A system for wide-field astronomical imaging developed and operated by the Institute for Astronomy at the University of Hawaii. Its goal is to survey the sky for moving or variable objects on a continual basis, and also produce accurate astrometry and photometry of already detected objects. It is situated at Haleakala Observatories near the summit of Haleakala in Hawaii. Pan-STARRS1 (PS1) was the first part of Pan-STARRS. The survey used a 1.8 meter telescope and a 1.4 Gigapixel camera to image the sky in five broadband filters (g, r, i, z, y). The PS1 consortium is made up of astronomers and engineers from 14 institutions and six countries. The survey was completed in April 2014. The Pan-STARRS Project is now focusing on building PS2.
Short for Panoramic Survey Telescope and Rapid Response System.
Fr.: étoile en crèpe
A star strongly compressed due to the → tidal force of a → massive black hole. The intense → gravity of the → black hole pulls harder on the nearest part of the star, creating an imbalance. When the star penetrates the → tidal radius, first it becomes cigar-shaped, then the squeezing of the tidal forces flattens the star in its orbital plane to the shape of a → pancake. Next the star rebounds, and as it leaves the tidal radius, it starts to expand. A little further on its orbit the star finally breaks up into gas fragments. This flattening would increase the → density and → temperature inside the star enough to trigger intense nuclear reactions that would tear it apart (Brassart & J.-P. Luminet, 2008, Astron. Astrophys. 481, 259).
Fr.: étoile particulière
A star with a spectrum that cannot be conveniently fitted into any of the standard → spectral classifications.
Fr.: Etiole Pivoine
A peony-shaped nebula around the → Wolf-Rayet star WR 102ka as shown by the → Spitzer Space Telescope image at 24 μm. The formation of this infrared bright nebula is attributed to the recent evolutionary history of WR 102ka during → LBV-type eruptions and/or its strong → stellar wind (see, e.g., A. Barniske et al. 2008, A&A 486, 971).
PG 1159 star
Fr.: PG 1159
A member of the class of stars in transition between → post-AGB and → white dwarf stars, with temperatures as high as 200,000 K, mean mass about 0.6 Msun, and log g = 5.5-8. PG 1159 stars have no hydrogen or He I lines in their spectra, but do show weak He II lines and stronger lines of ionized carbon and oxygen. These stars are thought to be the exposed inner core of a star that has exploded as a → planetary nebula and is on its way to become a white dwarf. Also called → pre-degenerate star
Named after their prototype PG 1159-035, from the Palomar-Green Catalog of Ultraviolet Excess Stellar Objects (Green et al. 1986, ApJS 61, 305); → star.
Piazzi's Flying Star
setâre-ye parande-ye Piazzi
Fr.: étoile volante de Piazzi
Giuseppe Piazzi (1746-1826) was the first to notice the large → proper motion of the star, in 1804. His observations over a period of 10 years revealed the largest proper motion ever detected for any star at the time, leading him to baptize it the "Flying Star;" → fly; → star.
PLAnetary Transits and Oscillations of stars (PLATO)
A space observatory under development by the → European Space Agency for launch around 2024. Its objective is to detect and characterize → exoplanets by means of their → transit signature in front of a very large sample of → bright stars, and measure the seismic oscillations (→ asteroseismology) of the parent stars orbited by these planets in order to understand the properties of the exoplanetary systems.
setâre-ye Plaskett (#)
Fr.: étoile de Plaskett
A → binary system consisting of two → massive stars, which are → supergiants of → spectral types O7.5 and O6. The two components are so close together that they orbit each other with a period of 14.4 days only. The Plaskett's star is a → double-line binary. The estimated masses of the components are 43 (Plaskett A) and 51 (Plaskett B) → solar masses. The lower mass component is optically brighter than the other star. Also known as HR 2422 and HD 47129 (See, e.g., Bagnuolo et al. 1992, ApJ 385, 708).
Named after the Canadian astronomer John S. Plaskett (1865-1941), who made a detailed spectroscopic study of this star in 1922.
setâre-ye qotbi (#)
Fr.: étoile polaire
A star that lies in the direction pointed to by the Earth's → rotation axis. The term usually refers to the star → Polaris, which is the current → north celestial pole star. The → south celestial pole is not associated with any bright star.
Population I star
setâre-ye-e porineš-e I
Fr.: étoiles de population I
A member of a class of relatively young stars, containing a large fraction of → metals, found mainly in the disk of the Galaxy.
Population II star
setâre-ye porineš-e II
Fr.: étoiles de population II
Population III star
setâre-ye porineš-e III
Fr.: étoile de population III
A member of the first generation of stars, formed out of pristine gas, enriched by → primordial nucleosynthesis alone. The material from which these stars formed consisted mostly of hydrogen and helium. Because neutral hydrogen clouds were free of dust, their cooling mechanism was drastically ineffective. As a result, these star forming clouds had a much higher temperature than in the present epoch, and their → Jeans mass was much higher. Therefore, these first generation of stars were principally massive, with a typical mass scale of order of about 100 Msun. Population III stars started forming about 300 million years after the → Big Bang at → redshifts between 50 and 6, when the Universe had between 1 and 5% of its present age. These stars were probably responsible for the → reionization of the Universe. Given their high mass, they lived only a few million years ending with either a → pair-instability supernova phase or a direct collapse to a → black hole. Population III stars thus initiated the chemical enrichment of the Universe and opened the way to more normal modes of star formation, namely → Population II. Some models predict a bimodal → initial mass function for the first stars, allowing also for solar mass stars. See also → extremely metal-poor star.
post-asymptotic giant branch star (post-AGB)
setâre-ye pasâ-šâxe-ye qulân-e nâhamsâvi
Fr.: étoile post-asymptotique
A star in a short-lived evolutionary stage evolving from the → asymptotic giant branch toward higher → effective temperatures. The majority of low and intermediate mass stars (1 to 8 → solar masses) are believed to pass through this stage on their way to becoming → planetary nebulae.
post-main sequence star
setâre-ye pasâ-rešte-ye farist
Fr.: étoile post séquence principale
A star that has evolved off the → main sequence.
post-planetary nebula star
setâre-ye pasâ-miq-e sayyâre-yi
Fr.: étoile post-nébuleuse planétaire
An evolved star whose → planetary nebula has dissipated.
Fr.: étoile pré-dégénérée
Same as → PG 1159 star.
pre-main sequence B[e] star (HAeB[e])
setâre-ye B[e]-ye piš-rešte-ye farist
Fr.: étoile B[e] pré-séquence principale
pre-main sequence star
setâre-ye piš-rešte-ye farist
Fr.: étoile pré-séquence principale
setâre-ye piš-kutule-ye sefid
Fr.: étoile pré-naine blanche
Fr.: étoile principale