Zoom Astronomy Questions and Answers April 2001

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A: Click here.

A: For a page on meteor showers and when the major ones occur, click here.

A: The biggest particles in Saturn's rings are about the size of the car and do not have sufficient gravity to pull you in. If you were in among the rings, you would orbit Saturn as do the ring particles.

A: No, Jupiter does not have seasons. Seasons are caused by a tilted axis, and Jupiter's axis is only tilted 3 degrees (not enough to cause seasons).

A: NASA's Cassini-Huygens spacecraft was launched from Earth on October 1997 to go on an 11-year mission to Saturn. The spacecraft was named after the main division in Saturn's rings, called the Cassini Division. Cassini sent back photos and scientific information from Venus (in 1998) and Jupiter (in 2000) - it used the planets' gravitational fields to boost the spacecraft towards Saturn. In 2004, Cassini will send a probe called Huygens (built by the European Space Agency) to the surface of Titan, (Saturn's biggest moon).

A: Nemesis is a hypothetical companion dark star to our Sun. Once every 30 million years, this dark star would pass through the Oort cloud, triggering comets that perhaps cause periodic mass extinctions on Earth.

Special relativity supplanted Newtonian mechanics, yielding different results for very fast-moving objects. The Theory of Special Relativity is based on the idea that speed has an upper bound; nothing can pass the speed of light. The theory also states that time and distance measurements are not absolute but are instead relative to the observer's frame of reference. Space and time are viewed as aspects of a single phenomenon, called space-time. Energy and momentum are similarly linked. As a result, mass can be converted into huge amounts of energy, and vice versa, according to the formula E=mc².

General Relativity expands the theory to include acceleration and gravity, both of which are explained via the curvature of space-time.

A: Click here for a NASA page on this subject.

A: Jupiter's biggest moon Ganymede, has a magnetic field (and therefore, probably a molten iron core).

A: A planet's gravity is determined by its mass and its size (radius). The weight that you would feel on a planet depends on many things, including your actual mass, the mass of the planet you're on, and how far away you are from the center of that planet.

A: The periodic mass extinctions that have occurred on Earth are an argument for the Nemesis theory.

A: They all rotate in the same direction except for Venus, Pluto, and Uranus which rotate in the opposite direction (have retrograde rotation).

A: The Big Bang theory was formulated by George Gamow and Ralph Alpher, in 1948.

A: I just answered those questions a few days ago. Please scroll down.

A: Jupiter's moon Europa has a liquid ocean.

A: Jupiter's moon Io is volcanically active. Neptune's moon Triton also has volcanos that are probably not active any more.

A: The Io Torus is doughnut-shaped ring of plasma around the planet Jupiter close to the orbit of the moon Io. This torus is caused by Jupiter's strong magnetic field, which strips ions from Io as it rotates; Io acts like an electrical generator. For an image, click here.

A: Saturn's moon Titan has a thick nitrogen atmosphere. Some of the other larger moons, like our moon, Ganymede, Triton, and Europa have extremely thin atmospheres.

A: Click here.

I would really be greatful for the answers given.=)
from dj p, n hollywood, ca, usa; April 21, 2001

A: I answered most of these questions recently (#1,2,3,5). Scroll down for the answers.

As to the others: 4. The ancient Egyptians knew about the year, but it may have been known even before that.

6. Astronomers analyze the light and other electromagnetic radiation coming from the star (or other body). Astronomers can determine the composition of gases in stars by looking for characteristic frequencies in the spectral lines. A spectral line is a bright or dark line found in the spectrum of some radiant sources. Bright lines indicate emission, dark lines indicate absorption. A bright spectral line represents light emitted at a specific frequency by an atom or molecule. Each different element and molecule gives off light at a unique set of frequencies. For example, carbon monoxide (CO) has a spectral line at 115 Gigahertz (equal to a wavelength of 2.7 mm).

7. A radio telescope is a metal dish that gathers radio waves coming from space. (It's like a giant radio that is tuned to sources other than Earth.)

8. An ultraviolet (UV) telescope gathers uv waves coming from space.

A: De Caelo (meaning "About the Heavens") was a book on astronomy written by Aristotle. In it he discusses coemology, the movements of stars, the shape of heavenly bodies, etc., with some mathematical-style discussions.

A: The Saturn V's, which were about 111 m tall. These rockets launched NASA's Apollo missions.

A: Yes.

A: See the entry for solar sail in the astronomy glossary.

A: 24,840 mph. FOr more information, see the entry for escape velocity in the astronomy glossary.

A: Generally , leap years are divisible by four, but century years are special, they must also be divisible by 400. Since 2100 divided by 400 is not an integer, 2100 is not a leap year.

A: 1. WIMP stands for Weakly Interacting Massive Particles. They are hypothetical particles that have a non-zero mass and only participate in weak nuclear interactions. Dark matter may be composed of WIMP's.

2. It takes the sun (and our solar system) roughly 200-250 million years to orbit once around the Milky Way.

3. Trojan asteroids are asteroids that orbit in gravitationally stable Lagrange points in a planet's orbit, either trailing it or preceding it (these places are where the gravitational attraction of the Sun and of the planet balance each other). For more information on Trojan asteroids, click here.

4. Hubble's Law is a linear relationship between the distance to a galaxy (R) and the velocity at which that galaxy is moving from us (v) because to the expansion of the universe. Hubble's Law is is v = H₀ R, where H₀ is Hubble's constant. It assumes that the universe is expanding at a constant rate that has reemained constant for all time.

5. Barringer crater, in Arizona, USA, was created by a meteor hitting the Earth.

6. I've never heard of caronardoes. A carbonardo is a rare type of diamond (with a very hard polycrystalline structure). They were once thought to have been formed as a result of a comet impact 2 billion years ago, but this is no longer thought to be true. The largest diamond ever found was a carbonardo that weighed over half a kilogram.

7. A bolometer is an instrument that measures the total amount of radiant energy (not just visible light) received from a star or other celestial object.

8. Delta Vega would be the fourth planet from the star Vega (Vega is also called Alpha Lyrae - the brightest star in the constellation Lyra); it is not known whether or not any planets orbit Vega).

A: We're roughly 50 light years from the Central Hub of the Milky Way. The time to get there would depend on your speed, but it takes light 50 years to get there (it would take longer than a human lifetime to get there going at our sluggish speeds).

A: Venus is only visible at dawn or dusk since it is closer to the sun than we are. Venus is also known as the "morning star" or the "evening star" since it is visible and quite bright at either dawn or dusk.

A: None.

A: Pluto's average temperature is -393°F (-236°C = 37 K). For more information on Pluto, click here.

A: Yes. Its unusual orbit makes some scientists think that Pluto is not a regular planet. but a "minor planet" or a Trans Neptunian Object (TNO) [Kuiper Belt objects left over from the formation of the solar system]. In the future, Pluto may be listed as an asteroid (it will probably be given the asteroid number 10,000) and also as the first TNO - it will also still be considered a planet, albeit an unusual one.

A: Some astronomers (like Marcy) already have found planets orbiting other stars.

A: Yes, you can.

A: For a section on Neptune, click here.

A: The asteroids orbit between Mars and Jupiter. The planet that orbits in the direction opposite to all the others is Venus.

A: The Hubble space telescope (HST) is named for the American astronomer Edwin Powell Hubble (1889-1953). Hubble showed that other galaxies (besides the Milky Way) existed and observed that the universe is expanding (since the light from almost all other galaxies is red-shifted).

A: Electromagnetic waves are energy in wave form. The electromagnetic spectrum is full range of electromagnetic radiation, including: gamma rays, X-rays, UV rays, visible light, infrared, microwaves, and radio waves (in order of decreasing energy and increasing wavelength).

A: 1. An object in uniform motion tends to remain in that state of motion unless an external force is applied to it (the law of inertia). 2. A force causes a change in the velocity (acceleration) of an object (F=ma). 3. For every action there is an equal and opposite reaction. .

A: Erwin Schrödinger and Paul Dirac won the Nobel Prize in 1933 for a new atomic theory that, among other things, predicted the existence of the positron (the anti-particle of the electron). Carl Anderson won in 1936, for actually discovering the positron experimentally.

A: The corona extends for millions of miles.

A: The big bang theory addresses the origin of the universe. The big bang theory states that the universe began as a tiny but powerful explosion of space-time roughly 15 to 30 billion years ago.

The Earth is about 4.5 billion years old (this is known by using radio-isotope dating to determine the age of the oldest rocks).

A: The Sun is made up of gases. Its mass is about 75% hydrogen and 25% helium. About 0.1% is metals (made from hydrogen via nuclear fusion).

A: The sun will turn into a red giant in about 6 billion years (when this happens, the Earth will be unbearably hot). After that, the Sun will slowly turn into a white dwarf star (emitting very little light).

My favorite planet is Earth.

A: No one knows.

A: A year is defined as the time it takes to orbit around the sun, so there is no "year" for the sun. A day on the sun is the time it takes for one complete revolution around its axis; this takes about 31 Earth days, but that is only an average - it rotates faster at the poles.

A: None, our Solar System consists of our Sun, nine planets, some moons, comets, asteroids, and other smaller objects. A galaxy is a large group of stars - our Solar System is a tiny fraction of the galaxy we call the Milky Way.

A: Charon was named by its discoverer, Jim Christy in 1978. Charon is the name of the mythological demon who ferried people across the mythological river Styx into Hades (Hell). Christy's wife's name is Charlene, and the name Charon was chosen partly to honor her.

A: A blue moon isn't literally a moon that is blue. It is the second full moon in a month in which there are two full moons.

A: Right now, Pluto is farther from the Sun than Neptune. This will change in September 2226, when Neptune will be farther from the Sun than Pluto.

A: Since our Solar System formed, roughly 5 billion years ago, from an enormous cloud of dust and gas

A: Probably.

A: Because Pluto has a moon (called Charon) that is almost as big as Pluto itself. Although Charon is small, about 1,172 km in diameter, it about half of the size of Pluto itself (which has a diameter of 2,274 km).

A: The next blue moon will occur on November 30, 2001, at 20:50.

A: Through the course of a single day (24 hours), they both seem to revolve around a pole. Over time, though, you'll notice a big difference. The stars will essentially remain in the same positions over your lifetime (so you'll always see essentially the same stars, but they'll sometimes be overhead during the day and sometimes at night). The planets are different; over time, the planets change position (seeming to race against the background of the stationary stars) and you will see different planets at different places and times.

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