Expert: Jayendra Upadhye - 5/16/2004

Question
My name is Fred Jinkens and I am required to do an interview with someone about the job that you chosen to research for an english project.  And I have picked, you guessed it, astronomy.  I would really appreciate it if you could answer these questions for me:
1 In what way has space travel benefited astronomy?
2 Why do stars appear to move at night?
3 How do astronomers still use constellations?
4 About how many times a month do astronomers actually get to observe outerspace?
5 What is retrograde motion?
6 Why do stars appear to twinkle?
7 How do astronomers use computerized scientific models?
8 What type of planetary work do astronomers do?
Thank you for your time.  I greatly appreciate it.

-Fred Jinkins


Answer
Hi fred,
I could not get the job part right..but that should not be a hindernace in answeing your question.
1 - Space travel has immensely benefited astronomy! If you have heard about the hubble space telescope (HST), you will realise this. It has enabled astronomers to view very distant objects without the hinderance of an atmosphere that interfers with observation of very dim objects.
The hubble space telescope has also shown us how densley galaxies are spread in every direction of the sky one looks at.
2 - Star "move" due two reasons. Our own eyes in absence of large steady frames of reference in a dark sky, "wander" or dither a bit and make a star "jump about" a bit about their position. the second long term movement is from east to west due to earths rotation from west to east.
3 - I am not clear what you mean here. They still use constellations to name and identify stars of a constellation sequentially such as eta carineae for example in the constellation carina or alpha, beta centauri in the constellation centaurus.
4 - Round the clock! with the hubble space telescope in place now! Plus the radio telescopes make it possible to observe almost throughout the year, except when the solar interferences become too strong i guess.
5 - Retrograde motion is the motion of planet as observed from the earth, when the planet actually appears to reverse its "normally forward" motion and go back for a while, before resuming its "proper" direction again. This happens because of the "relative motion" of earth and the planet in their elliptical orbits.
6 - stars twinkle because weak starlight is "buffetted" as it passes thru different thermal layers of the atmosphere. stars are much more true  "point sources" than planets so the "whole" star appears to have been momentarily dimmed or lost" which results in a twinkle. planets present a bigger disk and some part continues to be seen at all times in our field of view so the image is less affected than the image of a star in our eyes.
7 - Computerised scientific models are used to study the evolution of stars and their motions as well as to study how the universe evolves.
8 - Again i fail to understand clearly, but "planetary" work that scientists do involves the geologies of planets as well as studies of their absorption / emission ratios, the study of their atmispheres, surface maps, polar caps etc.
Jayen