{"id":41648,"date":"2023-02-14T14:43:17","date_gmt":"2023-02-14T14:43:17","guid":{"rendered":"https:\/\/c01.purpledshub.com\/bbcskyatnight\/?post_type=purple_issue&p=41648"},"modified":"2023-02-16T09:20:27","modified_gmt":"2023-02-16T09:20:27","slug":"star-of-the-month-18","status":"publish","type":"post","link":"https:\/\/c01.purpledshub.com\/bbcskyatnight\/2023\/02\/14\/star-of-the-month-18\/","title":{"rendered":"Star of the month"},"content":{"rendered":"\n

Zosma, the rump of Leo the Lion <\/p>\n\n

\"\"
Easy to see with the naked eye, Zosma sits in an unglamorous spot at the foot of Leo\u2019s tail <\/figcaption><\/figure><\/div>\n\n

Zosma is a mag. +2.5 star marking the point on the top of Leo\u2019s body that connects to the Lion\u2019s tail. This is the IAUapproved name for Delta (\u03b4) Leonis, derived from the Greek word for \u2018girdle\u2019. However, its Arabic name, Dhur, meaning \u2018the lion\u2019s back\u2019, might have been more appropriate. <\/p>\n\n

It\u2019s a main sequence star with a spectral classification A4 V: a white (A4) main sequence dwarf (V). It is 2.1 times larger than the Sun and 15 times more luminous. Unlike the Sun\u2019s leisurely rotation velocity of 2km\/s, Zosma rotates with a projected rotational velocity of 180 km\/s. This is uncorrected for the inclination of the rotational axis; correct the angle so the axis would be at right angles to our line of sight and the speed would be around 280km\/s. As a consequence, up close Zosma would show a noticeable equatorial bulge. <\/p>\n\n

Parallax measurements put the star at a distance of 58.4 lightyears from the Sun. Direct measurements of Zosma\u2019s proper motion \u2013 direction and velocity through space \u2013 show it is probably part of a collection of stars known as the Ursa Major Moving Group. This group would have formed in the same location together around 500 million years ago. <\/p>\n\n

Zosma\u2019s hydrogen fusion period is around 1 billion years and consequently we know the star is about halfway through its \u2018normal\u2019 life cycle. At the end of this cycle its helium core will shrink and its outer layers expand, causing it to become an orange giant.<\/span><\/p>\n\n

PHOTO: PETE LAWRENCE<\/p>\n","protected":false},"excerpt":{"rendered":"

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