Drive-By Blogging 2: Blogs in Space

I’ve come across lots of interesting space-related items in the past few weeks (er, months), but I’ve been too busy or too preoccupied with other matters to mention any of them here, so I think it’s time for another exciting installment of… Drive-By Blogging!

(I’m thinking of turning this into a regular feature here at Simple Tricks, by the way. It seems like there are always many more items that I want to comment on than I ever manage to actually devote entire entries to. Sigh…)

  • The big news of recent weeks was, of course, the announcement that European scientists have found the first known Earth-like planet orbiting another star. Earth-like is a somewhat relative term in this case; the planet in question is thought to be 1.5 times the size of our world and five times more massive, with a correspondingly stronger gravity field. Also, it makes a complete circle around its star in only 13 Earth days, and there’s a good chance that it is “tidally locked,” meaning it always shows only one face to its star the way our Moon shows only one side to Earth. However, the models show that it’s most likely rocky or covered in oceans like Earth, and — here’s the exciting part — it orbits inside what is called the “habitable zone.” In other words, the average surface temperature is estimated to fall within a range where water would be liquid. And where there’s liquid water, there’s a good chance for life.
    As the Bad Astronomer points out, we have no idea what the atmosphere of this world might be like, and we don’t know for sure that there’s any water there. But there could be, the first time we’ve seen this possibility, and that’s immensely exciting. The planet is one of three known worlds in orbit around a star called Gliese 581, a red dwarf some 20 light years from Earth. (For my non-geeky friends, that means it would take us 20 years to get there, travelling at the speed of light. If we could travel at the speed of light, that is. Where’s the Millenium Falcon when you need it?)
  • It only took a couple of days for some artistically inclined individual to try imagining what the surface of Gliese 581c might look like, and it’s something else: very alien but very beautiful. The idea behind this painting is that the star Gliese 581 is very active, with lots of surface granularity and solar flare activity, which is, in turn, generating the equivalent of northern lights in the planet’s atmosphere. Wouldn’t you love to be in a boat on this ocean, watching this sunset?
  • And speaking of alien sunsets, a recent article announced that scientists now think that planets around binary stars — that is, two stars in the same system — are at least as common as they are around single stars like our own sun. Moreover, habitable planets in binary systems are not out of the question. The story I linked to includes an artist’s conception of a sunset seen from such a planet. To my great pleasure, it’s a familiar sight.
  • A little closer to home and several months back, the plucky Martian rover Opportunity captured some nifty photos of wintertime clouds passing overhead. NASA then stitched them into a mesmerizing little movie. An explanation of what you’re seeing can be found here.
  • Researchers from the Jet Propulsion Laboratory (with help from the Planetary Society) have tracked down a complete set of recorded telemetry data from the Pioneer 10 and 11 probes and are now transferring all that information to a modern digital format. They’re hoping that once the data is ready for analysis, they’ll be able to figure out what’s causing the so-called “Pioneer Anomaly,” the mysterious force that seems to be slowing the two spacecraft as they cruise toward interstellar space. One interesting idea is that particles from the probes’ own nuclear power plants may be striking their main antennae and acting like a solar sail.
    [Ed. note: I first wrote about the Pioneer Anomaly here.]
  • The New Horizons space probe, currently outbound for Pluto, passed by Jupiter recently and captured many awesome images, including a volcanic eruption on the Jovian moon Io, and a lovely pic of the moons Io and Europa together, receding into the distance as NH continued on its way. Relevant blog entries describing these images are here and here.
  • Another spacecraft, the European Space Agency’s Rosetta, passed very close to Mars during its complicated back-and-forth course to rendezvous with comet 67P/Churyumov-Gerasimenko, and took this amazing photo of the planet’s surface framed by the probe’s own solar array and hull. As seems to happen so very often, this real-life image reminded me of something from my youthful fantasy life, namely a shot from the original Battlestar Galactica series which depicted the Mineral Ship moving into position over the planet Carillon. (Naturally, I couldn’t find a photo or video clip, but trust me, the Rosetta photo looks just like the scene I’m thinking of.) An explanation of the Rosetta shot and more pics can be found here.
  • Remember that prototype inflatable space hotel I’ve mentioned before (here and here), the Genesis 1? Here is a pretty detailed article about what’s been going on with it and how Bigelow Aerospace is coming on its successor, Genesis 2. The short version: Bigelow hopes to launch Genesis 2, the second prototype, very soon, with the larger Galaxy module to follow in 2008 and the habitable Sundancer module in orbit by 2010. That vacation in space is coming, kids!
  • But if you can’t wait for Bigelow, you could always try taking a ride on a “vomit comet” like astrophysicist Stephen Hawking did last week. For a mere $3,500, Zero Gravity Corporation will take you up on a Boeing 727 that goes through a series of extremely sharp climbs and dives. When the plane noses over to start its dive, you’ll experience a brief period of weightlessness, just like the astronauts. I imagine that it must’ve been heavenly for Hawking, who has been paralyzed for 40 years by Lou Gehrig’s disease, to be free of gravity’s bonds for even a few brief moments.
  • And finally, an item that doesn’t have a lot to do with space but nevertheless amused me: Queen Elizabeth plans to visit NASA’s Goddard Space Flight Center this month while she’s in the US to commemorate the 400th anniversary of the founding of Jamestown. Here’s what I wonder: Is this simply some kind of courtesy call arranged by the Queen’s people for some political reason I’ve not heard, or is she really a closet space buff? I think it would be really cool to think that this woman, who seems (with all due respect) like such an anachronism here in the 21st Century, is up on all the current explorations and efforts to get off this little rock…

And there you have it, all the space news that’s caught my eye recently. If you haven’t already, please follow those links — you’ll find a lot of fascinating stuff…

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3 comments on “Drive-By Blogging 2: Blogs in Space

  1. Cranky Robert

    Why are some bodies “tidally locked”?

  2. jason

    I don’t know for sure – I think it’s got something to do with the mass of the body that is orbited being larger than the mass of the orbiting body, and the distance between the two — but it is an interesting phenomenon that every moon in our system is so locked. In other words, the time it takes for them to rotate once (i.e., complete one of their “days”) also happens to be the amount of time it takes to complete an orbit (a “year”). Our moon, for example, is turning; it’s just that it takes the same amount of time to make one full turn that it does to circle the earth, one month.

  3. jason

    Duh… I should’ve known to consult the oracle of all knowledge (a.k.a. Wikipedia):

    The change in rotation rate necessary to tidally lock a body B to a larger body A is caused by the torque applied by A’s gravity on bulges it has induced on B by tidal forces.
    Tidal bulges: A’s gravity produces a tidal force on B which distorts its gravitational equilibrium shape slightly so that it becomes stretched along the axis oriented toward A, and conversely, is slightly compressed in the two perpendicular directions. These distortions are known as tidal bulges. When B is not yet tidally locked, the bulges travel over its surface, with one of the two “high” tidal bulges travelling close to the point where body A is overhead. For large astronomical bodies which are near-spherical due to self-gravitation, the tidal distortion produces a slightly prolate spheroid or ellipsoid. Smaller bodies also experience distortion, but this distortion is less regular.
    Bulge dragging: The material of B exerts resistance to this periodic reshaping caused by the tidal force. In effect, some time is required to reshape B to the gravitational equilibrium shape, by which time the forming bulges have already been carried some distance away from the A-B axis by B’s rotation. Seen from a vantage point in space, the points of maximum bulge extension are displaced from the axis oriented towards A. If B’s rotation period is shorter than its orbital period, the bulges are carried forward of the axis oriented towards A in the direction of rotation, whereas if B’s orbital period is shorter the bulges lag behind instead.
    Resulting torque: Since the bulges are now displaced from the A-B axis, A’s gravitational pull on the mass in them exerts a torque on B. The torque on the A-facing bulge acts to bring B’s rotation in line with its orbital period, while the “back” bulge which faces away from A acts in the opposite sense. However, the bulge on the A-facing side is closer to A than the back bulge by a distance of approximately B’s diameter, and so experiences a slightly stronger gravitational force and torque. The net resulting torque from both bulges, then, is always in the direction which acts to synchronise B’s rotation with its orbital period, leading eventually to tidal locking.
    Orbital changes: The angular momentum of the whole A-B system is conserved in this process, so that when B slows down and loses rotational angular momentum, its orbital angular momentum is boosted by a similar amount (there are also some smaller effects on A’s rotation). This results in a raising of B’s orbit about A in tandem with its rotational slowdown. For the other case where B starts off rotating too slowly, tidal locking both speeds up its rotation, and lowers its orbit.
    Locking of the larger body: The tidal locking effect is also experienced by the larger body A, but at a slower rate because B’s gravitational effect is weaker due to B’s smaller size. For example, the Earth’s rotation is gradually slowing down because of the Moon, by an amount that becomes noticeable over geological time in some fossils. For similar sized bodies the effect may be of comparable size for both, and both may become tidally locked to each other. The dwarf planet Pluto and its satellite Charon are good examples of this— Charon is only visible from one hemisphere of Pluto.

    Clear as mud?