Introduction to Ast Obs Tech Inst

The goal of this course is to introduce students to the very wide range of methods by which astronomers can measure the properties of objects beyond the Earth's atmosphere. This is a survey course, meaning that we will touch on many topics, but cover very few -- perhaps none -- in much depth.

One might describe the course as focusing on several closely related issues:

The messengers

You may have heard of "multi-messenger astronomy", a phrase which has become somewhat common recently, due in large part to the influence of LIGO. Although the great majority of astronomers still rely on good ol' electromagnetic waves to get their information, we now do have additional options:



              Q:  How many "messengers" can you name?

The sources

What are the sources of these different messengers from space? As we discuss each type of signal, we will talk about the objects in space which provide the strongest sources. We won't go into great detail, but I hope to provide enough information that you will be able to figure out which observational method might be best for any particular sort of object.



              Q:  What sort of sources are the most likely
                    candidates for each type of messenger?

                    (Just for fun now)

The detectors

How can we actually detect each type of messenger? What is the technology (or technologies) best suited to each? This may involve some physics and/or engineering.

My plan is to touch lightly on most types of detector, in part because our time is limited, but also in part because I'm certainly no expert in most of them. We will go into a bit of detail on optical detectors, simply because they are used widely to study all sorts of objects, and because I know something about them.

The techniques

Hand-in-hand with the physical objects used to detect messengers from space are the methods by which these objects are placed in the right locations; for example, the world's best X-ray spectrograph won't do much good sitting in an observatory on the Earth's surface.

In addition, for a subset of our regimes, I'll try to describe some of the data reduction techniques. This is not the right course to take if you are interested in gaining a working knowledge of, say, optical CCD-based photometry, but it will at least introduce some ideas and basic concepts.

A topical example: the Gravitational Wave source in NGC 4993

Let's look at an event which was all over the news six years ago -- it can show the importance of multi-messenger astronomy. You've probably heard about it.

Perhaps the best way to start our discussion is with a simple timeline:

2017 Aug 17 12:41:06	Fermi satellite	detects a short gamma-ray burst
2017 Aug 18 00:04	CTIO 4-m DEC	starts observing a location in the sky at RA = 197.13, Dec = -23.33
2017 Aug 18 10:25 (??)	Twitter	J. Craig Wheeler announces ( or see summary) a LIGO source with optical counterpart
2017 Aug 18 22:56	ALMA	starts observing a target at RA = 13:09:48, Dec = -23:22
2017 Aug 19 17:09	Chandra satellite	starts a 25-kilosecond exposure at RA = 13:09:48, Dec = -23:22:53
2017 Aug 21 10:53	HST	starts observations under at least 4 different proposals for target-of-opportunity "GRB 170817A" RA = 13:09:48, Dec = -23:22:53.2

You can find a more detailed discussion of this event in one of the later lectures




  Q:  What is the uncertainty in position for the gamma-ray burst?
            (Hint: look at the FITS file linked in the Fermi Trigger list)



  Q:  Just how close are the positions of the gamma-ray burst
            and the optical counterpart?


 
  Q:  Who are the scientists who have been given time to 
            chase this object with HST?
            (Hint: this search form might help)



  Q:  Did the Chandra satellite detect anything?

Some GRB information can be found in this very large list

This might help with HST question

Within a couple of months, the LIGO team published a paper describing their detection of a burst of gravitational waves at this time on Aug 17, 20217.

GW170817: Observation of Gravitational Waves from a Binary Neutron Star Inspiral



  Q:   Where on the sky, in (RA, Dec), did LIGO detect this burst
             of gravitational waves?


  Q:   How close is that to the position at which all those telescopes 
             were pointing?


              RA   =   13:09:48   =   197.45

              Dec  =  -23:22:53   =   -23.38



  Q:  Just what might be present in the sky at the position
         to which these telescopes were pointing?

There are many good tools to answer that question. A few of my favorites are:

The Aladin tool which is best used by downloading a Java application to your computer
Skyview Advanced Query Form

For more information

There was a bit of a leak when this event occurred. I'm not a fan of secrets in science, especially when there's only a brief window of time to observe some rare phenomenon.