Bakersfield Night Sky – September 3, 2016
By Nick Strobel
Last week’s announcement of an Earth-mass planet around Proxima Centauri will surely go down as one of the most exciting astronomy discoveries of 2016. Proxima Centauri is the closest star to us besides the sun. Proxima Centauri b orbits within the star’s habitable zone. The exoplanet announcement was the Astronomy Picture of the Day (APOD) on the second lecture day of the semester. I start most class lectures with the APOD website and to have the announcement happen in the first week of the semester was great timing.
Proxima Centauri is a small red dwarf star that orbits the two primary members of the Alpha Centauri triple-star system in a huge orbit about 15,000 times the Earth-Sun distance. True Star Trek fans will also know that Alpha Centauri is the home system of Zephrem Cochrane, the inventor of warp travel. On page 65 of “Star Trek Spaceflight Chronology” published in 1980, the year after the first Star Trek movie came out, you can read the science officer’s log about his conversation with Cochrane. With no universal translator, they had to use the truly universal language of mathematics to communicate. The publish date of 1980 is important because it is 16 years before The Next Generation movies messed up the timeline and put Cochrane on earth. I’ll be happy to show you my copy of the book and I’m looking forward to the year 2048 when first contact happens (in the original timeline).
Proxima Centauri's planet has a minimum mass of about 1.3 Earth masses and orbits the star at just 0.05 AU in 11.2 days (an “AU” is the Earth-Sun distance). That close distance means the exoplanet will have some sort of tidal locking with the star but still be in the habitable zone. Although the star is a moderately active star, during the quiet periods, its activity and X-ray output are comparable to those of the Sun. The "habitability of Proxima Centauri b" website at www.proximacentauri.info discusses the habitability of the exoplanet under two possible rotation scenarios: a synchronous one (rotation period equals orbit period) and a 3:2 spin-orbit resonance (3 spins for every 2 orbits like Mercury has). The research team's two papers about the habitability of Proxima Centauri b are still in the peer-review process with the Astronomy & Astrophysics journal.
The discovery of an exoplanet orbiting the nearest star has put extra energy behind the Breakthrough Starshot project that is working on sending a nanocraft on a 20-year mission to Alpha Centauri at 20% the speed of light. A nanocraft is only about a gram in mass and consists of a computer chip with the sensors and transmitter attached to a lightsail a meter or so across made of graphite. A gigawatt laser would push on the sail until the craft reaches a speed of 20% the speed of light at which point the craft would coast the rest of the way.
The main problem is not the miniaturization required for the computer chip sensors or the atoms-thin layer of carbon for the lightsail. Instead, the main worry is interstellar dust. Although the chance of running into an interstellar dust grain is thought to be very, very small, any dust grain larger than the width of a human hair hitting the spacecraft at 20% light speed could vaporize the spacecraft. For more about the Breakthrough Starshot project, go to http://breakthroughinitiatives.org/Initiative/3 and for more about the dust hazards of interstellar spaceflight, see Monica Young’s article on the Sky and Telescope website at www.skyandtelescope.com .
In this election season I am still waiting to see if any of the presidential candidates will take up the challenge of answering the questions of ScienceDebate.org . Several questions deal with topics of special concern to Kern County residents including: the internet and cybersecurity, mental illness, energy production, STEM education, public health, access to fresh water, agriculture, environmental regulations, vaccination, and immigration policy. I’m sure that when you look at the questions posed by ScienceDebate.org, you’ll agree that we need to make sure our leaders have thought through those questions because the topics are going to greatly impact all of our lives in the next four years.
Here at home, tickets are now on sale for “Black Holes” that will be shown at the William M Thomas Planetarium on September 22. Next Saturday, September 10, is the free public star party at Panorama Park with the Kern Astronomical Society. See kernastro.org for more details.
In the early evening sky you’ll see Venus pull away from Jupiter low in the western sky as the month progresses. Tonight a thin waxing crescent moon will be to the left of Venus and tomorrow night the moon will be above the bright star Spica. Later this week, on September 8, a fat crescent moon will be above Saturn and then above and to the left of Mars the following night. The triangle of Mars, Saturn, and Antares will lengthen due to Mars’ speedy eastward motion over the month.
Want to see more of the stars at night and save energy? Shield your lights so that the light only goes down toward the ground. See www.darksky.org for how.
Director of the William M Thomas Planetarium at Bakersfield College
Author of the award-winning website www.astronomynotes.com