{"id":42407,"date":"2023-03-08T13:33:05","date_gmt":"2023-03-08T13:33:05","guid":{"rendered":"https:\/\/www.skyatnightmagazine.com\/?p=116768"},"modified":"2023-03-08T14:32:28","modified_gmt":"2023-03-08T14:32:28","slug":"how-to-see-star-zosma-the-rump-of-leo-the-lion","status":"publish","type":"rss_feed","link":"https:\/\/c01.purpledshub.com\/bbcskyatnight\/rss_feed\/how-to-see-star-zosma-the-rump-of-leo-the-lion\/","title":{"rendered":"How to see star Zosma, the rump of Leo the Lion"},"content":{"rendered":"

Easy to see with the naked eye, Zosma sits in an unglamorous spot at the foot of Leo\u2019s tail. <\/p>

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

Published: Wednesday, 08 March 2023 at 12:00 am<\/p>

\n\n

Zosma is a mag. +2.5 star marking the point on the top of the constellation Leo<\/a>\u2019s body that connects to the Lion\u2019s tail.<\/p>\n

This is the IAU-approved name for Delta (\u03b4<\/span>) Leonis, derived from the Greek word for \u2018girdle\u2019.<\/p>\n

However, its Arabic name, Dhur, meaning \u2018the lion\u2019s back\u2019, might have been more appropriate.<\/p>\n

Zosma is 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.<\/p>\n

Unlike the Sun\u2019s leisurely rotation velocity of 2km\/s, Zosma rotates with a projected rotational velocity of 180 km\/s.<\/p>\n

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.<\/p>\n

As a consequence, up close Zosma would show a noticeable equatorial bulge.<\/p>\n

Parallax measurements put the star at a distance of 58.4 lightyears from the Sun.<\/p>\n

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.<\/p>\n

This group would have formed in the same location together around 500 million years ago.<\/p>\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.<\/p>\n

At the end of this cycle its helium core will shrink and its outer layers expand, causing it to become an orange giant.<\/p>\n

This guide originally appeared in the March 2023 issue of <\/strong><\/em>BBC Sky at Night Magazine<\/strong>.<\/strong><\/em><\/p> <\/body><\/html>\n