Astronomers spot the brightest object ever seen in the Universe

Alan Pickup

Author: Alan Pickup

The maps show the sky at 23.00 GMT on the 1st, 22.00 GMT on the 16th and 21.00 GMT (22.00 BST) on the 31st. British Summer Time begins at 01.00 GMT on the 31st when clocks go forward one hour to 02.00 BST.

Astronomers have used Europe’s Very Large Telescope in Chile to identify the brightest object ever observed in the Universe, one blazing with the power of 500 trillion, or 500,000,000,000,000, suns. The light comes from a disk of matter, mainly hydrogen, swirling into a black hole that has a mass of 17 billion suns and is swallowing the equivalent of an entire star like our Sun every day.

Credit: ESO/Digitized Sky Survey 2/Dark Energy Survey

The object has the catchy name SMSS J052915.80−435152.0 and shines at the 16th magnitude from some 12 billion light years. It was first photographed in 1980, but it is only now that its true nature as a quasar has been recognised, joining perhaps another million quasars that have been discovered since 1980, most of them much fainter. Indeed, its very brightness may be why it has been hiding in plain sight. All quasars are thought to sit in the centre of galaxies, but this is the largest and fastest-growing one ever seen.

The new quasar lies in the constellation Pictor about 36° south of the star Rigel in Orion and too far south to be seen from Scotland. Orion, itself, straddles the meridian in the south at nightfall as the month begins but makes a hasty retreat westwards during the month to stand some 10° lower in the south-west by nightfall on the 31st.

Our star maps show Orion closer still to its setting in the west another two hours later. Above, and slightly to its left is Gemini with Castor and Pollux. Regulus, in the handle of the backwards question-mark forming the Sickle of Leo, stands some 45° high in the south with the inverted Y of Cancer between Pollux and Regulus. Near the join of the Y is the Praesepe star cluster, visible to the naked eye in a dark sky and easy through binoculars.

Just under Cancer is the asterism of six stars that make up the head of Hydra the Water Snake, the largest of the sky’s 88 constellations.

While climbing another 12° northwards during March, the Sun crosses the sky’s equator at 03:06 on the morning of the 20th, bringing the vernal or spring equinox. This also marks the start of astronomical spring, though meteorologists hold that spring begins tomorrow, on March 1st. Edinburgh’s sunrise and sunset times change from 07:03/17:48 GMT on the 1st to 06:45/19:50 BST (05:45/18:50 GMT) on the 31st, the day when we set our clocks forward by one hour at the start of British Summer Time.

Jupiter is conspicuous well up in the south-west at nightfall on the 1st but is low down near our west-north-western horizon by the map times and sets soon after. Starting the month 20° below and right of the Pleiades, the giant planet tracks 6° closer to the cluster during March as it recedes and dims slightly from magnitude -2.2 to -2.0. Look for the earthlit and 17% sunlit Moon 4° to the right of Jupiter on the 13th when the Jovian disk spans 35 arcseconds if viewed telescopically from our distance of 835 million km.

The Moon is gibbous and low down in the south in Libra before dawn on the 1st and less than 2° to the right of the noticeably red supergiant star Antares in Scorpius on the morning of the 3rd. Last quarter phase comes later that day and is followed by new on the 10th and the Moon’s speedy emergence into our evening sky.

Forty minutes after sunset on the 11th, we might glimpse the thin sliver of the young lunar crescent, only 3% illuminated and 9° above the western horizon. We need to be sharp if we want to use it as a guide to Mercury which lies 8° below and right of the Moon and only 3° high at that time. Although the little planet, a mere 38% as wide as the Earth, is bright at magnitude -1.3, we will need binoculars to pick it out of the bright twilight so early in its apparition.

Its visibility soon improves, though, to give us our best chances to spot Mercury in our evening sky this year. We need the right weather, a vantage point with an unobstructed view low into the west and to remember that Jupiter shines higher and brighter in the same part of the sky, so do not confuse the two.

Mercury’s altitude forty minutes after sunset climbs to 10° by the 24th when it reaches its greatest angular distance of 19° east of the Sun in the sky. By then it has faded to magnitude -0.1 but should be easy to spot, even with the unaided eye, since it lingers longer in the fading twilight as it sinks to set a full two hours after the Sun. The final week of March sees Mercury fall only a couple of degrees in altitude but fade rapidly to a difficult magnitude 1.4 by the 31st as its apparition concludes.

For once, we can forget the other naked-eye planets, Venus, Mars and Saturn, which are too deep in our morning twilight to be seen this month.

In the wake of its encounters with Mercury and Jupiter, the Moon lies 5° below-right of the Pleiades on the 14th and reaches first quarter near the Taurus-Gemini border on the 17th. It stands above Regulus in Leo on the evening of the 21st and is full in Virgo on the 25th. As dawn approaches on that day, the Moon starts to enter the northern fringe of the Earth’s shadow, the penumbra, at 04:53 when it stands 10° high in our western sky. Sadly, it is unlikely that any darkening of the lunar surface will be noticeable before the Moon sets shortly after sunrise. The penumbral lunar eclipse ends at 09:32.

The Moon stands left of Spica on the morning of the 27th and once again meets Antares on the 30th, being right of the star on that morning and to its left on the 31st.

Diary for 2024 March

  • 3rd 09h Moon 0.3° N of Antares
  • 3rd 15h Last quarter
  • 10th 09h New Moon
  • 11th 02h Moon 1.0° S of Mercury
  • 14th 01h Moon 4° N of Jupiter
  • 14th 12h Moon 3° N of Uranus
  • 15th 04h Moon 0.4° S of Pleiades star cluster
  • 17th 04h First quarter
  • 17th 11h Neptune in conjunction with Sun
  • 19th 07h Moon 1.5° S of Pollux
  • 20th 03:06 Vernal equinox
  • 20th 09h Moon 4° N of Praesepe star cluster
  • 22nd 05h Moon 4° N of Regulus
  • 24th 23h Mercury furthest E of Sun (19°)
  • 25th 07h Full Moon and penumbral lunar eclipse
  • 26th 20h Moon 1.4° N of Spica
  • 30th 15h Moon 0.3° N of Antares
  • 31st 01h GMT = 02h BST Start of British Summer Time

This is an extended version, with added diary, of Alan’s article published in The Scotsman on 29 February 2024, with thanks to the newspaper for permission to republish here.