From Galileo to Gaia: January 6, 2014

Show notes for Episode 180, January 6, 2014
Hosts: Paul, Jesse, Rob C.
Title: From Galileo to Gaia

After long and restful vacation (read: too short and not enough turkey), the York Universe hosts are back to chat about the most recent and awesome space and astronomy stories. Today SpaceX launched a Falcon 9 rocket containing a payload to Geostationary transfer orbit. Two planets move to opposite sides of our sky. And StScI released a great video of the light echoes created by RS Puppis, a Cepheid variable star. Hold onto your butts, show notes and podcast below.

This week in space/astronomy history:
1. January 7, 1610 – Galileo discovers three moons around Jupiter (actually all 4, but couldn’t resolve Europa/Io). Simon Marius named the moons.
Stuart Clark: “The Sky’s Dark Labyrinth”
2. January 7, 1964 – First power tool demonstrated for Space
3. January 8, 1942 – Stephen Hawking born in Oxford, England.  Working from the University of Cambridge, Hawking has in many ways “revolutionized” our understanding of black holes (Hawking Radiation) and has ventured into the public domain of popular science with works such as “A Brief History of Time.”
4. December 24, 1963 – JPL director William H. Pickering in effect created the Deep Space Network that has communicated with every space mission since the early 1960s.  3 x 70 metre dishes spaced around the world allow continuous communication with all spacecraft.

1. The Earth reached perihelion on January 4th, 2014, its closest approach to the Sun in its 365.25 day orbit.
2. Gaia lift off. Following in the footsteps of Hipparcos, Gaia was launched on December 19, 2013 to measure the astrometry of billions of stars (Suggested Reading: Mission Homepage/Blog, wiki page, BBC article, ESA Mission Page, Hipparcos wiki)
3. The ISS has been busy. On December 11, 2013, an ammonia pump (responsible for cooling electrical equipment) malfunctioned forcing the crew to shut it down and switch over to the back up pump. Two spacewalks were performed on December 21st and 23rd of 2013 by Rick Mastracchio and Mike Hopkins (Americans). Another spacewalk occurred on December 27th, 2013 by Oleg Kotov and Sergey Ryazansky (Russians) which attempted to install the high definition Urthecast cameras. Unfortunately, the cameras did not work and were returned to the ISS (Suggested Reading: BBC article, NASA press release, Urthecast homepage)
4. China’s Yutu Moon rover caught on camera by NASA satellite.  Just before the rover went into hibernation, to survive the cold lunar two-week long “night”, it was photographed by the Lunar Reconnaissance Orbiter’s camera orbiting 150 km overhead on December 25, 2013.  The long shadows just at lunar dusk helped distinguish these two objects against the relatively flat surrounding landscape.  Yutu marks a significant milestone in the return to the Moon; it is the first soft landing their for 37 years. Does this herald a new and exciting “Space Race” for the 21st century?  (Suggested Reading: BBC article, wiki page)
Moon movie: (also lunar mining!)
Robert Heinlein book: “The Moon is a harsh mistress” (lunar mining)
5. 223rd AAS meeting gets underway.  Between January 5-9, 2014, thousands of astronomers are descending on Washington, DC, for this year’s AAS’s annual meeting.  Watch this space as we see lots of interesting news stories announced there this week…  For example:
Triple star system ‘can reveal secrets of gravity’.  Under extreme conditions, it’s possible that Einstein’s laws of general relativity may be incompatible with quantum theory.  But how do you recreate these extreme conditions to test this?  You turn to the stars – specifically, a triple-star system that contains pulsar PSR J0337+1715 and two white dwarfs.  The pulsar, essentially a stellar lighthouse, beams pulses of radio waves towards us 366 times per second.  By measuring the differences between these pulses, astronomers can determine if their theories are correct.  (Suggested Reading: BBC article, Nature article)
6. Another milestone for SpaceX.  Earlier this evening (January 5, 2014), SpaceX Falcon 9 successfully launches Thaicom-6.  This was the first time that the privately-funding company used a Falcon 9 rocket for delivering a geosynchronous payload, the Thai communications satellite, Thaicom-6.  Such successful deliveries are important for the future of SpaceX as this is what the majority of commercial launch contracts want.  (Suggested Reading: NASA space flight article, SpaceX wiki)
7. Night sky at a glance. The planet Jupiter hit opposition today at 4pm EST Jan 6, 2014, and the planet Venus will achieve conjunction with the Sun on Jan 11, 2014. (Suggested Reading: SkyNews This Week’s Sky)

Major Topics Discussed:
1. Variable star RS Puppis light echos
Most stars are fairly consistent in their energy output. As they fuse hydrogen into helium and create energy, the resultant luminosity stays very constant. Once a star begins running low on fuel to fuse with, it will begin evolving into different types of stars. One type is the ‘variable star.’ These are stars that change their luminosity over a range of periods. One of the most common (or well known) types of variable stars are called Cepheid variables. These stars were instrumental in the early 20th century as Henrietta Leavitt was measuring the distance to the Large and Small magellanic clouds.
The Cepheid Variable star RS Puppis changes its brightness by a factor of 5 over a period of about 40 days. Since it sits inside a shroud of gas and dust, the change in brightness can be observed as light echoes reflecting off the dust. The Space Telescope Science Institute put together a wonderful video displaying these light echoes.
The first modern variable star cataloged was discovered by John Goodricke of York, England. He observed the star delta Cephei to pulse in brightness over a period of 5 days, 8 hours, and 48 minutes. In observing the star, Goodricke contracted pneumonia and died at the age of 21.
Cepheids as standard candles. Leavitt discovered the Period-Luminosity relationship of classical cepheid variables: the brighter the apparent magnitude of the variable star, the longer the period of pulsation. Since most of the stars Leavitt was observing were in the Small Magellanic Cloud, this would indicate that the change in apparent magnitude must reflect an intrinsic difference in luminosity. By calibrating this P-L relationship, we would then have a standard candle. Such a calibration was achieved by Ejnar Hertzprung in 1913.
Suggested Reading: STScI press release, STScI Videos, ESA press release on distance measurements, Henrietta Swan Leavitt).
Thanks for listening!
-YorkUniverse Team
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