2014年9月30日 星期二
A Full Circle Rainbow over Australia
Sierra Nevada Develops Stratolaunch Launch For Dream Chaser
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U.S., India to Collaborate on Mars Exploration, Earth-Observing Mission
September 30, 2014
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More LightSail Day-in-the-Life Multimedia, and a Community Image Processing Challenge
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Fall Colors Arriving
Russia and China Visa Issues at the International Astronautical Congress
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2014年9月29日 星期一
Planetary Society President Testifies Before Congress
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Unusual Rocks near Pahrump Hills on Mars
Brief mission update: Hayabusa 2 has a launch date!
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Curiosity update, sols 748-763: Driving and Drilling at Pahrump Hills
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NASA TV Previews, Broadcasts U.S. Space Station Spacewalks
September 29, 2014
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Mars Orbiter Mission delivers on promise of global views of Mars
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This Is Your MOM’s Mars
Holy. Ares!
THAT is a full-disk image of Mars taken by India’s Mars Orbiter Mission, or MOM. It was just released this morning and shows nearly an entire hemisphere of the planet.
It’s gorgeous. There’s so much to see! North is to the upper left (roughly the 11:00 position), and the pole looks like it’s covered in a cloudy haze [Update (Sep. 29, 2014 at 17:40 UTC): Ah, according to my friend and fellow science writer Carolyn Collins Petersen, that's a dust storm brewing there.]. The huge, lighter-colored region just to the right and above center is called Arabia Terra, a 4,500-kilometer stretch of uplands that is one of the oldest terrains on Mars. It’s hard to tell from this wide-angle shot, but it’s heavily eroded and covered with craters.
Just below it is a long dark feature called Terra Meridiani (“Meridian Land”; though you could fancifully call it “Middle Earth”). The rover Opportunity is there, still roaming around and poking at the rocks there. This whole area shows evidence that is was once under water.
Nestled in the northern part of Terra Meridiani is the crater Schiaparelli, which is more than 460 km across! That’s huge, far larger than the crater left by the dinosaur-killer impact here on Earth. Straight up from it in Arabia Terra you can also see the crater Cassini (also more than 400 km wide), and to the right, just inside the dark region called Syrtis Major, is the crater Huygens, which is about the same size as Schiaparelli. The astronomers Cassini and Huygens studied Saturn, which is why the Cassini probe is named what it is, and the lander probe it sent to the moon Titan is named Huygens. Those astronomers really get around.
I could go on and on; you can see Hellas Basin as a smooth, butterscotch-colored area to the lower right just on the edge, and the ices of the south pole at the bottom. There are craters galore, and all sorts of wind-eroded areas that so many scientists will happily spend the rest of their lives studying.
But for me, right now, what makes me sigh in awe is the overall perspective of this picture. We’re seeing the entire face of the planet here, a perspective we don’t always get from our probes, sent to study Mars in detail. And the added touch of it not being fully lit—you can see the day-night line, called the terminator, cutting across the planet to the upper left—really drives home that what we’re seeing here really is an entire world, a huge expanse of territory just calling out for us to explore and understand.
There’s a lot of solar system out there to look at, and it fills me with joy to know we’re doing just that.
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Rocket Boosters Prepared For Orion Spacecraft's First Flight
2014年9月28日 星期日
Two Black Holes Dancing in 3C 75
Japanese Volcano Eruption Caught on Video… VERY Up Close and Personal
If you’ve ever wondered what my nightmares are like, they pretty much go like this.
On Sep. 27, a group of hikers were enjoying the fall weather on the Japanese volcano Mount Ontake. Suddenly, the volcano erupted, letting loose an incredible pyroclastic flow, a torrent of superheated ash that barrels down the slopes of the volcano like a thundering wall of death. The hikers tried to get away, but the flow was far faster… still, one of them managed to get video .
[Yes, it's vertical, so turn your head. And give the videographer a break, they were literally running for their life.]
My heart was pounding in my throat watching that; ever since I started reading about volcanoes years ago, pyroclastic flows fill me with visceral terror. They are implacable and unyielding; my friend and geologist Mika McKinnon calls them “rolling clouds of murder.” It is almost beyond imagination that the hikers survived. In fact, given how many people were on the mountain that day, it’s truly remarkable anyone survived. However, there have been no confirmed deaths as I write this (one had been reported but was subsequently retracted).
Here’s what it looked like from the air:
I’d write about the science behind all this, but Mika has already done an outstanding job on io9.
I love volcanoes; they are fascinating and something about them draws me in. I will happily travel to see more… but as I do, something like this will always be at the very least at the back of my mind. As long as it isn’t literally at my back.
<shudder>
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2014年9月27日 星期六
Dawn Journal: 7 Years of Interplanetary Travel
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A Night of Science and Silliness
I have good news if you like fun things! And if you live somewhere near the San Francisco Bay area.
On Oct. 25 I’ll be at the Castro Theater to do not one but two science comedy events: BAHFest and the Quiz-O-Tron 9000! Both are part of the Bay Area Science Festival, a week-long celebration of science. Or, in the case of these two events, the mocking of it. To wit:
1) BAHFest is the Festival of Bad Ad Hoc Hypotheses, which is the brainchild of that ginger fiend Zach Weinersmith, creator of the Saturday Morning Breakfast Cereal comic. The gist is that people come up with terrible science-based just-so stories to explain something, then present it to the audience and judges. To give you an idea of how this goes, read the SMBC comic that inspired it.
I will be a judge at this, and I will be harsh but fair (note: I will be neither). The keynote speaker is Matt Inman, who draws The Oatmeal, so c’mon. This will be amazing.
For tickets and such, go to the BASF BAHFest page. I know Zach and I will have books and stuff to sell and sign after the event, as will Matt and probably others.
b) Quiz-O-Tron 9000 is a snarky quiz show hosted by my friend and noted MRA enemy Rebecca Watson. She asks panelists about current science news topics, and the person with the most points at the end of the show (generally arbitrarily assigned by a judge with a tenuous grip on events) wins. I’ve done this a few times at DragonCon, and it’s a lot of fun (see these photos for evidence of such funnery). It’s also decidedly adult, so fairly warned be thee, says I.
I’ll note I am the Reigning Champion of the Universe for this game, and I have the belt to prove it. I’ll be bringing the belt with me, only so I can mock the other panelists when I take it home with me again.
I’m really excited by this. This will be a fantastically fun night, so don’t miss it.
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2014年9月26日 星期五
MAVEN at Mars
Using Lasers to Lock Down Exoplanet Hunting
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In Pictures: A Busy Week at the International Space Station
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Sierra Nevada Protests Commercial Crew Award
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Philae's landing day announced as Rosetta swings to comet's dark side
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Field Report from Mars: Sol 3790
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NASA Issues RFP for Next Round of Commercial ISS Resupply Missions
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NASA Expands Commercial Space Program, Requests Proposals for Second Round of Cargo Resupply Contracts for International Space Station
September 26, 2014
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2014年9月25日 星期四
NGC 206 and the Star Clouds of Andromeda
Someone at NOAA Really Hates Star Trek
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Another Soyuz is Heading Toward the Space Station
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New Crew Launches to Space Station to Continue Scientific Research
September 25, 2014
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NASA Awards Agency-wide Helium Contract
September 25, 2014
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NASA Awards Glenn Multiple Award Construction Contract
September 25, 2014
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You Can Now Buy NASA Wind Tunnel Parts on eBay
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ISEE-3 Is In Safe Mode
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We Are Indeed Made of Starstuff
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Dream Chaser Program to go Forward
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Looking for Comets in a Sea of Stars
India's Mars Orbiter: Does "Faster, Better, Cheaper" Work?
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2014年9月24日 星期三
The Lagoon Nebula in Stars Dust and Gas
How Much Will SLS Actually Cost?
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LightSail Sails through Day-in-the-Life Test
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MAVEN returns first images of Mars' atmosphere
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Reflecting on the success of Mars Orbiter Mission
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NASA Telescopes Find Clear Skies and Water Vapor on Exoplanet
September 24, 2014
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All That is Known About Bennu
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King Fire in California, False-Color Infrared
NASA Administrator Statement About India's Mars Orbiter Mission
September 24, 2014
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NASA Releases Emerging Space Report
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Holy Kilauea!
I travel quite a bit, and I’m privileged to visit some places of extraordinary beauty. Last week, I returned home from an exceptional trip to the Big Island of Hawaii. The proximal reason for the visit was to attend HawaiiCon, where much fun was had by all.
But as regular readers know, I am a sucker for volcanoes. Despite having been to quite a few, the ones I’ve seen personally are all quiet, either dormant or extinct. That all changed after the con ended, though. My wife and I drove across the island to visit the active volcano Mount Kilauea, and it was nothing short of life-changing.
After spending some time at the ranger station learning about the volcano, we went to the Jaggar Museum on the summit, which had excellent displays about Kilauea. The museum is on the very lip of the gigantic caldera, which is several kilometers across.
While I was there I shot a short video (I apologize for the wind noise; it was pretty gusty up there):
I may have forgotten to mention that I was traveling with my friend Aaron Douglas, aka Chief Tyrol from Battlestar Galactica . He was a guest at HawaiiCon too, and like us wisely decided to stay a few days extra to tour the island with his wife.
Kilauea is active, spewing out a towering plume of sulfur dioxide from a vent in the Halema’uma’u (ha-LAY-mah-oo-mah-oo) crater (which, mind you, is a kilometer across); the plume thankfully was blowing to the southwest when we were there. Here’s what it looked like:
Note how the plume looks blue at the base, and turns brown/red higher up. The blue is from the SO2 molecules in the plume scattering light; blue light hits those molecules and bounces off in random directions. But higher up the plume is seen silhouetted against the sky. The blue light is scattered away, but red light from behind gets through, changing the color of the plume.
In the foreground, on the caldera floor, there were dozens of smaller vents, each blowing out plumes:
I say smaller, but they’re still big compared to puny humans. I was wondering if some of those might have been water vapor plumes, but then through my telephoto lens I saw this one:
The yellow color makes it pretty clear that’s sulfur depositing on the ground. Incredible.
Not far from the crater, just down the trail, is the Kilauea Iki crater, which formed in a huge towering fountain of lava in 1959. Video of that eruption is jaw-dropping. The cinder cone formed all those decades ago still looks as fresh as the day it was violently born:
To give you a sense of scale, the arrow points to a person walking toward the cone along the trail.
We went back to the museum after that and decided to stick around until it got dark. That, it turns out, was one of the best decisions I’ve ever made in my life.
There is a pool of lava at the bottom of the Halema’uma’u, well below view from the crater rim. It also glows too faintly to see during the day, but once the Sun is down, magic happens:
That’s the plume illuminated by the molten rock below. We sat, watching as the sky darkened and the plume grew in brightness, until it glowed a brilliant red in one of the most astonishing sights I have ever witnessed. Short time exposures show it best:
You can see the steep walls of the crater there, and the plume billowing out. As extraordinary as that was, it was the wide view that had me gasping out loud:
This 30-second exposure shows the crater and plume, but also the stars of Scorpius high above. Hawaii is at a latitude of about 20° north of the Equator, which is much farther south than I’m used to. Scorpius was high in the sky, Sagittarius right behind it, and the Milky Way spilled across the sky easily seen to the eye. I couldn’t capture it to my satisfaction, but happily, and coincidentally, the wonderfully gifted astrophotographer Rogelio Bernal Andreo just posted a photo he took of the sky over Kilauea in June, and graciously gave me permission to use it here:
Holy Haleakala! You absolutely must click that to see it in all its beauty. I’ll note Andreo has a book coming out with his photos of Hawaii. It’s already on my holiday wish list.
Seeing this volcano myself was one of the most moving events I have experienced. The sheer power of it is almost overwhelming, the devastation it can cause always foremost on my mind. And yet, amidst all that, there was life, and not just life, but incredibly beautiful life:
We saw these orchids everywhere, along with many other scrappy plants and animals. Volcanoes literally create land, and the rich mix of ingredients in their output is like a smorgasbord to the life there. Kilauea is several hundred thousand years old, and yet is one of the youngest of the volcanoes in Hawaii. The sense of age looming all around you while there provides a perspective I couldn’t hope to appreciate without standing at that spot, sensing it for myself, taking it all in.
So my thanks to the people at HawaiiCon, to the Big Island Visitors Bureau (especially Erin Kinoshita who was tremendously helpful), to Aaron … and also to nature, for providing me a glimpse into its magnificence.
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2014年9月23日 星期二
Aurora and Volcanic Light Pillar
This Is What Happens to Moon Bashers
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India's Mars Orbiter Spacecraft Enters Mars Orbit
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New Space Vs Old Habits
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A Tour of 67P...
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How I will be watching Mars Orbiter Mission's arrival
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A Glimpse Into NASA's New History Archives
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45th Binghamton Geomorphology Symposium Report
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NASA Manager Honored for Launching New Era of Private-Sector Spacecraft
September 23, 2014
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NASA Astronaut to Speak to Clinton Global Initiative Meeting Attendees from International Space Station
September 23, 2014
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2014年9月22日 星期一
Last Chance to Fly Your Name to Asteroid Bennu
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SpaceX Texas Ground Breaking Ceremony
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NASA Lists ISEE-3 Reboot as 2nd Largest Space Crowdfunded Effort
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NASA Administrator to Participate in High-Flying STEM Education Event
September 22, 2014
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2014 Arctic Sea Ice Minimum Sixth Lowest on Record
September 22, 2014
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The Odd Trio
SHARAD: Delving Deep at Mars
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Mars Orbiter Mission test firing successful; all ready for orbit insertion
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Mars Fleet +1
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2014年9月21日 星期日
Saturn at Equinox
Celebration: MAVEN Arrives at Mars
NASA’s Newest Mars Mission Spacecraft Enters Orbit around Red Planet
September 21, 2014
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MAVEN orbit insertion timeline
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SpaceX Dragon Rockets to the Space Station
SpaceX Launches Dragon to the ISS
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An Astronaut’s Guided Video Tour of Earth
I love astronaut photography of Earth, especially the dizzying and psychedelic time-lapse videos. I’ve wondered, though, why we don’t see more straight-up plain old video of the Earth as the International Space Station passes over?
Well, here you go: I love this short tour of the Earth, narrated by astronauts Mike Hopkins and Rick Mastracchio as they pass over some pretty familiar landmarks:
It’s fun to see places I’ve visited (or even lived, like Houston and San Francisco) slowly slide past the view. Of course, “slowly” is just perspective; the ISS orbits at eight kilometers per second—18,000 miles per hour! But it’s also several hundred kilometers up, and distance does tend to change frame of reference.
And it’s not hard to see that video like this puts to rest the silly urban legend that the Great Wall of China is the only human-made structure visible from space. Cities, farm lands, dams, and even bridges are easily spotted, even without the zoom lens. Even better: The Great Wall is actually pretty hard to spot from orbit! It’s not actually that wide, and doesn’t have a lot of contrast with the surrounding land, making it difficult to see.
Don’t believe everything you hear. Or see. Or anything, actually: Always look for evidence. What you find might disappoint you at first, but it’s always good to learn something new. And you might stumble on something really cool … like photos taken by space-traveling humans as they fall endlessly around a blue-green world.
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NASA Cargo Launches to Space Station aboard SpaceX Resupply Mission
September 21, 2014
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2014年9月20日 星期六
Shoreline of the Universe
NASA Launches New Citizen Science Website; Opens Challenge to Participate in Future Mars Missions
September 20, 2014
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The Shaggy Sun
The Sun has been pretty active lately, popping off a series of fairly powerful X-class flares; they've been generating aurorae and other magnetic phenomena on Earth.
But even before it started spouting off it was still busily doing Sunny things. Recently it was almost as if it was posing for photographers, and when you get someone like Alan Friedman—who knows his way around a solar photo—you get beauty and majesty.
That shot was taken on Sept. 1, 2014, and shows a portion of the Sun. I know, it looks weird, doesn’t it? He uses a filter that only allows through a very narrow slice of color emitted by warm hydrogen, and this tends to emphasize the gas under the influence of magnetic fields. He also does something tricky: He uses the negative of the image to enhance details.
So the bright spots are actually dark sunspots! The few you see in this image are roughly the size of the Earth, if you want your sense of self-importance vaporized today.
The other features are prominences, filaments, and, apparently, a shag carpet covering the Sun that it still has from the 1970s. All of these features are magnetic in nature. The Sun’s extremely complicated magnetic behavior starts deep within, with magnetic field lines connected to moving cells of ionized gas (called plasma). As these huge packets of gas rise to the surface through convection, their magnetic fields lines move plasma around on the surface. The lines can also get tangled up and then snap, releasing their energy as solar flares.
The gas packets cool when they reach the surface, but sometimes the magnetic field acts like a net, trapping that gas. It can’t sink, and it cools more than the surrounding gas, so it looks dark in comparison. Sunspots!
All this information is hidden unless you look at the Sun in just the right way, examine what it’s doing by slicing up and dissecting its light as it reaches Earth (or space-based observatories). When you do, you get knowledge, as well as profoundly beautiful (and, sometimes, profoundly odd) portraits of our nearest star.
So go take a look at more of Alan's photos. Trust me: You'll be glad you did.
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2014年9月19日 星期五
Potentially Habitable Moons
More jets from Rosetta's comet!
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NASA TV, Web Coverage Set for Sept. 21 Mars Spacecraft Orbit Insertion
September 19, 2014
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The Curious Incident of the Supernova in the Nighttime
Detective Gregory: “Is there any other point to which you would wish to draw my attention?”
Holmes: “To the curious incident of the dog in the night-time.”
Gregory: “The dog did nothing in the night-time.”
Holmes: “That was the curious incident.”
— “Silver Blaze,” by Arthur Conan Doyle
Sometimes, you learn more about something when it isn’t there.
In January 2014, the light from a distant supernova reached Earth. It caused some excitement because the star that exploded was in the nearby galaxy M82 and that meant it was within reach of even small telescopes—in fact, it was discovered using an amateur-sized 35 cm telescope being used by an undergraduate astronomy class. Using my own telescope, I saw this supernova at the eyepiece as well.
Even better, the supernova, called SN 2014J (the 10th one discovered in 2014), was a special one: Type Ia, the kind used to measure the expansion of the Universe. We can see them very far away, and they’re used as benchmarks to calibrate distances to extremely remote galaxies. Seeing one nearby allows us to better understand them, and therefore better understand the size and expansion of the Universe itself.
Because the supernova was in a nearby, well-studied galaxy, we have lots of observations of the area before and after the explosion. The mighty orbiting Chandra X-Ray Observatory was pointed at M82 after the supernova went off, and found something surprising: nothing.
The image shows the galaxy in X-rays—extremely high-energy light emitted by black holes, very hot gas, stars being born, and, sometimes, supernovae. The little box marks the location of the star, and inset are enlargements; on the left is centered on the region before the star blew up, and on the right is the same area after the supernova. As you can see, there’s nothing there.
That’s interesting! We know that this type of explosion is caused by a white dwarf, the extremely dense core of a star that was once much like the Sun but has since shed its outer layers (much like the Sun will do in about 6 billion years after it becomes a red giant). There are several ideas about what happens next. It’s possible the white dwarf siphons material off a nearby companion star; that stuff piles up, gets very hot, and then fuses like a gigantic nuclear bomb, shredding the star and creating a very large bang indeed.
Another model is that two white dwarfs circle each other and, over billions of years, eventually merge. They collapse into an even-denser neutron star, and again you get a very large explosion. There’s even a third idea that there are three stars involved, two white dwarfs and a “normal” star, and the interaction between them causes a direct, head-on collision between the two dwarfs, causing the explosion. All three ideas have their merits, and astronomers are still arguing over them.
What makes SN 2014J critical to this is that if it were a white dwarf sucking material off a binary companion star, we’d expect some of that gas to get flung out into space; white dwarfs, apparently, are sloppy eaters. But when the dwarf explodes, the blast wave would slam into that material, and the interaction should generate copious X-rays. Yet none is seen.
And that’s why this is so interesting. It would appear the normal star binary companion model doesn’t work for 2014J … at least, without some other event going on, like perhaps a whole bunch of smaller pre-supernova eruptions that cleared the region of gas. That’s possible, but I prefer not to have to resort to special circumstances when other explanations are also likely.
The next step is to continue taking more observations. The debris from the explosion is still screaming outward, and will continue to do so for years. As it expands, any gas out there will get plowed, and Chandra should see it. Until then, though, we must be much like Sherlock Holmes, looking at the evidence that isn’t there as well as that which is.
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Congress Delays Space Legislation Until Next Year
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Starry Sky from the Space Station
Two Views: Dragon Vs CST-100
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2014年9月18日 星期四
Cocoon Nebula Wide Field
Space Golf Update: NASA Inspector General Has Noticed That CASIS is a Flop
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NASA's 2015 Sample Return Robot Challenge Open for Registration
September 18, 2014
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OIG Report on Extending ISS Operations Until 2024
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NASA Television Coverage Set for Next Space Station Crew Launch
September 18, 2014
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Red and Green Ghosts Haunt the Stormy Night
Randy Halverson is a photographer and has quite a gift for time-lapse video (I’ve featured his work many times on the BA blog).
He recently sent me a video he took in central South Dakota that is quite astonishing. While photographing a storm at night, he caught two very rare events at the same time: sprites, and gravity waves rippling through airglow!
First, here’s the video, because it’s amazing.
Did you see the sprite? It happens just before the six-second mark in the video. Look to the right, just above the storm cloud. The red flash is obvious once you spot it.
Sprites are a phenomenon associated with lightning storms; they’re electrical discharges from the top of the storm cloud, not the bottom. They’re not really understood, but they occur simultaneously with lightning between clouds or from cloud to ground, and glow eerily red. They were only first discovered in 1989 (officially, that is; pilots have been reporting them for decades, but no one outside that cadre really took them seriously) so not a huge amount is known about how they operate.
On a larger scale, you can also see green ripples moving across the sky. The green is airglow, molecules in the upper atmosphere that are energized by the Sun during the day, and give off that energy as light at night. This occurs via chemoluminescence; a process where the excited nitrogen and oxygen atoms molecules bump each into other and form bonds, giving off that light.
The rippling is due to gravity waves. This is simply an up-and-down oscillation of something under the influence of gravity. For example, waves on the surface of the water in your bathtub are gravity waves; the water gets pushed up a little bit (maybe when you plop your rubber ducky into the water), and then gravity pulls that crest of water back down. But the water itself pushes back, and you get oscillatory motion.
This can happen in air, too (air is a fluid, after all). Currents of air in the upper atmosphere bob up and down pretty often, similar to the water in your tub. This motion can disturb the process that creates airglow, so you get those rippling waves moving across the sky. I only recently learned about this phenomenon, when I saw a time-lapse video taken in Chile, a world away from South Dakota.
Several years ago, Randy sent me an email asking about a weird rippling glow he saw in some footage he had taken. I wasn’t sure at that time what it was (though I was sure it wasn’t an aurora), and we agreed it could be airglow. It’s funny that he would send me this new video right after I finally learned what that rippling was! If Randy had asked me two weeks ago I wouldn’t have known. He found out on his own, and now we both understand. And I hope now you do too.
The sky above us is just incredible. There’s still so much to discover, so much to figure out, so much to explore. And it’s all right there, just over our heads.
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2014年9月17日 星期三
Aurora over Maine
Hubble Helps Find Smallest Known Galaxy Containing a Supermassive Black Hole
September 17, 2014
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NASA Seeks America's Best and Brightest for Space Technology Research Fellowships
September 17, 2014
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NASA Kicks Off a Private Space Race Between Boeing and SpaceX
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NASA Administrator Visits North Texas Air Traffic Management Facilities, Discusses NextGen Development
September 17, 2014
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Blue Origin and ULA to Jointly Fund New B4 Engine
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NASA Mars Spacecraft Ready for Sept. 21 Orbit Insertion
September 17, 2014
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Comet Siding Spring Mars encounter: One Mars Express plan becomes two
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A Bridge Across the Sky
A couple of months ago I spent a few days in western Colorado, far away from city lights. I was with a group of science enthusiasts for Science Getaways, taking a weeklong vacation chock full o’ science.
That part of the country is blessed with dark skies and fantastic weather, and I took my telescope out every night to view the heavens. But just standing there and looking up was surpassingly moving. The Milky Way loomed large over the land, stretching across the sky, so bright it was a palpable thing.
A half a world away, that feeling was captured perfectly by astrophotographer Amirreza Kamkar, who took this incredible picture in Abyaneh, Iran:
Wow. This shot is a mosaic of seven 20-second exposures, in what must be a phenomenally dark region. I like how Kamkar pointed the camera in such a way that the picture goes horizon to horizon, and the Milky Way is, in Kamkar’s own words, a bridge across the sky.
Our disk galaxy dominates the scene, apparently edge-on since our solar system is embedded in it. Dark dust lanes block light from stars behind them, and a few pinkish nebulae dot the skyscape near the bottom. Stars are being born in those clouds, thousands of them at a time.
Not only that, but a satellite can be seen leaving a dead-straight track on the right, and above it, a bright meteor flashed. At the other end (at the “top,” though it’s really just the other horizon) you can see the fuzzy Andromeda galaxy, and below it the bright reddish star Mirach behind a cloud, which mimics the much more distant and far, far larger galaxy. Mirach is a red giant, a star that may have once been much like the Sun, but is now dying, swelling to huge proportions and becoming a luminous beacon; a last gasp before shrinking and fading away a million years hence. It’s a reminder that even the Sun won’t last forever, but the galaxy itself—with the help of its star-forming nebulae—will live on for eons to come.
This is a clever shot and substantially beautiful. I highly recommend visiting Kamkar’s collection of astrophotographs at The World at Night website; I particularly liked this one. Such photographic talent, and a sense of humor! Wonderful.
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Powerful, Pulsating Core of Star
NASA Announces a New Challenge at World Maker Faire
September 17, 2014
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Unanswered Commercial Crew Questions
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2014年9月16日 星期二
Milky Way above Atacama Salt Lagoon
CCtCap: Is Boeing More Expensive or is SpaceX Just Cheaper?
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NASA Chooses American Companies to Transport U.S. Astronauts to International Space Station Selection
September 16, 2014
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FAA Relases HSF Recommended Practices Safety Document
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NASA Airborne Campaigns Focus on Climate Impacts in the Arctic
September 16, 2014
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Mars Orbiter Mission prepares for Mars arrival
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Mars Orbiter Mission arrival timeline
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NASA’s Chandra X-ray Observatory Finds Planet That Makes Star Act Deceptively Old
September 16, 2014
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Florida to Louisiana Viewed From the International Space Station
NASA to Make Major Announcement Today About Astronaut Transport to the International Space Station
September 16, 2014
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ISS Daily Summary Report – 09/15/14
September 16, 2014 at 12:38AM
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A Galaxy of Tatooines
Using an old-style observing technique, astronomers have come to a very interesting conclusion: About half of all exoplanets in the galaxy are in binary star systems.
That’s astonishingly cool. Mind you, it’s not unexpected, but now we have some evidence for it.
Here’s the deal. We know that roughly half the stars in the galaxy are in binary systems, with two stars physically orbiting each other. The circumstances that give rise to star formation make it pretty easy for two stars to form near each other (the Sun, of course, being an exception).
We also know that planets are pretty common around stars as well; we know of nearly 2,000 such exoplanets at this point, and thousands more are waiting to be confirmed. It’s natural to put these two ideas together, and ask: How many exoplanets orbit a star in a binary system?
You’d expect the ratio to be the same, but Nature is tricksy sometimes, so it’s best to check. However, that can be tough. Even though a binary companion might orbit a star billions of kilometers out, from light years away the two stars blend into one blob. Even Hubble might not separate the two.
To see what they could see, the astronomers relied on an old method called speckle interferometry. Basically, the Earth atmosphere roils over our heads, with little packets of air flying this way and that. When light from a star passes through them, it gets bent this way and that as well due to refraction. This happens many times per second, so when you take a long exposure the light blurs into a disk. Astronomers call this (confusingly) “seeing.” It’s also why stars appear to twinkle.
But there’s a way around this. Over time the light rays get smeared out, but if you take lots of extremely fast exposures, you freeze that motion out. It’s like taking super slo-mo video. Instead of a big disk, you get a bunch of near-perfect images of the star that jump around in location from image to image, but each frame is a nice, extremely high res shot of the star.
There are limitations to this technique; the star can’t be too faint, or else you won’t get enough light in each frame. There are also limits to the resolution due to telescope size, too. And you need a very sophisticated technique to combine the resulting frames to tease out all the information in them. But speckle interferometry has been around a long time, and its methods are solid (here’s a detailed and technical description).
The astronomers observed a bunch of stars known to have planets (found by the Kepler mission), and then used speckling to see how many had detectable stars very close by. They then used some pretty nifty simulations to find out how many binary companions they might miss—some might be too close to the star to separate even using these techniques. By comparing the two results, they were able to conclude that 40–50 percent of all exoplanets orbit a star in a binary system.
That’s pretty amazing. There are billions of planets orbiting stars in binary system in our galaxy!
What I find most interesting about all this, oddly, is the mundanity of it. Back in the day, we didn’t even know if other planets existed. Was there something special about the Sun that allowed it to host a solar system? Size, chemical content, position in the galaxy? But now we see that a wide variety of stars have planets. Even having another star orbiting the host star doesn’t seem to be a problem!
... well, as long as the other star is far enough out. Closer in, and its gravity could disrupt the planet orbit. But if the stars are close enough together, a planet could orbit both stars. Quite a few such circumbinary exoplanets (I love sciencey words) have been found. I’ve written about a few of them, like Kepler 16b and PH-1b.
Forty years ago this picture was science fiction. Now … well, now not so much.
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2014年9月15日 星期一
Boeing/Blue Origin Poised to Take Commercial Crew Contract?
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62 Kilometers above Comet Churyumov Gerasimenko
NASA Commercial Crew Announcement Being Planned for Tuesday
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A landing site for Philae, but it's not going to be easy
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CASIS Would Rather Go Golfing Than Do Actual ISS Research
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OIG: NASA NEO Program is Inefficient and Lacks Oversight
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