Local Density low; Astronomers Hopes HIGH!

Show notes for episode 194 – April 28, 2014
Hosts: Paul, Jesse
Title: Local Density low; Astronomers Hopes HIGH!
Paul and Jesse expounded eloquently on all matters of astronomical news (and Cricket scores) this evening, starting with the Tito controversy in space tourism and the birthday of Jan Oort. They chatted about local Toronto events, with a little pat on the back for the wonderfully involved York Observatory Team. Of course, no chat about space is worth its moxy without a short list of how space can kill all humans. Finally, Jesse wrapped by testing Paul’s knowledge of the local stellar systems…Paul did very well. Thanks for tuning in everyone, show notes and podcast below.


This week in space and astronomy history
:
1. April 28, 2001 – Dennis Tito becomes the first space tourist. Flew on Soyuz TM-32 to the ISS, stayed for 6 days and returned onTM-31. A former engineer and NASA scientist, Tito flew as a private citizen. His place in space lead to charged relations with NASA and he was precluded from entering the US portion of the ISS.
2. April 28, 1900 (-5 November 1992) Jan Oort was born. While most well know for the Oort cloud of comets surrounding the Solar System, his influence on astronomy spans the realms of radio astronomy, dark matter, and galaxy rotation to name but a few areas of his interests and expertise. Great quote: Upon his death, Nobel Prize winning astrophysicist Subrahmanyan Chandrasekhar remarked, “The great oak of Astronomy has been felled, and we are lost without its shadow.”

Honourable Birthday Mentions: Bart Bok (1906), Eugene Shoemaker (1928)

News:
1. Local happenings: a)‘What’s up in Space?’ event Sunday May 4, 2014 in Newmarket, Ontario.  Sponsored by the Astronuts Kids Space club, this event will feature a lot of interesting and notable individuals in the astronomy and space science arena; they will be there to excite the next generation of scientists. Feel free to drop in and join the fun!  Website: 3rd Annual What’s up in Space?b)Science Rendezvous follows up the following Saturday May 10, 2014 all across the Greater Toronto Area and beyond. Join the York Observatory team at the Markham town square for our “making of the Universe” display, featuring crater formation and comet building activities! Website: Science Rendezvous Toronto. c) AstroCats! May 3rd and 4th at the David Braley Athletic & Recreation Centre in Hamilton. The York Observatory will have a booth present. Website: http://www.astrocats.ca/
2. A possible exomoon discovered? A gravitational microlensing study has found a system that could be a free-floating planet and its moon. Sadly, since we likely will never have another opportunity to observe the pair again, we may never know the true nature of the pair. Microlensing events typically last about a month and happen when an object closer to us passes in front of a distant star. The gravity of the closer object bends the light coming from the star, focussing and brightening it. A body orbiting the main lensing object further brightens or dims the light from the background star. Astronomers can calculate the mass ratio of the foreground system, in this case 2000:1, but because we don’t know the distance to that system we can’t determine whether it’s a planet and moon (planet more massive than Jupiter, moon less massive than Earth) or a small faint star and a planet. Suggested reading: IFLS, JPL release.

From the paper abstract (http://arxiv.org/abs/1312.3951):
‘Occam’s razor favors a lens system in the bulge of the Milky Way, with host and companion masses of 126 M_Jupiter and 18 M_earth, respectively, at a projected separation of ~ 0.84 AU.  If the system was about 10 times closer, it would have a host a few times Jupiter’s mass and a companion of half Earth’s mass, with separation of about 0.1 AU.  For comparison, the outermost satellites of Jupiter have orbital radii of about 0.2 AU, but the most massive satellite of Jupiter is just 2.5% of Earth’s mass.’

3. Possibly observing a new moon forming? The Cassini Mission has been an unbelievable success in its research of the planet Saturn. Since its arrival at Saturn and orbital insertion on 1 July 2004, Cassini has made countless discoveries about the massive ringed gas giant planet. It appears Cassini has added another discovery to the list with observations that may indicate a new moon is forming in the rings. Informally nicknamed ‘Peggy,’ the strange object/disturbance in the rings of Saturn may in fact be a new moon forming. Astronomers think the disturbance is a result of the gravitational field of some small object. The object itself is too small to be seen, but it’s affects on the rings of Saturn betray its existence. It is tough to tell if this is, in fact, a new Moon forming, but it is one of the more likely explanations. The rings of Saturn are made up of mostly icy chunks ranging in size from dust grain size to a few meters. Suggested Reading: Science @ NASA, Cassini Mission homepage, wikipedia entry, NPR article, Icarus article.
3. Giant Asteroid Hit Earth. An asteroid of estimated diameter 37 km is now thought to have hit the Earth 3.3 billion years ago. Compare that to the 10 km diameter asteroid that helped kill off the dinosaurs only 65 million years ago: the more ancient asteroid was about 187 times more massive. Evidence of its huge impact — the first one mapped from so long ago — comes from an examination of the Barberton Greenstone Belt in South Africa, which shows rocks and ‘crustal fractures’ that are consistent with the idea of a giant impact, the scientists said. The asteroid struck the Earth thousands of miles away from the rocks studied, but where isn’t known. Suggested Reading: Universe Today article, AGU article, abstract for published article.

Major Topics Discussed:
1. Nearby Brown Dwarf discovered only 7.2 lightyears away
The closest system to the Sun is the Alpha Centauri system at 4.4 light-years away; the next closest system is Barnard’s Star at 6.0 light-years away. After that is a binary Brown Dwarf duo called Luhman 16, at 5.69 light-years. Those two were discovered in 2013 using data from WISE and are the closest Brown Dwarfs ever discovered. Now, using data from the the same telescope, astronomer Kevin Luhman (of the aforementioned discovery) announced the fourth closest system to the Sun: WISE 0855-0714, at 7.2 light-years away.
Not only is this new Brown Dwarf very close to the Sun (relative to the size of the Milky Way, that is), it is also very very cold: the surface temperature is -48 < T < -13 degrees Celsius, or as cold as the North Pole on Earth. The Brown Dwarf was found as a result of its high proper motion, which is the motion of the object relative to the Sun. Objects that are far from the Sun (like distant stars) will move relatively slowly across the sky; objects that are very close will move much faster. By taking multiple images of the same location on the sky and then comparing them, its possible to locate an object that is moving, and measure its velocity and distance. As Brown Dwarfs do not shine like stars, these discoveries require the use of an infrared telescope; hence WISE.
How exactly to categorize Brown Dwarfs is a topic of much debate in the community. They are definitely not stars, because they haven’t ignited fusion of hydrogen in their core. Fusion is started when enough mass has accreted onto an object such that the pressure and temperature at the core of the object reaches levels high enough to overcome the Coulomb barrier, and fuse two protons together. Brown Dwarfs simply aren’t massive enough to sustain this reaction. However, classifying them as giant planets is also up for debate. They are much bigger than most of the planets we have discovered in other star systems, and they also occur on their own (i.e., not orbiting a star).  What’s interesting is WISE 0855-0714 has a mass between 3 and 10 times that of Jupiter, making it more likely to be a gas giant planet that was (most likely) ejected from its own star system.
Suggested Reading: Science @ NASA, Bad Astronomy article, List of Nearest Stars,

 

Thanks for listening!
-YorkUniverse Team
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