The Milky Way Mosaic

The Milky Way Galaxy is a big place.  It’s close to 100,000 lightyears across another 1,000 lightyears thick.  It’s home to around 300 billion stars, including our Sun, which revolve lazily around the galactic core once every 220 million years.  If the galaxy were shrunk to 100 miles in diameter, the Solar System would only be 1/10 of an inch big. 

Given the scales involved, mapping the Milky Way can be an arduous, complex, and frustrating undertaking.  But NASA, using infrared technology, has developed the highest-resolution image mosaic of the Milky Way ever developed, and a cool viewer to help explore it.  The image above is from the GLIMPSE viewer, sponsored by NASA and other space organizations, to view the infrared-spectrum mosaic at its highest resolution.  Click here or on the picture above to go to the viewer.

The mosaic was developed using images taken by the Spitzer Space Telescope.  NASA used infrared imagery, rather than the visible spectrum, because infrared images can see deep into the galaxy in much greater detail.  This mosaic is still being explored and analyzed, but it has already revealed previously hidden galactic objects and gorgeous images of faraway regions of space.

NASA highlighted the images with artificial colors to represent the infrared spectrum.  For example, red areas indicate a strong presence of Polycyclic Aromatic Hydrocarbons (PAHs), which light up under ultraviolet radiation.  As such, brighter red areas in the image represent the birth of recent high-mass stars, which emit the ultraviolet radiation that makes the PAHs glow.  Ionized and shocked gasses in the image show up as green.  These colors indicate additional high-mass star formation, but also supernovae. 

The GLIMPSE program provides a beautiful view of a complex galactic picture.  Take the time to explore the image and look at some of the recommended features already toggled on the image. [via Slashdot]

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The Oldest Maps of All

Mankind has been making star charts for thousands of years.  Particularly for ancient societies, stars and other celestial bodies represented their mythological figures–gods, heroes, and wild creatures–each standing for a force of nature with power over their lives.  For decades, historians and astronomers credited the ancient Babylonians with developing the earliest star catalogs.  There is evidence that these catalogs were already incredibly detailed as far back as 5,000 years ago, including predictions of planetary motion, observations of eclipses, and the earliest known named constellations.  But to Dr. Michael Rappenglueck, of the University of Munich, this history didn’t make sense.

There is plenty of unassailable evidence that societies far older than the Mesopotamians were fascinated by the stars.  Archaeological sites around the world, such as Stonehenge, show societies with less advanced mathematical knowledge than the Babylonians successfully developing complex astronomical calendars.  And given the relative ease with which an observer can spot major stars with the naked eye, it is a long-accepted historical fact that celestial bodies played a critical role in ancient religion and mythology.  So where, wondered Rappenglueck, were the maps?  Why hadn’t very ancient societies pre-dating the Babylonians made diagrams of the night sky?

According to Rappenglueck, they did, and archaeologists have been looking at them for decades without realizing it.  Amazingly, Rappenglueck claims to have discovered star charts among cave paintings created as long as 17,000 years ago.

European caves such as Lascaux in France contain a large number of striking and extremely old hand-drawn paintings by prehistoric peoples.  Some of these paintings are adorned with series of dots that, Rappenglueck claims, resemble what major constellations would have looked like tens of thousands of years ago.   Rappenglueck used algorithms of stars’ movements over time to replicate what the night sky would have looked like when the paintings were created.

According to this BBC article, the Lascaux paintings include not just representations of horses, antelopes, and bulls, but also more abstract figures, such as this painting of a bull charging a human figure with a the head of a bird, who is beside yet another bird seemingly on a stick:

According to Dr Rappenglueck, these outlines form a map of the sky with the eyes of the bull, birdman and bird representing the three prominent stars Vega, Deneb and Altair.

Together, these stars are popularly known as the Summer Triangle and are among the brightest objects that can be picked out high overhead during the middle months of the northern summer.

Around 17,000 years ago, this region of sky would never have set below the horizon and would have been especially prominent at the start of spring.

In other words, these abstract paintings are actually ancient constellations dreamed up by prehistoric man.  

Rappenglueck has also found evidence of similar star charts in other caves.  For example, he claims that an image from the “Frieze of Hands” in the Cueva de el Castillo cave in Spain is actually a representation of the Corona Borealis (“Northern Crown”) constellation.  He has produced a paper detailing how he arrived at this conclusion, including explanations of how he reproduced what the night sky would have looked like thousands of years ago. 

The more one thinks about Rappenglueck’s hypothesis, the more it seems to make sense.  Prehistoric peoples drew images from their world on the walls of the caves they lived in, so why couldn’t they have also drawn the stars?  We know very little about what, if anything, these peoples believed in terms of mythology or religion, but if later civilizations could form figures of their gods in the heavens, why not prehistoric man as well?  If these peoples would paint a bull or a horse or an antelope, why wouldn’t they also paint the figures they saw in the sky?

Rappenglueck’s theories are very difficult, if not impossible, to prove conclusively, but other astronomers consider his work reasonable and plausible.  If Rappenglueck is correct, that we can credit the men and women living tens of thousands of years ago with making the first graphical representations of the world around them–maps of the heavens, not of the earth. 

For a primer on stellar cartography, you can see this previous post.  You can also learn more on Dr. Rappenglueck’s field of archaeoastronomy by clicking here.

The Phoenix Goes to Mars

Exciting news from NASA–their long-awaited Phoenix Lander is scheduled to touch down on the Martian surface on Sunday, nine and a half months after leaving Earth.  The Phoenix is another NASA mission sent to look for evidence of life on the Red Planet.  Unlike previous missions, the Phoenix will touch down in the far Martian north–approximately equivalent to northern Canada or Alaska on Earth.  In the Martian winters, this region is covered in ice; but during this Martian summer the region will have thawed out and the lander can explore the ice and dirt for signs of life.

The map above was produced by the New York Times to show the Phoenix Lander’s final destination–a flat area of lowlands by the Heimdall Crater in the Vastitas Borealis region of Mars.  These arctic plains are barren and generally free of boulders or chasms that could endanger the lander.  Click here or on the picture above to see the full map.  You can read the full Times article here.

Previous Mars missions such as Pathfinder, and more recently Spirit and Opportunity, have focused on the planet’s equatorial regions.  And as rovers, they have moved and explored large areas of the Martian surface.  Not only is Phoenix going to the frigid Martian north instead of the relatively balmy tropics, but it is also a simple lander, not a rover.  Where the Phoenix lands, it stays, just as NASA’s Viking landers operated back in the 1970s.

The Phoenix is a remakable instrument.  Just to get to the surface safely it will have to perform a sequence of stunning aerobatic maneuvers, including a booster-slowed free-fall to the planet surface.  Here is a video from the Jet Propulsion Laboratory on the Phoenix descent:

Once on the surface it will use a robotic arm to scoop up soil and ice. The lander even has a set of small ovens to bake its samples to high temperatures, allowing its instruments to examine the liquids and gasses that form.

NASA expects to know by about 8:00 pm Eastern Time on Sunday if the lander arrived safely.
 

A “Terrible Responsibility”

The June issue of Popular Mechanics has a brief article on one of NASA’s safety features for the Space Shuttle program.  Apparently, should the Shuttle malfunction during a launch, NASA has the ability to destroy the vessel and its crew by remotely detonating charges in each of the Shuttle’s solid fuel boosters (the smaller white rockets on each side of the Shuttle during a launch).  This “terrible responsibility” falls to a flight safety officer sitting at the “flight termination” panel. 

The explosive system is officially known as the Range Safety System (RSS).  It was last used during the January 1986 launch of the Space Shuttle Challenger.  But although NASA ordered the activation of the Challenger’s RSS 110 seconds after liftoff, the charges likely did no damage becuase the Shuttle and its rocket boosters had already disintegrated.

The article includes a map of the official “launch corridor” showing the dangers involved in a malfunctioning Shuttle launch.  As the Shuttle blasts off, it ascends into orbit over the Atlantic Ocean.  But if the vessel begins to malfunction and veer off course, it only has a short time before it comes over land again, creating the possibility for significant casualties on the ground should the Shuttle and its massive quantities of fuel strike a populated area.  Click here or on the picture above to go to the full map.

The map shows two lines–one solid and one dotted.  Under no circumstances can the Shuttle cross the solid line until it is safely in orbit, and it cannot cross the dotted line unless it is functioning normally.  These lines follow the North American coastline from Nova Scotia down to the bottom of the Lesser Antilles, protecting coastal cities from the threat of a Shuttle crash.  If the Shuttle crosses the solid line before reaching orbit, or if it crosses the dotted line while malfunctioning, the safety offer is required to flip the switch to detonate the charges in the boosters.

Stellar Cartography

Stellar cartographers are responsible for mapping the accurate locations of stars, galaxies, and other celestial objects.  This sounds fairly simple to do–just look up into the night sky and make a map of what you see.  Except that unlike terrestrial cartography, all the objects you see in the night sky are in three dimensions, hundreds, thousands, millions, and sometimes billions of lightyears apart from one another.  To make matters even more confusing, every celestial object is moving in different directions at different speeds.  And even though we don’t notice it, the Earth and the rest of the Solar System are moving as well.

To help keep track of everything, stellar cartographers have divided the sky into constellations, each with official borders.  There are 88 official constellations, as designated by the International Astronomical Union in 1922.  In 1930, their borders were drawn by Eugène Delporte, a Belgian astronomer who discovered 66 asteroids during his career.  In the picture of the constellation Orion, above, the dotted lines delineate the borders between constellations, with Orion highlighted in white.  Click on the image above for the bigger picture, from the IAU.

Orion consists of seven main stars, all named on the map: Betelgeuse, Rigel, Bellatrix, Mintaka, Alnilam, Alnitak, and Saiph.  Stellar cartographers also give the major stars in each constellation designations based on Greek letters.  This system is called the Bayer Designation. The Bayer designations of the seven main stars in Orion are Alpha (α), Beta (β), Gamma (γ), Delta (δ), Epsilon (ε), Zeta (ζ), and Kappa (κ) Orionis, in the same order as the list above.  All the other major stars in the constellation also have Greek letters assigned to them.  These Greek letters are also indicated on the map.

The map also contains a few objects with a name that has a letter “M” followed by a number.  These are Messier Objects, named for French astronomer Charles Messier.  In 1781, Messier published a sky catalog with 103 bright objects he had studied. 

Finally, as I mentioned earlier, the stars in Orion look like they’re on the same plane, but in fact they are widely distributed through space in three dimensions.  For a great visualization of this distribution, take a look at this image created by Don Dixon over at Cosmographica.