Who Owns Space History, the Public or the Astronauts?

The Apollo 13 checklist with Lovell's handwritten calculations. Image credit:

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Former NASA astronaut Jim Lovell came under fire last week when he sold a personal memento from his tenure with the space agency at an auction – the 70-page checklist from the famous Apollo 13 mission that didn’t land on the Moon. The sale has reopened the ongoing debate over who owns NASA artifacts and photographs, the astronauts or the public.

Apollo 13 commander Lovell with a model Lunar module. Image credit: NASA

In Lovell’s case, the checklist is so valuable because it contains Lovell’s hand written calculations he used to navigate the crippled Apollo 13 spacecraft after its oxygen tank exploded. That’s a pretty important piece of history for many collectors. Bids on the historic item surpassed $388,000.

But now NASA is questioning whether Lovell had the right to sell the item and profit from its sale. For now, the checklist – along with a lunar module identification plate and a hand controller from Apollo 9 sold by former astronaut Rusty Schweickart and a glove Al Shepard wore on the Moon on Apollo 14 sold at the same auction – is locked in a Heritage Auctions vault until the issue is resolved.

NASA administrator Charles Bolden released a statement saying that there have been “fundamental misunderstandings and unclear policies” regarding items astronauts took home from the Mercury, Gemini, Apollo and Skylab mission.

These “misunderstandings and unclear policies” aren’t new. Last summer, NASA filed a lawsuit against Apollo 14 astronaut Ed Mitchell after he tried to sell a 16mm video camera he used on the Moon. NASA claimed Mitchell was selling the camera illegally and sued the former astronaut for ownership rights. Mitchell countered that the camera would have been left on the Moon had he not brought it home. It’s been sitting in his personal safe since 1971.

Mitchell isn’t wrong in his self defense. In the 1960s and 1970s, NASA officials told the astronauts that they could keep certain equipment from the missions.

In 2002, former Flight Director Chris Kraft said that he approved the policy. Apollo astronauts were allowed to keep personal items that flew with them as well anything from the lunar landing module that would otherwise have been abandoned on the Moon. The astronaut had great freedom in choosing what they wanted to keep.

Rusty Schweickart during an EVA on Apollo 9. Image credit: NASA/courtesy of nasaimages.org

“It was generally accepted that the astronauts could bring back pieces of equipment or hardware from this spacecraft for a keepsake of these journeys,” Kraft wrote.

Since the end of the space race, collectors around the world have paid millions to own pieces of history themselves. NASA’s problem isn’t with these former astronauts keeping pieces of history for themselves, it’s when they sell these artifacts for personal gain that creates a problem.

Kraft’s 2002 letter doesn’t address whether or not astronauts have the right to sell their mementos. In its recent letter to the auction house, NASA insisted only the agency can approve such artifacts for sale.

Bolden said the ownership discussions will explore “all policy, legislative and other legal means” to resolve ownership issues “and ensure that appropriate artifacts are preserved and available for display to the American people.” The agency has agreed to work cooperatively with the astronauts to resolve what’s recently become a contentious issue.

Apollo 14 Lunar Module pilot Mitchell. Image credit: NASA

It is a bit of a grey area. The astronauts did the work, they trained for difficult mission and went to the Moon. But NASA footed the bill, and American tax payers funded NASA. The space agency argues that artifacts from the Apollo era should be available to the public. Everyone should be able to view and experience these pieces of one of the nation’s historic achievements.

Source: Yahoo! News

The Eagle Nebula as You’ve Never Seen it Before

A new look at M16, the Eagle Nebula in this composite from the Herschel telescope in far-infrared and XMM-Newton in X-ray. Credits: far-infrared: ESA/Herschel/PACS/SPIRE/Hill, Motte, HOBYS Key Programme Consortium; X-ray: ESA/XMM-Newton/EPIC/XMM-Newton-SOC/Boulanger

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Here’s a stunning new look deep inside the iconic “Pillars of Creation.” As opposed to the famous Hubble Space Telescope image (below) — which shows mainly the surface of the pillars of gas and dust — this composite image from ESA’s Herschel Space Observatory in far-infrared and XMM-Newton telescope in X-rays allows astronomers to peer inside the pillars and see more detail of the structures in this region. It shows how the hot young stars detected by the X-ray observations are carving out cavities, sculpting and interacting with the surrounding ultra-cool gas and dust.

But enjoy the view while you can. The sad part is that likely, this beautiful region has already been destroyed by a supernova 6,000 years ago. But because of the distance, we haven’t seen it happen yet.

Gas Pillars in the Eagle Nebula
Gas Pillars in the Eagle Nebula, as seen by the Hubble Space Telescope. Credit: NASA/ESA/STScI, Hester & Scowen (Arizona State University)

The Eagle Nebula is 6,500 light-years away in the constellation of Serpens. It contains a young hot star cluster, NGC6611, which is visible with modest back-yard telescopes. This cluster is sculpting and illuminating the surrounding gas and dust, resulting in a huge hollowed-out cavity and pillars, each several light-years long.

The Hubble image hinted at new stars being born within the pillars, deep inside small clumps known as ‘evaporating gaseous globules’ or EGGs, but because of the obscuring dust, Hubble’s visible light picture was unable to see inside and prove that young stars were indeed forming.

The new image shows those hot young stars are responsible for carving the pillars.

The new image also uses data from near-infrared images from the European Southern Observatory’s (ESO’s) Very Large Telescope at Paranal, Chile, and visible-light data from its Max Planck Gesellschaft 2.2m diameter telescope at La Silla, Chile. All the individual images are below:

M16 seen in several different wavelengths. Credits: far-infrared: ESA/Herschel/PACS/SPIRE/Hill, Motte, HOBYS Key Programme Consortium; ESA/XMM-Newton/EPIC/XMM-Newton-SOC/Boulanger; optical: MPG/ESO; near-infrared/VLT/ISAAC/McCaughrean & Andersen/AIP/ESO

Earlier mid-infrared images from ESA’s Infrared Space Observatory and NASA’s Spitzer, and the new XMM-Newton data, have led astronomers to suspect that one of the massive, hot stars in NGC6611 may have exploded in a supernova 6,000 years ago, emitting a shockwave that destroyed the pillars. But we won’t see the destruction for several hundred years yet.

Source: ESA

Carnival of Space #232

This week’s Carnival of Space is hosted by our very own Amy Shira Teitel at her very own website, Vintage Space.

Click here to read the Carnival of Space #232 and this week’s spacey goodness from around the web.

And if you’re interested in looking back, here’s an archive to all the past Carnivals of Space. If you’ve got a space-related blog, you should really join the carnival. Just email an entry to [email protected], and the next host will link to it. It will help get awareness out there about your writing, help you meet others in the space community – and community is what blogging is all about. And if you really want to help out, sign up to be a host. Send and email to the above address.

Planck Spacecraft Loses Its Cool(ant) But Keeps Going

Artist's impression of the Planck spacecraft. Credit: ESA

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After two and a half years of observing the Cosmic Microwave Background, the ESA Planck spacecraft’s High Frequency Instrument ran out of its on-board coolant gases over this past weekend, reaching the end of its very successful mission. But that doesn’t mean the end for Planck observations. The Low Frequency Instrument, which does not need to be super-cold (but is still at a bone-chilling -255 C), will continue taking data.

“The Low Frequency Instrument will now continue operating for another year,” said Richard Davis, of the University of Manchester in the UK. “During that time it will provide unprecedented sensitivity at the lower frequencies.”

From its location at the Earth/Sun’s L2 Lagrangian point, Planck was designed to ‘see’ the microwaves from the CMB and detects them by measuring temperature. The expansion of the Universe means that the CMB is brightest when seen in microwave light, with wavelengths between 100 and 10,000 times longer than visible light. To measure such long wavelengths Planck’s detectors have to be cooled to very low temperatures. The colder the spacecraft, the lower the temperatures the spacecraft can detect.

The High Frequency Instrument (HFI) was cooled to as close to 2.7K (about –270°C, near absolute zero) as possible.

Planck worked perfectly for 30 months, about twice the span originally required, and completed five full-sky surveys with both instruments.

“Planck has been a wonderful mission; spacecraft and instruments have been performing outstandingly well, creating a treasure trove of scientific data for us to work with,” said Jan Tauber, ESA’s Planck Project Scientist.

While it was the combination of both instruments that made Planck so powerful, there is still work for the LFI to do.

Now and Then. This single all-sky image simultaneously captured two snapshots that straddle virtually the entire 13.7 billion year history of the universe. One of them is ‘now’ – our galaxy and its structures seen as they are over the most recent tens of thousands of years (the thin strip extending across the image is the edge-on plane of our galaxy – the Milky Way). The other is ‘then’ – the red afterglow of the Big Bang seen as it was just 380,000 years after the Big Bang (top and bottom of image). The time between these two snapshots therefore covers about 99.997% of the 13.7 billion year age of the universe. The image was obtained by the Planck spacecraft. Credit: ESA

The scientists involved in Planck have been busy understanding and analyzing the data since Planck launched in May 2009. Initial results from Planck were announced last year, and with Planck data, scientists have created a map of the CMB identifying which bits of the map are showing light from the early Universe, and which parts are due to much closer objects, such as gas and dust in our galaxy, or light from other galaxies. The scientists have also produced a catalog of galaxy clusters in the distant Universe — many of which had not been seen before — and included some gigantic ‘superclusters,’ which are probably merging clusters.

The scientists expect to release data about star formation later next month, and reveal cosmological findings from the Big Bang and the very early Universe in 2013.

“The fact that Planck has worked so perfectly means that we have an incredible amount of data,” said George Efstathiou, a Planck Survey Scientist from the University of Cambridge. “Analyzing it takes very high-performance computers, sophisticated software, and several years of careful study to ensure that the results are correct.”

Source: ESA, UK Space Agency

SpaceX Delays Upcoming 1st Dragon Launch to ISS

SpaceX Dragon approaches the ISS, so astronauts can grapple it with the robotic arm and berth it at the Earth facing port of the Harmony node. Illustration: NASA /SpaceX

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The first test launch of a commercially built spacecraft to the International Space Station has been delayed by its builder, Space Exploration Technologies or SpaceX, in order to carry out additional testing to ensure that the vehicle is fully ready for the high stakes Earth orbital mission.

SpaceX and NASA had been working towards a Feb. 7 launch date of the company’s Dragon spacecraft and announced the postponement in a statement today (Jan. 16).

A new target launch date has not been set and it is not known whether the delay amounts to a few days, weeks or more. The critical test flight has already been rescheduled several times and was originally planned for 2011.

The unmanned Dragon is a privately developed cargo vessel constructed by SpaceX under a $1.6 Billion contract with NASA to deliver supplies to the ISS and partially replace the transport to orbit capabilities that were fully lost following the retirement of the Space Shuttle in 2011.

“In preparation for the upcoming launch, SpaceX continues to conduct extensive testing and analysis, said SpaceX spokeswoman Kirstin Grantham in the statement.

“We [SpaceX] believe that there are a few areas that will benefit from additional work and will optimize the safety and success of this mission.”

“We are now working with NASA to establish a new target launch date, but note that we will continue to test and review data. We will launch when the vehicle is ready,” said Grantham.

This SpaceX Dragon will launch to the ISS sometime in 2012 on COTS2/3 mission. Protective fairings are installed over folded solar arrays, at the SpaceX Cape Canaveral launch site.

Dragon’s purpose is to ship food, water, provisions, equipment and science experiments to the ISS.

The demonstration flight – dubbed COTS 2/3 – will be the premiere test flight in NASA’s new strategy to resupply the ISS with privately developed rockets and cargo carriers under the Commercial Orbital Transportation Services (COTS) initiative.

The Dragon will blast off atop a Falcon 9 booster rocket also built by SpaceX and, if all goes well, conduct the first ever rendezvous and docking of a privately built spacecraft with the 1 million pound orbiting outpost.

After closely approaching the ISS, the crew will grapple Dragon with the station’s robotic arm and berth it to the Earth-facing port of the Harmony node.

“We’re very excited about it,” said ISS Commander Dan Burbank in a recent televised interview from space.

An astronaut operating the ISS robotic arm will grab Dragon and position it at a berthing port at the Harmony node. Illustration: NASA /SpaceX

Since the demonstration mission also involves many other first time milestones for the Dragon such as the first flight with integrated solar arrays and the first ISS rendezvous, extra special care and extensive preparatory activities are prudent and absolutely mandatory.

NASA’s international partners, including Russia, must be consulted and agree that all engineering and safety requirements, issues and questions related to the docking by new space vehicles such as Dragon have been fully addressed and answered.

William Gerstenmaier, NASA’s associate administrator for the Human Exploration and Operations Mission Directorate recently stated that the launch date depends on completing all the work necessary to ensure safety and success, “There is still a significant amount of critical work to be completed before launch, but the teams have a sound plan to complete it.”

“As with all launches, we will adjust the launch date as needed to gain sufficient understanding of test and analysis results to ensure safety and mission success.”

“A successful mission will open up a new era in commercial cargo delivery to the international orbiting laboratory,” said Gerstenmaier.

SpaceX is also working on a modified version of the spacecraft, dubbed DragonRider, that could launch astronaut crews to the ISS in perhaps 3 to 5 years depending on the amount of NASA funding available, says SpaceX CEO and founder Elon Musk

Read Ken’s recent features about the ISS and SpaceX/Dragon here:
Dazzling Photos of the International Space Station Crossing the Moon!
Solar Powered Dragon gets Wings for Station Soar
Absolutely Spectacular Photos of Comet Lovejoy from the Space Station
NASA announces Feb. 7 launch for 1st SpaceX Docking to ISS

To The Extreme… NASA’s Fermi Gamma-Ray Telescope Gathers In High Energy

This all-sky Fermi view includes only sources with energies greater than 10 GeV. From some of these sources, Fermi's LAT detects only one gamma-ray photon every four months. Brighter colors indicate brighter gamma-ray sources. Credit: NASA/DOE/Fermi LAT Collaboration

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It scans the entire visible sky every three hours. Its job is to gather light – but not just any light. What’s visible to our eyes averages about 2 and 3 electron volts, but NASA’s Fermi Gamma-Ray Space Telescope is taking a deep look into a higher realm… the electromagnetic range. Here the energy doesn’t need a boost. It slams out gamma-rays with energies ranging from 20 million to more than 300 billion electron volts (GeV). After three years of space time, the Fermi Large Area Telescope (LAT) has produced its first census of these extreme energy sources.

Over its current operating time, Fermi has continued to paint an ever-deepening portrait of the gamma-ray sky. Even with the huge amount of data which pours in over its 180 minute window, high energy events are not common. When it comes to sources above 10 GeV, even Fermi’s LAT detects only one source about three times a year.

“Before Fermi, we knew of only four discrete sources above 10 GeV, all of them pulsars,” said David Thompson, an astrophysicist at NASA’s Goddard Space Flight Center in Greenbelt, Md. “With the LAT, we’ve found hundreds, and we’re showing for the first time just how diverse the sky is at these high energies.”

Just what exactly is out there which can produce such a powerful process? When it comes to gamma-rays, more than half of Fermi’s nearly 500 findings are active galaxies where matter falling into their central supermassive black holes produces intense jets spewing out at close to light speed. A small portion – around 10% – of the census belongs to sources within the Milky Way. These are pulsars, supernova debris and a handful of binary systems which house massive stars. What’s really interesting is the portion of totally unidentifiable sources that constitute about a third of the findings. They simply don’t have any spectroscopic counterparts and astronomers are hoping that these higher energy sources will give them new material to compare their findings against.

New sources emerge and old sources fade as the LAT's view extends into higher energies. Credit: NASA/DOE/Fermi LAT Collaboration and A. Neronov et al.

When it comes to light – obey the rules. Just as we understand that sources of infra-red light fade away when viewed in the ultra-violet, gamma-ray sources above 1 GeV can disappear without a trace when viewed at higher, or “harder,” energies. “One example is the well-known radio galaxy NGC 1275, which is a bright, isolated source below 10 GeV.” says the Fermi team. ” At higher energies it fades appreciably and another nearby source begins to appear. Above 100 GeV, NGC 1275 becomes undetectable by Fermi, while the new source, the radio galaxy IC 310, shines brightly.” The Fermi hard-source list is the product of an international team led by Pascal Fortin at the Ecole Polytechnique’s Laboratoire Leprince-Ringuet in Palaiseau, France, and David Paneque at the Max Planck Institute for Physics in Munich.

More than half of the sources above 10 GeV are black-hole-powered active galaxies. More than a third of the sources are completely unknown, having no identified counterpart detected in other parts of the spectrum. Credit: NASA's Goddard Space Flight Center

The new Fermi census will be a unique source of comparative information to assist ground-based facilities called Atmospheric Cherenkov Telescopes. These sources have confirmed 130 gamma-ray sources with energies above 100 GeV. They include the Major Atmospheric Gamma Imaging Cherenkov telescope (MAGIC) on La Palma in the Canary Islands, the Very Energetic Radiation Imaging Telescope Array System (VERITAS) in Arizona, and the High Energy Stereoscopic System (H.E.S.S.) in Namibia.

“Our catalog will have a significant impact on ground-based facilities’ work by pointing them to the most likely places to find gamma-ray sources emitting above 100 GeV,” Paneque said.

But big ground-based telescopes have big limitations. In this case, their field of view is very constricted and they can’t operate during daylight hours, full Moon or bad weather. But don’t count them out.

“As Fermi’s exposure constantly improves our view of hard sources, ground-based telescopes are becoming more sensitive to lower-energy gamma rays, allowing us to bridge these two energy regimes,” Fortin added.

Original Story Source: NASA Fermi News Release. For Further Reading: Major Atmospheric Gamma Imaging Cherenkov telescope (MAGIC) on La Palma in the Canary Islands, Very Energetic Radiation Imaging Telescope Array System (VERITAS) in Arizona and High Energy Stereoscopic System (H.E.S.S.) in Namibia. For Further Images: Fermi Images.

Astronomy Cast – Episode 248: Carina Constellation

Time for another detailed look at a constellation; one of the most fascinating in the sky, but hidden to most of the northern hemisphere: Carina. Home to one of the most likely supernova candidates we know of: Eta Carinae. Let’s talk just about this constellation, how to find it, and what you can discover in and around it.

You can watch us record Astronomy Cast live every Monday at 12:00 pm PDT (3:00 pm EDT, 2000 GMT). Make sure you circle Fraser on Google+ to see it show up in the feed. You can also see it live over on our YouTube channel.

If you’d like to be notified of all our live events, sign up for our notification email at Cosmoquest. You can check out our calendar here.

A Wrinkled Moon

Wrinkle Ridge South of Plato
Wrinkle ridges, like this one in the northern part of Mare Imbrium, were studied using telescopic observations, as early as the 1880's. Data from the Apollo era refined our understanding of these interesting features. More recently, data from the Lunar Reconnaissance Orbiter Camera is calling that understanding into question. Image credit: NASA/GSFC/Arizona State University and the author Click on the image to explore the LROC data from this area in greater detail

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Wrinkle ridges have been seen on the surface of the Moon for over a century. Studies of these interesting features began as early as 1885, with telescopic photographs, and continued beyond the Apollo era, with satellite and lander observations. Scientists thought they understood them, but the latest images from the Lunar Reconnaissance Orbital Camera (LROC) suggest we may not know the whole story.

By definition, wrinkle ridges are narrow, steep-sided ridges that form predominantly in volcanic regions. They are very complex features, which can be either straight or curved, or even be braided and zig-zagged. Their width can be anything from less than 1 km to over 20 km. And their heights range from a few meters (say the height of an average room) to 300 meters (about the height of a 100-story sky scraper). They are also asymmetric, with one side of the ridge being higher than the other. Often, these things sit on top of a gentle swell in the landscape. Features like this have been found on a number of planets throughout the Solar System, including the Moon, Mars, Mercury, and Venus.


Wrinkle Ridge South of Plato
Wrinkle ridges, like this one in the northern part of Mare Imbrium, were studied using telescopic observations, as early as the 1880's. Data from the Apollo era refined our understanding of these interesting features. More recently, data from the Lunar Reconnaissance Orbiter Camera is calling that understanding into question.

Image credit: NASA/GSFC/Arizona State University and the author
 Click on the image to explore the LROC data from this area in greater detail

The earliest researchers of lunar wrinkle ridges saw them through telescopes. When looking at the terminator (the line between the dark side and the lit side of the Moon), the angle of the Sun causes spectacular shadows to highlight the topography, allowing these otherwise subtle features to be seen. Scientists in the late 19th century believed that these wrinkle ridges, which were found predominantly in the volcanic mare regions, formed when the cooling magma shrank. The chilled crust at the very top of this magma body was now too large, and wrinkles had to form to accommodate the difference. This process was often compared to the wrinkled skin of a shriveled apple, or the skin on our hands as we age.

The dawn of the space age introduced orbiting satellites, which circled the Moon collecting images that were more detailed than had been possible ever before. Data from the 1960’s the Lunar Orbiter (LO) program, whose mission was to photograph the Moon in preparation for the Apollo missions, showed many more of these wrinkle ridge features.

Some researchers felt the LO data pointed to a volcanic origin for wrinkle ridges. They saw lava flows emanating from the wrinkle ridges and embaying impact craters. They suggested that lava flowed to the surface along linear fractures that exploited zones of weakness in the lunar crust (presumably, these weaknesses formed when impacts created the basins that lunar mare occupy). Lava that extruded onto the surface formed the wrinkle ridge features, while magma that intruded below the surface formed the regional swell the ridges sit on.

The Apollo missions, however, were able to provide information about what was happening below the surface, with the Apollo Lunar Sounder Experiment (ALSE). Data collected over a wrinkle ridge in the southeastern portion of Mare Serenitatis showed that there was some kind of topographic structure beneath the thin mare layers in this area. This suggested that wrinkle ridges were the surface expressions of thrust faults in the underlying crust. This interpretation was appealing because it explained why some wrinkle ridges are found outside of mare areas.


Bulging Wrinkle Ridge in Tsiolkovskiy Mare
Wrinkle ridges are generally steep-sided, asymmetric structures, displaying complex braiding or zig-zag patterns. This wrinkle ridge, in the northern mare of Tsiolkovskiy crater, is very different. Described as "bulging", it has a gently curved uniform shape. It is also much smaller than the wrinkle ridges seen before. This unusual wrinkle ridge suggests we may not understand the formation of these features as well as we thought.

Image credit: NASA/GSFC/Arizona State University
 Click on the image to learn more about this discovery from NASA's LROC team.

Later, studies of wrinkle-like features on Earth refined our understanding of how these features form. Now the thinking is that wrinkle ridges form by tectonic buckling of the mare areas and their surroundings. When mare lavas are extruded on the surface of the Moon, they fill up the impact basins in a series of basalt layers. The thinned crust left by the basin-forming process can’t support the weight of the mare, so the entire structure sags. The mare layer can become decoupled from the underlying regolith (the “soil” layer that impacts created between the time the basin was formed and when the first mare lavas extruded) and slide towards the sagging centre. As it does so, it bunches up in places where the decoupling is not complete. This creates a series of thrust faults at the base of the mare layer, which show up as wrinkle ridges at the surface. This decoupling process is more pronounced for thinner mare layers, which explains why we often see wrinkle ridges at the edges of a mare.

Recent findings from the Lunar Reconnaissance Orbiter Camera (LROC) may challenge this current understanding of wrinkle ridge formation. LROC images from the mare in Tsiolkovskiy crater have identified wrinkle ridges that are considerably different from the ones seen before. For one, these wrinkle ridges are not asymmetrical in profile, but have a uniformly curved shape. Also, they are much smaller, measuring less than 100 meters in width, as opposed to the 1-20 km widths seen for other wrinkle ridges.

It remains to be seen if these new wrinkle ridges will again change our understanding of how these enigmatic features form. The discovery of these particular ridges is so new that there is nothing yet published about them! Perhaps this image and others like it will help us learn more about these enigmatic features and answer questions such as: does this new wrinkle ridge represent the beginnings of their formation process and that all such ridges started out so small and symmetrical? Or maybe we’ll find that they are extrusions of particularly viscous lava, which have barely protruded above the surface along a linear fault.

Scientists plan to target this area for further data acquisition, because only more data from LRO and further research will help solve the mysteries of the wrinkled Moon.

Why Does Sirius Twinkle?

Orion and Sirius Credit Adrian West

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At this time of year, after dark we in the northern hemisphere are able to see the mighty constellation of Orion rise high in the sky with a very bright companion in a nearby constellation: Sirius – The Dog Star.

Sirius is the brightest star in the sky and can easily be found in the faint constellation of Canis Major to the left and below Orion. Its name comes from ancient Greek meaning “glowing” or “scorcher.”

Sirius (α CMa) is the alpha star in this trusty hound and is roughly 8.5 light years away from Earth, making it one of the closest stars to us. It has a tiny companion star making it a binary system composed of “Sirius A” the main component (which is a white main sequence star) and “Sirius B,” a white dwarf star. As seen with the naked eye, Sirius can be seen to twinkle many different colours low in the winter evening sky.

Sirius A
Sirius. Image credit: Hubble

So why does Sirius twinkle?

It’s not just Sirius that twinkles; all stars twinkle. Light travels many light years from stars and right at the end of its journey, it hits Earth’s atmosphere, which consists of nitrogen, oxygen and other gasses.

Earth’s atmosphere is constantly swirling around, and wind and air currents etc distort light travelling through it. This causes the light to slightly bend or shimmer and the light from distant stars twinkle. An extreme, more down-to-Earth example of this would be heat rising off of a road or a desert causing objects behind it to distort, shimmer and change colour.

Sirius appears to twinkle or shimmer more than other stars for some very simple reasons. It is very bright, which can amplify atmospheric effects and it is also very low down in the atmosphere for those in the northern hemisphere. We are actually looking at it through a very dense part of the atmosphere which can be turbulent and contain many different particles and dust. The lower towards the horizon an observer is looking, the thicker the atmosphere. The higher an observer is looking, the thinner the atmosphere. This is also the cause of colourful sunrise and sunsets.

(Addition due to the questions in the comment section: planets don’t usually twinkle because they are closer and therefore bigger — they are disks of light instead of faraway points of light. The larger disks of light usually aren’t distorted; however if you are looking through especially turbulent areas of our atmosphere, and even sometimes when looking at planets that are low in the thicker parts of the atmosphere, they will twinkle. Phil Plait, the Bad Astronomer explains it very well on his website.)

This optical illusion is a big pain for astronomers and some very large telescopes such as those in Chile and Hawaii use special equipment and techniques to reduce the effects of the atmosphere.

One of most famous telescope of them all, the Hubble Space Telescope doesn’t get affected at all by our atmosphere as it is in space, making the light from stars crystal clear.

Twinkle, twinkle little star, now we know what you are (and why you are twinkling!)

Astrophoto: Venus Above Kendal Castle

Venus Above Kendal Castle in the UK. Credit: Stuart Atkinson

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Thanks to our pal Stu Atkinson for braving the elements and risking life and limb to capture this image: “I trekked up to Kendal Castle to try and get some pictures of Venus blazing in the dusk sky above the castle ruins…,” Stu wrote on his blog, Cumbrian Sky. “On the way I fell, really went down, slipping on some mud and landing flat on my back, limbs everywhere, but when I got home and saw how the images turned out, well, it was worth the tumble!”

We agree — this is a beautiful image! Click on the image for larger version, where you can see all the gorgeous detail.

Stu took this image during the BBC Stargazing Live activities, which are currently taking place.

Want to get your astrophoto featured on Universe Today? Join our Flickr group, post in our Forum or send us your images by email (this means you’re giving us permission to post them). Please explain what’s in the picture, when you took it, the equipment you used, etc.