Tag: Mercury

… 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

Planetary alignment pyramid scheme

By Phil Plait | August 20, 2012 12:46 pm

What the heck is in the air this past week? First we see a simulated image of the sky from Mars go massively viral because people thought it actually showed Earth in the Martian sky, then a clearly Photoshopped pic of two "Suns" setting on Mars gets passed around.

And now a new slice of oddness enters the field: a picture of a planetary alignment over the Giza Pyramids, saying this only happens once every 2737 years. Because planetary alignments and the pyramids play such a large role in New Age/astrological beliefs, there is clearly some sort of spiritual message implied here.

Well, I hate to be a thricely-bursting-bubble person, but here we go again, again. Let me be clear: while there will be an event more-or-less like this in December, and it should be pretty and quite cool to see, the claims being made are somewhat exaggerated. The picture itself isn’t real, and the planets won’t really look like that from Giza. Also, alignments like this happen fairly often, though to be fair getting them spaced out to fit over the pyramids in this way probably is relatively rare.

Busting your Cheops

Here’s the picture making the rounds:

It clearly shows the three pyramids in Giza, Egypt, with three planets above them. There are various versions of this picture I’ve seen; most are like this with almost no explanation. Some say the planets are Mercury, Venus, and Saturn, and some mention this is what it will look like on December 3rd, 2012, just before sunrise.

First, this obviously cannot be an actual photo if the event hasn’t happened yet! This must be a Photoshop job. That’s fine if it’s only to show what things are supposed to look like, and no one is claiming this is an actual photo.

However, it hardly matters. There are lots of other problems with this planetary alignment claim.

What’s your angle?

The first thing I did when I saw this was ask: is there really going to be a close conjunction of three planets on December 3rd?

The answer is yes! Mercury, Venus, and Saturn will all be within a relatively small distance of each other in the sky on that date. This isn’t a particularly tight configuration like Venus and Jupiter were earlier this year – in this case, they’ll be 14 degrees apart, nearly 30 times the width of the full Moon on the sky – but it’s still pretty nifty.

The second thing I did, though, was ask myself: will they really look like that in the sky as seen from Giza?

The answer this time is no. I used the software planetarium program SkySafari to show what the three planets would look like in the sky before sunrise on December 3rd as seen from the location of the pyramids, and got this:

In this picture, the yellow line is the ecliptic, the path of the Sun in the sky through the year. The green horizontal line is the horizon, and the three planets are labeled.

Note the angle of the planets: in the picture going viral, the planets are much closer to horizontal, but in reality the line connecting the planets is at a much steeper angle. It’s nearly vertical, in fact. This may not seem like a big deal, but having the planets closer to horizontal like in the viral picture is more spectacular than what will really happen, exaggerating the claim.

Not only that, but in the pyramid picture the planets are almost exactly on a line, like beads on a string. But as you can see in the picture above, they’re not nearly that colinear. Again it’s looking like the pyramid picture is exaggerating the situation.

Mirror, mirror

I noticed something else funny as well.

Here’s a satellite view of the three pyramids, courtesy Google maps:

Read More

Mickey Mouse MESSENGER Mercury

By Phil Plait | June 15, 2012 8:58 am

MESSENGER is a spacecraft that’s been orbiting Mercury since early 2011, sending back to Earth huge amounts of data about the tiny planet, including incredible high-resolution close-up images. It’s an amazing mission…

… but I wonder what kind of Mickey Mouse outfit would put up this kind of image for display?

[Click to enmusculate.]

Well, at least I know to whom NASA can turn if the current budget cuts get through Congress.

Image credit: NASA/Johns Hopkins University Applied Physics Laboratory/Carnegie Institution of Washington

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- X Crater: First Class
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CATEGORIZED UNDER: Astronomy, Pretty pictures

The Sun is 1,392,684 +/- 65 km across!

By Phil Plait | March 21, 2012 7:00 am

You would think that, of all the astronomical measurements we could make, one of the best known would be the diameter of the Sun.

You’d be wrong. It’s actually really hard to measure! For one thing, we sit at the bottom of an ocean of air, gas that is constantly moving around, mucking up precise measurements. For another, our telescopes themselves can be difficult to calibrate to the needed accuracy to get a really solid measurement of the size of the Sun.

Nature, however, provides us with a way to measure our nearest star. Naturally! And it involves Mercury, the smallest and, critically, the closest planet to the Sun.

In 2003, and again in 2006, Mercury passed directly across the face of the Sun as seen from Earth (the picture above is a view of the 2006 transit as seen by SOHO; a very short animation was made from this as well). Mercury’s orbit is tilted a little bit with respect to Earth’s, so these transits don’t happen terribly often, occurring only every few years. But because we know the orbit of Mercury so well, and our own distance from the Sun, by precisely timing how long it takes the diminutive world to cross the Sun, we can get a very accurate measurement of the Sun’s diameter.

A team of scientists did exactly this, using SOHO, which is a solar observing and solar-orbiting satellite. Because it’s in space, it doesn’t suffer from the problems of peering through a murky, dancing atmosphere. They were able to measure the timing of Mercury’s passage of the Sun to an accuracy of 3 seconds in 2003 and 1 second in 2006. They had to take into account a large number of effects (the Sun’s limb is darker than the center, which affects timing; they had to accurately measure the position of Mercury; they had to account for problems internal to SOHO like focus and the way it changes across the detector; and, of course, correct for the fact that Mercury cut a chord across the Sun and didn’t go straight across the diameter — but that only took knowledge of Mercury’s orbit and some trig) but when they did, they got the most accurate measure of the Sun’s diameter ever made: 1,392,684 +/- 65 km, or 865,374 +/- 40 miles.

That uncertainty of 65 km is quite a it better than what can be done from the ground, amazingly. It may sound like a lot, but it actually represents an accuracy of 99.995%! The Sun is big. Really, really big.

… and they’re not done. The authors are going to observe the Transit of Venus coming up in June, hoping it’ll improve their measurements. I’ll be very curious to see how that goes; Venus has an atmosphere which I would think would confound the observations. They may have ways around that though.

Either way, I think this is completely fascinating. Even thrilling! The Sun is the brightest thing in the sky, the center of our solar system, the basis of light and heat and life on Earth, and the best-studied star in the Universe.

And here we are, just now figuring out how big it is. Sometimes the simplest things can be the hardest, I suppose.

Image credit: NASA/EDA/SOHO

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CATEGORIZED UNDER: Astronomy, Cool stuff, Science, Top Post

Top 14 Solar System Pictures of 2011

By Phil Plait | December 8, 2011 6:30 am

Jupiter and Ganymede in exquisite detail

By Phil Plait | October 7, 2011 1:32 pm

If you go outside shortly after sunset and face east, you’ll see a brilliant white "star" madly shining down on you. That’s no star: it’s Jupiter, king of the planets, the brightest object in the sky right now after the Sun and the Moon. Now is the best time to observe it, since the Earth is placed directly between the giant planet and the Sun, meaning we’re as close to it as we’ll get all year.

"Amateur" astronomer Emil Kraaikamp took advantage of the situation, and, with his friend Rik ter Horst — who crafted his own 40 cm (16") mirror telescope — took this amazing shot of Jupiter:

[Click to enjovianate.]

I found this image on the Astron/Jive image of the day page (you should really subscribe to their RSS feed), and Emil gave me permission to use it here. Isn’t it lovely? The level of detail is quite incredible, about as good as you can possibly get with a 40 cm ‘scope. They used a video camera to capture a lot of frames, and then pick the best ones to add together. Earth’s atmosphere roils and shifts, causing images to blur out, so this technique compensates for that — and Jupiter obliges by being very bright, allowing for lots of short exposures in rapid succession.

The little guy below Jupiter and to the right is the moon Ganymede, which, if Jupiter weren’t there, would be considered a planet in its own right. It’s the biggest moon in the solar system, and actually comfortably larger than Mercury — though also much less massive, because Mercury has lots of iron, while Ganymede is mostly rock and ice. It’s incredible that advances in technology have made it possible to capture such detail on an object 600 million km (360 million miles) away! The image on the right of Ganymede is a NASA map of the moon based on space probe images, showing that those features Emil and Rik captured are real.

Emil tells me it’s been cloudy where he is lately, which is too bad. It’s been touch-and-go here with the weather, but seeing this is making me think of hauling out my own ‘scope and taking a look. I should get on that before the snow starts to fall here in Boulder…

In the meantime, check out the Related posts links below to see more of Emil’s amazing work.

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- Jupiter rolls into view
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CATEGORIZED UNDER: Astronomy, Pretty pictures

Clair de Mercury

By Phil Plait | September 30, 2011 6:30 am

I know I just posted a MESSENGER photo of craters, but this one is different and spectacular enough that I figure, why not? I love a big, splashy, wide-angle shot of a rayed crater! So here’s the lovely, 80-km wide impact crater Debussy on the surface of Mercury:

[Click to haphaestenate.]

Craters make rays when the ejected material blasted out forms long plumes which fall across the surface. On airless worlds, those trajectories are ballistic, heading straight out from the center of the impact. Deeper material tends to be a lighter shade than surface material, so the interior of the crater and the rays are lighter than surrounding surface stuff. You can also see what’s called the apron, the layer of material that falls immediately around the crater, surrounding it (that’s more clear in an earlier image of the crater looking more straight down on it).

Rayed craters are common (even on our Moon; take a look at Tycho!), and usually indicate the impact was recent (geologically), since the rays eventually get eroded by the solar wind, cosmic rays, and subsequent meteorite impacts. Debussy is therefore one of the younger features on Mercury. It still has that youthful shine.

Image credit: NASA/Johns Hopkins University Applied Physics Laboratory/Carnegie Institution of Washington

Related posts:

- Jaw-dropping mosaic of Mercury’s battered, beautiful face
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CATEGORIZED UNDER: Astronomy, Pretty pictures

Mercury's hot and cold south pole

By Phil Plait | September 28, 2011 6:30 am

The MESSENGER spacecraft, orbiting Mercury for nearly a year now, took this pretty nifty shot of the tiniest planet’s south polar region, showing deep, dark craters in the Goethe basin:

This region is about 300 km (180 miles) from the true south pole of the planet. On Earth that might be a cold spot, but on Mercury, cold spots are hard to come by.

… however, see how dark those craters are? Since they’re near the pole, the Sun never gets far above the horizon for them, and the crater floors are shrouded in perpetual darkness. That does make them cold! Well below the freezing point of water, it’s thought. Interestingly, radar observations of Mercury have indicated something in the crater floors is highly reflective, and water ice fits that bill. It’s not at all confirmed, but it’s entirely possible Mercury — a planet hot enough in the open Sun where zinc can exist as liquid lakes on the surface — might have frozen lakes of ice locked in crater bottoms near its poles!

While gazing idly at this picture, another thought popped into my head. Read More

CATEGORIZED UNDER: Astronomy, Cool stuff, Pretty pictures

Jaw-dropping mosaic of Mercury's battered, beautiful face

By Phil Plait | May 13, 2011 7:00 am

We live in an era of wonder, where people send robots to other worlds and view them close up. These machines get bathed in radiation, searing heat, bitter cold, suffocating vacuum, and they keep running. Moreover, they send their data back digitally, which can then be stored in a database and, if permissions are given, accessed by the public. And a subset of that public is educated in the ways of digital media, able to stitch together pictures, carefully aligning them, balancing them, coordinating borders and overlap regions.

The result? This:

Yegads. That is Mercury as seen by the MESSENGER spacecraft in 2008, as it flew by the planet for the first time. It would do so again before finally entering orbit in March 2011. But as it left the smallest planet, it snapped a series of wide angle and high-resolution images.

Gordon Ugarkovic is a Croatian software developer. He’s also an amateur image processor… for a sufficiently wide definition of "amateur". He takes space images and works his prowess on them, creating dramatic and beautiful images like this one of Mercury.

Click the picture to embiggen it, or you can also download a vast 5000 x 5000 pixel version that is, frankly, spectacular. Gordon used over 30 of the high-res frames from MESSENGER’s Narrow Angle Camera to make this mosaic, and then used images from the Wide Angle Camera to balance the color.

The 25 megapixel image is nothing short of amazing. Scrolling across it is like flying across the planet. I see features there I hadn’t noticed before, like a pale dark streak just south of Mercury’s equator, sharp cliffs called scarps that litter the surface, craters with bright rays of ejected material streaming out of them. It’s breathtaking.

Gordon has also done images of Saturn, Jupiter, and moons galore. You can follow his work at the Unmanned Spaceflight forum, or peruse his Flickr stream. But be warned: better have a lot of time handy. You’ll be spending it there.

Image used with permission. Tip o’ the heat shield to Dan Durda for tipping me off to the picture.

Related posts:

- MESSENGER’s family portrait
- More Mercury!
- Mercury hides a monster impact
- Watermelon planet (a personal favorite of mine)

CATEGORIZED UNDER: Astronomy, Cool stuff, Pretty pictures

X Crater: First Class

By Phil Plait | May 9, 2011 6:59 am

When an asteroid or comet impacts a planet, the explosion ejects huge amounts of material, sending it flying in all directions. But there are also plumes of material, long fingers of rock and dust that stream out as well. The boulders and such inside this plume then fall back to the ground, making linear chains of secondary craters. We see lots of these on our Moon, moons in the outer solar system, and Mercury, too.

If these features are long enough, it’s inevitable two chains from two different primary craters would cross somewhere. And it turns out this has been seen… but where?

Well, X marks the spot!

This MESSENGER image of Mercury shows exactly that: two crater chains from two separate impacts crossing over each other (and a third, shorter chain is at the bottom, too). They’re almost exactly perpendicular to each other, which is cool, and the intersection happens to lie in a big, shallow crater about 120 km (72 miles) across that fills this image. Unfortunately, MESSENGER hasn’t been orbiting Mercury long enough to have surveyed the whole planet yet, so I wasn’t able to find the source craters of these two chains.

Interestingly, both chains have elongated craters at their ends, one on the upper left and the other at the top. That indicates a very low-angle impact; anything hitting the ground from an angle above about 10° tends to make a circular crater. However, the one on the left appears to be right on the big crater’s rim, so the elongation may be due to the ground angle changing. The other may be coincidence; both are far too small to have been the source craters for the chains.

I’m not sure there’s any real scientific value in knowing these crater chains intersect or examining the intersection in detail. Still. They’re fun to look at, fun to explore, and they’re just seriously nifty.


Image credit: NASA/Johns Hopkins University Applied Physics Laboratory/Carnegie Institution of Washington

Related posts:

- More Mercury!
- Watermelon planet
- Machault by MESSENGER
- MESSENGER: Three days out from Mercury
- MESSENGER’s family portrait

CATEGORIZED UNDER: Astronomy, Pretty pictures

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