Bright Stars, Variable Stars, Constellations, and Asterisms

Explores IAU, HD, YBS, GCVS, and open-source star catalogs, BAA variable star data, IAU constellation boundaries, and asterism lines.

Introduction

The sky on a clear night appears to the naked eye salted with stars of visual magnitude ~<6. Their brightness depends on their absolute magnitude and their distance (4 to several hundred LY). The brightest have official names, e.g. Vega. [1]. Many are actually double or triple stars systems and some with variable brightness.

The celestial sphere is divided into 88 irregular exclusive regions called constellations.[1] associated with asterisms. The standardized constellation boundaries follow lines of constant right ascension (RA) and declination (Dec or DEC) in the equatorial coordinate system. These regions form the basis for many historical and still popular Bayer and Flamsteed star designations, e.g. Alpha Centauri, a bright triple star system in the southern constellation of Centaurus.

Several catalogs of stars visible to the naked eye or through a small telescope are in common use and explored in this script.

The IAU named stars catalog lists 451 stars with approved proper names, and is available in text format. It includes the Henry Draper (HD), Yale Bright Star (HR), and Hipparcos (HIP) identifiers for each named star.

The Henry Draper catalog lists some 225,000 stars each with designator HD and a catalog number. It provides location (RA, Dec) and spectroscopic information for stars with visual magnitude less than about 9 and was extended to 359000 stars with prefixes HDE and HDEC and magnitude 11. The HD plus HDEC combination is available at Vizier as catalogue number III/135A with 272150 rows containing RA and Dec updated to J2000.

The Yale Bright Star catalog lists 9110 objects with magnitude <6.5, essentially all those visible to the naked eye, with designator BSC or HR in homage to a predecessor, the Harvard Revised Photometry Catalogue. The Yale Bright Star catalog is available at the NASA High Energy Astrophysics Science Archive Research Center (HEASARC) catalog repository as Bright Star Catalog (bsc5p).

An open source star-catalog (description) by John O'Hanley contains 5112 naked eye stars with magnitude <6 and includes variable stars, cross referenced HD, HR, HIP catalog numbers, historical Bayer and Flamsteed star designators, and proper motion information garnered from the Hipparcos mission.

The General Catalog of Variable Stars is available at Vizier as catalog GCVS 5.1 and contains 58,035 variable stars and provides position, proper motion, spectral information, minimum and maximum magnitude, and period as applicable. Star magnitude variability has serveral sources - flaring, rotation of nonuniform surface features, transits in binary systems, and interaction with nearby material. See the GCVS website for additional information.

More modern catalogs include those produced by the Hipparcos/Tycho mission and provide accurate proper motion measurements of 118,000/2.5 million stars, and the GAIA satellite mission providing similar measurements for ~2 billion stars including 331,000 "nearby" stars (within ~300 LY).

This script imports and explores the open source catalog, the IAU named star catalog, the Yale Bright Star catalog, the Henri Draper catalog, and the General Catalog of Variable Stars. The Hipparcos and GAIA data are explored in related Live Scripts Hipparcos Astrometry Explorer and GAIA data Explorer.

The script also analyzes amateur observations collected by the British Astronomical Association (BAA) of a variable star and produces its light curve using a Lomb-Scargle periodogram that is compared to that display by the American Association of Variable Star Observers (AAVSO).

Finally, the script explores constellation boundary and stick-figure asterism data described in an astronomy.stackexchange post. It imports a text file of right ascension and declination constellation points defining boundaries in J2000 decimal format and constellation acronyms, as well as a file of constellation barycenters, for convenient plotting and naming, and explores two files of asterism stick figures.

This script may interest to students and instructors of physics and astronomy. It is a companion to Mobile Phone Astrometry Explorer, which illustrates how to plate-solve a mobile phone night-sky image with astrometry.net, and Celestial And Image Coordinate Projections Using FITS WCS. Given a FITs file containing an astrometry.net plate solution, the bright stars, constellations, and asterisms provided here may be projected onto an image. The variable star analysis might be compared with the exoplanet transit data analysis in Exoplanet Transit Explorer.

The script provides the various catalogs as MATLAB transportable .mat variables and as generally transportable comma delimited text files, along with text files explaining the variables for each table.

"Try this" suggestions and coding challenges are provided for further exploration. Hyperlinks to documentation are provided for many MATLAB functions so the script may serve as a tutorial for data analysis.