Archive for the ‘Astronomy’ category

John Huchra

October 12, 2010

Over the weekend I learned that observational cosmologist John Huchra passed away on Friday. I only met him once, when I was a summer intern at the Harvard-Smithsonian Astrophysical Observatory. He very graciously gave the group of summer interns an hour and a half of his time and told us about his research, and about the interplay between observation and theory in astronomy. But more than that he also shared his passion for discovery and learning about the universe. Hearing him talk got me much more excited at the prospect of becoming a scientist. Even though my scientific interests have drifted toward planets rather than cosmology, that morning spent with Dr. Huchra still sticks in my mind as one of the highlights of my first summer doing real research.

I jotted down this quote when Dr. Huchra was sharing the excitement of his research with a bunch of wide-eyed interns. It spoke to me then and I think of it every time I find myself burning the midnight oil for the sake of something I’m passionate about:

“The best sunrises are the ones you see as you’re going to bed.” -John Huchra

My condolences go out to his friends, families and colleagues who knew him much better than I did. Astronomy has lost a passionate leader. He will be missed.

The Science of Starcraft: Supernovae and Gauss Rifles

September 21, 2010

I’ve got two new posts up at The Science of Starcraft! The first tackles the difference between supernovae and novae. The words are often used interchangeably in sci-fi, but they are (usually) very different phenomena. Plus, I love telling the story of nucleosynthesis and stellar evolution, and this was a good excuse.

The second post is sort of a sequel to my previous post about railguns. This time I look at gauss rifles, another electromagnetic futuristic weapon that pops up in sci-fi pretty often, but is incorrectly depicted in Starcraft:

Herschel Finds Water around a Carbon Star

September 6, 2010

Water is pretty common in the universe, since it is made of hydrogen and oxygen. Hydrogen is left over from the big bang and oxygen is made in most stars. But you don’t typically expect to find water in the atmosphere of stars themselves! That’s what astronomers using the infrared Herschel observatory found though! Deep in the shroud of gas and dust that CW Leonis is expelling as it dies, there is water at temperatures up near 1000 K. To learn more about it, check out my article over at Universe Today!

WISE Maps the Sky

July 22, 2010

This infrared view of the Pleiades is a mosaic of a few hundred out of the millions of images taken in the WISE full-sky survey. Image credit: NASA/JPL-Caltech/UCLA

I have two new articles up at Universe Today! The first is about the WISE infrared survey of the entire sky, which involved approximately a bazillion images, including the lovely view of the Pleiades shown here. You should go check it out.

The size of planets and stars

July 7, 2010

Solar System Tour: The Sun

May 28, 2010

Everyone knows about the sun, it’s that really bright thing that rises every morning and sets every evening. Not everyone knows much about it though. For example, did you know the sun is actually a star? Ok, so maybe you knew that. But if you’re so smart, what’s it made of? The sun is almost entirely hydrogen, with a bit of helium mixed in and a tiny amount of all the rest of the elements, just to spice things up. You might think that a bunch of gas floating around in space wouldn’t hold together very well, but the sun is HUGE! It weighs 300,000 times as much as the earth! Because it is so big, gravity holds it together very nicely. In fact, gravity squeezes the center of the sun together so hard that the hydrogen atoms stick together to form helium in a process called fusion. Here’s a diagram of what happens during fusion:

It looks sort of complicated, but the important thing to know is, four hydrogen atoms get turned into one helium atom, and in the process a LOT of energy is released. All the energy being released in the center of the sun has to go somewhere, and it goes into heating up the center of the sun. The center of the sun is 15 million degrees Kelvin (that’s 27,000,000 Fahrenheit!!)!

At really high temperatures, matter is no longer a solid, liquid, or gas. It becomes a plasma, which means the electrons aren’t attached to the nucleus anymore, and both can just go flying around. Energy from the core of the sun makes its way toward the surface in two ways. The first is radiation, which means it travels as photons (light) through the dense plasma. After traveling by radiation for a while, the energy starts to travel by convection. Convection is what happend when you heat a blob of gas. Hot gas is less dense, so it starts to float upward. Once it floats to the top, the hot blob cools down and begins to sink again. This rising and sinking is called convection. Convection is what causes weather on earth, hot air rises and cooler air rushes in beneath it, making wind. On the sun, we can see convection happening right at the surface. The blobs of hot plasma are called granules. Each granule is about 1/10 the size of the earth! Check them out in this picture:

The bright parts in the center of the granules is hot gas rising, the dark edges are the cool gas sinking back down. This layer of the sun (with all the granules) that you can see is called the photosphere. It has an average temperature of about 5800 K. Most people think of the photosphere as the “surface” of the sun. Above the photosphere is a thin layer called the chromosphere. You normally can’t see this layer because the photosphere below it is much brighter, but sometimes when the moon passes in from of the sun and blocks most of the light (a solar eclipse), you can see the chromosphere glowing red. (Never look directly at the sun, even during an eclipse!!) The chromosphere is hotter than the photosphere, at around 7000K. At this temperature, hydrogen glows red, giving the chromosphere its color.

Above the chromosphere is a wispy layer that extends off into space called the corona. The corona is really hot (more than a million degrees!) but not very dense. It is made of gas and bits of atoms that are getting blown off the sun. These particles are called the solar wind. When they hit the earth’s atmosphere, they make the very highest layers of air glow, causing the northern and southern lights (also called aurora). Telescopes have shown that Jupiter and Saturn also have aurora, so the solar wind keeps going a very long way.

Spots and Loops and Flares, Oh My!

The sun isn’t just a boring ball of plasma, there’s some really amazing stuff going on up there. We said before that plasma is when the bits of atoms can move around however they want, but that’s not the whole story. When things that have a charge (like electrons and protons) start moving around, they create magnetic fields. Those magnetic fields force the plasma to follow them, and end up making some really interesting features on the surface of the sun. Sunspots are the most well known result. What happens is, a bunch of magnetic field lines cluster together and keep the blobs of gas from convection from rising up in that place. The gas that is in the sunspot gets stuck and cools off, so it looks darker. Check out this movie of sunspots forming! (Note: Unfortunately all the movies in this post are .mov format, which I can’t embed. But they are truly awesome, so I recommend clicking the links!)

The powerful magnetic fields on the sun force the plasma to follow them, and make beautiful glowing loops that extend into the corona. The loops can grow to be extremely large. When they are seen in front of the photosphere, they are called filaments, when they are seen at the edge of ths sun in front of space they are called prominences.

These loops contain a lot of energy stored in the magnetic fields. Sometimes the filaments “let go” and plasma goes flying either away from the sun, or is attracted to other magnetic fields on the sun. Check this out! A blob of gas goes flying off and hits some loops, making them shake back and forth. Sometimes, when the loops get crossed or twisted, a huge amount of energy is released in what is called a flare. During a flare, a patch of the sun heats up VERY quickly because of all the energy released. Sometimes this causes huge clouds of hot gas to go flying off the sun.

These clouds of gas are called Coronal Mass Ejections, and can be enormous! Check out the next picture, with a picture of the earth added for scale.

Carnival of Space 152

May 2, 2010

Welcome to The Martian Chronicles and the 152nd edition of the Carnival of Space! As always, we’ve got a great bunch of space-related posts from across the blogosphere, ranging from life on Mars to the age of the universe to Science Ninjas!

I’ll get things started with a pair of posts from right here at The Martian Chronicles. A couple weeks ago I went on a cool geology field trip in the El Paso/Carlsbad area along with a whole bunch of other martian and terrestrial geologists. Among other things, we learned that printed Mars panoramas make good raincoats, that graduate students are ideal for menial labor like counting hundreds of thousands of layers of rock, and that ancient reefs have a surprising amount to teach us about stratigraphy on Mars. Check out my summaries of Day 1 and Day 2 of the field trip! Day three is coming soon, with lots of pretty pictures of Carlsbad Caverns!

Speaking of rocks and Mars, Paul Scott Anderson at Planetaria has a post about another Mars meteorite that might have evidence of life! He includes a few very nice electron microscope images of the meteorite for your consideration. Personally, I’m not convinced, but I’m also not an expert on this corner of Mars science. Take a look for yourself!

Ian O’Neill at Discovery News also has been thinking about martian microbes, and whether germs from Earth might have hitched a ride on our rovers, set up camp on Mars and wiped out the locals. It would sure be disappointing if we discover life on Mars only to learn that someone at JPL forgot to wash their hands! Of course, there are also those who think we should stop bothering with all this planetary protection business and deliberately seed Mars with Earth life. What do you think?

While we’re on the topic of our potentially infectious little rovers, Stuart Atkinson has some beautiful pictures from the Opportunity rover. Oppy is slowly making her way across the Meridiani Plains, and has a tantalizing view of the distant hills that are her ultimate destination. As Stu says, “The far horizon is calling…

But this is the Carnival of Space, not the Carnival of Rocks and Bugs and Rovers, so let’s get on to the more “spacey” stuff! I’m a big fan of stuff, and so is Steve Nerlich at Cheap Astronomy! This week they have a great podcast about “stuff” in space and the surprisingly limited number of shapes in which it can be found.

A radar "image" of an asteroid and its two tiny moons. Credit: NASA / JPL / GSSR / Emily Lakdawalla

While we’re on the topic of stuff and its various shapes, I should point out that radar is a great way to find out the shape of stuff in space like asteroids. If you’ve ever seen one of the “images” of an asteroid taken by a telescope like Arecibo and wondered how a radar antenna can be used to take a picture, then wonder no longer! Just take a look at Emily Lakdawalla’s post about radar imaging and all your questions will be answered.

If radar images are not your cup of tea, then maybe you’d prefer to learn about an old-school optical telescope: the Radcliffe 1.9 meter telescope. Markus shares the joy of handling the massive old wrought iron telescope in this post at Supernova Condensate.

Not a fan of old school ‘scopes? Well, perhaps I can interest you in some futuristic  Hypertelescopes? Next Big Future also has some cool posts about even more far-out ideas like Dyson Swarms and Dyson bubbles and “statites” – structures that hover above a star by balancing its gravitational force with its radiation pressure.

We’re a long way from that level of engineering, but solar sail technologies are getting more advanced. Centauri Dreams has a post about the Japanese IKAROS mission: an interplanetary solar sail that also uses its sail as a solar panel to generate electricity! I hadn’t heard of this mission, but it sounds really cool!

Whether you’re talking about star-enveloping Dyson spheres or relatively simpler missions, you have to wonder what drives exploration, particularly since big steps forward like the Apollo program come so rarely. Well, 21st Century waves talks about the idea that what we’re really dealing with is a chaotic system in this post on how complexity drives exploration.

Of course, sometimes it’s just the brilliance of one person that makes the difference, and lights the path forward, and Robert Goddard is a great example. Over at Music of the Spheres, there’s a great post about Goddard that takes a look as some of his earliest thoughts on space and also some of his inventions, which are now available online thanks to Google Patents.

Weird Sciences contributed three posts this week: First up, some thoughts on why Stephen Hawking is wrong about aliens and the threat they pose. Also, some thoughts on the implications of self-replicating machines. And third, visualizing the fourth spatial dimension.

Speaking of weird, what does Weird Warp have for us this week? Why it’s a nice, informative (and actually not very weird!) post all about the ins and outs of comets, everyone’s favorite icy visitors to the inner solar system.

While we’re back on the subject of “things that are in the inner solar system”, let’s take a look at Astroblogger Ian Musgrave’s post about how to use the moon to find stuff in the night sky. Ian even provides some scripts for the free programs Celestia and Stellarium!

Once you have rounded up your friends and family and taken them on a tour of the night sky using the moon as your guide, you’re bound to start getting pelted with questions. Luckily, “We are all in the gutter” has started a new “how do we know” feature. Their first post in the series is an answer to the question: “How do we know how old the universe is?” Do you have other “how do we know”-type questions? Contact the “We are all in the gutter” folks and get your answer!

Our penultimate post is from Steinn Sigurdsson, who reports on the unfortunate incident of the Nuclear Compton Telescope: a balloon-borne telescope that crashed in Australia during an attempted launch earlier this week. Condolences for those on the telescope team; it’s painful to watch so much work fall apart at its culmination.

And finally, on a (much) lighter note, what you’ve all been waiting for. Toothpaste ingredients! Which of course, logically, lead us to discover Amanda Bauer’s secret alter ego: the Science Ninja. This post makes me wish that a) all products had ingredient lists like the one on that toothpaste, and b) that I, too, was a science ninja.

Update: one late addition to the carnival! Nancy Atkinson at Universe Today is working on a series of posts entitled “13 Things that Saved Apollo 13“. The main article has link to the rest of the articles. Very interesting stuff!

Update 2: One more latebreaking addition! Out of the Cradle has a nice review of the book “The Big Splat, or How the Moon Came to Be”.

Phew! Well, that does it for this week’s Carnival of Space! It’s been a wild ride, as always. Thanks again to Fraser for letting me host, and thanks to all the space bloggers who contributed!



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