The University of Texas at Arlington

The University of Texas at Arlington

The Planetarium at UT Arlington

The Planetarium at UT Arlington

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  • How do we know what the Milky Way galaxy looks like, if we cannot travel outside it?
  • Astronomers are not certain exactly what the galaxy looks like. But by using telescopes that see in visible, infrared and ultraviolet light, we are able to plot the positions of the stars and get a good guess of what the galaxy would look like, if we could leave it. It helps that we have so many other known galaxies to compare ourselves to.

    (Tags:  milkyway galaxy)
  • Does the longitude of the Vernal Equinox move around the equator once during 25,800 cycle of the precession of the equinox?
  • Yes, the vernal equinox does change its position due to precession. The equinox points are the points in space where the celestial equator and ecliptic meet. The one that the Sun travels from Southern hemisphere to Northern hemisphere is called Vernal point. This intersection point moves Westward in space at approximately 50 arcsecs/year (Precession motion). That’s why NCP moves across the sky changing the North Star in the long-term. One cycle takes approximately 26,000 yrs. Precession motion changes the position of Vernal Point in reference to the background stars. But the Vernal Point will always be Right Ascension (RA) = 0 because we defined it that way. This means that RA and Declination (DEC) of stars will shift over a long time. For this reason, star catalogues include the year when listing RA and DEC of stars.

    (Tags:  ecliptic  equinox  precession)
  • The Lunar Reconnaissance Orbiter (LRO) scientists mentioned the Moon's craters that have ice in them are probably charged up by static electricity from interacting with the solar wind. Is there a way to measure the voltage from some probe or other?
  • This might be a good one to try to send to the LRO scientists because this will be depend on the amount of ice, as well as electromagnetic field strength caused by the solar wind. Unfortunately, static electricity can’t be measured by probes unless the voltage carrying medium is grounded and discharged. For example, we can’t measure the static electric voltage building up in clouds. However, if we knew the amount of current that was transmitted to a lightning rod by the cloud, then we would be able to estimate the amount of static electricity carried in the cloud just before the lightning.

    (Tags:  moon  nasa  satellite)
  • Can we experience weightlessness near a black hole?
  • I don’t think that you would feel weightless around a black hole, because the difference in gravity between your head and feet is so great that you will be stretched into a long thin string. Even if you can get into a fast orbit around the black hole that would attempt to balance the gravitational forces, creating a free fall situation (exactly the same situation the astronauts have around Earth) you would still feel this stretching on your body. Some astronomers like to call this stretching effect, spaghettification, because it stretches you into a thin piece of spaghetti. You will eventually become stretched so much, that the bonds holding your atoms together will break, so it won’t be you that enters the black hole, but the protons, neutrons and electrons that make you up.

    (Tags:  black hole  gravity)
  • How long would it take to get to Venus going 60 miles per hour?
  • Venus’s distance from Earth varies depending on where each planet it is its orbit around the Sun. The closest that Venus ever gets to Earth is 23.6 million miles. That means that it would take 44.9 years to reach Venus travelling at 60 mph!

    (Tags:  venus)

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