Astronomy 61:
Current Problems in Astronomy and Astrophysics

Spring 2014
Prof. David Cohen

Seminar Room: Science Center 113
11:30 AM - 12:20 PM on Friday


Our topic this semester is compact objects

Manchester Fig. 5
The Crab and Vela pulsar wind nebulae (Chandra X-ray Observatory)


This site is from the last time this course was taught
Astro 61 will be taught again in Spring 2015


For week 14, Matt has chosen "Constraints on Pulsar Evolution: The Joint Period-Spin-Down Distribution of Millisecond Pulsars," Kiziltan & Thorsett, ApJ, 693, L109 (2009).

Matt will post a summary the article on Moodle by Thursday night, and the rest of us should post questions by 9 PM that night.

Kiziltan and Thorsett Fig 2

weekly archive of papers | schedule


Astrophysics Data System (ADS), broad paper search by keyword, author, topic, etc.

arXiv's astro-ph listing a public preprint server (i.e. authors of papers can post their papers here, often before they are actually published). Over the last decade, this has become the go-to place to find papers. But in practice, ADS links to all papers on astro-ph, so you can just start your search there, if you want.

Astrobites: a summary of one paper per day on astro-ph. It's written by graduate students, for undergraduates.

Annual Reviews of Astronomy and Astrophysics: prestigious invited and refereed review articles; they tend to be lengthy. (The link here is for only those articles with "massive stars" in their text.)

Encyclopedia of Astronomy and Astrophysics: few-page articles on specific topics, written at a pretty high level. Useful for finding information about something you read in a paper.


Each week, one of us will chose a paper for us all to read. We'll read it, and then the person who chose the paper will send a summary of it to the class by 9PM on Thursday. And each (other) student will post at least one question on the discussion board forum, also by 9PM on Thursday. The discussion board is available on the class Moodle page.

Whoever's turn it is to choose a paper for a given week should already have some ideas to share with David at the end of class the previous week. So, when it's your turn (schedule soon to be posted), start thinking about what paper you'd like to read about two weeks ahead of time.


This semester, our focus will be on massive stars - stars at least several times as massive as the Sun, with a focus on the most massive stars, which end their lives in supernova explosions.


The goals of this class are to learn how to search and use the astronomical literature, to read papers critically, to apply your knowledge of physics and astronomy to research problems of current interest, and to learn about new developments in astrophysics.

Each week we will read a paper and meet for an hour to discuss it. We will take turns choosing the paper. The person who chooses the week's paper will write a short summary, to be sent out the night before our meeting, and will also introduce the paper at the beginning of class. Everyone else will come up with a question about something that puzzled you about the paper, or about something that you found interesting. You must post your question to Moodle's discussion board by 9PM on Thursday.

What is a paper? A research paper is an article that contains words and often some combination of numbers, equations, graphs, and images (and more recently, on-line supplements that include things like movies of numerical simulations). It usually reports on observations (or occasionally experiments) and/or calculations that address some problem or topic of interest to researchers in a particular subfield. To qualify as a research paper, it must advance the state of knowledge in the field in some important way. There are also review papers which summarize previous results and advances.

For research papers to be taken seriously, they must appear in a refereed journal. That is, they must pass peer review. Reviewers (anonymous "referees") are other scientists in the field (I write research papers and I also referee other people's papers; I usually know to one extent or another most of the authors of the papers I referee). The referee of a paper is charged with assessing the significance of the result described in the paper and with assessing whether the conclusions of the paper really do follow from the data and calculations presented.

There are four major journals in international astronomy, two American ones, The Astrophysical Journal and The Astronomical Journal, a British one, Monthly Notices of the Royal Astronomical Society, and a European one, Astronomy & Astrophysics. There are lower-profile journals, but the gap between them and the four major ones is (perceived to be) large. There are many useful and interesting publications that are unrefereed. Primary among these are conference proceedings papers. Aside from publishing research papers, giving talks at conferences - often quite specialized - is the main way scientists disseminate their research results. Most conferences publish a book, referred to as the conference proceedings, with a paper written by each speaker. Usually these papers follow very closely the talk itself. Importantly for readers like us, these conference proceedings papers fall into two often useful categories: the aforementioned review papers and papers that present preliminary results. Often the substance of a conference paper will appear in a refereed journal a few years later. So conference papers, if they're recent, can be a good way to see what new results might be coming soon. And even if they've been superseded by a refereed journal paper, they can still be shorter, more straightforward, and easier to read.

We should primarily read refereed papers and review articles from conference proceedings. But we shouldn't preclude ourselves from reading conference papers on new research.

I hope that by the end of the semester, you'll be scanning the literature on your own, on a regular basis...just like the pros do. But where to start? Note that there are several different types of places you might look for a paper, including the old fashion way: browsing paper copies on the library shelf. But for the past 20 years or so, literature searches in astronomy have generally started on-line, with Astrophysics Data System (ADS) (non-profit, run out of Harvard/Smithsonian Astrophysical Observatory, with funding from NASA).

ADS catalogs papers from many (nearly every) journal currently published, and many old ones, too. It indexes many conference proceedings articles. From an ADS query you can see the title and author list and almost always an abstract, or paragraph-long description/synopsis of the paper. You can very often download the article in question (as well as see a list of citations, easily see other papers by the same authors, etc). Please realize that the availability of articles, especially recent ones, is often the result of a subscription Cornell Library has to the journal (costs can range from several $100 to several $1000 per year per journal). If you access articles via ADS (or otherwise) from off-campus, you might find your access restricted. You can always use the library's proxy server.

From the ADS query screen you can search for articles by a given author (that's how I use it most often, but I'm very familiar with who writes about what in my field). You can search for a key word in the title or in the abstract, for example. Go ahead and see what you find when you search for "massive stars" in the "title" field (or try the "abstract" field). You can search for articles that discuss particular objects. One of the more extreme and interesting massive stars is eta Carina. What papers can you find about this object (or some other, favorite massive star of yours)?. Note that you can restrict your search results based on publication year, by the type of article (refereed journal vs. conference proceedings paper, for example), sort your results by citation count, or any number of other parameters.

The only other database of papers that a professional astronomer is likely to consult regularly is astro-ph (part of arXiv) where scientists (and others, but not too many others) post papers, short articles, research notes, even lecture notes, ruminations, and direct responses to articles. This is great in a pure availability sense, but there's very little overt quality control (though the overall quality is remarkably high; note that the "comments" field associated with each article provides an opportunity for the author to indicate if the paper will appear in a refereed journal, and what stage of that process the paper is in). The vast majority of papers published in the main journals are posted by their authors to astro-ph. And they appear months ahead of time, quite often. Articles posted on astro-ph are freely available.

There are services that will sort papers on arXiv (like arxivsorter). I get a daily email with 24 hours worth of titles and abstracts. I get it unsorted because I like serendipitous discovery.

Functionally, for me anyway, its timeliness is the main utility of astro-ph. Also, some articles you find listed in ADS but without any actual article availability (they are published in obscure journals or conference proceedings) are posted by their authors to astro-ph. However, a few years ago, ADS started listing every article on astro-ph on its own database, so ADS really is the one-stop shopping article database for astronomers. Just make sure you have the "arXiv e-prints" box near the top of the query page checked.

For hard to find articles or to explore the literature in a different way, you can check out Head Science Librarian Meg Spencer's astronomy subject portal.

Another mode of finding articles is the "newsletter." Many subfields in astronomy have newsletters, to which people in the field submit articles. Most all of these will also appear on astro-ph, but the newsletter collects them in one place, undiluted by articles on other subjects. Sub-field specific newsletters often have additional items such as meeting announcements, job postings (for post-doctoral positions, working on a specific problem, usually). Newsletters are getting to be a relic of another time. They used to be real letters sent on paper through the US mail. But they generally still exist on-line (old people like David and Eric might subscribe to email updates). You might check out the Massive Star News, run by the International Astronomical Union, the organizing and governing body for world-wide astronomy.

For information on a given subject and data from a given type of object, there are often organizations or even individuals who host useful databases, compendia of background information, and other tools. In the field of massive stars, an example is The Galactic O Star Catalog.

Finally, you may want to find out about a particular object or search a catalog for information about an object (e.g. distance, spectral type, magnitude and colors). A good way to do this is via SIMBAD. Note that the entry for any object will provide a list of all the articles published since 1850 that mention that object.


Maintained by David Cohen.

Last modified: May 10, 2014