Date: September 4, 2010

Title: Exoplanet Roundup


Podcaster: Davin Flateau


Description: Exoplanet Roundup: Wrangling the latest exoplanet news from the newest Kepler planets to the discovery of a solar system worth of worlds- saddle up!

Bio: Davin Flateau has been a planetarium director, writer, educator, and large format producer for over 20 years.  He is currently an astrophysics student at the University of Cincinnati.  He hosts the radio show “The Planetarium” about astronomy on the Cincinnati, Ohio airwaves, and is the founder of Aural Moon internet radio, one of the internet’s first radio stations.  His homepage is, and welcomes new Friends at Facebook.

Today’s sponsor: This episode of “365 Days of Astronomy” is sponsored by the American Association of Variable Star Observers, the world’s leader in variable star data and information, bringing professional and amateur astronomers together to observe and analyze variable stars, and promoting research and education using variable star data. Visit the AAVSO on the web at


Exoplanet Roundup!
Davin Flateau

Welcome to the September extrasolar planet roundup! I’m Davin Flateau from the University of Cincinnati and

So many new little planets to corrall, so little time. The current exoplanet roundup count is 490!

Tons and tons of extrasolar planet news over the past few weeks.

Last Thursday, the team at NASA’s Kepler mission announced that they had, for the first time, detected a star that has two transiting planets. If you’re not familiar with the Kepler mission, the spacecraft constantly stares at the same patch of sky and measures any brightness variations in the thousands of stars in its view. A star that varies regularly in brightness may be a planet passing in front of the star, dimming the light from its sun. Well, for the first time, we have a star that has two planets – with a hint of a third – that transit in front of its star. The two newest planets known to humankind, known as Kepler 9b and 9c, are a bit smaller than Saturn, and orbit a star a whopping 2,120 light years away. They’re locked in a 2 to 1 resonance with orbits lasting 19 and 38 days, meaning that they are bound to each other in a push you-pull me dance that keeps the two planets bound together with their star. This is the first time astronomers have found planets outside of our solar system that do this. Matthew Holman of the Harvard Smithsonian Center for Astrophysics explains in a podcast for the journal Science.

But that’s nothing compared to the third suspected planet – seen as a very weak dip in the planet’s brightness – which could be a tiny planet only 1 and a half times the diameter of the earth. On this planet, a year lasts less than two days. Short years means close distances in orbits, so this small planet is very, very close to its star– and surely scorched to a crisp. If confirmed, this planet would be one the smallest planets outside of our solar system yet discovered, and one step closer to finding a true earth-sized planet that may support life as we know it.

The other big extrasolar planet news this week was about a basketball team of planets around a star almost 2000 light years closer to us. A few days before the Kepler news dropped, astronomers using the European Space Agency’s HARPS spectrograph in Chile announced the discovery of an entire solar system – at least 5 planets, with hints of two more around the star HD 10180 in the southern constellation of Hydrus. Also, it looks like the planets are regularly spaced out from its host star, just like our solar system. Team leader Christophe Lovis put the discovery in perspective this way:

“This remarkable discovery also highlights the fact that we are now entering a new era in exoplanet research: the study of complex planetary systems and not just of individual planets. Studies of planetary motions in the new system reveal complex gravitational interactions between the planets and give us insights into the long-term evolution of the system.”

Like most extrasolar planets discovered around the galaxy, these planets hug their stellar parent. The 5 confirmed planets are around Neptune-sized – between 13 and 25 Earth masses that orbit the host star from a speedy 6 days, to a Mars-like 600 days.

Unlike the brightness detection – or transiting – method of Kepler, the HARPS spectrograph, which the European Space Agency describes as the most successful planet-hunting instrument in existence, is attached to a 3.6m telescope at La Silla, Chile. HARPS measures the complex push and pull of the planets on the star by watching the shifting of the star’s light from the red to the blue and back again– essentially – a Doppler shift. Lovis and his team measured and analyzed this wobble for 6 years before they were confident they had enough data to confirm these new worlds. Like the Kepler planets, the two other suspected planets are very low mass planets that have less than 2 day orbits. It’s a race to the bottom for extrasolar planet hunters to see who will be the first to confirm the lowest mass exoplanet.

Lovis goes on to say in the press release that he thinks that low mass planets like in this system seem to be common – but astronomers don’t have a clear explanation of how they form.

One interesting thing that astronomers ARE getting a handle on is what kind of star planets seem to prefer to form around. From the planets we’ve found so far, it appears that big planetary systems tend to form around stars that contain more Iron and other elements heavier than Hydrogen than our Sun. On the other hand the few planetary lightweights we know about have been found around metal-poor stars. Which makes sense according to one idea about why this relationship exists. The more metal a star has, the more iron, silicates and other substances are probably also in the disk that surround the star, that eventually coalesces to form planets. The idea is that metal rich stars simply have more building blocks to form planets than those will less metal-rich material.

So now we have at least 15 stars that are known to have three or more planets, and the total extrasolar planet total is up to 490. Kepler is expected to discover perhaps thousands more in the next few years. So what lies in the future – beyond Kepler or our current host of ground-based transiting surveys or spectrographs?

That question was party answered recently by the release of the Decadal Survey document by the U.S.’s National Research Council. This every 10 year report documents is the result of expert panels, study groups, and a survey of astronomers all across the U.S. This one document maps out the priorities in astronomical research, and is a major factor in what missions or programs get funding. Entitled “New Worlds, New Horizons in Astronomy and Astrophysics”, the report recommends that the search for extrasolar planets be one of the top research priorities for the U.S. over the next 10 years The reports recommends the funding and launch of the WFIRST, or Wide Field Infrared Survey Telescope as a top priority in missions costing over one billion dollars. This Hubble-sized space telescope would be deployed as early as 2020 at the L2 Lagrangian point. Unlike the Hubble or James Webb, however, WFIRST will have a wide view. In addition to trying to answer the question of why the Universe is accelerating, and the telescope will search the Milky Way bulge for gravitational microlensing events. Small changes in brightness in background stars due to unseen solar systems is a powerful technique of finding even tiny planets around other stars. Together with Kepler, WFIRST is slated to give us a good idea of how many earth-like planets there are in the Milky Way.

The future is bright for extrasolar planets! Well, at least in the tiny fluctuations of its brightness.

For the 365 Days of astronomy podcast, this is Davin Flateau.

End of podcast:

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