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Back from a Week Away

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Exploring an Ice World

An unprocessed image of the moon Helene, orbiting Saturn. Taken by the Cassini spacecraft, June 18, 2011. Courtesy NASA/Cassini Solstice Mission.

I took a week off from writing (everybody  needs a short vacation, right?) and am now back in front of the screen, going through the latest astro-news.

What caught my eye first thing today was the ongoing Cassini Solstice mission. It’s the little spacecraft that just keeps going and going. While her older sisters Voyager and Pioneer are out exploring the outer limits of our solar system, and her little sister New Horizons is headed to Pluto, Cassini keeps sending back images and data about the Saturnian system. The latest views are of a little moon called Helene.

It’s an icy world, which is why I tuned into the story.  Today, June 20, we woke up to snow (which has since turned to rain).  Seems rather incongruous the day before summer solstice (for the northern hemisphere). But, the snow outside reminded me of the snow “out there” – orbiting Saturn like a lopsided iceberg.

It doesn’t take a very close inspection of the image to see the mottled, serrated-looking surface of this little world and to figure out that it looks just plain cold. As to be expected, since temperatures of ice worlds are far, far colder than the conditions we experience here on Earth. Helene is really an irregularly shaped chunk of ice that orbits Saturn in the same orbital path as another moon, Dione. It appears to have been beat up by collisions with other debris in Saturn’s orbit.

Spotting Another Ice Chunk in Space

Animation showing the comet moving against the background of stars. Images taken at the Pan-STARRS 1 Telescope on the night of June 5-6, 2011. Hawaii time is 10 hours earlier than Universal Time (UT). Credit: Henry Hsieh, PS1SC

The distant solar system contains many icy bodies, including these chunky worlds orbiting the gas and ice giant planets. But, there are icy chunks out there that aren’t gravitationally bound to any planets — and astronomers using the Pan-STARRS telescope on Haleakala in Hawai’i spotted one of them just outside the orbit of Jupiter. It’s a comet, called C/2001 L4 (PANSTARRS).  A preliminary orbit computed by the Minor Planet Center in Cambridge, Mass., shows that the comet will come within about 30 million miles (50 million km) of the sun in early 2013, about the same distance as Mercury. The comet will pose no danger to Earth.

The good news about this find is that as it gets closer to the Sun, astronomers have excellent chances to study this comet and figure out just how bright it will appear to be in our skies. If conditions are right, once the comet gets close enough to Earth (say, within the orbit of Mars), it should start to sprout a plasma tail. That’s the tail of ionized gases that streams out from a comet when it gets close enough to the Sun for solar radiation to heat up the gases (and cause them to glow).

It’s tough to know right now just what the composition of the comet is — certainly it’s made of ice. But, how much dust is embedded in that ice?  What kind of ice is it?  Astronomers should be able to tell as they study the comet’s tail with spectrographs (instruments that break up the light from an object into its component wavelengths — and each gas gives off a specific “fingerprint” in the spectrum).

Astronomers think that this comet could be on its first trip around the Sun.  It mostly like comes from the Oort Cloud, that collection of icy objects left over from the formation of the Sun and planets, some 4.5 billion years ago. This cloud lies at the very fringes of the solar system and is a treasure trove of objects that can tell us what conditions were like ‘way back when.

Keep an eye out for this comet in a couple of years. It probably won’t be easy to spot, but if you do see it, you’ll be seeing an object that harks back to a time when our Sun was still forming and the planets were still a work in progress.

AAS meeting stories, american astronomical society, astronomy, astronomy news, cassini mission, JWST, Kepler mission

More Astronomy than You Can Shake a Stick At

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A Sip from the Fire Hose of Astro Information

Every year in early January is “astronomy assimilation” time for me, a time when I can go and soak up all the latest in professional astronomy research. Yes, it’s the annual winter meeting of the American Astronomical Society.  Today’s the first full day of the conference and we hit the ground running.  I’ll be posting sporadic notes from the meeting over the next few days, including some highlighted astronomy discoveries that could make the news in between the coverage of the bad snowstorms and the very sad events in Tucson.

Part of Dr. Porco's talk focused on the dynamic causes of events called "propellers" in the Saturning rings. An unusually large propeller feature is detected just beyond the Encke Gap in this Cassini image of Saturn's outer A ring taken a couple days after the planet's August 2009 equinox.

Today’s meeting began with a short presentation about the future of space observational astronomy particularly as it will be seen through the James Webb Space Telescope. Following that was a wonderful talk sponsored by the Kavli Institute about Saturn’s rings and the observations made by the Cassini spacecraft that are enabling speaker Carolyn Porco and her team members to understand the dynamics of this evolving system.

The first press conference of the meeting featured the discovery of a new rocky world called Kepler-10b. It’s circling a star that lies about 600 light-years away and has been studied steadily by the Kepler planet-finding mission for more than eight months.  This is the first rocky world discovered by Kepler and it’s a fascinating one: it is about 1.4 times the size of Earth and orbits closer to its star than Mercury does to the Sun.

Kepler-10b is a scorched world, orbiting at a distance that’s more than 20 times closer to its star than Mercury is to our own Sun. The daytime temperature’s expected to be more than 2,500 degrees Fahrenheit, hotter than lava flows here on Earth. Intense radiation from the star has kept the planet from holding onto an atmosphere. Flecks of silicates and iron may be boiled off a molten surface and swept away by the stellar radiation, much like a comet’s tail when its orbit brings it close to the Sun.

There are several constants about these meetings — especially in these exciting days of spacecraft missions like Cassini, HST, and Kepler — and that is that we’ll always be hearing about new planets around other stars, we’ll keep learning new things about familiar objects like Saturn and its rings, and Hubble Space Telescope (and its sister orbiting observatories) will keep bringing us gorgeous images of the cosmos.
Each day of this meeting is chock full of papers and results to hear about. My own path through the meeting (at least today) is guided by radio astronomy results, and so I spent some time listening to presentations about early science from the Murchison Widefield Array in Australia and the search for the epoch of reionization at low frequencies.  It’s always amazing to me the new and inventive ways that astronomers can explore the universe and find out things we didn’t know before. The more of these meetings attend, the more I realize that even though we know a LOT – there’s so much more that we will be learning in the days and years and centuries ahead.