Peter D. Usher

Professor Emeritus

Department of Astronomy and Astrophysics
Penn State University

Ph.D. in Astronomy, Harvard University, 1966

Contact Information
Mailing Address: 1725 Yorktown Place, Pittsburgh PA 15235

Research Interests

Extragalactic astronomy, Perturbation Theory, topics in the History of Science


US Survey for faint blue objects

The US survey selects faint blue objects from seven Palomar-Schmidt fields in the North and South Polar Caps. The survey is named "US" for its chief selection effects: Ultraviolet-excess and Starlike morphology. These are completely defined: the Ly α criterionz ≤ 2.2; UBV colors bluer than halo subdwarfs; a morphology condition B< 21.0 – 0.75 / z (ApJ 454, 654, 1995; AJ 111, 645, 1996); and a flux-limit B ≤ 18.5. The selection method uses measured instrumental color indices B–V and U–B and is thus the first quantified multicolor generalization of the methods of Haro & Luyten and Jaidee & Lynga. Initial selection by eye enabled the investigator to “see” the Milky Way halo. Positional accuracy of 2" or better was achieved by Reseau astrometry with a Cuffey astrophotometer in the field mode (PASP 93, 655, 1981). The survey provided the best medium-bright quasar surface density in 1984 (ApJL 287, L3, 1984), and was one of the top surveys for bright quasars in 2000 (AJ 120, 1683, 2000).

US 708 is a high velocity star with the greatest known speed (1200 km/sec) of any gravitationally unbound star, and is further unique as it is a helium star (Geier et al. Science 347, 1126, 2015). US 943 is a cataclysmic variable discovered by Dianne Mattson and now renamed DV UMa (ApJS 48, 51, 1982). US 1329 is about the 200th brightest quasar in the sky and was identified by Penn State graduate students using the 62-inch telescope at the Department’s Black Moshannon Observatory in Pennsylvania (Mitchell et al. PASP 95, 45, 1983). US 1867 is an absorption-line quasar selected for the Hubble Space Telescope quasar absorption line key project (Gannuzi et al. ApJS 118, 1, 1998). US 3215 is an active Seyfert 1 galaxy selected by visiting Nanjing Professor Ke-Liang Huang (ApJS 56, 393, 1984). It is of morphological type gE2 with a de Vaucouleurs profile, centered on a cluster of galaxies of Abell Richness Class 0 (Howell et al. PASP 109, 1149, 1997).


Perturbation analysis

The renormalized Poincaré-Lighthill perturbation theory (Thesis 1966) applied to the method of Shoot and Fit for systems of nonlinear ODEs with 2-point boundary conditions, widens the circle of convergence (IJAA 3, 353, 2013).


Shakespeare and Science

An enduring puzzle of the Renaissance is why William Shakespeare ignores the astronomical revolutions of the sixteenth and early seventeenth centuries. He deals superficially with celestial phenomena and appears oblivious to the effects that new perceptions in cosmology were having on worldview.


HAMLET’S UNIVERSE(Aventine Press 1996-7), and SHAKESPEARE AND THE DAWN OF MODERN SCIENCE (Cambria Press 2010), argue that Hamlet is an allegory for the chief cosmological models that vied for acceptance at the turn of the seventeenth century. Study of Hamlet and four other plays indicate that before 1610 when Galileo observed the heavens telescopically, Shakespeare had knowledge of celestial phenomena that must have resulted from telescopic observation. Analysis of the scripts indicates that Leonard Digges, developer of the Perspective Glass, was the likely source of these data. We posit that Leonard did not die in 1558, 1559, 1570, 1571, 1572, 1573, or 1574 as he is thought to have done, but lived to become the premier poet of the English language.


SHAKESPEARE AND SATURN: ACCOUNTING FOR APPEARANCES (Peter Lang 2015) confirms that Leonard calculated planetary ephemerides at about the same time as Rheticus and Reinhold (1550–1), and that he observed Saturn’s rings prior to 1567. Conventional wisdom has it that Shakespeare is indifferent to chronology, but astronomical dating proves otherwise. In particular, Shakespeare’s plot resolutions coincide with transits of the Earth through Saturn’s ring plane. Analysis of All’s Well places Shakespeare’s description of Kepler’s Supernova SN1604 in full context; Much Ado features the rabid anti-Copernican Francesco Maurolico; and in Comedy of Errors, we discover why time leaps forward and falls backward.

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