Bad Astronomy
The entire universe in blog form

March 24 2015 12:26 PM

Sen: Ancient Radioactive Lunar Volcano

For my fortnightly column at this go-round, I had a lot of fun writing about an ancient lunar volcano’s explosive eruption eons ago, the extent of which was mapped using gamma rays from radioactive thorium buried under billions of years of impact-produced lunar dust.

So yeah, I had a lot of fun. Sometimes just researching an article is pretty cool.

As I’ve said before, while the news and other sections at Sen are free, the blogs are subscription only. But if you look at the bloggers there, you’ll find that the price is totally worth it. You’d spend more than that on a book by just one person. And for that you’ll get to read lots of people covering lots of space. Literally.

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March 24 2015 7:30 AM

Flying High During a Solar Eclipse

I should know better by now: Whenever I post a bunch of pictures from some astronomical event and say they were the best I saw, someone comes along and proves me wrong.

This photo was taken by frequent BA Blog contributor Geoff Sims, who was flying on a plane chartered to observe the March 20 solar eclipse (the flight was planned by my old friend and dedicated umbraphilic astronomer Glenn Schneider). They were over the north Atlantic at 35,000 feet when he took that shot of the eclipsed Sun, the moon’s shadow darkening the Earth below.

March 23 2015 12:00 PM

Bad Astronomy Video: The Pink and Purple Crab

Take equal parts 1) supernova, 2) Hubble Space Telescope, and 3) Herschel infrared observatory. Mix well. What do you get? Purple (and pink) majesty.

This video is based on an article I wrote about this observation. And yeah, you want to go take a look; the high-res picture is pretty phenomenal.

I love this image of the Crab Nebula, if only because the colors are almost electric. But also because this has been an intensely scrutinized object; people have dedicated their careers to it, and lots of astronomers have done at least some work on it. I have too; I did a bit of coding for a Hubble observation years ago, and developed/updated a classroom education exercise based on the observable expansion of the gas. And, of course, I’ve observed it a zillion times with binoculars and telescopes.

But when you get new tech, like Herschel, you learn new things. Even familiar faces have something to teach us when we see them in a new way.

If there is a life lesson in there somewhere, feel free to find it. 

March 23 2015 7:15 AM

Pluto Naming Rights

In a few months, Pluto’s gonna get a lot less fuzzy.

Right now, the distant world is a scant three pixels across in the camera of the New Horizons space probe. But it’s fast approaching; New Horizons recently crossed the distance where it was closer to Pluto than the Earth is to the Sun. Given that Pluto is 40 times farther from the Sun than the Earth is, you can see that the probe is nearing the goal of its mission.

Closest approach will be in mid-July 2015. A bit more than a month before then Pluto will be more than a dozen pixels wide in images. Still not much, but enough to start seeing major features, coloration or brightness differences from spot to spot on the surface. Closing in at 14 kilometers every second, Pluto will grow rapidly, and details will clear.

The transformation of Pluto from a fuzzy blob to a sharp and clear world will be so rapid, in fact, that there won’t be time to name all the new surface features seen. Thinking ahead, the scientists involved have decided to create a list of potential names for features not yet seen. That’s pretty clever, but what names should go on that Plutonic list?

That, it turns out, is up to you. Seriously. The New Horizons team, in coordination with the International Astronomical Union (the official keeper of cosmic names), has a website called Our Pluto where you can suggest names and vote for the ones you like.

The names fall under several themes, including explorers (real and fictional), the underworld (Pluto was, after all, the god of the underworld, and the moons are named after various related characters), scientists, engineers, starships and spaceships, and more. They make a special note: “We particularly welcome suggestions that come from the ancient past and from the world’s many diverse cultures.”

This is an interesting idea. It’s not a free-for-all, so that should prevent the usual irritating responses expected from the underbelly of the Internet, and in the end the names from the public are suggestions, not mandatory. But with the IAU involved, the ones chosen will eventually become official.

So here’s your chance to help name a feature on another world! Voting ends on April 7, so hurry. Orbital mechanics wait for no human.

March 22 2015 7:30 AM

Where Are the Pictures of Ceres?

I’ve been getting some emails and tweets asking why, if the Dawn spacecraft entered orbit around Ceres on March 6, haven’t we seen any new close-up pictures for nearly three weeks?

The answer is not that NASA is covering up alien bases or Obama’s birth certificate or any other such nonsense. It’s actually due to gravity and chemistry.

Dawn doesn’t use conventional chemical rocket thrusters. While these can provide a lot of oomph, the fuel is heavy, which means you need to carry more fuel to carry that fuel, and so on. You can change directions quickly, but the cost is dedicating more of your precious payload mass to fuel instead of scientific equipment.

Instead, Dawn uses ion thrusters, which use complex electric fields to fling ionized atoms out the back end at high speed. The thrust is a lot lower, but you use fuel so efficiently you can literally keep your engines on for months at a time. In the end, you get the same ability to change the direction and speed of your spacecraft; it’s just a lot more gentle and takes a lot longer.

The orbital insertion path for Dawn is not an easy one. The new trajectory is in green, and the tick marks are Dawn's positions one day apart. Note the long, looping path designed to save fuel over the old trajectory (red). Right now, Dawn is at the apex of the long loop.

Diagram by NASA/JPL

So instead of blasting toward Ceres and blasting into orbit, it’s more like Dawn is sliding into orbit, catching up with the asteroid slowly and easing its way closer. To do that it flew past Ceres a bit, and is now on the side of Ceres away from the Sun. From its vantage point it’s looking down on the dark side of the asteroid. It’s also on a trajectory that took it farther away from Ceres, and is now falling down closer to it (like tossing a rock in the air, and having it fall back down into your hand).

In fact, a problem with Dawn’s reaction wheels (which are used to turn the spacecraft) caused engineers to put it on an orbital insertion path that’s even more fuel-efficient, to make sure they have extra fuel on hand if they need to compensate for the loss of the wheels. The diagram above shows this, and here's a nifty animation of the insertion as well:

So, though it’s been under the influence of the gravity of Ceres for a few weeks now, it’s not in a low orbit just yet. It will be soon though, and we’ll start getting lovely high-resolution images. I can’t wait. I’m dying to know just what those bright spots are; speculation is rampant among scientists, but really we won’t get definitive answers until Dawn gets close and can watch Ceres over time.

When will that finally start? April, so in just a couple of weeks. Patience, young Padawans. A new Ceres is coming.

Tip o' the electrostatic grid to Rachel WW for the link to the orbit video.

March 21 2015 7:30 AM

Snowy Hawaii

Now here’s something you don’t see every day: snow in Hawaii!

To be fair, that’s the Mauna Kea volcano on the Big Island, and it tops out at 4,200 meters (13,800 feet). It’s commonly cold up there, of course, but snow is unusual.

The picture is part of a much larger shot taken by the Landsat 8 satellite. By coincidence, my friend and astronomer Mike Brown was at the observatory at the summit and took a lovely photo of it from a more terrestrial viewpoint.

It’s funny to think of Hawaii as getting cold, but when your island goes from sea level to more than a third of the way out of the atmosphere (as measured by pressure, at least), you get a bit of diversity in the weather.

March 20 2015 12:18 PM

Solar Eclipse Pictures and Video to Make Your Brain Happy

On March 20, 2015, the Moon passed in front of the Sun ... if you were on the right spot on the planet. Or, better, above it!

Let's start off with a special treat: From the ground, master astrophotographer Thierry Legault took video of the International Space Station crossing the Sun during the eclipse!

Incredible. Legault is really, really good at this sort of thing and traveled to Spain to catch the fraction-of-a-second event. 

Most of the U.S. would've been asleep during the eclipse overnight, which graced the skies of Europe, northern Africa, and Asia ...where for the most part it was only partial; it was total in the waters north of Europe and Asia. 

However, some places did see a total eclipse, like in Longyearbyen, a town in Svalbard, an island a few hundred kilometers north of mainland Norway. My pal Tunç Tezel was there and got this great shot:

The European Space Agency has a lot of images and video on its site, including this one taken by its Proba-2 satellite using a camera sensitive to the far ultraviolet:

Proba-2 view of the eclipse from space.

Photo by ESA/ROB

There's a video of the eclipse from Proba-2 as well that's pretty nifty.

Astronaut Samantha Cristoforetti took an amazing picture of the Moon's shadow on the Earth, with a Russian capsule hanging off the ISS in the foreground:

It must be nice to know you're guaranteed a view even if there are clouds.

Photo by ESA/NASA

And one more: NASA's Terra Earth-observing satellite took this dramatic shot of the Moon's inner (umbra) and outer (penumbra) shadow over clouds in the Arctic Ocean:

The colors are amazing in this picture from space.

Photo by NASA Goddard MODIS Rapid Response Team

Those lines are called cloud streets and are pretty cool all by themselves.

And finally, if you want to understand eclipses, why, I did a Crash Course episode on them:

If you missed this eclipse, don't sweat it: There are a lot more coming, including the August 2017 that will sweep across the U.S.! I'll have more information about that closer to the event, of course.

Update, March 20, 2015, at 16:30 UTC: I originally wrote that this eclipse happened "yesterday," because it was during the middle of the night for those of us in the U.S. A few people got confused by that, so I changed it to simply the date of the eclipse: March 20, 2015. Sorry about that!

March 20 2015 7:30 AM

Crash Course Astronomy Episode 10: The Sun

Doubt thou the stars are fire, doubt that the sun doth move. Doubt truth to be a liar, but never doubt I love. —Hamlet, in a letter to Ophelia

Of all the stars in the Universe, the one we know best is our own Sun.

That’s not to say we understand it completely, of course. But we know it’s not a burning ember, or a god, or a great ball of fire (goodness gracious). It’s a fantastically huge fusion-generating plasma ball, the main source of light, heat, and gravity in the solar system.

Wanna know more? Of course you do. Let this guy in an orange shirt tell you more.

Researching this one was fun. I know a bit about our star, having written about it a bajillion times on the blog and in my books. The hard part, as usual, was struggling with what to leave out. I decided the chromosphere could be sacrificed, and details about the complex way the magnetic field is generated.

That wasn’t so bad, but the killer was the sunspot cycle. It’s a big topic, and too hard to synopsize for the video in the time allotted. In the end I figured I covered the spots, the solar storms, and the effects on Earth, so the fact that Sun waxes and wanes in magnetic activity would just take too long to go over. You can read more about it here if you’d like.

But, the hope is that you get a taste of the Sun—figuratively, because otherwise ow—and want to find out more. The thing about astronomy, about science itself, is that there’s always more to learn.

March 19 2015 1:54 PM

Ted Cruz Goes Full Orwell

In case you haven’t heard, Sen. Ted Cruz (R-Texas) is not a fan of reality.

Earlier this week, Cruz went on Late Night With Seth Meyers, and they discussed the issue. What Cruz said, in its entirety, is what comes out of the south end of a north-facing bull. Watch:

Here’s the transcript:

I just came back from New Hampshire where there’s snow and ice everywhere. And my view actually is simple: Debates on this should follow science, and should follow data.  And many of the alarmists on global warming, they got a problem cuz the science just doesn’t back them up. And in particular, satellite data demonstrates that the last 17 years there’s been zero warming. None whatsoever. It’s why—you remember how it used to be called global warming and then magically the theory changed to climate change? The reason is it wasn’t warming, but the computer models still say it is, except the satellites show it’s not.

There’s so much wrong in what he said that it’s almost cartoonish. It’s a tour de force of wrongness.

Let’s go point by point.

First: It’s cold in New Hampshire! Yes, because global warming doesn’t mean the Earth is always hot. It still gets cold because we have seasons; the Earth’s axis is still tilted. This is a standard denier talking point meant to distract from the real issue. Cruz starting off with this line is a sure-fire way of knowing that he’s got his head firmly planted in the sand. As Stephen Colbert wrote, brilliantly mocking this kind of ridiculosity, "Global warming isn't real because I was cold today! Also great news: World hunger is over because I just ate."

Next, Cruz is right in one sense; we should follow the science. But the real science, not the nonsense he’s saying. Real science doesn’t cherry-pick one result that appears (incorrectly) to back up an outrageous claim, but ignore the overwhelming amount of evidence that this claim is dead wrong.

He says satellite data shows no warming. That is wrong, wrong, wrong. Even giving him the benefit of the doubt, his saying this shows at best a gross misunderstanding of the data. And there is a vast amount of data from other sources showing the Earth is warming up. As the National Oceanic and Atmospheric Administration reported in February 2015, “[n]ine of the past 12 months have been either warmest or second warmest on record for their respective months.” And 2014 was one of if not the hottest year on record.

getting hot
Top: The global temperature trend over time, from 1950–2014, in degrees Celsius per decade. Red means it's getting hotter. Notice anything? Bottom: An "anomaly plot"; the annual global temperature trend over time where the average from 1951–1980 is set to 0. This shows what the actual temperature increase in degrees Celsius is.

Both diagrams from NASA/GSFC/Earth Observatory, NASA/GISS

But of all the bizarre nonsense Cruz said in that interview, what really got my teeth grinding was his comment about how it used to be called “global warming” but now we call it “climate change” because the evidence doesn’t support warming. That is at the level of weapons-grade irony. The idea to start calling it “climate change” came from a Republican strategist, in an effort to make it seem less threatening.

By saying that, Cruz has gone full Orwell: His own party made that change in phrase, but he’s accusing scientists of doing it.

Ted Cruz is a flat-out science denier. He’s unworthy of a leadership position, especially one that deals with science. Yet he’s chairman of the Senate subcommittee overseeing NASA, and he wants to run for president.

If there’s anything that can counteract global warming, it’s the chill in the air I feel from having to write that last paragraph.

Correction, March 23, 2015, at 16:20 UTC: I originally misstated that the bottom plot in the picture had the average from 1950–2014 set to 0. The average is from 1951–1980.

March 19 2015 12:00 PM

You Are Gopher Launch

After this morning’s post, we all need a Unicorn Chaser.

I don’t usually post cute animal videos, but this one is pretty dang cute and is at least marginally apropos of the blog: At the Russian Baikonur Cosmodrome rocket launch site, a prairie dog made its home in the ground. Not just anywhere, though: Right in the middle of the rail tracks over which a monster transporter moves.

Someone put a pretty nice webcam on the side of the hole, facing the launch site, where a Proton rocket waits for launch!

(I suggest setting the playback to 2x the normal rate.)

I love how the rodent watches the people moving … until its observations are so rudely interrupted. Also, if you’re going to install a camera in an animal’s hidey hole, make sure it’s secured well!

By the way, a lot of sites are calling the animal a gopher, but it looks more like a prairie dog to me. If there are any varmint experts reading, I’m listening.

Tip o' the nose cone to Jason Davis via Emily Lakdawalla.