Episode 177, December 9, 2013
Hosts: Jesse, Harrison, Rob B., Rob C.
Title: Shine on Chang’e Moon
The first show in a while where we didn’t mention Australia once! (Paul wasn’t on). The Robs, Harrison, and Jesse tackled, what must be, the most wide range of topics the show has seen to date. Ranging from moons of Jupiter, the Star of Bethlehem, all the Milky Way’s super massive black hole and recently discovered jet. It’s been 37 years since a soft landing on the Moon and 41 years since Gene Cernan’s last steps. China’s Change’e lander is currently orbiting the Moon and will go for soft landing December 14th. Stay tuned for that! Thanks for listening all, show notes and podcast below.
This week in space/astronomy history:
1. December 3, 1904 – Charles Perrine’s discovery of Himalia, Jupiter’s fifth-largest moon (by mass) and six-largest (by size). Himalia is also the largest of the irregular satellites (those that do not are retrograde, have highly inclined orbits, or large eccentricities. See Moons of Jupiter on wikipedia. Perinne also discovered Elara.
2. December 6-10, 1998 – Docking (6) and opening (10) of ISS (the first two modules: Zarya and Unity) by STS-88. Three of the astronauts from that mission will reunite at Kennedy Space Center Visitor Complex for a panel discussion to celebrate the anniversary. Space.com wrote an article with 15 fun facts about the ISS. Suggested Reading: Happy 15th Birthday Space Station!
3. December 5-9, 1993 – Hubble Space Telescope (HST) Servicing Mission 1 (SM1) with five extra-vehicular activities (EVAs). This mission was completed as part of STS-61 – Space Shuttle Endeavour, same Orbiter as STS-88 coincidentally.
4. December 14, 1972 – Apollo 17 LEM blasts off Moon; Humans haven’t set foot on the satellite since. Dec 14 is also the date set for Chang’e 3/Yutu to land next weekend (nice connection).
Notable quick mentions: Venera 7 lands on Venus, happy birthday to Tycho Brahe
1. Kepler lives: New follow-on missions proposed for the telescope. Kepler is no longer hunting for exoplanets, but that doesn’t mean it’s useless. The engineers at Ball Aerospace have found a way to balance the Kepler space telescope using rays from the sun in order to control the telescope’s roll axis (Suggested Reading: Space.com article, NASA press release).
2. China launches moon rover. Another step in China developing and demonstrating it’s new space technology/ability, a lunar orbiter and rover named Change’e 3 launched on December 2nd, 2013, and achieved lunar orbit on December 6th. The three month mission is one part of a much larger and long range plan that includes landing humans on the moon, and a permanent settlement (Suggested Reading: Bad Astronomy article, Planetary Society article, Planetary Society update, wikipedia article).
3. MOM completes final maneuver. MOM successfully left Earth orbit and has begun its journey to Mars via a transfer orbit. These maneuvers take advantage of the Oberth effect, an interesting little tidbit of orbital mechanics for those who don’t already know about it (Suggested Reading: A fairly technical infographic on the Oberth Effect, An even more technical explanation, MOM Wikipedia article, Oberth Effect Wikipedia article).
4. Curiosity data shows that astronauts would get a 1.01 Sievert dose for a 500-day round trip to Mars. This is very close to the ESA guidelines of 1 Sievert, which corresponds to a 5% increase in cancer risk over the lifetime. NASA only allows a 0.6 Sievert dose.
5. SpaceX launched its first mission to a geostationary transfer orbit. A geostationary transfer orbit (GTO) is a Hohmann, or transfer orbit, used to get from low Earth orbit to a geosynchronous orbit (Suggested Reading: SpaceX press release, GTO wikipedia article, SpaceX launches first commercial communications satellite).
6. Geminids peak this coming weekend. These moderately slow meteors, originating from Asteroid 3200 Phaethon, peak while the Moon is a gibbous this Saturday. But they’re usually bright, so it’s still worth watching; also, this particular shower starts around 9-10pm, meaning you don’t have to stay up all night (Suggested Reading: earthsky.com guide, JPL guide, American Meteor Society).
Major Topics Discussed:
1. Star of Bethlehem
The Star was a myth, a miracle or an astronomical event. If it was the latter, popular suggestions include a comet, a conjunction or a nova/supernova. Mark Kidger, in his 1999 booked “The Star of Bethlehem – An Astronomer’s View” suggests a series of events that preceded a possible nova in Aquila. Bradley Schaefer recently (Nov 2013) refuted the claim that DO Aquilae was the nova as he claims it is not a recurrent nova (but rather a classical nova) and its last brightening only reached magnitude 8.5.
You can see a McMaster University Planetarium show: www.physics.mcmaster.ca/planetarium
2. CSA funding announcement
Harrison thinks the announcement that the Canadian Space Agency’s Space Technologies Development Program getting more funding is great; Rob B is cautious to support it if it comes at the expense of funding basic research, rather than partnering with industry to do program specific, commercially-linked research. Other significant item in the article is that the CSA’s funding levels will be stable, and a five year plan for Canada’s space program will be released in 2014 (Suggested Reading: Harrison’s Blog Post, Sun News Article).
3. Our SMBH has a Jet
In astronomy, a ‘jet’ is a symmetric flow of gas/plasma/dust out of the poles of a given object. These are common phenomena seen on both small scales (jets associated with stellar objects like neutron stars, white dwarfs, etc.) and on large scales (jets associated with the super massive black holes at the centres of galaxies). A very famous example of a jet can be found in the nearby galaxy M87. It is obvious from any image of the galaxy that there is a large collimated outflow of plasma directed out of the galaxy itself. It’s a strong reminder of the types of forces a black hole generates. The SMBH is literally kicking material out of the galaxy.
While it is not entirely clear exactly what mechanism launched the plasma at such high velocities, out to such great distances, it clear that is related to the accretion process. If material is falling onto a on object like a neutron star or black hole, it forms a disk around it known as an accretion disk. This disk of accreting material is dense, hot, and permeated by large magnetic fields that are not very well understood. It appears that the rotation and bunching of these magnetic field lines, along with the fast rotational speed of material near the core, are responsible for launching jets.
The super massive black hole at the centre of our galaxy, also known as Sagittarius A*, was discovered in 1974, and weighs in at roughly 4 million solar masses. The type of radiation associated with the black hole (synchrotron radiation) indicates the presence of a jet, however, the actual structure has never been found. This was mostly due to, 1. there was no a priori knowledge of the orientation of the jet, 2. the inner galaxy is complicated by a much higher density of stars and star forming activity.
Using a very deep set of data from the Chandra Space Telescope, Zhiyuan Li and Mark Morris were able to confirm the presence of a jet in the galactic centre (Suggested Reading: NASA Press Release, Chandra Blog, arXiv preprint, wikipedia Messier 87 Jet, APOD November 20th 2013).
Final This Week in History
December 11, 1863 – Annie Jump Cannon is born. She was an american astronomer who is credited with the Harvard Classification Scheme, the first attempt at categorizing stars by temperature.
Thanks for listening!
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