Universe Today

April 25, 2013April 26, 2016 by Dan Majaess

Dust Complicates Determinations of the Distance to Galactic Center

The plane of our Milky Way galaxy (image credit: R. Bertero/deviantart, cropped by DM). Understanding the nature of the obscuring dust, indicated partly by the dark regions bisecting the plane, is key to establishing a precise distance to the Galactic center.

Obtaining an accurate distance between the Sun and the center of our Galaxy remains one of the principal challenges facing astronomers. The ongoing lively debate concerning this distance hinges partly on the nature of dust found along that sight-line. Specifically, are dust particles lying toward the Galactic center different from their counterparts near the Sun? A new study led by David Nataf asserts that, yes, dust located towards the Galactic center is anomalous. They also look at accurately defining both the distance to the Galactic center and the reputed bar structure that encompasses it.

The team argues that characterizing the nature of small dust particles is key to establishing the correct distance to the Galactic center, and such an analysis may mitigate the scatter among published estimates for that distance (shown in the figure below). Nataf et al. 2013 conclude that dust along the sight-line to the Galactic center is anomalous, thus causing a non-standard ‘extinction law‘.

The extinction law describes how dust causes objects to appear fainter as a function of the emitted wavelength of light, and hence relays important information pertaining to the dust properties.

The team notes that, “We estimate a distance to the Galactic center of [26745 light-years] … [adopting a] non-standard [extinction law] thus relieves a major bottleneck in Galactic bulge studies.”

Various estimates for the distance to the Galactic center tabulated by Malkin 2013. The x-axis describes the year, while the y-axis features the distance to the Galactic center in kiloparsecs (image credit: Fig 1 from Malkin 2013/arXiv/ARep).

Nataf et al. 2013 likewise notes that, “The variations in both the extinction and the extinction law made it difficult to reliably trace the spatial structure of the [Galactic] bulge.” Thus variations in the extinction law (tied directly to the dust properties) also affect efforts to delineate the Galactic bar, in addition to certain determinations of the distance to the Galactic center. Variations in the extinction law imply inhomogeneities among the dust particles.

“The viewing angle between the bulge’s major axis and the Sun-Galactic centerline of sight remains undetermined, with best values ranging from from 13 to … 44 [degrees],” said Nataf et al. 2013 (see also Table 1 in Vanhollebekke et al. 2009). The team added that, “We measure an upper bound on the tilt of 40 [degrees] between the bulge’s major axis and the Sun-Galactic center line of sight.”

However, the properties of dust found towards the Galactic center are debated, and a spectrum of opinions exist. While Nataf et al. 2013 find that the extinction law is anomalously low, there are studies arguing for a standard extinction law. Incidentally, Nataf et al. 2013 highlight that the extinction law characterizing dust near the Galactic center is similar to that tied to extragalactic supernovae (SNe), “The … [extinction] law toward the inner Galaxy [is] approximately consistent with extra-galactic investigations of the hosts of type Ia SNe.”

The delineation of the bar at the center of our Milky Way galaxy by Nataf et al. 2013. The bar is closer toward the Sun in the 1st Galactic quadrant. The center line represents the direction toward the constellation of Sagitarrius (image credit: Fig 17 from Nataf et al. 2013/arXiv/ApJ). — Left, the delineation of the bar at the center of the Milky Way by Nataf et al. 2013. The centerline represents the direction towards Sagittarius (image credit: Fig 17 from Nataf et al. 2013/arXiv/ApJ). Right, a macro view of the Galaxy highlighting the general orientation and location of the Galactic bar (image credit: NASA/Wikipedia). The Galactic bar is not readily discernible in the distribution of RR Lyrae variables.

Deviations from the standard extinction law, and the importance of characterizing that offset, is also exemplified by studies of the Carina spiral arm. Optical surveys reveal that a prominent spiral arm runs through Carina (although that topic is likewise debated), and recent studies argue that the extinction law for Carina is higher than the standard value (Carraro et al. 2013, Vargas Alvarez et al. 2013). Conversely, Nataf et al. 2013 advocate that dust towards the Galactic center is lower by comparison to the standard (average) extinction law value.

The impact of adopting an anomalously high extinction law for objects located in Carina is conveyed by the case of the famed star cluster Westerlund 2, which is reputed to host some of the Galaxy’s most massive stars. Adopting an anomalous extinction law for Westerlund 2 (Carraro et al. 2013, Vargas Alvarez et al. 2013) forces certain prior distance estimates to decrease by some 50% (however see Dame 2007). That merely emphasizes the sheer importance of characterizing local dust properties when establishing the cosmic distance scale.

In sum, characterizing the properties of small dust particles is important when ascertaining such fundamental quantities like the distance to the Galactic center, delineating the Galactic bar, and employing distance indicators like Type Ia SNe.

The Nataf et al. 2013 findings have been accepted for publication in the Astrophysical Journal (ApJ), and a preprint is available on arXiv. The coauthors on the study are Andrew Gould, Pascal Fouque, Oscar A. Gonzalez, Jennifer A. Johnson, Jan Skowron, Andrzej Udalski, Michal K. Szymanski, Marcin Kubiak, Grzegorz Pietrzynski, Igor Soszynski, Krzysztof Ulaczyk, Lukasz Wyrzykowski, Radoslaw Poleski. The Nataf et al. 2013 results are based partly on data acquired via the Optical Graviational Lensing Experiment (OGLE). The interested reader desiring additional information will find the following pertinent: Udalski 2003, Pottasch and Bernard-Salas 2013, Kunder et al. 2008, Vargas Alvarez et al. 2013, Carraro et al. 2013, Malkin 2013, Churchwell et al. 2009, Dame 2007, Ghez et al. 2008, Vanhollebekke et al. 2009.

The Nataf et al. 2013 results are based partly on observations acquired by the OGLE survey (image credit: OGLE team).

April 25, 2013April 26, 2016 by Tammy Plotner

Entire Galaxies Feel The Heat Of Newborn Stars

This illustration shows a messy, chaotic galaxy undergoing bursts of star formation. This star formation is intense; it was known that it affects its host galaxy, but this new research shows it has an even greater effect than first thought. The winds created by these star formation processes stream out of the galaxy, ionising gas at distances of up to 650 000 light-years from the galactic centre. Credit: ESA, NASA, L. Calçada

If you think that star-formation only has an impact within the confines of a host galaxy, then think again. Thanks to the magic of the NASA/ESA Hubble Space Telescope, astronomers are now realizing starburst activity can change the properties of galactic gases at distances almost twenty times larger than a galaxy’s visible boundaries. Not only does this affect galactic evolution, but it has ramifications on how matter and energy ripple across the cosmos.

What’s going on here? Once upon a time in the early Universe, galaxies would form new stars in huge blasts of activity known as starbursts. While it happened frequently long ago, it’s much less common now. During these starburst episodes, hundreds of millions of stars spring to light and their combined energy sets off massive stellar winds that push outward into space. While these winds were known to have effects on the parent galaxy, new research shows they have an even greater effect than anyone knew.

Recently a team of international astronomers took on twenty galaxies which are known to be hosting starburst activity. What they found was the starburst stellar winds were able to ionize gas at huge distances – up to 650,000 light years from the galaxy’s nucleus – and around twenty times beyond the galaxy’s visible perimeter. For the first time, researchers were able to verify that starburst activity could impact the gas around the parent galaxy. This new observational evidence shows just how important each phase a galaxy goes through can impact the way it form stars and how it evolves.

“The extended material around galaxies is hard to study, as it’s so faint,” says team member Vivienne Wild of the University of St. Andrews. “But it’s important — these envelopes of cool gas hold vital clues about how galaxies grow, process mass and energy, and finally die. We’re exploring a new frontier in galaxy evolution!”

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This animation shows the method used to probe the gas around distant galaxies. Astronomers can use tools such as Hubble’s Cosmic Origins Spectrograph (COS) to probe faint galactic envelopes by exploiting even more distant objects — quasars, the intensely luminous centres of distant galaxies powered by huge black holes. As the light from the distant quasar passes through the galaxy’s halo, the gas absorbs certain frequencies – making it possible to study the region around the galaxy in detail. This new research utilised Hubble’s COS to peer through the very thin outskirts of galactic halos, much further out than shown in this representation, to explore galactic gas at distances of up to twenty times greater than the visible size of the galaxy itself. Credit: ESA, NASA, L. Calçada

So how did they do it? According to the news release, the researchers employed the Cosmic Origins Spectrograph (COS) instrument located on the NASA/ESA Hubble Space telescope. By examining the spectral signature of a variety of starbirth and control galaxies, the team was able to carefully examine the regions of gas surrounding the galaxies. However, they had a little boost, too… quasars. By adding the light of the intensely luminous galactic cores to the mix, they were able to further refine their observations by watching the quasar’s light as it passed through foreground galaxies. This method allowed them to even more closely examine their targets.

“Hubble is the only observatory that can carry out the observations necessary for a study like this,” says lead author Sanchayeeta Borthakur, of Johns Hopkins University. “We needed a space-based telescope to probe the hot gas, and the only instrument capable of measuring the extended envelopes of galaxies is COS.”

The eureka moment came when the astronomers found the starburst galaxies in their samples showed abnormal amounts of highly ionized gases in their halos. By comparison, the control galaxies – those known to have no starburst activity – did not. Now they knew… the ionization had to be the product of the energetic winds which accompanied the birth of new stars. Armed with this information, researchers can now confidently say that galaxies which host starburst activity has taken on new parameters. Since galaxies enlarge by feeding on gas from the space around them and convert this into new stars, we realize that the ionization process will regulate future star formation.

“Starbursts are important phenomena — they not only dictate the future evolution of a single galaxy, but also influence the cycle of matter and energy in the Universe as a whole,” says team member Timothy Heckman, of Johns Hopkins University. “The envelopes of galaxies are the interface between galaxies and the rest of the Universe — and we’re just beginning to fully explore the processes at work within them.”

Burn, baby, burn…

Original Story Source: NASA/ESA Hubble Space Telescope News Release. Further reading: The Impact of Starbursts on the Circumgalactic Medium.

April 25, 2013December 23, 2015 by Elizabeth Howell

When Typhoid (Briefly) Struck Apollo 16

Charles Duke in a light-hearted moment during Apollo 16. Credit: NASA

Astronaut pranks are, well, just a part of the job. Often they poke at a sore spot in the astronaut’s history, and Charles Duke found himself the subject of a particularly painful one in the 1970s.

Duke was in the final moments of preparations before climbing into the Apollo 16 spacecraft, which was exploring the Moon in this week in 1972. It was a serious moment as Duke and his crew were about to rocket off to the moon. Then Duke got a surprise, courtesy of backup commander Fred Haise, as Duke recalled in an interview with NASA in 1999.

We were up climbing into the command module on the launch pad, and [launch pad leader] Guenter Wendt and the team were up there. And so John gets in, and I’m the next in on the right side. And as I start to climb in, I reach in and I look over and taped to the back of my seat was a big thing, “Typhoid Mary suit—seat.” So, we had a … laugh over that. Yeah, Fred would never let me forget that.

Typhoid Mary referred to Mary Mallon, a cook who was put under quarantine for the latter half of her life in the 1900s — against her stringent objections. She was accused of passing along typhoid to several families for which she did cooking, even though she didn’t show any symptoms herself. At the time, typhoid had no cure. Her curious story has been the subject of a PBS show and numerous books.

The joke on Duke hearkened back to the ill-fated Apollo 13 two years before, when Duke’s son caught the German measles. Duke fell ill and unwittingly exposed several astronauts during his contagion period — including the upcoming Apollo 13 prime crew of Jim Lovell, Fred Haise and Ken Mattingly.

Of the three crew members, Mattingly had not been exposed to the German measles. This led to Mattingly being yanked from the mission days before launch. Adding to the drama, Apollo 13 suffered an explosion in space that crippled the spacecraft and, without the extraordinary efforts of the astronauts and Mission Control, could have killed the crew.

Anyway, Apollo 13 came back safely, and in 1972 lessons had been learned from the mission. Haise, to his credit, wasn’t afraid to poke a little fun at the early havoc Duke’s illness wreaked on his crew.

What are your favorite astronaut pranks?

April 25, 2013December 23, 2015 by Jason Major

Saturn’s Little Wavemaking Moon

Daphnis' gravity disturbs the edges of the Keeler Gap as it travels along

Captured on January 15, this narrow-angle Cassini image shows an outer portion of Saturn’s A ring on the left and the ropy F ring crossing on the right. The thin black line near the A ring’s bright edge is the Keeler Gap, a 22-mile-wide space cleared by the passage of Daphnis, a shepherd moon barely 5 miles (about 7.5 km) across. As it travels around Saturn within the gap its gravity perturbs the fine icy particles within the rings, sending up rippling waves both before and behind it — visible here near the upper center.

From Cassini’s distance of 870,000 miles (1.4 million km) Daphnis itself is just barely visible as a single pixel within the Gap — can you see it? If not, click below…

There it is:

Highlighting Daphnis inside the Keeler Gap

While lacking the murky mystery of Titan’s atmosphere, Enceladus’ dramatic jets and the tortured and cratered surfaces found on Dione, Rhea, Mimas and many of Saturn’s larger icy moons, little Daphnis has always fascinated me because of the scalloped waves it kicks up within Saturn’s rings. Eventually these waves settle back down, but at their highest they can extend a mile or two above and below the ring plane!

Daphnis' wake casts peaked shadows on the rings — Daphnis’ wake casts peaked shadows on the rings

This effect was most pronounced during Saturn’s spring equinox in August 2009 when sunlight was striking the rings edge-on, creating strong shadows from any areas of relief.

Imagine the impressive view you’d have if you were nearby, positioned just above the rings as Daphnis approached and hurtled past, the rings rising up in mile-high peaks from the moon’s gravity before smoothing out again. Incredible!

Daphnis seen by Cassini in June 2010 (NASA/JPL/SSI)

And I’m not the only one to imagine such a scene either — apparently artist Erik Svensson is also intrigued by Daphnis, enough to have been inspired to create the image below. How very cool!

Future explorers watch Daphnis speed past at the edge of Saturn's A ring (© Erik Svennson, all rights reserved. Used with permission.) — Future explorers watch Daphnis speed past at the edge of Saturn’s A ring (© Erik Svennson, all rights reserved. Used with permission.)

Like its larger shepherd moon sister Prometheus, Daphnis may be little but still has a big effect on the icy stuff that makes up Saturn’s iconic rings.

And for lots more views of Daphnis click here (but watch out, it may just become your favorite moon too!)

Image credits: NASA/JPL-Caltech/Space Science Institute.

April 24, 2013April 26, 2016 by Nancy Atkinson

TV and Online Viewing Alert: The Man Who Tweeted Earth

Canadian astronaut Chris Hadfield in the Cupola of the International Space Station. Credit: NASA/CSA

Canadian astronaut Chris Hadfield has been called “the internet’s favorite astronaut” and with over 700,000 followers on Twitter, he may be one of the reasons why space is “hot” these days.

A new show featuring Hadfield’s mission on the International Space Station will air on the Canadian Broadcasting Corporation (CBC) on Thursday, April 25 and then will be available world-wide online on April 26.

UPDATE: The online version of this show is now available on CBC here.

CBC’s The Nature of Things is broadcasting “The Man Who Tweeted Earth,”,which looks at Hadfield’s mission and features other astronauts, scientific collaborators, Hadfield’s secret weapon family member (his son) and the Mission Control staff at the Canadian Space Agency and NASA.

Also, Universe Today is proud to say that our own Elizabeth Howell is also part of this broadcast, and she’s event featured on this trailer from the CBC!:

“Essentially, I talk about the techniques Hadfield uses to keep people engaged,” Elizabeth told me, as a teaser for the show. “He tweets about people’s hometowns, for example. I also mentioned the Shatner tweeting incident and how other Star Trek actors reacted. The entire show focuses on Hadfield on the station, the experiments he’s doing, and how folks are reacting to it.”

Elizabeth added that other astronauts and “lots of smart people” are part of the show.

For those of you in Canada (and anyone who otherwise has access to the CBC) the TV broadcast is on Thursday, April 25 at 8 p.m. (8:30 NT) on CBC-TV. There are other re-broadcasts later, so check the CBC’s website for info and to verify the times it is being shown in your time zone.

The show will be available online starting Friday, April 26th at: http://www.cbc.ca/natureofthings/episode/the-man-who-tweeted-earth.html

The Nature of Things is CBC’s flagship science television documentary show and has been broadcasting award-winning shows for more than five decades.

April 24, 2013December 23, 2015 by Katrina Cain

Giveaway: The Rocket Company

A few years back, when we were all a little younger and less jaded – okay – when I was younger and less jaded (!) Universe Today reviewed the book The Rocket Company. This book speaks to the need of bootstraping our way into funding massive space projects privately, using our own gumption, connections and personalities, and doing so without the help of big governmental organizations because, let’s face it, there is less and less of the proverbial pie to go around.

This fictional book is becoming more lifelike as time goes on with companies like Deep Space Industries, Planetary Resources and many, many others, looking to explore the infinite possibilities our Universe has to offer. On April 30th, this title will be available for free on Amazon.

For Amazon.com

For Amazon.co.uk

But for those of you who like the feel and smell of a book in your hands, Patrick Stiennon is giving away 3 free print copies of this book to three lucky Universe Today winners.

This giveaway will run for a week starting today, so get your entries in! How?

In order to be entered into the giveaway drawing, just put your email address into the box at the bottom of this post (where it says “Enter the Giveaway”) before Wednesday, May 1, 2013. We’ll send you a confirmation email, so you’ll need to click that to be entered into the drawing.

We’re only going to use these email addresses for Universe Today giveaways/contests and announcements. We won’t be using them for any other purpose, and we definitely won’t be selling the addresses to anyone else. Once you’re on the giveaway notification list, you’ll be able to unsubscribe any time you like.

April 24, 2013December 23, 2015 by Nancy Atkinson

Awesome Image from Space: Cygnus Mass Simulator Separates from Orbital’s Antares Rocket

The Cygnus mass simulator separates from the Antares rocket on its inaugural flight on April 21, 2013. Image was taken by a camera onboard the rocket. Credit: Orbital Sciences Corporation.

This image almost looks like an artist’s concept, but is an actual photo taken by a camera on board Orbital Science’s Antares rocket showing the Cygnus mass simulator shortly after separation from the rocket’s upper stage.

Antares launched on April 21 for its first test flight – dubbed the A-One mission. The goal of the flight was to test the fully integrated Antares rocket and boost a simulated version of the Cygnus cargo carrier into a target orbit of 250 x 300 kilometers and inclined 51.6 degrees.

Antares also sent a trio of off-the-shelf-smartphone “PhoneSats” to orbit. The three picture-taking satellites are named Alexander, Graham and Bell and are some of the lowest-cost satellites ever flown in space.

Orbital says that both the mass simulator and the upper stage are expected to stay in orbit for several months before their orbits degrade, causing them to re-enter and burn up in the atmosphere.

A test flight of an actual Cygnus capsule is expected later this year, and is currently scheduled for June 2013.

Source: Orbital Science Corporation

April 24, 2013December 23, 2015 by David Dickinson

Comet Lemmon, Now in STEREO

Animation of Comet 2012 F6 Lemmon as seen from NASA's STEREO ahead spacecraft. (Credit: NASA/GFSC; animation created by Robert Kaufman).

An icy interloper was in the sights of a NASA spacecraft this past weekend.

Comet 2012 F6 Lemmon passed through the field of view of NASA’s HI2A camera as seen from its solar observing STEREO Ahead spacecraft. As seen in the animation above put together by Robert Kaufman, Comet Lemmon is now displaying a fine ion and dust tail as it sweeps back out of the inner solar system on its 10,750 year plus orbit.

Comet Lemmon has been a dependable performer for southern hemisphere observers early in 2013. As we reported earlier this month for Universe Today, this comet is now becoming a binocular object low in the dawn sky for northern hemisphere astronomers.

Comet Lemmon passed perihelion at 0.73 astronomical units from the Sun on March 24th. It’s currently in the +4^th to +5 magnitude range as it heads northward through the constellation Pisces.

NASA’s twin Solar TErrestrial RElations Observatory (STEREO) spacecraft often catch sungrazing comets as they observe the Sun. Known as STEREO A (Ahead) & STEREO B (Behind), these observatories are positioned in Earth leading and trailing orbits. This provides researchers with full 360 degree coverage of the Sun. Launched in 2006, STEREO also gives us a unique perspective to spy incoming sungrazing comets. Recently, STEREO also caught Comet 2011 L4 PanSTARRS and the Earth as the pair slid into view.

Another solar observing spacecraft, the European Space Agencies’ SOlar Heliospheric Observatory (SOHO) has been a prolific comet discoverer. Amateur comet sleuths often catch new Kreutz group sungrazers in the act. Thus far, SOHO has discovered over 2400 comets since its launch in 1995. SOHO won’t see PanSTARRS or Lemmon in its LASCO C3 camera but will catch a glimpse of Comet 2012 S1 ISON as it nears the Sun late this coming November.

Like SOHO and NASA’s Solar Dynamics Observatory, data from the twin STEREO spacecraft is available for daily perusal on their website. We first saw this past weekend’s animation of Comet Lemmon passing through STEREO’s field of view on the Yahoo STEREOHunters message board.

Here’s a cool but largely unrecognized fact about comets. As they move back out of the solar system, their dust tail streams out ahead of them, driven by the solar wind. I’ve even seen a few science fiction flicks get this wrong. We simply expect comets to always stream their tails out behind them!

Another observatory in our solar observing arsenal has also moved a little closer to operability recently. The Interface Region Imaging Spectrograph (IRIS) arrived at Vandenberg recently in preparation for launch this summer on June 26^th. IRIS will be deployed from a Pegasus XL rocket carried aloft by an L-1011. NuSTAR was launched in a similar fashion in 2012. A Pegasus XL rocket will also launch the TESS exoplanet hunting satellite in 2017.

Keep an eye out for Comet Lemmon as it emerges from the dawn twilight in the days ahead. Also, be sure to post those pics to Universe Today’s Flickr community, and keep tabs on the sungrazing action provided to us by SOHO and STEREO!

April 24, 2013April 26, 2016 by Nancy Atkinson

Comet PANSTARRS: The Show’s Not Over Yet!

Comet PANSTARRS as seen over Payson, Arizona on April 24, 2013. Credit and copyright: Chris Schur

While Comet C/2011 L4 (PANSTARRS) is fading to barely naked-eye and binocular visibility (the comet has lost a full magnitude approximately every week since perihelion on March 9), astrophotographers are still able to track down the comet as it moves away from the Sun. This deep color exposure by Chris Schur in Arizona is still able to show surprising detail and Chris said via email that he was “surprised how beautifully colored the stars are in this part of the Milky Way.” Chris’s shot is a 25 minute exposure, and is an LRGB (Luminance, Red, Green and Blue — is a photographic technique used in amateur astronomy for producing good quality color photographs by combining a high-quality black-and-white image with a color image).

See some more recent PANSTARRS images from around the world, below, plus an awesome new timelapse from TWAN (The World At Night) photographer P-M Hedén:

The Visitor – Comet PanStarrs from P-M Hedén on Vimeo.

Comet C/2011 L4 (PANSTARRS) on April 23, 2013. Credit and copyright: Paul M. Hutchinson.

Comet PANSTARRS and star trails on April 21, 2013. Credit and copyright: David G. Strange.

Comet C/2011 L4 PanSTARRS in false color, 'sigma combined and rotational gradient filter (inset) C8 @ f/2 85mins. exposure. April 19, 2013. Credit and copyright: David G. Strange. — Comet C/2011 L4 PanSTARRS in false color, ‘sigma combined and rotational gradient filter (inset) C8 @ f/2 85mins. exposure. April 19, 2013. Credit and copyright: David G. Strange.

Comet C.2011 L4 (PANSTARRS) on April 15, 2013. A 5 minute exposure with a Zeiss 80mm astrograph with DSLR camera. Credit and copyright: Chris Schur.

This shot was taken on April 2 when Comet PANSTARRS was snuggling up in the sky with the Andromeda Galaxy, but this beautiful image is a recent addition to Universe Today’s Flickr page. You can see more images of PANSTARRS and the Andromeda Galaxy here and here.

13 frame stack of Comet PanSTARRS and the Andromedaa Galaxy on April 2, 2013 as seen over Leitrim, Ireland. Canon 200mm. Credit and copyright: Martin Campbell.

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

April 24, 2013December 23, 2015 by Elizabeth Howell

Why Spacewalking Is All About The Hands

NASA astronaut Shane Kimbrough works outside the International Space Station in 2008. Credit: NASA

Think about your typical construction worker — there’s a lot of reaching, bending, stretching, lifting. How do you accomplish those tasks without gravity, as astronauts do on the International Space Station?

According to astronaut Shane Kimbrough — who should know, as he spent more than 12 hours “outside” doing station work and repairs during shuttle mission STS-126 in 2008 — instead of using your feet, you transfer most of the work to your hands. Your feet are basically used to brace yourself.

“You’re moving around, kind of walking with your hands, and pulling yourself in between the handholds and the rails,” he said to Universe Today, expanding on comments he made publicly at a conference last week.

Astronauts train for hours in a large pool known as the Neutral Buoyancy Laboratory, which includes a full-size model of the station modules inside. “You build up the [hand] strength in the NBL,” Kimbrough said, “with your hands fighting against the pressure of the spacesuit. If you didn’t do that, your hands would be fatigued [during a spacewalk.]”

It’s not a perfect training environment, though. “The big difference in the water is the drag it produces. You don’t realize you are floating, at times. If you’re moving along and walking with your hands down the rail, and you stop, you will immediately stop. In space, the mass of your spacesuit keeps going even if you stop. Your body will keep moving back and forth a few times, and using more energy when you need.”

Shane Kimbrough spent more than 12 hours outside the International Space Station during one mission. Credit: NASA

During the shuttle era, astronauts tended to specialize in different areas of spaceflight — robotics and extra-vehicular activity (spacewalks) being some of the fields. The station, however, demands that astronauts be versed in both, Kimbrough said. Any crew could be called upon to do a repair on short notice, or to haul in a robotic spacecraft (like SpaceX’s Dragon) that arrives at station.

This means there’s a huge demand within NASA now for spacewalking expertise. Before stepping into the NBL, the astronauts run through the procedures in the classroom, and will get a look at the tools to make sure they understand their functions. Occasionally, a crew might pop on scuba suits to do a rough run of an expected spacewalk at the station, rehearsing where they should be and how they should position themselves.

A spacesuit really limits the astronaut’s range of motion, making the hours of training crucial. “For people like myself, with short arms, our work envelope is very small,” said Kimbrough, who is hoping for another flight assignment.

“It’s really out in front, not very far, in a circular motion. If you put your hand out in front, a small circle, that’s my work envelope. If I want to get something higher or lower, I can’t get there by reaching based on the way the [spacesuit] shoulder and arm operates. You maybe have to go sideways or upside down.”

November 3, 2007 – Canadarm2 played a big role in helping astronauts fix a torn solar array. The arm’s reach was extended by the Orbiter Boom Sensor System, and here, allowing astronaut Scott Parazynski analyses the solar panel while anchored to the boom. Credit: NASA

Spacewalking is inherently a dangerous business. Many people remember a daring station-era spacewalk in 2007, when Scott Parazynski dangled on the end of a Canadarm2 extension to stitch together a torn — and live — solar array. For this spacewalk, a lot of procedures were put together on the fly.

NASA also has a computer program that can roughly simulate how the astronauts can get into various areas of the station, and this was extensively used before Parazynski’s spacewalk, Kimbrough said.

Kimbrough’s crew had a more messy problem as they worked to repair the broken solar array rotary joint (that controlled one of the station’s solar panel arrays) and do other station work. The grease guns the crew used in that mission periodically squirted way too much grease and covered everything. The work area, the spacesuits, the tools.

“It had to do with the thermal properties,” Kimbrough said. “It would go in between pretty hard, to not being so hard. So sometimes, the grease guns that were designed at the time leaked … they have been redesigned, a few modifications, and they’ve worked well since then.”

Kimbrough himself ran into a minor, but still surprising situation when at the end of a lengthy tether. It turned out that tether had a bit of zing to it. “I was working way out on the end of the truss, and it was nighttime and I felt somebody pulling me back and almost spinning me around. The force of it surprised me the most.”

Other astronauts had warned him about that ahead of time, Kimbrough said, but he didn’t realize how vehement the pull could be. “I was a believer after that,” he joked.