June 2015

A Disruptive Pathway for Planet Formation

June 30, 2015

Planet formation can be tricky business. Consider that our current models for core accretion show dust grains embedded in a protoplanetary disk around a young star. Mixing with rotating gas, the dust undergoes inevitable collisions, gradually bulking up to pebble size, then larger. As the scale increases, we move through to planetesimals, bodies of at […]

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A Planet Reborn?

June 29, 2015

Objects that seem younger than they ought to be attract attention. Take the so-called ‘blue stragglers.’ Found in open or globular clusters, they’re more luminous than the cluster stars around them, defying our expectation that stars that formed at about the same time should develop consistent with their neighbors. Allan Sandage discovered the first blue […]

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The Zoo Hypothesis as Thought Experiment

June 26, 2015

Imagine a civilization one million years old. As Nick Nielsen points out in today’s essay, the 10,000 year span of our terrestrial civilization would only amount to one percent of the older culture’s lifetime. The ‘zoo hypothesis’ considers extraterrestrials studying us as we study animals in controlled settings. Can a super-civilization study a planetary culture […]

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Beaming ‘Wafer’ Probes to the Stars

June 25, 2015

The last interstellar concept I can recall with a 20-year timeline to reach Alpha Centauri was Robert Forward’s ‘Starwisp,’ an elegant though ultimately flawed idea. Proposed in 1985, Starwisp would take advantage of a high-power microwave beam that would push its 1000-meter fine carbon mesh to high velocities. As evanescent as a spider web, the […]

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Capturing Sedna: A Close Stellar Encounter?

June 24, 2015

With New Horizons scheduled for its flyby of Pluto/Charon in a matter of weeks and a Kuiper Belt extended mission to follow, it’s interesting to note a new paper on objects well beyond Pluto’s orbit. Lucie Jílková (Leiden Observatory) and colleagues address the problem of Sedna and recently discovered 2012VP113. The problem they present is […]

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Charon’s ‘Dark Pole’

June 23, 2015

An abrupt change: I’m holding today’s post (about halfway done, on a stellar flyby that may have produced Sedna and other such objects long in our system’s past) to turn to New Horizons’ latest imagery, which is provocative indeed. We’ll cover the Sedna story tomorrow. What we have from New Horizons is the work of […]

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Yarkovsky and YORP Effect Propulsion for Long-life Starprobes

June 22, 2015

Centauri Dreams regular James Jason Wentworth wrote recently with some musings about Bracewell probes, proposed by Ronald Bracewell in a 1960 paper. Bracewell conceived the idea of autonomous craft that could monitor developments in a distant solar system, perhaps communicating with any local species that developed technology. Pondering how such a craft might manage station-keeping […]

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New Insights into Titan

June 19, 2015

It’s hard to consider a place with surface temperatures of –180°C ‘Earthlike,’ but there are reasons why we see the term so often applied to Titan. The most striking of these is the presence of surface lakes and seas, a phenomenon found nowhere else in the Solar System. The temperatures are cold enough to make […]

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Kepler-138b: A Mars-Size Exoplanet

June 18, 2015

Astronomers at Penn State, NASA Ames, the University of Chicago and the SETI Institute are publishing news of an exoplanetary first: A planet smaller than Earth whose mass and size have both been measured. Kepler-138b is a Mars-sized world orbiting a red dwarf about 200 light years from Sol in the constellation Lyra. This is […]

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Interplanetary Updates: Philae and New Horizons

June 16, 2015

Given that the Philae lander has just come to life after seven months without communicating, it’s no wonder that the mood among everyone involved with Rosetta’s mission to comet 67P/Churyumov–Gerasimenko is exuberant. On the surface of the comet, conditions have been improving for Philae since March, meaning that with higher temperatures and better illumination, it […]

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