Chinese astronomy

ChineseastronomyChinese astronomers
Astronomy in China has a long history, beginning from the Shang Dynasty (Chinese Bronze Age). Chinese star names later categorized in the twenty-eight mansions have been found on oracle bones unearthed at Anyang, dating back to the middle Shang Dynasty, and the mansion (xiù:宿) system's nucleus seems to have taken shape by the time of the ruler Wu Ding (1339–1281 BCE).

NASA

National Aeronautics and Space AdministrationNASA Advisory CouncilU.S. space program
In 2017, using an improved statistical method, two studies reduced the estimated number of NEAs brighter than absolute magnitude 17.75 (approximately over one kilometer in diameter) to 921. The estimated number of asteroids brighter than absolute magnitude of 22.0 (approximately over 140 m across) rose to 27100, double the WISE estimate, of which about a third are known as of 2018. A problem with estimating the number of NEOs is that detections are influenced by a number of factors. Observational biases need to be taken into account when trying to calculate the number of bodies in a population. What is easily detected will be more counted.

Ursa Major Moving Group

Ursa Major StreamCollinder 285Ursa Major association
Since then, the sparse group has scattered over a region about 30 by 18 light-years, whose center is currently about 80 light-years away, making it the closest cluster-like object to Earth. The Ursa Major Moving Group was discovered in 1869 by Richard A. Proctor, who noticed that, except for Dubhe and Alkaid (Eta Ursae Majoris), the stars of the Big Dipper asterism all have proper motions heading towards a common point in Sagittarius. Thus, the Big Dipper, unlike most constellations or asterisms, is largely composed of related stars.

Breakthrough Starshot

StarChipBreakthrough Starshot initiativeSprites
Breakthrough Starshot is a research and engineering project by the Breakthrough Initiatives to develop a proof-of-concept fleet of light sail spacecraft named StarChip, to be capable of making the journey to the Alpha Centauri star system 4.37 light-years away. It was founded in 2016 by Yuri Milner, Stephen Hawking, and Mark Zuckerberg. A flyby mission has been proposed to Proxima Centauri b, an Earth-sized exoplanet in the habitable zone of its host star, Proxima Centauri, in the Alpha Centauri system.

SN 1054

supernova of 10541054 Supernovaa 3-week long supernova in 1054
This star, of medium brightness (apparent magnitude of 3.3), is the only star of its level of brightness in this area of the sky (there is no other star that is brighter than an apparent magnitude of 4.5 within 7 degrees of ζ Tauri), and therefore the only one likely to figure among the asterisms of "Shi Shi". All of these elements, along with some others, allow "Tianguan" to be confirmed beyond reasonable doubt as corresponding to the star ζ Tauri. Three Chinese documents indicate that the guest star was located "perhaps a few inches" South-East of Tianguan. Song Shi and Song Huiyao stipulate that it "was standing guard" for the asterism, corresponding to the star ζ Tauri.

List of galaxies

List of largest galaxieslargest galaxies knownlargest known galaxies
Wolfram Research: Scientific Astronomer Documentations - Brightest Galaxies. 1956 Catalogue of Galaxy Redshifts: Redshifts and magnitudes of extragalactic nebulae by Milton L. Humason, Nicholas U. Mayall, Allan Sandage. 1936 Catalogue of Galaxy Redshifts: The Apparent Radial Velocities of 100 Extra-Galactic Nebulae by Milton L. Humason. 1925 Catalogue of Galaxy Redshifts: [ ] by Vesto Slipher. (1917) First Catalogue of Galaxy Redshifts: Nebulae by Vesto Slipher. Interactive Map of the Visible Universe with Galaxies: Deep Space Map.

Voyager 1

Voyager IVoyagerMariner 11
The apparent magnitude of the Sun from the spacecraft was −16.3 (less than 30 times the brightness of the full moon). The spacecraft was traveling at 17.043 km/s relative to the Sun. It would need about 17,565 years at this speed to travel a light-year. To compare, Proxima Centauri, the closest star to the Sun, is about 4.2 light-years (2.65 AU) distant. Were the spacecraft traveling in the direction of that star, 73,775 years would pass before Voyager 1 reaches it. (Voyager 1 is heading in the direction of the constellation Ophiuchus. ) In late 2012, researchers reported that particle data from the spacecraft suggested that the probe had passed through the heliopause.

Galactic Center

Galactic Centregalactic corecenter
These so-called "Fermi bubbles" extend up to about 25,000 light years above and below the galactic center. The galaxy's diffuse gamma-ray fog hampered prior observations, but the discovery team led by D. Finkbeiner, building on research by G. Dobler, worked around this problem. The 2014 Bruno Rossi Prize went to Tracy Slatyer, Douglas Finkeiner, and Meng Su "for their discovery, in gamma rays, of the large unanticipated Galactic structure called the Fermi bubbles". The origin of the bubbles is being researched.

Cassiopeia (constellation)

CassiopeiaCassiopeia constellationCassiopea
It has been reported to show eclipses of less than 0.1 magnitudes with a period of 2 years and 1 month., but this has never been confirmed. It is 99.4 ± 0.4 light-years from Earth. Epsilon Cassiopeiae has an apparent magnitude of 3.3. Located 410 ± 20 light-years from Earth, it is a hot blue-white star of spectral type B3 III with a surface temperature of 15,680 K. It is 6.5 times as massive and 4.2 times as wide as the Sun, and belongs to a class of stars known as Be stars—rapidly spinning stars that throw off a ring or shell of matter.

Twinkling

scintillationtwinkleScintillation (astronomy)
Twinkling, or scintillation, is a generic term for variations in apparent brightness or position of a distant luminous object viewed through a medium. If the object lies outside the Earth's atmosphere, as in the case of stars and planets, the phenomenon is termed astronomical scintillation; within the atmosphere, the phenomenon is termed terrestrial scintillation. As one of the three principal factors governing astronomical seeing (the others being light pollution and cloud cover), atmospheric twinkling is defined as variations in illuminance only.

Deneb

Alpha CygniAridedα Cyg
Deneb's absolute magnitude is currently estimated as −8.4, placing it among the visually brightest stars known, with an estimated luminosity nearly. This is towards the upper end of values published over the past few decades, which vary between and. Deneb is the most luminous first magnitude star, that is, stars with a brighter apparent magnitude than 1.5. Deneb is also the most distant of the 30 brightest stars by a factor of almost 2.

Joseph von Fraunhofer

FraunhoferJoseph FraunhoferFraunhofer refracting telescope
He found that the spectra of Sirius and other first-magnitude stars differed from the sun and from each other, thus founding stellar spectroscopy. These dark fixed lines were later shown to be atomic absorption lines, as explained by Kirchhoff and Bunsen in 1859. These lines are still called Fraunhofer lines in his honor; his discovery had gone far beyond the half-dozen apparent divisions in the solar spectrum that had previously been noted by Wollaston in 1802.

Flare star

flare starsflareflare events
Flare stars are intrinsically faint, but have been found to distances of 1,000 light years from Earth. On April 23, 2014, NASA's Swift satellite detected the strongest, hottest, and longest-lasting sequence of stellar flares ever seen from a nearby red dwarf. The initial blast from this record-setting series of explosions was as much as 10,000 times more powerful than the largest solar flare ever recorded. The Sun's nearest stellar neighbor Proxima Centauri is a flare star that undergoes occasional increases in brightness because of magnetic activity.

Open cluster

open star clusterstar clusteropen clusters
The core is typically about 3–4 light years across, with the corona extending to about 20 light years from the cluster centre. Typical star densities in the centre of a cluster are about 1.5 stars per cubic light year; the stellar density near the Sun is about 0.003 stars per cubic light year. Open clusters are often classified according to a scheme developed by Robert Trumpler in 1930.

Circumstellar habitable zone

habitable zonehabitable zonesGoldilocks zone
Discovered by radial velocity in June 2017, with approximately 3 times the mass of Earth, Luyten b orbits within the habitable zone of Luyten's Star just 12.2 light years away. At 11 light-years away, a second closest planet, Ross 128 b, was announced in November 2017 following a decade's radial velocity study of relatively "quiet" red dwarf star Ross 128. At 1.35 Earth's mass is it roughly Earth sized and likely rocky in composition. Discovered in March 2018, K2-155d is about 1.64 time the radius of Earth, is likely rocky and orbits in the habitable zone of its red dwarf star 203 light years away.

Epoch (astronomy)

J2000J2000.0epoch
This may be related to the fact that the Egyptians regulated their year by the heliacal rising of the star Sirius, a phenomenon which occurs in the morning just before dawn.

Neutron star

neutron starsStellar spin-downdying star
Some of the closest known neutron stars are RX J1856.5−3754, which is about 400 light-years from Earth, and PSR J0108−1431 at about 424 light years. RX J1856.5-3754 is a member of a close group of neutron stars called The Magnificent Seven. Another nearby neutron star that was detected transiting the backdrop of the constellation Ursa Minor has been nicknamed Calvera by its Canadian and American discoverers, after the villain in the 1960 film The Magnificent Seven. This rapidly moving object was discovered using the ROSAT/Bright Source Catalog.

Kapteyn's Star

Kapteyn
Kapteyn's Star is a class M1 red subdwarf about 12.76 light years from Earth in the southern constellation Pictor; it is the closest halo star to the Solar System. With a magnitude of nearly 9 it is visible through binoculars or a telescope. Its diameter is 30% of the Sun's, but its luminosity just 1.2% that of the Sun. It may have once been part of the globular cluster Omega Centauri, itself a likely dwarf galaxy swallowed up by the Milky Way in the distant past. The discovery of two planets — Kapteyn b and Kapteyn c — was announced in 2014. Attention was first drawn to what is now known as Kapteyn's Star by the Dutch astronomer Jacobus Kapteyn in 1898.

Beta Crateris

β Crtβ Crateris
It is visible to the naked eye with an apparent visual magnitude of 4.46. Based upon an annual parallax shift of 9.59 mas as seen from Earth, it is located around 340 light years from the Sun. This is an astrometric binary star system with an orbital period of 6.0 years and a projected separation of 8.3 AU. The orbit has an estimated semimajor axis of 9.3 AU. The primary, component A, is listed as an A-type giant star with a stellar classification of A2 III. However, Houk and Smith-Moore (1988) give a main sequence classification of A1 V, while Abt and Morrell (1995) list it as a subgiant star with a class of A2 IV.

Exoplanet

extrasolar planetexoplanetsplanet
Later that same year, the colors of several other exoplanets were determined, including GJ 504 b which visually has a magenta color, and Kappa Andromedae b, which if seen up close would appear reddish in color. The apparent brightness (apparent magnitude) of a planet depends on how far away the observer is, how reflective the planet is (albedo), and how much light the planet receives from its star, which depends on how far the planet is from the star and how bright the star is. So, a planet with a low albedo that is close to its star can appear brighter than a planet with high albedo that is far from the star.

Pollux (star)

PolluxBeta Geminorumβ Gem
At an apparent visual magnitude of 1.14, Pollux is the brightest star in its constellation, even brighter than its neighbor Castor (α Geminorum). Pollux is 6.7 degrees north of the ecliptic, too far north to be occulted by the moon and planets, but in the distant future it will be close enough. Parallax measurements by the Hipparcos astrometry satellite place Pollux at a distance of about 33.78 ly from the Sun. The star is larger than the Sun, with about two times its mass and almost nine times its radius. Once an A-type main sequence star, Pollux has exhausted the hydrogen at its core and evolved into a giant star with a stellar classification of K0 III.

Redshift

red shiftzred-shift
[[Image:Distance compared to z.png|thumb|400px|Plot of distance (in giga light-years) vs. redshift according to the Lambda-CDM model. d (in solid black) is the comoving distance from Earth to the location with the Hubble redshift z while ct (in dotted red) is the speed of light multiplied by the lookback time to Hubble redshift z . The comoving distance is the physical space-like distance between here and the distant location, asymptoting to the size of the observable universe at some 47 billion light-years.

Pi Mensae

π Men
The apparent magnitude is 5.67, which can be visible to the naked eye in exceptionally dark, clear skies. It is nearly 60 ly away. The star is slightly larger than the Sun in terms of mass, size, luminosity, temperature, and metallicity and is about 730 million years younger. It hosts two planets. On October 15, 2001, an extrasolar planet was found orbiting the star. Pi Mensae b is one of the most massive planets ever discovered, and has a very eccentric orbit that takes approximately 2,151 days (5.89 years) to complete.

Beta Serpentis

β Serβ SerpentisBeta
It is visible to the naked eye with a combined apparent visual magnitude of +3.65. Based upon an annual parallax shift of 21.03 mas as seen from Earth, it is located around 155 light years from the Sun. The system is a member of the Ursa Major Moving Group. The visual magnitude +3.68 primary, component A, is either an ordinary A-type main-sequence star or somewhat evolved subgiant with a stellar classification of A2 V or A2 IV, respectively. The star is about 267 million years old with nearly double the mass of the Sun. It is spinning rapidly with a projected rotational velocity of 207 km/s. The secondary component, visual magnitude 9.7 B, lies at an angular separation of 30.6 arc seconds.

Tau Ceti

Tau Ceti eτ CetTau Ceti f
It can be seen with the unaided eye with an apparent magnitude of 3.5. As seen from Tau Ceti, the Sun would be in the northern hemisphere constellation Boötes with an apparent magnitude of about 2.6. The name "Tau Ceti" is the Bayer designation for this star, established in 1603 as part of German celestial cartographer Johann Bayer's Uranometria star catalogue: it is "number T" in Bayer's sequence of constellation Cetus. In the catalogue of stars in the Calendarium of Al Achsasi al Mouakket, written at Cairo about 1650, this star was designated Thālith al Naʽāmāt (ثالث النعامات - thālith al-naʽāmāt), which was translated into Latin as Tertia Struthionum, meaning the third of the ostriches.