Ask any long-time stargazer who has had the greatest impact on amateur astronomy, and two names will surely come up.

The first is Russel W. Porter, who (with help from Albert Ingalls of Scientific American) jump-started amateur telescope making in the 1920s. Every year more than 1,000 amateur astronomers still gather atop Breezy Hill in southern Vermont, where Porter and the Springfield Telescope Makers first gathered to test-drive their glass-and-metal creations.

The other is John Dobson, who turned telescope making on its head during the 1960s and '70s by using simple materials to produce low-cost, large-aperture reflectors. Today millions of stargazers worldwide use Dobsonian telescopes to sweep the sky, though (as Dobson himself will tell you) these are really just Newtonian reflectors affixed to the simple alt-azimuth wooden mounts that he popularized.

Dobson turns 95 on September 14th, and astronomy activist Thilina Heenatigala wants everyone to join him in sending birthday wishes. You can either send a message to wishdobson95@gmail.com or post a comment on Heenatigala's Dobson-turns-95 website.

These days Dobson isn't barnstorming the U.S. to drum up interest in telescope making and to share the joys of simple stargazing. Instead, he's espousing a personal concept of cosmology that is, to be charitable, at odds with conventional thought.

Here's a recent snippet, captured last January by filmmaker and Dobson documentarian Jeffrey Jacobs: "The Big Bang model takes nonexistence for granted and gets the universe out of nothing, whereas what I see as my model takes existence for granted — but not space and time." You can get a fuller glimpse of Dobson's universe in this 6½-minute excerpt from a recent interview.

But make no mistake: two or three decades ago, Dobson was a force of nature in telescope-making circles, a man who singlehandedly revolutionized concepts of aperture, portability, and ease of use. In 1968, he cofounded the San Francisco Sidewalk Astronomers, which continues to thrive. Three years later he and his group rumbled into the Riverside Telescope Makers' Conference with a 24-inch f/6.5 reflector housed in a thick cardboard tube.

A few years before I joined the Sky & Telescope staff, Dobson sent an article on his unconventional techniques to the magazine for publication. Charlie Federer, S&T's founder and editor, rejected the submission. ""While your shortcuts undoubtedly help to demonstrate large amateur telescopes," Federer wrote in reply, "they can hardly lead to satisfactory instruments of the kind most amateurs want in these large sizes." Dobson still has that letter.

In the end he did get his due in S&T. He authored a long article titled "Have Telescopes, Will Travel" in the April 1980 issue, and David Levy offered a gracious profile of Dobson in the September 1995 issue, to mark his 80th birthday. Dobson also wrote, together with Norm Sperling, How and Why to Make a User-Friendly Sidewalk Telescope, a hardbound book as remarkable for its wooden front and back covers as for the telescope-making wisdom dispensed between them.

So here's to you, John — and I hope to help celebrate your centennial five years from now!

It's been more than two decades since we Earthlings got word that a star in the Large Magellanic Cloud had blown itself to smithereens.

Supernova 1987A peaked at 3rd magnitude, making it a snap to spot by eye. But, with its declination of -69°, the blast was invisible to virtually everyone north of the equator. I'm jealous of my southern astro-friends because I never got to see it. (In fact, I wonder how the popular perception of and appreciation for astronomy might be different had this event been in view from northern skies — a topic for another day!)

Fortunately, the Hubble Space Telescope started observing SN 1987A within months of its launch in 1990. Those first views revealed a ring of matter thrown out by the star about 20,000 years before its demise. The supernova's expanding shock wave eventually crashed into that ring, creating a necklace of bright knots first spotted in 1995 HST images. Observers have kept tabs on this ring ever since — primarily with an instrument called the Space Telescope Imaging Spectrograph, or STIS, which astronauts installed on Hubble in 1997.

Unfortunately, an electronic failure in 2004 rendered STIS inoperable, and astronomers had to make do without its services until last year, when spacewalking astronauts replaced a faulty circuit board and brought STIS back to life.

In the September 2nd edition of Science Express, a star-studded international team of astronomers describe observations of the supernova made with STIS earlier this year, the first in six years. The ejected ring is still there, now studded with about 30 hotspots. Over time, as the supernova's shock wave continues to barrel outward, these should merge into a single bright band.

More interesting is the insight being gleaned from a second shock wave, this one triggered by the ring itself and propagating back toward what's left of the progenitor star and through the supernova's expanding debris. The team reports that spectra of this inner shock reveal lots of hydrogen, as you'd expect, but they also see some other emissions that are probably from nitrogen and perhaps from carbon.

Essentially, the now-gone star has laid bare whatever was inside when it exploded, and over time careful observations by HST and other telescopes will, in Humpty Dumpty fashion, attempt to put the progenitor star back together again.

"I think a great thing here is the resurrection of STIS," notes coauthor Robert Kirshner (Harvard-Smithsonian Center for Astrophysics). "Astronauts zipping out 114 screws while wearing boxing gloves were not just doing it for the challenge! This paper shows that the instrument is back working, and that we're finding out new things about an object that is about the same age as HST."

Read more about the new findings in this University of Colorado press release.

Over the weekend I came across an excitedly-headlined BBC report suggesting that not one but two impacts in quick succession doomed the dinosaurs 65 million years ago.

One was the giant, now-famous pounding called Chicxulub that gouged out a crater 110 miles (180 km) wide in what's now the Yucatán Peninsula. The other was a smaller crater named Boltysh, only 16 miles (24 km) across, in central Ukraine.

I thought, "Hmm . . . this sounds familiar" — and I was right.

Loyal followers of S&T.com will remember reading about Boltysh in 2002. That's when Simon P. Kelley (Open University, United Kingdom) and Eugene Gurov (National Academy of Ukraine) used isotopic dating to show that the Boltysh impact occurred 65.2 million years ago, give or take several hundred thousand. Chicxulub is a little older, 65.5 million years, but the dating uncertainties overlapped enough that the two hits might have been nearly simultaneous.

Geologists realize that Boltysh is too small to have played a role in the near-total destruction of life on Earth that did in the dinosaurs, a biological hiatus known as the Cretaceous-Paleogene extinction. (You thought it was "Cretaceous-Tertiary," didn't you? The naming convention got changed in 2004.) Statistically, an asteroid or comet creates a Boltysh-size hole on Earth roughly every million years. Sure, it would have been ugly for anything foraging along the Dnieper River that day, but life elsewhere would not have been affected in a serious way.

So why the renewed fuss? You can dismiss the BBC's headline — Boltysh wasn't found to be riddled with plant-munching alien spores or anything else that would change its status as a secondary blip in the dinosaurs' demise.

Instead, in the August issue of Geology, David Jolley (King's College, Scotland) and four colleagues describe what they found after drilling deep into the sediments that now fill the crater's floor. It turns out that ferns and flowering plants had just begun to flourish in the region's recovering ecosystem — only 2,000 to 5,000 years after the impact — when they were wiped out by the aftermath of Chicxulub's much-bigger blast.

Cosmically speaking, the chance of Earth getting nailed twice in such quick succession by impacts of this size is only about 1 in 1,000, so this was no coincidence. Nor were Boltysh and Chicxulub simultaneous — it wasn't a binary asteroid.

Instead, Jolley and his team (which includes Gurov and Kelley) suggest that something must have stirred up the asteroid belt enough to redirect multiple large bodies Earth's way. Perhaps two large asteroids collided about that time, spraying a shower of fragments throughout the inner solar system, or maybe a clutch of asteroids were yanked into Earth-crossing orbits due to a gravitational resonance with Jupiter.

Whatever the cause, Chicxulub likely resulted from an asteroid of some kind, likely a carbonaceous chondrite, based on the tiny piece of one that UCLA researcher Frank Kyte found a decade ago in a deep-sea drill-core from the central Pacific Ocean. So, just like T. rex and its buddies, the idea that a rogue comet caused the Cretaceous-Paleogene extinction is probably dead too.

And the exoplanet news just keeps on coming.

Two days ago a European planet-hunting team announced finding a Sun-like star with at least five and maybe seven planets, based on the star's complex gravitational wobbles as tracked by the super-precision HARPS spectrograph in the Andes.

Now the science team for NASA's Kepler probe has performed radial-velocity followups at the Keck Observatory confirming that a different Sun-like star, known as Kepler 9, is transited by the silhouettes of two planets. And the team determined an accurate mass for each of them.

But that's just the start. The timing of each planet's transits is changing. The orbital period of one world is slowing down and the other is speeding up. The two planets are gravitationally interacting with each other. Strongly.

They circle the star with periods of 19.2 and 38.9 days. Look carefully at those numbers; they form nearly a 2:1 ratio. That's no coincidence. Objects locked into such orbital resonances with each other are common in our solar system, such as among the moons of Jupiter and among asteroids locked to major planets' periods. Resonances are also proving to be common among extrasolar planets, as more and more multi-planet systems are discovered.

But look again; the orbital ratio is not quite exact. That's normal too. Objects in orbital resonances tend to "librate" (oscillate back and forth) by up to a few percent around the exact numerical value.

Hot Saturns

Kepler 9b and 9c, as they are known, are both gas giants a little smaller and a little less massive than Saturn. The inner one, 9b, weighs in at 0.25 of a Jupiter mass (80 Earths) and the outer one at 0.17 Jupiter mass (54 Earths), with an uncertainty of just a few percent. They orbit 0.14 and 0.22 astronomical units from the star, closer than Mercury orbits the Sun (0.39 a.u.). That means they pass pretty close to each other. And so they should tug on each other significantly.

Sure enough, the team found that the inner planet's orbital period is increasing by 4 minutes per orbit, and the outer one's is decreasing by 39 minutes per orbit. That's a lot. The two planets would soon meet and crash, or go chaotic, unless those values change and reverse periodically. The team estimates, by running simulations, that they oscillate back and forth around the exact 2:1 ratio about every 4 years. That's how the system has survived an estimated 2 billion years or more.

"In addition to the slow change in orbital period," they write in their paper, "the times between successive pairs of transits of Kepler 9b also show an alternating pattern with an amplitude of 2 to 4 minutes." This is due to "the alternating position of the outer planet at the time of transit with respect to the inner planet, and it scales with the mass of the outer body." Again, the whole gravitational picture falls neatly into place.

A Planetary Decoder Ring

All this has lots of implications. At a press conference this afternoon, lead author Matthew J. Holman (Harvard-Smithsonian Center for Astrophysics) stressed that as Kepler finds more and more multiple systems with smaller and smaller planets, transit-timing variations "will be particularly valuable for estimating the masses of small planets." That includes Earth-mass worlds, which are too puny to create a radial-velocity wobble in their stars big enough to measure. (Detailed paper on such multi-planet opportunities.)

Gravitational interactions could also reveal the presence of additional worlds that do not transit their star but tug on those that do.

Moreover, the team writes, "The detailed dynamics of a resonant system probe the system's formation." At the press conference, Alycia Weinberger (Carnegie Institution of Washington) explained why.

It's clear, she said, that exoplanets in resonant orbits didn't form that way but fell into the resonance and became stuck there while migrating in toward their star from farther out. "Planet migration" is expected early in a system's history, when the original protoplanetary disk of gas and dust is still massive enough to exert a gravitational effect. Migration can also occur somewhat later, if planets interact with large numbers of small bodies such as asteroids or Kuiper Belt objects. Some degree of migration is strongly suspected in our own solar system's early history.

A Super-Earth too?

There's more. In addition to Kepler 9's two confirmed giants, the team also identified signs of a third, much smaller body that also transits the star much closer in. It's perhaps 1.5 Earth diameters in size and seems to cross the star every 1.6 days, implying a distance from it of only 0.027 a.u. If it's real, it's broiling at a distance of just a few times the star's own radius. More observations are needed to confirm it. A hot super-Earth of this diameter would probably possess 3 or 4 Earth masses of rock and iron .

Kepler 9 is a G2 star about 2,300 light-years away in Lyra. It shines at a very dim magnitude 13.9, currently almost straight overhead (as seen from North America and Europe) in the early-evening sky.

Among the world's professional observatories, the one in Big Bear, California, is unique.

First, it's located in a lake — not along a lake, but in it! This was Caltech astronomer Harold Zirin's idea. In the late 1960s he wanted to build a world-class facility for studying the Sun, and he was attracted to the clear stable air over Big Bear Lake high in the mountains about 100 miles east of Los Angeles. Zirin equipped his pride and joy with a trio of scopes having apertures of 8 to 25 inches (20 to 65 cm).

Second, it's one of three observatories that Caltech gave up. (Do you know the other two? If so, leave me a comment!) In 1997 this venerable bastion of science and engineering turned over Big Bear's keys to the New Jersey Institute of Technology, which promptly dedicated the facility to honor Zirin, who'd managed it for some 30 years.

Third, Big Bear Solar Observatory (BBSO) is home to the world's largest solar telescope (until the Advanced Technology Solar Telescope comes online later this decade). Last October, NJIT finished a five-year overhaul that brought in a state-of-the-art telescope with a clear aperture of 63 inches (1.6 m), actuators to contort the primary mirror for optimum sharpness, and an off-axis f/52 design that provides an unobstructed light path.

Finally (and here's the point of telling you all this), Big Bear's big new telescope has now taken its official "first-light" image, at right — and it's amazing. Sunspot number 1084 didn't look all that special when it crossed the solar disk eight weeks ago — check out the small image below it, acquired by a camera on the SOHO spacecraft.

But the BBSO version, taken July 2nd, provides a wholly different perspective. According to an NJIT press release, the resolution is about 50 miles (80 km). To give you a sense of scale, the spot's dark center (its umbra) is roughly the diameter of Earth. It's surrounded by a lighter-colored penumbra. The spot sits lower than the surrounding photosphere, and recent research suggests that below each sunspot is a self-sustaining vortex of magnetic-field lines (a little like terrestrial hurricanes in that respect).

The textured stuff all around the spot, termed granulation, is the pattern of Alaska-size bubble of hot gas bringing the Sun's energy to the top of the photosphere, where it radiates to space as light and heat. Think "pot of boiling oatmeal," and you'll get the picture.

Sunspots are typically about 3,000° to 4,000°F cooler than their surroundings, but they're still plenty hot enough to be brightly incandescent. So why do they look dark? Because luminosity is proportional to the fourth power of temperature. Cool the Sun's surface by a third, and its brightness drops by 80%.

A companion image, this one recording the red hydrogen-alpha emission at 656.3 nm (6563 angstroms), probes a region about 600 miles (1,000 km) higher up, in the chromosphere. It was taken July 1st and shows the same sunspot at upper left.

Philip Goode, the observatory's director, comments: "Around the bright sunspot edges are black fibers that look like strands of hair" but in fact they're jets of energized plasma being ejected upward. "What’s interesting," Goode adds, "is that when we look in visible-light, the sunspot appears pretty benign. However, this shows the real dynamics of the magnetic region and the jets exploding from the sunspot’s edges."

To close, I need to confess something. Zirin won't remember this, but he once gave me a job when I was an undergrad at Caltech — and it was the easiest job on the planet. Once every hour I had to climb to the roof of the (now-demolished) Robinson building, check the status of a solar telescope he had running, and take a quick series of calibration images. It took 5 minutes tops. The rest of the hour I could do anything I wanted: usually that involved eating, sleeping, flirting with secretaries, or goofing off — but rarely, if ever, studying!

Nestled in the Chilean Andes at altitude of 7,900 feet (2,400 m), the European Southern Observatory's 3.6-m reflector at La Silla is neither the highest nor the largest telescope in the region. Far from it. However, coupled with the incredible HARPS spectrograph, this telescope is cranking out discoveries of extrasolar planets faster than any other observatory on Earth.

Today, at a gathering of planet-hunting astronomers in France, Christophe Lovis (Geneva Observatory) announced that his team has identified a solar system packed with planets — five for sure, and probably seven — using the La Silla facility. It's the most populous exoplanet system known.

The central star is HD 10180, a type G dwarf situated 137 light-years away in the southern constellation Hydrus. It's one of 400 nearby Sunlike stars that astronomers have been monitoring from La Silla for years. HARPS can't see these worlds directly; instead it detects minuscule Doppler shifts in the stars' light, caused by back-and-forth wobbles in their motion that, over time, reveal the presence of planets circling around them. In the case of HD 10180, the telescope amassed 190 nights of observations over six years.

You could make a case that spotting alien planets has gotten a little ho-hum — after all, the total count (including those orbiting the Sun) now tops 500, and 15 systems involve at least three planets.

But HD 10180 definitely raises the bar. Its five sure-things, dubbed C, D, E, F, and G, have Neptune-class masses 13 to 25 times that of Earth. But all five are quite close to the star, in orbits that range from 0.06 to 1.4 astronomical units (5½ to 130 million miles out). So much mass packed so close together is bound to incite gravitational tussles among them, and future observations will follow the long-term evolution of the system.

But wait — there's more! Lovis and his team are fairly certain there's a sixth planet, H, with at least 65 Earth masses (making it Saturn-ish) and orbiting 3.4 a.u. from the star. There's also strong evidence for a seventh sibling, B, zipping just 0.02 a.u (2 million miles) from the star. Although not yet confirmed, this innermost planet might be very close to Earth in mass. It causes a wobble in HD 10180 only about 2 miles (3 km) per hour — "slower than walking speed," notes team member Damien Ségransan — and is thus very hard to measure.

For all the details, read the team's article in the current issue of Astronomy & Astrophysics. At upper right is Figure 13, a concise comparison of solar systems with three or more planets (one is missing, however: the four-member set circling pulsar PSR 1257+12).

Now that we know of a system as crowded with planets as our own, isn't it about time we starting finding some that resemble Earth? That bar-raising exoplanet discovery may not be long in coming — NASA's Kepler spacecraft is looking for them right now.

Amateur astronomy lost one its most iconic figures today. Jack Horkheimer, known to millions as public television's ebullient "Star Gazer," died this afternoon at age 72. The exact cause of death was not disclosed, though he had battled chronic respiratory problems for decades.

Horkheimer had been a fixture at the Miami Planetarium for more than 45 years, where he began as a volunteer and served as its executive director since 1973. But he'll be remembered most for his exuberant and often zany television persona, who helped us all appreciate the breadth and depth of eyeball-only astronomy.

The show started airing locally on WPBT in Miami, then went national in 1985. Along the way his nom de television morphed from "Star Hustler" to "Star Gazer," to sidestep aggressive web-browsing filters.

The shows are distributed free, via satellite to more than 200 stations across the U.S. and to other outlets like the Armed Forces Network. You can download any of the past year's episodes as well. Since Horkheimer and longtime planetarium colleague Bill Dishong produced several episodes in advance, the last one to feature Horkheimer — his 1,708th — will air the first week of September and feature the Summer Triangle. As always, he begins with a chortling "Greetings, greetings, fellow stargazers and ends with his signature phrase "Keep looking up!"

Beyond the enthusiasm he projected over the air waves, Horkheimer had encouraged kids to get involved in astronomy, most notably through annual $1,000 awards given to aspiring young amateur astronomers through the Astronomical League.

It's not yet clear how or if his show will continue. Tony Lima of the Miami Science Museum, home to the planetarium, says the staff is still trying to make sense of Horkheimer's passing, adding, "We at the Museum all feel this loss quite a bit." At least one month of shows will be hosted by Chris Trigg, another staffer at the Miami facility.

Horkheimer's inspiration will live on. In 2007 Cricket Books published a collection of comic strips (first seen in Odyssey magazine) featuring his madcap take on viewing the sky. Colorful to the end, "Horky" offers this amusing, self-penned epitaph in his online bio:

"Keep Looking Up was my life's admonition,
I can do little else in my present position."

At one point during the Apollo 17 mission, moonwalking astronauts Gene Cernan and Harrison "Jack" Schmitt tried to drive their lunar rover up the face of a 200-foot-high rise known as the Lincoln-Lee Scarp. It didn't seem that imposing a task, but the rover's wheels slipped so much that the astronauts were forced to climb it at an angle, much as a sailboat tacks into a stiff wind.

Lincoln-Lee is the kind of feature created when one slab of rock overrides another due to horizontal compression (what geologists term a thrust fault). On Earth, good (if enormous) examples of thrust faults occur where crustal plates collide — think how the towering Andes rim the west coast of South America, and you get the idea.

What Cernan and Schmitt couldn't have known back in 1972 is that Lincoln-Lee is not an isolated feature but one of likely hundreds of small thrust faults all over the Moon. That revelation came to light only recently, thanks to the incredibly detailed images of the lunar surface being beamed to Earth by two Narrow Angle Cameras aboard NASA's Lunar Reconnaissance Orbiter. (These same cameras have taken snapshots of the historic Apollo 11 landing site and others.)

It wasn't until LRO arrived on the scene that geologists realized the subtle fractures are pervasive. After poring over images from LRO, a team led by Thomas Watters (Smithsonian Institution) has identified 14 new scarps in addition to the three dozen already known. As the map here shows, half of the new finds are poleward of 60° in latitude. (Most of the previously recognized scarps had been spotted by cameras mounted into the orbiting command modules of Apollos 15, 16, and 17 — but these craft never strayed far from the lunar equator.)

In the August 20th issue of Science, the researchers reach a startling and unexpected conclusion: "We have now found that these lobate scarps occur everywhere on the Moon," Watters explains, "which means the Moon has been contracting or shrinking globally."

All told, the lunar diameter hasn't changed much, probably only about 700 feet (200 m). But the scarps look so fresh that they must have formed in the recent past, geologically speaking. "These scarps can't be any older than 800 million to 1 billion years," Watters noted during a press briefing yesterday, and they could be much younger. "We're finding the Moon is a truly dynamic planet," adds Michael Wargo, chief lunar scientist at NASA headquarters. "Who'd have thought that tectonic processes would still be occurring today?"

The scarps escaped notice until now because they're only a mile or two long and just tens of feet high — completely invisible to backyard telescopes and even to previous lunar-orbiting craft. Most likely, they result from the gradual contraction of the lunar interior as it cools, a process that apparently didn't end when the last maria filled with lava some 3 billion years ago.

Thrust faults appear on the surfaces of Mars and especially Mercury, but they're huge by comparison. Some of the Mercurian scars are hundreds of miles long and more than a mile high, implying that the planet shrank by at least a couple of miles as its molten interior cooled and contracted.

Yet at one time the Moon must have been really, really hot as well. After all, it likely accreted by picking up the white-hot pieces after something enormous collided early on with Earth. So shouldn't there likewise be giant thrust faults jutting skyward across lunar landscape? Some researchers think the Moon did undergo substantial contraction, but the surface scars from that have been erased over time. Watters thinks otherwise. "Our results are really more consistent with a cooler initial starting temperature," he explains, "one that didn't allow the entire Moon to melt."

As I listened to yesterday's press briefing, I wondered what Cernan and Schmitt were thinking as they struggled up the slope of Lincoln-Lee Scarp all those years ago. So I asked one of them.

"We were well aware of the Lee-Lincoln scarp and that it is a potential thrust fault or wrinkle ridge," Schmitt recalls. "We drove up it to Station 2 at the base of the South Massif, and along and down it going to Station 4 [Shorty crater]. It was entirely covered by a light mantle or avalanche deposit. The avalanche probably flowed off the South Massif about 100 million years ago, as it appears to have been triggered by [nearby impacts from] Tycho ejecta. Lee-Lincoln would be at least older than the avalanche and I suspect much older than that."

Watters and other lunar geologists should eventually be able to say more about how and when all these lobate scarps formed. As of now, LRO has mapped only about 10% of the lunar surface at high resolution. But give it another three years (assuming the funding holds out), and there'll be enough coverage to inspect the entire lunar glove down to a resolution of just a few feet.

You can read NASA's press release here, and learn more about LRO's incredible cameras here.

The notion that a massive object can literally bend light, what we now call gravitational lensing, has been around for more than 200 years — though Einstein gets the nod for making the effect widely known and getting it right.

Ever since the 1979 discovery of a distant quasar "lensed" into two images by an intervening galaxy, observers have amassed all sorts of gravitationally mangled novelties — none more famous than QSO 2237+0305, the Einstein Cross. By carefully dissecting these cosmic mirages, cosmologists can learn much about the lensing objects in the foreground, such as how much unseen dark matter is fortifying their mass, and about the distances to the farther objects being distorted.

Now a group headed by Eric Jullo (Jet Propulsion Laboratory) and Priyamvada Natarajan (Yale) has used the light-bending power of the massive galaxy cluster Abell 1689 to refine our conceptions about the mysterious, antigravity-like phenomenon called dark energy.

In August 20th's Science, these researchers describe how they used images of Abell 1689 from the Hubble telescope's Advanced Camera for Surveys to identify 114 visible manifestations of 34 different background galaxies. Then Keck and Very Large Telescope spectrographs pinned down distances to 24 of those galaxies.

The team used these observations not only to reconstruct the paths taken by light from each background galaxy, but also to model how dark energy altered the geometry of space along the route. “The precise effects of lensing depend on the mass of the lens, the structure of spacetime, and the relative distance between us, the lens and the distant object behind it,” Natarajan explains in a press release about the results.

The goal was to tighten the constraints on the dark-energy density in the universe. There's much more to the universe than the normal "stuff" (consisting of protons, neutrons, and electrons) that we can see or sense. Cosmologists currently favor a universe in which this baryonic matter is merely 4.5% of all matter, with as-yet-unidentified dark matter adding another 22%.

The remaining 73%, they believe, is accounted for by the "dark energy" that's making the expansion of the universe speed up — and the leading candidate for that is something dreamed up by Einstein in the 1920s as a fudge factor for general relativity, now termed the cosmological constant and abbreviated Λ (Lambda).

(Trust me: no one-liner at a star party will prove your astro-smarts faster than uttering, "Why, yes — I do support a Lambda-cold-dark-matter cosmology.")

Jullo, Natarajan, and their colleagues find that cosmologists' assumptions about the ΛCDM's "equation of state" are reasonably well matched by their observations of Abell 1689. In that sense, nothing's new. Prior results using Type Ia supernovae and other approaches likewise support a ΛCDM cosmology (that is, that the dark energy's equation of state, known as w, is exactly equal to –1). But the Abell 1689 work represents a new and arguably more robust way to get there. "We have to tackle the dark energy problem from all sides,” Jullo notes in a second press release. "It’s important to have several methods, and now we’ve got a new, very powerful one.” They say they've narrowed the value of w to –1 to an uncertainty now of just 7%, including others' work with theirs.

As they conclude in their full paper (warning: not for the fainthearted!), it's a technique that will get even better once observations of ultra-distant objects start rolling in from the forthcoming James Webb Space Telescope.

Just five years ago the first hypervelocity star was confirmed, by Warren Brown of the Harvard-Smithsonian Center for Astrophysics. Now about 16 are known. These are stars moving through space so fast, upwards of several hundred kilometers per second, that they will escape the Milky Way's gravity and forever roam the intergalactic void. Their discovery had to wait for very efficient surveys; only about one in 100 million stars is going so fast.

Several possible mechanisms can fling a star with that much speed. But the most productive of them seems to be happening at a single, very special place. If a binary star falls close enough to the supermassive black hole at the Milky Way's center, the binary can be disrupted in such a way that one star is trapped around (or in) the hole and the other is slung away with preternatural velocity. This is thought to account for most of the escaping 16.

One of them, known as HE 0437–5439, is already 200,000 light-years out near the Large Magellanic Cloud, way beyond the usual definition of the Milky Way's limits. Brown and six colleagues have published a new study that presents a complex picture of its nature and history.

Other astronomers had argued that it probably came from the Large Magellanic Cloud (LMC) itself, rather than the Milky Way, based on the star's chemical makeup. Brown's group has laid that scenario to rest by measuring the star's proper motion on the sky for the first time. Two high-resolution Hubble images taken 3.5 years apart show that it's moving away not from the LMC, but from the Milky Way's center in Sagittarius.

The star is departing at 723 km per second as measured with respect to the Sun. Before it climbed out of the Milky Way's gravitational well, it must have been going 820 km/sec with respect to the galaxy. Even so, it must have taken 100 million years to get where it is now.

And that's a problem. Its spectrum shows it to be a young, main-sequence star of type B with about 9 solar masses. Such a massive main-sequence star can't be more than about 20 million years old.

Brown's group proposes an answer: the star was born near the Milky Way's center as a triple, consisting of a tight binary and a more distant third star. The third was the one captured by the black hole; the tight binary was flung off. As it raced out of the Milky Way, one or both of the binary's stars evolved to swell and engulf the other. The result was a "newborn" single star known as a blue straggler. Blue stragglers have long been familiar in globular clusters, where stellar encounters and mergers are fairly common, and elsewhere.

The team is now trying to determine the origins of four other hypervelocity stars on the fringes of the Milky Way. "We are targeting [other] massive B stars," says Brown. "These stars shouldn't live long enough to reach the distant outskirts of the Milky Way, so we shouldn't expect to see them there. The density of stars in the outer region is much less than in the core, so we have a better chance to find these unusual objects."

They sure can run, but nowadays they can't hide.

Here's the group's paper.

For any of you who've agonized about dropping $1,000 or more on a new telescope, consider how much professionals worry about where they'll get money for the seriously expensive toys needed to advance the frontiers of astronomy. To pick just one example, the proposed Thirty Meter Telescope has an estimated price tag of nearly $1 billion. Cutting-edge discoveries don't come cheaply.

So where does the money for such megaprojects come from? Among U.S. agencies, NASA provides the lion's share, about $1.1 billion per year. The National Science Foundation chips another $250 million, though right now much of its "new" money is funding construction of the ALMA radio-telescope array in Chile and the Advanced Technology Solar Telescope (ATST) in Hawaii.

OK, then who decides which projects get federal funding? Since the 1960s, that task has fallen to the National Research Council, an arm of the U.S. National Academy of Sciences that periodically assembles a panel of A-list astronomers to assess what projects would get the most bang for the U.S. buck in the coming decade.

It's hard to understate how critical these reviews are the budgeting process. "Nothing is more important to our discipline than the release of the decadal survey recommendations,” says Kevin Marvel, executive officer for the 7,000-member American Astronomical Society. When the one for the 1990s came out, Sky & Telescope devoted nine articles and 54 pages to the conclusions!

Don't worry: I'm not going to write anywhere near that much about Astro2010, the sixth in the NRC's series of astronomy assessments, which debuted last Friday, August 13th. It details a plan of attack for the period 2012-21 — with an eye toward laying the foundation for 2022-31. The massive summary report, written by a 23-member committee chaired by Stanford cosmologist Roger Blandford, has been in the works for nearly two years. All told, 123 experts on nine topical panels sifted through 324 white papers touting various ground- and space-based projects. You can download the full report, New Worlds, New Horizons in Astronomy and Astrophysics, as a free PDF; a printed copy will set you back $39.95 once it's published in final form.

Blandford's charge was to find the best mix of projects to tackle three key scientific objectives: searching for the first stars, galaxies, and black holes; seeking nearby habitable planets; and advancing understanding of the fundamental physics of the universe. As expected, the committee urges strong continued (or increased) support of already-approved programs and basic research. But it also looked at supporting unrealized "honorable mentions" from past decadal assessments.

The winners, if you will, fell into categories with large (exceeding $1 billion), medium ($300 million to $1 billion), and small budgets. Here they are, as ranked in priority by the committee, along with the estimated costs (not all of which may involve U.S. federal funding):

Large-scale space-based efforts:

• Wide-Field Infrared Survey Telescope (WFIRST): an observatory with a 1.5-m mirror, would be placed far from Earth at the L₂ Lagrangian point. It would tackle two of the most fundamental questions in astrophysics: Why is the expansion rate of the universe accelerating? And are there other solar systems with worlds like Earth? ($1.6 billion)
  
  
• NASA's Explorer Program: a plan to augment the space agency's long-running satellite program, so that modest-cost missions can be developed rapidly to respond to new scientific and technical breakthroughs. ($463 million)
  
  
• Laser Interferometer Space Antenna (LISA): a low-frequency gravitational-wave observatory, developed jointly by NASA and the European Space Agency, that will open an entirely new window on the cosmos. LISA will measure ripples in space-time caused by exotic sources like white dwarfs and black holes. ($2.4 billion)
  
  
• International X-ray Observatory (IXO): a powerful X-ray telescope that will transform our understanding of hot gas associated with stars and galaxies in all evolutionary stages. ($5 billion)
  

Medium-scale space-based efforts:

• New Worlds Technology Development Program: designed to establish the technical and scientific foundation for a future mission to study Earthlike planets. ($100 to 200 million)
  
  
• Inflation Probe Technology Development Program: a program to prepare for a mission to study the cosmic microwave background mission and the epoch of inflation. ($60 to 200 million)
  

Large-scale ground-based efforts:

• Large Synoptic Survey Telescope (LSST): a wide-field telescope, optimized for variable sources, to address broad questions that range from asteroids and comets that threaten Earth to the nature of dark energy. ($465 million)
  
  
• Mid-Scale Innovations Program augmentation: a program designed to provide the capability to respond rapidly to scientific discovery and technical advances with new telescopes and instruments. ($93 to 200 million)
  
  
• Giant Segmented Mirror Telescope (GSMT): a large optical and near-infrared telescope that will provide a spectroscopic complement to the James Webb Space Telescope (JWST), the Atacama Large Millimeter Array (ALMA), and LSST. ($1.1 to 1.4 billion)
  
  
• Atmospheric Čerenkov Telescope Array (ACTA): permits U.S. participation in an international effort to study very-high-energy gamma rays. ($400 million)
  

Medium-scale ground-based efforts:

• Cerro Chajnantor Atacama Telescope (CCAT): an 80-foot (25-m) submillimeter telescope that will complement ALMA by undertaking large-scale surveys of dust-enshrouded objects. ($140 million)
  

Add these up, and it totals some $12 billion over 2012-21 time frame. And that doesn't factor in ongoing big-ticket items like the James Webb Space Telescope. Nor does it includes priorities for planetary science and for solar and space physics, the subjects of separate decadal assessments (here and here) under way right now. Unless NASA and the NSF somehow win the federal-budget lottery, many of these programs won't be funded — nor will scores of other worthwhile research efforts that didn't make the committee's cut. There'll be a few winners and plenty of losers.

Of course, setting such priorities — along with making a strong case for supporting astronomical research generally — is the whole point of the exercise. It's a tough job, but I'm glad somebody's doing it.

First came SETI@home, which enabled millions of people to sign up their computers to sift through radio-telescope data for alien transmissions from the stars. Now 11 years old and running stronger than ever, SETI@home has opened the way for about 50 similar distributed-computing projects — in molecular biology, climate modeling, quantum chemistry, chess problems, and other number-crunching endeavors. Most of these run through BOINC, the Berkeley Open Infrastructure for Network Computing, which makes it easy to choose projects to join. A few clicks download the software and it runs out of sight, usually when your computer is in screensaver mode. Fancy displays are often available if you want to see what's going on.

Several of these projects involve astronomy. One called Einstein@Home started by examining data from the LIGO gravitational-wave observatory, looking for certain subtle signatures of spacetime ripples that might have escaped initial notice. Last year Einstein@Home expanded to took through radio data from an ongoing pulsar hunt at the Arecibo dish in Puerto Rico, using an algorithm that's especially sensitive to pulsars circling in very fast orbits around other objects. A quarter million people have installed Einstein@Home on their computers.

On June 11th Einstein@home made its first discovery: a pulsar drifting through space all by itself about 17,000 light-years away in Vulpecula. Designated PSR J2007+2722, it’s a previously unknown neutron star spinning 40.8 times per second. It seems to be a rare case of an old pulsar that was spun up by gaining mass from a companion that either blew up long ago or was eaten completely. It's the fastest such spinner on record.

The discovery took place on a computer running in the basement of Chris and Helen Colvin of Ames, Iowa. Three days later it was confirmed on a computer owned by Daniel Gebhardt in Mainz, Germany. It then brought itself to human attention.

About 2,000 pulsars are currently known. The project’s “holy grail,” says Cornell radio astronomer Jim Cordes, would be a pulsar orbiting something with a period of less than an hour. That would allow new tests of Einstein’s general relativity, the project's longterm goal.

Every year awards are given to high-achieving members of our community, so let's take a moment to applaud them and their stellar contributions to amateur astronomy.

Most recently (August 6th), the International Astronomical Union's Central Bureau for Astronomical Telegrams (CBAT) announced that four amateurs share this year's Edgar Wilson Award. Established in 1998 and administered by the Smithsonian Astrophysical Observatory, this award goes to those dedicated observers lucky enough to spot a comet using amateur-grade equipment. Here's the list of winners, who will split the prize money equally:

• Don Machholz discovered an 11th-magnitude comet from his California home on March 23rd using an 18-inch (0.47-m) f/4.8 reflector at 77×. As with his 10 previous comet discoveries, Machholz spotted C/2010 F4 by eye!
  
  
• Jan Vales (Slovenia) identified a 12.6-magnitude periodic comet, P/2010 H2, on images taken April 16th with a 24-inch (0.6-m) f/3.3 reflector.
  
  
• Rui Yang and Xing Gao (China) discovered P/2009 L2 on images taken June 15th by Gao using nothing fancier than a Canon 350D camera and a 107-mm f/2.8 lens. At the time it was 14th magnitude.
  

Harvard-Smithsonian astronomer Daniel Green, who's coordinated the Wilson award for many years, notes that all but one of the last 13 amateur comet discoveries utilized digital imaging. Machholz's C/2010 F4 was the first found with eyes alone since David Levy spotted P/2006 T1. "There were no visual discoveries in 2003, 2005, or 2007-09," Green notes. "But during 2000-02, there were 11 visual discoveries of seven comets — compared to only two using CCDs in that same 3-year span! Changing times!"

CBAT's announcement about the Wilson Award comes close on the heels of the Astronomical Society of the Pacific's annual meeting. On August 3rd, at the ASP's annual banquet, Allan Rahill accepted this year's Amateur Achievement Award. At the Canadian Meteorological Center, Rahill and colleague Attila Danko maintain the Clear Sky Clock Chart website that has become an invaluable tool for observers throughout North America.

Also honored by the Society were science writer Marcia Bartusiak, winner of the Klumpke-Roberts Award for her contributions to the public understanding and appreciation of astronomy; and Wayne "Skip" Bird, whose efforts as an ambassador for astronomy in schools earned him the Las Cumbres Amateur Outreach Award. Several others received awards for their work in education and outreach; read about them all in the Society's press release and see their pictures here.

Two months ago I headed to Tucson, where the Astronomical League held it annual convention. The League, and especially incoming president Carroll Iorg, has taken the lead in promoting amateur activity among a new generation of stargazers. To that end, a highlight of this year's gathering was the presentation of the National Young Astronomer Award, which recognizes achievements by top high-schoolers in the U.S., and the Jack Horkheimer Award, given to youngsters whose time and talents have helped the League or one of its 240 member societies.

Competition was especially keen for this year's NYAA, notes Iorg, with more entries than he's seen in many years. The submitted projects were judged by trio of professional astronomers.

The first-place finisher, Andrew Hitchner of Norristown, Pennsylvania, explored the relationship between the temperature of a star and the strength of hydrogen's Balmer absorption lines in the star's spectrum. He recorded stars of various spectral types with an 8-inch Meade LX200 telescope and then analyzed their spectra. Hitchner's results supported, at least in part, his hypothesis that lower temperatures correlate with weaker line strength — though he discovered that superhot O-type stars don't have strong hydrogen lines either.

Hitchner will have a tougher equipment choice for his next observing project: as the top NYAA winner, he received an Explore Scientific ED 127 refractor on a Twilight II mount from sponsor Scott Roberts.

Taking second place this year is Tongji "Youyou" Li, who lives in Hershey, Pennsylvania. To assess the threat posed by near-Earth asteroids, she wrote a computer program to determine their orbits and the risk they pose. Third place goes to Erika Tinley of Tucson, Arizona, whose project was entitled "The Geometry of Active Galactic Nuclei as Evidenced by Their Emission Line Spectra."

I can't do justice here to the amazing work these three students and their fellow entrants, or to the other prizewinners noted below. But be sure to check out Iorg's summaries in a forthcoming issue of The Reflector.

The Horkheimer award, generously sponsored by one-of-a-kind stargazer Jack Horkheimer, is actually a series of recognitions for youth service to astronomy. This year's recipients are:

• Horkheimer/Smith Award (honoring Arthur P. Smith Jr.): Christian Borao of Stevenson Ranch, California, who for the past three years has had a major role in the Astronomy Day activities of the Local Group Astronomy Club. He received a $1,000 check and a Celestron NexStar 130SLT telescope.
  
  
• Horkheimer/Parker Award (honoring planetary imager Don Parker): Caroline Moore of Warwick, New York, who discovered two supernovae while a member of the Rockland Astronomy Club. (You might recall her standing alongside President and Mrs. Obama during last year's White House Star Party.)
  
  
  

  Caroline Moore, a junior at Warwick Valley High School, already has two supernova discoveries to her credit. She is the 2010 winner of the Astronomical League's Horkheimer/Parker Award.

  R. E. Moore / Deer Pond Observatory
• Horkheimer/D'Auria Award (honoring Tippy D'Auria of Winter Star Party fame): Catlin Ahrens of Fairmont, West Virginia, who joined the Central Appalachian Astronomy Club at age 10 and last year was a first-place winner in the West Virginia State Science and Engineering Fair.
  

Speaking of science fairs, back in May the ASP presented high-school seniors Andrei Nagornyi (Staten Island, New York) and Evan Fletcher (Galesburg, Michigan) with its Priscilla and Bart Bok Awards at the Intel International Science and Engineering Fair in San Jose, California. Read about these students' incredible research projects here.

Finally, I'd be remiss if I didn't acknowledge an award presented last January to Robert Stephens. The Chambliss Amateur Achievement Award is perhaps the highest honor a backyard stargazer can attain — because it's bestowed by the American Astronomical Society at its annual winter meeting. Stephens, a certified public accountant in Rancho Cucamonga, California, is best known for his involvement in the annual RTMC Astronomy Expo and the Society for Astronomical Sciences. But did you know that this avid eclipse-chaser has published more than 100 research articles? His specialty is asteroid photometry.

OK, I think that's it — did I miss anyone? Congrats to all this year's winners! You make us proud to be called "amateur astronomers."

We're in the midst of the 40th anniversaries of the six Apollo landings; the last, Apollo 17's, comes in late 2012. It's hard to imagine that we might still be making fundamental discoveries about the Moon from the study of the dusty rocks hauled back to Earth all those years ago, but consider the following.

In the past weeks, two new analyses of Apollo samples have appeared in competing but equally prestigious journals. The articles themselves were competing too: one claims that at least some of the lunar interior contains as much water as do the lavas now oozing out along Earth's mid-ocean ridges, while the other asserts that on the whole the Moon must be very, very, very dry. It's too early to know who's right — perhaps both are — but here's why the eventual correct answer has major implications for solar-system history and the Moon's formation in particular.

Most planetary scientists now accept that a Mars-size object whacked the just-formed Earth so hard that much of our young planet's mantle, and most of the impactor, spurted into orbit as white-hot rock vapor that eventually condensed and collected into that big, beautiful, solitary satellite of ours. The Moon ended up both very much different from Earth (it's nearly iron-free, for example) yet very much like it (the two bodies' ratios of oxygen and chromium isotopes are identical).

Frankly, geophysicists still wrestle with how conjure up a Moon made in part from Earth materials and yet have its rocks — as the Apollo samples initially showed — utterly devoid of water in any form. There are ways to make this stark chemistry work out: for example, Earth might have started out completely dry as well, and then amassed its water later after being hit by countless comets and water-rich asteroids. But the geochemical recipe would be a lot easier to follow if we knew, with certainty, just how much water ended up in the Moon.

So is the lunar interior wet or dry? On the "wet" side of this debate are a few research teams who've found water in volcanic glasses and in a mineral called apatite. The chemical formula for apatite is Ca₅(PO₄)₃(F,Cl,OH). It looks messy — and it is. Apaptite is a "dreg" in the rock-forming process, a mineral that sops up leftovers that none of the other rock minerals wanted. Water, in the form of hydroxyl (OH), is one of those leftovers.

Writing in the July 22nd issue of Nature, Caltech's Jeremy W. Boyce and six colleagues describe their study of apatite grains found in a particular sample returned by Apollo 14's astronauts.

Using a sensitive ion mass spectrometer, they found abundant hydrogen (derived from hydroxyl), chlorine, and sulfur — enough of it, in fact, to be "essentially indistinguishable" from apatite crystals found in rocks derived from Earth's upper mantle.

So might portions of the lunar mantle or crust are more volatile rich than previously thought? If so, geophysicists could take a slightly more relaxed approach to formulating a Moon from the primordial smash-up's debris.

However, a counterpoint favoring a bone-dry Moon appeared just two weeks later, in August 5th's edition of Science Express. A team led by Zachary Sharp (University of New Mexico) argues that the Moon is exceeding dry, using roundabout evidence from the abundance of chlorine's two isotopes.

Sharp hadn't gone looking for this result. He and others had studied the ratio of chlorine-35 and slightly heavier chlorine-37 in wide range of planetary samples. They'd found a consistent story: the two isotopes were always about equal in Earth rocks and nearly so in meteorites, with very consistent results that never varied by more than 0.5%.

But when they assayed the chlorine in lunar rocks, the numbers were all over the place — a range of ratios "so ridiculously large," Sharp recalls, that he thought their measurement technique was seriously flawed. However, it wasn't. In particular, the lunar rocks they studied contain up to 25 times more chlorine-37 than chlorine-35. "The only way to get this high range of Cl isotopes," Sharp explains, "is if in the Moon is anhydrous," that is, water-free.

Here's his thinking: In a bubbling pot of magma on Earth, the lighter chlorine isotope would boil off more readily. But that's neatly balanced out by the strong preference of chlorine-37 to bond with hydrogen to create HCl, which also boils away readily. In this isotopic match-up, the result is a draw.

However, remove hydrogen (a.k.a. water) from the mix, and the chlorine-37 has no way to escape. It's forced into end-of-the-line minerals like apatite, salts, and metal chlorides, but the chlorine-35 flies off into space. The result would be compositions strongly biased toward the heavier chlorine isotope — just what Sharp's team found.

Might some other process be skewing the ratio? The researchers looked at all the possible candidates, including eons of exposure to the solar wind, but in the end the "dry-Moon" seems the only plausible cause.

This facinating scientific tug-of-war is still in the early going. Remember: we have well-selected samples from only nine locations on the Moon (if you include the three small staches returned by the Soviet Union's Luna landers). How would you like the job of deciding how Earth formed if you could pick rock samples from only nine spots on our vast planet? It wouldn't be easy.

After oversleeping for more than a year, our star is finally stirring from hibernation. Experts don't expect solar activity to peak until until mid-2013 (and a weak one at that), but the signs of awakening are clearly evident.

A few days ago the Sun let loose with a massive belch. On August 1st at 8:55 Universal Time, orbiting satellites witnessed a sizable flare erupting from the large sunspot region designated 1092. The strength of this outburst was pegged at C3, modest as flares go, but it still triggered an impressive coronal mass ejection, or CME, that shot out from the solar disk at more than 600 miles (1,000 km) per second. Watch the amazing video from NASA's STEREO spacecraft here.

When the flare erupted, NASA's recently-launched Solar Dynamics Observatory also looked on as the magnetic disturbance caused an enormous filament of superheated gas to pulse across the Sun's disk. More amazing video, this one from SDO, is here.

All this tumult occurred on the Earth-facing side of the Sun, and skywatchers at far northern and southern locations briefly enjoyed colorful auroral displays on the night of August 3-4.

The Sun has since quieted down, but the big spot in region 1092 has been joined by a second, smaller group (1093) that rotated into view yesterday. Go have a look — but, as always, never try to look at the Sun by eye or using optical aid without using a safe solar filter.

Meanwhile, when the Sun's activity finally does peak, solar physicists will have more spacecraft at their disposal than ever before — despite the news that NASA managers pulled the plug on the Transition Region and Coronal Explorer (TRACE) on June 21st after 12 years of operation.

The workhorse Solar and Heliospheric Observatory (SOHO), a collaboration between NASA and the Rueopean Space Agency, just keeps on chugging (it's nearly 15 years old). Even with the loss of TRACE, NASA still has SDO, STEREO, and ACE (Advanced Composition Explorer) in its arsenal of orbiting sentinels. (By the way, teh STEREO team has a great iPhone app showing the Sun in 3D.)

In addition, the Japan Aerospace Exploration Agency continues to receive great high-resolution images from its Hinode spacecraft.