Blogs / Bad Astronomy

GRB080319b, the explosion that shook astronomers by getting bright enough to be seen with the naked eye, is still going strong. Hubble snapped this image three weeks after the explosion:

Incredibly, even after that time the GRB afterglow is still brighter than its host galaxy! This was truly an incredible event. I imagine any potential aliens in that galaxy — at least between us and the burst — are just so much vapor now. Of course, you can think of this event as having happened 7.5 billion years ago, so it’s unlikely that there are any alien civilizations around to be destroyed (as I mentioned in an earlier post, heavy metals were rarer back then, so planets would probably have been deficient in elements like iron, calcium, zinc, and so on). Maybe whole planets-full of microbes were zapped, though.

GRBs emit their light in beams like a flashlight, which is why they are so bright even from so maddeningly far away. But this one was so bright that astronomers were at first a little baffled. Was this really an astonishingly luminous event, or did the beam from the GRB happen to be perfectly aimed at us? Did it hit a bulls-eye?

In fact, it’s thought that this truly was an incredibly luminous event intrinsically, and that was due to the beam being unusually tightly focused. It also was aimed right at us, making it look even brighter.

What’s fun to think about is how many other GRBs have been like this one? Probably not many, actually, so it was good for us that we happened to have the Swift satellite operating when the GRB went off. That allowed us to observe the explosion in near real-time with bigger and more sensitive telescopes, and in turn learn more about these incredible explosions on the dim edge of the Universe.

And I’ll add that this couldn’t have happened at a better time for me: I was able to edit the proofs of my book to include GRB 080319b! I had talked about an earlier burst originally, but substituted this one in for it. I’m glad the timing worked out so well.

The web has been buzzing over what everyone is calling the smallest extrasolar planet found, weighing in at about 5 times the mass of the Earth.

Problem is, that’s not the smallest exoplanet found, not by a long shot. That record is still held by three planets massing 0.02, 3.9, and 4.3 times the Earth’s mass, orbiting the pulsar PSR B1257+12.

This newly found planet, orbiting the red dwarf GJ436, is the smallest yet found orbiting a Sun-like star.

I’m not picking nits here. I’m trying to be careful. The news tends to focus on planets found orbiting stars like the Sun (that is, fusing hydrogen in their cores as the Sun does) because those planets are the ones in environments most like ours. Certainly, those ones resonate with us, because one of the goals of this search is to find not only a planet with roughly the same mass as Earth, but one on which the conditions may be ripe for life to form and evolve.

Trust me, I’m all for that! I’m excited, terribly excited, about this search. I was a part of it, briefly, years ago, and it means a lot to me. But I’m also an astronomer, and I think it’s important to remember that not only were terrestrial-massed planets found first, they were found a full three years before any other exoplanets were found orbiting Sun-like stars.

Pulsars are dead stars, the collapsed cores of massive stars that exploded. The three planets in the system found in 1990 are probably nothing like Earth; they either existed before their star went supernovae, in which case they got fried but good, or they accreted after the explosion and formed under very weird conditions that make them exotic. Either way, they’re damn odd (to quote Kirk), and so they don’t work their way into our minds as well as more familiar planets.

But still, their discovery was a huge advance in astronomy! Who could have thought planets could either survive, or form after, something as devastating and titanic as the explosion of an entire star? It rocked astronomy when they were found, and their existence is still something of a mystery. How did they get there? What are they like? What does a planet look like when it’s baked by intense X-rays and particle radiation for thousands of years?

I don’t mean to detract from either the search for exoplanets around Sun-like stars (again, big supporter of it) or people writing up the news of such (obviously, also a big supporter). I just want to make sure the record is clear. It pays not to gloss over details sometimes, because in many cases that’s where the real treasure and real wonder lies. I don’t want folks to forget our prejudice toward Earth-like (or solar system-like) planets, when the exotic and bizarre might get overlooked.

Yeah, not what you thought, eh? But still… pretty.

Spitzer Space Telescope caught this image of the cluster Omega Centauri, which I recently wrote about.

Whether Omega Cen is a galaxy or a globular cluster doesn’t change the fact that this is a striking image. It’s actually a combo of Spitzer and ground-based images taken with a 4-meter telescope in Chile. Stars shown here as blue (more on that in a sec) are low-mass stars seen in both the 4-meter ’scope and Spitzer. Yellow and red stars were seen only by Spitzer. Since it looks in the infrared, that means these stars are probably more evolved.

Why?

Clusters (or galaxies) like Omega Cen form pretty much all at once, using up all their gas to make stars. Since high-mass stars age more rapidly, and clusters like this are old, all the more massive stars have already either blown up (if they were massive enough) leaving behind black holes or neutron stars, or have long since turned into red giants and blown off their outer layers. That leaves behind a very faint white dwarf.

Omega Cen is very old, so only lower mass stars are still around, but even they have evolved into red giants. Those stars tend to emit more light in the infrared, both due to their low temperature as well as blowing off lots of dust, which enshrouds them and reddens their light. In fact, these images were taken to investigate how much dust these stars are generating. Fewer dusty stars were found than expected, which is interesting. Clusters like this tend to have lower metals (the term astronomers use for anything on the periodic table heavier than helium) because they formed early in the Universe, before massive stars could make those heavy elements and seed them into space. Could this lack of metals affect the dust formation? Images like this one can lead us to those answers.

By the way, in Omega Cen the lowest mass stars are still going strong. Ironically, in this false-color image, those stars are colored blue (meaning visible light), but if you looked at them with your eye they’d look orange or red. False color images can be tricky, and in this case things are really topsy-turvy.

But it sure is a pretty picture.

So next week I fly to Jolly Old to begin an adventure which includes going down to the bowels of the Earth and poking around the Large Hadron Collider. No hadrons will be harmed during this trip, but I will be making videos with the officially sexy scientist Brian Cox, his unofficially sexy wife Gia, and a few others.

We figured, why not take a chance to meet up with folks in England in a pub? And so we will: on April 17th, from 6:30 to 10:30, we will glom onto a Nature.com meetup and use it to meet BA fans and others from the UK! The details are all online.

But wait, there’s more: James Randi hisself will be joining us! He’ll be in England on unrelated business, but seeing as how I was sitting next to him yesterday while he’s here in Boulder, I asked if he could join us, and he said yes.

W00t!

So here’s your chance to meet quite a few science and skeptic types. Unfortunately, we’re not sure if Brian can be there or not, but don’t let that stop you (he’s married anyway, remember?).

While I’m there, I’ll be doing some other things as well, but we’re not set in stone on what yet. I’ll have more info on all that as it solidifies.

Astronomers have found the coldest (well, least hot) brown dwarf in deep space: by the name of CFBDS J005910.83-011401.3, it has a temperature of 350 Celsius (660 Fahrenheit). That’s still hotter than you need to bake cookies, but compared to a star it’s practically frigid.

Now we should be careful with our semantics here. Planets have been detected around other stars which may be lower in temperature than this object, I suspect, but their temperatures have not been directly determined. In the case of CFBDSetc., the temperature was found by looking at its spectrum. The presence of ammonia in the atmosphere of this object was a dead giveaway that it’s cold; ammonia breaks apart when it gets too hot. Other features allow a temperature to be found, and 350 C is pretty cool. Other brown dwarfs are hotter, more like in the 1000 C range or so. The warmer an object, the brighter it glows, and the easier it is to find. So warmer ones are found first, and cooler ones are tougher.

Brown dwarfs are weird. They’re objects with masses between that of a planet and a star, and the first were found just a few years ago. They are more massive than planets — CFSBD is 15 - 30 times the mass of Jupiter — but still far less massive than a star, and cannot continuously fuse hydrogen to helium in their cores. The ones we find tend to be young and still hot from their formation. Eventually they cool off, since they cannot generate heat in their cores as stars do. Obviously, CFSBD has been around the block a few times to have had enough time to cool down so much. That alone makes it interesting.

But since it’s so cool, its atmosphere is more like a planet than a star. Getting direct observations of a planet around another star is incredibly difficult, so studying this weird object will no doubt generate insight into planetary atmospheres with temperatures intermediate between what we see here in our solar system and brown dwarfs we detect out in space.

And now that we’ve found one, I’ll just bet more will pop up in the next few years. Once we have enough to get statistics on them, our knowledge will increase rapidly, just as it did when brown dwarfs were discovered in the first place.

Funny– as I write this, it’s snowing outside. Cold is relative, I suppose, but one thing I like about new discoveries is how they stretch our minds just a little bit, and make us re-evaluate what we mean by things like "hot" and "cold". I’ll still put on a coat and gloves when I go outside in a few minutes, but in my mind I’ll wonder what it’s like to walk across Mars, where it’s so much colder, or Mercury, where it’s a tad bit warmer. And what would it look like to hover over a brown dwarf, orbiting an object that’s the physical size of Jupiter, but is neither a planet nor a star? What odd weather patterns would paint the view?

The Universe is weird. I’m glad we get the chance to take a look around.

Craving a little doubt in your life? Check out the 84th edition of the Skeptics’ Circle of blog posts, hosted at Archaeoporn. As usual in such blog carnivals, there’s a lot of stuff to keep you reading when your boss isn’t looking. Since I work at home, my boss is never looking. Which is good, because sometimes I’m not wearing pants.

Wow: New Scientist is reporting that scientists have created a laser that pound for pound is the brightest light source in the Universe.

It’s a petawatt laser, which is incredibly powerful (one petawatt is 1000 terawatts; peta is a prefix people will get to know in a year or two once terabyte drives prove too small to store very many illegally downloaded BluRay movies). The light of the laser is sent out in a very brief pulse, which has all that energy packed into it. So it’s short-duration, but incredibly bright. It’s actually got more intensity (energy per square centimeter) crammed into the pulse than a gamma-ray burst beam, which is insanely powerful.

This sort of thing has lots of uses in astronomy, oddly. It creates so much energy that it can be used to model what happens when a lot of energy slams into matter as it does in a supernova or GRB. It’s not well-understood what happens when matter absorbs energy on that scale, so it will be a useful test on theories.

Plus, it’s just cool. Chris Knight would be proud.

Tip o’ the heavily shielded goggles to BABloggee Dave, Just Dave.