Tag: Moon

Libration libretto

By Phil Plait | September 17, 2012 12:30 pm

Sticking with my theme of art and astronomy

Back in March 2012, I posted a remarkable video from NASA’s Goddard Space Flight Center (where I used to work) showing the motion of the Moon and how its appearance changes over the course of the year. The video went somewhat viral – probably because of the awesome music I added from Kevin Macleod – and I was pleased with it.

But then my friend, the skeptic and awesomely talented mezzo-soprano Hai-Ting Chin, asked me about libration, because she was working on a musical piece about it. She’s done several scientific songs with her partner Matthew Schickele, so it’s not as weird as it sounds. At least, not for them. Or me.

So we chatted back and forth a bit, and the result is this amazing piece of haunting and lovely music.

She sang this at the 2012 NECSS, and I wish I could’ve been there to hear it. Wow. My sister’s a mezzo-soprano, so I have some familiarity here: Hai-Ting’s voice is incredible. The piano is played by Erika Switzer.

I know the words to operatic music can be difficult to understand, so here are the lyrics:

This is animation.
Each frame represents one hour;
the whole, one year.
The moon keeps the same face to us,
but not exactly the same face.
Because of the tilt and shape of its orbit
we see the moon from slightly different angles.
In a time lapse it looks like it’s wobbling.
This is libration.
That rocking and tilting is real,
it’s called libration.

The moon’s orbit is not a circle,
but an ellipse.
The speed varies,
but the spin is constant.
Together these geometries
let us look East a little more,
then West a little more.
And the orbit’s tilt
let’s us look South a little more,
then North a little more.
This is libration.
The moon’s libration.

How flipping cool is this? Hai-Ting and Matt write the Scopes Monkey Choir blog, which you should have in your feed reader.

I love how science inspires art. Love. I hope to see more and more of this kind of scientific art as time goes on. The more ways we can show people how amazing and wonderful the Universe is, the better.


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CATEGORIZED UNDER: Astronomy

… I'm just on my way up to Clavius

By Phil Plait | September 14, 2012 12:08 pm

Thierry Legault is no stranger to this blog (see Related Posts below or search the blog for his stuff); his astrophotos are always amazing. Always. And he just sent me a link to a new batch that are jaw-dropping: very high-resolution images of the Moon, Mercury, and even Uranus. As an example, here is a shot he got of the giant crater Clavius on the Moon:

I shrank that image way down to fit the blog; click it to monolithenate. The detail is astonishing. There are lots more shots of the Moon like that on his site; and you most certainly want to click the links to Uranus and Mercury above. You can see details on both planets (the surface for Mercury, and cloud tops for Uranus)!

I always say that astronomy is much more than just pretty pictures, but sometimes, when the pictures are as pretty as this, astronomy is quite simply art.

[One gold star to anyone who can identify the title of this post without looking it up.]

Image credit: Thierry Legault


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CATEGORIZED UNDER: Astronomy, Pretty pictures

A lunar crater is graben the spotlight

By Phil Plait | September 11, 2012 7:00 am

I am endlessly fascinated by the Moon. There may be an inherent bias there because it is, after all, the closest astronomical object in the sky. Still, it has an amazingly varied surface with lots of really odd features.

One of my favorite types of things to look at are overlapping features. It can produce a very complicated terrain, difficult to understand. Or can also create a lovely tableau that cleanly separates the two features, like this very pretty shot from Lunar Reconnaissance Orbiter (LRO) showing a fresh crater near a graben:

[Click to enlunenate.]

A graben is a crack or fracture. They form on the Moon when the crust is stretched, splitting the surface. They look like long, relatively straight and narrow valleys with steep sides. You can only see a part of it on the right side of the image above; the Sun is shining from the right and illuminating the left-hand side of the graben. The picture below is zoomed out and should help you see the situation.

The crater is clearly younger than the graben feature. The radial streaks around the crater are called rays, and are formed when plumes of material ejected from the impact fall back down to the ground. They’re common around young craters; solar wind, later impacts, and even thermal compression and expansion of rocks over the Moon’s day-night cycle eventually erode them away.

You can see the rays extended over and into the graben, so the crater must be younger. It’s hard to say just how much younger, but even relative ages can help geologists understand the lunar surface better. And detailed images like this – you can see individual blocks of rock inside the crater itself – are crucial for study. Someday, I think, human geologists will be investigating places like this in person, and mapping missions like LRO will make that possible.

Image credit: NASA/GSFC/Arizona State University


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CATEGORIZED UNDER: Astronomy, Cool stuff, Pretty pictures
MORE ABOUT: crater, graben, LRO, Moon, rays

New Moon from a new moon

By Phil Plait | September 9, 2012 7:00 am

When I get too frustrated with things, when I’m annoyed at people, when the dickishness of the commentariat gets too overwhelming, I’ll just click the bookmark I made that goes to this picture:

Sigh. Much better.

The International Space Station was 400 kilometers (240 miles) above the US northwest coast on August 21, 2012 at 05:42 GMT (9:42 p.m. August 20 local time) when an astronaut faced west, looked over the Pacific ocean, and took this picture of the new Moon just after sunset.

Nice.

Image credit: NASA. Tip o’ the spacesuit visor to Fragile Oasis on G+.

CATEGORIZED UNDER: Astronomy, NASA, Pretty pictures

Time lapse: When the Moon ate Venus

By Phil Plait | August 31, 2012 6:30 am

On the morning of August 13 – 14 (depending on where you were in the world) the Moon slipped directly in front of Venus in the sky, an event called an occultation. It was cloudy here in Boulder so I missed it, but halfway across the world in Korea, astrophotographer Kwon O Chul had a magnificent view, and made this lovely time lapse video of the event.

Occultations like this are relatively rare. If all the planets and moons orbited the Sun in exactly the same plane – that is, if you looked at the solar system from the side and all the orbits aligned perfectly, like looking at a DVD from the side – we’d see occultations all the time.

But in reality all the orbits are tilted a little bit. Venus circles the Sun in an orbit canted by about 3° compared to Earth’s. The Moon’s orbit is tilted by 5 °. The Moon orbits the Earth once per month or so, but it usually passes by Venus, missing it by a bit because the orbits aren’t aligned. But sometimes, every few years, the dance comes together, and the Moon wil slip directly in front of Venus.

An occultation is an amazing thing to see. I saw a lunar Venus occultation when I was a kid and just starting out as an amateur astronomer. It takes a few seconds for the Moon to cover a planet, so you can watch as the planet dims and then pops out when it gets completely covered. Also, the Moon commonly passes in front of stars, which are so far away and appear so small they just wink out, blip!

You can get a list of upcoming occultations at the International Occultation Timing Association website. If you get a chance to see the Moon occult a star, take it! Binoculars help a lot, and it’s fun to watch the star just suddenly blink out.

Tip o’ the dew shield to Astropixie.

CATEGORIZED UNDER: Astronomy, Cool stuff, Pretty pictures

BAFact Math: The Sun is 12 *trillion* times brighter than the faintest star you can see

By Phil Plait | August 28, 2012 10:00 am

[BAFacts are short, tweetable astronomy/space facts that I post every day. On some occasions, they wind up needing a bit of a mathematical explanation. The math is pretty easy, and it adds a lot of coolness, which I’m passing on to you! You’re welcome.]


Today’s BAFact: The Sun is 12 trillion times brighter than the faintest star you can see with your naked eye.

In yesterday’s BAFact, I showed how the Sun is about 400,000 times brighter than the full Moon – and I showed my math. That’s an amazing brightness difference, but while I was writing it I had to wonder: how much brighter is the Sun than the faintest star you can see?

The faintest stars visible to the naked eye have a magnitude of about 6. This depends on lots of stuff, like how dark the sky is, how good your eyesight is, and so on. Some people with excellent vision can see stars down to magnitude 7, and there are reports of a few extraordinary people who can see even fainter. But on a dark night, the average person can just barely see 6th magnitude stars.

Let’s use that number then. All we have to do is plug that into the equation I gave yesterday (and remembering that the Sun has a magnitude of -26.7):

Brightness ratio = 2.512(6 – (-26.7)) = 2.51232.7 = 12 trillion

Yegads! That’s 12,000,000,000,000 times brighter!

Now, to be fair, that’s not really the brightness range your eyes can detect. You can’t look right at the Sun easily or comfortably; it’s simply too bright. So the range of brightness your eye can see is probably smaller.

We can put a lower limit on it easily enough using the Moon. The Moon is the second brightest object in the sky, and we know we can look at that easily enough, so let’s do that math (the Moon’s magnitude is -12.7 when it’s full):

Brightness ratio = 2.512(6 – (-12.7)) = 2.51218.7 = 30 million

Wow. So you can comfortably see objects over a brightness range of 30 million. That’s impressive! The eye is a pretty cool little machine.

As an aside, your eye isn’t linear; it’s logarithmic (in reality, it’s more complicated than this, and I’m simplifying, but close enough). In other words, a star giving off twice as much light doesn’t look twice as bright as another. The way your eye responds to light squeezes down the scale, making it easier to see fainter and brighter objects at the same time.

So how faint do objects get? Ah, that’ll be tomorrow’s BAFact. Stay tuned!


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CATEGORIZED UNDER: Astronomy, BAFacts
MORE ABOUT: magnitudes, Moon, star, Sun

BAFact Math: The Sun is 400,000 times brighter than the full Moon

By Phil Plait | August 27, 2012 10:02 am

[BAFacts are short, tweetable astronomy/space facts that I post every day. On some occasions, they wind up needing a bit of a mathematical explanation. The math is pretty easy, and it adds a lot of coolness, which I’m passing on to you! You’re welcome.]


Today’s BAFact: The Sun is 400,000 times brighter than the full Moon in the sky.

If you’ve ever looked at the full Moon through a telescope you know how painfully bright it can be. But you can do it if you squint, or use a mild filter to block some of the light.

On the other hand, if you try the same thing with the Sun (hint: don’t) you’ll end up with a fried retina and an eyeball filled with boiling vitreous humor.

So duh, the Sun is much brighter than the Moon. But how much brighter?

Astronomers use a brightness system called magnitudes. It’s actually been around for thousands of years, first contrived by the Greek astronomer Hipparchus. It’s a little weird: first, it’s not linear. That is, an object twice as bright as another doesn’t have twice the magnitude value. Instead, the system is logarithmic, with a base of 2.512. Blame Hipparchus for that: he figured the brightest stars were 100 times brighter than the dimmest stars, and used a five step system [Update: My mistake, apparently he didn’t know about the factor of 100, that came later.]. The fifth root of 100 = 2.512 (or, if you prefer, 2.5125 = 2.512 x 2.512 x 2.512 x 2.512 x 2.512 = 100), so there you go. I’ll give examples in a sec…

Secondly, the other weird thing about the magnitude system is that it’s backwards. A brighter star will have a lower number. It’s like an award; getting first place is better than third. So a bright star might be first magnitude, and a dimmer one third magnitude.

To figure out how much brighter one star actually is than another, subtract the brighter star’s magnitude from the dimmer one’s, and then take 2.512 to that power. As an example, the star Achernar has a magnitude of roughly 0.5. Hamal, the brightest star in the constellation of Aries, has a magnitude of 2.0. Therefore, Achernar is 2.512(2.0 – 0.5) = 2.5121.5 = 4 times brighter than Hamal. So you can say it’s four times brighter, or 1.5 magnitudes brighter. Same thing.

It’s weird, but actually pretty handy for astronomers. And it doesn’t stop at 0. A really bright object can have a negative magnitude, and the math still works. For example, Sirius, the brightest star in the night sky, has a magnitude of about -1.5 (making it 6 times as bright as Achernar – check my math if you want). Which brings us to the topic at hand…

The Moon is pretty bright, and when it’s full has a magnitude of about -12.7. That’s bright enough to read by! But the Sun is way, way brighter. It’s magnitude is a whopping -26.7. How much brighter is that?

Well, it’s 2.5(-12.7 – (-26.7)) = 2.514 = 400,000.

In other words, the Sun is 400,000 times brighter than the full Moon!

This would explain why you can look at the Moon easily enough with just your eye, but trying that with the Sun is not – wait for it, wait for it – a bright idea.

Image credit: NASA/SDO


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CATEGORIZED UNDER: Astronomy, BAFacts, Cool stuff
MORE ABOUT: brightness, magnitudes, Moon, Sun

Pow! ZOOM! To the Moon!

By Phil Plait | August 26, 2012 6:56 am

[I was going to wait to post this until next week, but with Neil Armstrong’s death I’ve decided to put it up now. If he could risk his life open up the Moon as a world for all mankind, the least I can do is share it as much as I can.]

If you need a little extra dollop of awesome in your day, then try zooming in and flying over the surface of the Moon, care of astronomer Pete Lawrence’s incredible mosaic of our nearest cosmic neighbor:

[You may need to refresh this page if you don’t see the Moon picture directly above this sentence.]

Click the button on the lower right that makes the picture expand to fit the browser, then zoom in and out using the + and - buttons. Click and drag to fly around. Make vrooom vroom noises.

Make sure you zoom in all the way and then cruise over the terminator, the day/night line. Trust me.

This ridiculously cool image is composed of 166 separate sub-images taken over the course of just 45 minutes on August 10, 2012. He used a Celestron 14" with a video camera. Get this: each of the 166 sub-images is actually made up of 1000 separate video frames, which are stacked and processed to pick out the best bits of each one, resulting in a single high-quality frame. So he really took 166,000 images!

That’s so cool. I love what digital cameras have done for astronomy.

Pete’s images of the sky are amazing; check them out at digitalsky.org, and you can keep up with him on Twitter.

He also sent me this shot he took in 2009 showing the Moon in three different phases; you must click it to see it full size. It’s pretty impressive.

I should probably Photoshop a wolf in there.

Tip o’ the lens cap to Will Gater.

CATEGORIZED UNDER: Astronomy, Cool stuff, Pretty pictures
MORE ABOUT: Moon, Pete Lawrence

Peaking into lunar craters

By Phil Plait | July 13, 2012 6:57 am

Large impacts are fascinating. There’s the thriller-movie aspect of them, of course, spiced with enough reality to make them legitimately scary. But the physics of them is equally enthralling, and complex enough that it will be a rich field for scientists to study for years to come.

The good news for both these aspects is our Moon. Seriously! There are enough craters there for anyone to be happy studying them, and since the Moon is a giant lifeless chunk of rock, impacts there seem less urgently threatening.

I want to show you two craters on the Moon that are very different, and therefore very interesting.

First up, Copernicus. Or more accurately, a small part of this 90+ km (55 mile) wide impact feature: its central peaks.

[Click to enselenate.]

This image was taken by NASA’s wonderful Lunar Reconnassance Orbiter. Copernicus is a big crater, and easy to spot even with binoculars since it sits in a vast lava plain; the surrounding material is darkish grey, while the crater is far brighter. It’s also surrounded by a gorgeous system of rays: linear streaks caused by the collapsed plumes of material after the asteroid or comet smacked into the Moon to form the crater itself.

Copernicus has a series of mountains in its center, the tallest over a kilometer high. These weren’t created in tectonic events like on Earth, though! Giant impacts that cause big craters have weird physics. The pressure upon impact can be so high that the rock in the surface flows like a liquid. It splashes outward, then flows back in, surging upwards in the middle of the impact point. This video showing water dropping into various surfaces might help:

Lots of craters have such central peaks (like Tycho). But not all… like the spectacular Giordano Bruno, an impact crater on the lunar far side measuring 21 km (13 miles) across:

Read More

Will we ever live on the Moon?

By Phil Plait | June 14, 2012 9:55 am

When will we live on the Moon?

It’s a fair question. Newt Gingrich’s assininery notwithstanding, it’s worth considering carefully. While I’m pretty sure that at some future date we will have a permanent human colony on the Moon — perhaps even a thriving nation over time — the more interesting bit to me is how something like this will come to be.

So when I was asked by the BBC to write an article for their blog called "Future", as part of a series called "Will We Ever…?", the idea of humans living on the Moon seemed like a good topic. My thoughts on this are now up on their site: Will We Ever… Live on the Moon? It outlines one possible path toward a lunar base, and it’s not necessarily the only one. But given recent developments and our current circumstances, the situation I describe in that article isn’t unrealistic.

If we are to one day live on the Moon — and I do seriously think we will — this may be the way it happens. Give it a read and see if you agree!

Image credit: Small Artworks


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CATEGORIZED UNDER: Astronomy, Piece of mind, Space
MORE ABOUT: BBC, lunar colony, Moon
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