Bad Astronomy
The entire universe in blog form

June 18 2016 9:00 AM

Blue Origin to Test Rocket Parachute Failure Sunday Morning

Update, June 19, 2016, at 13:00 UTC: The launch was a success! The peak altitude reached was more than 101 kilometers, passing above the Kármán line and into space. The crew capsule deployment looked good, with the two main parachutes slowing the capsule adequately (we’ll know more when the data are analyzed) and the capsule touching down about 10 minutes 30 seconds after launch. One note:The capsule appeared to land too soon, and I'm not sure the retrothrust system activated. We'll know more soon. The rocket itself landed vertically right on target, too.

On Sunday, at approximately 14:15 UTC (10:15 a.m. Eastern time), the private rocket company Blue Origin plans to launch its New Shepard rocket for the fourth time. As with the three previous tests, it’ll launch straight up, deploy the crew capsule, and then come back down vertically. The crew capsule will come back much more slowly, using parachutes to descend gently (and a retrothrust system to make sure the landing isn’t too rough).

Except this time, the company has rigged it so that only two of the three parachutes will open.

This test is being done on purpose to make sure they can still safely land in the event of single parachute failure. As Blue Origin CEO Jeff Bezos said, “Works on paper, and this test is designed to validate that.”

This should be an exciting test. In a very different move for the company, it has announced that it will be streaming the event live on its website (it starts at 13:45 UTC, a half hour before the launch). I find that very interesting; in general the company has not done that; they release video after the flights, and rarely even announce when the launch tests will be. I wouldn’t say they’re secretive, but they tend not to actively seek publicity.

I have to wonder if the live coverage of SpaceX launches is behind this decision. Obviously, SpaceX has captured the lion’s share of the public’s attention when it comes to rocket launches. SpaceX has carefully cultivated an excellent public outreach effort, and the result is that its launches are watched live by a lot of folks. I imagine Blue Origin wants a piece of that.

They deserve it. New Shepard (named after astronaut Alan Shepard, the first American in space) has launched successfully three times, and each flight has tested different aspects of the process, including a quick restart of the engine only a kilometer above the ground before landing. It’s actually pretty amazing.

What SpaceX is doing and what Blue Origin is doing are, at the moment, very different. SpaceX is launching a very large rocket into orbit, meaning it has to go sideways (usually to the east) very rapidly to go around the Earth. Blue Origin’s flights are suborbital; the rocket goes essentially straight up, past the arbitrary but generally agreed-upon 100-kilometer altitude marking the beginning of space (at that height, there’s almost no air and no drag on the rocket). That’s far easier than going into orbit.

But not easy. Going up that high, releasing a capsule, having that land safely, and landing the rocket itself back down vertically on its tail is incredibly hard. Blue Origin has shown they’re getting the hang of it, though.

And while there’s a good market for suborbital flights (even a few minutes of free fall can be very useful scientifically), the plan is to use the knowledge gained to create a more powerful rocket capable of orbital flight. This is how SpaceX did it with the Falcon 1 rocket that led to the Falcon 9, and Blue Origin has similar ideas. Its BE-4 engine, currently being tested, should have enough oomph to do this. United Launch Alliance, which makes the Atlas and Delta rockets, has partnered with Blue Origin to develop this engine for use with their next generation Vulcan rocket. That’s being created as a competitor for SpaceX’s Falcon series, and I’ll be very interested indeed to see how this goes.

I’ll be getting up early Sunday morning to watch this fourth New Shepard test flight, and live tweeting it, too. Rocket launches are fun and exciting, and these tests are the first steps toward a bigger and better arena for commercial spaceflight. I have a lot of hope for this new chapter in space exploration. A lot, and I think it’s been earned.

There’s an (apocryphal) curse: “May you live in exciting times.” I don’t think it’s a curse. I think it’s the best time to be alive.

June 17 2016 9:00 AM

Another Moon for Earth? Well, Not Really, but It Depends on Your Point of View.

The Earth has one satellite, right? That fact is so solid, we just call it the Moon with a capital M.

But due to a trick of gravity and timing, there are other objects out in space that aren’t really moons but do travel along with Earth through space. I guess “companions” would be a better name.

One of them was just discovered recently by astronomers: the asteroid 2016 HO3. It’s small, probably 40–100 meters in size, and let me be clear: It orbits the Sun, not the Earth, so I wouldn’t call it a moon. But its orbit is such that it always sticks near the Earth, and from our point of view even seems to go around us!

Here’s how that works. The asteroid was first seen in April 2016 in observations of the sky taken by the Pan-STARRS observatory, designed to look for asteroids and comets that get close to Earth. That’s recent enough that a really good orbit for it is hard to determine, but it turns out it was seen in older observations (those can be found by tracing the orbit backward and checking if any observations of it were archived), providing a much longer baseline and therefore a better orbit.

What they found is really interesting: The orbit of HO3 is very Earth-like! It’s very slightly elliptical, and tilted by about 8° with respect to Earth’s, but the average distance of the asteroid from the Sun is just a hair more than Earth’s, and it takes 365.93 days to orbit the Sun. That’s just 16.6 hours longer than Earth’s 365.24 daylong year!

Because it’s moving on a tilted and elliptical orbit, sometimes it’s a wee bit closer to the Sun and moving a bit faster than Earth, and sometimes it’s a wee bit farther out and moving a bit more slowly. But it never gets closer than about 14 million kilometers from Earth or farther than about 40 million kilometers.

That’s hard to picture, so I made an animation using the JPL Small Body Database Browser. It shows the inner solar system and keeps Earth centered as it and 2016 HO3 orbit the Sun (HO3’s orbit is blue; light blue for when it’s north of (“above”) the Earth’s orbit, and dark blue when it’s south (“below”). As time moves forward, you can see HO3 moving faster and ahead of the Earth, then slowing and lagging behind, but never getting very far away:

So as you can see it’s clearly orbiting the Sun, but never straying far from Earth. If you map its motion relative to Earth, it actually appears to go around us, like a moon! That’s shown in the diagram at the top of this article.

But it gets weirder. Because the orbit is slightly longer than Earth’s, you’d expect it to drift away over many years, lagging behind Earth more and more every year. But that’s not the case! Earth’s gravity tugs on HO3, changing the orbit slightly every time they pass. That keeps HO3’s orbit in line with Earth’s, so it never gets too close or too far away. It’ll be our companion for at least the next few centuries.

If you’re wondering how we’ve missed it all this time, I’ll remind you it’s small and still pretty far away in terms of actual kilometerage. Even at closest approach it’s at about 21st magnitude, or just one-millionth as bright as the faintest star you can see with your unaided eye. It takes a decent telescope to see it at all.

I find things like this delightful. The Universe is so surprising! Due to the law of gravity our solar system is in many ways like a clock, each object like a gear ticking away in time with the others.

But there’s more than fanciful analogies to be had here: Because of its similar orbit, HO3 is moving relatively slowly compared with Earth’s motion through space. That makes it a rather tempting target for a space mission, where how much fuel you need to get from point A to point B depends on their relative motion. HO3 is moving just a few kilometers per second relative to Earth in some parts of it orbit, making it much easier to send a probe there. Or maybe, someday, humans.

How about that? One of the best targets we could hope for, and we just discovered it a few weeks ago. The Universe really is surprising.

June 16 2016 9:00 AM

LIGO Bags Another Binary Black Hole Burst

About 1.4 billion light-years from Earth, two black holes were on a dance of death. One was about 14 times the mass of the Sun; the other eight. For a long time their orbits had been decaying, approaching each other ever more rapidly. And then, finally, so close they were whipping each other around at very nearly the speed of light, they merged. The event was catastrophic, sending out a blast of energy that literally shook the very fabric of the Universe itself.

Eons later, that death cry was seen by astronomers here on Earth. By the time it got here it was vanishingly feeble, but strong enough to shake the sensors in LIGO, the Laser Interferometer Gravitational-Wave Observatory. Two facilities comprise the observatory, one in Livingston, Louisiana, and the other in Hanford, Washington. Each one uses a system of lasers to measure the distance between a set of mirrors, and when the ripples in space-time emanating from the black hole merger passed through the Earth, they changed the distance between mirrors ever so slightly.

Perhaps I’d better explain. In fact, I already have, when the first event was announced in February 2016:

One of the outcomes of Einstein’s General Relativity theory is that space and time are two facets of the same thing, which we call space-time. There are lots of analogies for it, but you can think of it as the fabric of space, a four-dimensional tapestry (three of space and one of time) in which we are all embedded. Remember, it’s not literally like this; we’re using an analogy. But it’ll help you picture it …
… if a massive object is accelerated, it will cause ripples, waves, to move away from itself as it moves. These are actually ripples in the fabric of space-time itself! Space-time expands and contracts in complicated ways as a wave passes, a bit like how ripples will move out from a rock dropped into a pond, distorting the surface of the water.

In other words, when a massive object accelerates, it emits what’s called a gravitational wave that quite literally stretches and shrinks space. The more massive the object and the higher the acceleration, the more powerful the gravitational wave is, and the more space gets distorted. Most objects in the Universe are way too placid to do this, but when two black holes merge, the masses are high and the acceleration fierce.

Even then, by the time the waves get here (moving at the speed of light across the Universe), the ripples are incredibly tiny. The ripples from this new event, called GW 151226 (for the gravitational wave source detected on Dec. 26, 2015), stretched space by only a factor of about 10-22 by the time they reached Earth. That’s so small it’s hard to imagine, so let me put it this way: If you had a ruler a kilometer long, as a ripple passed through, it would change its length by less than the width of a proton!

Still, that’s measurable! Barely. As I described in my earlier article, LIGO is designed to see incredibly small strains in the fabric of space-time. The biggest problem is noise; in this case the detectors are so sensitive that they can detect molecules of air hitting the mirrors!

It’s taken many years, but last year LIGO was finally made sensitive enough to detect the more powerful gravitational waves passing through it. The first detection, made on Sep. 14, 2015, was from two pretty beefy black holes, roughly 36 and 29 times the mass of the Sun. The event lasted two-tenths of a second.

In this second case, the entire detected event lasted about a full second. As the black holes fell in those last few kilometers, their fierce gravity swung them around faster and faster, causing the gravitational waves to increase in frequency and strength. When sound waves do this, you get a sharp, short “chirp,” and that’s what astronomers call this event, too.

The detection itself is pretty amazing. Automated software checks the signal from the LIGO setup and was the first to notice something was up. It alerted astronomers, who checked to make sure the signal was real. Part of that was looking at the signal from both facilities in Washington and Louisiana, and they both saw it (it was first seen in Louisiana, then in Washington 1.1 milliseconds later; that has to do with the speed of light and the angle to the merging black holes).

signal from the black holes
Top: The signal detected by the LIGO facilities (in red and blue), with the best predicted fit model calculated using Einstein's equations. Bottom: The energy of the signals is hard to see over the noise, but the frequency ramping up into chirps is discernable.


Note that in the plot above, a pair of up and down cycles is one orbit of the black holes around each other. These objects combined are 20 times the mass of our entire star, but they were whipping around each other hundreds of times per second before the end.

The exact shape of that signal is predicted by Einstein’s Theory of General Relativity. Using computers, the astronomers then generated literally millions of theoretical signals, comparing them to the observed one. They change the masses of the black holes, as well as many other parameters, giving them a range of values for their masses and distances. In the end, the masses found were 14.2 ± 8.3/3.7 (so as much as 8.3 more and 3.7 less) and 7.5 ± 2.3/2.3 times the mass of the Sun, and the distance roughly 1.4 billion light-years.

This means the black holes were probably created in the usual way. A long time ago, two very massive, hot stars were in orbit around each other. One blew up, expelling its outer layers, and its core collapsed to form a black hole. Sometime after that the second one blew, creating the other black hole. They would have orbited each other stably forever, but Einstein has something to say about that: As they moved, they emitted those gravitational waves. The emission was very weak at first, but it removed energy from the system, and the black holes spiraled every so slightly closer together. As they got closer they moved faster, were accelerated more, and emitted more waves. This was a positive feedback loop, and when they got close enough together, BLOOP! They merged.

The 14 and eight solar mass black holes combined to form a single black hole with 21 times the mass of the Sun.

Of course, 14 + 8 = 22. What happened to the missing mass? That mass was converted into the energy of gravitational waves.

I’m not going to lie to you: Just writing that gave me a chill down the back of neck.

That amount of energy is beyond staggering: It’s equivalent of all the energy the Sun emits over a period of about 15 trillion years. That’s a thousand times the lifetime of the Sun! Or, if you prefer, it’s about the same amount of energy emitted by a billion galaxies like ours over the same time interval as the merger.

And now you can see why astronomers are so excited by this. These are among the most energetic events in the Universe, and until last year we were completely blind to them.

The first event showed we could do it. This second event shows that the age of gravitational wave astronomy is truly here. Mind you, both events were detected just a few months after LIGO became sensitive enough to detect them; many more will be seen, and soon. As data are gathered, we’ll learn more about this entirely new field of astronomy, one completely divorced from the usual detection of electromagnetic waves—light. Certainly, conventional telescopes will help; it’s suspected there may be a brief flash of light accompanying the release of gravitational waves, but it’s not certain. And just on their own, gravitational waves yield a treasure of information.

This is an amazing event. Predicted by esoteric physics a century ago, detected by physics even older than that, we finally have the technology that allows us to hear the faint whispers the results from these deafening roars. And it will allow us understand the universe in a whole new way.

June 15 2016 9:00 AM

A Dying Star Metamorphoses Into a Butterfly

When a star dies, it can be lovely.

When a star dies with another nearby, it can be amazing.

The image above shows Hubble 12 (also called HB 12 for short), what astronomers call a planetary nebula, the gas and dust thrown off by a star as it ends its life. When the star runs out of fuel in its core needed to generate the energy it uses to sustain itself, the outer layers of the star can be thrown off in a series of winds, like a solar wind on steroids.

This can form odd and intriguing shapes, including hourglass figures, elongated figures like two squids kissing, and even more bizarre objects.

But HB 12 has an extra ingredient or two. One of them is that the star in the center isn’t one star, but two. They orbit each other pretty close together, their orbital velocities high. This can help shape the wind blown out by the one star that’s dying; it adds a component of centrifugal force. Most of the material flung out goes out along the orbital plane of the two stars, forming a disk. Other stuff hits this disk and flows up and away, forming the hourglass figure.

Another ingredient is the fact that HB 12 sits in a region of the galaxy thick with interstellar gas and dust. Some observations indicate there’s quite a bit of it surrounding the stars, and the wind is plowing into that material, which confines it. That may be why the edges of the shapes you see in the image are so well defined. It also makes the nebula denser, and therefore brighter; HB 12 has one of the highest “surface brightnesses” of any nebula—that means any given piece of it is pretty bright compared with the same size section of another nebula.

But there’s a lot more going on here. If you look at the inner nebula, the part that looks like a butterfly, you can see brighter rings going around the cone-shaped “wings” (reminding me of the old Rocketdyne F-1 engines used on the Saturn V rocket). Each one of these may have been due to a gust of wind from the star, an episodic hiccup that temporarily increased the amount of material blown out. Given the spacing in the rings, they probably occur every 50 years or so. So twice a century the star went through some sort of event that increased its outflow. It’s not clear what that event might be.

Those outer structures, though! What a mess. But if you look carefully, you see symmetry. For every U-shaped structure you see, there’s an upside-down U to match it. That’s because every time the star blows out material, it does so in both directions, up and down. That might be more clear in a grayscale version of the image:

Hubble 12
The same as the image above, but only using the infrared data, and displayed in grayscale.

NASA/ESA/Judy Schmidt

The exact cause of all these structures has me scratching my head, though. The eye-shaped oval in particular is weird. I’d expect that to be an ellipse, a circle of expanding material seen at an angle (like looking at a water glass from an angle makes the circular opening appear like an ellipse). However, in this case it has sharper cusps on the left and right. That might simply be due to a weird perspective; the gas here is thin, and you can see through it, so you’re seeing the front and back side of the nebula on top of each other.

So that wide open structure on the outside is probably much like the inner, bright butterfly structure. Perhaps it’s just older and has had more time to spread out. If that’s the case, I see at least three such structures here, which hints that the dying star has had a lot of increased activity over the years.

And this I find particularly interesting: Just outside the central bright point marking the star’s position, you can see two parallel circular features, one just above and one just below the star. That reminds me very strongly of NGC 1514, another planetary nebula:

NGC 1514
NGC 1514, seen here using the WISE observatory in infrared, is one of my candidates for Weirdest Thing in the Sky.


As I wrote then, such features aren’t well-understood. What shapes them, why are they on opposite sides of the star like that, why are they so bright? It’s not clear.

Actually, there’s a lot that’s not well known about this object. We’re not even sure of its distance! Various methods to measure that yield wildly different results; everything from 7,500 light-years to more than 25,000 light-years! I suspect it’s probably on the closer end of that range, but who knows?

Here’s another interesting thing: This nebula is young. Measuring the speed of the expansion of the features and then tracing that back,* the age of the nebula is probably more than 1,000 years. That’s consistent with what we know about such objects; the gas is thrown out pretty quickly, and the planetary nebula stage of a dying star lasts millennia at most. The expanding gas becomes too thin and too distant for the star to light up, and the nebula fades.

I love planetary nebulae; I studied them both for my master’s degree and Ph.D. Very little was known about them before the advent of digital cameras, they’re pretty faint and small. But now we have extremely sensitive detectors and telescopes like Hubble, capable of imaging their fantastic structures.

And one last thing: The images you see here of HB 12 were processed and constructed by Judy Schmidt, who likes to reprocess data from the Hubble Space Telescope and create beautiful images. Her work has been featured here on the blog many times, and you can also see her creations on her website and on her Flickr page. Follow her on Twitter to get the latest updates, too. We had a fun conversation about this nebula, and I hope she tackles more such objects in the future.

*It’s a bit like knowing how far you’ve driven knowing your speed and how long you’ve been on the road. If you know the size of the nebula and how quickly it’s expanding, working the math backwards gives you the age.

June 14 2016 9:00 AM

Will SpaceX Be on Its Way to Mars by 2018? Maybe. But That’s Not the Point.

In May, Elon Musk announced that SpaceX would be sending a Dragon capsule on its way to Mars by the end of 2018.

That’s pretty ambitious. After all, 2018 is soon.

But is it too soon? I wrote an article about Musk’s plan to go to Mars, and I still think SpaceX can do it. But can do it isn’t the same thing as will do it. The problems are essentially twofold: The hardware they’ll use to go to Mars (mostly the Falcon Heavy rocket and the upgraded Dragon capsule) is still untested, and the fact that, to coin a phrase, stuff happens. By that I mean the winds of chance: a launch delay, a wonky part that refuses to be diagnosed, a lawmaker who has a NASA rocket facility in their district and doesn’t want the competition … these can all add weeks or months to the countdown.

So when Taylor Quimby of the New Hampshire Public Radio show Word of Mouth called me to talk about it and settle a bet he had with his colleague Sam Evans-Brown, I tried to explain this all carefully.

In the end, the distinction I’m trying to make is that yes, SpaceX can get to Mars, and possibly even launch the mission before Dec. 31, 2018. But it seems to me, given the reality of the situation, it’s quite likely it’ll happen in 2019 or later.

Ask me again after the Falcon Heavy goes on its first voyage, and the upgraded Dragon is built and tested, too. Once SpaceX gets those up and running, well, the sky’s no longer the limit.

As I said in the interview, the real question is: Who will put humans on Mars first, NASA or SpaceX?

NASA’s plans to go to Mars are a bit vague but rely on the Space Launch System to do it (full disclosure: I’m not a big fan of SLS). Like the Falcon Heavy, SLS has not yet launched, and the first flight is planned for late 2018 (barring delays, of course). NASA doesn’t plan to have humans on board an SLS flight until at least 2023, with a Mars flight perhaps sometime “in the 2030s.” Musk recently announced he wants to put humans on Mars by 2024, another ambitious but potentially doable deadline. Even if delayed several years, SpaceX would have an edge over NASA.

The situation with SLS and Falcon Heavy is complex, and more than I want to dive into here; a longer, more thorough post will come where I lay out my current thoughts on it. But in the meantime, to be clear: The deadlines Musk has laid are ambitious but achievable, and even if they aren’t met, the ability of SpaceX to go to Mars and eventually put humans there should not be discounted.

It’s the way to bet.

June 13 2016 11:55 AM

Orlando: What Can You Do in the Face of Another Senseless Gun Tragedy?

On Sunday, the country woke up to another horrific crime: a mass shooting in Orlando, Florida. A man who legally purchased guns just days before walked into a gay night club and shot more than 100 people, killing 49.*

By now you’ve heard the story, read the articles, perhaps even listened to the president, sounding tired and at a loss after having to make a variant of this speech more than a dozen times since talking office.

There have been a lot of updates since that morning, and there will be more to come. Twitter was its usual self, both an excellent and abhorrent example of the good and the awful in humanity.

I don’t usually comment very much in social media about such things, mostly because it tends to erase subtlety and flatten layers of meaning. But like so many others, I couldn’t stand by, silent. So I composed a series of thoughts and laid them out on Twitter and Facebook.

The gay community has made some huge strides in the past few years, with love mostly winning out over bigotry ... in the legal system. But that undercurrent of homophobia, especially in state governments, is still there. And we've seen this ugliness still bubbling up to the surface ...

By this I mean the ridiculous transgender bathroom laws that are getting so much airtime (and which, incidentally, are unconstitutional). Given that there's never been a recorded case of a transgender person attacking a child in a public restroom, the purpose behind these laws, so heavily promoted by state-level GOP politicians, is obvious: scare people, and get them to the voting booths come November.

Of course people want to send their thoughts and express their grief; that's natural and very human. But it's cynically hypocritical when politicians do it and nothing else. Congress made it extremely difficult for the Centers for Disease Control and Prevention to even study the effects of gun violence. Seeing all the NRA-funded lawmakers tweeting their "thoughts and prayers" was particularly galling.

Take special note of how politicians reacted after the shooting. Watch President Obama's calm speech again. Note how he calls this event a shooting and specifically mentions the LGBTQ community.

Contrast that with Donald Trump's response, who made a series of appalling tweets about the event, then released an unhinged statement about "radical Islam," saying Obama should step down, and then gave an interview on Fox strongly implying conspiracy ideations about the president.

Contrast that with Hillary Clinton's response, which was far more measured and reality-based. She understood that information was (and is) still lacking, and going off like tainted batch of fireworks not only is the wrong thing to do, but it actually makes things worse. As my Slate colleague William Saletan wrote in the link above, hate against Muslims is what ISIS wants. And also note that, like the president but unlike Trump, Clinton didn't hesitate to talk about guns in her reaction. She addressed the actual situation, not some fantasy spun out of conspiracies and hatred. 

Who sounded more presidential? 

Also, if you want to donate money to help, Equality Florida, the state's (LGBTQ) civil rights organization, has set up donation page on GoFundMe. They also have information there about other ways to help.

Not long after I posted those tweets, my friends at STARtorialist posted the image of a heart I used at the top of this article, and it really struck me, so I retweeted it.

Inside the heart is the spectrum of the Sun, composed of light from all of its constituents inside it and mixed together, shining down on Earth. If there’s a metaphor there, feel free to ponder it.

So, to reiterate, how to help:

*Update, June 13, 2016: This post has been updated to more accurately reflect the death toll from Sunday's shooting. Earlier reports of 50 victims included the shooter, but it’s standard practice not to list the perpetrator as a victim in these situations.

June 13 2016 9:00 AM

Akatsuki Reveals a Hot, Dynamic Venus

That stunning image above really threw me for a moment. If I hadn’t seen the caption first, it seriously would’ve taken me a second or two to figure out what planet it must be.

That’s Venus. Honestly, I’ve never seen an image of our sister planet that looks anything quite like that (well, maybe just a little; see below). Usually Venus just looks, well, white. In visible light, at least, the kind our eyes see. Sometimes you can see subtle features, but nothing like this.

That shot was taken by the Japanese Akatsuki (“Dawn”) spacecraft, which entered Venus orbit in late 2015. This part is amazing: It was launched in March 2010 and arrived at Venus in December of that year, but due to a thruster misfiring it wound up not going into orbit around Venus initially. It orbited the Sun for five years, and incredibly engineers were able to insert it into Venus orbit using only its attitude control thrusters, very low thrust rockets used normally just to change the spacecraft’s angle to the planet. By doing so, they saved the mission.

And now Akatsuki is returning science to Earth. The image above is a combination of two infrared shots at wavelengths of 1.735 microns (shown as red) and 2.26 microns (shown as blue); a pseudo-green frame was crated combining the two together. The color choice is a bit odd, since usually the longer wavelength image is shown as red. But who am I to argue with such a phenomenal image?

The bright white crescent on the left is the day side of Venus, and the orange band is actually twilight; the ridiculously thick atmosphere of Venus (90 times the pressure of Earth’s atmosphere at ground level!) spreads out the sunlight, causing a wide band of scattered sunlight.*

But it’s the structure of the clouds on the night side of the planet that’s so amazing. The two different wavelengths used are sensitive to different sized cloud particles in Venus’ atmosphere and really show the atmospheric structure.

Venus is really odd: It rotates extremely slowly, taking 243 days to spin just once! The atmosphere, however, moves much more rapidly. At least, in the troposphere it does, up to a height of about 65 kilometers. It super-rotates, going around the planet faster than the planet spins. This effect is strongest at the equator, and decreases toward the poles. You can see that in the image; the sideways V-shape to the clouds reveals that. 

In fact, I mentioned that the IR image does look a little like another one of Venus I’ve seen, in this case what it looks like in the ultraviolet:

Venus in the ultraviolet
Venus in ultraviolet light.


That image was also taken by Akatsuki as it reached Venus orbit. You can also see the unusual pattern in the clouds there. Previous UV images have shown this as well.

The folks at the Japanese space agency JAXA also released this fascinating short animation showing the cloud motion:


That was taken in the infrared, four images taken four hours apart each. The motion you see is almost entirely due to the clouds super-rotating; Venus hardly spun at all during that time (the spacecraft was about 360,000 kilometers from the planet at the time, so its orbital velocity is low, and doesn’t contribute much to the motion seen either).

Akatsuki is still warming (haha) to its task at Venus. One of the most interesting things I’m waiting for is lightning data. Yes, seriously! Akatsuki has a Lightning and Airglow Camera that hopefully will settle a decades-long debate over whether Venus has lightning or not. That camera will be returning data pretty soon, so that’ll be nice to see.

Venus is such a fascinating place. Far hotter than Earth, an atmosphere that’s almost entirely carbon dioxide, tremendous surface pressure, a thick crust covered in volcanic features … it’s so close to being another Earth yet misses by a country kilometer. What happened? Why is it not Earth’s twin, but Earth’s evil twin? We’re still trying to figure that out, and Akatsuki will help tremendously.

Update, June 13, 2016: Mark McCaughrean, senior space adviser for the European Space Agency, reminded me that the ESA Venus Express probe also took amazing images of Venus. To be honest, this simply slipped my mind! I've thought about this before; we've had so many missions to so many planets now that it can be hard to remember them all. What times we live in! I've written about Venus Express many times, and because why not, here's NASA's Magellan mission, too.

*I used the auto-translate feature of Google to convert the original website’s description from Japanese, and it says the twilight band “is because that's near the day and night boundary has become Orange sexy,” which, honestly, I can’t argue with.

June 12 2016 9:15 AM

A Heavy Metal Cosmic Whodunit

Sometimes you just need a pretty picture of a star field, right?

But sometimes it’s fun to find out a little bit more, too, and I’m happy to help!

That image above is NGC 6496, a globular cluster as seen by the Hubble Space Telescope. Globulars are roughly spherical collections of hundreds of thousands of stars, bound together by their mutual gravity. I did an episode of Crash Course Astronomy about them if you want more (and you do, because they’re wonderful):

Our Milky Way galaxy has at least 150 such clusters orbiting it, and in general they can be divided into two groups: halo clusters and disk clusters. As you might expect from the names, halo globulars tend to have orbits that are way far removed from the galaxy itself, staying out in its halo. Disk clusters stick closer in to the flat plane of the galaxy.

Compared with the Sun, both kinds of globulars have stars that are deficient in heavy elements (for astronomers, that means any element heavier than hydrogen and helium, which, for historical and mainly traditional reasons nowadays, astronomers confusingly call “metals”). For example, the amount of iron in globular cluster stars never gets much more than about 1/3 as much as you see in the Sun, and can be as little as a fraction of a percent. But they are different: Halo cluster stars tend to have lower abundances of metals in them compared with disk clusters.

NGC 6496, as it happens, is seen very near the plane of our galaxy, close enough that we have to look through stars and gas and dust in our galaxy to see it. That makes it a bit harder to observe and measure its chemistry. Astronomers have argued whether it’s a halo cluster or a disk cluster for some time; even though it’s in the galactic plane it could be a halo cluster on a highly tilted orbit that we happen to see when it’s plunging through the galactic equator.

The Hubble observations here indicate the stars have more heavy elements in them than you’d expect for a halo cluster, but about the right amount for a disk cluster. While it may not be conclusive, that’s pretty good evidence for it being a disk system globular.

Why does it matter? Globulars are very old, 10 billion to 12 billion years old, about the same age as the galaxy itself, so they probably formed along with it. Being able to categorize them, assess their similarities and differences, tells us more about how the galaxy formed, and how things have changed in the ensuing eons.

It’s a detective story. The more clues you have, the more you understand the situation. The Universe is pretty good at providing us with clues, and we just have to be clever enough to put them together.

P.S. This image is made up of public Hubble observations, processed expertly and artistically by Judy Schmidt, who’s made a name for herself doing just this. Follow her on Twitter and on Flickr for more of her imagery.

June 11 2016 9:30 AM

Oh, THAT’S What Those Bright Spots on Ceres Look Like

Sweet mother of protoplanetary briny impacts! I’ve been wanting to see a high-resolution image of the crater Occator and its weird bright spots for months, but I never expected this.

Mind you, that’s not the full picture, nor is it full size here! I had to crop and shrink it; the original is7,700 pixels on a side and will melt your brain.

I recently wrote about Occator and the odd ridge-like features running down its rim. I’m not sure what they are (though I have an idea; see the link) but this is definitely the best view of them yet. Yegads. Like most craters on Ceres, the rim wall has suffered a series of landslides, and the debris has piled up all around the crater wall floor.

And the bright spots! Those were first seen when the Dawn spacecraft was still nearly 400,000 kilometers from Ceres back in January 2015, and hinted at in Hubble images before that. It took a while, but planetary scientists seem swayed that the spots are salt deposits. Ceres has a lot of water ice in it as well as a lot of rock, and under some circumstances when those two substances interact you can get salty water.

June 10 2016 9:15 AM

“This Is Discovery”

Oh, the wonder of science! It inspires people to learn more, investigate more, even if the payoff isn’t obvious. But don’t believe me: Just watch this:

I don’t think I could say it any better myself. But I have said it:

I’ve said this many times, under many different guises, but mostly under the mantle of dealing with the attacks on science, as Dr. Sheila Patek did in that video.

And this is why I speak out, and will continue to speak out. As long as people deny science, deny reality, then we must speak up. And when those people are in the government and control the funding and the choices scientists have to make, then it is absolutely critical that those who understand reality (or are trying to understand it better) continue to make their voices heard.

Tip o’ the Bunsen burner to Emily Dietle.