Proper motion - proper motion

Japanese: 固有運動 - こゆううんどう
Proper motion - proper motion

Stars are thought to never change their position on the celestial sphere, but in fact their position (i.e. the direction from which we view the star) appears to change, albeit very slightly. This change includes the annual change due to annual parallax and annual aberration, but the change in position due to the spatial motion of the star itself, excluding these, is called the proper motion of the star. More precisely, this refers to the change in position that is thought to be due to the motion of the star itself, remaining after subtracting from the annual change in the celestial coordinates of the star (for example, right ascension and declination) the changes in coordinate values ​​due to fluctuations in the coordinate system such as precession and nutation, and the changes due to the motion of the Earth such as annual parallax and annual aberration. In other words, proper motion is the change in the direction (position movement) of the star due to the tangential part (the component of motion perpendicular to the line of sight) of the spatial motion of the star relative to the Earth (strictly speaking, the Sun). The speed of a star relative to the Sun (Earth) is fast, ranging from 10 to several tens of kilometers per second, but because the star is so far away, its proper motion is generally extremely small, less than a few arcseconds per year (a second is a unit of angle that is 1/1,296,000th of a circumference (360 degrees)). The actual tangential speed of a star cannot be determined solely by the magnitude of its proper motion; it can only be calculated by multiplying the proper motion by its distance.

The first person to discover proper motion was Harry of England in 1718. He discovered the proper motion of stars because the positions of three stars, Sirius, Procyon, and Arcturus, at that time were different from the positions observed in the Greek era.

The proper motions of stars provide extremely important information in astronomy, such as the distance, motion, structure, and evolution of star clusters, and the rotation, structure, scale, and evolution of our galaxy.

[Naoaki Owaki]

"Astronomy on a Cloudy Day -- Astronomical Information Consultation Room," edited by Ryo Ikeuchi, So Kinoshita, Yukio Niimi, and Shiro Nishimura (1988, Maruzen) " "Stars and Constellations," revised edition, supervised by Genichiro Hori, Etsuko Kobayashi, and Naoto Kimura (1998, Gakken)"

[References] | Aberration | Stars | Precession | Parallax | Nutation | Harry
Proper motion
©Shogakukan ">

Proper motion


Source: Shogakukan Encyclopedia Nipponica About Encyclopedia Nipponica Information | Legend

Japanese:

恒星は天球上でまったく位置を変えないと思われているが、実は非常にわずかであるが位置(すなわち恒星を見る方向)が変わっていくように見える。この変化のなかには、年周視差および年周光行差による1年周期の変化も含まれるが、それを除いた恒星自体の空間運動による位置変化を恒星の固有運動とよぶ。これをより厳密にいえば、恒星の天球座標(たとえば赤経・赤緯)の年変化から、歳差・章動など座標系の変動による座標値の変化、および年周視差や年周光行差など地球の運動に起因する変化を差し引いた残りで、恒星自体の運動に起因すると思われる位置変化をさす。すなわち固有運動は、地球(厳密には太陽)に対する恒星の空間運動のうちの接線部分(視線方向に直角な方向の運動成分)による恒星の方向の変化(位置の移動)である。太陽(地球)に対する恒星の運動速度は毎秒10~数十キロメートルと速いが、恒星がきわめて遠くにあるため、固有運動は一般に年間数秒角(秒は円周=360度の129万6000分の1の角度を表す単位)以下ときわめて小さい。恒星の実際の接線運動速度は、固有運動の大小だけでは決められず、固有運動にその距離を乗じて初めて求められる。

 固有運動を初めて発見したのはイギリスのハリーで、1718年のことである。彼は、シリウス、プロキオン、アークトゥルスの三つの星のその当時の位置が、ギリシア時代に観測された位置よりずれていることから恒星の固有運動をみいだしたのであった。

 なお、恒星の固有運動は、天文学上きわめて重要な情報を与える。たとえば、星団の距離・運動・構造や進化、さらにわが銀河系の回転や、その構造・規模、ひいてはその進化などの解明に、不可欠な資料となるものである。

[大脇直明]

『池内了・木下宙・新美幸夫・西村史朗編『くもった日の天文学――天文情報相談室』(1988・丸善)』『堀源一郎・小林悦子・木村直人指導・著『星・星座』新訂版(1998・学習研究社)』

[参照項目] | 光行差 | 恒星 | 歳差 | 視差 | 章動 | ハリー
固有運動
©Shogakukan">

固有運動


出典 小学館 日本大百科全書(ニッポニカ)日本大百科全書(ニッポニカ)について 情報 | 凡例

<<:  Proper time - Koyuji (English spelling)

>>:  Goyu - Goyu

Recommend

Neo-Confucianism

...In later times, in addition to these names, th...

Paul Mauriat

French composer, arranger, conductor, and pianist...

Ribbon grass

...Reed canary grass is an important pasture gras...

Gyokuro - Gyokuro

This is the highest quality Japanese green tea. I...

Ichikawa Danjuro (first generation)

...An actor like Murayama Heijuro I, who played b...

Okudzhava (English spelling) Bulat Shalvovich Okudzhava

Russian poet. Born in Moscow. After serving as a ...

Nieuwe Gids (English spelling)

However, it cannot be denied that the Netherlands...

Tatami - Tatami

A flooring material for use on the floor of a roo...

Pelecanus rufescens (English spelling) Pelecanusrufescens

…[Maki Sachiko]. . . *Some of the terminology tha...

Battle of Ishiyama

This was a battle that lasted for 11 years from 15...

《Sea》

...But trying to force his individual genius, whi...

Pinus monticola (English spelling) Pinus monticola

… [Makoto Nishida]. … *Some of the terminology th...

Flow with eddies - Flow with eddies

…The speed of all motions other than translationa...

Household items - Oimono

It is a type of Joruri and Kabuki script. It is a...

Sleepwalking - Sleepwalking

During deep sleep known as non-REM sleep, the pat...