{"id":25259,"date":"2021-10-21T00:00:00","date_gmt":"2021-10-21T00:00:00","guid":{"rendered":"https:\/\/c01.purpledshub.com\/bbcskyatnight\/?post_type=purple_issue&p=25259"},"modified":"2021-10-21T12:32:05","modified_gmt":"2021-10-21T12:32:05","slug":"the-sky-guide-challenge-2","status":"publish","type":"post","link":"https:\/\/c01.purpledshub.com\/bbcskyatnight\/2021\/10\/21\/the-sky-guide-challenge-2\/","title":{"rendered":"The sky guide challenge"},"content":{"rendered":"\n

Can you separate bright Capella\u2019s two true companion stars from the impostors?<\/p>\n\n

\"\"
Locate Capella H (and the more tricky Capella L) by finding it mid-way between two field stars, as shown in the locator chart (right)<\/figcaption><\/figure><\/div>\n\n

Capella (Alpha (\u03b1) Aurigae) rides high across the winter sky, a yellow beacon at the top of the misshapen pentagon that represents the main part of the constellation of Auriga, the Charioteer. Look at Capella through a telescope and you\u2019ll see numerous other stars nearby. These are listed in the <\/span>Washington <\/em>Double <\/em>Star <\/em>Catalogue <\/em>as Capella A (the main star) through to Capella R. Of these, only two are known to be true physical companions, Capella H and Capella L. The others appear close simply because they occupy the same line of sight as Capella A. This month\u2019s challenge is to locate Capella H and possibly Capella L.<\/span><\/p>\n\n

The main star, Capella A, is a spectroscopic binary, Aa and Ab, two yellow giant suns in a 104-day mutual orbit around one another. Their mean orbital distance is around 0.74 AU, which is approximately the distance between Venus and the Sun. At a distance of 42.8 lightyears, amateurs can\u2019t see these stars separated, and they appear as one.<\/span><\/p>\n\n

Capella H and L are different and are viable targets for amateur telescopes. The stars are a binary pair of red dwarf stars gravitationally linked to Capella Aa and Ab, thus forming a quadruple system. While Capella A is easy to find with any size of telescope, Capella H needs at least 150mm of aperture and Capella L a 250mm scope. A large instrument over 300mm in aperture is recommended to separate the pair convincingly<\/p>\n\n

Capella H and L appear very close to one another in the night sky, separated by just 3 arcseconds. They sit 12 arcminutes southeast of Capella A, between two field stars, mag. +10.0 TYC 3358-2785-1 and mag. +8.7 TYC 3358-3023-1. This makes Capella H easier to locate. Start with a low- to mid-power eyepiece giving you a field of view at least 30 arcminutes across; that\u2019s roughly the apparent diameter of the Moon. Centre on bright Capella A, then identify mag. +10.2 TYC 3358-3142-1, 1.7 arcminutes southeast of Capella A.<\/span> This is a key navigational star for two reasons. Its brightness is the same as mag. +10.2 Capella H and if you can see easy-to-find TYC 3358-3142-1, you should be able to see H. Secondly, a line from Capella A through TYC 3358-3142-1 points to TYC 3358-2785-1, mentioned earlier.<\/p>\n\n

Once you\u2019ve located TYC 3358-2785-1 you should be able to identify brighter TYC 3358-3023-1 quite easily. There are several faint stars between TYC 3358- 2785-1 and TYC 3358-3023-1, Capella H being the brightest one, roughly mid-way between them. Once identified, increase magnification to see whether you can see a southern \u2018extension\u2019 to Capella H. If you can, you\u2019ve located Capella H\u2019s close binary companion, mag. +13.7 Capella L. Imaging the pair really helps reveal the distinct orange hue of this red dwarf binary.<\/p>\n","protected":false},"excerpt":{"rendered":"

Can you separate bright Capella\u2019s two true companion stars from the impostors?<\/p>\n","protected":false},"author":24,"featured_media":25258,"comment_status":"closed","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"ub_ctt_via":"","purple_page_number":"55","purple_custom_meta_purple_page_number":"55","purple_seq_number":"1","purple_custom_meta_purple_seq_number":"1","purple_source_article":"article_55-1.xml","purple_custom_meta_purple_source_article":"article_55-1.xml","purple_source_issue":"November-2021","purple_custom_meta_purple_source_issue":"November-2021","purple_external_id":"November-2021-55-1","purple_custom_meta_purple_external_id":"November-2021-55-1","purple_issue_code":"|0000086546||","purple_custom_meta_purple_issue_code":"|0000086546||","purple_android_product":"com.im.skyatnight.198","purple_custom_meta_purple_android_product":"com.im.skyatnight.198","purple_ios_product":"com.im.skyatnight.198","purple_custom_meta_purple_ios_product":"com.im.skyatnight.198","purple_web_product":"","purple_custom_meta_purple_web_product":"","purple_publication_id":"075fab74-0a21-4201-866a-899d6c41c40c","purple_migrated":"","kt_blocks_editor_width":""},"categories":[22],"tags":[14],"featured_image_src":"https:\/\/c01.purpledshub.com\/uploads\/sites\/77\/2021\/10\/791d437c-889b-40a4-8861-cedc652cf0d5.jpg","author_info":{"display_name":"importmanagerhub@sprylab.com","author_link":"https:\/\/c01.purpledshub.com\/bbcskyatnight\/author\/importmanagerhubsprylab-com\/"},"acf":{"readingTimeMinutes":"3","apple_news_title":""},"uagb_featured_image_src":{"full":["https:\/\/c01.purpledshub.com\/uploads\/sites\/77\/2021\/10\/791d437c-889b-40a4-8861-cedc652cf0d5.jpg",2048,1463,false],"thumbnail":["https:\/\/c01.purpledshub.com\/uploads\/sites\/77\/2021\/10\/791d437c-889b-40a4-8861-cedc652cf0d5-150x150.jpg",150,150,true],"medium":["https:\/\/c01.purpledshub.com\/uploads\/sites\/77\/2021\/10\/791d437c-889b-40a4-8861-cedc652cf0d5-300x214.jpg",300,214,true],"medium_large":["https:\/\/c01.purpledshub.com\/uploads\/sites\/77\/2021\/10\/791d437c-889b-40a4-8861-cedc652cf0d5-768x549.jpg",768,549,true],"large":["https:\/\/c01.purpledshub.com\/uploads\/sites\/77\/2021\/10\/791d437c-889b-40a4-8861-cedc652cf0d5-1024x732.jpg",800,572,true],"1536x1536":["https:\/\/c01.purpledshub.com\/uploads\/sites\/77\/2021\/10\/791d437c-889b-40a4-8861-cedc652cf0d5-1536x1097.jpg",1536,1097,true],"2048x2048":["https:\/\/c01.purpledshub.com\/uploads\/sites\/77\/2021\/10\/791d437c-889b-40a4-8861-cedc652cf0d5.jpg",2048,1463,false]},"uagb_author_info":{"display_name":"importmanagerhub@sprylab.com","author_link":"https:\/\/c01.purpledshub.com\/bbcskyatnight\/author\/importmanagerhubsprylab-com\/"},"uagb_comment_info":0,"uagb_excerpt":"Can you separate bright Capella\u2019s two true companion stars from the impostors?","_links":{"self":[{"href":"https:\/\/c01.purpledshub.com\/bbcskyatnight\/wp-json\/wp\/v2\/posts\/25259"}],"collection":[{"href":"https:\/\/c01.purpledshub.com\/bbcskyatnight\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/c01.purpledshub.com\/bbcskyatnight\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/c01.purpledshub.com\/bbcskyatnight\/wp-json\/wp\/v2\/users\/24"}],"replies":[{"embeddable":true,"href":"https:\/\/c01.purpledshub.com\/bbcskyatnight\/wp-json\/wp\/v2\/comments?post=25259"}],"version-history":[{"count":2,"href":"https:\/\/c01.purpledshub.com\/bbcskyatnight\/wp-json\/wp\/v2\/posts\/25259\/revisions"}],"predecessor-version":[{"id":25653,"href":"https:\/\/c01.purpledshub.com\/bbcskyatnight\/wp-json\/wp\/v2\/posts\/25259\/revisions\/25653"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/c01.purpledshub.com\/bbcskyatnight\/wp-json\/wp\/v2\/media\/25258"}],"wp:attachment":[{"href":"https:\/\/c01.purpledshub.com\/bbcskyatnight\/wp-json\/wp\/v2\/media?parent=25259"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/c01.purpledshub.com\/bbcskyatnight\/wp-json\/wp\/v2\/categories?post=25259"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/c01.purpledshub.com\/bbcskyatnight\/wp-json\/wp\/v2\/tags?post=25259"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}