နှစ်လုံးတွဲ ကြယ်

ကမ္ဘာပေါ်မှ အဝေးကြည့်မှန်ပြောင်းဖြင့် ကြည့်ပါက တစ်လုံးနှင့် တစ်လုံး နီးကပ်စွာ တည်ရှိနေသည်ဟု မြင်ရသော ကြယ်စုံတွဲကို နှစ်လုံးတွဲ ကြယ်ဟု ခေါ်သည်

ဤကဲ့သို့ မြင်ရခြင်းမှာ အမှန်တကယ် နီးကပ်စွာ တည်ရှိ၍ အချင်းချင်း လှဲ့ပတ်နေသော ကြယ်စုံတွဲများ ဖြစ်နိုင်သလို နီးကပ်သည်ဟု ထင်ရသော သီးခြားစီတည်ရှိနေသည့် ကြယ်နှစ်လုံးလည်းဖြစ်နိုင်သည်။ ကြယ်စုံတွဲများမှာ ၎င်းတို့၏ သွားလာလှည့်ပတ်ပုံကိုကြည့်၍ ဒြပ်သားထု တိုင်းတာခြင်းနှင့် အခြားအချက်အလက်များ လေ့လာရာတွင် အလွန် အရေးကြီးသည်။

Since the beginning of the 1780s, both professional and amateur double star observers have telescopically measured the distances and angles between double stars to determine the relative motions of the pairs. If the relative motion of a pair determines a curved arc of an orbit, or if the relative motion is small compared to the common proper motion of both stars, it may be concluded that the pair is in mutual orbit as a binary star. Otherwise, the pair is optical. Multiple stars are also studied in this way, although the dynamics of multiple stellar systems are more complex than those of binary stars.

There are three types of paired stars:

• Optical Doubles are unrelated stars that appear close together through chance alignment with Earth.
• Visual Doubles are stars whose binary status was deduced through more esoteric means, such as occultation (eclipsing binaries), spectroscopy (spectroscopic binaries), or anomalies in proper motion. (astrometric binaries).
• Visual Binaries are gravitationally-bound stars that are separately visible with a telescope.

Conceptually, there is no difference between the two visual categories, and improvements in telescopes can shift previously double stars into visual binaries, as happened with Polaris in 2006. Thus it is only the inability to telescopically observe or detect orbital motion in the visual double stars that differentiates these two groups.

သမိုင်း

ခုနစ်စင်ကြယ်အတွင်းရှိ မီဆာကြယ်(Mizar, in Ursa Major)ကို နှစ်လုံးတွဲကြယ်ဖြစ်ကြေင်း Benedetto Castelli and Galileo တို့မှ ပထမဆုံး ရှာဖွေတွေ့ရှိ့ခဲ့ကြသည်။ထို့နောက်  Robert Hooke မှ အခြားနှစ်လုံးတွဲ ကြယ်များကို ခြာဖွေတွေ့ရှိ့ခဲ့သည်။  ၎င်းတွေ့ရှိမူများ နောက်တွင်တော့ ညကောင်းကင်၏ နှစ်လုံးတွဲ ကြယ်များကို ဆက်တိုက်ရှာဖွေခဲ့ကြသည်။ မြောက်ဘက်ကမ္ဘာခြမ်းတွင် အလင်းအား ၉ထက်ပိုသော ကြယ်များအားလေ့လာခဲ့ရာ ၁၈ လုံးတွင် ကြယ်တစ်လုံးမှာ နှစ်လုံးတွဲ ကြယ် ဖြစ်ကြောင်း တွေ့ရှိ့ရသည်။  ope.

The unrelated categories of optical doubles and true binaries are lumped together for historical and practical reasons. When Mizar was found to be a binary, it was quite difficult to determine whether a double star was a binary system or only an optical double. Improved telescopes, spectroscopy, and photography are the basic tools used to make the distinction. After it was determined to be a visual binary, Mizar's components were found to be spectroscopic binaries themselves.

နှစ်လုံးတွဲ ကြယ်များအား လေ့လာခြင်း

Astronomers have also mistakenly reported observations of a double star in place of J 900 and a faint star in the constellation of Gemini.

Visual double stars are defined as double stars which are visible in an optical telescope. This is the majority of all known double stars. If visual doubles show similar properties, such as similar proper motion through space, trigonometric parallaxes, or radial velocities, this is evidence that they are gravitationally attached and form a binary system; in this case, the visual double star is called a visual binary.

Observation of visual double stars by visual measurement will yield the separation, or angular distance, between the two component stars in the sky and the position angle. The position angle specifies the direction in which the stars are separated and is defined as the bearing from the brighter component to the fainter, where north is 0°. These measurements are called measures. In the measures of a visual binary, the position angle will change progressively and the separation between the two stars will oscillate between maximum and minimum values. Plotting the measures in the plane will produce an ellipse. This is the apparent orbit, the projection of the orbit of the two stars onto the celestial sphere; the true orbit can be computed from it. Although it is expected that the majority of catalogued visual doubles are visual binaries, orbits have been computed for only a few thousand of the over 100,000 known visual double stars.

Distinction between binary stars and other double stars

Visual double stars may be distinguished from binary stars by observing their relative motion. If the motion is part of an orbit, or if the stars have similar radial velocities or the difference in their proper motions is small compared to their common proper motion, the pair is probably physical. When observed over a short period of time, the components of both optical doubles and long-period visual binaries will appear to be moving in straight lines; for this reason, it can be difficult to distinguish between these two possibilities.

Designations

Some bright visual double stars have a Bayer designation. In this case, the components may be denoted by superscripts. An example of this is α Crucis (Acrux), whose components are α¹ Crucis and α² Crucis. Since α¹ Crucis is a spectroscopic binary, this is actually a multiple star. Superscripts are also used to distinguish more distant, physically unrelated, pairs of stars with the same Bayer designation, such as α^1,2 Capricorni (separated by 0.11°), ξ^1,2 Centauri (separated by 0.66°), and ξ^1,2 Sagittarii (separated by 0.46°.) These optical pairs are resolvable by the naked eye.

Apart from these pairs, the components of a double star are generally denoted by the letters A (for the brighter, primary, star) and B (for the fainter, secondary, star) appended to the designation, of whatever sort, of the double star. For example, the components of α Canis Majoris (Sirius) are α Canis Majoris A and α Canis Majoris B (Sirius A and Sirius B); the components of 44 Boötis are 44 Boötis A and 44 Boötis B; the components of ADS 16402 are ADS 16402A and ADS 16402B; and so on. The letters AB may be used together to designate the pair. In the case of multiple stars, the letters C, D, and so on may be used to denote additional components, often in order of increasing separation from the brightest star, A.

Double star discoverer designations

Discoverer	Traditional code	WDS code
Brisbane Observatory	Brs0	BSO
S. W. Burnham	β	BU
James Dunlop	Δ	DUN
William Herschel	H I, II, etc.	H 1, 2, etc.
N. Lacaille	Lac	LCL
F. G. W. Struve	Σ	STF
Struve Appendix Catalogue I	Σ I	STFA
Struve Appendix Catalogue I	Σ II	STFB
Otto Struve	OΣ	STT
Pulkova Appendix Catalogue	OΣΣ	STTA

Visual doubles are also designated by an abbreviation for the name of their discoverer followed by a catalogue number unique to that observer. For example, the pair α Centauri AB was discovered by Father Richaud in 1689, and so is designated RHD 1. Other examples include Δ65, the 65th double discovered by James Dunlop, and Σ2451, discovered by F. G. W. Struve.

Examples

Artist's impression of the discs around the young stars HK Tauri A and B.

Visual binaries

• Acrux
• Alpha Centauri
• Capella
• p Eridani
• Polaris
• Procyon
• Sirius

Optical doubles

• Alpha¹ and Alpha² Capricorni
• Theta Muscae and Theta Muscae B
• Eta¹ and Eta² Coronae Australis
• Kappa¹ and Kappa² Coronae Australis
• Winnecke 4 (Messier 40)

Uncertain

• Alpha Centauri system (AB) and Proxima Centauri (thus α Cen C): association is generally considered a physically connected system
• Castor system (Aa/Ab/Ba/Bb) and YY Geminorum (thus Castor Ca/Cb) is generally considered a physical system
• Mizar system (Aa/Ab/Ba/Bb) and Alcor (itself a binary, thus Mizar Ca/Cb, though generally not considered physical until 2009)