Blogs / Bad Astronomy

I’ve been posting sporadically on how sunspots are starting to come back to the Sun, and I’m glad to see a new group sprouted up recently… and it’s a monster:

These images are from SOHO, the Solar and Heliospheric Observatory. The orange one is in visible light, and the sunspots are pretty obvious. The green one shows the Sun in the far ultraviolet, and you can see the sunspots are pretty intense, blasting out high-energy light. Sunspots are indicators of magnetic activity, and the intense magnetic field can accelerate plasma (ionized gas) to high energies.

Just so’s you know, a hundred Earths could fit across this image, so that oughta give you an idea of just how big these blemishes are.

What this means is that the Sun is becoming active again. You can see it better in this video I put together using SOHO animations. These are real SOHO observations. Note that some of the data are missing so the Sun’s rotation is a bit jerky, and that you can see that data dropouts and other problems plague these sort of observations. Oh– actually, another group popped up on the Sun earlier, too, and you can see those in the visible light data.

You can actually see the plasma flowing along the magnetic field lines in the latter part of the video.

Right now, the Sun is struggling to climb back up to the peak of its magnetic cycle, which will probably occur in 2013 or later, given how slow this has been — which you might want to keep in mind if some crackpot or scammer is trying to sell you on the idea that solar activity will destroy the Earth in 2012. When the Sun is at its peak, the magnetic field is at its strongest, and we see the most sunspots. However, the strongest solar flares and other explosive events tend not to happen until well after the cycle peaks, so it’ll be late 2013 or 2014 before we see the most vigorous activity, if the Sun holds to its previous behavior.

Again, people selling you on 2012 disasters generally have a very tenuous grasp on science. The less you know the better for them.

I expect we’ll be seeing more and more sunspots now as time goes by. It’s nice to see this happening, as it adds to the activity seen in December, and ends a long period of minimal sunspots — heck, for a long time, there were none at all. Boring. Now we can look forward to some exciting action again… just in time for SDO to launch, too!

[P.S. If anyone can tell me why the first few frames of my uploaded videos turn gray sometimes, that would be nice. I don't know whether to curse iMovie, Flash, YouTube, or all three.]

Image credit: SOHO (ESA and NASA)

The Solar Dynamics Observatory, due for launch on February 9 at 10:30 Eastern time (15:30 GMT), is a revolution in solar observing: equipped with state-of-the art detectors, it’ll stare at the Sun and teach us far more about our closest star than we’ve ever had a chance to before. It’s like SOHO on steroids.

I was going to write up a lengthy post about it, but then I found out my friend Nicole Gravitationaliotta, aka The Noisy Astronomer, already put together a great post about it. That saves me time.

Something I want to point out: SDO will have a continuous science data streamrate of a whopping 16 megabytes per second. You might want to read that again. That’s 1.4 terabytes per day, or half a petabyte per year. Given that a Blu-Ray disk holds 50 gigabytes at most, that means SDO would fill 28 disks a day just to store that data. Cripes. That’s a vast amount of data to sift through. If the Sun is hiding anything, it has about a week to figure out what to do. After that we’ll be watching everything it does.

Also, a fun thing about this for me is that the project scientist for SDO is Barbara Thompson, a woman I’ve known a long, long time: her office was across from mine when I was working on Hubble, and I would often drop by to swap stories with her and generally mix it up. It’s very cool to know that an old friend will be helping run such a fantastic astronomical instrument.

Pity poor Pluto. The debate over its planethood has caused much consternation over the years. Part of the problem is that it’s so dinky and so far away! If it were closer, or bigger, we almost certainly wouldn’t be having this debate.

But whether or not you think Pluto should be part of the gang or not, one thing is certain: it’s a world unto itself. And to bring this point literally home, the Hubble Space Telescope has revealed the changing face of this tiny iceball:

These images, just released today (but taken in 2002), represent the most detailed surface map of Pluto ever taken. Even in Hubble’s Advanced Camera for Surveys Pluto is only a few pixels across, but it’s possible using sophisticated image processing techniques to tease out the detail seen.

Here’s a nifty animation of Pluto rotating using these maps:

Very cool. But these maps are more than just eye candy. They show significant changes on Pluto’s surface since the last maps were made using Hubble 16 years ago. Pluto’s north pole is brighter and the south pole darker, implying that material has migrated from one pole to the other, or at least that the poles are changing in different ways. Pluto orbits the Sun "on its side", dramatically more tilted than Earth’s mere 23.5°. Right now, the north pole of the world is facing the Sun, meaning it’s summer on Pluto’s northern hemisphere (as it’ll remain for a long time, given Pluto’s 248 Earth-year long year).

Not only that, these images show that Pluto has reddened quite a bit in the past few years. This is one reason it took so long to release the images; Marc Buie, the astronomer who took them, saw some things in the data that were difficult to understand, and wanted to make sure they were correct. These images are composites of pictures taken using a blue and a green filter. During the time these observations were made, in 2000 – 2002, Pluto got much darker in blue, which was unexpected. Pluto’s moon, Charon, did not get any bluer, indicating that the cause was something intrinsic to Pluto and not that something weird happened with Hubble.

So why is Pluto redder now? That’s not clear. In general, ultraviolet light from the Sun interacts with the chemicals on Pluto, creating reddish organic molecules; this is seen on lots of distant, icy objects in the Kuiper Belt (the region past Neptune where Pluto orbits). Incredibly, even at the numbing distance of over 4 billion kilometers (3 billion miles) from the Sun, Pluto is still strongly affected by it. But this is happening while overall the northern hemisphere got brighter and the southern darker. You’d expect Pluto to get darker if it gets redder, so clearly there’s more going on here than meets the eye.

These maps will prove crucial in planning the imaging run of the New Horizons probe, which will scream past Pluto in 2015. Having even a crude map in advance of the encounter will help scientists plan their limited time more carefully.

Plus, these Hubble images may very well be the best view we’ll get until New Horizons gets to Pluto, for that matter. And whether you think Pluto is the littlest planet or one of the biggest of the Kuiper Belt Objects, it’s a fascinating place worthy of a lot more study. And in just a little more than five years we’ll see fantastic images of it, too. I can’t wait!

Video courtesy Emily Lakdawalla (and my thanks to her for a helpful conversation). Image and video credit: NASA, ESA, and M. Buie (SwRI)

Apropos of my recent post showing a Hubble image of two asteroids colliding, the website Word Spy just happened to have a funny choice for their word of the day: cosmophobia, "the strong and irrational fear that in the near future the earth will be destroyed by some cosmic event."

Personally, I figured it’s really for people who don’t like vodka, triple sec, cranberry and lime juice all mixed together, which is silly. Unless it’s headed for you at 30 km/sec. Because that’ll give you a pretty wicked hangover.

What’s better than a gorgeously stunning image of a massive cluster surrounded by delicate, wispy nebulosity?

Well, nothing, really. Unless you can use it for SCIENCE!

[Click to gigantisize.]

Purty, ain’t it? That’s NGC 3603, a very large star-forming region in our own Milky Way Galaxy, lying about 20,000 light years away. It can only be seen from the southern hemisphere, which is why the European Southern Observatory folks got this image using the ginormous Very Large Telescope, an 8-meter behemoth in Chile (and actually, Ginormous Telescope would be a cool name).

Not too long ago — no more than a million years, give or take — a lot of the stars forming the central cluster there were born. There are so many that they appear to overlap, but that’s an illusion due to the blurring of the image from the Earth’s atmosphere (and the nature of light itself only allows us to make star images so small).

Lost in that crowd is a star designated NGC 3603 A1, and it is the most massive star to ever have its mass directly measured. It’s actually a binary star, two monsters locked in a gravitational dance, orbiting each other once every 3.77 days — which right away tells you this is a special pair, possessing enough gravity to toss themselves around that rapidly.

Using simple laws of physics discovered by Kepler back in the 1600s, we can measure the masses of each star in the duo. The heftier of the two is a whopping 116 times the mass of the Sun — which is close to the upper limit of what a star can get to without tearing itself apart. The more massive a star, the more luminous it is, and the surface can get so hot that any material there gets blown off… so that sets a lid on how big a star can get. Details vary depending on a lot of factors, but really 116 times the mass of the Sun is about as big as you’ll ever get for a star in our galaxy.

The other star in the binary is no slouch, tipping the scales at 89 solar masses. If it were just sitting out there all by itself it would rate as a phenomenal star, too. But its partner still wins the prize.

And how do I know those stars were born no more than a million years ago? Because massive stars don’t live long, and any beasts like these two live short lives indeed. It won’t be long before they detonate as supernovae, lighting up with a violence and fury that will make each outshine the rest of the stars in our entire galaxy combined!

Not only that, but pretty much every star you see in that cluster is of the massive and luminous classes astronomers call O and B stars, bruisers with enough oomph to explode as supernovae. How many stars do you see in that cluster? Dozens? So think about that: each one of those will become a titanic supernova, wreaking havoc across dozens of light years, sending out blasts of light to outshine galaxies, and throwing out octillions of tons of gas.

Eventually that gas, laced with heavier elements created in the nuclear forge of the supernova blast wave itself, will slam into, merge with, and seed the surrounding gas in the nebula. Compressed beyond its ability to sustain itself, the gas will collapse and form more stars. Some of these may be massive ones which will again repeat the cycle, and some will have lower mass, be fainter, cooler. They may form planets from those heavy elements. It will be a rocky birth, given the environment, but the vagaries of orbital dynamics dictate that eventually those systems will leave the nebula and move out on their own in the Milky Way. And a billion years from now, two, four billion, who knows what creatures may roam the surfaces of any of those worlds.

And will they see more stellar factories dotting the galaxies starscape, and wonder what their own looked like, all those eons ago?

Last week, the Lincoln Near-Earth Asteroid Research (LINEAR) sky survey program, designed to sweep the heavens looking for near-Earth asteroids, spotted something really weird; an elongated streak that looked as if two asteroids had collided. Just days later, Hubble was pointed at the object, and what it saw was really really weird:

[Click to armageddonate.]

This is a false-color image showing the object, called P/2010 A2, in visible light. The long tail of debris is obvious; this is probably dust being blown back by the solar wind, similar to the way a comet’s tail is blown back. What apparently has happened is that two small, previously-undiscovered asteroids collided, impacting with a speed of at least 5 km/sec (and possibly faster). The energy in such a collision is like setting off a nuclear bomb, or actually many nuclear bombs! The asteroids shattered, and much of the debris expanded outward as pulverized dust.

Now, let me just take a moment and say HOLY HALEAKALA WHAT WE’RE SEEING HERE IS THE COLLISION BETWEEN TWO PREVIOUSLY UNDISCOVERED ASTEROIDS THAT EXPLODED LIKE THERMONUCLEAR WEAPONS WHEN THEY IMPACTED!!!

Phew. OK, I feel better. I needed to get that off my chest.

First off, to be clear we’re in no danger from this event. It was really far away (in human terms; 140 million km or 90 million miles — the object’s orbit keeps it farther from the Sun than Mars — so we’re not about to get pummeled with debris. And while the explosion energy was quite large — certainly much larger than any weapon ever detonated on Earth — it wasn’t radioactive, in case you’re worried about that sort of thing. This was a kinetic explosion, caused by a high-speed collision, and not an actual detonation of any kind.

Looking at the image, the bright spot to the left is most likely what’s left of one of the two asteroids, a chunk of rock estimated to be a mere 140 meters (450 feet) across. In the press release they’re not clear about the curved line emanating to the right of the nucleus. It may be — and I’m spitballing here — dust blown back from a stream of chunks, since the tail is broad and appears to originate from that swept curve, and not from the nucleus itself. The other filament perpendicular to the curve is from yet another piece of debris.

Despite how much this looks like a comet, ground-based observations indicate no gas is present, meaning this was from asteroids colliding, not comets, which have significant amounts of ice which turn to gas near the Sun. The collision energy was high enough to produce a lot of gas if any were present. That clinches this being an asteroid impact.

Also, the orbit of the object indicates it’s an asteroid, and it appears to be part of a well-known group of asteroids called the Flora family, which share similar orbital characteristics, and are probably remnants themselves of an ancient breakup of a much larger parent asteroid.

Nothing like this has ever been seen before. Sure, Hubble and about a hundred other telescopes observed the comet Shoemaker-Levy 9 slam in to Jupiter in 1994, but that was different than seeing two asteroids hit. Asteroids are small, and very very far apart on average (don’t believe scenes like that in "Empire Strikes Back"), so a collision like this is extremely rare, and catching it from such a great vantage point rarer still. But we have a lot of eyes on the sky, and the more we watch the more we’ll see.

And we’d better. An object 140 meters across hitting the Earth would, to be technical, suck. Hard. Whatever caused Meteor Crater in Arizona, an impact scar over a kilometer across, was itself probably about 40 meters across. An object like 2010 A2, which is three times the diameter, would have 20 -30 times the mass, and do considerably more damage. I’m glad groups like LINEAR are out there patrolling the skies for such things. We need to learn as much as we can about these asteroids, so that we can prevent the next Meteor Crater from occurring.

One of the closest and most spectacular galaxies in the sky is M51, the Whirlpool. A grand design face-on spiral with a small, irregular companion, it’s so bright and big that it’s a favorite target for amateurs. So you just know when you point Hubble at it, what you get is nothing short of jaw-dropping heart-aching beauty.

Voila:

[Click to galactify.]

This image, using the Hubble Advanced Camera for Surveys, was originally released in 2005, but was recently reprocessed by the phenomenal astrophotographer Robert Gendler. And yeah, you absolutely want to click that link to see the work Robert has done. He’s incredible.

I could go on and on about the galaxy, the glorious spiral arms, the red glow of nebular star birth factories, the odd companion that apparently has drawn out that long tidal tail of stars from the spiral, and so on… but you’ve read that stuff here before.

Instead, while looking this image up, I found the behind-the-scenes story on how they observed it that I think will interest you, my BABloggees. Extra cool is the page showing the galaxy observations in different colors, and you can see just what a big spiral looks like when you use different filters:

You can see the ACS field of view, and the final version on the left. The different observations are listed (each frame is clickable to embiggen on that page, which lets you explore the galaxy on your own). The filters are labeled on the top of each image: B (blue), V (visual, or really yellow), I (near-infrared), and Hα + [NII], the reddish light given off by hot hydrogen clouds laced with nitrogen. That last bit is where stars are being born, and traces the spiral arms very well. The I-band shows very warm dust as well as stars, so it looks smoother since all that stuff is rather smoothly distributed in the galaxy. The B-band has hot stars in it, so again shows where stars are being born; blue stars don’t live very long, and can barely escape their gas cloud nurseries before blowing up as supernovae.

When you put these all together you get the majesty of a spiral galaxy, a city of stars much like our own Milky Way. I’ve seen M51 myself with binoculars and through countless telescopes at star parties, and while it doesn’t look as glorious as it does here — of course — just knowing what’s going on in the galaxy and what it really does look like through the big guns is enough to thrill. It may look blurry and fuzzy through a small telescope, but our brains are big enough to encompass all those light years, and to understand what it is we’re seeing.

Image Credit: NASA, Hubble Heritage Team, (STScI/AURA), ESA, S. Beckwith (STScI). Additional Processing: Robert Gendler