Astronomy Chapter 7 - Intro to the Solar System

The planet closest to the Sun in the solar system is: a.Mercury b.Pluto c.Venus d.Neptune e.none of the other choices

Mercury

7.1 Overview of Our Planetary System

Our solar system currently consists of the Sun, eight planets, five dwarf planets, nearly 200 known moons, and a host of smaller objects. The planets can be divided into two groups: the inner terrestrial planets and the outer giant planets. Pluto, Eris, Haumea, and Makemake do not fit into either category; as icy dwarf planets, they exist in an ice realm on the fringes of the main planetary system. The giant planets are composed mostly of liquids and gases. Smaller members of the solar system include asteroids (including the dwarf planet Ceres), which are rocky and metallic objects found mostly between Mars and Jupiter; comets, which are made mostly of frozen gases and generally orbit far from the Sun; and countless smaller grains of cosmic dust. When a meteor survives its passage through our atmosphere and falls to Earth, we call it a meteorite.

7.4 Origin of the Solar System

Regularities among the planets have led astronomers to hypothesize that the Sun and the planets formed together in a giant, spinning cloud of gas and dust called the solar nebula. Astronomical observations show tantalizingly similar circumstellar disks around other stars. Within the solar nebula, material first coalesced into planetesimals; many of these gathered together to make the planets and moons. The remainder can still be seen as comets and asteroids. Probably all planetary systems have formed in similar ways, but many exoplanet systems have evolved along quite different paths.

7.3 Dating Planetary Surfaces

The ages of the surfaces of objects in the solar system can be estimated by counting craters: on a given world, a more heavily cratered region will generally be older than one that is less cratered. We can also use samples of rocks with radioactive elements in them to obtain the time since the layer in which the rock formed last solidified. The half-life of a radioactive element is the time it takes for half the sample to decay; we determine how many half-lives have passed by how much of a sample remains the radioactive element and how much has become the decay product. In this way, we have estimated the age of the Moon and Earth to be roughly 4.5 billion years.

7.2 Composition and Structure of Planets

The giant planets have dense cores roughly 10 times the mass of Earth, surrounded by layers of hydrogen and helium. The terrestrial planets consist mostly of rocks and metals. They were once molten, which allowed their structures to differentiate (that is, their denser materials sank to the center). The Moon resembles the terrestrial planets in composition, but most of the other moons—which orbit the giant planets—have larger quantities of frozen ice within them. In general, worlds closer to the Sun have higher surface temperatures. The surfaces of terrestrial planets have been modified by impacts from space and by varying degrees of geological activity.

Which of the following places is most likely NOT to be differentiated? a.a small asteroid b.Earth c.Jupiter d.Venus, because it is so hot e.Ganymede, the largest satellite in the solar system

a small asteroid

Which planet in the solar system has not been examined by spacecraft instruments that have either flown by or orbited them? a.Earth b.Neptune c.Venus d.Saturn e.you can't fool me, spacecraft have visited all the planets in our solar system

You can't fool me, spacecraft have visited all the planets in our solar system

What is one way that astronomers have actually gotten an idea of the age of the surfaces of terrestrial planets other than the Earth? a.looking at the colors different surfaces show b.bringing back samples and run radioactive dating tests c.counting craters d.measuring the thickness of the atmosphere above each surface e.looking in the instruction manual that comes with each planet

counting craters

One piece of evidence that can help astronomers sort out how the planets in our solar system formed is a.discovering other galaxies of stars beyond the Milky Way b.counting the number of moons around each planet in our own solar system c.finding circumstellar disks of material around nearby stars d.counting the craters on the surface of Jupiter, Saturn, Uranus, and Neptune e.measuring variations in the amount of snowfall in northern Canada during this century

finding circumstellar disks of material around nearby stars

The inner planets are made mostly of rock and metal because: a.lighter materials cannot orbit the Sun; they would fall in immediately b.the Sun is made mostly of rock and metal and the inner planets are closest to the Sun c.it was so hot where the inner planets formed that the lighter materials evaporated d.Jupiter's large gravity immediately attracted all the lighter materials, and so there were few light atoms left by the time the inner planets were ready to form e.this is an unsolved problem in astronomy

it was so hot where the inner planets formed that the lighter materials evaporated

In a bad late-night science fiction film, a villain is using a large collection of rare radioactive atoms as energy for a weapon to threaten the good guys. The atoms have a half-life of 1 hour. The villain has 4 kilograms of the radioactive material now, and he needs a minimum of 1 kg. for his weapon to work. After how much time will the weapon no longer be a threat? a.just a little after 1 hr b.just a little after 2 hrs c.just a little after 4 hours d.just a little after 16 hours e.can't be determined from the information given

just a little after 2 hrs

All the planets (without exception) a.have solid surfaces b.have atmospheres much thicker than Earth's c.have satellites orbiting around them d.revolve around the Sun in the same direction e.rotate on their axes in the same direction that they revolve around the Sun

revolve around the Sun in the same direction

What is the most important reason that astronomers have learned more about our planetary system in the last 30-40 years than all of history before then. a.astronomers today are a lot smarter than astronomers were earlier b.the Hubble Space Telescope c.we have been able to send spacecraft to gather information about planets and moons up close d.radio telescope arrays allow astronomers to make out details on the planets that they have never been able to see before e.the planets (moving in their slow orbits around the Sun) happen to be closer to the Earth in the last 30 years than at any previous time in human history

we have been able to send spacecraft to gather information about planets and moons up close

On which of the planets (other than Earth) could a human being step out of a spacecraft and survive without any protective gear (special suit, oxygen tanks, etc)? a.Venus b.Mars c.Jupiter d.Neptune e.you can't fool me; there is no other planet on which we could survive unprotected

you can't fool me; there is no other planet on which we could survive unprotected