By Mark Daymont
Published March 12, 2010
Two extremely dense stars in an intimate dance are spinning around each other in just 5.4 minutes—making them the fastest known stellar partners in the galaxy, astronomers have confirmed.
To have such a speedy orbit, the stars must be moving at about 310 miles (500 kilometers) a second, the team calculates.
The whirling duo, known as HM Cancri, also has the tightest orbit of any known "binary" star system. (Related: "First Proof 'Tight' Double Suns Can Have Planets.")
Both stars are white dwarfs—the dense, white-hot remnants left behind when sunlike stars die. The stellar corpses are separated by no more than three times the width of Earth.
In such tight quarters, hot gases flow between the two stars, releasing huge amounts of energy."This is the most extreme example of one of these double white dwarf systems we have so far," said study co-author Danny Steeghs of the University of Warwick in the U.K.
Published March 11, 2010
But a new look at Titan's insides reveals even more oddities: Beneath the brittle crust of ice lies a layer of slush. Deeper still is an underground ocean over a solid core of rock and ice.
This new picture is based on measurements of Titan's gravity field. The measurements were made by clocking the speed of the NASA-ESA Cassini orbiter with extreme precision—gaguing how many five-thousands of a millimeter the craft traveled per second.
"The ripples of Titan's gravity gently push and pull the spacecraft. By studying the velocity changes we can calculate the gravity," explained study leader Luciano Iess, of Sapienza University of Rome.
Subtle differences in Titan's pull on Cassini suggest that the materials inside the moon are a mix of ice and rock with no clearly defined rocky layers.
Titan's Icy Insides
Until now, scientists had thought Titan's interior would look a lot like the inside of Jupiter's moon Ganymede: Both bodies are large, have similar densities, and are made of roughly the same materials.
Under Ganymede's thin, icy crust lies a well-defined upper mantle of warmer ice, an inner mantle of silicate, and a molten iron core. (Related blog: "Comets 'Melted' Jupiter's Biggest Moon.")
But the new gravity data suggest that Titan and Ganymede had very different evolutionary histories.
"It is really quite a surprise, and it tells us that [Titan] never got hot enough to separate out into a core, mantle, and crust," said Ulrich Köhler of the German Aerospace Center in Berlin, who wasn't on the study team.
Instead, Iess and colleagues think that Titan's ice and rock remained together in a relatively lukewarm mixture.
This mixture took a leisurely million years or so to settle toward Titan's center—"plenty of time for heat to escape" and for the moon to cool into its present state, Iess said.
The team's calculations support the idea that Titan today has a subsurface liquid ocean from which methane bubbles up through an icy crust, constantly shrouding Titan in thick smog. (Related: "Methane Rain Formed New Lake on Saturn Moon.")
The study's notion of a relatively warm, spongy ice layer beneath a thin, hard outer shell would also explain Titan's lack of major mountains.
"Large mountains can't exist on Titan," Iess said. "They would simply sink into the ice."
Findings published in this week's issue of the journal Science.
The magnitude 8.8 quake in Chile this weekend apparently changed the length of the day — and shifted the way the Earth wobbles, according to scientists at NASA's Jet Propulsion Laboratory. Not that anyone noticed. Here's why scientists figure that the Earth changed the way it rotates: It turns out our planet doesn't spin like a perfect top; it actually wobbles a bit.
"The consequence of that is that the rotation pole actually moves, and it moves over the area about the size of a tennis court," says Richard O'Connell at Harvard University. This is called the Chandler wobble. And back in the mid 1970s, O'Connell wrote a paper that showed how big earthquakes keep kicking the Earth and by so doing keep the Earth wobbling.
The Earth's Wandering, Wobbly Axis
Now we know that earthquakes aren't alone in keeping that wobble going. It's also propelled by sloshing ocean waters and by huge air masses like typhoons. All this shifting around can also change the speed at which the Earth spins. And that of course affects the length of a day.
So how much difference can an enormous quake make? Scientists at the Jet Propulsion Laboratory figure that the shift caused by Saturday's quake in Chile should have shortened each day on Earth by about a millionth of a second. They also figure that the Earth's wobbly axis should have shifted by about 3 inches within that tennis-court-size area where it tends to wander.
But did it? It's Brian Luzum's job at the U.S. Naval Observatory to keep tabs on the Earth's rotation and orientation. And he says even the best instruments in the world can't measure a change in day length as small as a millionth of a second.
The Wobble Doesn't Show Up In Data
It is possible to measure the Earth's wobble pretty precisely. But considering how many things affect that wobble, it's hard to see the effect of the quake as well.
"So on a day-to-day basis, we actually will see changes on the order of 2 to 3 inches happening every day, and to try to pick out this signal in and among all the other signals, is just not really feasible," Luzum says.
The one hope was that the quake changed the wobble so abruptly that it would show up on the data.
"That's what you'd like to see to give you that eureka moment, but when we do look at the data, no such jump exists," Luzum says.
Theory says it happened, but the observations thus far aren't good enough to back that up.
Melting Ice Also Moved The Earth
But if these planetary effects are trivial on a day-to-day basis, they can really add up over geological time. Adam Maloof at Princeton University notes that ice has been melting over the past 12,000 years, as we come out of the last ice age. That's changing the Earth's orientation by about an inch, each and every year.
"You can imagine that as the ice melts you are redistributing the mass on the surface of the Earth," Maloof says. "So all this water that's caught up in the ice in poles is melting and moving into the oceans at lower latitudes."
And if you go way back in time — like to a period 800 million years ago — this kind of movement was dramatic. Over the course of a few million years, the land mass at the North Pole shifted monumentally: It slid south by 50 degrees.
"That's basically like taking Paris to the equator," Maloof says.
Nobody knows why this happened, though Maloof says one idea is that a huge volcanic plume, like the one that created the Hawaiian Islands, developed near one of the poles and that lopsided mass forced the Earth to rotate.
"It would have had major ramifications for sea level, climate, landscape, equilibrium, all sorts of effects like this," he says.
As for the effect of one quick catastrophic event: It's fair to say the Chilean quake touched hearts around the world more tangibly than it changed the spin of our planet.
I remember Julie well. She is an exceptional student and lifetime fan of the Space Center. She wrote this essay for her Honor's Inquire Class and sent it along to me to share.
I want to thank Julie for her kind words, and praise her for her goals and dedication to the exploration of Space. Space is the final frontier. It is our future. It draws us to it. You feel its appeal every time you step outside and stare into the night sky wondering what's out there and if they know we are here.
The Space Center does its part using science and science fiction to inspire people to dream big then achieve. The future begins in our imaginations. Our goals is to get those dreams and ideas out of our minds and into the real world using education and good old hard work.
And Now Julie's Essay...
Space = The Passion and Focus of My Life
Julie Anna Sanchez
Ever enchanted by the beauty of the sky, my life has taught me to dream of beyond. From some of my earliest memories of watching the stars at night, to the time when I discovered my passion, to my quest to become a rocket scientist, I have focused myself upon the deep beauties and mysteries that space holds for me.
I can remember that as I was growing up, my parents would take me out of the city to look at the sky where there is little light pollution to block out the stars. I was enchanted by the sky even then, and on long trips in the car at night, I would squish my head as close to the window as possible in order to watch the sky as we drove. I would look for shooting stars, and I always made a wish on the first star that I saw each night.
In my early childhood, I was able to visit the Hansen Planetarium in Salt Lake City. I loved watching the productions about the universe, and the museum upstairs was my favorite part of the experience because I was able to interact with science on a personal level. I have a natural ability to understand math and science. My parents tell me that I learned my multiplication tables when I was three years old; they were trying to teach them to my older brother and I just picked them up by watching them practice with him. Math and science were always my favorite subjects, and I couldn’t get enough of them.
In the fifth grade, my school was privileged to take a field trip to the Christa McAullife Space Education Center located in Pleasant Grove, Utah. The Space Center is a place where children are put into Star Trek type simulators and they set off on a “dangerous” mission. It is the most interactive learning environment I have ever seen; we learned about space, ethics, hard work, responsibility, current events, and teamwork all at once. I became enthralled with the Space Center and returned for summer camps and overnighters as often as time and money would allow. My experience as a 5th grade Damage Control Officer on the bridge of a starship was the turning point of my life. Before my visit to the space center, I was a nerdy child who liked math and science. After my visit to the space center, I was a gifted child whose life ambition was to do something in the space field. I had an outlet for all my hopes and dreams. I reached for the stars and the moon with the belief that one day I would touch them. I had found my passion.
Space rapidly became my focus, even approaching the level of an obsession. I watched, read, or viewed as much material as I could find about my chosen field as I possibly could. I watched Star Trek, read Isaac Asimov, researched space in Encyclopedias, and learned as much as I could about NASA. Many of my research papers for school had something to do with Space; I’ve written about Werner von Braun and the Russian Space Program. I got my own telescope for my birthday, and I started to find fascinating objects in the night sky.
I had begun researching space careers. Astronaut, astronomer, rocket scientist, and astrophysicist - I had so many choices. I gradually learned that some of these fields were not for me. I realized very soon into my explorations of space that I didn’t want to be an astronaut. However, I do want to build rockets, I want to work at mission control, and be in charge of an experiment or project in space. I want to be a part of the very large team of space explorers. Most people I meet never seem to understand this. When they learn of my love for all things in the heavens above, they immediately assume that my goal is to become an astronaut. When I tell them that I don’t actually want to be the one to journey into the beyond, but rather work on the project here below, they get confused or think that I’m a coward. People, it seems, can’t fathom the idea of a space nut who doesn’t want to be an astronaut. Yet, here I am. I dream of adventure, challenges, and marvels. For me, rocketry is the end, or beginning, of all my hopes and dreams.
I continued to attend the Space Center, finally achieving the rank of Fleet Admiral and becoming a member of the Order of the Federation. I also attended Astro Camp in Ogden, Utah and a telescope camp at the Clark Planetarium in Salt Lake City, Utah where I assembled my own telescope (a six inch Dobsonian Orion Telescope). I was able to visit the Marshall Space and Flight Center in Huntsville, Alabama, and I continued to visit the Clark Planetarium regularly. In all my visits and encounters with people who work with space, I became even more determined to become a rocket scientist myself.
During my secondary education, I took as many math and science classes as I possibly could. I attended the Math Circle at the University of Utah, and mathematics quickly became my best subject. For a brief time, I envisioned myself becoming a math teacher, but after a summer working at a space camp, I knew that my passion is space and that any job in a field not related to the celestial sphere would not be the best choice of career for me. I worked at an amazing place called iWorld’s Simulations, located in Murray, Utah. It was a spin off from the Space Center in Pleasant Grove. I worked closely with the children in the story telling process. The next summer, I attended the Summer Mathematics program for High School Students at the University of Utah. I learned about number theory and cryptography. The summer after I graduated from high school, I worked at Astro Camp. I had an amazing summer where I learned even more about space, because I was teaching it. We also visited many space/aerospace places such as Hill Air Force Base and ATK. We talked to astronauts, designed amusement parks, and ran simulators where the kids got to experience what it would be like to be an astronaut. Now heading into college, I know that Space is my future.
I know that I am going to touch the heavens one day. I want to work on the Constellation Program established by NASA. I want to design a rocket so powerful and awesome that when I look at it, I simply say, “Wow.” I want to be a part of an effort to colonize the moon, and eventually travel there myself to continue working on rocketry from a new perspective. My life focuses on space, and this highlight and obsession brings me great joy.
I got the link to your site through one of the documents mailed to me by a
friend.After going through your site I saw that The Christa McAuliffe Space Education Center is poised and well positioned to partner with us.
I am a Scientific/Outreach Officer at African Regional Centre for Space Science and Technology Education-English, located inside Obafemi Awolowo University Campus,Ile-ife, Nigeria (ARCSSTE-E is affiliated to the United Nations). We are into capacity building in the area of space science and technology as well as outreach activities for the schools. I am writing to inquire if your centre will be interested to collaborate with us in reaching out to the young ones in the area of space science and technology.
We have been doing this for the past few years and I believe your input based on your numerous experience will further assist us in achieveing our
objectives. I am actually very interested in the simulation aspect of your programmes which I believe must have thrilled your visitors.
As a space enthusiast and a staff of ARCSSTE-E I love to inspire people about space science and its benefits.I interact with young people almost
on daily basis and have found out that the natural tendency explore [the
universe] have been part of all of us.
I have been priviledged to help design instructional materials from locally resourced materials on space science education for students right from primary to the tertiary level. I have also designed and constructed space education kits for students on excursion as well as those that come for workshops and seminars.I also create and use animations to drive home
space points in some of our programmes. I have helped to fabricate mockups (Ariane, Space Shuttle, Galileo satellite, ISRO, astronauts, etc.) and have acted as the curator for our mini space museum.
I believe it is crucial for the children to have the right foundation [in space science and technology] and get it right now hence the need to reach out to them in a proper manner that is globally accepted.
I have included few pictures of some of our centre's activities in the area of space science education outreach, some objects in our space museum as well as a computer generated image of our new space museum (under