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Sometimes if you aren’t watching the heavens (or the news) closely enough, you miss a major astronomical discovery.  For example last summer, astronomers discovered a galaxy which formed only one or two billion years after the Big Bang (so I guess it is unclear whethter I missed this story by one year or by 12 billion).  At any rate, the galaxy hunters used the Hubble space telescope to peer through a powerful gravitational lense far away in space.  Gravitational lenses are areas where timespace is warped like a huge lense by high-gravity phenomena, and a viewer can use them like a huge lense to see far-away objects.  By using the Hubble telescope together with the gravitational lense they were able to see back a dozen billion years in time to the edge of the universe…as it once was not long after creation.  What they saw perplexed them.

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There is a fundamental difference between galaxies.  Galaxies where stars are being formed tend to be blue and spiral shaped (like our own beloved Milky Way!).  Galaxies where stars have largely stopped forming are “red and dead” since the remaining stars tend to be long lived red dwarf stars and the bright young (short-lived) blue stars are mostly gone.  These red galaxies are not shaped like spirals, but tend to be elliptical shaped (like an egg or a football, not like one of those evil gym machines).

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The ancient galaxy at the edge of the universe was neither of those colors or shapes. It was a dense yellow disk.  Stars formed in an (enormous) accretion disk but then, for some reason, new star formation stopped.  The blue stars burned out (“the light that shines twice as bright etc, etc..”), but the yellow middle aged stars were still burning.   The galaxy had three times the mass of the Milky Way but scrunched into a pancake of much smaller area.

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So do galaxies always form as disks and then either become self-renewing blue spirals (maybe by colliding with other galaxies or clouds of dust)or dead red footballs?  Or was this early yellow disk galaxy an abberation? Or is our own galaxy truly new (well…newish…being only a few billion years old)?  I do not understand astrophysics well enough to answer these questions or even formulate them properly (although I get the sense some of these questions may not yet be answered by anyone in any comprehensive way), but I would love to hear what people can add to this rudimentary yet compelling story of shapes and colors.

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Happy (belated) Fourth of July! While everyone was out barbecuing and amusing themselves with colorful novelty explosions, there was big news in space exploration: NASA’s Juno probe, which launched from Earth five years ago, has finally reached the gas giant planet and entered orbit. The robot spacecraft, which is about the size of a basketball court, is now dancing nimbly amongst the system of moons and rings and radiation belts around the giant world.

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The probe is a remarkable spacecraft.  It traveled 2.7 billion kilometers (1.7 billion miles) to reach the exact orbit which NASA planned for it.  The secret behind its astonishing precision (even when traveling at 165,000 mph) is the autonomy of its sophisticated navigational computer.  Mission controllers do not have to radio the probe from half-way across the solar system (which would take minutes—or longer. Instead the probe navigates itself. The ship computer is shielded beneath a titanium vault to keep radiation from frying its clever electronic brain.

earth-jupiterOh man!

 

Among the planets, Jupiter is a sort of greedy eldest child.  Scientists who study planetary formation believe that the gas giant formed first of all the planets and it took the lion’s share of available matter left over from the formation of the sun. Jupiter is more than twice as massive as all the other planets in our solar system put together: indeed, it is three hundred and eighteen times more massive than Earth.  Yet we know shockingly little about this bruiser. Very basic questions about Jupiter remain unanswered. For example we still do not know whether the planet has a rocky core beneath its vast colorful atmosphere.

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As we learn more about exoplanets which orbit other stars, questions about the formation of solar systems have become more numerous.  Astronomers have been particularly perplexed by the number of “hot Jupiters,” giant gas planets which are extremely close to their stars.  Was Jupiter such a world at some point before moving to its current location, or is it a huge freak?  We simply do not know.  Scientists would also like to know more about the unimaginably vast cloudscapes of Jupiter.  What dynamics move these huge bands of pressurized gas?

As Jupiter formed, it was bombarded by strange radiation.  The depths of Jupiter’s storms must still feature giant lightning strikes. This sort of treatment can cause hydrocarbons and ammonia to form amino acids.  Maybe life has a Jovian origin.  Maybe Jupiter still has life floating around like aerial zooplankton.  Again, we just don’t know much about the giant world…

Did anybody see that amazing episode of "Cosmos"?

Did anybody see that amazing episode of “Cosmos”?

However, now that Juno has arrived we can start to answer some of these questions.  The probe will go through various start-up and test sequences until Oct. 19 when it moves to a 14-day orbit of the planet and really starts scrutinizing our giant neighbor.

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Oh, one more thing—NASA has been getting better at PR to make space more accessible and “fun” for us laypeople following at home (as witnessed by the July 4th arrival).  Juno also has a crew of three Lego astronauts: Galileo, Jupiter, and Juno herself.  This leads me to write about Juno herself, for she is a terrifying figure among the gods.  More about her tomorrow!

A Stellar Nursery in the Carina nebula: pillars of gas and dust three light years tall (NASA, JPL)

A Stellar Nursery in the Carina nebula: pillars of gas and dust three light years tall (NASA, JPL)

Stars develop in vast nebulae of swirling dust and gas that are light years across. Within these giant molecular clouds (GMCs), gravity gathers matter together into an accretion disk which then further compacts until the density and temperature of the central ball of gas reach the extremes necessary for nuclear fusion to begin. Different stars created in different GMCs thus have different spectrographic characteristics depending on the place of their creation, however GMCs tend to be inconceivably vast and multiple stars form in one stellar nursery at the same time. Such stars share similarities of composition.

The Sun

The Sun

For a long time, astronomers have sought the stars which formed at the same time in the same GMC as our beloved sun (which is approximately four and a half billion years old). Now, at long last, it seems we have found one of the sun’s bigger sisters. A yellow star in the constellation Hercules seems to have the same composition as the sun. Using elaborate computer models of stellar drift, scientists have traced the star (which goes by the unlovely name “HD 162826”) and the sun back to the same place of origin. HD 162826 is 15% larger than the sun (which is why I called it a big sister) and although it does not have any “super Jupiter” type planets, there is a possibility it may have some small rocky inner worlds. The sun has grown somewhat distant from its sibling: during the billions of years since their creation the two stars have drifted 110 light years from each other.

HD 162826

HD 162826

The discovery was made by a team of astronomers from around the world (lead by Ivan Ramirez from the University of Texas). The sun’s sister is not visible to the naked eye, but no doubt many telescopes will be trained on Hercules to discover if there is anything we can learn from our sun’s long sundered nursery mate.

An artist's rendition of NASA's MESSENGER spacecraft

Yesterday NASA’s spacecraft MESSENGER entered orbit around Mercury, the least explored of the Solar system’s rocky inner planets.  This is the first time a spacecraft has been in orbit around Mercury and it represents a tremendous engineering achievement. Since gravity becomes more intense the closer one comes to the sun, Messenger had to slingshot back and forth among the inner planets for some time in order to accomplish the tricky feat. The spacecraft had to undertake a 4.9 billion mile (about 7.9-billion kilometer) journey to enter orbit around the closest planet to the sun. Of course that hefty mileage only is equal to 0.00083 light years!

Having survived the grueling trip, the spaceship must now carry out its mission in the blistering bath of solar radiation.  To survive next to the star, Messenger is equipped with a large sun visor which prevents the little craft from frying like a quail egg.

NO! The Messenger spacecraft is not an old lady playing golf!

Messenger will try to determine the planet’s mineralogical composition and learn about its geological history (the surface of Mercury is reckoned to be one of the oldest in the solar system).  The robot probe will fully map Mercury and analyze the planet’s composition.  Like Earth (but unlike Mars and Venus) Mercury has an internal magnetic field.  Additionally, the tiny world is incredibly dense. In order to learn more about the planet’s core Messenger will measure the extent to which the planet wobbles on its rotational axis.  Studying the partially molten interior of Mercury should provide clues about how the planet formed which will help us better understand the creation of all planets (especially in conjunction with the flood of data regarding exoplanets which we are beginning to receive).

Since the craft will be trying to learn the secrets of Mercury’s molten interior, it is worth reflecting on the deity whom the planet is named after.   Although he was worshipped as a messenger, a herald, and a god of commerce, the Greco Roman god Hermes/Mercury was also quietly worshipped as a god of the underworld. The Greeks and Romans regarded him as a psychopomp who guided souls down to Hades with his magical staff. Because (like the somewhat similar African traveling god Eshu) Hermes was able to go anywhere at will he was one of the only entities in the Greco Roman pantheon free to enter and leave the underworld.

Although we are not capable like Mercury of going everywhere at our whim, I think it is a tremendous accomplishment to navigate a robot spacecraft into broiling orbit around the innermost planet.  That we are using the craft to learn the secrets of the fiery underworld of the swift planet seems like a fitting tribute to the god who was slayer of Argus, giver of charms, messenger, schemer, luck bringer, and patron of travelers and wayfarers (even those voyaging to their last end or to places the ancients could never dream of).

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