PlanetPol was a ground-based, high sensitivity polarimeter based at the William Herschel Telescope [1] on the island of La Palma in the Canary Islands, Spain that has now been decommissioned. It was the most sensitive astronomical visual polarimeter ever built in fractional polarisation, a mantle that since its decommissioning now belongs to HIPPI. Although the device could be used for a wide range of astronomy, its primary use was the detection of extrasolar planets. [1]
PlanetPol did not discover any extrasolar planets, however it was used to provide upper limits to planetary albedos in the known 55 Cnc and τ Boo planetary systems. [2] Observations with the polarimeter in the Canary Islands, which are affected by dust from the Sahara, also identified airborne dust as a source of polarization within our atmosphere. [3] Additionally, PlanetPol provided measurements of the polarization of a few dozen nearby stars, [4] which were later combined with southern hemisphere measurements from PlanetPol's successor, HIPPI, [5] to provide information about the nature of those stars and the distribution of the interstellar medium. [6]
The Giant Metrewave Radio Telescope (GMRT), located near Narayangaon, Pune in India, is an array of thirty fully steerable parabolic radio telescopes of 45 metre diameter, observing at metre wavelengths. It is operated by the National Centre for Radio Astrophysics (NCRA), a part of the Tata Institute of Fundamental Research, Mumbai. It was conceived and built under the direction of Late Prof. Govind Swarup during 1984 to 1996. It is an interferometric array with baselines of up to 25 kilometres (16 mi). It was recently upgraded with new receivers, after which it is also known as the Upgraded Giant Metrewave Radio Telescope (uGMRT).
Polarimetry is the measurement and interpretation of the polarization of transverse waves, most notably electromagnetic waves, such as radio or light waves. Typically polarimetry is done on electromagnetic waves that have traveled through or have been reflected, refracted or diffracted by some material in order to characterize that object.
Sher 25 is a blue supergiant star in the constellation Carina, located approximately 25,000 light years from the Sun in the H II region NGC 3603 of the Milky Way. It is a spectral type B1Iab star with an apparent magnitude of 12.2. Its initial main sequence mass is calculated at 60 times the mass of the Sun, but a star of this type will have already lost a substantial fraction of that mass. It is unclear whether Sher 25 has been through a red supergiant phase or has just evolved from the main sequence, so the current mass is very uncertain.
Guinevere Alice Mei-Ing Kauffmann was born in California. She is an astrophysicist and is known for her work studying galaxies among other subjects.
HD 27274, also known as Gliese 167, is a solitary, orange hued star located in the southern constellation Dorado. It has an apparent magnitude of 7.63, making it readily visible in binoculars, but not to the naked eye. Based on parallax measurements from the Gaia spacecraft, the star is known to be located 42.5 light-years away from the Solar System However, it is drifting closer with a heliocentric radial velocity of −23 km/s. At its current distance, HD 27274 is dimmed down by 0.05 magnitudes due to interstellar dust.
Kappa2 Coronae Australis, Latinized from κ2 Coronae Australis, is the primary of a probable binary system located in the southern constellation Corona Australis. It is visible to the naked eye as a bluish-white hued star with an apparent visual magnitude of 5.59. The distance to this star is roughly 710 light years based on Gaia DR3 parallax measurements. The radial velocity is poorly constrained, but the star appears to be moving closer with a radial velocity of around −15 km/s. At its current distance, Kappa2 CrA's brightness is diminished by 0.45 magnitudes due to interstellar dust.
HD 138867, also known as HR 5786, is a bluish-white hued star located in the southern circumpolar constellation Apus. It has an apparent magnitude of 5.94, making it faintly visible to the naked eye if viewed under ideal conditions. Based on parallax measurements from the Gaia spacecraft, it is estimated to be 417 light years away from Earth. However, it is receding with a heliocentric radial velocity of 1.1 km/s.
Benedetta Ciardi is an Italian astrophysicist.
Chandrasekhar Polarization is a partial polarization of emergent radiation at the limb of rapidly rotating early-type stars or binary star system with purely electron-scattering atmosphere, named after the Indian American astrophysicist Subrahmanyan Chandrasekhar, who first predicted its existence theoretically in 1946.
Zeta Octantis, Latinized from ζ Octantis, is a solitary, yellowish-white hued star located in the southern circumpolar constellation Octans. It has an apparent magnitude of 5.42, making it faintly visible to the naked eye under ideal conditions. The star is located relatively close at a distance of only 156 light-years based on Gaia DR3 parallax measurements, but is drifting closer with a radial velocity of −3.6 km/s. At its current distance, Zeta Octantis' brightness is diminished by 0.25 magnitudes due to interstellar dust.
NGC 4324 is a lenticular galaxy located about 85 million light-years away in the constellation Virgo. It was discovered by astronomer Heinrich d'Arrest on March 4, 1862. NGC 4324 has a stellar mass of 5.62 × 1010M☉, and a baryonic mass of 5.88 × 1010M☉. The galaxy's total mass is around 5.25 × 1011M☉. NGC 4324 is notable for having a ring of star formation surrounding its nucleus. It was considered a member of the Virgo II Groups until 1999, when its distance was recalculated and it was placed in the Virgo W Group.
Gamma3 Octantis, Latinized from γ3 Octantis, is a solitary star located in the southern circumpolar constellation Octans. It is faintly visible to the naked eye as an orange-hued star with an apparent magnitude of 5.28. The object is located relatively close at a distance of 264 light years but is receding with a heliocentric radial velocity of 15 km/s. At its current distance, Gamma3 Octantis' brightness is diminished by two tenths of a magnitude due to interstellar dust and Eggen (1993) lists it as a member of the old disk population. It has an absolute magnitude of +0.83.
HD 89571 is a binary star located in the northern circumpolar constellation Camelopardalis. It is faintly visible to the naked eye with a combined apparent magnitude of 5.51 and is estimated to be 142 light years away from the Solar System. However, it is receding with a heliocentric radial velocity of 3.5 km/s.
AF Columbae, also known as HD 42682, is a solitary, red hued variable star located in the southern constellation Columba, the dove. It has an apparent magnitude that fluctuates between 5.6 and 5.71. Nevertheless, it is faintly visible to the naked eye. Parallax measurements from the Gaia spacecraft place the star relatively far at a distance of 820 light years. However, it is approaching the Solar System with a poorly constrained radial velocity of −19 km/s.
CD−34°8618, also known as KELT-13 or WASP-167, is a yellowish-white hued star located in the southern constellation of Centaurus. It has an apparent magnitude of 10.52, making it readily visible in medium sized telescopes, but not to the naked eye. Based on parallax measurements from the Gaia spacecraft, the object is estimated to be approximately 1,350 light years away from the Solar System. It appears to be drifting closer to it, having a radial velocity of −0.53 km/s.
HD 34255, also known HR 1720, is a star located in the northern circumpolar constellation Camelopardalis, the giraffe. It has an apparent magnitude of 5.60, allowing it to be faintly visible to the naked eye. The object is located relatively far at a distance of about 1.65 kly but is approaching the Solar System with a heliocentric radial velocity of −7.7 km/s.
PW Telescopii, also known as HD 183806 or simply PW Tel, is a solitary variable star located in the southern constellation Telescopium. It has an average apparent magnitude of 5.58, making it faintly visible to the naked eye. Based on parallax measurements from the Gaia satellite, the star is estimated to be 395 light years distant. It appears to be approaching the Solar System with a heliocentric radial velocity of −10 km/s. The value is somewhat constrained, having an uncertainty of 26%. At its current distance, PW Tel's brightness is diminished by 0.05 magnitudes due to interstellar dust.
HD 170642, also designated as HR 6942 or rarely 13 G. Coronae Australis, is a single star located in the southern constellation Corona Australis. It is faintly visible to the naked eye as a white hued star with an apparent magnitude of 5.16. The object is located relatively close at a distance of 229 light years based on Hipparcos parallax measurements, but it is approaching the Solar System with a somewhat constrained heliocentric radial velocity of −6 km/s. At its current distance, HD 170642's brightness is diminished by 0.28 magnitudes due to interstellar dust. It has an absolute magnitude of +0.93.
HD 23005, also known as HR 1124, is a soltiary, yellowish-white hued star located in the northern circumpolar constellation Camelopardalis, the giraffe. It has an apparent magnitude of 5.78, making it faintly visible to the naked eye. The object is located relatively close at a distance of 173 light years based on Gaia DR3 parallax measurements but is receding with a heliocentric radial velocity of 4.9 km/s. At its current distance, HD 23005's brightness is diminished by 0.15 magnitudes due to extinction from interstellar dust. It has an absolute magnitude of +2.07.
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