fermi Gamma-ray Space Telescope team did too. Charles has taken data from Fermi’s Large Area Telescope and turned it into a mesmerizing movie of the Vela Pulsar. It actually is a reflection of the complex motion of the spacecraft as it stared at the pulsar.
The video shows the intricate pattern traced by the Fermi Gamma-ray Space Telescope’s view of the Vela Pulsar over the spacecraft’s 51 months in orbit.
Fermi orbits our planet every 95 minutes, building up increasingly deeper views of the universe with every circuit. Its wide-eyed Large Area Telescope (LAT) sweeps across the entire sky every three hours, capturing the highest-energy form of light — gamma rays — from sources across the universe. The Fermi telescope has given us our best view yet of the bizarre world of the high energy Universe, which include supermassive black holes billions of light-years away to intriguing objects in our own galaxy, such as X-ray binaries, supernova remnants and pulsars.
Francis Reddy from the Goddard Spaceflight Center describes the movie:
The Vela pulsar outlines a fascinating pattern in this movie showing 51 months of position and exposure data from Fermi’s Large Area Telescope (LAT). The pattern reflects numerous motions of the spacecraft, including its orbit around Earth, the precession of its orbital plane, the manner in which the LAT nods north and south on alternate orbits, and more. The movie renders Vela’s position in a fisheye perspective, where the middle of the pattern corresponds to the central and most sensitive portion of the LAT’s field of view. The edge of the pattern is 90 degrees away from the center and well beyond what scientists regard as the effective limit of the LAT’s vision. Better knowledge of how the LAT’s sensitivity changes across its field of view helps Fermi scientists better understand both the instrument and the data it returns.
The pulsar traces out a loopy, hypnotic pattern reminiscent of art produced by the colored pens and spinning gears of a Spirograph, a children’s toy that produces geometric patterns.
The Vela pulsar spins 11 times a second and is the brightest persistent source of gamma rays the LAT sees. While gamma-ray bursts and flares from distant black holes occasionally outshine the pulsar, the Vela pulsar is like a persistant beacon, much like the light from a lighthouse.
Find out more about this movie and the Fermi Telescope here.
An artist's conception of a comet. Credit: NASA/JPL-Caltech
Take a dirty snowball in space and hurl it towards the Sun. I dare you… and then make a prediction as to how that will look.
This is the problem comet scientists face when talking about how bright a comet will appear from Earth. They’re imaging a conglomerate of dust, ice and other materials millions of miles away. After figuring out where the comet will go, then they have to predict how it will behave.
It’s a science, to be sure, but an unpredictable one. That’s why it’s so hard to figure out how Comet ISON will fare when it gets closer to the Sun in November 2013. It could blow into pieces before arriving. It could break up when it gets close to the Sun. Or, it could live up to wildest expectations and shine so brightly you’ll be able to see it in daylight.
Veteran comet-gazers can name a few visitors that didn’t perform as well as predicted. Michael Mumma, who is with the NASA Goddard Space Flight Center’s solar system exploration division, was the lead for the agency’s scientific campaign on many comets of the past few decades. In an e-mail to Universe Today, he shared what made three comets less spectacular than predictions.
Comet Kohoutek (1973)
Comet Kohoutek in 1973. Credit: NASA/University of Arizona
Billed by some as the comet of the century, Comet Kohoutek was predicted to pass close to the Sun after it was discovered in March 1973. NASA initiated “Operation Kohoutek” to keep an eye on the comet from a network of observatories in the sky, on the ground and even telescopes in mid-air.
Mumma joked that Kohoutek was a great career launcher for him, as a spectrometer that searched for ammonia ended up getting sustained funding for further development. But the comet was a visual disappointment, he acknowledged.
“The hype surrounding Comet Kohoutek was inspired by two predictions of its possible brightness, made by a recognized senior comet scientist. The NASA spokesman chose to promote the brighter of the two, that predicted the comet would become as ‘bright as the full Moon’. He usually mentioned (softly) that we couldn’t be certain it would actually brighten that much – but the press usually ignored that disclaimer,” Mumma wrote.
“Actually, the comet really did fizzle, failing to reach even the fainter estimate – probably because at discovery it was far from the Sun and activated by something other than water ice. Under those circumstances, any prediction was bound to be highly uncertain.”
Halley’s Comet (1986)
Halley’s Comet in 1986. Credit: NASA
Halley’s is the most famous periodic comet, meaning that it returns to the inner solar system over and over again. Its bright appearance made it show up repeatedly in the historical record, most famously in the Bayeux Tapestry after it arrived in 1066 shortly before William the Conquerer successfully led the Norman Conquest of England. However, astronomers in each era saw the comet’s appearance as separate, unpredictable events.
English astronomer Edmond Halley, in examining the astronomical record in 1705, supposed that a comet with similar properties that appeared every 75 years or so was probably the same comet. Ever since then, astronomers and the public alike eagerly await each appearance. The 1910 visit was particularly spectacular, making the press set high expectations for 1986. However, the comet was much further away from the Sun in the 1980s and was fainter.
According to Mumma, the comet did not actually fizzle. Many press reports just got the brightness of the comet wrong, leading the public to believe the comet was less spectacular than predicted.
“It was a bright comet, just as scientists predicted. However, it was much brighter in the southern hemisphere than in the northern, as predicted. From Christchurch (New Zealand), and again from Cairns (Australia), it was large and the brightest object in the sky – easily seen with the unaided eye.”
As a scientific sidenote, Mumma’s team probed the comet with NASA’s Kuiper Airborne Observatory and, using infrared fluorescence spectroscopy that Mumma developed, found water for the first time in a comet.
Comet Austin (1990)
A negative image of Comet Austin. Credit: European Southern Observatory
In 1989, Sky & Telescope published a cover article on Comet Austin with the eye-catching headline: “Monster Comet is Coming!” As with Halley, many people anticipated this would be a bright comet, easily visible with the naked eye. In the book Hunting and Imaging Comets, United Kingdom amateur astronomer Martin Mobberley pointed out it was a great object in telescopes or binoculars, but not so much with the eye alone.
“Austin was less bright than some had predicted, but it was bright enough to permit major scientific successes,” Mumma added in his e-mail to Universe Today. “My team detected CO (carbon monoxide) and methanol in that comet, among the first detections of these molecules in comets at infrared wavelengths.”
All in all, these comets show that it’s really hard to figure out what they look like when they get by Earth. This means that nobody knows exactly how ISON will behave until it’s almost upon us.
