Star Porrima, known as Gamma (γ) Virginis, is a binary star in the constellation Virgo with an orbital period of 169 years.

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Back in the early 2000s the apparent separation of the two components was so small that it was virtually impossible to split them.

Now that situation has improved somewhat and the two similarly bright stars (mag. +3.6 and mag. +3.7), appear separated by a little over 4 arcseconds.

Constellation Virgo, showing the locations of Spica and Porrima. Credit: Hubl Bernhard, CEDIC Team / CCDGuide.com
Constellation Virgo, showing the locations of Spica and Porrima. Credit: Hubl Bernhard, CEDIC Team / CCDGuide.com

The binary pair is made of two similar main sequence stars both about 38 lightyears from Earth.

Shining at mag. +2.7, Porrima can be seen with the naked eye in the ‘bowl of Virgo’, but to resolve it and see the two individual stars, you’ll need a telescope.

Lunar occultations of Porrima

From the centre of the UK, Porrima is occulted at 05:52 UT on 19 March as the sky is brightening due to the approach of dawn. Credit: Pete Lawrence
Credit: Pete Lawrence

Because Porrima lies close to the ecliptic - the imaginary line followed by the Sun across the sky - it can often be seen in a lunar occultation, whereby it disappears behind the Moon from our perspective on Earth.

One such occultation occurred on 19 March 2022 and was viewable from the UK.

Then, on the morning of 13 May 2022, the 87%-lit waxing gibbous Moon occulted Porrima.

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This guide originally appeared in the March 2022 issue of BBC Sky at Night Magazine.

Authors

Pete Lawrence, astronomer and BBC The Sky at Night presenter.
Pete LawrenceAstronomer and presenter

Pete Lawrence is an experienced astronomer and astrophotographer, and a presenter on BBC's The Sky at Night.