Radial velocity in the context of "HD 202628"

Radar is a system that uses radio waves to determine the distance (ranging), direction (azimuth and elevation angles), and radial velocity of objects relative to the site. It is a radiodetermination method used to detect and track aircraft, ships, spacecraft, guided missiles, motor vehicles, weather formations and terrain. The term RADAR was coined in 1940 by the United States Navy as an acronym for "radio detection and ranging". The term radar has since entered English and other languages as an anacronym, a common noun, losing all capitalization.

A radar system consists of a transmitter producing electromagnetic waves in the radio or microwave domain, a transmitting antenna, a receiving antenna (often the same antenna is used for transmitting and receiving) and a receiver and processor to determine properties of the objects. Radio waves (pulsed or continuous) from the transmitter reflect off the objects and return to the receiver, giving information about the objects' locations and speeds. This device was developed secretly for military use by several countries in the period before and during World War II. A key development was the cavity magnetron in the United Kingdom, which allowed the creation of relatively small systems with sub-meter resolution.

The Laniakea Supercluster or Laniakea for short (/ˌlɑːni.əˈkeɪ.ə/; Hawaiian for "open skies" or "immense heaven"), sometimes also called the Local Supercluster (LSC or LS), is the large-scale structure centered around the Great Attractor that is home to the Milky Way and approximately 100,000 other nearby galaxies. It was originally defined in September 2014 as a galaxy supercluster, when a group of astronomers, including R. Brent Tully of the University of Hawaiʻi at Mānoa, Hélène Courtois of the University of Lyon, Yehuda Hoffman of the Hebrew University of Jerusalem, and Daniel Pomarède of CEA Université Paris-Saclay published a new way of defining superclusters according to the relative velocities of galaxies as basins of attraction. The new definition of the local supercluster subsumes the then prior defined Virgo and Hydra-Centaurus Supercluster as appendages, the former being the prior defined local supercluster.

Follow-up studies suggest that the Laniakea is not gravitationally bound. It will disperse rather than continue to maintain itself as an overdensity relative to surrounding areas. In addition, some papers favored the traditional definition of superclusters as high-density regions of the cosmic web; basins of attraction including Laniakea were therefore proposed to be called "supercluster cocoons" (or "cocoons" for short), containing smaller traditional superclusters, which evolve inside their parent cocoon.

Doppler spectroscopy (also known as the radial-velocity method, or colloquially, the wobble method) is an indirect method for finding extrasolar planets and brown dwarfs from radial-velocity measurements via observation of Doppler shifts in the spectrum of the planet's parent star.As of June 2025, over 1,100 known extrasolar planets (about 19.0% of the total) have been discovered using Doppler spectroscopy.

Nu Fornacis, Latinized from ν Fornacis, is a single, variable star in the southern constellation of Fornax. It is blue-white in hue and faintly visible to the naked eye with an apparent visual magnitude that fluctuates around 4.69. This body is located approximately 370 light years distant from the Sun based on parallax, and is drifting further away with a radial velocity of +18.5 km/s. It is a candidate member of the Pisces-Eridanus stellar stream, which suggests an age of 120 million years or less.

This object is an Ap star with a stellar classification of B9.5IIIspSi matching a late B-type giant star. The 'Si' suffix indicates an abundance anomaly of silicon. It is an Alpha Canum Venaticorum variable that ranges from magnitude 4.68 down to 4.73 with a period of 1.89 days – the same as its rotational period. It is 3.65 times as massive and 245 times as luminous as the Sun, with 3.44 times the Sun's diameter.

Hipparcos was a scientific satellite of the European Space Agency (ESA), launched in 1989 and operated until 1993. It was the first space experiment devoted to precision astrometry, the accurate measurement of the positions and distances of celestial objects on the sky. This was the first practical attempt at all-sky absolute parallax measurement, something not possible with groundside observatories, and thus represented a fundamental breakthrough in astronomy. The resulting high-precision measurements of the absolute positions, proper motions, and parallaxes of stars enabled better calculations of their distance and tangential velocity; when combined with radial velocity measurements from spectroscopy, astrophysicists were able to finally measure all six quantities needed to determine the motion of stars. The resulting Hipparcos Catalogue, a high-precision catalogue of more than 118,200 stars, was published in 1997. The lower-precision Tycho Catalogue of more than a million stars was published at the same time, while the enhanced Tycho-2 Catalogue of 2.5 million stars was published in 2000. Hipparcos's follow-up mission, Gaia, was launched in 2013.

The word "Hipparcos" is an acronym for High Precision Parallax Collecting Satellite and also a reference to the ancient Greek astronomer Hipparchus of Nicaea, who is noted for applications of trigonometry to astronomy and his discovery of the precession of the equinoxes.

Hot Jupiters (sometimes called hot Saturns) are a class of gas giant exoplanets that are inferred to be physically similar to Jupiter (i.e. Jupiter analogues) but that have very short orbital periods (P < 10 days). The close proximity to their stars and high surface-atmosphere temperatures resulted in their informal name "hot Jupiters".

Hot Jupiters are the easiest extrasolar planets to detect via the radial-velocity method, because the oscillations they induce in their parent stars' motion are relatively large and rapid compared to those of other known types of planets. One of the best-known hot Jupiters is 51 Pegasi b. Discovered in 1995, it was the first extrasolar planet found orbiting a Sun-like star. 51 Pegasi b has an orbital period of about four days.

HD 209458 is a star with an orbiting exoplanet in the constellation Pegasus. It has an apparent visual magnitude of 7.65 and an absolute magnitude of 4.28. Because it is located at a distance of 157 light-years (48 parsecs) from the Sun as measured via parallax, it is not visible to the unaided eye. With good binoculars or a small telescope it should be easily detectable. The system is drifting closer with a heliocentric radial velocity of −14.8 km/s.

The Local Volume (LV) is a collection of more than 1,500 galaxies, within a spherical region centred on the Local Group with a radius of 12 megaparsecs from Earth or up to a radial velocity of redshift of z < 0.002 (550 km/s).

It was in this region of the universe where the Local Volume Legacy (LVL) project took place for the study of 258 galaxies through cycles of observations made by the Spitzer Space Telescope using the Infrared Array Camera (IRAC) and the Multiband Imaging Photometer (MIPS).

Gamma Andromedae is a multiple star system in the northern constellation of Andromeda. It is the third-brightest star in the constellation, after Alpheratz and Mirach. Its identifier is a Bayer designation that is Latinized from γ Andromedae, and is abbreviated Gam And or γ And, respectively. The system has the proper name Almach, pronounced /ˈælmæk/. Based on parallax measurements, it is estimated to be about 390 light-years distant. The system is drifting closer to the Sun with a radial velocity of −11.7 km/s.

Mirach is a prominent star in the northern constellation of Andromeda. It is pronounced /ˈmaɪræk/ and has the Bayer designation Beta Andromedae, which is Latinized from β Andromedae. This star is positioned northeast of the Great Square of Pegasus and is potentially visible to all observers north of latitude 54° S. It is commonly used by stargazers to find the Andromeda Galaxy. The galaxy NGC 404, also known as Mirach's Ghost, is seven arcminutes away from Mirach.

This star has an apparent visual magnitude of around 2.07, varying between 2.01 and 2.10, which at times makes it the brightest star in the constellation. Based upon parallax measurements, it is roughly 197 light-years (60 parsecs) from the Solar System. Its apparent magnitude is reduced by 0.06 by extinction due to gas and dust along the line of sight. The star has a negligible radial velocity of 0.1 km/s, but with a relatively large proper motion, traversing the celestial sphere at an angular rate of 0.208″·yr.

Delta Scuti, Latinized from δ Scuti, is a variable star in the southern constellation Scutum. With an apparent visual magnitude that fluctuates around 4.72, it is the fifth-brightest star in this small and otherwise undistinguished constellation. Analysis of the parallax measurements place this star at a distance of about 200 light-years (61 parsecs) from Earth. It is drifting closer with a radial velocity of −43 km/s.

Hamal, pronounced /ˈhæməl/, is a star in the northern zodiacal constellation of Aries. It has the Bayer designation Alpha Arietis, which is Latinized from α Arietis and abbreviated Alpha Ari or α Ari. This star is visible to the naked eye with an apparent visual magnitude of 2.0. Hamal is the brightest star in the constellation and, on average, the 50th-brightest star in the night sky. Based upon parallax measurements made with the Hipparcos astrometry satellite, Hamal is about 65.8 light-years (20.2 parsecs) from Earth. It is drifting closer to the Sun with a radial velocity of −14 km/s.

This is an aging giant star that is likely to host an orbiting planet with a mass greater than Jupiter.

HD 205739 is a yellow-white hued star in the southern constellation of Piscis Austrinus, positioned near the western constellation boundary with Microscopium. It has the proper name Sāmaya, which was selected in the NameExoWorlds campaign by Sri Lanka, during the 100th anniversary of the IAU. Sāmaya (සාමය) means peace in the Sinhalese language.

With an apparent visual magnitude of 8.56, this star requires a small telescope to view. It is located at a distance of approximately 303 light-years from the Sun based on stellar parallax, and is drifting further away with a radial velocity of +9.7 km/s. This star has an absolute magnitude of 3.42.

ν Serpentis, Latinized as Nu Serpentis, is a solitary star in the Serpens Cauda section of the equatorial constellation of Serpens. It is a white-hued star that is faintly visible to the naked eye with an apparent visual magnitude of 4.32. Based upon an annual parallax shift of 16.05 mas as seen from the Sun, it is about 203 light years from the Sun. The star is drifting further away with a radial velocity of +5 km/s.

This is an A-type main-sequence star with a stellar classification of A2V, and is generating energy through hydrogen fusion at its core. It is 350 million years old with a high rate of spin, showing a projected rotational velocity of 123 km/s. The star has 2.64 times the mass of the Sun and 3.0 times the Sun's radius. It is radiating 76 times the Sun's luminosity from its photosphere at an effective temperature of 9,120 K. Nu Serpentis has an optical companion, a magnitude +9.4 star at an angular separation of 46 arcseconds.

HD 256 is a binary star system in the equatorial constellation of Cetus. It has a white hue and is dimly visible to the naked eye with an apparent visual magnitude of 6.20. Based upon parallax measurements, the system is located at a distance of approximately 474 light years from the Sun. It is drifting closer with a radial velocity of −10 km/s.

Originally considered a single star, it was reported to be a shell star in 1982. Circumstellar absorption lines were then found to be variable, showing a similarity to the edge-on debris disk surrounding Beta Pictoris. The stellar classification of A2 IV/V matched an A-type star near the end of its main sequence lifetime, showing traits of an emerging subgiant star phase.

51 Ophiuchi is a single star located approximately 410 light years away from the Sun in the equatorial constellation of Ophiuchus, northwest of the center of the Milky Way. It is visible to the naked eye as a faint, blue-white point of light with an apparent visual magnitude of 4.81. The star is moving closer to the Earth with a heliocentric radial velocity of –12 km/s.

The star has been assigned spectral types of B9.5IIIe and A0 II-IIIe. It is uncertain if it is a pre-main sequence star on the Herbig Ae/Be stage, or is already an evolved giant Be star, as it presents all the characteristics of a typical Be star but also has circumstellar dust that would otherwise indicate a young star. If the star is a Be star, it would be notable for being "a rare, nearby example of a young planetary system just entering the last phase of planet formation". 51 Ophiuchi is about 300,000 years old with 3.3 times the mass of the Sun and a polar radius 5.7 times the Sun's radius. It is radiating three times the Sun's luminosity from its photosphere at an effective temperature of 9,772 K. The star is spinning rapidly with a projected rotational velocity of 267 km/s, close to the critical rotation rate.