Don Pettit / NASA

This is a composite of 18 time-exposure images photographed from a mounted camera on the International Space Station, from approximately 240 miles above Earth. The image is filled with star trails and spiraling reflections from the space station's solar arrays.

Flying on the International Space Station is the world's biggest high, and a series of psychedelic time-exposure images engineered by NASA astronaut Don Pettit proves it.

This picture, showing the station's truss structure in the foreground and Earth's airglow in the background, is actually a composite of 18 different exposures. A couple of other pictures in the series step things up a notch by putting together 47 exposures. Here's Pettit's explanation of the process, as laid out in the NASA Twitter gallery:

"My star trail images are made by taking a time exposure of about 10 to 15 minutes. However, with modern digital cameras, 30 seconds is about the longest exposure possible, due to electronic detector noise effectively snowing out the image. To achieve the longer exposures, I do what many amateur astronomers do. I take multiple 30-second exposures, then 'stack' them using imaging software, thus producing the longer exposure."

This isn't the only experiment Pettit has been conducting during his stint on the space station. A wide variety of scientific tests are under way in orbit, ranging from studies of human health in zero-G to the chemistry of Scotch whisky in weightlessness. Pettit has shown off some pretty trippy experiments in a couple of space station videos, including the creation of antibubbles within bubbles and the sight of sonic water droplets rockin' out to the sounds of ZZ Top. As Pettit says in one of the videos: "Oh, wow!" Check out the full "Science Off the Sphere" series, presented in cooperation with the American Physical Society.

More about the space station:

• Video: Russian rocket blasts off for space station
• New life science experiments sought for space station
• Space zucchini's life blogged by astronaut

Tip o' the Log to Phil Plait at the Bad Astronomy blog.

Alan Boyle is msnbc.com's science editor. Connect with the Cosmic Log community by "liking" the log's Facebook page, following @b0yle on Twitter and adding the Cosmic Log page to your Google+ presence. You can also check out "The Case for Pluto," my book about the controversial dwarf planet and the search for new worlds.

Robert Michael / AFP - Getty Images

A nearly full moon rises behind the cross of the Frauenkirche in the German city of Dresden in May 4.

Saturday night's "supermoon" is the biggest and brightest full moon of the year, due to the fact that the moon is near the closest point in its orbital path around Earth. But just how much bigger and brighter does it look? That's a tricky question.

Most reports say the moon looks 14 percent bigger than usual, which is close to the truth but isn't quite right. They also say it's 30 percent brighter than usual, which isn't right, either. James Garvin, chief scientist at NASA's Goddard Space Flight Center, ran the numbers to come up with an explanation that seems to make the most sense.

First of all, it's important to note that the moon itself is not getting significantly bigger or smaller. There's a scientific debate over whether the moon is slowly shrinking or spreading out. But in either case, the change isn't noticeable on human time scales.

The difference in the moon's apparent size is basically a function of how close it is to Earth in its elliptical orbit. That orbit isn't changing on human time scales, either. It just so happens that tonight, the moon is coming closest to Earth at the same time that it's going full. Because the moon and the sun are precisely opposite each other, relative to Earth, tonight's ocean tides may be a bit higher than typical — but again, the effect is nowhere near big enough to worry about.

So how noticeable is the visual effect? Here what Garvin told me in an email today:

• "The biggest predictable effect on the brightness of the full moon is how close the moon is to Earth.  With everything else the same, a full moon is about 30 percent brighter when the moon is closest to Earth in its orbit (called perigee) compared to a full moon when the moon is farthest from Earth in its orbit (called apogee).  Today’s full moon is at perigee."
• "Also, when the moon is high in the sky (as it is now), we are closer to the moon by approximately the radius of Earth compared to when the moon is on the horizon. (Note: Earth’s radius is about 6,371 kilometers)."
• "Since the distance from the center of Earth to the center of the moon is on average about 384,403 kilometers, the radius of the earth is about 6,371 kilometers, and brightness changes as the square of the distance, being closer to the moon by about the radius of the earth increases the brightness of the full moon by about 3 percent."  
• "Thus the present supermoon is, at maximum, only about 9 to 10 percent larger in an angular (appearance) sense than a typical full moon and is also brighter (by a few percent), making it appear 'super.'"

"Meanwhile, our intrepid Lunar Reconnaissance Orbiter continues its remarkable mapping of our nearest celestial neighbor, coming up (in June) on its three-year anniversary of being in lunar orbit with its amazing array of 7 instruments," Garvin added.  "As of now, the data returned from LRO (over 300 trillion bytes) is larger than all of the rest of the data acquired for planets in the solar system combined (except for Earth, of course)."

Which just goes to show that every day is a "super moon" day for the Lunar Reconnaissance Orbiter and its science team. Check out NASA's Web site for more wisdom from James Garvin.

Geoff Chester, an astronomer at the U.S. Naval Observatory, says the moon appears 14 percent larger in angular size when it's at the closest point in its orbit, compared with its appearance when it's farthest away from Earth. That's not 14 percent larger than average. That's 14 percent larger than the minimum apparent size.

"You'd be very hard-pressed to detect that with the unaided eye," Chester told The Associated Press. Seasoned skywatchers, however, say they can definitely tell the difference. Can you? Take a look at the moon tonight — before, during or after the moment of maximum fullness at 11:35 p.m. ET — and tell us what you see.

Update for 6:45 p.m. ET May 5: Bad Astronomy's Phil Plait observes that the moon's angular size is roughly equivalent to that of a dime as seen from 6 feet away. You can bet I'll have a dime taped onto a south-facing window tonight to make the observations. Also, tonight's supermoon will be a little less super than last year's supermoon, because the moon is about 240 miles farther away at peak fullness than it was in March 2011. For what it's worth, next year's supermoon will be imperceptibly smaller than this year's. I wonder if there'll be perceptibly less hype.

Update for 2:20 a.m. ET May 6: Yes, the weather was clear enough for supermoon-gazing in my Seattle-area neighborhood — and yes, I really did tape a dime onto a window to compare its angular size with the moon's. But it seemed to me that the sizes were about the same at a dime distance of 4 or 5 feet, rather than the 6-foot distance that Phil Plait suggested. Which just goes to show you: YMMV (your moon may vary). You can see what I saw by checking my Twitpic gallery.

More about the supermoon:

• How to see the supermoon — and meteors, too
• How to plan your supermoon snapshot
• Supermoon rises over Greek temple
• Five moon mysteries
• Five moon myths

If you snap a great photo of the moon, feel free to upload it into msnbc.com's FirstPerson in-box.

Alan Boyle is msnbc.com's science editor. Connect with the Cosmic Log community by "liking" the log's Facebook page, following @b0yle on Twitter and adding the Cosmic Log page to your Google+ presence. You can also check out "The Case for Pluto," my book about the controversial dwarf planet and the search for new worlds.

SpaceX

Sparks and clouds of exhaust and vapor issue forth from SpaceX's Falcon 9 rocket during a static fire test at Cape Canaveral Air Force Station on Monday.

SpaceX has suggested May 19 as the new date for its potentially history-making Falcon 9 rocket launch to the International Space Station, with May 22 as a backup date.

The schedule shift provides more time for NASA to review changes in the California-based company's flight software, and also avoids a potential conflict with the planned May 14 launch of three new space station crew members from Russia's Baikonur Cosmodrome in Kazakhstan.

If SpaceX's demonstration mission is completely successful, it would represent the first commercial flight to the space station. The flight plan calls for the company's robotically controlled Dragon cargo capsule to conduct a series of maneuvers near the station, starting two days after the Falcon 9 lifts off from Cape Canaveral Air Force Station's Launch Complex 40 in Florida. If all those maneuvers go as planned, astronauts on the orbiting outpost would latch onto the Dragon and pull it in for a berthing.

About a half-ton of supplies would be unloaded over the course of a couple of weeks, and then the Dragon would be detached and sent back down to a Pacific Ocean splashdown. That success scenario would open the way for SpaceX to start resupplying the space station in earnest, under the terms of a $1.6 billion contract with NASA.

If the Dragon couldn't hook up with the station this time around, another demonstration flight would be scheduled as a makeup test.

SpaceX has received hundreds of millions of dollars from NASA to develop the Falcon 9 and the Dragon as a partial replacement for the space shuttle fleet, which was retired last year. The Falcon 9 had a successful maiden orbital flight in June 2010, and the Dragon made a similarly successful debut in December 2010. The upcoming flight would provide the first opportunity for an actual rendezvous with the space station.

The launch has been repeatedly delayed, primarily due to flight software reviews. SpaceX conducted a successful launch-pad engine firing test on Monday in preparation for a planned May 7 liftoff, but the company and NASA decided to hold off in order to provide more time for the current review.

"SpaceX and NASA are nearing completion of the software assurance process," company spokeswoman Kirstin Brost Grantham said today in an email, "and SpaceX is submitting a request to the Cape Canaveral Air Force Station for a May 19 launch target with a backup on May 22. Thus far, no issues have been uncovered during this process, but with a mission of this complexity we want to be extremely diligent."

Bill Gerstenmaier, NASA's associate administrator for human exploration and operations, also indicated in a space agency statement that the May 19 date was doable.

"After additional reviews and discussions between the SpaceX and NASA teams, we are in a position to proceed toward this important launch," he said. "The teamwork provided by these teams is phenomenal. There are a few remaining open items, but we are ready to support SpaceX for its new launch date of May 19."

Because of the orbital mechanics involved with a space station rendezvous, the Falcon 9 must be launched at a precise time of day, with opportunities coming up only every three days.

The current plan would result in a launch at 4:55 a.m. ET May 19. That would provide an ample time interval after the Russians' launch of a Soyuz craft carrying a NASA astronaut and two Russian cosmonauts up to the station. That mission, which is due for liftoff on May 14 Eastern time and docking on May 17, will boost the station's crew to its full complement of six spacefliers.

More about SpaceX:

• SpaceX chief plans to become spaceflier
• Next steps in the new space race
• SpaceX has a lofty goal: Help save humanity
• CNBC: Elon Musk on why SpaceX has the Right Stuff
• Cosmic Log archive on the new space race

Alan Boyle is msnbc.com's science editor. Connect with the Cosmic Log community by "liking" the log's Facebook page, following @b0yle on Twitter and adding the Cosmic Log page to your Google+ presence. You can also check out "The Case for Pluto," my book about the controversial dwarf planet and the search for new worlds.

SpaceX

The SpaceX Dragon capsule is prominent in this photo of the Falcon 9 rocket in its lowered position at Cape Canaveral Air Force Station's launch complex in Florida.

The first private-sector spaceship destined to hook up with the International Space Station will have to wait a few days longer than planned for its Florida launch.

SpaceX's Falcon 9 rocket had been scheduled to lift off from Cape Canaveral Air Force Station's Launch Complex 40 on May 7, on a test flight that could climax with a space station berthing of its unmanned Dragon cargo capsule several days later. A launch-pad engine test went off successfully on Monday, but more time is needed to analyze changes in SpaceX's flight software and make sure all systems are go.

"At this time, a May 7 launch appears unlikely," SpaceX communications director Kirstin Brost Grantham said in an email. "SpaceX is continuing to work through the software assurance process with NASA.  We will issue a statement as soon as a new launch target is set."

Due to the orbital mechanics involved in a space station rendezvous, the Falcon 9 can be launched only at a precise time during the day, on specific dates. The next opportunity for launch comes on May 10, but it's not yet clear whether liftoff will be reset for that date. In a Twitter update, Space News' Brian Berger cited an internal NASA manifest that showed the launch slipping to no earlier than May 10. After that date, SpaceX would have to stand down to let the Russians launch a three-person crew in a Soyuz craft to the space station on May 14.

California-based SpaceX has received hundreds of millions of dollars from NASA to support the development of the Falcon 9 and the gumdrop-shaped Dragon capsule for resupplying the space station. The Falcon 9 has been sent into orbit only twice before — once in June 2010 with a test capsule, and again in December 2010 with a functional Dragon spacecraft that returned to Earth after two orbits.

The upcoming demonstration launch has been rescheduled repeatedly, from February to April to May, due to the need for intensive software reviews. The flight plan calls for Dragon to execute a series of maneuvers near the space station. If the spaceship's sensors and flight systems work as designed, Dragon will then fly a rendezvous and approach. If Dragon reaches the station safely, the station's astronauts will use a robotic arm to bring the commercial spaceship in for berthing, and then unload the non-essential cargo that's aboard.

A couple of weeks later, Dragon would be sent back down to a Pacific Ocean splashdown.

A success during this first berthing attempt would open the way for SpaceX to start regular robotic resupply missions to the space station under the terms of a $1.6 billion NASA contract. It also could help pave the way for Dragon to ferry Americans to and from the space station in three to five years, depending on further NASA funding. 

Since the last space shuttle left the station last July, Americans can travel into orbit only as passengers aboard Russian spacecraft, at a cost of about $60 million a seat.

More about SpaceX and the commercial space race:

• Private spaceship launch on the horizon
  
• SpaceX has a lofty goal: Help save humanity
• Next steps in the new space race

Last updated 3:25 p.m. ET. Tip o' the log to NBC News' Cape Canaveral correspondent, Jay Barbree.

 Alan Boyle is msnbc.com's science editor. Connect with the Cosmic Log community by "liking" the log's Facebook page, following @b0yle on Twitter or adding Cosmic Log's Google+ page to your circle. You can also check out "The Case for Pluto," my book about the controversial dwarf planet and the search for other worlds.

Blue Origin

This computational fluid dynamics simulation shows Blue Origin's orbital Space Vehicle with a body flap placed toward the spacecraft's aft end. More than 180 wind-tunnel tests were used to analyze design alternatives.

Executives at Blue Origin, the rocket venture founded by Amazon billionaire Jeff Bezos, have traditionally been reticent about discussing where they're going — but now that they're focusing in on development work for NASA, they're speaking out about their progress and their ambitions. And it turns out that those ambitions are ... well, pretty ambitious.

Like Armadillo Aerospace, Blue is developing a vertical-takeoff suborbital space vehicle for tourists and researchers. Like Sierra Nevada Corp., it's working on an aerodynamic spacecraft to carry NASA astronauts and other spacefliers into orbit. And like SpaceX, it's working on its own launch vehicles as well. The company may not provide many specifics about its timeline, but that doesn't mean the pace is lackadaisical.

"It's not a question of, 'Are we on some timeline,'" Brett Alexander, Blue Origin's director of strategy and business development, told me last week. "We've always said 'later in this decade' is when we're going to do it. Working with NASA will just accelerate us."

Alexander, who has worked on aerospace issues for more than two decades in government and industry circles, discussed Blue Origin's blue-sky ambitions as a follow-up to last week's news about a successful round of wind-tunnel tests for its orbital Space Vehicle, or SV. He said more than 180 runs were conducted at Lockheed Martin's wind-tunnel facility in Dallas to work out the right placement of aerodynamic body flaps on the aft end of the spacecraft.

The idea is that the flaps will enhance SV's biconic shape to give the capsule an extra bit of cross-range maneuverability "without the weight penalty and the complexity of wheels and wings," Alexander said. That could allow for a quicker return to orbit in the event of an emergency, since the SV could more easily be guided to a parachute-slowed descent over a designated land range.

May is a big month for Blue
Alexander said the resulting spacecraft design "will be officially blessed" at a system requirements review in May. Also during May, Blue Origin expects to begin testing of the thrust chamber assembly for its BE-3 rocket engine at NASA's Stennis Space Center in Mississippi, Alexander said.

The company, based in Kent, Wash., is receiving $22 million from NASA during the current phase of the space agency's program to help commercial ventures develop space taxis for the post-shuttle era. The SV isn't nearly as big as the space shuttle, of course, but it should be capable of transporting up to seven passengers to and from the International Space Station.

Alexander declined to say definitively whether Blue Origin would apply for further NASA funding during the next phase of the effort, known as Commercial Crew Integrated Capability or CCiCap. But with or without the money from NASA, Bezos and his team intend to create its their very own space transportation system.

"We started this design before NASA had the commercial crew program," Alexander said. "It was always our intention — and still is — to develop this."

He said that the plan calls for the "first few flights" to be launched on United Launch Alliance's Atlas 5 rocket, and that Blue Origin will eventually switch to its own launch vehicle with a reusable first stage.

Suborbital craft as 'pathfinder'
In parallel with its orbital development effort for NASA, Blue Origin is working on a separate crew capsule and propulsion vehicle that would blast off vertically for suborbital space trips. That part of the space program came into the spotlight last August, when Blue's unmanned test rocket went awry and crashed at the end of a supersonic test flight at Bezos' private spaceport in Texas. At the time, Bezos said that his team was "already working on our next development vehicle." Last week, Alexander said the development effort was "still under way."

In February, Alexander told Flightglobal that the suborbital crew capsule was undergoing testing, and that a pad-abort test would be conducted "in the summer sometime."

Although the funding arrangements for the privately backed suborbital program and the NASA-supported orbital program may be different, the two programs support each other technologically.

"Suborbital is definitely a pathfinder for our orbital system," Alexander said. The implication is that Blue Origin's rockets will be taking tourists and researchers to the edge of space significantly earlier than they'll be taking astronauts to orbit.

Bezos, whose net worth is currently estimated at more than $20 billion, doesn't strictly need NASA's money to pursue his long-held space ambitions. But Alexander said government backing will quicken Blue Origin's pace, and he argued against the sentiment in Congress that NASA should select just one company as the "leader" to go forward with spaceship development. Right now, NASA is supporting development efforts at four companies — the Boeing Co., Sierra Nevada Corp. and SpaceX as well as Blue Origin — and observers expect the field to shrink for the next round of funding. It's just a question of how much shrinkage there'll be.

"Competition is definitely better — better for the program, better for the country, better for the future of human spaceflight," Alexander told me. "If they down-select to one, it's no longer a commercial space program."

What do you think about Blue Origin's ambitions and the prospects for commercial spaceships? Feel free to weigh in with your comments below.

More about Blue Origin and Jeff Bezos:

• Blue Origin spruces up its rocket report
• How tycoons will fuel future spaceflight
• Bezos aims to bring up Apollo 11's sunken engines
• Cosmic Log archive on the commercial space race

Alan Boyle is msnbc.com's science editor. Connect with the Cosmic Log community by "liking" the log's Facebook page, following @b0yle on Twitter and adding the Cosmic Log page to your Google+ presence. You can also check out "The Case for Pluto," my book about the controversial dwarf planet and the search for new worlds.

SpaceX conducted a successful test firing of a Falcon 9 rocket's engines on its Cape Canaveral launch pad, one week before its precedent-setting launch to the International Space Station. But it took more than one try.

The initial countdown was halted just 47 seconds before the nine engines were scheduled to start up. SpaceX fixed what it called a "limit that was improperly set" on the flight computer and quickly set up another countdown. The second countdown proceeded smoothly, and the rocket's nine engines fizzed to life for two seconds as expected, at 4:15 p.m. ET today.

"Woohoo, rocket hold-down firing completed and all looks good!!" SpaceX's millionaire founder, Elon Musk, reported in a Twitter update. Meanwhile, company spokeswoman Kirstin Brost Grantham said "engineers will now review data as we continue preparations for the upcoming launch."

This was a full dress rehearsal for SpaceX's second official demonstration flight for NASA. The first demo flight, back in December 2010, sent a gumdrop-shaped Dragon space capsule into orbit for the first time. The second flight, scheduled to lift off as early as May 7, could see the Dragon go all the way to the space station.

The company has received more than $375 million so far from the space agency for the development of the Falcon 9 and the Dragon. SpaceX and another company, Orbital Sciences Corp., are getting the money to help NASA fill the gap in payload transportation capability left by last year's retirement of the space shuttle fleet.

In addition, SpaceX is receiving tens of millions of dollars from NASA under a separate program to make the Falcon/Dragon launch system suitable for carrying astronauts as well as cargo. Musk founded the California-based company in 2002 with the long-range aim of flying people to Mars.

The Falcon 9 didn't fly anywhere during today's test at Cape Canaveral Air Force Station's Launch Complex 40 in Florida, but if SpaceX and NASA stick to the current timeline, the rocket will send the robotically controlled Dragon capsule into orbit on May 7. A couple of days later, the spacecraft will catch up with the space station and go through a sequence of rendezvous maneuvers.

If the Dragon performs those maneuvers correctly, NASA would give the go-ahead for the Dragon to approach a station docking port. The station's robotic arm would grab onto it and bring it in for berthing. There'll be some cargo riding aboard the Dragon — water, clothing, scientific gear and the like — and the astronauts would take a couple of weeks to take on those payloads and load up the Dragon with Earth-bound cargo. Then the Dragon would be unberthed and sent back down to a Pacific splashdown, marking the successful end of the first flight of a private-sector spaceship to the International Space Station..

There are a lot of "ifs" on that list of contingencies. This launch has been delayed repeatedly due to software glitches, and if a snag like the one that occurred today happened to crop up on May 7, liftoff would have to be postponed for three days. To reach the space station, the Falcon has to lift off right on the dot. The orbital mechanics will not allow for same-day do-overs. But that's OK. Last month, SpaceX President Gwynne Shotwell said "we may have to have a couple of attempts, but we're certainly looking forward to getting that flight off."

If the Falcon 9 and the Dragon pass their tests, that would put SpaceX in a position to ship supplies to the space station in earnest, under the terms of a $1.6 billion NASA contract.

Will SpaceX get 'er done? Feel free to weigh in with your comments below.

More about SpaceX and the commercial space race:

• Private spaceship launch set for May 7 
• SpaceX has a lofty goal: Help save humanity
• Next steps in the new space race

Last updated 4:27 p.m. ET.

Alan Boyle is msnbc.com's science editor. Connect with the Cosmic Log community by "liking" the log's Facebook page, following @b0yle on Twitter or adding Cosmic Log's Google+ page to your circle. You can also check out "The Case for Pluto," my book about the controversial dwarf planet and the search for other worlds.

Skywatchers as far south as Colorado and Kansas witnessed a quick flare-up of the northern lights this week, which called to mind the brilliant, beautiful displays that northerners saw earlier this year. The skies have settled down — for now — but developments on the sun suggest we could be in for another wave of auroral glories.

The greenish glow over Lake Superior, recorded from Michigan's Upper Peninsula at 2 o'clock in the morning by Shawn Malone of LakeSuperiorPhoto.com, was impressive enough to make NBC's "Nightly News" on Tuesday night. In an email, Malone told me that the "intensity caught me off guard."

"Check out the passing freighter for scale," Malone said in his comments on the Vimeo version of the video. "What a view those sailors must have had!"

Mark Riutta had a similar view from Copper Harbor Cabins on the Upper Peninsula, as the time-lapse video below illustrates. Riutta told me over the phone that he and his girlfriend were getting the cabins ready for the summer season and were surprised by how bright Tuesday's display turned out to be. "We were just about to go to sleep, when we looked out and wondered, 'Why is it so light out there?' he said.

SpaceWeather.com provides a roundup of auroral images from a dozen U.S. states, mostly in the Midwest but also including the top state for the northern lights, Alaska. And speaking of Alaska, here's an unconventional view of the aurora that was recorded from a height of 90,000 feet during "Project Aether: Aurora," a scientific experiment that took place this month:

Project Aether, led by University of Houston physicist Ben Longmier, sent up almost two dozen weather balloons laden with high-definition cameras and scientific instruments to monitor auroral activity near Fairbanks. Most of the payloads have been recovered, but the student researchers are still on the lookout for a few that haven't yet been located. If you happen to be in the Fairbanks area and find one of them, you could win a prize.

More prizes could be in store for aurora-watchers: The National Oceanic and Atmospheric Administration's Space Weather Prediction Center reports that we're currently in the midst of a minor geomagnetic storm, which could spark another wave of northern lights. What's more, an active region of the sun known as AR1465 has developed the type of magnetic field that's associated with stronger X-class outbursts.

To keep tabs on the solar weather report, check in with SpaceWeather.com as well as the Space Weather Prediction Center's website and Facebook page. And to watch some classic auroral videos, check out the gallery offered by NASA's Gateway to Astronaut Photography of Earth.

More auroral glories:

• Awesome auroras on Uranus ... and Earth
• Farewell to the northern lights
• Northern lights make for must-see TV
• Southern exposure for auroral lights
• Slideshow: The best of the northern lights
• Cosmic Log's auroral archive

Alan Boyle is msnbc.com's science editor. Connect with the Cosmic Log community by "liking" the log's Facebook page, following @b0yle on Twitter or adding Cosmic Log's Google+ page to your circle. You can also check out "The Case for Pluto,"my book about the controversial dwarf planet and the search for other worlds.

Mark Wilson / Getty Images

Retired senator-astronaut John Glenn is surrounded by other space veterans in front of the space shuttle Discovery during its handover to the Smithsonian at the Udvar-Hazy Center in Chantilly, Va., on Thursday. Glenn says the shuttles were "prematurely grounded" but accepts the shuttle program's end.

For some veteran astronauts, today’s transformation of the shuttle Discovery into a museum exhibit is a cause for celebration. For others, it’s a reminder of their regrets. But for John Grunsfeld, the one-time “Hubble Hugger” who is now NASA’s science chief, the dominant feeling is a sense of relief.

Discovery's handover to the Smithsonian's National Air and Space Museum has re-ignited questions about the end of the 30-year space shuttle program. Why did they have to be retired? The short answer is that in the wake of the 2003 Columbia tragedy, policymakers decided that once the job of building the International Space Station was finished, it would just be too risky and expensive to keep the shuttles flying.

Instead, President George W. Bush decided to re-target the space program on destinations beyond Earth orbit. For Bush, the first focus was going to be the moon. President Barack Obama shifted that initial focus to near-Earth asteroids, but the endpoint is the same: eventually getting to Mars. And the shuttles could never do that. They weren't built to go beyond Earth orbit.

Nevertheless, some of America's best-known astronauts think the shuttles should have been kept around a while longer — particularly because NASA will be dependent on the Russians for rides to the space station for the next three to five years.

'Unfortunate decision'
"The unfortunate decision eight and a half years ago to terminate the shuttle program, in my opinion, prematurely grounded Discovery and delayed our research," retired senator-astronaut John Glenn said during today's handover ceremony at the museum's Steven F. Udvar-Hazy Center in Virginia.

Another retired astronaut who rode on Discovery, Tom Jones, voiced similar frustration during an interview conducted before today's ceremony. "I'm reliving the disappointment that the shuttles are retiring without a rapid successor," he told me.

Jones wishes that the White House and Congress had revved up NASA's plan for new spaceships capable of going to the space station and beyond: the Constellation Program, which initially aimed to put U.S. astronauts back on the moon by 2020. Instead, Constellation was so cash-starved and technically challenged that the Obama White House scrubbed the program and reworked elements of it into the current plan to visit an asteroid by 2025.

"We dropped the ball on this," Jones said. "If we just went from 0.5 percent of the federal budget to 0.6 percent, this would all be a non-issue."

The benefit of retaining an American system for resupplying the space station is what motivated Glenn's call to keep the shuttles flying. Glenn made his pitch to the White House in 2010 — but Obama didn't go for it, and the former Democratic senator told me today that he accepts the verdict.

"No need crying over what happened in the past," Glenn said. "Let's get on with the future."

The 'Hubble Hugger' and his pin
Grunsfeld thinks the White House made the right call, at least on the question of grounding the shuttles. He's best-known for his role as a spacewalker on Hubble servicing missions in 1999, 2002 and 2009. During that last mission, Grunsfeld was the one who bade the Hubble Space Telescope goodbye forever. Now he's NASA's associate administrator for science. The way Grunsfeld sees it, keeping the shuttles flying might have led to another disaster like the 1986 Challenger explosion — or the loss of Columbia and its seven STS-107 crew members in 2003.

"There's a possibility we could have flown them for a little bit longer, or extended them at some cost," Grunsfeld told me. "I'm actually extremely thankful that we are rolling Discovery into the Air and Space Museum, and not burying its parts. We flew out the space shuttle program gracefully. We didn't lose another one. It would have been tragic. The fact is that the space shuttle program was ended with dignity — it was an amazing accomplishment, and I'm just thankful for that."

Then he shared what he called a "small, personal story."

"Just this morning, on my flight suit for the first time since the loss of Columbia, I took my STS-107 pin off. I felt like this was an apt celebration, that we flew out the program safely after Columbia, and that affected me very deeply," Grunsfeld said. "Now that we are where we are, I'm looking forward to getting the next space vehicle going."

The end ... and the beginning
Retired astronaut Eileen Collins, who became NASA's first woman shuttle pilot during a 1995 mission on Discovery and went on to command shuttle missions in 1999 and 2005, has some firsthand knowledge about the risks associated with flying the shuttles.

The 2005 mission on Discovery marked NASA's "return to flight" after the Columbia tragedy. She and most other people at NASA had thought they had solved the foam-loss problem that led to the Columbia's doom — but mission managers were shocked to see that the fuel tank shed a substantial piece of foam insulation during Discovery's ascent. No significant harm was done, but it took another year for NASA engineers to rework the problem to their satisfaction.

This week, retired NASA shuttle manager Wayne Hale recounted the episode in a blog item headlined "How We Nearly Lost Discovery."

Today, Collins noted that each shuttles was originally designed to fly for 100 missions or 10 years, whichever came first. Discovery, the most traveled of the shuttles, flew 39 missions ... over the course of 28 years. She recalled that she agreed with the shuttle retirement plan that was announced in 2004, but was disappointed when the Constellation Program was canceled in 2010.

"At that time, I would say yes, we should keep the shuttles flying — with one major exception. Back in 2006, we at NASA made major decisions to start shutting down the pipeline for parts. In 2010, to reverse the decision and continue flying the shuttles was going to be very expensive and take a very long time. So it wasn't realistic to fly them again," she told me.

"The worst thing we can do to our people is to constantly change things ... so in the end, the right thing to do was to fly out shuttle. I am personally very sad to see it go. But the big problem is, we don't have anything to follow on right now. We're going to get there. It's just that right now, we don't have it."

It's not the end of the shuttle program that bothers Collins. Rather, it's the possibility that NASA won't be able to follow through on the beginning of the next program.

"I don't want to see any more canceled programs," she told a school group after today's ceremony. "If we have problems, we need to fix those problems and press on. We can't just cancel and walk away from them. I go to schools, and I talk to kids, and I say, 'If you have problems, stick with it, fix it, don't give up.' We don't want to continue to give up on programs that are going to be taking us out into space, whether it's with robots or with people. We need to keep working on those programs."

What do you think? Here's your chance to weigh in on the end of the shuttle program and the beginning of the next chapter in exploration. Just leave a comment below.

More about what's next for NASA:

• NASA gives all-clear for commercial launch to space station
• NASA's chief says end of shuttle era could usher in new age
• NASA unveils giant rocket design for future space odysseys
• NASA retools spaceship design for missions beyond Earth orbit
• Next steps in a commercial space race

Alan Boyle is msnbc.com's science editor. Connect with the Cosmic Log community by "liking" the log's Facebook page, following @b0yle on Twitter or adding Cosmic Log's Google+ page to your circle. You can also check out "The Case for Pluto," my book about the controversial dwarf planet and the search for other worlds.

Laurent Lamy

These composite images show Uranian auroras as bright spots on the planet's disk on Nov 16, 2011 (left), and on Nov. 29 (right). The images from the Hubble Space Telescope have been processed to bring out details in Uranus' faint ring system.

Thanks to the Hubble Space Telescope, astronomers have caught a rare display of auroras on Uranus, which ranks among the solar system's oddest planets.

Unlike the beautiful, rippling curtains of greenish light we've been seeing in earthly skies over the past few months, the Uranian auroras are short-lived bright spots sitting on top of the ice giant's bluish cloud tops. But they're caused by a similar mechanism, involving the interaction of electrically charged particles with atoms and ions in the planet's upper atmosphere.

NASA's Voyager 2 probe picked up the first evidence of Uranus' auroras in 1986. "Since then, we've had no opportunities to get new observations of this very unusual magnetosphere," Laurent Lamy, an astronomer at the Observatoire de Paris, said today in a news release. There have been a few hints of auroral observations, but Hubble's views from last November rank as the best views yet. Lamy and his colleagues provide the details in a paper published by Geophysical Research Letters.

The team took advantage of a lucky break and a favorable planetary alignment: Last year, Earth, Jupiter and Uranus were lined up so that energetic solar emissions could flow past each planet in turn. When the sun produced several outbursts in September, the astronomers timed the flow of the particle storm past Earth a couple of days later, and then detected the flow past Jupiter two weeks after that. On the basis of those readings, they calculated that the outburst would reach Uranus in mid-November, and scrambled to schedule observing time on the Hubble Space Telescope.

Uranus is an oddity because it basically rotates on its side as it orbits the sun. The orientation of its magnetosphere is tilted 60 degrees with respect to its rotational axis. As a result, during the current season, each of the planet's magnetic poles turns to face the sun in the course of a Uranian day. "This configuration is unique in the solar system," Lamy said.

Hubble was well-placed to catch the auroral flashes on the sunlit side, near Uranus' north magnetic pole. Each flash appeared to last only a couple of minutes, the astronomers said.

These new findings solidify Uranus' place on the list of planets flashing with auroral lights. Jupiter and Saturn are also on the list. Mars is thought to be capable of localized auroral effects, even though it doesn't have a global magnetic field. (In fact, some observers suspect we saw evidence of those effects last month.) Earlier this month, astronomers reported seeing auroral-type activity on Venus as well.

Lights on Earth
And then there's Earth. Last October, a solar outburst sparked northern lights that could be seen as far south as the state of Mississippi, and over the past month, higher-latitude residents have been treated to almost as many fireworks displays as Disneyland tourists typically get to see. Although the approach of summer is starting to cut down on the opportunities to see auroras in the Northern Hemisphere, some folks got great views as recently as last night. Here are a few of the highlights:

Shawn Malone of Marquette, Mich., snapped pictures of the aurora from the shores of Lake Superior. "The sky was ablaze in light," Malone told SpaceWeather.com. "Northern lights were so bright they lit up the beach!" For more from Malone, check out LakeSuperiorPhoto.com and his Vimeo video gallery.

Brian Larmay

Here's a different angle on the aurora and the International Space Station, captured by Brian Larmay of Beecher, Wis. The long streak in this time-lapse photograph is the space station, sailing across the sky. To see more of Larmay's pictures, check out his SmugMug gallery.

'Where in the Cosmos'
Today's picture of auroral displays on Uranus served as this week's "Where in the Cosmos" picture puzzle on the Cosmic Log Facebook page. It took only a couple of minutes for Shirley Beningo to blurt out which celestial body was shown in the picture, and what the bright spots were. To reward her for her quick cosmic vision, I'm sending her a pair of cardboard 3-D glasses, wrapped up in a 3-D picture of yours truly. Ashley Nicole and Gerry Marien came in as the runners-up, and are eligible for 3-D glasses as well. Be sure to click the "like" button on the Cosmic Log Facebook page so you're ready for next Friday's "Where in the Cosmos" contest.

Earlier stories of auroral glories:

• Farewell to the northern lights
• Northern lights make for must-see TV
• Southern exposure for auroral lights
• Sky lights go wild, north and south
• Solar storm lights up northern skies
• Slideshow: The best of the northern lights
• Cosmic Log's auroral archive

In addition to Lamy, the authors of "Earth-Based Detection of Uranus' Aurorae" include R. Prange, K.C. Hansen, J.T. Clarke, P. Zarka, B. Cecconi, J. Aboudarham, N. Andre, G. Branduardi-Raymont, R. Gladstone, M. Barthelemy, N. Achilleos, P. Guio, M.K. Dougherty, H. Melin, S.W.H. Cowley, T.S. Stallard, J.D. Nichols and G. Ballester.

Alan Boyle is msnbc.com's science editor. Connect with the Cosmic Log community by "liking" the log's Facebook page, following @b0yle on Twitter or adding Cosmic Log's Google+ page to your circle. You can also check out "The Case for Pluto,"my book about the controversial dwarf planet and the search for other worlds.