Just some silliness: a guy attached a webcam to his cat’s collar, and the pictures it has taken are actually rather engaging. Some of his captions are a bit twee, but others made me LOL. And I wish I had thought of this! Someone should tell him to put Google ads on his site; he’ll get rich. But he’ll have to reinvest in more cats and cams.

A lot of websites are saying that the Full Moon will look huge tonight (Saturday), and urging people to go out and look. This is true, but I want to make sure people understand what’s going on. It’s not that the Moon will look any bigger tonight than it does at any other time; it’s that it stays near the horizon longer.

Any time you see the Moon rising, especially when it’s full, you can get the Moon Illusion: the appearance that the Moon is huge, looming over the Earth. I won’t go into the details here; go to that link where I wrote up a brief intro to the phenomenon.

You only get the illusion when the Moon is near the horizon; when it’s overhead the illusion vanished. Because this month is the summer solstice, tonight the Moon stays close to the horizon for northern hemisphere observers. When the Moon is full, it’s opposite the Sun in the sky. And because the Sun is high in the sky during the day during the summer, the full Moon will be low in
the sky at night. For me, in Boulder Colorado (latitude almost exactly 40 degree north), the Moon only gets to an altitude of about 23 degrees above the horizon tonight — about the width of two fists outstretched.

The angle at which the Moon rises is also small, so it takes a while to rise, prolonging the illusion.

What’s funny is that physically, the Moon should look smaller tonight than usual! It orbits the Earth in an ellipse, so sometimes it is farther from the Earth, and sometimes closer. I checked the good ol’ Naval Observatory website, and looked up the distance to the Moon for a couple of weeks centered on tonight. Here are the results:

The Moon was farthest from the Earth about a week ago (June 25), and will be closest around July 10. Right now, the Moon is a little bit farther then average, so if you were to measure its apparent size very carefully, you’d see it’s smaller than usual!

Anyway, whatever reason works for you is good enough for me tonight. Go out and take a look. And when you do, take a look to the "upper right" of the Moon — the bright "star" there is the mighty planet Jupiter, fully 40 times the diameter of the Moon, but well over 1600 times as distant. That’s where distance really matters!

I am a big fan of optical illusions; I love ‘em (see here and here and here and here). A lot of Bad Astronomy is due to one illusion or another, like the Glass Worm, but that’s incidental. I just think they’re cool.

One of my favorites is the in-out illusion, where your brain can’t tell if something is convex or concave. It’s maddening, and fun. The Mighty Optical Illusions site has one of the best examples I have ever seen of it, a spinning silhouette that’ll melt your brain. Go have a look!

I have been getting some interesting mail and comments about the Alien Sun issue. Several people are pointing out that I have been saying the Sun is native to the Milky Way, but I have no proof of that.

They’re right. I don’t. I’ve been a little sloppy in my terminology. The way I have been phrasing things makes it sound like the Sun was definitely formed in the Milky Way Galaxy, and we don’t know that for sure. What I should be saying is that we know it didn’t form in the Sagittarius Dwarf galaxy. That much is positive.

But this isn’t the first galaxy the Milky Way has cannibalized. It’s not even the only one we’re eating right now! And over time, no doubt the Milky Way has eaten several other galaxies. The Milky Way has been around for at least ten billion years, long enough to ingest other galaxies and discard the evidence. If a dwarf galaxy happened to impact our own in the plane of the disk, it might be very hard to tell what stars were originally "ours" and which came from the interloper. And given that the Sun is only 4.6 billion years old, it’s possible that some of the gas from which it formed came from Out There.

So I cannot say for sure that the Sun was born in the Milky Way, or is made from 100% Milky Way parts. I don’t know if we could ever prove it… or not. Given our location, our orbit, and other factors, it seems likely the Sun has been here the whole time. But there is always room for doubt.

So let me be clear: the Sun is not from the Sagittarius dwarf galaxy the Milky Way is currently eating. We know that. And if I had to bet, I would put money on the Sun having lived its whole life here in the Milky Way. But I’ll try to be more judicious in my phrasing in the future.

There has been some interesting fallout from the Alien Sun debunking I wrote last night.

I talked to Steve Majewski, the lead author on the horribly maligned scientific paper about the Sagittarius Dwarf galaxy. He thanks me for saving him the trouble of having to debunk the claim himself. He has updated his original page about all this with a disclaimer saying the Viewzone article is wrong, too.

But while we were talking, he pointed out that I made a mistake!

Before I go into details, let me add that the error I made does not in any way negate the facts that

1) The claim that the Sun came from a different galaxy is wrong, wrong, wrong, and
2) The Sun orbits the Milky Way smack dab along the MW’s disk plane. That one fact alone kills the alien Sun claim.

What I said was that the plane of Sag Dwarf stream was perpendicular to the Galactic center. Turns out that’s not right. I was basing this on a still frame from an animation based on the original data, showing the stream, the Milky Way, and the position of the Sun.

The problem was, I was seeing all that from one angle. I didn’t realize it was from an animation! Dr. Majewski pointed this out, so I looked at it. If, in fact, you freeze the movie at a different spot, you get another angle on the issue:

Interestingly, from this angle, you can see that coincidentally, the stream’s plane does, more or less, cut across the Galactic center. Also — though you can’t tell from the video — the plane of the solar system, while not aligned with the stream, isn’t hugely far off either from the plane of the stream, either (though not exact, of course).

However, and this is a big but, it doesn’t matter. It’s irrelevant. The key issue is that the Sun is well-known to orbit the MW center in the plane of the Galaxy’s disk, and therefore cannot be from the dwarf.

And I have to add: while looking at the animation, it’s also clear that where the stream intersects the MW disk is not right next to the Sun; it’s displaced a bit. Remember, that point of intersection is what started this whole thing.

AND, something I totally forgot to add in yesterday’s entry: the Sun is near that intersection point… now. But 50 million years ago (yesterday in terms of the Sun’s lifetime) the Sun was 90 degrees around the Milky Way from the stream! The Sun orbits the Galactic center every 200 million years or so. That means that right now, at this particular slice of time, we’re near the intersection of the dwarf’s stream and the Milky Way. but in a few million years we’ll be plenty far away. And over the 4.6 billion year lifetime of the Sun, we’ve passed in and out of that stream probably many times as the Sun has orbited the Milky Way.

So that’s another reason the Viewzone claim of the alien Sun is wrong. You can’t say, "Look at how close the stream is the Sun; we must be from that galaxy!" when 50 million years ago the Sun was tens of thousands of light years from the stream.

Fail.

So I will happily admit I made a mistake. It was a small one, and irrelevant (though if it were a big one I’d still admit it; that’s just the way I am). But in finding my own error I found two more reasons Viewzone is wrong. I wonder: will that article get retracted? Anyone wanna take bets?

Incidentally, this silliness has gotten national attention. Even Amanda Cogsdon was fooled by it (4:45 into that video). I left her a comment; we’ll see if she gets back to me.

Emily over at the Planetary Society blog has the Ninth Carnival of Space going. Give it a (space) shot.

Note: I generally don’t do a thorough debunking of pseudoscientific nonsense on the blog, and instead relegate that to the main site. But I decided to do this on the blog, knowing that more people would read it than if I put it on the main site and linked to it from the blog. So here it is. Bon appetit.

We’ve always assumed the Sun was born in the Milky Way, and has been here its whole life. Is it possible it was actually born in a different galaxy, and the Milky Way stole it?

Do we have (cue evil music)… an alien Sun?

No.

Oh, you want more info? Alrighty then, sit back. This’ll be fun.

Introduction

A website called Viewzone recently posted an article claiming that scientists have determined the Sun is not native to the Milky Way Galaxy, but instead was absorbed by the Milky Way while eating a smaller dwarf galaxy.

There’s just one eensy weensy problem with this: it’s totally wrong.

Here’s how the writer from Viewzone sets this up; I have synopsized but kept his argument intact:

1) The Milky Way is eating a smaller galaxy, called the Sagittarius Dwarf galaxy.

2) Because this galaxy has far less mass than our own, the Milky Way has far stronger gravity. This has destroyed the other galaxy, turning it into a long stream of stars.

3) This stream is at an angle to the plane of the Milky Way’s disk, and intersects that disk.

4) The Sun is very near the position of this intersection. The odds of this happening are very low.

5) Therefore, the Sun originally came from the dwarf galaxy, and is not originally from the Milky Way.

I’m not exaggerating their claim at all. They make it very clear, saying:

We actually belong to the Sagittarius Dwarf galaxy.

As with most pseudoscientific claims, this one has some truth to it. The Milky Way is indeed cannibalizing another, smaller galaxy. The MW is bigger, and so its gravity did rip the smaller galaxy up, turning into a long ribbon or stream of stars. It does intersect the MW, and the Sun is in fact near this intersection point.

But their conclusion — that we come from the Sagittarius Dwarf — is complete nonsense. Here’s why.

The Plane Truth

First: look at the illustration created by the scientists who discovered the dwarf (click for higher res).

The Milky Way is the blue spiral, the dwarf galaxy is the red stream, and the Sun’s position is marked by the yellow dot. See how the dwarf galaxy is tilted with respect to the Milky Way? That means that all the stars from that galaxy are orbiting the Milky Way at that angle. So if the Sun came from the dwarf, we’d be orbiting the Milky Way at that angle ourselves!

We’re not. Studies of the Sun’s motion relative to the plane of the Milky Way (using the stars, globular clusters, other galaxies, and many other sources) make it a rock-solid certainty that the Sun’s orbit is in fact in the plane of the Milky Way. It’s not plunging through the disk at a high angle at all. So right away we see that the claim that the Sun is alien to the Milky Way is complete rubbish.

Seriously, we’re done here. You can stop.

Oh, you want more? OK. Let’s continue the smackdown.

If you read the Viewzone article (or the original claim from a site called, interestingly, CureZone) you can see they don’t understand this angle issue at all! They do seem to get that the stream is at an angle to the Milky Way, but they also claim that this is why the plane of our solar system is at an angle to the Milky Way’s plane, which is a bizarre (and totally incorrect) idea.

First, the plane of the solar system (defined, really, by the plane of the Earth’s orbit) is tilted with respect to the Milky Way’s plane by about 60 degrees or so. But this is not a big deal; the Sun formed from a gas cloud 4.6 billion years ago, and any number of forces would have caused that cloud to collapse such that the plane of our solar system could be pointed any which way. There’s no reason to assume the two planes would align.

Second, the articles never actually make the case that the solar system is aligned with the angle of the Sagittarius dwarf stream! If the Sun came from that galaxy, and they make these claims about angles and planes, don’t you think they’d actually see if our solar system aligns with the dwarf galaxy? That should set off alarm bells in your head.

Anyway, by looking at the illustration I can see right away that the tilt of the solar system is not aligned with the dwarf galaxy’s star stream either. Note: this next part of the paragraph is difficult to describe, so feel free to skip it and go to the next paragraph. It’s incidental to the main point anyway. The plane of the dwarf stream is perpendicular to the direction toward the center of the Milky Way, while the solar system’s plane is pointed at the center of the Galaxy. In other words, at one point in Earth’s orbit, you can draw a line from the Earth through the Sun and it will pass very near the center of the Milky Way (if you were at the Galactic center, you’d see our solar system "edge-on"). If our solar system were aligned with the dwarf stream, that wouldn’t happen (from the Milky Way’s center, the solar system would appear to be "face-on"). That means we’re not aligned with either galaxy, and their claims about angles are bogus.

Look: the important thing to see here is that the angle of the Milky Way in the sky is not important at all. What counts is the Sun’s orbit around the center of the Milky Way. And the Sun’s orbit is aligned perfectly with the plane of the Milky Way, and not at all in the plane of the Sagittarius dwarf.

So again, we’re done.

But of course, I can always add more.

It does seem a coincidence that the Sun happens to be near the intersection point of the two galaxies. But look at the drawing: the stream from the dwarf galaxy is far, far larger than the Milky Way. If we belong to the dwarf galaxy, what are the odds that at this point in time we’d be almost exactly in the center of the plane of the Milky Way? A star in the dwarf stream would spend billions of years, going around the Milky Way, but only spend about a million years plunging through the Milky Way’s disk, and a fraction of that right at the midplane. The odds of us being precisely at the halfway point through the Milky Way’s disk just as this discovery is made are incredibly, ridiculously low. It makes a lot more sense if we are instead part of the Milky Way, and happen to be near where the two galaxies meet.

Conclusion: we’re native to the Milky Way.

Heavy Metal

One way to try to figure out if a star belongs to one population or another is to look at the chemical compositions involved. The Sun, for example, is known to have an above-average amount of iron in it, indicating that it’s a third-generation star. Most stars in the Milky Way have lower iron abundances, but some have more. However according to a paper on the composition of stars in the dwarf galaxy, the dwarf stars are much lower in iron than the Sun. If I am reading this paper correctly (it’s tough going, I’ll admit!) then it’s very unlikely just from this that the Sun came from the dwarf galaxy. It’s far more likely it was born right where we always thought: in the Milky Way.

Conclusion: we’re native to the Milky Way.

Artful Dodger

Also, I want to point out that the article on Viewzone is artfully constructed such that it sounds like the astronomers who wrote the original (and scientifically accurate) paper on the galaxy are agreeing (or at least supporting) with Viewzone’s (erroneous) conclusions. Quotations from real astronomers are interspersed with totally incorrect conclusions by the Viewzone article author.

Look at this from the Viewzone article:

On the other hand, Majewski and his colleagues have been surprised by the Earth’s proximity to a portion of the Sagittarius debris.

“For only a few percent of its 240 million-year orbit around the Milky Way galaxy does our Solar System pass through the path of Sagittarius debris,” Majewski said. “Remarkably, stars from Sagittarius are now raining down onto our present position in the Milky Way. Stars from an alien galaxy are relatively near us. We have to re-think our assumptions about the Milky Way galaxy to account for this contamination.”

Wow, that sounds like Majewski, the lead author of the scientific paper, agrees that the Sun must come from the dwarf galaxy, doesn’t it? Especially that last sentence. But he’s not really saying that at all. If you remove that last sentence about rethinking assumptions, he’s just commenting that it’s remarkable that we’re near the intersection point. Remarkable, but not mind-blowing. But the important part is that the last sentence is on another topic, the idea that we can’t assume that all nearby stars are native to the Milky Way. The vast majority are, to be sure (or else we would have discovered the interloping galaxy a long time ago), and astronomers will have to be careful when looking at individual stars. But he’s not commenting on the Sun at all.

To be fair, this is from the original press release. But the way it’s placed in the Viewzone article is misleading. It doesn’t support the Viewzone article’s premise at all.

Conclusion: don’t trust what the article says. But that’s true for anything.

Weird Stuff

I’m not a fan of attacking the messenger, but sometimes it pays to look at someone’s pedigree when they are making a huge claim like this. If they say the Sun comes from another galaxy, and also that Napolean talks to them through their houseplant, then you have to take the Sun claim with at least a modicum of salt.

Which brings me to this from the Viewzone article:

It has been postulated that this is the real reason for both global warming since higher energy levels of the Milky Way are almost certain to cause our Sun to burn hotter and emit higher energies. Indeed, temperatures have been seen to rise on virtually all the planets in our system. This seems quite apart from any local phenomenon like greenhouse gases etc.

Sigh. The warming of the outer planets is another bad idea. First, not every planet is warming — and saying "virtually all" is dead wrong — and the ones that are, if they are (it’s hard to tell), all have good reasons for doing so.

At least the ViewZone article author is in the good company of bonehead Fred Thompson.

Also, what are "higher energy levels of the Milky Way"? This vague term is never explained… and I know why: it’s meaningless. What energy levels? Kinetic energy? Gravitational energy? I suspect they mean "energy" in the meaningless New Age sense, given the very next paragraph:

This grand turning is possibly the root cause for the discontinuation of the Mayan calendar (the most accurate on the planet) because the ‘read-point’ of the Pleiades star cluster, which many believe the calendar was based upon, can no longer be a constant as we begin to steer away from the earlier predictable movements.

The Mayan calendar is the most accurate on the planet? That will surprise most astronomers, who have things timed to fractions of a millisecond.

Invoking the Mayans when discussing galactic interactions is a little, um, odd. The term "non-sequitur" seems inadequate. "Goofy" might be a better word.

Incidentally, the original article on CureZone, on which the Viewazone article is based, is a total mishmash of gobbledygook. The opening headline is:

New Discovery Evidencing Solar System Traveling Different Direction To Milky Way Substantiates Astounding New Theories — Coming To Be Called The 3 Most Pivotal Discoveries Of Our Time…

Anyone who says their idea is ONE OF THE MOST PIVOTAL OF ALL TIME, well, they’ll score pretty high on the crackpot index. That doesn’t mean they are a crank, of course. But it sure helps.

And the headline is certainly wrong — the solar system is traveling quite nicely around the center of the Milky Way in the plane of the disk, as I hammered home above.

Conclusion: The article is strongly suspect as to its accuracy.

Wrap Up

This kind of stuff comes and goes. Mostly goes, which is good. It’s silly pseudoscience of the highest order: all of the evidence points to the Sun being a native of the Milky Way (a native Sun! Bwahahahahahaha!). But someone sees a scientific article, doesn’t do any real research, jumps to any number of bad conclusions, ignores obvious refuting evidence, and then wraps up the nonsense in scientific-sounding jargon.

This particular silliness got a degree of success because it did well at Digg.com. But it’ll go away, just like all other silly claims. Well, not all others; more’s the pity. But I’ll keep at ‘em.

So if you hear someone claim that the Sun is not from around here, you know where to point them. There’s a reason I gave my website the name I did.

Tip o’ the sun visor to the bazillion folks who kindly sent me emails about this stuff!