Discuss why Pluto is no longer considered a planet
What will be an ideal response?
In 2006, the International Astronomical Union (IAU) voted to remove Pluto from the list of planets. Pluto is a very small, icy world: It isn't Jovian, and it isn't Terrestrial. Its orbit is highly inclined and so elliptical that Pluto actually comes closer to the Sun than Neptune at times.A bit of comparative planetology shows that Pluto is not related to the Jovian or Terrestrial planets; it is obviously a member of a newfound family of icy worlds that orbit beyond Neptune. These bodies must have formed at about the same time as the eight classical planets of the Solar System, but they did not grow massive to clear their orbital zones of remnant objects and remain embedded among a swarm of other objects in the Kuiper Belt.One of the IAU's criteria for planet status is that an object must be large enough to dominate and gravitationally clear its orbital region of most or all other objects. Eris and Pluto, the largest objects found so far in the Kuiper Belt, and Ceres, the largest object in the asteroid belt, do not meet that standard. On the other hand, all three are large enough for their gravities to have pulled them into spherical shapes, so they are the prototypes of a new class of objects defined by the IAU as dwarf planets.
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The heaviest nuclei of all are formed:
A) in the horizontal branch. B) in dense white dwarfs. C) during nova explosions. D) in the ejection of matter in the planetary nebula. E) in the core collapse that set the stage of type II supernovae.
In order for the cosmic microwave background to show hydrogen absorption lines at the redshift corresponding to the universe's age of 380,000 years, what condition would have been necessary?
A) There would have needed to be even warmer hydrogen clouds (which would contradict the observation of a uniform temperature in all directions). B) There would have needed to be cooler hydrogen clouds (which would contradict the observation of a uniform temperature in all directions). C) There would have needed to be ionized hydrogen (which would contradict the idea that the CMB originates at the time the universe cooled enough for protons and electrons to combine, making neutral atoms).
Assume a uniformly charged ring of radius R and charge Q produces an electric field Ering at a point P on its axis, at distance x away from the center of the ring as in Figure OQ23.13a. Now the same charge Q is spread uniformly over the circular area the ring encloses, forming a flat disk of charge with the same radius as in Figure OQ23.13b. How does the field Edisk produced by the disk at P
compare with the field produced by the ring at the same point?
A railroad freight car, mass 15,000 kg, is allowed to coast along a level track at a speed of 2.0 m/s. It collides and couples with a 60,000-kg loaded second car, initially at rest and with brakes released. What percentage of the initial kinetic energy of the 15,000-kg car is preserved in the two-coupled cars after collision?
a. 20% c. 86% b. 23% d. 100%