The Sky Above You, April 2025
by Duncan Lunan
The Moon is Full on April 12th, and New on April 27th. It passes through the Pleiades on April 1st and 2nd, near Jupiter on the 2nd, near Mars on the 5th, and is near Venus on the 24th and 25th, back near the Pleiades on the 29th and Jupiter on the 30th. (Details of the April 1st star occultations are in the April issue of Astronomy Now, on page 52.)
The planet Mercury is not visible this month, although at greatest elongation from the Sun on the 21st.
Venus is back in the morning sky at the start of the month, rising at 5 a.m., at greatest brightness on April 22nd, passed by the Moon on the 24th and 25th.
Mars is still in Gemini, passed by the Moon on the 5th, in line with Castor and Pollux on the 10th, setting at 3.30 a.m., and entering Cancer by the end of April.
Last month I reported that in 2014, two years after landing in Gale crater, the Curiosity rover found evidence of a phase 3.7 billion years ago when there were shallow lakes on the crater floor, later than the deep lake which filled the crater about 4 billion years ago. On January 15th 2025 it was announced that further study of the deposits had identified ripples in rock layers laid down by water 2 metres deep or less, but formed by wind-driven waves, indicating that liquid open water had survived on Mars for significantly longer than had been thought, increasing the possibility of life once having existed there. And ongoing remote analysis of samples picked up at a feature named 'Cumberland', on the crater floor in 2013, shows large organic molecules, larger than any found on Mars before, which on Earth would be taken to be remains of fatty acids manufactured by living organisms. (Paul Scott Anderson, 'Surprisingly big organic molecules on Mars: A hint of life?', EarthSky, online, March 27th 2025). Still not the 'smoking gun' for life on Mars, at least in the past, but the hunt continues.
On 12th March ESA's HERA probe, bound for the Didymos-Dimorphos asteroid pair, made a Mars slingshot within 3000 miles and passed the outer moon Deimos at 320 miles. Because the rotation of Deimos is trapped with respect to Mars and it was over the sunlit side, the images captured the farside of Deimos in 1000 images, mainly infrared and far infrared). Previously the Deimos farside had been seen only by the United Arab Emirates' Hope orbiter, which revealed a previously unsuspected cleft in the moon, and it's hoped that detailed study will show more. (Kelly Kizer Whitt, 'New Mars and Deimos pics from revealing Hera flyby', EarthSky, online, 14th March 2025.)
NASA's Lucy probe will make its first encounter with a Main Belt asteroid on April 20th, passing the carbonaceous asteroid Donaldjohansen. Carbonaceous asteroids are plentiful in the outer Belt, but meteorites from them are rare because mostly they disintegrate in Earth's atmosphere. Those that do survive are rich in naturally formed organic compounds from the early Solar System, and as these have also been found in the samples returned by OSIRIS-REx from the asteroid Bennu, observations of Donaldjohansen should be of great interest.
Pallas, the third largest of the asteroids and the second one to be discovered, has a large impact crater, like the one at the south pole of Vesta, the second largest asteroid. Its spectrum contains blue spikes in what's otherwise the typical spectrum of carbonaceous asteroids and meteorites, which differ from stony and nickel-iron meteorites by containing water and naturally formed organic compounds. Around 300 'Pallasites' are found in the B-type family, chipped off by impacts, which make up about 4% of known asteroids. Almost all orbit in the Main Belt, but one notable exception is Phaethon, which passes near the Sun and undergoes eruptions which generate the Geminid meteor shower each year in December. (Andy Tomaswick, 'Pallas Has a Very Blue Family', Universe Today, online March 16th 2025.) Perhaps we'll find examples among the samples brought back from asteroid Bennu, which come from all over the Solar System and are of great age, some possible predating the planets. All this is of great interest in the ongoing debate, where did Earth's water come from – inside the planet, from Main Belt asteroids, or from Kuiper Belt objects (beginning to look less likely). And just how complex were the organic compounds carried with them?
Jupiter is still bright, between the horns of Taurus, setting around 1.00 a.m.. The Moon passes it on the 2nd and 30th.
Saturn in Aquarius is still too close to the Sun to observe.
Uranus is in Taurus, setting at 10.30 p.m., near the Moon on the 1st and gone by the end of April.
Neptune in Pisces is not visible this month. But the James Webb Space Telescope has been looking at Neptune in the infrared, and found a clear trace of auroral activity, which can be superimposed on ultraviolet observations made by Voyager 2 in 1989. Unlike the other planets with atmospheres and magnetic fields, where aurorae are found in the polar regions, Neptune's magnetic field is displaced from the polar axis by 47 degrees and the aurorae are in low latitudes. (EarthSky Voices, 'See Auroras on Neptune for the First Time!', EarthSky, online, March 27th, 2025.)
Lyrid meteors from Comet Thatcher (no relation) can be seen from 14th to 30th April, but peak on the night of the 22nd/23rd, in a dark sky, with the Moon not rising till 4 a.m., near dawn. This is not a dense shower but in good conditions an observer could expect to see 10 or more bright meteors per hour. Best time to see them is after 1 a.m., as the Earth turns towards the constellation from which they radiate, and the apparent radiant climbs higher in the sky.
An outburst of nova T Coronae Borealis is expected any time, after 80 years. Although it isn't 'due' till 2026, the star has been flickering as it did before the last event. The circlet of Corona Borealis is below and to the left of the red giant star Arcturus, and its brightest star is Alphecca, 2nd magnitude like the stars of the Plough. If you see two stars there, one just off the circlet, then the nova is taking place.
And speaking of outbursts: an international team of astronomers led by CHRIST University, Bangalore, has found that 2MASX J23453268-0449256, a spiral galaxy three times the diameter of the Milky Way, with ten times as much dark matter, almost 1 billion light-years away, hosts a supermassive black hole powering colossal radio jets, 6 million light-years from tip to tip. (EarthSky Voices, 'Cosmic Anomaly Hints at Frightening Future for the Milky Way', EarthSky, online, March 21st 2025). Presumably 2MASX is older than the Milky Way, though the article doesn't actually say so. But it has retained a form very like the Milky Way's, including well-defined spiral arms, a luminous nuclear bar, and an undisturbed stellar ring. As such jets can tear away the structure of a galaxy, that suggests that the jets, from the axis of the supermassive black hole, are pointing out of the spiral. But as we can see many examples where galaxies have been torn apart in such cases, there's no guarantee that an offset will be the case with Sagittarius A*, the black hole at the centre of the Milky Way - hence the scary headline. Jets like that would destroy the spiral arms if pointing into them, let alone destroy the Earth's magnetic field and rip the atmosphere off the planet. Then again, so could a much less violent gamma-ray burster anywhere within the Milky Way, so let's not worry too much about it. One candidate for that was the Wolf-Rayet 104 double star, 8,400 light-years away in Sagittarius, a 'pinwheel' which appeared to be pointing right at us, but now turns out to be inclined 30-40 degrees away (Paul Scott Anderson, 'Famous, rare ‘pinwheel death star’ isn’t a threat after all', EarthSky, online, March 25th 2025', citing 'Famed WR 104 "Pinwheel" Star Reveals Another Surprise (and Some Relief)', W.M. Keck Observatory, online, March 18th 2025).
Postscript: in January 2025 I reported on observatories under threat in Scotland and Britain, following in February with the even greater threat to the European Southern Observatory in Chile. ('The Sky Above You', ON, 1st January and 1st February, 2025), including the concern of the Observatory Science Centre that the former Royal Observatory site at Herstmonceux in Sussex would be closed in 2026 by its owners, Canadian Queens University. The good news is that Queen's University and Bader College at Herstmonceux have issued a commitment to preserve and enhance the site ('Bader College, Queen's committed to upholding observatory site's legacy', online, February 11th, 2025.) Space.com has now run a history of the Observatory and the threat to end its current role as a public observatory, tourist venue and exhibition site (Ryan French, 'Preserving astronomy history: The fight is on to save iconic Royal Greenwich Observatory site', Space.com online, 23rd March 2025), which notes the Bader College and Queen's announcement but is less optimistic. The petition by the Herstmonceux Observatory Campaign Group to save it has drawn 12,000 signatures, and can be found at 'Save the Observatory Science Centre Herstmonceux', on change.org.
Duncan’s recent books are available through Amazon; details are on Duncan’s website, www.duncanlunan.com.
The Sky Above You
By Duncan Lunan
About this Column
I began writing this column in early 1983 at the suggestion of the late Chris Boyce. At that time the Post Office would allow 1000 free mailings to start a new business, just under the number of small press newspapers in the UK at the time. I printed a flyer with the help of John Braithwaite (of Braithwaite Telescopes) offering a three-part column for £5, with the sky this month, a series of articles for beginners, and a monthly news feature. The column ran from May 1983 to May 1993 in various newspapers and magazines, but never in more than five outlets at a time, although every one of those 1000-plus papers would have included an astrology column. Since then it’s appeared sporadically in a range of publications including The Southsider in Glasgow and the Dalyan Courier in Turkey, but most often, normally three times per year, in Jeff Hawke’s Cosmos from the first issue in March 2003 until the last in January 2018, with a last piece in “Jeff Hawke, The Epilogue” (Jeff Hawke Club, 2020). It continues to appear monthly in Troon's Going Out and Orkney News, with an expanded version broadcast monthly on Arransound Radio since August 2023
The monthly maps for the column were drawn for me by Jim Barker, based on similar, uncredited ones in Dr. Leon Hausman’s “Astronomy Handbook” (Fawcett Publications, 1956). Jim had to redraw or elongate several of them because they were drawn for mid-US latitudes, about 40 degrees North, making them usable over most of the northern hemisphere. The biggest change needed was in November when only Dubhe, Merak and Megrez of the Big Dipper, as the US version called it, were visible at that latitude. In the UK, all the stars of the Plough are circumpolar, always above the horizon. We decided to keep an insert in the January map showing the position of M42, the Great Nebula in the Sword of Orion, and for that reason, to stick with the set time of 9 p.m., (10 p.m. BST in summer), although in Scotland the sky isn’t dark then during June and July.
To use the maps in theory you should hold them overhead, aligning the North edge to true north, marked by Polaris and indicated by Dubhe and Merak, the Pointers. It’s more practical to hold the map in front of you when looking south and then rotate it as you face east, south and west. Some readers are confused because east is on the left, opposite to terrestrial maps, but that’s because they’re the other way up. When you’re facing south and looking at the sky, east is on your left.
The star patterns are the same for each month of each year, and only the positions of the planets change. (“Astronomy Handbook” accidentally shows Saturn in Virgo during May, showing that the maps weren’t originally drawn for the Hausman book.) Consequently regular readers for a year will by then have built up a complete set of twelve.
©DuncanLunan2013, updated monthly since then.