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  Night Sky

Enjoy the starry night skies
Be a considerate neighbor. Reduce nighttime glare. Shield your outside lights downward. Let the stars light up the night.

July 2013 night sky

—Charlie Christmann

Sickly spaceship

Over the last several years, the Kepler spacecraft has searched for, and found, hundreds of new planets circling other stars; astronomers still have thousands of candidate planets to sift through. However, today, Kepler is ailing and not collecting any new data.

Precision pointing of the spacecraft is imperative for its mission as it trails Earth in its solar orbit. It was placed there purposefully to minimize any disturbances to its attitude. Out where it is, the only external forces are from sunlight and the solar wind. This allowed the spacecraft to use gyroscopes to stabilize its gaze while minimizing the amount of fuel needed for onboard thrusters.

As designed, there were four gyros on the spacecraft; to point accurately, three must be operational. Unfortunately, there are only two spinning and the spacecraft is using thruster fuel to keep its communications antenna pointed earthward. As of early June, mission engineers still had hopes of freeing up one of the stalled gyroscopes. Meanwhile, the craft is safe and stable.

Kepler’s recent discoveries

Just over the last year, Kepler was busy providing scientists with amazing new planets, some in bizarre configurations.

In June of 2012, two planets were found orbiting extremely close to one another. The inner planet, Kepler-36b, orbits its host star every 13.8 days and the outer planet, Kepler-36c, every 16.2 days. On their closest approach, the neighboring pair comes within 1.2 million miles of each other. That is only five times the distance from the Earth to the Moon! Kepler-36b is a rocky world measuring 1.5 times the radius and 4.5 times the mass of Earth. Kepler-36c is a gaseous giant measuring 3.7 times the radius and eight times the mass of Earth. While neither is in the habitable zone, it would be interesting to stand on the surface of one of them to watch the other planet wiz by, growing larger and brighter by the hour, and then shrinking away into the distance.

August 2012 saw the discovery of a second, previously-thought-impossible circumbinary system. This is a planetary system (in this case two planets) circling two stars orbiting each other. The Kepler-47 system has a pair of stars in a 7.5-day orbit. Outside these stars, Kepler-47b orbits the pair of stars in less than fifty days, too close and hot to be comfortable for life as we know it. Kepler-47c orbits the stellar pair every 303 days and is in the habitable zone. If there is life there, it will be on a moon of this gas giant planet.

Astronomers announced in February of this year the discovery of a planet just slightly bigger than our moon, quite a challenge considering it lives 210 light-years away from us. This planet, Kepler-37b, has two known companions. Kepler-37c, the next planet outward from the star, is slightly smaller than Venus, measuring almost three-quarters the size of Earth. Kepler-37d, the farthest planet out, is twice the size of Earth. Kepler-37’s host star belongs to the same class as our sun, although it is slightly cooler and smaller. All three planets orbit the star at less than the distance Mercury is to the sun, suggesting they are very hot and inhospitable.

Then, just last April, the Kepler team announced the discovery of the Kepler-62 system with five planets (62b, 62c, 62d, 62e, and 62f) and the Kepler-69 system with two planets (69b and 69c). Three of these planets are slightly larger in size than Earth. Kepler-62f is only forty percent larger than Earth, making it the exoplanet closest in size to the Earth orbiting inside the habitable zone. Kepler-62e, orbits on the inner edge of the habitable zone and is roughly sixty percent larger than Earth. Kepler-69c is seventy percent larger than the Earth and orbits in the habitable zone of a star similar to our sun.

If engineers can heal the Kepler spacecraft, there are likely many more worlds to discover; if not, scientists have more than enough data to keep them busy for many years.

Featured conjunctions

On July 21, look in the evening twilight for the bright yellow-white Venus just 1.25 degrees above the blue-white star Regulus. On the morning of the 22nd, in the pre-dawn twilight, look for Mars 0.75 degrees to the upper right of Jupiter.


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