Cosmology and observation

Outline of space science

The outline of space science, or space sciences, is a structured overview of the study of Earth, the solar system, and the universe using satellites and observatories.

Palomar Observatory Sky Survey

The Palomar Observatory Sky Survey (POSS) is a photographic survey of the northern sky made with the 48-inch Oschin Schmidt telescope at Palomar Observatory, begun in 1949 and completed in 1958.

Palomar Transient Factory

The Palomar Transient Factory (PTF) was an automated optical sky survey at Caltech's Palomar Observatory, running from 2009 until 2017, that found supernovae and other transient sources.

Pan-STARRS1 Medium Deep Survey

The Pan-STARRS1 Medium Deep Survey repeatedly imaged ten small sky fields with the 1.8-meter Pan-STARRS1 telescope on Haleakala, Hawaii, between 2009 and 2014, discovering over 5,000 supernova-like transients.

Pantheon supernova sample

The Pantheon supernova sample is a 2018 compilation of 1048 Type Ia supernovae, assembled by Dan Scolnic and colleagues to measure cosmic distances and constrain dark energy.

Parallax

Parallax is the apparent shift of a nearby object against a distant background when viewed from different vantage points, used in astronomy to measure stellar distances.

Particle horizon

The particle horizon, also called the comoving horizon, is the maximum distance from which light could have reached us in the age of the universe.

Patrick Moore

Sir Patrick Moore (1923–2012) was an English amateur astronomer who presented the BBC's The Sky at Night from 1957 until his death and compiled the Caldwell Catalogue of 109 deep-sky objects.

Peculiar velocity

A peculiar velocity is a galaxy's velocity remaining after the Hubble flow from the universe's uniform expansion is subtracted, caused by gravitational tugs from surrounding matter concentrations.

Phase closure

Phase closure is an astronomical interferometry technique that sums visibility phases around a closed loop of baselines, typically a triangle of three telescopes, canceling antenna-based phase errors.

Phil Plait

Phil Plait, also known as the Bad Astronomer, is an American astronomer and science writer who debunks astronomy misconceptions online and wrote Bad Astronomy (2002).

Photometric analysis

Photometric analysis is the measurement of the brightness of astronomical objects, such as stars, supernovae, and galaxies, from images, together with how that brightness changes over time.

Photometric calibration

Photometric calibration is the procedure that converts raw instrumental brightness measurements into magnitudes on a standard photometric system, correcting for the instrument's response, atmospheric extinction, and standard reference stars.

Photometric redshift

A photometric redshift is an estimate of a galaxy's redshift and distance from its brightness in several broadband filters, cheaper to obtain than spectroscopy but less precise.

Photometric system (astronomy)

A photometric system in astronomy is a defined set of wavelength bands, standard stars, and zero points for measuring celestial brightness on a common magnitude scale.

Photometry (astronomy)

Photometry in astronomy is the measurement of light energy received per unit time from a celestial source, expressed on a logarithmic magnitude scale attributed to Hipparchus.

Physical cosmology

Physical cosmology, also called cosmophysics, is the branch of physics and astronomy that studies the origin, composition, structure, and evolution of the universe as a whole.

PKS 1510-089

PKS 1510-089 is a flat-spectrum radio quasar, a blazar whose jet points almost at Earth, about 6 billion light-years away and known for dramatic variability.

PKS 2155-304

PKS 2155-304 is a bright high-frequency-peaked BL Lac object at redshift 0.116, detected at TeV energies by H.E.S.S. and famous for its extreme 2006 gamma-ray outburst.

Planck (spacecraft)

Planck was a European Space Agency satellite that surveyed the whole sky from 2009 to 2013 to map the cosmic microwave background, the relic radiation of the Big Bang.

Planck epoch

The Planck epoch is the earliest period of the Universe, lasting from the Big Bang to one Planck time, about 5.39 × 10⁻⁴⁴ seconds, when gravity was as strong as the other forces.

Planck Sunyaev-Zel'dovich cluster catalogue

The Planck Sunyaev-Zel'dovich cluster catalogue lists galaxy clusters found by the Planck satellite through the Sunyaev-Zel'dovich effect, growing from 189 clusters in 2011 to 1653 detections in 2015.

Planet Hunters TESS

Planet Hunters TESS is a Zooniverse citizen science project launched in 2018 in which volunteers inspect NASA TESS light curves to find transiting planets pipelines missed.

Planetarium

A planetarium is a theater with a hemispherical dome on which the motions of stars, the sun, moon, and planets are projected, often for science education.

PLATO (spacecraft)

PLATO, short for PLAnetary Transits and Oscillations of stars, is an ESA space telescope scheduled to launch in 2027 to find Earth-sized exoplanets around bright, nearby stars.

POLARBEAR

POLARBEAR (Polarization of the Background Radiation) is a ground-based cosmic microwave background polarization experiment at the Huan Tran Telescope in Chile's Atacama Desert, known for its 2014 lensing detection.

Press–Schechter formalism

The Press–Schechter formalism is a 1974 analytic method in cosmology that predicts the abundance of dark matter halos, introduced by William H. Press and Paul Schechter.

Prime Focus Spectrograph

The Prime Focus Spectrograph (PFS, Hawaiian Onohi'ula) is a fiber-fed spectrograph at the Subaru Telescope on Maunakea, capturing about 2,400 objects per exposure since 2025.

Primordial black hole

A primordial black hole (PBH) is a hypothetical black hole formed within the first second after the Big Bang from collapsing dense regions, not from dying stars.