Seabooks Press

Astronomy Papers

My years studying astronomy at Mount Stromlo, 1982 to 1986, were intensely satisfying. Despite the complexities of life with a small child, I had the gift of freedom to focus on research (thank you, Gough Whitlam), and discovered something perhaps linked to a dramatic event in the evolution of our own galaxy. After completing my thesis I did postdoc work in the UK, and in 1988 moved into a part-computing, part-astronomy job at CSIRO.

Young, High-Velocity A Stars

Lance, C.M., Ph.D. Thesis, Australian National University, ACT, 1986.

This was the first 'book' I ever wrote. It studied a population of bright, young stars with anomalous compositions, velocities, and a very tight age limit, which suggested they were created during the merger of a small galaxy with ours at around 600 million years ago. The printed versions of this and the other theses at Mt Stromlo Observatory disappeared in the devastating Canberra fires of January 2003. Nobel Prize-winning astronomer Professor Brian Schmidt recalled:

"I could see the pages in the books and then a puff of wind came and blew all the ash in my face. They just kind of evaporated because they were burned through. The best astronomical library in the southern hemisphere, that was gone and never coming back."
Fortunately the librarians of ANU scanned their students' theses for the ANU Open Research Library, so digital copies still exist.

Portrait of a Novel Nova: V1500 Cygni

Lance, C.M., McCall, M. L., Uomoto, A. K., 1988, Astrophysical Journal Supplement Series, 66, p151. From NASA’s Astrophysics Data System

I include this paper only because my name is on it, but I was just a very new postgrad helping with data reduction and producing graphs. All the real work was done by the other authors, but Marshall McCall generously insisted we be listed in alphabetical order. Hours spent happily speculating with Marshall about possible scenarios for the nova's structure were my introduction to the joys of collaboration.

Young, High-Velocity A Stars. I. Rotational Velocities and a Catalog of Early-Type Stars at the South Galactic Pole

Lance, C.M. 1988, Astrophysical Journal Supplement Series, 68, p463. From NASA’s Astrophysics Data System.

The first few anomalous A stars discovered were dismissed as simply misidentified old stars like blue stragglers, or young stars randomly ejected by some unknown mechanism from the galactic disk. This paper describes the calibrations, observations and reductions that went into finding a larger sample of the anomalous stars in a relatively dust-free region of the sky.

Young, High-Velocity A Stars. II. Misidentified, Ejected, or Unique?

Lance, C.M. 1988, Astrophysical Journal, 334, p927. From NASA’s Astrophysics Data System.

The anomalous A stars had unusual chemical compositions and were moving fast, a long way out of their usual location in the galactic disk. My particular finding was being able to date their ages fairly precisely: they were all formed around 600 million years ago, whereas normal stars of this type should randomly show ages up to 2,000 million years.

Only a specific event could cause a population of stars to have such a tight age limit. This, together with their anomalous compositions and velocities, suggested they were evidence of a merger of a small galaxy with ours around 600 million years ago. This may be where the dogma hit the fan — today the the evidence for galactic mergers is completely mainstream, but in the 1980s mergers were the stuff of science fiction.

How Old Are Distant Stars?

Lance, C.M. 1989, Nature, 337, p513.

This was a howl of anguish at seeing yet another casual dismissal of the high-velocity A stars as 'blue stragglers.'

On present evidence, however, it is clear that blue stragglers, or any other type of star formed randomly over time from normal Galactic processes, cannot be proposed as an explanation for the existence of young high-velocity A stars far from the Galactic plane.

Young Halo Stars and Galactic Evolution

Lance, C.M. 1991, Comments on Astrophysics, 15, p355. From NASA’s Astrophysics Data System.

Professor Virginia Trimble kindly suggested I write this paper for Comments on Astrophysics after reading the Letter to Nature above. I was pregnant with my second child at the time (hurdle 101 in the female-scientist obstacle-race) so it was completed nearly two years later.

Whatever has been the true evolutionary path of our galaxy, we must find out what it was. We must be prepared to recognize that perhaps it never was a statistically normal member of its class, provided for our contemplation by a benevolent cosmological principle, but that it has its own unique and significant history that is different from any other galaxy in the Universe.

After Astronomy

In 1992 I finally accepted I had to leave research behind and concentrate on computing. It was a hard time and for many years afterwards I could not bear to see or read anything about astronomy. One small comfort came from a 2015 review by eminent astronomer George W. Preston, who briefly touched on my results in Field Blue Stragglers and Related Mass Transfer Issues:

Metal-rich A-type Stars Above the Galactic Plane: Another Inconvenient Truth — After considering various alternatives, Lance arrived at the earlier conclusion of Rodgers et al: about 0.6 Gyr ago a slightly metal-poor, but still gas-rich, satellite merged with the disc of the Galaxy. During the collision stars formed “that do not partake of the usual age-abundance-kinematics relationships shown by other Galactic stellar groupings”. So far as I am aware, Lance’s work has never been refuted. Rather, it simply has been ignored because, I suspect, her results do not conform to current dogma about Milky Way satellite encounters.
As is the way with science, I'd always expected new work would come along that might explain mine from a different perspective, although so far that hasn't happened. Ah well.

Next came computing in the wild early days of the Internet …