{"id":41049,"date":"2023-02-01T10:32:35","date_gmt":"2023-02-01T10:32:35","guid":{"rendered":"https:\/\/www.skyatnightmagazine.com\/?p=115748"},"modified":"2023-02-01T10:32:26","modified_gmt":"2023-02-01T10:32:26","slug":"a-guide-to-star-mirach-beta-%ce%b2-andromedae","status":"publish","type":"rss_feed","link":"https:\/\/c01.purpledshub.com\/bbcskyatnight\/rss_feed\/a-guide-to-star-mirach-beta-%ce%b2-andromedae\/","title":{"rendered":"A guide to star Mirach (Beta (\u03b2) Andromedae)"},"content":{"rendered":"

Mirach is 197 lightyears away and 1,900 times more luminous than the Sun. <\/p>

By Pete Lawrence\n \t\t<\/p>

Published: Wednesday, 01 February 2023 at 12:00 am<\/p>

\n\n

Mirach (Beta (\u03b2<\/span>) Andromedae) is in the constellation Andromeda and is found halfway along Andromeda\u2019s body, between Alpheratz <\/span>(Alpha (\u03b1<\/span>) Andromedae) and Almach (Gamma (\u03b3<\/span>) Andromedae).<\/p>\n

The name Mirach probably results from a corruption of mi\u2019zar, meaning girdle or waist-cloth.<\/p>\n

\"""\"<\/source><\/source><\/source><\/source><\/source><\/source><\/source><\/source><\/source><\/source><\/source><\/source><\/source><\/source><\/picture><\/div>
Credit: Pete Lawrence<\/span><\/figcaption><\/div>\n

Mirach and Alpheratz have the same average brightness of mag. +2.06, but look markedly different because Mirach is a red giant and Alpheratz a hot blue star.\u00a0<\/span><\/p>\n

Mirach is 197 lightyears away and 1,900 times more luminous than the Sun.<\/p>\n

Its radius is estimated at around 0.4 AU, or 85 times larger than the Sun, giving it a circumference equivalent to the orbit of Mercury.<\/p>\n

As the star is approaching the end of its life its core probably consists of helium or carbon.<\/p>\n

As is common with old red giants, Mirach\u2019s light is inconstant, and it\u2019s classed as a semi-regular variable star<\/a>.<\/p>\n

The changes in brightness are small, ranging between +2.01 to +2.10.<\/p>\n

Like many stars, Mirach is not alone and has a 14th-magnitude main-sequence companion that is 60,000 times dimmer than Mirach itself.<\/p>\n

Their orbits bring them physically to within 40 times the Sun-Pluto distance of one another.<\/p>\n

From Mirach the companion would appear as bright as Venus appears from Earth.<\/p>\n

Mirach would appear 120 times brighter than the full Moon<\/a> from the companion.\u00a0<\/span><\/p>\n

Through the eyepiece Mirach has an additional deep sky companion in the form of the isolated dwarf lenticular galaxy, NGC 404.<\/p>\n

The apparent separation between star and galaxy is just 7 arcminutes giving NGC 404 the appearance of a lens flare caused by Mirach.<\/p>\n

Known informally as Mirach\u2019s Ghost, one of the biggest hurdles to seeing it is the brightness of Mirach itself.<\/p>\n

This guide originally appeared in the September 2017 issue of <\/strong><\/em>BBC Sky at Night Magazine<\/strong>.<\/strong><\/em><\/p> <\/body><\/html>\n

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