2015年2月28日 星期六
Moon Venus Mars Skyline
Leonard Nimoy: A Science Fan’s Appreciation
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Astronaut Salutes Nimoy From Orbit
Ticket to Space
My friend Dan Durda is many things: an astronomer, a planetary scientist, an artist, a pilot.
He’s also an astronaut. Or he will be, very soon.
He works at Southwest Research Institute here in Boulder, Colorado, which is a company that does a lot of work in space; the New Horizons Pluto probe instruments were developed there, for example, and the principal investigator, Alan Stern, is there. Dan’s very interested in the behavior and structure of asteroids, which is difficult to study here on Earth.
So he and his fellow scientists at SwRI got an idea: Go into space.
We’re at the doorstep of cheaper, more reliable access to space. Ticket prices are within reach of wealthy individuals and, perhaps more importantly, companies that do science. A lot of Dan’s experiments can be done easily in the few minutes of weightlessness these suborbital flights provide.
But why not get all this from Dan himself? He recently gave a TEDxBoulder talk about this, and it’s really good.
What he said is true: We’re just starting off doing this work, and we don’t know where it will lead. There have been setbacks, for sure; the loss of the Virgin Galactic vehicle and its pilot last year, and the explosion of the Antares rocket upon liftoff.
As I have written many times before, while tragic, these sorts of losses are inevitable. They are the price we pay for pushing boundaries, and you’ll find most astronauts understand these risks. To use an analogy Dan made in the video, where would be now if airplane crashes grounded the airline industry in the early 20th century?
We’ll continue on, pushing our way into space. Again, as Dan points out, we cannot know where this will lead … except up. And that’s a direction I think we should go.
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2015年2月27日 星期五
Long Lovejoy and Little Dumbbell
Highlights from our reddit Space Policy AMA
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Pluto Science, on the Surface
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NASA Sets Coverage for Launch of Magnetospheric Multiscale Mission
February 27, 2015
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Leonard Nimoy
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Who Has More Relevant Capsule Expertise?
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The More Space Stations, The Better
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The Usual Suspects Want Their Government Handout
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2015年2月26日 星期四
Love and War by Moonlight
New NASA Earth Science Missions Expand View of Our Home Planet
February 26, 2015
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Russia Moves to Support ISS through 2024, Create New Space Station
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Feb. 26, 1966 Launch of Apollo-Saturn 201
Kepler-432b: A Doomed Planet Orbiting a Doomed Star
Two independent teams of astronomers have just announced the discovery of an unusual planet with a grim future: Kepler-432b.
The planet orbits a star nearly 3,000 light-years away and was discovered using the Kepler observatory, which looks for telltale dips in star light as a planet orbits a star; if the planet’s orbit is seen edge-on from Earth, then once per orbit it blocks a small fraction of the star when it passes directly between the star and Earth.
Measuring the timing of the dip (and knowing some of the properties of the star) yields a lot of information about the planet, including its size, and the size and shape of its orbit. They also took spectra of the star, breaking its light up into thousands of individual colors, which yields one more crucial piece of information: the mass of the planet. The planet and star orbit a common center of gravity, and as the star moves in its orbit its spectrum changes due to the Doppler shift. This effect is pretty dang small, but measurable using precision instruments.
The results are pretty cool: The planet Kepler-432b is roughly five times more massive than Jupiter, but only about 1.1 times as wide. This makes it pretty dense, about as dense as Earth! Gas giants have a weird property that as they get more massive their size doesn’t increase much—instead, the pressure inside them increases, and their density goes way up. Jupiter is right at about the lower limit where that happens, so planets can be much beefier than Jupiter but not much bigger.
But what makes this system special is the star itself. It’s a little more massive than the Sun, but it’s what we call a red giant: A star that is starting to die.
At some point in the past, the star Kepler-432 ran out of hydrogen fuel in its core. The core of the star is shrinking and heating up, dumping all that heat into its outer layers. What happens to a gas when you heat it up? It expands. And so Kepler-432 has swollen up to a size about four times wider than our Sun. As it got bigger its surface area increased, too, and so, weirdly, the amount of energy coming through its surface per square centimeter has actually dropped, lowering its temperature. Cooler stars are red, so Kepler-432 is a red giant.
It will continue to grow as it ages, swelling to a much larger size than it is now. Much larger. Will it engulf the planet?
It may not grow enough to swallow the planet directly. However, as it gets bigger, it interacts with the planet via tides, and (through a complicated series of steps) will actually drop the planet closer in to the star.
It looks like this one-two punch is enough to doom the planet. The star will grow larger, the planet’s orbit will shrink, and then … doom. The planet will fall into the star, where it will plunge deeper and deeper, until it evaporates completely.
But don’t despair too much. As the planet falls inside the star, it takes a while to disintegrate. It orbits much faster than the star spins, so it may churn up the insides of the star like a whisk in a mixing bowl of batter. The star’s rotation will increase. As the star continues to age, it will fling off its outer layers, exposing the hot core at its center. This very dense, very hot object, now called a white dwarf, will blast ultraviolet light into space, illuminating and exciting the gas it ejected, causing it to glow. Because the star was spinning, this gas can take on fantastic shapes, including double-lobed patterns reminiscent of butterfly wings.
Scientifically, this system is fascinating; we don’t have too many examples of giant planets orbiting red giant stars (which may be in part due to the fact that they tend to fall into their stars!), so every one we find is important. The planet orbits the star on a long ellipse, too, which is unusual and difficult to explain. There are many mysteries to plumb here.
And metaphorically, well, this transformation is almost too on-the-nose: Like a caterpillar, the planet and star will transform into something magnificent, literally a butterfly shape. And it will glow fiercely like that for centuries, its beauty visible easily from telescopes even thousands of light years away.
The Universe is all about change, birth, destruction … and given that, perhaps Kepler-432b’s eventual fate isn’t such a bad one.
Postscript: You can read the papers published by the two teams who studied this planet: Ciceri et al ., and Ortiz et al . Their results match pretty well, though, interestingly, Ciceri et al. find no evidence for a second planet orbiting the star, while Ortiz et al. do. Also, Ciceri et al. conclude the planet won’t be engulfed. I don’t think they included the work showing the planet’s orbital radius will shrink, though, which was considered by Ortiz et al., so I tend to agree with Ortiz’s team. The planet is doomed.
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2015年2月25日 星期三
The Rosette Nebula in Hydrogen and Oxygen
At last, Ceres is a geological world
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Pete Worden is Leaving NASA
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NASA Spacecraft Prepares for March 12 Launch to Study Earth’s Dynamic Magnetic Space Environment
February 25, 2015
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Dawn Journal: Ceres' Deepening Mysteries
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NASA Offers Space Tech Grants to Early Career University Faculty
February 25, 2015
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Tempest Vermilion
Gavin Heffernan is a photographer who travels to difficult-to-reach locations and shoots simply tremendous time-lapse videos of the landscape and night sky he sees there.
He just sent me a note that he’s created another video, and, well, holy wow. It’s another stunner: “Tempest Vermilion,” shot at the Vermilion Cliffs National Monument in Arizona.
You know the drill: Make it full screen, set it to high-def, crank up the volume, and let your eyes and brain soak it up.
Photographic stills from the shoot are on Flickr.
This is the second part of a trilogy of videos Heffernan has created for BBC 2; the first, called “Wavelight,” is online as well. He and his collaborator, Harun Mehmedinovic, are also making a video about the effects of light pollution. Called “Skyglow,” it’ll be on Kickstarter in early April. Stay tuned for that.
In the meantime, take a look at these other amazing videos by Heffernan:
Time-Lapse: Kings Canyon
Time-Lapse: YIKÁÍSDÁHÁ
Death Valley DreamLapse
Predators and Prey, Dragons and Dark Skies
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Chicago in Winter
OIG Has Doubts About NASA's Humans to Mars Plans
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A Supermassive Black Hole’s Fiery and Furious Wind
When you think of black holes, you probably think they are chaotic destroyers of all; wandering through space devouring everything in their path, and once something gets too close, it’s gone forever.
That’s a little unfair. Actually, a lot unfair. They only eat stuff that’s nearby, for one thing. And for another, they’re sloppy eaters. Not everything falls straight down their gullet; a lot of it can swirl around the black hole in what’s called an accretion disk. Material in that disk can be heated to terrifyingly high temperatures, millions of degrees, causing it to glow fiercely bright. It can blast out X-rays, and even create an intensely strong wind of material that flows away from the black hole.
We also know that every big galaxy we look at has a supermassive black hole in its very center. If that black hole has gas and matter falling into it, the accretion disk can be huge and ridiculously, soul-crushingly bright. The luminosity of such an object can easily outshine the hundreds of billions of stars in the host galaxy, and make the black hole visible clear across the Universe.
This sets up an interesting problem. When you have a monster in the middle like that, how does it affect the rest of the galaxy? A curious fact was discovered many years ago; the mass of the black hole in a galaxy seems to correlate with how the stars in the galaxy orbit. You might think “duh” to that, but hang on. Even though a black hole can have a mass of a billion times the Sun, that’s a teeny tiny fraction of the mass of a galaxy with a few hundred billion stars in it.
Somehow, the black hole is affecting the galaxy around it on a huge scale. How?
The obvious way is through this wind, this cosmic hurricane of particles blasting outward from it at high fractions of the speed of light. Studying that wind is maddeningly difficult, though. For example, when we look right at the center of the galaxy, all we can see is the extremely narrow slice of gas between us and the black hole. That gas absorbs the light coming from the accretion disk, blocking it. As it happens, different kinds of atoms block different colors of light. One type of iron, for example, that has a lot of its electrons ripped away from the intense energy blasting away nearby, is really good at absorbing a very specific wavelength of X-rays.
That can tell you something about the gas, like how hot it is, and how fast the gas is moving away from the black hole. But what it doesn’t tell you is the overall shape of the wind. Is it blowing out spherically, like an expanding balloon, or is it focused into narrow beams?
Lots of black holes have those beams screaming away from them. We know this because we can see them. But not every black hole has them. So how can you figure out the shape of the wind?
Some astronomers have just announced they found a way. The black hole they observed is a billion-solar-mass beast in the center of the galaxy PDS 456, which is about 2 billion light-years away. It’s fairly well studied, and is a good example of a typical “active galaxy,” one with an actively feeding black hole in its core.
They observed it using two different observatories: XMM-Newton and NuSTAR. Both can sort incoming X-rays into their individual energies (think of that like color in light we see). XMM-Newton could see the gas blocking the black hole directly, but can’t detect any gas anywhere else. NuSTAR, however, is able to see the kind of X-rays that would be coming from gas surrounding the black hole … and it did. Looking at the spectrum of the X-rays, it found the unmistakable signature of gas expanding outward in a sphere (if you want technical stuff, it saw a classic P-Cygni profile).
This is a big deal. The geometry of the expanding wind can tell us its total energy. Think of it this way: Imagine you have a 1-watt light bulb. It looks pretty dim, because it’s sending light out in all directions. Only a little bit of the light is heading into your eye. But if I have a flashlight, it focuses the energy emitted, so it can gather up all the light being wasted in other directions and beam it toward you. The bulb in a flashlight can be a lot dimmer, but still look brighter to you because of that.
And that’s the basis of these new observations. They saw that the wind from the black hole is expanding in all directions, which means the astronomers could determine the overall physical nature of the wind. It turns out the black hole is blasting a wind that totals 10 times the Sun’s mass every year—and mind you, that vast amount of stuff is screaming out at tens of thousands of kilometers per second. If I’ve done my math right (and I have; I checked), that means the mechanical energy in that wind is a staggering 10 trillion times the total energy the Sun emits every second.
Ten trillion.
And that wind is blowing outward in all directions, so it can easily affect the gas around it, even thousands of light-years away. This in turn would affect how stars form in a galaxy, and explain the relationship we see between the black hole and the stars in the galaxy around it.
And here’s the really cool thing: We think those big black holes form at the same time as the galaxy itself. As the zillions of tons of gas swirl around in the proto-galaxy, assembling itself into stars, some of it is falling into the nascent black hole in the center of that maelstrom. It forms a disk around the black hole, heats up, and starts to blast out a wind. This wind slams into the gas around it, all around it, blowing it hither and yon.
When the galaxy finally coalesces as a massive island universe of billions of stars, the motions of the stars themselves still have the fingerprint of the black hole’s wind imprinted on them, even billions of years later. And that wind may have helped trigger more stars being born as it rams into and compresses the gas around it, just as it can also shut down star formation by blowing that gas away.
Our galaxy, the Milky Way, has such a black hole in the middle. It’s not a big one as they go, a mere 4 million times the mass of the Sun. But 10 billion years ago, when our galaxy was forming, it may have been active, and may have affected the young galaxy around it as well.
When you go outside at night and look at the stars, think on that. If you can see Sagittarius, you’re looking toward the center of our galaxy, where that monster dwells. It’s surrounded by billions of stars, so distant from us their light merges into a soft glow. But they’re there, those myriad stars, and their motions, their formation, even their existence itself may have been profoundly influenced by a black hole that we didn’t even know existed until a few decades ago.
Ah, science. It allows us to wonder about the inner workings of the Universe we live in, and then shows us how the pieces fit together. If there is a grander, more exhilarating adventure than that, I don’t know what it is.
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2015年2月24日 星期二
Ask Me Anything (on reddit) About NASA's Budget
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Unusual Plumes Above Mars
UPDATE -- NASA Reschedules MMS Briefing to 3 p.m. EST Feb. 25
February 24, 2015
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NASA Briefing to Discuss First Spacecraft Arrival at a Dwarf Planet
February 24, 2015
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2015年2月23日 星期一
The Milky Way Over the Arizona Toadstools
Fixing ARM So That It Makes (Some) Sense
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NASA Hosts Media Briefing on Mission to Study Dynamic Magnetic System Around Earth
February 23, 2015
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Spacewalk Timelapse Makes Cable Routing Look Fun
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Jurczyk To Head Space Technology Mission Directorate
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Jurczyk Named Head of NASA Space Technology Mission Directorate
February 23, 2015
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Throwing Shade on Mars One
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Yet Another Space Group: The Space Illuminati
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NASA Briefing to Highlight Early Results from New Earth Science Missions
February 23, 2015
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Astronaut Barry Wilmore on the First of Three Spacewalks
Alliance for Space Development Revealed (Yawn)
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Commercial Space Hearings This Week
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Mooning Pluto
Pluto is an interesting little world. Smaller than our Moon, it still boasts no fewer than five moons discovered so far. The first, Charon, was discovered in 1978, but the second through fifth were found just a few years ago using Hubble data.
How many does Pluto have? It’s not known, because smaller, fainter moons may yet be undiscovered. But as the New Horizons probe nears Pluto, we may find more.
Charon is big and relatively bright, and has been seen in New Horizons images since 2013. But now two of the smaller moons, Nix and Hydra, have been spotted as well!
The animation on the left shows Pluto heavily overexposed (the bright tail off to the right is called blooming, and it’s an artifact of some digital detectors), with stars in the background. The moons have boxes around them to make them easier to spot. The animation on the right has the stars subtracted off, making it easier to see the moons’ orbital motions around their parent body. To give you a sense of scale, Nix and Hydra orbit about 50,000 and 65,000 km out from Pluto. The moon’s physical sizes are unknown, though less than 100 km across. They’re unresolved in these images, and in the Hubble images as well. When New Horizons gets closer it will certainly give us a far better idea about these little guys.
Each frame of each animation is a total of a 50 second exposure, which is pretty impressive. New Horizons is moving pretty fast, about 14 km/sec, so it needs to take short exposures as it flies through the Pluto system or else there will be motion blur.
These images are mere tastes of what’s to come. In the months ahead we’ll see Pluto resolved, surface features revealing themselves, and more detail on these moons as well. Perhaps the probe will discover more moons circling Pluto, too.
Hopefully it will shed light on how the moons formed; one current theory is that Pluto and Charon formed at the same time, out of the material that formed all the icy bodies past Neptune. Then, later, an impact on Pluto blasted chunks into space, which formed the other moons. Pluto doesn’t have a lot of gravity, but it also lacks nearby neighbors, so it can hold on to several moons without losing them due to perturbations from other massive bodies. We know many asteroids and other big icy objects past Neptune have moons, so seeing these close up may be able to help us understand how they came to be in the first place.
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2015年2月22日 星期日
The Dark River to Antares
Sonja Alexander Maclin
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Recent Space Poll: Public is Not Always in Synch With Space Advocates
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Conspiracy Revealed: The Simpsons Has Been Lying to You
I’ve been a fan of The Simpsons for a long time. Obviously. So when I heard that SpaceX’s head guy Elon Musk was guest-starring on the show, I hoped it would be a good episode. And it was! As I watched I marveled at how funny the show was even after all these decades, and laughed quite a bit as the story unfolded.
… until a scene came up that chilled me to the bone. I was so shocked that I had to rewind and watch it again, then freeze frame it to make sure I wasn’t hallucinating.
This is the moment that changed everything for me. The frozen moment of time when I realized that for 22 years, The Simpsons has been lying to us.
This shows Musk standing at the dining room window of the Simpson’s house, looking out and pontificating at the night sky as the family behind him eats dinner.
But look at the Moon. LOOK AT THE MOON!
It’s backwards. The scene is clearly at dinner, early evening, so that’s the setting crescent new Moon. But in the northern hemisphere, the tips of a waxing crescent Moon point to the left, away from the Sun. Here’s a photo I took myself in November 2013:
See? I took that picture shortly after sunset, around dinner time. It was new Moon, and the crescent's tips point to the left. But in that scene with Musk, they point to the right! How can that be?
There’s only one way. Springfield is not in the United States at all. It’s not even in our half of the world. Springfield is in the southern hemisphere!
I don’t even know how to react to this information. It’s as if… my whole world has been turned upside down.
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2015年2月21日 星期六
45 Days in the Sun
Pioneering Space National Summit Details Emerge
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Antares Explosion Might Not Be It's Engine's Fault
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2015年2月20日 星期五
An Evening Sky Conjunction
Curiosity update, sols 864-895: Drilling at Pink Cliffs
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Alliance for Space Development: Yawn - Yet Another Space Group
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John Glenn During the Mercury-Atlas 6 Spaceflight
Expedition 42 Spacewalks Postponed by a Day
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Crash Course Astronomy Episode 6: Telescopes
By number, I’d say I go outside and use just my eyeballs to look at the stars more than any other method. Every time I step outside, the first thing I do is look up. Even during the day: I wouldn’t want to miss the Moon, some Sun-induced optical phenomena, iridescent clouds, or maybe even the eye-wateringly hard-to-spot Venus in the clear blue sky.
And at night, there are familiar constellations, planets, the odd meteor or two, and satellites streaming overhead. These are all fun to see with your unaided eyes.
But there are times when a little magnification is needed. In those cases you’re far more likely to find me with binoculars up to my eyes, scanning the heavens for various objects. And then, when I’m feeling ambitious, out comes the telescope, in goes the eyepiece, and down goes my evening as I hop from one distant world to another.
But … how does a telescope work?
I’m glad you asked. Here’s my answer, cleverly embedded in this week’s Crash Course Astronomy episode!
I hope that helps! If you get anything out of that episode, let it be that telescopes help resolve objects, make fainter objects appear brighter, and let us see invisible forms of light. And before you ask, I have advice on how to buy a telescope, too.
That reminds me: An FAQ I get is, “What observing equipment do you use?” I have it on my list of Things I Need to Actually Write About Eventually When I Think About Them When I Actually Do Have Time to Write Them. And the list is longer than the title.
By the way, I'm extremely proud to say that Crash Course Astronomy passed a million total views this week! That's amazing to me. I'm really glad so many of you like the series. And I'm happy to say there are lots, lots more episodes to come. Here's the playlist of all the episodes so far. You can subscribe to Crash Course on YouTube, and don't forget subscribing to Subbable helps support the show as well.
Thank you to everyone who helps make this show happen. You are the Bernoulli effect above my wings.
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How LightSail Holds Its Place in Space
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2015年2月19日 星期四
Palomar 12
Why We Write to Congress
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Our Global Volunteer Network
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NASA, ESA Telescopes Give Shape to Furious Black Hole Winds
February 19, 2015
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Wolf Wrong on China - Johnson-Freese
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Magnetospheric Multiscale Observatories Processed for Launch
2015年2月18日 星期三
Dark Craters and Bright Spots Revealed on Asteroid Ceres
Mapping Europa
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New Horizons spots Nix and Hydra circling Pluto and Charon
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Is Mars Slowly And Surely Drawing Its Plans Against Us…?
Y’know, I’m not all that big on “Mystery Baffles Scientists!” kinda headline, but I have to admit, this scientific mystery is rather baffling.
What’s causing hundreds-of-kilometer-high plumes on Mars?
This is pretty weird. Amateur astronomers taking images of the Red Planet spotted cloud-like features well above the surface. And I do mean well; some are 250 kilometers in altitude. That’s way above where you normally find clouds.
They’ve been seen on multiple occasions, and by Hubble as well. They’re not image artifacts or some processing mistake in the pictures. They rotate with the planet, and are certainly real.
Mars has an atmosphere, though it’s thin, less than 1 percent of Earth’s pressure at sea level. It’s enough to stir up dust storms and other weather on Mars. It even can make clouds: As winds blow up the slopes of the planet’s huge volcanoes, for example, carbon dioxide can condense and form what are called orographic clouds (this happens on Earth too; I see it all the time since I live near the Rocky Mountains, with water instead of carbon dioxide of course).
Still, it’s hard to see how the Martian air could blow something like dust or CO2 as high as these plumes. It’s possible, though unlikely, that it could be some gas in the atmosphere that’s getting up that high, condensing, and forming reflective clouds.
But it’s just so far above what’s normally seen that this doesn’t hold water with me.
Another idea is that it’s auroral activity. Mars doesn’t have much of a magnetic field, but there are areas on the planet that do have stronger magnetic fields. The solar wind coming in from the Sun could be funneled into the atmosphere there, causing the glow. Although the press release doesn’t mention it, I suspect observing Mars in the ultraviolet might help; aurorae glow at those wavelengths.
You’d think that we have plenty of space probes orbiting the planet and that one of them would’ve seen something by now. The problem there is, in a way, being too close. The best way to see these things is on the edge of Mars, against the darkness of space. Most of the orbiting missions at Mars look straight down, and can’t see these plumes.
Not that observing them from Earth is all that easy. The problem is that these aren’t persistent features. They come and go, making observing them difficult. In cases like that, the best bet is brute force: Observe Mars a lot. Get as many telescopes observing it as often as possible and in as many ways as possible (imaging, video, different wavelengths, and so on). Small probability events become certainties given enough time.
I’d love to know what these things are. Giant plumes of gas erupting from Mars sounds little ominous to me. If there’s an observatory in Grover’s Mill, I hope it’s paying close attention.
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2015年2月17日 星期二
Fibrils Flower on the Sun
Space Advocates Work Together By Not Working Together
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Planetary CubeSats Begin to Come of Age
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Public Curiosity Talk in Boulder on March 2
Hey, Boulderites! I’ll be giving a talk about Mars and the Curiosity rover at the Chautauqua Community House on March 2, 2015, at 7 p.m. The talk, “Where Has Our Curiosity Taken Us,” is an overview of the mission loaded with cool imagery and fun science.
I’ve given this talk here and there, and I really have fun going over the amazing things we’ve learned since the rover touched down in 2012. I’ll talk about the launch and landing, the roving, the photos, and the science Curiosity has undertaken.
Tickets are $10 ($7 for concert members), and as I write this, about half the seats are already sold. If you want to come, better get a ticket soon! I hope to see some BABloggees there.
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Getting Closer to Ceres
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Getting Closer to Ceres
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Dawn Approaches: Two Faces of Ceres
Why Do Mirrors Reverse Left and Right but Not Up and Down?
I love brain teasers, especially when they’re based on real-world things we see every day but maybe don’t really think about.
I first heard of this one not too long ago: Why do mirrors reverse left and right, but not up and down? When you face yourself in the mirror, left and right are reversed, but you’re still right side up. Why?
The answer may not seem obvious because the question itself frames the problem incorrectly! It makes you try to solve the problem starting from the wrong premise. As it happens, Physics Girl has it covered:
Her use of written words and clothes is pretty clever, but the arrow was really good. That’s what makes it all clear: Mirrors don’t reverse left and right, they reverse in and out. Once you see that it all makes sense.
I really like demos like this; this connects physics to everyday life, and also shows that how you frame a problem is in many ways just as important as how you think about a problem.
I met Dianna, aka Physics Girl, last year at Comic Con; by coincidence I had just seen one of her videos and liked it. You should watch them; she has a knack for explaining things simply and well. I especially recommend the video about vortices in pools; it’s really cool, and these stable swirls of water are really fun to watch. I’ve spent some time in pools (and yes, in the bathtub) creating them and watching them propagate. They seem simple but are surprisingly complex phenomena, especially in how they interact with light.
And why not, here’s the video:
I’d suggest subscribing to her videos, and checking out her website, too. In my opinion, we can’t have enough good people out there communicating fun science. If you know of more, leave a comment below! I’m always looking for that sort of thing.
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2015年2月16日 星期一
M106: A Spiral Galaxy with a Strange Center
Rosetta Dips Low Over an Alien World
On Saturday, Valentine’s Day, the Rosetta spacecraft dipped down low over the comet 67P/Churyumov-Gerasimenko. How low? At one point, it was less than nine kilometers from the surface!
Given that the comet is 4.3 kilometers long and shaped like a rubber ducky that’s been sitting in the Sun for four billion years, this was a pretty low and gutsy pass. It was done to get extremely high-resolution pictures of the comet, of course, but the spacecraft will also be making a series of more distant passes to sample the environment around the comet at different locations.
Around the time of closest approach, the lower resolution NAVCAM instrument was used to snap photos of the comet. One of them showed the very, very weird Imhotep region of the comet, and, well, see for yourself:
Yeesh. What a mess! Imhotep is the name given to the broad, flattish area on the outer part of the bigger of the two lobes. The resolution on this image is staggering; it’s about 0.76 meters per pixel. A human standing on the surface would be just under three pixels long.
As you can see, the surface is ragged, littered with boulders, some the size of houses. There are two features in particular I want you to see.
That’s a closer view of the flat area at the upper left of the big picture (bear in mind I am not a cometologist, so I’m speculating a bit here; hopefully we’ll hear more from the Rosetta scientists about these features). This may be where ice under the comet’s surface is turned into gas when warmed by the Sun. As the gas escapes the comet, it leaves behind dust and gravel that can flow around; this may be a low spot in the surface that has been filled. Note the smooth area stops on the left just like water at a shoreline. But it’s not like a liquid, really; note the sharp step in the middle, a scarp that may be a slight collapse feature, where the ground suddenly gave way. It looks to be a few meters high.
The cliff-like region at the upper left looks very much like it’s been eroded, but not like it happens on Earth. There’s no water flow! In this case, it seems more likely that as ice turned to gas, the material erodes back, into the cliff, leaving behind the rocky material. Also, the those boulders may be chunks that have fallen and rolled into place, or exposed as icy material around them turns into gas and blows away.
Another fascinating area is this one:
Note the layering! On Earth or Mars (y’know, normal places) I’d wager a feature like that is from sedimentary action; deposited season after season by rains and flooding bringing sediment into a lake. But on a comet? I’d guess that this represents the exact opposite: As the comet orbits the Sun on an ellipse, it gets farther and nearer to our star. When it gets closer, the ice near the surface turning to gas will drop the surface down a bit, and that stops as the comet moves away from the Sun. Then the cycle starts up again, over and over. The plateau is probably rockier material, exposed more and more every orbit as the ice goes away.
Note also the circular crater-like features to the right. Those almost certainly aren’t impacts! More likely they are where gas is escaping the comet, the pits forming and growing over time as the area around the venting region loses ice.
Comets are really strange. They have extremely low gravity, their orbits determine their seasons, their erosive properties are backwards. That’s why I want to be clear with my caveats about not being a comet scientist! Places like this are hard enough to interpret by the experts, and my guesses might be wildly wrong. What I’m hoping to do here is to get you thinking about what you’re seeing, and to understand that we’ve never seen a comet’s surface in detail like this before. Ever.
There’s a huge amount to learn, and it’s essentially all virgin territory, all alien and bizarre. Shakespeare was right: There are more things in heaven and earth than are dreamt of in our philosophy.
I’ve always interpreted that to mean Nature is more clever than we are, and we will always be surprised by what we find when we explore the Universe… but we’re clever too, and just because we didn’t imagine something a priori doesn’t mean we can’t figure it out a posteriori.
Here are the photos of Nature’s imagination. Now we let the science get to work.
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Let Me Hold You in My Anomalous Arms
It’s been a while since I have slammed your brain with a huge and gorgeous spiral galaxy, so here’s the brain-slamming gorgeous and huge M106:
Oh my.
This mosaic was created by astrophotographer André van der Hoeven, using a combination of images from Hubble, the Canadian-French-Hawaii Telescope, the 1-meter telescope of the Tzec Maun Foundation in Cloudcroft, NM, the Subaru telescope, and an RCOS 51-cm telescope. vd Hoeven lists the details on his Flickr page for the image—and you can grab the ridiculously big 4,626 x 4,152 pixel version there, too.
I suggest you do take a look at that biggest version, because wow. The galaxy itself is incredible. I’ve written about it before—twice, actually. It’s a spiral about 25 million light years away, more or less in our own neighborhood, and about the same size (or somewhat bigger) than our own Milky Way. At its core is a monster black hole 30 million times the mass of our Sun. It’s actively gobbling down matter, and, as it happens, black holes are messy eaters.
As the matter falls in it gets ferociously hot, and all that energy powers two beams of matter and energy that blasts out from the black hole in opposite directions. Those beams slam into matter in the galaxy, heating it and causing it to glow: That’s why you see those weird red spiral arms that don’t align with the arms of the galaxy itself (which is why they’re called “anomalous arms”). That’s material that’s essentially being cooked by the energy from the black hole. If there are any planets orbiting stars there, I wouldn’t be too interested in investing in them for real estate. Lethal doses of X-rays tend to lower market resale value.
You don’t even have to look at M106 to be in awe of this pictures either; scan around the background and you’ll see hundreds of galaxies, far, far away, some are hundreds of millions or even billions of light years distant.
I’m seeing more images like this all the time; a lot of astronomical data are public, and if you know what you’re doing you can combine them from vastly different telescopes to create amazing shots. But there’s science in here, and a lot of it! Astronomers can study specific parts of a galaxy, but putting them in context can reveal wonders as well. Objects in the galaxy that are too small to see in wide field images can sculpt structures on much larger scales, so putting them together can give us insight into events and connections that might otherwise be unnoticed.
Making the invisible visible is one of the things astronomy does best. And when it does, you can see beauty you didn’t even know existed.
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2015年2月15日 星期日
Two Hours Before Neptune
2015年2月14日 星期六
Solar System Portrait
Crash Course Astronomy Episode 5: Eclipses
I have friends who tell me that seeing a total solar eclipse is literally life-changing; the serene beauty and majestic clockwork motion of the cosmos unfolding above you is transformative, showing you viscerally the connection between you and other objects in the Universe.
I wouldn’t know. I’ve never seen one.
But that won’t stop me from talking about them! So, just for you, here is ten minutes of me expositing on eclipses both solar and lunar in Crash Course Astronomy Episode 5:
In the video I mention you can get safe solar viewing glasses online; you can order them from Astronomers Without Borders and from Rainbow Symphony (I have these myself, and I believe that’s what I was wearing in the video). Rainbow Symphony has a wide range of other viewing apparatus as well.
And what I said is the truth: I’ve never seen a total solar eclipse for myself. I’ve seen lots of partial ones, but it’s not the same. I think my best chance will be in 2017, when the path of totality crosses the United States, cutting through a lot of places where the weather will almost certainly be good for viewing. It goes through Wyoming, just a few hundred kilometers north of my house, and that may be where I sojourn to see it.
You’ll be hearing a lot more about the 2017 eclipse in the coming couple of years. Make sure you bookmark this Crash Course Astronomy video so you can watch it again when the time comes!
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2015年2月13日 星期五
Aurora on Ice
Move Along. This Is Not The Space Policy You're Looking For.
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A Fresh Approach to Fundraising
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Media Invited to Boeing Commercial Crew Access Tower Groundbreaking
February 13, 2015
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An active comet, from a distance
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Growing Deltas in Atchafalaya Bay
2015年2月12日 星期四
Exploring the Antennae
Cassini begins a year of icy moon encounters with a flyby of Rhea
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NASA Study Finds Carbon Emissions Could Dramatically Increase Risk of U.S. Megadroughts
February 12, 2015
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Hearing: Problems With U.S. Weather Satellites
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NASA TV Previews and Broadcasts Space Station U.S. Spacewalks
February 12, 2015
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In Pictures: DSCOVR Headed for Deep Space
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NASA's Stratospheric Observatory for Infrared Astronomy
A Seagull Flies on a Dusty Ion Wind
Robert Gendler is an astrophotography whose work I’ve featured here many times (he helped assemble a jaw-dropping Hubble Andromeda Galaxy picture, for example). One area in which he excels is taking data from multiple big telescopes and merging them to create new views of the heavens.
His latest is a stunner: the aptly-named Seagull Nebula:
Can you see the shape of a gull in that? The head is the knot of gas to the left, and the wing shape is obvious enough. In this photo it actually looks more like a parrot to me, but that’s OK. A bird in the hand…
This is actually a vast star-forming region, a huge factory of gas and dust that is collapsing in various places to create newborn stars. Many of these stars are massive and hot, shining blue. They heat the gas up, exciting it (as we say in astronomy); the cloud is mostly hydrogen, which glows a characteristic pinkish-red when flooded by this starlight.
There’s also quite a bit of dark dust in this cloud, opaque to visible light. But the stars are so bright their light can reflect off it, and you see blue fuzz. The head of the gull is a lovely combination of both emission (red) and reflection (blue) nebulae.
Some features of the nebulae were puzzling me, so I poked around to look for other images, and found this one taken by NASA’s Wide-field Infrared Explorer (WISE):
The overall shape is the same, but there are big differences. This image is taken in the far-infrared, where the normally opaque dust glows. It’s actually a bit tough to match up features, since stars that are cool and faint in Gendler’s photo blaze away in the WISE image (and the WISE image is rotated clockwise slightly compared to the visible light image). Worse, what’s dark in Gendler’s image is bright in the WISE image, but some places are bright in both.
But note the bright blue star (called vdB 95) in the top image, located near the center bottom; it’s the brightest star in the field. See the fuzzy ring directly around it? I thought that was a reflection from inside the telescope (which is what causes the larger, sharper but fainter blue halo around it). It turns out that ring is real! You can see it in the WISE image, as well as a red arc. I suspect that star is moving at high speed through the gas and dust, and also blowing off a wind of material (like the Sun’s solar wind). That commonly causes such arc-like features in WISE images. Phenomenal.
Comparing the two, you can see other regions where stars are buried in gas and dust, and therefore are probably very young, still ensconced in their birth cocoons of material. As those stars age, their winds of subatomic particles and ultraviolet light will eat away at the dust, blowing it out, creating cavities in the nebula. Eventually the stars will wander out and travel the galaxy on their own. Thinking of them as chicks leaving the nest seems apropos for the whole theme here.
It’s possible our Sun was born in a cloud like this, our siblings and the nursery long since gone. I love soaking in the beauty of objects like this, but it’s hard not to stop and wonder that once, eons ago, we too were literally part of something like this.
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2015年2月11日 星期三
M100: A Grand Design Spiral Galaxy
Europe's Experimental Spaceplane Completes Successful Test Flight
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Giant Filament Seen on the Sun
Faces in the Sky
What does an accomplished astrophotographer do when it’s cloudy for over two months in a row, and getting new photos of the night sky is impossible?
Why, play with pictures already taken, of course. But J-P Metsävainio did more than that: Looking through his amazing collection of gorgeous astronomical photos he’s taken over the years, he started seeing familiar objects in the nebulae, galaxies, and other cosmic objects. With time on his hands, he created a really, really funny gallery of cosmic pareidolia; things that look like other things.
As they say, a picture’s worth a thousand words. The photo at the top of this post is a great example of seeing faces in objects (that's part of the Veil Nebula, the expanding debris from a supernova, and it's several light years across), but I have to admit, Metsävainio is on to something with this shot of the Red Ghost (aka IC 63):
Some of his examples are well-known, like the Pelican, the Heart, and (seriously) the Pac-Man nebula. But he has a lot of others that took a bit of imagination, but are obvious once you see them. Several made me laugh...
If I had to pick a favorite, I’d go with this one, because I don’t know why but it’s perfect and weird and I never would’ve thought of it myself:
Ha!
This idea of seeing familiar objects in patterns is pretty common in astronomy; we’ve named tons of objects after their remarkable (or even seriously vague) resemblance to other things. Heck, that’s what constellations are! And it does help us remember and discuss them more easily. Of course, pareidolia can go wrong, and often does… but sometimes it also goes very, very right.
So take a look at Metsävainio’s gallery, and after that bit of fun, treat yourself and take a look at the collection of images he took in 2014. They may not all look like other things, but they all do look like is gorgeous.
… and one more thing. When you’re done there, prepare to have your brain melted with his 3D rotating image of the nebula IC 1396. You’re welcome.
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