HR 7578

HR 7578 has two main components: the first component - A is a double star with an apparent magnitude of +6.33 ^{m [7]} and spectral class K ^[6] . The second component, B, is a star with an apparent magnitude of +10.68 ^{m [7]} and a spectral class M ^[9] . They rotate around each other at a distance of at least 580 AU ^[1] .

HR 7578 is a variable of type BY Dragon ^[4] . This is a class of variable stars, the variability of which comes from star spots, similar to solar spots on the surface of stars. The brightness of the star during rotation changes by 0.07 ^{m [4]} . The period of variability lasts 3.2 days and, apparently, is equal to the period of rotation of the star ^[11] .

HR 7578 is a fairly young system: it may be older than the Pleiades , but perhaps younger than the Hyades ^[5] . The age of the star is very uncertain and ranges from 0.5 to 2 billion years ^[5] .

Component A

HR 7578A consists of 2 stars: HR 7578Aa and HR 7578Ab, which rotate around each other with a period of at least 46.816103 ± 0.000057 days. or 0 128 years ^[14] . (For comparison, the period of revolution of Mercury around the Sun is 87.9 days. ) The eccentricity of the orbit is very large - 0.68640 ± 0.00028 ^[14] , i.e. about the same as Nereida . The argument of the pericenter (ω) of the binary system, i.e. the angle between the directions from the attracting center to the ascending node of the orbit and to the pericenter (closest to the attracting center point of the orbit of the celestial body) is 241.168 ± 0.046 ° ^[14] .

Both stars have a minimum mass of 0.85 ± 0.03${\displaystyle {\mathrm{<span\; class="nowrap"><span><span\; class="mwe-math-element"><span\; class="mwe-math-mathml-inline\; mwe-math-mathml-a11y"\; style="display:\; none;">M</span></span></span></span>}}_{<span\; class="nowrap"><span><span\; class="mwe-math-element"><span\; class="mwe-math-mathml-inline\; mwe-math-mathml-a11y"\; style="display:\; none;">⨀</span></span></span></span>}}$ {\ displaystyle M _ {\ bigodot}}   ^[5] . Also, both stars are almost half dimmer than our Sun , their luminosity is 0.59${\displaystyle {\mathrm{<span\; class="nowrap"><span><span\; class="mwe-math-element"><span\; class="mwe-math-mathml-inline\; mwe-math-mathml-a11y"\; style="display:\; none;">L</span></span></span></span>}}_{<span\; class="nowrap"><span><span\; class="mwe-math-element"><span\; class="mwe-math-mathml-inline\; mwe-math-mathml-a11y"\; style="display:\; none;">⨀</span></span></span></span>}}$ {\ displaystyle L _ {\ bigodot}}   ^[2] . In order for a planet similar to our Earth to receive about the same amount of energy as it receives from the Sun, it would have to be placed at a distance of 0.77 AU , i.e. a little further than the place where Venus is located in the solar system , whose semi-major axis is 0.72 AU ^[2] .

Both stars in the HR 7578A system are dwarfs of the spectral class K3V ^[6] , which indicates that the hydrogen in the star’s core serves as nuclear “fuel”, that is, the star is in the main sequence . A star radiates energy from its external atmosphere at an effective temperature of about 4774 K ^[6] , which gives them a characteristic orange color.

Both stars in the HR 7578A system are unusually rich in metals, showing a large amount of cyanide and sodium in their spectra ^[5] .

Component B

HR 7578 also has a companion with a common movement of its own - 2MASS J19542064-2356398 ^[9] . This is a star of the spectral class M5V, i.e. red dwarf ^[9] .

The discoverer of stars in the HR 7578 system is considered to be J. Herschel , who resolved stars until 1871 (the year of his death). The star herself entered the catalogs under the name HJ 2904, after his death in 1877 . Then, a second satellite was discovered in the star, which has been observed since 1954 . According to the Washington catalog of visual binary stars , the parameters of these components are given in the table ^{[15] [7]} :

Summarizing all the information about the star, we can say that the star has a satellite - HR 7578 B and that the stars move together in space, i.e. stars are not just in line of sight, but are gravitationally related to each other. Unfortunately, not a single orbit has been calculated exactly, which does not allow verification of stellar masses.

In the middle of the 20th century , information appeared about the third component - HR 7578 C, which has a magnitude of visible magnitude of 16.0 ^m and is 41.6 " distant from the main component ^[7] , but the pack does not have independent confirmation and it is possible that this star is simply optically double, that is, the star may simply be on the line of sight and is not gravitationally related to HR 7578.

The following stellar systems are within 20 light-years ^[16] of the HR 7578 star (included only: the closest star, the brightest (<6.5 ^m ) and noteworthy stars). Their spectral classes are shown against the background of the colors of these classes (these colors are taken from the names of the spectral types and do not correspond to the observed colors of stars):

Near the star, at a distance of 20 light-years , there are also about 25 red , orange and yellow dwarfs of the spectral class G, K and M, as well as 4 white dwarfs that are not on the list.

Comments

Sources

  19 ^h 54 ^m 17.74528 ^s , −23 ° 56 ′ 27.86298 ″