Three editions of the Star Catalogue of Tycho Brahe

Tycho Brahe completed his catalogue with the positions and magnitudes of 1004 fixed stars in 1598. This catalogue circulated in manuscript form. Brahe edited a shorter version with 777 stars, printed in 1602, and Kepler edited the full catalogue of 1004 stars, printed in 1627. We provide machine-readable versions of the three versions of the catalogue, describe the differences between them and briefly discuss their accuracy on the basis of comparison with modern data from the Hipparcos Catalogue. We also compare our results with earlier analyses by Dreyer (1916) and Rawlins (1993), finding good overall agreement. The magnitudes given by Brahe correlate well with modern values, his longitudes and latitudes have error distributions with widths of about 2 arcmin, with excess numbers of stars with larger errors (as compared to Gaussian distributions), in particular for the faintest stars. Errors in positions larger than 10 arcmin, which comprise about 15 per cent of the entries, are likely due to computing or copying errors.Comment: Accepted by Astronomy and Astrophysics; 24 pages; 63 figures; 3 machine readable tables made available at CD

No evidence for an early seventeenth-century Indian sighting of Keplers supernova (SN1604)

In a recent paper Sule et al. (Astronomical Notes, vol. 332 (2011), 655) argued that an early 17th-century Indian mural of the constellation Sagittarius with a dragon-headed tail indicated that the bright supernova of 1604 was also sighted by Indian astronomers. In this paper it will be shown that this identification is based on a misunderstanding of traditional Islamic astrological iconography and that the claim that the mural represents an early 17th-century Indian sighting of the supernova of 1604 has to be rejected.Comment: 7 pages, 6 figures. To appear in Astronomical Notes, vol. 334, issue 5 (2013), DOI number 1172

Re-making urban segregation: processes of income sorting and neighbourhood change

Segregation studies have mainly focused on urban structures as a whole or have discussed specific (gentrifying or renewing) neighbourhoods. The literature suggests that changes in segregation occur primarily through selective migration. In this paper, we follow up on recent work that has questioned these orthodoxies, suggesting that in situ social mobility, and entries to and exits from the city population should be taken into account as well, and that dynamics in all neighbourhoods should be considered. The paper traces the processes by which segregation changes for the cities of Amsterdam and The Hague for 1999–2006, using a longitudinal individual-level database covering the entire population. It extends previous work by looking at income rather than socio-economic status and by drilling down to the neighbourhood level. Applying an existing measure of segregation (Delta) in a novel way, the analysis focuses on changes in the spatial distribution of household income, measuring the relative contribution of a range of processes to changes in segregation. Results show that segregation rises in both cities but that different processes drive changes in each case. Furthermore, the aggregate change in segregation for each city masks a diversity of changes at the neighbourhood level, some of which tend to increase segregation while others tend to reduce it. Mapping these changes and the individual processes contributing to them shows that they have a distinct geography, which seems to be structured by historically specific trends in state and housing market context.

The Star Catalogue of Hevelius

The catalogue by Johannes Hevelius with the positions and magnitudes of 1564 entries was published by his wife Elisabeth Koopman in 1690. We provide a machine-readable version of the catalogue, and briefly discuss its accuracy on the basis of comparison with data from the modern Hipparcos Catalogue. We compare our results with an earlier analysis by Rybka (1984), finding good overall agreement. The magnitudes given by Hevelius correlate well with modern values. The accuracy of his position measurements is similar to that of Brahe, with sigma=2 arcmin for with more errors larger than 5 arcmin than expected for a Gaussian distribution. The position accuracy decreases slowly with magnitude. The fraction of stars with position errors larger than a degree is 1.5 per cent, rather smaller than the fraction of 5 per cent in the star catalogue of Brahe.Comment: Accepted by Astronomy and Astrophysics; 23 pages; 62 figures; 1 table made accessible via CD

The RAG1 and RAG2 proteins establish the 12/23 rule in V(D)J recombination

V(D)J recombination requires a pair of signal sequences with spacer lengths of 12 and 23 base pairs. Cleavage by the RAG1 AND RAG2 proteins was previously shown to demand only a single signal sequence. Here, we established conditions where 12- and 23-spacer signal sequences are both necessary for cleavage. Coupled cutting at both sites require

Early star catalogues of the southern sky: De Houtman, Kepler (Second and Third Classes), and Halley

De Houtman in 1603, Kepler in 1627 and Halley in 1679 published the earliest modern catalogues of the southern sky. We provide machine-readable versions of these catalogues, make some comparisons between them, and briefly discuss their accuracy on the basis of comparison with data from the modern Hipparcos Catalogue. We also compare our results for De Houtman with those by Knobel (1917) finding good overall agreement. About half of the about 200 new stars (with respect to Ptolemaios) added by De Houtman are in twelve new constellations, half in old constellations like Centaurus, Lupus and Argo. The right ascensions and declinations given by De Houtman have error distributions with widths of about 40 arcmin, the longitudes and latitudes given by Kepler have error distributions with widths of about 45 arcmin. Halley improves on this by more than an order of magnitude to widths of about 3 arcmin, and all entries in his catalogue can be identified. The measurement errors of Halley are due to a systematic deviation of his sextant (increasing with angle to 2 arcmin at 60 degrees) and random errors of 0.7 arcmin. The position errors in the catalogue of Halley are dominated by the position errors in the reference stars, which he took from Brahe.Comment: 26 pages, 58 figures. Tables will become available at CDS once the article appears in Astronomy and Astrophysic