Three international spacecraft converge on Mars

Alan Pickup

Author: Alan Pickup
The maps show the sky at 22:00 GMT on the 1st, 21:00 on the 15th and 20:00 on the 28th. An arrow depicts the motion of Mars.

February is the briefest month in the calendar, but Orion and his retinue of superb winter stars ensure that we enjoy some of our best stargazing of the year. Although there is a dearth of bright planets this month, the exception is Mars which is drawing closer to the iconic Pleiades star cluster and is about to welcome an international trio of uncrewed spacecraft that were launched from the Earth last September.

Leading the way is the Hope orbiter, the first interplanetary mission by the United Arab Emirates. Its design and development were led by a space centre in Dubai, working in conjunction with universities in the USA. Hope is due to be captured into Mars-orbit on the 9th with the aim of plugging a gap in our knowledge concerning the daily and seasonal cycles affecting the Martian atmosphere, weather and dust storms.

China’s Tianwen-1 is due to enter Mars-orbit on the 10th and, eventually, send a lander and rover down to the surface. Its first task, though, is to image and survey its first-choice landing site in Mars’ Utopia Planitia, a large plain in the planet’s northern hemisphere. It may not be until May before the lander touches down and its rover trundles down a ramp to begin its exploration.

Finally comes NASA’s Perseverance rover which is heading directly for a landing on the 18th. Its target is in the 49-km-wide Jezero Crater which lies on the edge of Syrtis Major, a dark feature on Mars that is familiar to amateur astronomers and was the first surface marking ever to be recognised on another planet.

It is thought that Jezero once held a long-lived lake in which ancient Martian life may have developed. An array of scientific instrument will investigate this theory while, in addition, the rover carries an experimental solar-powered mini-helicopter called Ingenuity to scout its way ahead. Also attached is a plate with a staff-and-serpent symbol as an appreciation to healthcare workers during the Covid-19 pandemic.

Edinburgh’s days grow two hours longer in February as the sunrise/sunset times change from 08:07/16:46 on the 1st to 07:06/17:45 on the 28th. The Moon is at last quarter on the 4th, new on the 11th, at first quarter on the 19th and full on the 27th.

As darkness falls at present, the bright and non-twinkling Mars stands 51° high in the south as seen from Edinburgh. This month sees it continue to fade and recede, its magnitude falling from 0.4 to 0.9 while its distance grows from 178 million to 219 million km. It also tracks 16° east-north-eastwards against the stars, moving from Aries into Taurus where it lies 3° below the Pleiades star cluster at the month’s end. Mars sinks westwards during the evening and sets in the north-west by 02:00.

The Moon lies below-Mars on the 18th and is at first quarter on the next evening when it lies further to the left of the planet and 6° below-left of the Pleiades. Compare the brightness and colour of Mars with Taurus’ leading star Aldebaran which shines at about magnitude 0.9 not far to Mars’ east (left). Whereas Mars owes it reddish-orange hue to its rusty surface, Aldebaran is an orange giant star with a surface at 3.600C, some 1,900C cooler than our Sun.

Most of the other bright planets are lost in the Sun’s glare, at least as seen from our latitudes. Saturn and Jupiter reached conjunction on the Sun’s far side in the past few days while Venus rises with the Sun. Mercury concludes its spell of evening visibility as the month begins and reaches inferior conjunction on the Sun’s near side on the 8th.

There is no mistaking the handsome constellation of Orion the Hunter which climbs from the south-east to pass due south one hour before our map times. The distinctive pattern made by its main stars is entirely a chance alignment – the stars concerned are at different distances with the closest, Bellatrix (see chart), at about 250 light years. All the others are at least twice as distant and the three in Orion’s Belt are beyond 1,000 light years. All these are more massive and much more luminous than our Sun – place the Sun at a comparable distance and we’d probably need binoculars to spot it.

If we could examine Orion through infrared eyes, we would see the whole constellation blanketed by clouds of gas and dust which lie 1,000 to 1400 light years away. Dubbed the Orion Molecular Cloud Complex, it is peppered by glowing nebulae of which the most prominent is the famous star-factory of the Orion Nebula.

Above-left of Orion, and due south at our map times, is Gemini, the constellation of the heavenly twins of Greek mythology, Castor and Pollux. Its two leading stars have the same names, with Pollux, the brighter and lower of the pair, being the closest giant star to the Sun at 34 light years.

Castor, though, is a remarkable family of six stars at a distance of 51 light years. What the unaided eye sees as single, appears through a telescope as two white stars only 5 arcseconds apart that orbit each other every 445 years, while a third dim star circles them both every 14,000 years or so. In fact, spectroscopy tells us that the third star is made up of a pair of red dwarf stars circling each other every 20 hours, and that each of the brighter stars has its own exceedingly close red dwarf companion.

Tradition depicts the twins lying side by side with their feet towards Orion. The star Alhena, at the feet of Pollux, is slightly fainter than Castor while our chart plots the star cluster M35 hovering near Castor’s feet. Easily seen through binoculars and spreading over an area as large as the Moon, M35 lies about 3,870 light years away and its stars formed some 175 million years ago.

Diary for 2021 February

  • 3rd 00h Moon 7° N of Spica
  • 4th 18h Last quarter
  • 6th 09h Moon 5° N of Antares
  • 8th 14h Mercury in inferior conjunction on near side of Sun
  • 11th 19h New moon
  • 18th 23h Moon 4° S of Mars
  • 19th 14h Moon 6° S of Pleiades
  • 19th 19h First quarter
  • 20th 14h Moon 5° N of Aldebaran
  • 24th 02h Moon 4° S of Pollux
  • 25th 01h Moon 2.7° N of Praesepe
  • 26th 15h Moon 5° N of Regulus
  • 27th 08h Full moon

This is an extended version, with added diary, of Alan’s article published in The Scotsman on January 30 2021, with thanks to the newspaper for permission to republish here.