As darkness falls on the evening of Monday, 21 March, observers in the British Isles should look low to the east-southeast to see the 13-day-old waxing gibbous Moon just four degrees to the right of planet Jupiter. The pair lie in southern Leo and will easily fit within the same field of view of most binoculars. For scale, this view is about 40 degrees wide, or twice the span of an outstretched hand at arm’s length. The Moon’s size has been slightly enlarged for clarity. AN graphic by Ade Ashford.Jupiter reached opposition almost a fortnight ago, so the largest planet in the solar system is still very much centre stage in the March night sky. Currently shining at a conspicuous magnitude -2.5, Jupiter is therefore more than twice as bright as the brightest nighttime star, Sirius, sparkling low in the south as night falls.
In the telescope, Jupiter’s mighty equator presently spans 44.2 arcseconds in angular measure. This means that as seen through a telescope, a magnification of little more than 40x is required to enlarge it to the same size as the adjacent Moon appears to the unaided eye. At higher magnifications, and with good seeing, you will also see the planet’s Great Red Spot (GRS) tonight as it passes Jupiter’s meridian close to 8pm GMT.
All four of Jupiter’s large Galilean moons — Io, Europa, Ganymede and Callisto — are also well presented tonight. While you’re looking for the GRS, note that moons Io and Europa pass each other at 8:09pm GMT, separated by just three arcseconds. The changing relative positions of the moons will be fascinating to watch at high powers — if seeing permits, naturally.The configuration of Jupiter and its Galilean moons at the instant Io passes close to Europa. The view is north up and east to the left — as one would see with a high-power terrestrial telescope. Users of Newtonian/Dobsonian reflectors should invert the graphic to match the eyepiece view, while owners of refractors, Maksutov- and Schmidt-Cassegrain telescopes using a star diagonal need to mirror the graphic left-right to match their view. AN illustration by Ade Ashford / SkySafari Pro.If you consult our interactive Almanac, you can obtain predictions of when the Galilean moons will pass in front of Jupiter (termed a transit), or when their inky-black shadows drift across the face of their parent planet — events called shadow transits; the latter are easier to view. For a summary of Jovian phenomena to see during the remainder of March, see this article.
As the night moves on, the angular separation of Jupiter and the Moon actually decreases owing to the latter’s rapid west-east orbit motion. As Tuesday arrives at midnight, the pair will be just three degrees apart as seen from the UK. By the time Jupiter and the Moon fade into the growing dawn twilight low in the west around 5am GMT for the centre of the British Isles, they will be closer still. If you’re an early riser Tuesday, when’s the latest that you can still see Jupiter with the naked eye?
Inside the magazine
Find out everything you need to know about observing Jupiter at its best and the other planets in the night sky in the March 2016 edition of Astronomy Now.
Magnitude +2.9 star Mu (μ) Geminorum, better nown as Tejat in the constellation of Gemini, is occulted (hidden) by the rising 13-day-old waxing gibbous Moon early on the evening of Thursday, 9 January 2020 as seen from the entire British Isles. This is a spectacle for small telescopes and large binoculars, the first bright lunar occultation of a busy year for such events.
The creation of a specialised IAU Working Group, the Working Group on Star Names (WGSN), was approved by the IAU Executive Committee in May 2016 to formalise star names that have been used colloquially for centuries. WGSN has now established a new catalogue of IAU star names, with the first set of 227 approved names published on the IAU website.
A newly discovered planet orbiting a star known as HIP 11915 is the most accurate analogue yet found for the Sun and Jupiter. HIP 11915 is about the same age and composition as the Sun, suggesting that there may also be rocky Earth-like planets orbiting closer to the star.
