Crash Course Astronomy: Stars
You’re the only star in heaven,
You’re the only star that shines,
You’re the only star in heaven,
Now that only star is mine.
Frankie Goes to Hollywood, “The Only Star in Heaven”
Stars are the building blocks of the visible Universe. They’re the fundamental unit, like atoms in matter. Stars make up galaxies, and galaxies make up the Universe.
They are also why we’re here, quite literally. Stars make planets, and stars make the elements that make you and me. We owe our existence to stars.
So understanding them is kinda critical to understanding, well, everything. Wanna know more? Then do I have a Crash Course Astronomy episode for you!
Mea culpa: In the “Focus On” segment, I say that the Sun’s spectrum peaks in the green. To be fair, it peaks in the blue-green part, and atmospheric absorption makes the light that hits the ground peak more in the blue. But when you add it all up, the Sun emits more green than blue light, which is what I meant. I should’ve been more clear.
And don’t confuse any of this with Hank Green in space. That’s a completely different topic.
Astronomers Find a Near-Earth-Size Planet in the Habitable Zone of a Very Sunlike Star
One of the biggest goals in the search for exoplanets—alien worlds—is finding an Earth-size planet orbiting its star in the “habitable zone,” where liquid water might exist on its surface. In other words, finding another Earth.
So far, a dozen such planets have been found. All of those planets may be very much like Earth (we can’t be sure, as I’ll get to in a sec), but they orbit smaller, cooler stars than our Sun.
On Thursday, astronomers announced they have found another planet in its star's habitable zone: Kepler-452b. But this one is different: It orbits a star much more like the Sun. The star and planet are about 1,400 light-years away.
The planet was discovered using what’s called the transit method; as it orbits its star, we see that orbit edge-on. Once every orbit, the planet passes directly in front of the star and we see a tiny dip in sunlight. The size of that dip tells us the size of the planet, and the time it takes tells us the planet’s orbital period.
Kepler-452b orbits its star at a distance just 5 percent more than Earth orbits the Sun, with a year 385 days long. While the star is similar to the Sun, it’s older, and stars brighten as they age. That means Kepler-452b actually receives more heat from the star than we do from the Sun, so it’s likely warmer than we are.
Note, though, that a couple of billion years ago the star was cooler, pretty much like the Sun is now. That means that a long time ago, 452b was getting the same amount of light and heat we do. Interesting.
This doesn’t mean the planet is Earthlike, though. For one thing, it’s bigger than we are: Its diameter is 1.6 times that of Earth. We don’t know its mass, unfortunately, and without that we can’t know its density. The density is what gives us our first clue about what the planet’s made of; water has a density of 1 gram per cc, but iron is 8. Rock is 2–3.
If the planet has the same stuff in it as Earth does, it’ll be more massive; four times Earth’s mass*. In that case, its surface gravity would be 1.6 times Earth. If you weighed 100 pounds on Earth, you’d weight 160 pounds there. But only if it’s rock and metal like we are. If it’s less dense (more rock) than, the surface gravity will be lower; if it’s denser (more metallic), it’ll be even higher.
It’s not clear what that means for a planet’s atmosphere. All other things being equal, more gravity means it can hold on to more gas, so the air there could be much thicker. If so—and remembering it’s receiving more light and heat from its star than we do—it might be suffering a runaway greenhouse effect. Or, it may not have any air at all. Or or or. Without more information, we can only guess.
This is an exciting discovery, since this is the first exoplanet roughly Earth-size in the habitable zone of a star so much like our own. The last time we found one this good was Kepler-186f, which orbits a red dwarf. That planet is much closer to our size than 452b is, and may be more similar to us. It’s not clear there how orbiting a red dwarf would make it different. Would the atmosphere be different? If life existed there, how might it look?
I’m a little torn about this discovery. For decades we had no idea if other planets even existed around other stars. Now we know of thousands! And we also know of many that are the size of our Earth, meaning they aren’t too hard to make. In fact, we think there are billions of Earth-size planets in our galaxy alone! Most will be too hot or cold for life, or have other issues making them likely to be uninhabitable.
Searching for a planet with conditions as close to ours is a clear goal here. Kepler-452b is a big step in that direction.
But it’s not perfect. It’s bigger, the star is hotter, and so on. I suspect 186f might be more Earthlike, but again we can’t know for sure. So I don’t want to overhype this discovery.
We need bigger telescopes, ones capable of teasing out the planet’s light from the star’s, taking its spectrum, and analyzing that spectrum for tell-take signs of chemistry. From that we can gauge its temperature better, what it’s made of, and even if there are biological markers (like, say the presence of oxygen molecules, which are hard to keep around without biology). Until then, we just don’t know enough about these planets to say much more about them with certainty.
And I think what may be even more important is to see just how diverse Earth-size planets are! Some bigger, some smaller, some hotter, some cooler. The interesting point here is that nature is cooking planets with all sorts of different flavors here, and while looking into the heavens and seeking out one that looks like us is natural, we should also be careful to delight in the varying recipes out there.
The big question we ask is, Are we alone? The answer, I suspect, hangs on what you mean by “alone.” We are in a galaxy brimming with planets, many of which look like us, and many of which don’t. But even the ones that look different at first may be more like us than we know.
* The volume of a sphere increases with the cube of the radius. Since Kepler-452b is 1.6 times the radius of Earth, its volume is 1.6 x 1.6 x 1.6 = 4.1 times Earth's volume.
Space Walking at Comic-Con With Adam Savage
Every year, I go to San Diego Comic-Con, the annual nerd bash where something like a mole of people converge on the town to celebrate pop culture. It’s a lot of fun, and one of the joys for me is to get together with friends I don’t get a chance to see otherwise.
I’m also privileged that all of my friends there are supremely talented, smart, and interesting people. One of them is My Close Personal Friend Adam Savage™; we’ve known each other for many years (so much so that he is starting to look like me).
As you might know, Adam is something of a celebrity, and getting around at the con can be a challenge for him; the huge crowds guarantee he’ll get stopped, and once that happens it’s all over. That’s how he got the idea of “Adam Incognito,” where he wears a full head-to-toe costume that conceals his identity. He then walks the exhibit hall of the con (where tens of thousands of fans visit exhibitors, goods dealers, artists, and more), and anyone who spots him and correctly IDs him wins some sort of prize, usually a VIP pass to one of Adam’s talks at the con.
This year he walked as Judge Dredd. But he threw in a twist: The next day, he decided to do it again, but this time bringing along a very special guest. The whole thing was recorded for Entertainment Weekly and Tested.com, and it’s pretty fun. Watch!
Cmdr. Chris Hadfield is a Canadian astronaut; he worked three stints on the Space Station (commanding it the third time), covered David Bowie while up there, and is an all-around nice guy—I highly recommend his book, too.
I’d never met him, so when I got a note from Adam asking if I’d like to sit behind the scenes and watch them prep for the con walk, I said YES. On the Saturday morning of the con I headed over to Adam’s hotel, met Chris, and watched with some amusement as they suited up. I wasn’t able to walk the con with them (Adam eschews anyone going with him, since it might give away the show, though in this instance they happened to run into Andy Weir, author of The Martian—soon to be a major motion picture—and they let him tag along), but I was around when they got back to the hotel room.
The suits were amazing, as you can see in the photos here. I put together an album of pictures on Flickr for your perusal as well. I think my favorite part of all this, besides the coolers Adam built to prevent them from overheating (a lesson he learned last year in his full-blown Alien space suit, complete with face-hugger), was the fact that they made sandwiches for the trip as well. That’s right out of the Moonbus scene from 2001, where Heywood Floyd and the other travelers eat lunch on the way to seeing the Monolith. Adam even made sure the crusts were cut off, an homage to the sandwiches in that scene!
Full disclosure: I ate the last sandwich. It was better than astronaut ice cream. As is everything.
And that wasn’t the end of it: That evening Adam did a one-hour Q&A on stage in the huge Room 6 of the exhibit hall, and asked several friends to come on stage and ask him questions as special guests. I was first, then Andy Weir, then Alton Brown, and finally Chris came on. It was a huge amount of fun, as you can see:
It was an honor to be able to watch this unfold and to be a part of it. Cmdr. Hadfield really is as nice as he seems, a wonderful thing to behold. He is a true gentleman, and someone who honestly and openly wants to share his joy of the world with that world. Adam is the same way; erudite and charming, he just loves what he does, and his enthusiasm is as infectious as his smile and laugh.
Although I wouldn’t say it’s a requirement, it’s a great bonus that my friends inspire me to be a better person, to work harder, to just do more. To all of them, I say: thanks.
And special thanks to Will Smith and Norman Chan of Tested for their patience, and for taking some of the pictures in the album.
Correction, July 23, 2015: This post originally misspelled Norman Chan's last name.
More Pluto! And Two Weird Moons. Well, It’s All Weird. It’s Pluto.
On Tuesday, the folks at New Horizons released more images, this time of Pluto’s surface and two of its smaller moons, Nix and Hydra.
The Pluto image shows an area to the west of Tombaugh Regio, the heart-shaped pattern. Like the earlier release, this shows mountains surrounded by flat plains of ice. The mountains aren’t as tall as in the other area (1–1.5 kilometers high, as opposed to more than 3 kilometers), but there’s something new in this one: craters.
Unlike the first close-up showing no craters at all, here you can see circular features that look very much like old impacts filled in by ice. This lends credence to the idea that the mountains are old, and the plains younger, possibly due to something that flooded (or seeped) into the lower topography. You can really see where the older, darker material had the younger, brighter stuff fill in the lower areas.
Finding craters is very important, as that helps geologists figure out just how old the surface is; more craters means the surface has been out there for longer, exposed to space.
I can’t wait to see detailed spectra of the surface so that we can know why some places are dark and some bright. Spectra will give more information on the composition of the surface.
I have to note: Some of the craters well inside the dark region have bright floors, as if some of the material got in there as well. That’s a bit harder to explain with just flooding or seepage. I can almost see gullies leading to them … but the resolution is just barely too low to tell.
This next shot shows the moons Nix and Hydra. Displayed roughly to scale, Nix is about 42 x 36 kilometers in size, and Hydra is 55 kilometers long. The best images we saw before were very pixelated, so these are fascinating to see.
Nix is red! Or it has a big red spot. It appears to be whiter near the edges, but I can’t be sure if that’s a real border to the spot or an odd effect caused by the curve of the moon’s horizon (note that the red hue in the photo has been amplified in processing to show it better). Either way, it’s a sure sign that some chemistry has been going on there. How?
Methane is abundant in the outer solar system. On Earth it’s fragile; in the presence of oxygen it’s easily burned (one reason it makes a useful fuel), forming carbon dioxide and water. But in the absence of oxygen, like out Pluto's way, ultraviolet light from the Sun can break down the molecule, and instead of forming water and CO2 it can build up to make more complex molecules. Called tholins, these are reddish in hue, and we see that a lot past Neptune.
The question is, why isn’t everything out there red? Pluto is reddish, but the big moon Charon is not. These are all clues telling us about the history of these objects. Were some objects more abundant in methane than others, or did something happen over millions of years to rob (or overfill) methane (or tholins) from some and not others? I’m totally guessing here. It’ll be interesting to see what the experts can tease out of the data.
The Hydra image, though not in color, is equally interesting. The moon is irregular in shape, looking like it has a huge bump on one end. I wonder though: That dark spot on the upper right might just be a big depression, and the rest of the bump in shadow. Perhaps more images will give us a better idea of the shape.
Two big craters are obvious; the one at the top (with a bright spot, probably a specular reflection—a glint—of sunlight off something shiny like ice) and the dark one at the bottom. I think at the bottom, that part of the moon is flattish and edge-on to the Sun; a possible crater rim can be seen on its left, and that would explain why the floor is in complete darkness. The crater on top is angled more toward us and the Sun, allowing sunlight into it.
Again, just seeing those craters is important. The more bodies we see with them, the better we can do at estimating their ages. How old is old, how young young? A hundred million years, a billion?
As usual, the first images of an unexplored place raise more questions than yield answers. But as we get more photos from New Horizons, we’ll see more of this territory and in higher resolution, too. The fun in the mystery isn’t in knowing the answer, it’s in finding it.
We’re on that journey now.
The Half Earth Catalog
Oh, that planet of ours.
On Feb. 11, 2015, a SpaceX Falcon 9 rocket launched with the Deep Space Climate Observatory, or DSCOVR, on board. The sat was slowly eased into an orbit 1.5 million kilometers (just under a million miles) away from Earth and toward the Sun, into a gravitational soft spot called the L1 point. There, the gravity of the Earth and Sun balance (if you account for the Earth’s centrifugal force as it moves around the Sun too).
Safely ensconced at this height, DSCOVR looks earthward, taking images of our planet using 10 different color channels, allowing scientists to monitor climate change among other important gauges of Earth. Starting in September, the images will be available to the public in just a day or so after they’re acquired.
Given that the camera has a 4 megapixel detector, they should be routinely gorgeous … as the image above testifies.
SpaceX Falcon 9 Rocket Lost Due to Internal Strut Failure
On June 28, 2015, disaster hit an uncrewed SpaceX Falcon 9 rocket 2 minutes 20 seconds after launch. Video made it clear something went wrong in the second stage, and at a press conference on Monday, CEO Elon Musk announced the most probable cause: a strut failure that led to the loss of the vehicle.
As fuel is used up during launch, high-pressure helium is fed into the liquid oxygen tank to maintain the pressure in that tank. The helium is kept at 5,500 PSI inside a bottle.
During launch, a strut holding the helium bottle down snapped. Counterintuitively, during the high acceleration of launch the helium tank feels a large force upward, because the helium in the tank is highly buoyant. The larger the acceleration is, the larger the buoyant force gets, and the more force the helium tank feels upwards.
The strut that snapped was designed to hold the bottle down against this force. When it snapped, the helium tank shot upward, slamming into and rupturing the liquid oxygen tank. The super-cold oxygen then boiled, expanded rapidly, and breached the second stage walls.
In the video, you can see that what happened was not technically an explosion; there’s no fireball, but you can see the expanding vapor from the oxygen tank flying away.
These struts are certified before launch, but Musk has promised that they will do a second test individually on each strut from here on out; this will mean a slightly higher cost for each launch but not a significant one.
This strut failure is hard to test for on the ground. As Musk pointed out, boosters are tested strapped down on the ground, so they only ever feel 1 g of acceleration (due to gravity). This failure happened when the rocket was undergoing 3.2 g, which cannot be realistically tested except in launch. This is a “really odd failure mode” and “quite a puzzle,” Musk said. The root cause of the failure still isn’t known; the strut failed at well under the rated stress level (it’s rated for 10,000 pounds of force, and failed at 2,000).
They are continuing to look into the telemetry; this series of events is the preliminary conclusion of the failure, not the definitive one.
Musk also said this will delay the next uncrewed flight (probably until September), and the loss of revenue to SpaceX will likely go into the hundreds of millions of dollars. Still, this probably won’t delay crewed flight, since that pace is being set by developing the next generation Dragon V2, which will likely take longer than fixing the strut issue.
Speaking of which, the Dragon capsule (filled with supplies for the space station) on the Falcon 9 survived the initial event, and in fact they were getting telemetry from it until it dropped below the horizon, but it was certainly lost when it impacted the ocean at high speed. Every indication was that, had the software triggered the parachute deployment, Dragon would have survived its fall into the ocean. However, that software has not been used on this Dragon version; it is supposed to be first implemented on the Dragon V2. Given that the capsule could have been saved, the new software will now be used on the current generation of Dragon capsules.
Incidentally, the next generation Falcon Heavy rocket demo flight has been delayed as SpaceX concentrates on the Falcon 9 issue. The Heavy demo will now probably occur in spring 2016.
Happily, no other problems have been seen in the telemetry. They’ve had 20 successful launches in a row, which is excellent, but as Musk notes, “a passing grade for rocket launches is 100 percent ... this is an important lesson and something we will take with us in the future”.
This is a huge setback for SpaceX, but Musk asserts that the company is on it and working to fix it for future launches. I certainly hope so.
Reboot the Suit!
Every now and again I get involved in a project I’m truly, deeply excited about, and honored to be a part of. This is one of those times.
The Smithsonian’s National Air and Space Museum needs your help for a fantastic project. It needs to conserve and preserve one of the greatest icons in American History:
Neil Armstrong’s Apollo spacesuit.
This is the spacesuit he wore when he made that one small step, forever dividing history into two eras: one where humans had not yet set foot on another world, and one where we forevermore became a spacefaring species.
Monday—on the 46th anniversary of that first Moon landing—Smithsonian has announced a project to help raise the funds needed to preserve the suit, and they asked me to be a part of it. We made a video introduction to the project:
You can read more about all this at the Air and Space Museum's blog.
The Kickstarter page has details on the different avenues that will be taken to conserve the suit, and also has the long list of rewards you’ll receive at various pledge levels … including access to files that will allow you to make a 3-D printout of the suit after it’s been digitized in high resolution!
The scale of this kind of project means it doesn’t come cheap. It’ll take $500,000 to fund it. But an artifact this important, this iconic, needs to be taken care of, and if this gets funded, the experts at the Air and Space Museum will do so with professionalism, care, and love.
We are just passing through history. This:
This is history.
I was overwhelmed to be invited into the back corridors of the Udvar-Hazy Center in Chantilly, Virginia, to see the spacesuit for myself (I have bigger versions of the pictures you see here, plus a few more, in an album on Flickr). I walked past workbenches and open areas with priceless treasures—the wheels from the Spirit of St. Louis, a snuffbox given to passengers who flew on the Montgolfier brothers’ hot air balloons, and the original Enterprise model from Star Trek (!!!)—and was able to stand next to and peer into Cmdr. Armstrong’s suit.
It was, quite simply, one of the high points in my life. To be able to see it up close, to talk to its caretakers, see how they work with it and other priceless historical items … it was profoundly moving.
This suit, with its human inside it, walked on the Moon. For 2½ hours, the suit traversed the lunar surface, allowing Armstrong to breathe and survive in one of the harshest possible environments. Along with Buzz Aldrin he set up scientific instruments, took pictures, and collected precious samples of the regolith and rocks around the landing site.
I’ve met some of the Apollo astronauts, and looked at other Apollo suits in museums. But this one? It was the first. The very first.
As Americans, as human beings of Planet Earth, it is more than our responsibility to maintain that spacesuit. It’s our duty. That’s why I jumped at the chance to participate in this project, and why I’m asking for your help.
If you have ever watched the footage of Armstrong stepping on the Moon, if you ever thought in awe of the grand adventure of traveling the 400,000-kilometer gulf separating it from our planet, if you ever gazed up at the Moon in the sky and wondered what it would be like to go there, and when we’ll be heading back again, then please, throw a little bit of money at this project.
My own dream is that, in a generation or two, a little boy or girl will be taking his or her first trip to the Air and Space Museum and will see that suit. It will make her wonder about her own history, and where the future will take her. And when she goes back home, back to the colony in Mare Tranquillitatis, she’ll look back toward Earth, and past it to Mars, to the asteroids, and to the stars.
But it starts here. Please help us Reboot the Suit.
I don’t ask this for much, but I will now: Please share this post and the Kickstarter link on any and all social media, and when you do, use the hashtag #RebootThe Suit. Smithsonian’s Air and Space Museum has a broad presence on social media as well.
Venus, Jupiter, the Moon, and the Heart of the Lion
I was perusing Twitter on Saturday and someone mentioned that Venus and the Moon would be close together in the sky that night. I checked my Sky Safari software, and sure enough they’d be about 1° apart at sunset for me. Given that the Moon’s width on the sky is about 0.5°, that’s a nice, tight pairing.
I also knew that Jupiter was still nearby, slowly separating from Venus after their very close encounter a couple of weeks ago (which I only caught glimpses of through thick clouds here after sunset EVERY SINGLE DAY in Colorado, grrrr). Once the Sun set I was outside snapping away. I took about 150 photos, and one really stuck out for me:
The Two Tails of Comet Pan-STARRS
I somehow didn’t hear anything about the comet C/2014 Q1 (Pan-STARRS), which isn’t to surprising: It never got bright to Northern Hemisphere observers. The comet’s orbit kept it mostly in the Southern Hemisphere’s skies, and it only recently got brighter once it swept past the Sun in its orbit.
But if you do live south of the equator, it’s putting on a decent show. It’s still naked eye visible, and is close enough to the Moon in the sky to make for a pretty airing … as astrophotographer Yuri Beletsky proves with this astonishingly lovely shot:
What’s in Store for the Doctor in Season 9?
As you might know, I’m a pretty big Doctor Who fan (as in OHMYGODILOVETHISSHOW), and I’m really looking forward to the next season. While the most recent season had some issues (arg, “Kill the Moon”) there were several great episodes, and tons of lovely scenes. The next and ninth season premiers Sept. 19.
I was at Comic-Con last week and attended a press “round table” with the Doctor Who stars and showrunner Steven Moffat, which was both fun and interesting. I’ll get to that in a moment, but first, here’s the trailer for Season 9!
Note: Spoilers ahoy, from here on out. Nothing major, but if you haven’t yet seen Season 8 or don’t want to know anything at all about next season, I suggest leaving here and finding something else to watch.
Well, that was quite a lot! I’m not sure which part was most intriguing, though Peter Capaldi playing guitar is high on my list (he used to be in a punk band with Craig Ferguson).
The trailer was played at the huge Comic-Con Doctor Who panel in Hall H (which seats more than 6,500 people), and the big reveal of Maisie Williams (from Game of Thrones) got a huge cheer. What’s her role here? I can’t help but wonder if (AGAIN, SPOILERS) she’s his granddaughter, Susan. She was his very first companion when the show started in the 1960s and was mentioned off-handedly in an earlier episode of the new reboot. During the press event (before the panel, and before we had seen the trailer) I asked about his granddaughter, and Moffat mentioned the Doctor would like to see her again. Hmmm.
There’s obviously a creepy element to some of the episodes, as you’d expect from Moffat (who wrote “Blink,” “Empty Child,” and “The Doctor Dances,” very creepy episodes indeed). Moffat said that this season, “There are scarier monsters. They’re more ‘creatures from the id,’ from the subconscious. They play with the way the Doctor sees the world. As the season unfolds, there are stranger creatures … the Universe is very dark; inevitably that’s where the Doctor will end up.” I like the sound of that; whenever we see the Doctor himself screwed with, the episodes get more compelling. Io9 has an article looking a bit deeper into some of this.
But what about the Doctor and Clara?
According to the actors, their relationship deepens. Jenna Coleman, who plays Clara, had this to say: “Clara has lost ties with Earth, her perspective has changed, she wants to travel, have fun … these will be the glory days of Clara and the Doctor. She’ll be more reckless … she has nothing to lose, seemingly.”
Peter Capaldi added, “The Doctor is deeply, deeply bonded with Clara. He sees things and understands things that are beyond the perspective of human beings. He knows things about Clara’s future that’s informed his decision to stay with her.” She’ll also teach the Doctor more about what it means to be human, and how to interact with them.
Will Clara leave the Doctor any time soon? “Clara loves the Doctor so much I don’t know what it would take to leave,” Coleman said. “[Traveling with him] opens your eyes to the Universe.”
I try to avoid getting spoilers of any kind, so I was surprised to see Michelle Gomez there; she plays Missie, the latest incarnation of The Master. Apparently she wasn’t quite as disintegrated as we were led to believe at the end of Season 8.
Gomez and Moffat talked quite a bit about the Doctor and Missie being two sides of the same coin, being friends. “They’re not enemies at all,” Moffat said. “It’s a friendship between a vegetarian and hunter.”
“She has an attitude that the rules don’t apply to her,” Gomez said. “We both do the same thing. We both kill a lot of people. He feels bad about it. I don’t.”
Watching them on the panel, I was impressed by the clear friendship and respect they all have for each other. And it’s clear they love the show: Capaldi showed up on a day he wasn’t filming so he could watch them film one particular scene involving Clara, whomever Williams plays, Vikings, and a spaceship.
Come on. You’d show up for that too. I have to admit I’m intrigued.
So, two more months until the premier. I think the trailer is all the spoilering I need, so I’ll avoid any more news … but it did what it’s supposed to do, and got me excited for the oncoming episodes.