By Jim Kaler

Department of Astronomy, University of Illinois

Mixed Beginnings

We start with a disturbing note, that the long-awaited James Webb Space Telescope (formerly the Next Generation Space Telescope) might be scratched by Congress. There are large cost overruns that are draining the NASA budget. It's in line with the decline of the whole space program, as evidenced quite publicly by the end of the orbiting Shuttle flights. We still hope for a JWST launch in 2015.

On the plus side, the historic horn antenna used in the discovery of the Cosmic Microwave Background (the fireball remnant of the Big Bang) has been restored. Better yet, SOFIA, the flying high-altitude infrared observatory, has taken its first science data. Just as good, the WISE ("Wide Field Infrared Survey Explorer") has released its first data set. In the first year of observation, it discovered 20 comets and 33,000 asteroids, and has since plotted a fine map of the infrared sky. More obscure, Gravity Probe B has found the appropriate evidence for spacetime distortion and frame dragging.

The Sun

The sky is of course dominated by the Sun, which is now being observed by a new 63-inch telescope at the Big Bear observatory in California. The largest of its kind, it is also equipped with adaptive optics to produce spectacular images. Space imagery both adds and supplements. SOHO keeps going, STEREO is a marvel, and the Solar Dynamics Observatory has been wildly successful.

Sunspots are related to solar meridional flows, which slowed during the last maximum and supposedly led to the great "sunspot desert" of the last minimum. The prediction of a weak next peak did not seem to come true, as the Sun has been pretty active. There is some indication from weakening magnetic fields and large-scale solar gas motions that we might be approaching a new "Maunder Minimum" of the kind in which sunspots disappeared between roughly 1645 and 1715 and is associated with a "Little Ice Age." (Not everyone agrees. The period of cold weather has also been ascribed to intense volcanism.) In any case, it seems that anyone who predicts solar behavior is usually wrong and in for a big surprise.

Ourselves: The Earth...

Water: something of a theme that streams through this account. Water was (and is) thought to have been brought to Earth by crashing comets shortly after Solar System formation. But Ceres, the largest (and first discovered) of the asteroids, is best understood by presuming a layer of internal ice, so maybe crashing asteroids brought a lot of the wet stuff too. Impactors may well have also brought us heavy metals that are incorporated into the terrestrial surface, as earlier stuff would have sunk (and did sink) into the interior.

Earth is hardly isolated. Cosmic Rays (presumably from supernova explosions) may in part be responsible for triggering lightning. Looking down, the Fermi Gamma Ray Telescope found that thunderstorms can create antimatter and gamma rays that are probably linked to upward "sprites" associated with lightning and first seen by airplane pilots.

And oh, Earth not only has its own satellite (the Moon, see the next title), it also has its own asteroid, a "Trojan" stuck in a gravitational "well" 60 degrees ahead of us in orbit. Welcome aboard. At least it can't hit us.

...and Moon

We are finally coming to grips with the structure and origin of the Moon. The latest reasoning has it rather like Earth, with a molten iron core 350 km in radius, with maybe a solid core inside and a 60-80 km crust that is (and has long been known to be) thinner on the near side (that facing Earth) than on the far side. Almost all agree that the Moon was formed when a Mars-sized competing planet hit us shortly after formation. The dichotomy in crustal depth might be due to a second hit that thickened the far side and promoted lava flows on the near side to create the dark maria. With a newly-determined age of 4.36 billion years (from the latest dating of Moon rocks), the cooling time may have been longer than expected due to tidal heating by Earth (the Moon much closer to us in early days).

More water: LCROSS showed it in pockets, but also found other volatiles like methane and ammonia. Curiously, the old Apollo moon rocks now are revealing an unexpected water content, the extra water counter to the standard formation theory, which involved the accumulation of debris after the Big Hit.

OH NO, the Moon is shrinking! Rather has shrunk. Lunar Reconnaissance Orbiter finds scarps that date to within the past billion years (the shrinkage not all that much).

Inner Planets

Mercury probably made more news than any of the others (well, there is Mars...) because of the orbit insertion of Messenger on March 18, 2011. Great numbers of images and amounts of other data reveal a planet unlike any other or expected. (But then, none is like any other.) We see heavily cratered areas, smooth volcanic plains, and polar craters that are indeed deep and dark enough to shield water (there it is again) ice against the solar heat. The surprising surface is rich in sodium and sulfur but poor in iron, the latter bound up in a huge iron core whose origins remain mysterious, though the theory of a collision that ripped off the outer rocky mantle is still viable. Oddest of all perhaps is the magnetic field, which is offset from the planet's rotation axis. One wonders why this small body, which should have cooled, should have a magnetic field at all.

Venus is known more for its possible future neglect. But not Mars. We find evidence for recent (within the past 200 million years) volcanism (which helps generate atmospheric carbon dioxide) and, from apparent rivulets, for occasional running water(!). Perhaps the best news is the launch of the Curiosity rover in November of 2011, the complex craft scheduled to land in August of 2012. It's to be lowered to the ground by a novel "sky crane."

Outer Ones

Planets seem to have shifted and migrated in the early Solar System. One idea is that an ancient 3:2 (ratio of periods) orbital resonance between Jupiter and Saturn kept Jupiter from invading the inner planetary system. Perhaps we owe our lives to it. Remember Comet Shoemaker-Levy 9 that hit Jupiter in 1994? The planet got it again in 2009 when hit by an asteroid perhaps 50 meters or more across. Spectra of the spot caused by the strike revealed iron and silicates from the impactor. If it can happen there, it can surely happen here. The best Jovian news is the launch to Jupiter of JUNO on August 5. The probe, to arrive in 2016, will examine the Jovian atmosphere and map the planet's gravitational and magnetic fields to determine its interior structure.

Cassini continues to bring back the riches of Saturn. The Great White Storm returned to the southern hemisphere, which it does periodically. Once again, the rings are explained. Both Cassini and ground-based data suggest that the rings are nearly pure (you guessed it) water ice. They are thus caused by the breakup of an icy satellite. The gravitational tidal limit is less restrictive for ice than for rock. Ice and rock were therefore separated. The ice then went around the planet and the rock crashed downward into it. The rings may therefore be nearly as old as the Solar System and not a recent acquisition.

Titan's atmosphere has some oxygen in it. Lab experiments suggest that the Titanic air could form chemicals of life. The satellite also exhibits high cirrus. Except (and they are big exceptions) for the cold and the dominance of methane, there is a remarkable similarity to Earth.

The water (a real theme) plumes of Enceladus come in part from heat produced by tidal flexing, but also by forced librations that arise from its irregular shape. Like Io to Jupiter, Enceladus has an electrical connection to Saturn, the base of it now found on the planet.

And then there is Iapetus. The old idea is that the dark side is the result of the satellite sweeping up dust blown off of others, and that the bright side is covered with snow. That is currently out. Another idea is that the ice on the dark side evaporated away, leaving a dark tarry substance. But why? Then there is the problem of the synchronous 79-day rotation, which should not be, as the satellite is too far from the planet for such a locking. That, the oblateness, and an equatorial ridge 15 kilometers high, may be the result of a collision. The debris rained back down to form the ridge, and a temporary moonlet gravitationally slowed the satellite and allowed the synchronous spin.

In July of 2011 Neptune finally completed its first orbit since discovery (which came from the perturbations it induces on the orbit of Uranus). The sea-god's planet has half a dozen captured trojans in the stable 60-degree points (ahead and behind in orbit), in addition of course to having synchronously captured Pluto into a 3:2 resonance.

Comets, Asteroids, KBOs, and Pluto

Deep Impact's imagery of Comet Hartley-2 shows that jets from the ends of the body are driven not by water (for a change) but by carbon dioxide (which sublimes quietly from the smooth, narrow, dusty center), big 10-20 centimeter aggregates of smaller pieces flying off. Then NASA did it again, when Stardust passed Comet Tempel-1, its camera revealing Deep Impact's 150-meter crater. The probe got hit with lots of dust, as the comet had just passed perihelion. Stardust then found minerals in Comet Wild that suggest liquid water. December of 2010 saw a veritable storm of two dozen Kreutz-group comets plowing into the Sun, with of course no damage to our star.

Probe Dawn imaged Vesta, the 550-km-wide asteroid (the only one visible to the naked eye). It's covered with craters that include a 450-km-wide monster at the south pole. The collision that caused it was perhaps the source of Vesta meteorites. Large grooved ridges near the equator are unexplained. Noted last year was the first recorded asteroid collision, which produced dust streaming away (but no gas) and a mysterious X-shaped head. New is a measure of 100,000 tons of the stuff in millimeter to centimeter sizes.

From asteroids cometh meteorites. A rare sighting of a pre- strike meteoroid resulted in a meteorite found to hold 19 amino acids. The Tagish Lake meteorite had amino and other organic acids that were formed within the meteorite itself (not in the interstellar medium) with the aid of water and heat generated by radioactive aluminum. In other meteorites, guanine and adenine (components of DNA) are found with non-DNA analogues, showing that they are made in space and are not contaminants.

The Solar System, like those of exoplanet systems, has a dust ring from smashed Kuiper Belt Objects. Among the biggest of the KBOs is Pluto, which sort of regained "largest" status, and is, with additional measures, now in a virtual tie with Eris. Pluto also added to its family with a fourth moon, "P4," its 32-day orbit between those of Hydra and Nix and well outside that of the innermost and (relatively) large satellite Charon.


We now launch outward from our local planetary system to the stars, wherein we first deal with the interstellar medium and star formation. Infrared radiation from dense cores (the first observational evidence of star formation) shows larger particles than we find in the ISM proper, suggesting that planet formation is already underway even as the parent star develops.

Such cores and birthing stars develop strong bipolar jets that sweep up and shock the local ISM to create Herbig-Haro Objects. Magnetic fields found in the jets may help reveal the jets' power sources. Could it be then that all such flows, including those associated with advanced-evolution (Mira) giants and planetary nebulae, be magnetically driven as well? Even outflows from supermassive black holes at the centers of galaxies may be included.


The end result of the process are planets and planetary systems orbiting the parent stars. The numbers of them found, and their incredible variety, are daunting. We can but scratch the surface. Doppler measures have given us more than 700 exoplanets, while the Kepler satellite (which looks for transits) notes as many as 3000 candidates, 200 in habitable zones. As many as half of the solar-type stars may have "terrestrial" planets. There are good odds that if a star has a planet there is another, perhaps in orbital resonance with it. A downside is that stellar oscillations, which cause the star to vary slightly, can confuse the dips in brightness caused by the transits. The upside is a treasury of information on the stars, the oscillations acting as internal probes. As a result, Kepler needs more time than designed so as to untangle the two effects.

Among the interesting results are more hot Jupiters, wrong-way planets (both possibly caused by gravitational interactions with other planets), one that encircles an inner binary star, various "superearths" (but none quite yet down to our mass), one hot Jupiter found speeding up in orbit in preparation for being swallowed by its star, systems of up to 6 or 7 planets, a superdense superearth, an "iron planet," a "diamond planet" (actually a star stripped to its core orbiting a millisecond pulsar), a "black Jupiter" for which there is no explanation, and several "free-floating" bodies, perhaps planets ejected from their systems, which with low mass brown dwarfs (substars not capable of full nuclear fusion of hydrogen to helium) may outnumber actual stars. Among the more remarkable observations is the first spectroscopy of a superearth in orbit around a red dwarf. Continuing the theme, the spectrum shows a water haze.

But don't look to globular clusters to find exoplanets, as the clusters have low metals (planet-holding stars tending to have high metal contents). Strong gravitational interactions within the clusters would also eject such small bodies.


We finally arrive at the stars themselves (probably something no spacecraft will ever do). Class Y, cooler than L and T (the latter exclusively made of brown dwarfs), is still empty, but may be on the verge of fulfillment. The coolest BD's run down to 400 Kelvin but we need to see ammonia and water to classify one as "Y." It's an important consideration, as class Y would close the gap between brown dwarfs and planets.

We've tripled the number of red dwarfs in elliptical galaxies, seeing far more than here, so star formation may have worked differently there. Oddly, even old red dwarfs, for which rotation and magnetic fields should have declined, show flaring activity (all the way into class L). Harkening to earlier comments, oscillation data from Kepler is transforming the asteroseismology business.

The vibrations of some 500 Kepler stars reveal radii and masses, the former in good shape, the latter lower than expected. Remarkably, imagers aboard the solar observatory STEREO have been able to check out background stars, resulting in the discovery of more than 100 eclipsing binaries.

Advanced evolution draws more attention. The wind from Delta Cephei (the prototype of Cepheids) blows with a strength a million times that of the solar wind, creating a shock wave half a light year across. And nobody expected gamma rays from a 2.5 magnitude symbiotic star outburst ("symbiotics" combinations of windy a href="../sow/star_intro.html#giants">giants and dense white dwarfs). Then there is yet more water, seen in extraordinary, molecule- rich IRC+10216 (centered on the Mira star CW Leonis); at 1000 Kelvin, it should not be there. It's presumably formed in the star itself.

Further along, we find the structure of a carbon-rich protoplanetary nebula (the leavings of an advanced red giant whose core is not yet hot enough to create a true planetary) to be apparently related to a binary companion in an 800 year orbit. It could then be that much of the varied structures among real planetaries, a subject that has long confused astronomers, is caused by such companions (note the rings in the Cat's Eye and others).

Supernovae, Pulsars, and Stellar Black Holes

The final product of the evolution of lower mass stars (below 8 or 9 solar masses) is the white dwarf state. Binary white dwarfs can be in incredibly tight orbit. One pair consists of mutually- stripped helium wd's (most are carbon/oxygen) that whirl around each other in 2.8 hours at 1.5 times the distance from here to the Moon. Binary white dwarfs are significant, because if they merge and have enough mass to exceed the 1.4 solar mass support limit, they will collapse and violently flame out in Type Ia supernova explosions.

A roughly equal number of supernovae are of Type II, in which the core of a massive star (one born with greater than 8 to 10 times the solar mass) fuses to iron and implodes, an outbound shock wave exploding the vast stellar envelope. A prime candidate is familiar Betelgeuse, which has an outer envelope even bigger than expected, its oxygen-rich dust extending to 400 AU.

Famed Messier 101 made special news with a nearby ninth magnitude Type Ia supernova that was easily accessible from the back yard with a small telescope. Adding to the mix of supernovae (which include the core-collapse Ibc's) is a new class of ultra-bright hydrogen-less (like the Ia's) supernovae that nobody really knows anything about.

It's long been thought that cosmic rays (see above) are produced by acceleration of ambient particles by supernova explosions. The different energy spectra of protons and alpha particles (helium nuclei) suggest otherwise. The issue needs further resolution.

The origins of Type II core-collapse supernovae are more or less understood (except for the "minor details" of the energy source of the explosion). The detailed origins of the Ia's, however, are still controversial, there being two roads to success, the merger of a double white dwarf or the tidal overflow from a normal star onto a white dwarf companion, either of which can cause the result to exceed the 1.4 solar mass Chandrasekhar limit. There is evidence on both sides. Note the double white dwarf in tight orbit above, which supports the merger theory. On the other hand the spectral signature of sodium in Ia supernovae supports mass transfer.

The expanded leavings of supernovae, the blown-out clouds (the gaseous "supernova remnants"), dot the sky. The outbound remnant of Supernova 1987a in the Large Magellanic Cloud is filled with half a solar mass of dust, much more than expected. The best-known supernova remnant of all is the easily accessible Crab Nebula, Messier 1, in Taurus. It's long been used as a standard source for X-ray intensities (in units of "crabs"). But the standard is hardly that, as we find the X-ray Crab to vary by several percent a year. Moreover it has been dimming and has been seen to pop gamma-ray flares.

The final by-products of core-collapse Type II's are either neutron stars (which include pulsars) or black holes (the Ia's annihilating themselves). Within the pulsar class are the magnetars with fields 100 or so times "normal." One such seems to have come from a star with an initial mass of more than 40 times that of the Sun, which provides a lower limit to black hole formation.

Gamma Ray Bursts

At the extreme energetic end are distant gamma ray bursts (GRB's), of which there are two kinds,"short" and "long," divided at about two-second duration. Computer simulations suggest that short bursts are caused by tangled magnetic fields that derive from the merger of orbiting neutron stars as they form black holes. The long bursts have long been known (so far as we can know) to be caused by "hypernovae" collapsing to black holes, both kinds of bursts producing their radiation in narrow cones. We see the GRBs only when the cone-shaped jets are pointed at us.

Also at the energetic edge was the observation of a supermassive black hole in the center of a distant galaxy that apparently swallowed an orbiting star, which produced a third kind of gamma- ray burst that poured out in bipolar jets quite like the usual short and long bursts.

The Galaxy

Every year seems to include a new idea for the structure of our Galaxy. Now we are apparently in a three-arm spiral (and from much prior data, a barred one).

Of more dramatic interest is observation by the Fermi Gamma Ray Observatory of huge gamma-ray bubbles that spring in bipolar flows from the Galactic center perpendicular to the plane that are 25,000 light years long. We might speculate that they are caused by some kind of burp from the central supermassive black hole or are expanding superbubbles that arise from a high star formation rate that results in powerful winds and great supernova rates. But nobody really knows their origins.

Galaxies, Quasars, and the Distant Universe

First we had another galaxy redshift record of z = 8.6 ("z" the shift in wavelength relative to the rest wavelength), which took us back 13.1 billion light years, some 600 million years after the Big Bang, which restricts the time of re-ionization of the Universe following the so-called "dark ages" of neutrality. Then a bit later comes the news of z = 10.3, taking us to a look-back time of 13.2 billion light years, 500 megayears after the creation event. We are slowly getting there, back to origins, which is why we need the JWST (see the opening paragraph).

The most distant galaxy cluster comes in at z = 5.3, at an age of 1.1 billion years. The hot gas touted to be within galaxy clusters is being increasingly revealed, PLANCK (the CMB satellite) finding a hot medium with temperatures in the tens to hundreds of millions Kelvin. A record of sorts among clusters is set by the merger of not just a pair of them but by four at the same time to make Abell 2744, the results very visible in X-ray radiation.

Then there is the 770 megayear fully functional quasar (a forming galaxy surrounding a superenergetic supermassive black hole). How on Earth (or in the Heavens) could it develop so quickly? Another distant QSO at 11 billion years in time from us is seen to be surrounded by a cloud of (yet more) water vapor. Outflows from the supermassive black holes that make the quasars drive away the infalling galactic gas, and therefore are self-limiting systems that shut themselves down, which explains why quasars are all so far away (distant in time). In that sense there is a small (it's all relative) nearly dead quasar at the center of our of Milky Way Galaxy.

Massive ionization in the early Universe is seen through the observation of nearly three dozen "supernebulae." Seen through their Lyman-Alpha radiation, the biggest of the blobs, at z = 3.1 (2.1 billion years after the Big Bang), is 300,000 light years across, thrice the size of our own Galaxy. They represent one more still-obscure step in the creation of what we see around us today. (Lyman Alpha is the fundamental emission line of hydrogen. Produced by electron jumps from the second energy level down to the lowest energy state, at rest (no large radial motion) it is found in the middle ultraviolet, but at high redshift lies in the optically-observable realm.)

But which actually came first, black holes that acted as nucleating cores of galaxies, or early galaxies that then formed the black holes? The opinions fall on the former side, supported by the discovery of a distant, early, small galaxy that already has a massive black hole at its core. That said, did early galaxies form through mergers of smaller ones, or more slowly from infalling gas? We get both sides, and no decision. Only the galaxies themselves seem to know.

Dark Matter, Dark Energy, and the Hubble Constant

At the end, we search for the origins of most of the mass-energy of the Universe. Normal matter, including hot intergalactic gas, seems to make up a mere four percent of it, while 22 percent is in dark matter and 74 percent in dark energy (these numbers somewhat dependent on the mode of research). Dark matter is "visible," its distribution measurable, only through its gravity. The leading candidate for it is a vast collection of exotic, weakly interacting massive particles ("WIMPS") that have yet to be found.

Dark energy (and its mass equivalence) is known through the deviation of the Hubble Law (redshift versus distance) from a straight line. The weight of evidence is that DE is a property of spacetime itself as first suggested (for the wrong reason) by Einstein. Support comes from observations of gravitational lensing, in which light from background galaxies is split into different paths through a closer cluster 2.2 billion light years away, allowing the structure of spacetime to be examined.

The Hubble Telescope era (which includes a lot of other instrumentation) finally led to the resolution of the Hubble Constant, the rate at which the Universe is expanding. The value currently ranges from 70.4 to 74.2 kilometers per second per megaparsec, quite a change from earlier years when the range from different observers went from under 50 to near 100. Taking everything into account, the age of the Universe, the time since the Big Bang, comes in close to 13.7 billion years. Included within it almost immediately after the event were the atoms of our own Earth and our own selves, all of us the produced by everything that is out there.