Ingenuity helicopter readied for pioneering flight on Mars

Alan Pickup

Author: Alan Pickup
The maps show the sky at midnight BST on the 1st, 23:00 on the 16th and 22:00 on 30th. An arrow shows the motion of Mars.

With most of the planets poorly placed for viewing, and with Orion sinking into the western evening twilight, our April night sky might appear disappointing to many. Mars is still there, but it no longer demands attention at nightfall since it is four times further away and more than thirty times fainter than it was as recently as October.

Our monthly chart represents something of a lull between the spectacular evening constellations of winter and the rich Milky Way patterns of the summer and autumn, typified by the Summer Triangle formed by the bright stars Altair in Aquila, Vega in Lyra and Deneb in Cygnus. The latter two lie in the north-east at our map times and if we watch Vega as it climbs high into the east in the early hours of the 22nd, we should be alert for medium-swift meteors of the Lyrids shower as they diverge from a radiant point close by.

Step outside at nightfall at present, though, and Orion still dominates our lower south-western sky, the three stars of his Belt pointing to the left to Sirius and to the right to Aldebaran in Taurus. Mars, now noticeably dimmer than Aldebaran, lies 10° above it on the 1st before tracking east-north-eastwards between the Bull’s horns and onwards to the feet of Gemini by the month’s end.

Meanwhile, the planet dims from magnitude 1.3 to 1.6 as its distance grows from 263 million to 302 million km and its tiny disk shrinks below 5 arcseconds in diameter.

On the evening of the 26th, Mars passes only 0.6° (about a Moon’s breadth) above-right of M35, a cluster of hundreds of stars at a distance of almost 4,000 light years. M35 is usually easy to see through binoculars, but may be more of a challenge on this occasion since the meeting with Mars occurs in the light of the full Moon.

NASA’s engineers have continued checks of their Perseverance rover following its spectacular landing in Mars’ Jezero crater on 18 February. It has made its first drives, while its two onboard microphones (the first to reach the planet) relayed the sounds of the Martian wind and the rover’s metal wheels crunching across the surface. The rover also carries Ingenuity, a 1.8 kg helicopter which could make the first ever powered, controlled flight on another planet in the coming days, but probably no earlier than the 8th, under the watchful eyes of Perseverance’s cameras.

Edinburgh’s sunrise/set times change from 06:43/19:51 BST on the 1st to 05:31/20:50 on the 30th. The Moon is at last quarter on the 4th, new on the 12th, at first quarter on the 20th and full on the 27th.

The thin sliver of the young Moon may be glimpsed just above our western horizon in the evening twilight on the 13th while a day later it is impressively earthlit below the Pleiades. It lies between the Pleiades and Aldebaran on the 15th and 3° above-left of Mars on the 17th, having occulted the planet earlier that day as seen from south-eastern Asia.

The Plough looms overhead at our map times, though it is squashed and stretched on our charts. At the same time, the familiar “W” of Cassiopeia is turning counterclockwise below Polaris in the north. A rare binocular-brightness nova or “new star” – actually a temporary and non-destructive outburst of a faint star – was discovered from Japan on 18 March (see chart), peaked at about magnitude 7.6 a day or two later and is fading only very slowly as I write this.

Leo, chasing Cancer into the south-west at the map times, is followed by Virgo and its bright star Spica, the 15th brightest in Earth’s night sky and six ahead of Leo’s leader Regulus. Higher in the south-east, and in third place in the stellar league, is Arcturus in Bootes. We can connect Arcturus to Spica and the fainter Denebola at Leo’s tail to form an asterism that many call the Spring Triangle. Include the still fainter star Cor Caroli in Canes Venatici, the Hunting Dogs, further to the north to construct yet another asterism, the Diamond of Virgo which is known more grandly as the Great Diamond.

The western half of the diamond contains a region sometimes called the Realm of the Galaxies. Here, about 54 million light years away and 10° east of Denebola, is the heart of the Virgo cluster of more than 1,300 galaxies, several of which are visible through small telescopes. One of these, M87, is home to the supermassive black hole whose image was released two years ago this month. The Virgo cluster dominates the much larger Virgo supercluster of galaxies to which the Andromeda Galaxy and our own Milky Way belong. Another supercluster of galaxies has its centre some 300 million light years away in the neighbouring dim constellation of Coma Berenices.

The giant planets Saturn and Jupiter are becoming visible in our predawn sky, but are much better seen from southern latitudes. Forty minutes before sunrise on the 1st, Saturn is magnitude 0.7 and only 4° high in Edinburgh’s south-east while Jupiter is much brighter at magnitude -2.1 but 2° lower still and 12° to Saturn’s left. By the equivalent time on the 30th, they stand 4° higher and, given an unobstructed horizon, should be easy to spot in the brightening twilight.

Venus swept around the Sun’s far side on 26 March and is followed by Mercury on the 19th. As they begin to emerge in our evening twilight, Mercury passes 1.3° above-right of Venus on 25th. Thirty minutes after sunset on the 30th, Venus is brilliant at magnitude -3.9 but only 2° high in the west-north-west, while Mercury is 2° higher and magnitude -1.2.

Diary for 2021 April

  • 1st 22h Moon 5° N of Antares
  • 4th 11h Last quarter
  • 12th 04h New moon
  • 15th 06h Moon 5° S of Pleiades
  • 16th 06h Moon 5° N of Aldebaran
  • 17th 13h Moon 0.1° S of Mars
  • 19th 03h Mercury in superior conjunction on far side of Sun
  • 19th 20h Moon 3° S of Pollux
  • 20th 08h First quarter
  • 20th 20h Moon 3° N of Praesepe
  • 22nd 19h Moon 5° N of Regulus
  • 26th 04h Moon 6° N of Spica
  • 26th 10h Mercury 1.3° N of Venus
  • 27th 05h Full moon
  • 29th 08h Moon 5° N of Antares
  • 30th 21h Uranus in conjunction with Sun

This is an extended version, with added diary, of Alan’s article published in The Scotsman on March 31 2021, with thanks to the newspaper for permission to republish here.