Archive for September, 2009

campaign mode

September 21st, 2009 1 comment

Full-resolution Poster-sized .pdf of the above.

The next HD 80606 transit is coming up this week. While the sky position of the star will be much more favorable during the coming January event, observers across the US have an opportunity to get photometric measurements of the ingress early Thursday morning.

The transit begins just after 11 AM UT on Sept. 24, and will unfold over the next 12 hours, meaning that observers in Japan and East Asia will be able to catch the egress.

Josh Winn of MIT is organizing a repeat of the successful June campaign (detailed in this post). If you’re a capable photometric observer, and if you’re interested in participating in the campaign, definitely get in touch with him.

intellects vast and cool and unsympathetic

September 21st, 2009 1 comment

I was jazzed to learn that the recent spate of saucer-themed Google “doodles” and coded messages were a tip of the hat to H. G. Wells. From the Google blog:

Now, we’re finally acknowledging the reason for the doodles with an official nod to Herbert George, who would be 143 years old today.

Inspiration for innovation in technology and design can come from lots of places; we wanted to celebrate H.G. Wells as an author who encouraged fantastical thinking about what is possible, on this planet and beyond. And maybe have some fun while we were doing it.

I’ve always thought that it would be almost impossible to improve upon the first paragraph of War of The Worlds:

No one would have believed in the last years of the nineteenth century that this world was being watched keenly and closely by intelligences greater than man’s and yet as mortal as his own; that as men busied themselves about their various concerns they were scrutinised and studied, perhaps almost as narrowly as a man with a microscope might scrutinise the transient creatures that swarm and multiply in a drop of water. With infinite complacency men went to and fro over this globe about their little affairs, serene in their assurance of their empire over matter. It is possible that the infusoria under the microscope do the same. No one gave a thought to the older worlds of space as sources of human danger, or thought of them only to dismiss the idea of life upon them as impossible or improbable. It is curious to recall some of the mental habits of those departed days. At most terrestrial men fancied there might be other men upon Mars, perhaps inferior to themselves and ready to welcome a missionary enterprise. Yet across the gulf of space, minds that are to our minds as ours are to those of the beasts that perish, intellects vast and cool and unsympathetic, regarded this earth with envious eyes, and slowly and surely drew their plans against us. And early in the twentieth century came the great disillusionment.

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Rings on the TV

September 14th, 2009 2 comments

Image: JPL/Cassini

Just a heads-up for those of you who haven’t yet firmed up your television viewing schedules for tomorrow night.

I’ll be appearing in a episode devoted to astrophysical disks (that is, rings) that’s set to air Tuesday night on the History Channel’s Universe series. Time is 9PM/8C. (Not sure when it goes down on the West Coast, “check your local listings”.)

The show delves into the ubiquity of disk-like structures in astrophysics, covering the range of scales from the band of our geosynchronous satellites to the rings of the Jovian planets all the way up to quasars and disk galaxies.

The swarm of satellites and space debris, including the ring of geosynchronous satellites (Source).

To create a visual analogy for Saturn’s rings, we visited a Pizza My Heart in Santa Cruz where they still hand-throw the pizza dough. I lecture about how the elastic forces in the spinning dough play a role similar to a the gravity of the central planet in providing inward centripetal acceleration. All the while, they’re throwing the dough in the background.

Throwing pizza dough to emulate an astrophysical disk.

Later, they got dramatic close-up footage of the spinning disks. There were were several moments when the spinning dough was severed azimuthally, causing the outer edge of the dough to go flying off at a tangent, narrowly missing camera and crew. I ad libbed that this is similar to what would happen with the ring particles if Saturn’s gravity could somehow be cut off.

Tune in to see whether it all bakes up as a credible piece of science popularization…

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Ups and Downs and Ups And

September 14th, 2009 Comments off

Visitors to may have noticed that the site was down for most of Sunday. I’d been neglecting to update my WordPress installation, which lead to a problem with the database, and a huge load spike for the server. Everything seems stable now, and I’m now flossin’ 2.8.4 inch rims.

In the relatively near future, I will be modernizing some aspects of the look and feel of the site, which will make it more discussion-friendly, and more smoothly slotted into the hum of the outside world. No need to worry, though. We’ll continue to roll ad-free.

I’ve updated the second systemic console tutorial which guides the user through the remarkable Upsilon Andromedae radial velocity data set. The back-end database is getting closer to its relaunch, and the systemic console (version 1.0.97) is freely available for download here.

Read on to work through the tutorial.

Read more…

Hot enough for ya?

September 7th, 2009 4 comments

A recent article in Nature reports that WASP-18b has emerged victorious in the ongoing exoplanetary limbo competition.

WASP-18b is also a strong contender in the least-habitable-planet-yet-detected competition. It has a mass roughly ten times Jupiter’s and skims 2.6 stellar radii above the surface of the parent star. The orbital period is a mere 22 hours 36 minutes. A year in less than a day.

To the offhand glance, even the simple presence of the planet seems puzzling. It’s so close to its parent star that tidal orbital decay should haul it in for destruction on a timescale that’s alarmingly short in comparison to the ~1 billion year age of the parent star. Either WASP-18b has been found on the very cusp of its dénouement (which seems unlikely) or tidal dissipation in the parent star is much lower than in a star like the Sun.

Darin Ragozzine pointed me to to a recent article by Barker and Ogilvie that indicates that WASP-18 may indeed be very poor at dissipating tidal energy. It’s an F-type star, somewhat more massive than the sun, with a negligible convective envelope, and no good recourse to turning tidal waves into heat. It’s like a bell that can ring and ring without making a sound. According to Barker and Ogilvie, similarly inviscid F-type parent stars are also responsible for the survival of WASP-12 and OGLE-TR-56b. Their prediction for WASP-18b would be that changes in the orbital period will not be observable, even with the excellent precision that will be obtained by timing the orbit over periods of a decade or more.

Darin also pointed out something else that’s pretty cool. As is also the case with HD 209458b and HD 189733b, the transit of WASP-18b is readily visible in the archived photometry from the Hipparcos mission. Indeed, the planet has been sitting in open view on the web for well over a decade, assuming, of course, that one knew exactly where to look. To see it with 20-20 hindsight, use the folding applet provided at the Hipparcos web site. Enter the Hipparcos catalog number (7562) for the parent star, and fold the 130 published photometric measurements at the 0.94145299 day orbital period. Can you see the transit?

On worlds like WASP-18b, surface temperatures are well in excess of 2000 K. Under such conditions, the ionization fraction is high enough that the planetary magnetic field can affect the weather.

On Earth, where air is composed of neutral atoms and molecules, the wind blows right through magnetic field lines. By contrast, on WASP-18b, the ionization fraction is high enough that the winds will have a tendency to drag the planetary magnetic field lines along. This stretches the field lines, and like rubber bands, they offer a restoring force. Whereas ordinary exoplanetary weather can be described using the equations of hydrodynamics, on an ultra-hot Jupiter, the richer behavior of magnetohydrodynamics comes into play. As a consequence, I have little intuitive sense of what’s going on at the sub-stellar point of WASP-18b, but I’ve got little doubt that it’s interesting and complicated.

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