Bad Astronomy
The entire universe in blog form

Dec. 27 2016 8:45 AM

Vera Rubin, Discoverer of Dark Matter, Has Died

Vera Rubin, a pioneering astronomer who discovered dark matter, has died. She was 88.

Her work in astronomy ushered in a revolution in how we saw the Universe. Dark matter is invisible, but it has mass, and affects the cosmos on a large scale. Rubin’s work was studying galaxy rotation curves, literally how spiral galaxies spin. When she plotted her data, she found that the graphs of rotation speed versus distance from the center could not be explained using the standard model for galactic structure. She realized that what her data showed is that there must be far more mass in the outskirts in galaxies than we can see. We now know this to be correct: Almost all galaxies are embedded in a vast cloud of invisible material we call dark matter. And these halos are truly massive; dark matter outmasses normal matter by a factor of more than 5 to 1.

Later work showed that entire clusters of galaxies had dark matter halos, and that this stuff actually helped the largest scale structures in the Universe form when the cosmos was very young. Without it, the Universe would look very, very different.

Do you see how important this is? Most of the Universe, Rubin discovered, is invisible to us, yet this material has had a profound effect on literally everything.

I didn’t know her personally, but everyone I know who did spoke highly of her. She was a mentor and role model to many, including many women. She was an advocate for women in astronomy, working for years for example to get more women into the National Academy of Sciences. Lots of people are sharing lovely stories online about meeting her and the effect she had on their lives, including Carolyn Collins Petersen and Dr. Chanda Prescod-Weinstein.

One more thing that must be said. As a woman, Rubin faced in uphill battle in much of her career. She deserved a Nobel Prize for her work but was overlooked year after year. I’ve written about this before; her work predates the discovery of dark energy by decades, yet the two teams of astronomers who made that discovery were awarded the Nobel in 2011. I do think the 2011 award was deserved, but why did the Nobel Committee skip over Rubin for so long? The last woman to win the prize for physics was Maria Goeppert-Mayer (for her work on atomic nuclear structure), and that was in 1963. The most recent woman before that was Marie Curie, in 1903. And that’s it. Just two women.

But the Nobel committee, by its own rules, does not give the award posthumously. So that’s that.

Except it isn’t. Her work lives on, and as she herself said when being admitted to the National Academy of Sciences:

Fame is fleeting. My numbers mean more to me than my name. If astronomers are still using my data years from now, that’s my greatest compliment.

How many women were inspired by her, how many structures in astronomical societies exist because of her? Even if the general public might not know her name, her positive influence will extend well beyond her own lifespan.

Dec. 26 2016 12:00 PM

Video Preview of Cassini’s Saturn Endgame

Not long ago I wrote that the mission of the fantastic space probe Cassini is coming to an end. On Sept. 15, 2017, after a series of quite daring maneuvers, Cassini will drop into the atmosphere of Saturn, returning a last few bits of data about the giant planet’s atmosphere even as it plunges to its death.

The wonderful podcast NASA 360 just released a pretty nifty short video showing this, with graphics that explain the end-of-mission so that you can picture for yourself how this will go:

This is bittersweet, to be sure. Of all the robotic probes humanity has sent into space, Cassini is one of my favorites. It’s been orbiting Saturn for more than 12 years; I remember watching the live feed of the orbital insertion burn with my daughter, then in grade school, while she asked me questions about it.

My daughter is now in college. That puts the longevity of Cassini into perspective.

But all good things … It costs money to maintain a spacecraft mission, and NASA has a limited amount of it. The longer the mission runs, the higher the chance something will go wrong, or it will run out of propellant—and Cassini’s tank runs low. NASA wants to make sure the probe cannot hit any of the moons; while it’s unlikely in the extreme, we don’t want our germs contaminating any places where there might be life. And this way we get extra data about Saturn’s atmosphere, too.

I always hate to see a mission end, but there is something noble and hopeful that our robotic proxy will send us information back even with its last breath. May all such missions do so well.

Dec. 26 2016 8:45 AM

By the Light of the Silvery Lunar Fogbow

Göran Strand is an amazing astrophotographer whose work I’ve highlighted here many times. He has an astonishing skill in making beautiful photographs out of rare and bizarre phenomena.

And here he is once again: That photo above shows that’s quite uncommon sigh: a fogbow! But this being Strand, even that’s not unusual enough. For him, it had to be even more difficult to track down. That’s not just a fogbow, it’s a lunar fogbow!

Fogbows are similar to rainbows, in that they’re caused by water droplets, but in detail they’re very different. In a rainbow, sunlight is bent and reflected inside a raindrop, and sent off at an angle. The drops are big compared to the wavelength of light, so they act a bit like mirrors. Each color of sunlight, though, bends at a slightly different angle, separating them, creating the multihued rainbow.

Fog is made of much tinier droplets, far smaller than a millimeter in size. At those sizes, the physics is different. Instead of following clean paths, the different colors of light get smeared out inside the droplets due to a process called diffraction — this is what happens when a wave encounters an obstacle; it spreads out. When the colors emerge from inside the teeny fog droplets they overlap so much that they form white light.

Fogbows are generally pretty faint, and usually seen only dimly during the day. The Moon is far dimmer than the Sun, but —and stop me if this is too much— it gets darker at night, so the Moon is enough to create a visible fogbow. Even then, it helps when the Moon is full or nearly so, to maximize its brightness.

lunar fogbow
The original shot shows the fogbow, stars, the aurora, and glow from a nearby town (I cropped the shot at the top of the article to emphasize the fogbow).

Göran Strand

Strand took the fogbow picture on the island of Frösön in central Sweden on Dec. 17, 2016, when the Moon was about 85 percent full. He actually went out to photograph the aurora, which didn’t perform well that night. He was about to go home when he decided to go to another site to see if he could get a better shot. To his delight, he saw the lunar fogbow while walking along the beach. Good thing he did; a few minutes later the wind dispersed it!

He’d been hoping for years to see and photograph one, and now his wait is over. I’m really glad it is! It’s a spectacular photo. You can even see supernumerary arcs (caused by wave interference inside the drops) and the green aurora, weak as it was (the yellow glow is from a nearby town).

I had to do a little reading to understand what causes these milky bows, and now that I understand them better I too want to see one! Fog is rare in my part of Colorado, and I’d need a clear night with a mostly full Moon as well, so there’s a lot of moving parts to connect. Still, I know how to maximize my odds: Be aware of my environment, and keep looking up! There is beauty waiting around those who endeavor to see it.

Dec. 25 2016 8:45 AM

The Photons Came Down the Chimney With Care

This day of the year is a funny one; people who write for a living try mightily to tie their particular field to the holidays. For an astronomy and scifi nerd, it’s relatively easy, whether it’s a Star Wars tree topper or an asteroid named Santa. Finding a little Christmas connection isn’t so much a chore.

I was going through my emails to look over topics I could write about (and reply to a few queries I’d let sit for far too long) when I found the above image of the galaxy NGC 918, taken by my friend Adam Block using the 0.81-meter Schulman Telescope at the Mt. Lemmon SkyCenter in Arizona. In the email he sent me he titled it “Galaxy in the Mist”, which is poetic and accurate enough.

But I had something else in mind when I saw it…

Dec. 24 2016 8:45 AM

Venus Commands the Sky Over Frozen Waves

Apropos of nothing, last night I took this picture just after sunset. The sky was still bright enough to illuminate the lake at a low angle, accentuating the ripples and color variations of the thin ice covering the liquid below… but also dark enough that brilliant Venus was easily visible, dominating the sky to the south.

Yesterday was an irritating day for a number of reasons; everything I was doing seemed to get bollixed and impeded by trivialities. It was nothing major, but enough to be frustrating and put me in a dim mood. But then I saw this. It certainly didn’t fix any of the issues of the day, but it just as certainly put them in their place.

Dec. 23 2016 8:45 AM

The Expanse Expanded

Editor's Note: The author of this post has been financially compensated for promoting this show. This post is not related to that compensation, but the author's financial relationship to the show still presents a conflict of interest that violates Slate's ethical standards. We do not allow our writers to be paid to promote products that they will later cover. Slate regrets the error. We have updated the original headline of the post, but the rest of it stands below.

*Full disclosure: I want to be fully up front with y’all here: The senior vice president of communications at USA and Syfy is a friend of mine (from long before she was with the network). I also know the authors of The Expanse book series (I was on a panel at Phoenix Comicon with Ty Franck, and moderated a panel with him and showrunner Naren Shankar at Gallifrey 1). Finally, I was part of a paid promotional campaign for The Expanse on social media (see here and here). That campaign absolutely does not extend to this blog, where I am free (and quite apt) to praise or condemn whatever I want. Having said that, I only agreed to promote the show because holy cow, it really is that great.

Regular readers know how big a scifi nerd I am. Star Trek, Doctor Who, 12 Monkeys… I love science fiction that tells big, grand stories.

Right now, one of the best scifi shows on TV —heck, one of the best shows on TV— is The Expanse on Syfy*. Set about 200 years in the future, it’s about the people and fragile politics between Earth, Mars, and the people who live in the asteroid belt. Belters mine the asteroids for water for Earth and Mars, but live much like slaves. Mars and Earth have no love for each other, and things are … tense.

Throw into the mix a mysterious and incredibly advanced bioweapon, and things get difficult indeed.

The first season is simply stunning. The writing, acting, special effects and more all come together to make a superior show. I wrote about the first season last year, and now with the second season coming, Syfy put together a short intro to the show that goes behind the scenes to reveal how it’s all done, and to familiarize you with the concept. It’s hosted by My Close Personal Friend Adam Savage™, and you might recognize another face in it as well.

I love this show, so I was excited when they asked me to be in the documentary. What I said is true: The way they stick to real science as much as they can in the show is amazing, accurately depicting how things would work in space. There are some shortcuts taken, like sounds in space because it adds drama, but the physics of gunfire, spaceship travel, and more are depicted with faithful accuracy. It makes my nerd heart sing.

And if that’s not enough, Adam also did a 360° virtual tour of the set of the Rocinante, and interviewed Daniel Abraham and Ty Franck, the authors of the book series on which the show is based. I highly recommend the books, too. They’re a great read.

I am really fired up for the second season. It premiers Feb. 1st, 2017. Watch it, and help keep really solid TV alive.

Dec. 22 2016 8:45 AM

Antimatter Is Starting to Yield Its Secrets

Is antimatter just like matter, but, well, opposite?

This question has bedeviled physicists for decades. Antimatter is very similar to matter —it’s made up of subatomic particles juts like matter is, but they have an opposite electric charge. So an antimatter electron has a positive charge and is called a positron (a “normal” matter* electron has a negative charge). An antimatter proton has a negative charge, and though I really wish they were called negatrons instead they’re just called antiprotons. Which is still cool.

Other than that, antimatter should behave just like normal matter. You can take an antielectron and an antiproton, put them together, and they’ll form an antihydrogen atom, the antimatter version of a normal hydrogen atom.

But does it behave like a normal matter of hydrogen? We know a lot about how hydrogen goes about its business, to extremely high precision. But antihydrogen is tougher to figure out for two reasons: Making it is hard, and studying it is harder.

Antimatter has an irritating quality: If it touches its normal matter counter part, they annihilate, turning into pure energy. A lot of it. That is, after all, why the Federation uses it as a power source for their starships. Duh.

Anyway, it takes extremely high energies to make antimatter, the kind of energies you get in a particle accelerator, and we see positrons from them all the time (they occur in small quantities naturally, too, when some radioactive elements decay, and in fact are even used for medical imaging in PET scans; the P stands for positron).

High energies means high speeds, so you get these antiparticles whizzing around, and you have to slow (cool) them. But when you do that, then what? If you try to put them in a jar or a vault or a net, they react with the matter, and kaboom!

To overcome this, scientists use magnets. Charged particles are affected by magnetic fields, so if you’re clever —and we humans are— you can create a magnetic bottle to trap the particles. This has actually been done for years.

The tricky part is catching lots of them. Then the next tricky part is catching both antiprotons and positrons. Then the next tricky part after that is merging the two so they can naturally form antihydrogen. Then the subsequent next tricky part after that is to keep that antiatom trapped.

That last part is pretty hard; once a positron hooks up with an antiproton, they form a neutral antihydrogen atom, which is no longer affected by the magnetic bottle. It then falls away, hits the side of your metal container in your lab, and produces a teeny weeny flash of light.

Now comes the next clever bit. An antihydrogen (or even normal hydrogen) atom looks neutral when you’re far from it, but up close it’s still made of a pair of particles, one positively and the other negatively charged. This means it’ll react very weakly to much more sophisticated magnetic fields (an octopole field, for those taking notes at home), which can then be used to trap the antihydrogen before it goes poof.

Still with me? Because now comes the very, very cool part: Once you have an antihydrogen atom trapped, you can start poking at it with science and see what makes it tick.

And now (finally!) we come to why I’m writing this article: Scientists at CERN have, for the very first time, been able to take an optical spectrum of an antihydrogen atom. That’s pretty big news! It shows that to the accuracy of their measurements, antihydrogen obeys the same laws of physics as good ol’ normal hydrogen.

In a normal hydrogen atom, the electron whizzes around the proton in the nucleus in a very specific way (if you want a more detailed explanation, my episode about light for Crash Course Astronomy will cure what ails ya). If you give the electron a little more energy, it jumps to a new level, whizzing around in a very specific but different way. It takes a very precise amount of energy to do that, which we call a quantum, and is where the whole “quantum mechanics” thing comes from.

Anyway, it’s like walking up a flight of steps; you can climb up one step at a time, or two, or three, but not one-and-a-half; if you don’t have enough energy to get up to the higher step, you stay where you are.

For electrons, that energy can be given to it in the form of light. What we call “color” is really the energy of the light; red is lower energy and blue higher. So if you can tune a laser’s color to be the exact right energy, you can use it to zap an atom and ping the electron to the next level, then see if you had any effect on it.

This is precisely what the scientists did. But there’s one final problem: How do you measure what it is you did? How do you know that you had an effect on the antihydrogen when you zap it with the laser?

The actual physics involved is quite complicated, but in the end, one thing that can happen is the laser can excite the positron enough to make it leave the antihydrogen atom. If that happens, then the positron and the antiproton from the atom fall their separate way, react with the normal matter in the chamber, and give off little flashes of light. Those flashes can be carefully measured to make sure they actually did come from the positron and antiproton, confirming the laser zapping worked.

This procedure only works if the laser is tuned to precisely the right energy. What the scientists found (by running the experiment with different laser energies) is that this only works if you use the same exact laser energy as you would on normal matter hydrogen atoms. In other words, antihydrogen and hydrogen obey the same laws of physics!

Well, within experimental error that is, which is a few parts in ten billion. We can do far better with normal hydrogen, which is easier to study; we know the energy we need to a few parts in a thousand trillion. Still, this new result is exciting, and is one of the first steps to understanding antimatter far better. Here’s a short video with Jeffrey Hangst, the spokesperson for the ALPHA collaboration that did the experiments:

We still don’t know everything about antimatter. We have very complex physical models built up over the past century or so on how it should all work, but we really want experimental results to make sure the theories are right. The good news here is that, so far, they are.

But there are still questions. One funny one I like in particular: Does antimatter fall up or down? If you had a tennis ball made of antimatter (warning: Do not try this at home or on any habitable planet) and dropped it, would gravity pull it up or down? Most physicists think it would fall down just like a normal tennis ball, but there are some ideas that gravity would work on it backwards. I doubt very strongly that’s the case, but now that we can actually make antihydrogen atoms we can start testing ideas like that directly.

I know it’s small scale and a little bit weird, but This. Is. So. Amazing. We are probing the fundamental forces and energies that the Universe itself is made of, testing it to see how it works, and what we can make of it.

And I mean that literally. I may have joked about warp drives earlier, but antimatter would make a dandy energy source for rockets even as we use them now, and who knows what else we’ll learn, what science fictional technologies await as we uncover more of what antimatter is telling us.

Remember: The computer (or phone or tablet or whatever) on which you are reading these very words is possible because we figured out how electrons work, how atoms work, even that they exist at all. What will we be able to do as we find out even more about the quantum Universe?

* Calling the kind of matter we see all around us and from what we’re made “normal” sounds vaguely racist to me. Or maybe fermionist. But in this case it’s OK; the vast majority of stuff we can see in the Universe is normal matter, with very little antimatter. The reason for the extreme lack of antimatter is still a mystery.

Dec. 21 2016 11:55 AM

What Happens When the Camera Faces the Other Way During a SpaceX Landing?

One year ago today, SpaceX landed the first-stage booster from a Falcon 9 rocket that boosted a payload into orbit.

Since that day, the rocket company has repeated that feat five times. Designed as a way to save money by not having to rebuild the first stage for every launch, the booster landings also make for incredibly dramatic video.

In the live broadcasts we’ve seen (and heard) the SpaceX team cheering as each milestone in the launch is reached, but they’ve only made brief appearances. What happens when the camera is turned around, so that we focus on them instead, as well as on SpaceX CEO Elon Musk, as they watch that very first landing live?

The footage was taken for the National Geographic Channel’s series Mars, a mix of fact and fiction about the first humans to reach Mars. (Full disclosure: I haven’t seen it yet.) I quite enjoyed this clip. I’ve been to the SpaceX factory a couple of times and it’s an amazing place; a little like Willy Wonka’s chocolate factory except they make rockets there.

What really struck me is how enthusiastic and dedicated the people who work there are. They are fiercely devoted to the SpaceX vision, and just as proud of what they do. The intense emotion you see from them in this clip is completely genuine and reflects how they feel watching their handiwork —literally, since much of the rocket is built by hand— blast its way into space… and as one part of it comes back down.

It’s engaging to see the mix of emotions, the worry/dread/joy/pride, Musk goes through as well. The way he is commonly depicted in the media is more of a comic book character than human, and while he is in many ways larger than life, when he watches that rocket goes up he is a little kid just like the rest of us. Though, perhaps, a wee bit more invested in the outcome.

I went through some engaging emotions myself watching that. It really brings home that this is a human endeavor, this exploration of space. And don’t forget that this exact same personal sort of scene goes on in at Blue Origin, at ULA, at Orbital ATK, at the ESA, in China, India, and everywhere humans build rockets to ply the sky.

I need not defend here our desire and our need to wander out into the universe; I’ve done so elsewhere. But I want to just remind you of what happens when we do. We become the best of who we are.

Tip of the nose cone to my dear friend Katherine Nelson, who’s watched a launch or two herself.

Dec. 21 2016 8:45 AM

Happy December Solstice!

Today, at 10:44 UTC (05:44 Eastern U.S. time), the Earth’s northern axis was pointed as far away from the Sun as it could be, or, if you prefer, the Earth’s southern axis was tipped toward the Sun as much as it could be*. We call that point the December solstice.

The Earth spins on its axis once per day, and orbits the Sun once per year. Over that time, the axis stays pretty much fixed — if you extend the northern axis into the sky, it points very close to the star Polaris (hence its name) all year ‘round.

But the Earth’s rotation axis is tipped a bit with respect to its orbital plane:

Earth orbit
Round and round it goes... of whose true-fix'd and resting quality there is no fellow in the firmament. Kinda.

Tfr000/Wikipedia, Creative Commons License

See? When the Earth is over to the right in the animation, the northern axis is pointed more or less in the Sun’s direction, and when it’s on the left it’s pointed away. In northern summer, near the summer solstice, the North Pole gets 24 hours a day of sunlight, and the South Pole gets 24 hours of darkness.

You can see this for yourself. Literally! Himawari 8 is a Japanese weather satellite that takes images of the Earth every 10 minutes. It’s in a geostationary orbit, which means it goes around the Earth once per day, so from its point of view it “hovers” over the same spot of the Earth. This animation shows the Earth as seen from Himawari 8 just yesterday (Dec. 20, 2016); watch carefully:

The satellite orbits at the same speed the Earth spins, so it always sees the same part of our planet; note Australia below center. Over the course of a day the Earth’s shadow sweeps over the surface, creating nighttime. Watch the video again, and pay attention to the North Pole, at the top of the frame: It always stays dark! If you’re at the North Pole, you’re in 24 hours of darkness; the Sun never rises.

Now look at the South Pole, at Antarctica. There, the shadow never quite reaches the bottom, and you can always see a bit of the austral continent lit. The Sun never sets there at this time of year!

Things are reversed at the June solstice, and you can see that for yourself as well in an amazing video that follows the Sun over the course of a day above the Arctic Circle.

So, if you live at the North Pole (ho ho ho) don’t despair: You’ve made it halfway through the long night, and you’ll get your first sunrise in just three months.

It’s funny how many different motions make up the clockwork of our planet, and how much they affect us, perhaps without us even knowing why. Unless you read my blog, of course. Then you’ll know.

And I haven’t even mentioned our orbit being an ellipse! Which reminds me: Next up: perihelion, on Jan. 4, 2017 at 14:18 UTC!

* 6.5 of one, half a baker’s dozen of the other.

Dec. 20 2016 8:45 AM

Another Day, Another Anti-Science Trump Pick For Federal Office

In case you were still wondering about the incoming Trump administration's attitude toward science —and at this point you’d have to live on Mars to not see what's going on— take a look at the person Trump has picked to run the Office of Management and Budget (OMB): Congressperson Mick Mulvaney (R-South Carolina).

As we've seen, Trump's choices for government positions have been anything from grossly unqualified to vocally antagonistic toward the agency they'll be in charge of; for his part Mulvaney says Trump will "restore fiscal sanity back in Washington," which is at best a bizarre proclamation. And of course he’s a climate change denier; that’s de rigeur for nearly every Trump pick.

But he’s more worrisome even than that. As Pema Levy at Mother Jones has written, Mulvaney questions whether government should be funding scientific research.

In a now-deleted (though cached) Facebook page, Mulvany wrote, “… do we really need government-funded research at all?”

Mulvaney zika Facebook post
The cached version of the now-deleted Facebook page; emphasis mine.


The context here was about Zika virus research; he was asking specifically why money was being spent on the virus’s effect on infant microcephaly when in Colombia there were many cases of zika infections but no cases of microcephaly (in reality, there were dozens of such cases, but far fewer than expected). In his opinion, this casts doubt on the connection between the virus and microcephaly.

There are two reasons why Mulvaney’s claim here is deeply, deeply troubling.

One is that there is wide scientific consensus that zika and microcephaly are linked, and had been for some time before Mulvaney wrote that Facebook page. Either he or his staff hadn’t done even the minimum amount of research needed to understand the situation (which can be easily found by simply googling the CDC site) or had done just enough to confirm his own bias before he jumped to denying the science.

But then he undermined his own point by bringing up a seeming problem with the research, contradicting himself on a much more fundamental level: When science comes up with a finding that’s not understood, why would you pull the funding at that point?

That’s the exact worst time to cut funding, because that’s precisely the time when we need even more research, more people investigating the problem! An unusual finding, or one that seems to go against the other results, means you’ve found something interesting, something important. If you find a spot on the planet where a disease doesn’t have the same terrible outcome as it does everywhere else, don’t you think we should find out why?

In Mulvaney’s opinion, it would’ve been better to simply bury our heads in the sand and ignore the problem — worse, to make sure we couldn't even study it. That's horrible.

Given the context of his Facebook post, I’m hesitant to extrapolate his claim about not funding zika research to not funding any scientific research, but the way he phrased it is disturbing. If he can deny the need for such obvious and critical research into a dangerous virus, then what else will he turn away from?

And, as head of OMB, he will have Trump’s ear, and influence over the Federal budget and government agencies. This concerns me greatly, as it does the Union of Concerned Scientists, which felt strongly enough to issue a statement condemning Mulvaney's stance on science.

I keep looking for some ray of hope, some move by the incoming administration that’s even just a nod toward reality. When it comes to science, it’s become crystal clear the opposite is true: Trump and his cohorts will do what they can to reverse many of the advances we’ve made, and they’ll use their gross (and/or willfull) misunderstanding of the foundational principles of science to do so.