Monday, 27 March 2017

Pluto a planet? Mercury and Jupiter prime viewing and SotM Katherine Johnson with newly 'bald' @smrolfe


Science Correspondent Sam Rolfe joined us in the studio today just a few days after having shaved her hair off for two great charities, Little Princess Trust who will get her hair to make into a wig for children who have lost theirs due to illness and Macmillan Cancer Support. If you are able and would like to donate, please follow the link(s):

https://www.justgiving.com/fundraising/samantharolfe87  (Little Princess Trust)

https://bravetheshave.org.uk/shavers/samantha-rolfe/ (Macmillan)



Science Feature 27-03-2017




What is a planet anyway?

Is Pluto a planet? A vote by just 424 astronomers on the final day of International Astronomical Union (IAU) Meeting in August 2006. This is only about 5 % of the total astronomers around the world. The controversial decision meant that Pluto was removed from its standing as a planet and was “demoted” to dwarf planet status. 

Only 6 months before the vote had the New Horizons space craft been launched on its journey to the space rock, arriving in 2015. The dwarf planet status and other non-planets seem to make these bodies appear less important to the public for scientific research. The New Horizons team have had enough of being asked why are they going to Pluto if it’s not a planet.

Several proposals have been put to the IAU since Pluto’s demotion to change its status, but most recently one has been proposed, not by astronomers but planetary scientists.

The current definition for a planet is: A celestial body that (a) is in orbit around the Sun, (b) has sufficient mass for its self-gravity to overcome rigid body forces so that it assumes a hydrostatic equilibrium (nearly round) shape, and (c) has cleared the neighbourhood around its orbit.
 
Other than forgetting bodies that orbit other stars or so-called “rogue planets” that are not gravitational bound to a star, the most controversial part of this is (c). Jupiter has 50,000 trojan asteroids. Pluto crosses the path of Neptune so for part of Neptune’s orbit it is further from the Sun than Pluto, so it technically hasn’t cleared its orbit either.

The new proposal suggests, rather than astronomical, a geophysical definition of a planet:
A planet is a sub-stellar mass body that has never undergone nuclear fusion and that has sufficient self-gravitation to assume a spheroidal shape adequately described by a triaxial ellipsoid regardless of its orbital parameters.

Essentially, it removes any reliance on where or what the body orbits. This would give us approximately 110 planets in our Solar System. Many of these are body that are routinely studied and are already of great interest (inc. Moon, Europa…).

For many, the acceptance of such a proposal would right the wrong of Pluto being stripped of planet status.



 
Night Sky this month
Last week saw the March Equinox where day and night were of equal length and we are now into British Summer Time.
1st April Mercury at greatest eastern elongation, it appears furthest from the Sun making it viewable with the naked eye, a rare occurrence. Look for the planet low in the western sky just after sunset at 7:30.
7th April Jupiter at Opposition. Jupiter is closest to the Earth and will be fully illuminated by the Sun, it will be brighter than any other time of year and is visible all night long. Binoculars or a small telescope will allow viewing of its four largest moons.
22nd to 23rd April, peak of the Lyrids meteor shower, best viewed from a dark place after midnight about 20 meteors per hour. Can produce bright dust trails that last for several seconds.
29th April International Astronomy Day, theme “Bringing Astronomy to the People”.



Scientist of the Month



Katherine Johnson, born 1918. Worked for NASA as a computer.
She calculated the trajectories, launch windows, and emergency back-up return paths for many flights from Project Mercury, including the early NASA missions of John Glenn and Alan Shepard, and the 1969 Apollo 11 flight to the Moon, helped ensure the safe return of the Apollo 13 astronauts and worked through the Space Shuttle program. Her calculations were critical to the success of these missions. Johnson also did calculations for plans for a mission to Mars.
Recently highlighted in the film: Hidden Figures.

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