Download III - National Optical Astronomy Observatory

Examining an actual research paper
Astronomy, like all science, is quantitative and necessitates making measurements.
As an example of this let’s look at a research paper (provided separately as a file)
by Slesnick, Hillenbrand and Massey on “The Star Formation History and Mass
Function of the Double Cluster h and x Persei”. You may not want to read the entire
paper, but scanning sections of it will illustrate the process an astronomer might
follow. To begin, the interplay of reading other’s research and learning all that is
known about a subject will lead a scientists to formulate their own questions. The
question may require some new images, say, of a star cluster. In this case, the
authors applied to Kitt Peak National Observatory for observing time. Their
proposal was selected to receive time (there are always more requests than there is
telescope time).They made their observations with the same telescope that you will
use when you come to Kitt Peak.
This double cluster has been known since antiquity: it is possible to see it without a
telescope in a dark site. Fig. X is a color combined images taken at Kitt Peak. Notice that
most of the stars appear blue-white, but a few are rather orange. For scale, the separation
of the two clusters is just about the angular diameter of the moon (or the sun) in the sky.
In the ABSTRACT. The authors summarize the entire paper, especially their conclusion
that these two clusters are at the same distance and that they formed at the same time.
They also conclude that the different masses of the stars in the clusters are normal fro
clusters like these.
In the INTRODUCTION, they discuss what other astronomers have learned about the
cluster, and the controversy over the age and formation stage of these clusters. They
explain that in addition to using ccd images, they have taken spectra of hundreds of stars.
In OBSERVATIONS AND DATA REDUCTION they present a detailed explanation of
every step of their work. The first sentence, “UBV photometry was obtained…” tells
others that they took ccd images through 3 filters called U (for very blue), B (for blue)
and V (for visual, or red). If you skip the details in sect. 2.1 but look at their Table 1, you
find the magnitudes and colors (remember, quantitatively astronomers use the difference
in magnitude between two filters and call it the “color”) they have measured. This table
contains only the first 5 stars of 4528, but the rest of the data is to be found in electronic
form. Publishing all these numbers in a paper journal would be out of the question! Table
1 also includes the spectral types: the results of classifying the spectra of several hundred
of these stars. (sect. 2.2)
In 3.ANALYSIS the authors use their measurements to draw conclusions. The details
here are beyond what we need to discuss, but Fig. 7 presents data in a form known to
every elementary astronomy student. This is the H-R diagram. Each filled circle
represents a star with both photometry (through 3 different filters) and spectroscopy;
open circles are stars with only photometry.
In sect 4. DISCUSSION they do just that. What does it all mean?
Finally, Sect 5 SUMMARY, presents a final few words as well as acknowledgements of
both those who inspired the work and the funding agency that made it possible. The paper
ends with a list of all references, all papers referred to in the body of the article. Now that
you have finished scanning this paper, you might note that under the authors names is a
line “Received 2002 February 27; accepted 2002 May 18” This indicates that after they
submitted the paper to the journal in which is was ultimately published, the editor sent the
paper to an anonymous referee (but quite probably someone who has done similar work)
Not until this referee was satisfied with the paper could it be accepted for publication.