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How exactly is information for CO transitions found?

  1. Jan 14, 2016 #1
    I recently attended a talk about molecular clouds discussing CO transitions in them. I've been trying to understand spectroscopy in astronomy and have tried reading lots of articles online although I still don't quite get everything. It seems that telescopes can find the intensity emitted by certain sources at different wavelengths, such as in normal spectroscopy, correct? How exactly then can a telescope focus on one particular molecular cloud light years away without having this data obfuscated by all the other interacting objects and interfering waves in space? How are we confident this information came from that particular molecular cloud specifically (is it some sort of filter done against the background? If so, could you explain this)? Also, I saw a temperature vs velocity graph that displayed different CO transitions, but how can such a graph even be constructed?

    I unfortunately don't have the slides for reference, but I'm just fascinated and slightly confused by how we actually get all this data from telescopes. Any information you have would be great!
  2. jcsd
  3. Jan 15, 2016 #2

    Simon Bridge

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    You point the telescope precisely at the object you want to study - you can collect light from it the same way you get light from nearby objects without getting confused about other things in the way. One way is to put a metal mask over the telescope that has a small hole in it, and the aim of the telescope through the hole is allowed to pass over the disk of the star or the area of the cloud being studied - the way the data collected changes with the pass is graphed.
    But mainly, if there is something in the way we can see it's effect ... it will block some of the light from what we want to look at.

    Very confident. The data from the regeon of the cloud is compared with data from another region and also from other times.
    By using our understanding of how these things usually work for nearby objects and assuming that physics is the same everywhere.

    Note: Galileo demonstrated his telescope first by pointing it at objects across the room - so people could verify quickly that the telescope showed what was really there. Then he pointed it at more and more distant objects, like the motto carved high up on a building across town (which people knew about)... he did this well before showing them other planets because he needed to build confidence in the telescope.

    It is the same today - observations are not done alone but are built on a long history of other observations and refinements.
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