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Monthly Archives: December 2015

From an article on the Sky and Telescope website by Monica Young, originally posted on December 10, 2015.

More than half of the potential giant planets detected by NASA’s Kepler satellite might not be planets after all according to a study by Alexandre Santerne (University of Porto, Portugal, and Aix Marseille University, France). A press release following the Extreme Solar Systems III conference in Hawaii summarized the study with the headline: “Half of Kepler’s Giant Exoplanet Candidates are False Positives.”

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Credit: NASA/Ames Research Center

Santerne and colleagues followed up on Kepler’s long list of planet candidates during a five-year observing campaign. Between July 2010 and July 2015, the team spent 370 nights observing 129 planet candidates out of more than 4,000 that were identified by Kepler, and only 45 of these turned out to be bona fide planets. The rest fell into 3 different categories: 3 were brown dwarfs, 63 were multiple-star systems, and 18 were neither of these, but could not be confirmed as planets. Even if all of those 18 cases turned out to be planets, 51% of Kepler’s giant potential planets would still turn out not to be real.

Previous studies found a much lower ‘false-positive’ rate for Kepler’s planet candidates. However, according to experts on Kepler data, this seemingly surprising high false-positive rate is not surprising at all.

For more information on our Solar System, and others, see Chapter 9 of The Cosmos. Link to the original article here.

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From an article on Sky and Telescope by David Dickinson, originally posted on December 9, 2015.

The Japanese Aerospace Exploration Agency’s (JAXA) Venus Climate Orbitor Akatsuki is finally orbiting Venus – five years later than planned. After a catastrophic main engine failure in 2010 causing the spacecraft to fly past Venus instead of entering its orbit, scientists and engineers have salvaged the mission and put Akatsuki back on track.

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Credit: JAXA

On December 6th 2015, five years to the day of the original blip, four tiny reaction-control thrusters burned for more than 20 minutes to insert the spacecraft into Venusian orbit. Engineers had tested these thrusters to ensure it was possible back in 2011, before putting the spacecraft into hibernation to prolong its life. The first opportunity to execute the manouver came at the beginning of this month, and it proved to be second time lucky for JAXA’s spacecraft.

The six instruments aboard the Akatsuki spacecraft will probe Venus’s atmosphere, measuring its rotation and convection.Researchers also hope to detect evidence for Venusian lightning using a high-speed imager aboard the spacecraft. Viewing across radio, infrared, visible and ultraviolet wavelengths, the payload will also record heat radiated from the Venusian surface and may spot active volcanoes if they exist. A series of radio occultation experiments will also allow researchers to probe the depths of the Venusian atmosphere as the spacecraft makes successive passes behind the planet as seen from Earth.

In addition to the science payload, JAXA also teamed up with the Planetary Society to carry more than 260,000 people’s names and messages printed on aluminium plates aboard the spacecraft.

Whilst the new orbit time is much longer than originally planned, with a closest approach of 400km as opposed to the intended 300km, the JAXA engineers have saved the mission from disaster. Akatsuki, meaning ‘dawn’ in Japanese, will begin to send back its findings in 2016, and as it’s the first time that JAXA have managed to put a spacecraft in orbit around another planet, their wait will hopefully be rewarded.

For more information on the terrestrial planets, see Chapter 6 of The Cosmos.

Link to the original article here.