Category Archives: astronomy

astronomy news, cassini, cassini mission, evolution of galaxies, galaxies, globular clusters, omega centauri

Cassini Catches a Cluster

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Omega Centauri as Ring Backdrop

Well, this is kind of cool. The Cassini Mission out at Saturn happened to be studying the planet’s F ring and during the course of the observations caught view of the globular cluster Omega Centauri as it passed through the camera’s field of view.

The movie above is actually 13 images taken three minutes apart and then surgically joined together by the Cassini team to make the animation.  It clearly shows the cluster moving through the background.

Omega Centauri is really a spectacular naked-eye sight. It’s visible from throughout the southern hemisphere and lucky folks in more southerly parts of the northern hemisphere closer to the equator have a good vantage point for it, too. It has several millions stars packed into an area less than 90 light-years across.

The cluster lies about 15,800 light-years away from us, and is the largest of the globular clusters that are associated with the Milky Way Galaxy.  Omega Centauri may have played an interesting role in the evolution of our galaxy. Some astronomers suspect that it could have been part of a dwarf galaxy that was consumed by the Milky Way billions of years ago.  If this is true, then the cluster is what’s left of that galaxy’s core.  It’s an intriguing idea and one that astronomers are still researching.

On an unrelated note, if you’re a fan of the Carnival of Space, check out this week’s Carnival, written by Emily Lakdawalla.  Great stuff in there, including one of my own entries.

astronomy, European Space Agency, solar studies

Solar Dance

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The Interactions Between the Sun and Earth

Space Weather FX -- a series about the interactions between the Sun and Earth's magnetosphere. Courtesy MIT Haystack Observatory.

Earlier this year Mark and I completed work on a series of video podcasts called Space Weather FX. It was funded by NASA through MIT’s Haystack Observatory, and is aimed at helping people understand the interactions between the solar wind and Earth’s geomagnetic system. The series is getting some serious play around the world and we’re pleased about that. It means that people are learning just what the effect of solar activity can be on our fragile planet.

An artist's conception of the four Cluster spacecraft flying in formation to study the effects of the solar wind. Courtesy ESA.

What’s just as cool is that the European Space Agency’s Cluster series of satellites — each named after a different saucy dance: Samba, Salsa, Tango, and Rumba, have been operating for a decade, giving scientists a constant stream of data that allows them to construct a virtual 3D “picture” of how the solar wind (that stream of charged particles that moves constantly out from the Sun), affects our planet and its protective magnetic shield called the magnetosphere.

Cluster’s keen observations of magnetic field interactions have revealed how the solar wind can often penetrate the magnetosphere whipping up giant magnetic whirlpools that can spread highly energetic particles (called plasma) into the upport part of our atmosphere called the ionosphere. What’s more, it has looked carefully at a strange phenomenon called “black auroras” — a sort of “anti-aurora” that sucks electrons from Earth’s ionosphere.

The action of the solar wind and its interaction with the magnetic field of our planet generates huge electrical currents that can be measured. There are also collisions of massive, strong magnetic fields during those interactions. When those collisions take place, there’s a huge release of energy. But there’s also the creation of a central region called a “null point.”  Cluster has given scientists a way to study such a null point, helping them better understand the physics of a magnetic reconnection event.  Now, everything that Cluster studies is mostly invisible to us. We can’t stare at the solar wind and see these magnetic reconnection events.  But, Cluster’s sensitive instruments can track the interactions that so fascinate solar physicists.  It’s a great leap forward for solar physics and I hope that the mission continues for another decade — probing the often violent interactions between Sun and Earth’s magnetosphere.