Last week we invited Professor Robert Kirshner from Harvard University to visit New Zealand. We invited him as the Royal Society of New Zealand Distinguished Science lecturer for 2009 and in order to celebrate the International Year of Astronomy.

For those readers who do not know, Bob Kirshner is one of the world’s leading astronomers and definitely one of the most stimulating public speakers. He is currently the Clowes Professor of Science at Harvard and comes from the Harvard-Smithsonian Center for Astrophysics in Cambridge, Mass. Kirshner and his High-Z supernova team were joint recipients of the Gruber Prize in cosmology for their work on type Ia supernovae, which apparently shows that the universe’s expansion is accelerating. This is the work which has led to the discovery of the so-called ‘dark energy’ or Λ-term in modern cosmology. Kirshner is also the author of a popular book on this subject, with the title ‘The extravagant universe’.

Professor Robert Kirshner, Harvard University

In an earlier article written for Cosmic Diary I gave my personal list of the top 25 discoveries in astronomy and astrophysics of the twentieth century (see Cosmic Diary for 18 June: http://cosmicdiary.org/blogs/john_hearnshaw/?p=96). The list was originally prepared for a seminar on this topic, but in compiling my list of 25, I actually considered a larger list of at first 50, which grew to 51 after the seminar!

So in this blog I am going to present what are the most important discoveries between numbers 26 and 51. The criteria for selection were only to include astronomy and astrophysics of the Sun, stars and beyond. Cosmology is of course included, but solar system exploration of planetary bodies by spacecraft was not part of my deliberations (important though that may be). By importance I am referring to impact in discovering something completely new, such as a new phenomenon or type of object, and research which went on to spawn a whole new branch of subsequent investigations. For sure, my judgement is very arbitrary, and I have not done a more careful analysis based on citations, though that would have created its own set of biases.

So much has been written about Galileo in this, the International Year of Astronomy 2009, that I wonder if there is anything original left to say. Like many astronomers I have given a talk this year on Galileo – in my case to the Canterbury Historical Association in October. In researching the lecture, I found I can at least dispel a few myths about Galileo, even if they are not anything new!

Galileo, portrait by Sustermans

The first myth is that Galileo was the first person to use a telescope in astronomy when he made observations of the Moon, planets and Milky Way from December 1609.

In an earlier Cosmic Diary article (28 May) I wrote about three great astronomical photometrists whom I had known. In this article I will write about three influential spectroscopists who guided me in my career and who have had a profound influence on me. All three were not only great scientists, but also great friends. They were Ted Dunham, Giusa Cayrel and Jun Jugaku. As the last two are still alive, I will write mainly about Theodore Dunham (not that my remarks should cause any embarrassment to the living!).