Blogs / Bad Astronomy

Hot on the heels of the post the other day about the winds on Mars blowing the sand dunes and visibly moving them across the planet’s surface comes this new satellite image of a huge sandstorm raging across the planet:

Of course, I’d forgive you if you interpret my saying "the planet" as meaning Mars. However, this picture is of Earth! Specifically, the Middle East. This March 4^th image from the Terra satellite shows a plume of sand 100 km (60 miles!) across sweeping from Saudi Arabia over Kuwait and into Iran.

In some ways, Mars and Earth are very similar. Sometimes, it’s even hard to tell them apart…

The BBC is reporting that a previously unknown potential impact crater has surfaced in the Congo. This region was heavily forested, hiding the crater, but recent widespread deforestation has revealed the ancient impact scar.

Obviously, I’m conflicted about this.

If this is an impact crater (it has not yet been confirmed), it’s about 40 km (25 miles) across, making it one of the largest seen on the Earth. We haven’t been hit by a big asteroid in a long time, and erosion has erased most of the impact craters. There’s a picture of the crater on that link above, and the crater is obviously very old.

It’s fascinating to know that such a large feature can be hidden at all, but it’s sad indeed on how it got uncovered. I can hope no one would be so crass as to suggest we should continue to deforest our planet in hopes of finding more treasures, but I have seen far worse things suggested to support unrestrained mining, drilling, and polluting. I’m glad something good came of this horrific practice, but all things told, I think I’d rather it had remained tucked away among thousands of square kilometers of trees.

Tip o’ the Whipple Shield to Ted Judah.

Word from New Zealand Zimbabwe is that a religious sect there — which believes in prayer over vaccinations — may be responsible for the deaths of over one hundred children from measles.

I believe people have the right to practice their religious beliefs… up until they start to hurt others. It has been proven over and again that prayer does nothing to heal disease over the placebo effect, while vaccinations have saved hundreds of millions of people. That’s math I can do pretty easily.

If this story is true, I certainly hope that the people involved are introduced to the inside of a jail cell for a long, long time. They can happily pray there all they want, and on the outside those children can get the vaccinations that will save their lives.

The Cassini spacecraft recently passed very near the tiny moon Helene and returned amazing pictures of it.

Helene is a dinky iceball, only about 36×32x30 km (22×19x18 miles) in size (this picture has an incredible resolution of about 113 meters (123 yards) per pixel). It circles Saturn in the same orbit as the much larger Dione, and is in fact in the larger moon’s leading Trojan point: a peculiar artifact of gravity when an object orbits another. It’s a gravitational stable point, like a valley between two mountains.

Clearly battered, Helene has an oddly smooth appearance, which may be due to the feeble gravity of the moon collecting dust also trapped in the Trojan point. At The Planetary Society Blog, Emily has more info on Helene and speculates about its appearance. She also has a good description of how the Trojan points work.

Credit: NASA/JPL/Space Science Institute

The 144th Carnival of Space is up at my bud Ian O’Neill’s Discovery Space News blog. Now does this post title make sense?

Anyway, go there, read it, study it, and that way you’ll pass the test. Oh, you didn’t know this will be on the test? C’mon, you’re a human, and this is life. Everything is on the test.

Every time a psychic gets surprised by something, the world gets a little smarter. I hope.

If that’s true, then our collective IQ went up a solid 8 points when the Securities and Exchange Commission filed a suit against "America’s Prophet" Sean David Morton on claims he’s a big ol’ phony.

If only he had spelled it "profit" instead, then he wouldn’t have been falsely advertising. And given that he made a cool $6 million off of gullible dupes, that moniker would certainly fit better.

Now, of course this doesn’t mean all psychics are knowing frauds any more than a scientist who perpetrates knowing fraud indicts all other scientists.

However, science has given us spaceflight, agriculture, computers, medicine, telescopes, and a deeper and quantitative understanding of the Universe from the quantum level out to its observable edge.

Psychics have given us, well… y’know… um… oh! They make it easier for non-critical people to carry their now much-lighter wallets around.

Right. Well, to paraphrase Philip J. Fry: psychics 0, regular science a billion.

Tip o’ the crystal ball to Dale Martin.

The website called Today I Found Out has an interesting post on Sun factoids, including its color as designated in hex code: #FFF5F2. That code is actually taken from the site vendian.org, put together by Mitchell Charity. He has other star colors listed as well. I found the codes for different stellar types interesting.

The star type is listed, along with the RGB and hex values. The stars go from hottest at the top to coolest at the bottom, and the Sun is roughly a G2V.

The colors are relatively good, in that they are blue at the top and reddish at the bottom. But I was surprised at the lack of color saturation, and that the cooler stars aren’t as red as I would think.

I have spent a lot of time at the eyepiece. Vega, an A0 dwarf star, is distinctly and brilliantly blue, almost a sapphire to the eye. Betelgeuse, an M1 supergiant, is a ruddy orange. I’ve seen a handful of cooler red giants, and to the eye they are very red, not the pastel orangey thing seen here.

Why is this? There are lots of reasons that come to my mind. One is that the way stars shine is inherently different than the way colors are represented on your screen. Stars are hot balls of luminous plasma, glowing like a blackbody. Unless you heat your monitor to that same temperature, you can only approximate the way a star shines, and the colors will be off.

Our eye perceives color oddly, too. Seeing a star against a black sky will give you a different sense of its color than if you see it on your monitor. Even putting a differently colored star in the same field wrecks your color sense. I’ll note that Charity’s star color page has a hex code for the color of planetary nebulae, and that’s a whole nuther can o’ worms.

In my opinion, doing this is an interesting exercise, and a wonderful "teaching moment" on how stars emit light and how we perceive color. But as an exercise in actually trying to mimic star colors, it’s a whole lot tougher than you might think. I’m not saying Charity’s colors are wrong, but I am saying that trying to get hex codes for star colors is like writing down the notes to Beethoven’s Ninth Symphony on paper. It’s a code, and has the right information in it, but it’s not the same as hearing the orchestra.

I’ll also note that the whole point of the first site’s article is that the Sun is white. This is actually an extremely difficult topic to understand — it’s not just scattered blue light that makes the Sun look yellow to us, and I’m still not convinced the Sun does look yellow to us. Charity links to a page about the Sun’s color written by my friend the astronomer Andrew Hamilton, which has some more info on it.

I think the real lesson here is that something we think of as simple — color — is not at all simple! The way colors are emitted by an object, the way our eyes detect color, and most importantly the way our brains interpret that signal, are actually extraordinarily complex processes. I think that’s a very important concept to keep in mind when pondering pretty much any issue: what we take for granted as simple is almost never any such thing.

Tip o’ the artist’s beret to Philippe Hamel.