As the year 2024 comes to a close, it’s time to look back and recall the most significant astronomical events and discoveries of the year. Every day, thousands of different telescopes operate across the globe and in space, their data is processed on thousands of computers, and thousands of astronomers uncover the secrets of the Universe. But perhaps we remember this year most of all for the spectacular comet and the incredible aurorae that reached the middle latitudes.
From a huge number of different publications in 2024, we have selected 10 of the most interesting, in our opinion, studies in the field of astronomy, astrophysics and cosmology, and also highlighted 5 exciting astronomical events.
The most important scientific discoveries
New satellites of ice giants
For about 20 years, no new satellites have been registered for the most distant planets in the Solar System. But February this year was marked by “additions” to both Uranus and Neptune. The discovery was made by a research team led by Scott Sheppard, an American astronomer who is particularly well known for having discovered (either alone or in collaboration) satellites for all 4 gas giants in the Solar System.
The new moon of Uranus is identified as S/2023 U1, bringing the total number of officially recognized bodies orbiting the planet to 28. S/2023 U1 is about 8-12 km in size, with an orbit similar to that of the previously known Caliban and Stephano, suggesting that they may have a common origin.
The Neptune family has been expanded with the satellites S/2021 N1 and S/2002 N5, bringing their total number to 16. The size of the first of them is estimated at 14 km, and the second – at 23 km. As in the case of the new Uranus satellite, the orbit of S/2021 N1 is similar to the trajectories of Psamathe and Neso, and S/2002 N5 is related to Sao and Laomedeia.
Jupiter’s Great Red Spot “rejuvenated”
This is another discovery that will rewrite astronomy textbooks. The Great Red Spot is one of the most prominent and stable features of Jupiter, having been observed as early as 1665. It was believed that this huge vortex, which is larger than the Earth, had been around for almost 360 years. But it seems that after 1713, traces of the storm were lost for 118 years, at least no records of its existence were found even in the archives of observations by very experienced astronomers. What is known for certain is that the Great Red Spot has been observed regularly since 1831, meaning that it has been around for at least 193 years.
Modeling conducted in 2024 suggests that the vortex could well have collapsed and not remained stable for all 360 years. However, even if the Great Red Spot has only been observed for about 190 years, it is still impressive.
Intermediate-mass black holes
At least two classes of black holes are known for certain. One includes less massive ones (of stellar mass), which are usually found in binary systems where the second component is a star. The second class is supermassive black holes located in the centers of most galaxies. Between these two, there should be black holes of intermediate or medium mass. Despite theoretical calculations and suspicions, their existence has not been confirmed so far.
This year, two groups of scientists announced the reliable detection of intermediate-mass black holes. One of them is in the largest globular cluster in our Galaxy, Omega Centauri (southern hemisphere), with a mass of at least 8200 solar masses. The other is in the IRS 13 star cluster near the center of the Milky Way. The mass of this black hole is estimated at 30,000 solar masses. This latter may eventually merge with Sagittarius A*.
“Forbidden” black hole
Yes, we are talking about black holes again, but not so massive ones. The theory of black hole formation as a result of the evolution of massive stars suggests that a hole with a mass of 2-3 to 5 solar masses cannot exist, or at least such objects are extremely rare. However, in September 2024, a study was published in which the authors discovered a black hole with a mass of 3.6 solar masses.
Its discovery was made possible by the presence of a close neighbor, a red giant with a mass of 2.7 solar masses. The system, designated as G3425, orbits a common center of mass in wide circular orbits with a period of 880 days. It seems that the very existence of such a black hole challenges modern theories of stellar evolution.
Long-awaited planet around a nearby star
Barnard’s Star is a red dwarf, famous for its rapid self-motion, located less than 6 light-years away from us, making it one of the closest stars. It is no wonder that this invisible to the naked eye has been attracting the attention of scientists for many decades. In the 1960s, it was suspected that there was a planet around the star. However, subsequent checks refuted this claim.
In the autumn of 2024, using the Very Large Telescope (VLT), astronomers did detect tiny fluctuations in the position of Barnard’s Star relative to the calculated trajectory. These fluctuations are interpreted as the result of gravitational interaction with a planet whose mass is at least half that of Venus. The newly discovered planet Barnard b is 20 times closer to its star than Mercury is to the Sun, and a year on it lasts only 3.15 Earth days. Scientists estimate that the temperature on the planet’s daytime side reaches 125°C, which excludes the presence of liquid water and any life forms similar to those we know.
The mystery of the extremely massive brown dwarf solved
The brown dwarf Gliese 229B has been the subject of debate for almost three decades. In 1994-1995, scientists discovered that the red dwarf Gliese 229 has a satellite that is about 70 times the mass of Jupiter. The problem was that this satellite seemed too dim, like a brown dwarf.
It was only in October this year that astronomers using the Very Large Telescope (VLT) managed to discover that there are two brown dwarfs of similar mass, and not one, as previously thought. So, we now know that Gliese 229 consists of three objects: the red dwarf Gliese 229A, as well as a pair of brown dwarfs Gliese 229Ba and Bb with masses of 38 and 34 Jupiter masses, respectively.
Brown dwarf candidates in another galaxy
As sub-stellar objects, brown dwarfs emit very little light – they are usually detected in the infrared. And here, of course, the flagship of modern infrared astronomy, the James Webb Space Telescope, comes into play.
Detailed images of the star cluster NGC 602 in the vicinity of the Small Magellanic Cloud, a satellite galaxy of the Milky Way, have allowed scientists to identify as many as 64 brown dwarf candidates with masses ranging from 50 to 84 Jupiter. This discovery is still pending confirmation, but it already demonstrates the fantastic capabilities of the Webb in the study of extremely faint space objects.
First image of a star beyond the Milky Way
The next incredible achievement that shook the entire astronomical world was also associated with a Milky Way satellite, but this time with the Large Magellanic Cloud. For the first time, scientists were able to see the disc and the surroundings of the huge star WHO G64, which is 2000 times larger than our Sun.
Due to their considerable distance, direct observations of stellar discs, even in our own Galaxy, are a real challenge for modern astronomical instruments, and can only be achieved for the largest stars (e.g. Betelgeuse) and with the most powerful telescopes and advanced data processing techniques. The red supergiant WOH G64 was observed because four 8.2-meter VLT telescopes can work together as one huge interferometer. It turned out that the giant inhabitant of the Large Magellanic Cloud was surrounded by a cocoon of gas and dust and was most likely preparing to explode in a supernova soon.
James Webb takes a look at the outskirts of the Universe
The farther away a galaxy is from us, the faster it moves away from us, the radiation waves from it are stretched and shifted first to the red and then to the infrared. Therefore, the search for the most distant galaxies is also one of the priority tasks of the James Webb Infrared Space Telescope. And in this sense, it has already far exceeded the wildest expectations of astronomers.
In 2024, the galaxy JADES-GS-z14-0 was discovered and reliably confirmed, which we now see as it was 290 million years after the Big Bang, corresponding to a redshift of z=14.3. Moreover, it not only looks quite mature and formed but also shines quite brightly due to ongoing star formation flares. Scientists are now puzzling over how such a galaxy could have formed so early, as its existence contradicts existing models of the early Universe.
And it seems that JADES-GS-z14-0 may not even be a record yet. Shortly afterward, another group of scientists announced the discovery of 5 galaxies with z’s from 15.9 to 18.6, but they are still waiting for confirmation.
Unique double star system in a dangerous neighborhood
Closing the top of the hit parade of discoveries in 2024 is a very strange object, the existence of which was considered theoretically impossible. For the first time, a double star system was discovered near the supermassive black hole Sgr A* in the center of our Galaxy.
A double star is a pair of stars that are gravitationally bound and orbit a common center of mass. However, the extreme conditions around supermassive black holes should quickly destroy such pairs, even if they manage to form. Nevertheless, astronomers estimate the age of the double star D9 at 2.7 million years, and the masses of the components are at least 2.8 and 0.7 Sun masses. Scientists still assume that the system will not exist for long – the stars will merge and probably form one of the mysterious “G objects”, which have been discovered in large numbers around Sgr A*.
The most interesting astronomical events of the year
Asteroids that hit the Earth
In 2024, as many as 4 small asteroids (a record number!) were discovered just before impact with the Earth. On the night of 21 January, asteroid 2024 BX1 was observed burning up over Germany, and some fragments reached the surface and were even found by a team of enthusiasts. On 4 September 2024, RW1 crashed near the Philippines, but its remains are now at the bottom of the Pacific Ocean and are unlikely to ever fall into the hands of scientists. On 22 October, the asteroid 2024 UQ fell near the coast of California, but, as in the previous case, if part of it reached the surface, it was under a thick layer of water. The last collision took place on 3 December – if the remains of asteroid 2024 XA1 did reach the surface, they were lost in the forests of Eastern Siberia and, due to harsh weather conditions, will most likely not be found, at least in the near future.
All of these bodies are quite small – no more than 1 m and can even be classified as meteoroids rather than asteroids. That’s why it was so difficult to spot them in advance. Each of them was discovered a few hours before the collision, but their trajectories were carefully calculated and the moments and points of re-entry were very accurately predicted, so each of these events had many witnesses.
The brightest comet in the last 27 years
The year 2024 will remain in our memory as the year of the bright comet C/2023 A3 (Tsuchinshan-ATLAS), which, with its amazing appearance, surpassed all its “sisters” over the past 27 years – since the time of Comet Gale-Bopp in 1997. At first, we carefully followed its approach to the Sun, visible in the Southern Hemisphere. And after passing perihelion, we were able to enjoy this rare astronomical phenomenon ourselves.
The best time for observing was in mid-October, but for a couple of weeks, C/2023 A3 could still be seen in the evening sky with the naked eye. And even now, in December, enthusiasts continue to photograph it, despite the fact that the comet has already moved farther away from us and appears as a barely visible cloud in the images.
The Sun has reached its maximum activity in the current cycle
Although last year the maximum solar activity was predicted for 2025, this forecast was later changed to a more accurate one for autumn 2024. Indeed, on 15 October, NASA and NOAA reported that the Sun had already reached its maximum activity in the current 25th cycle. Scientists assume that high activity will continue throughout 2025.
Each such cycle lasts approximately 11 years. The growth of activity is manifested by an increase in the number of sunspots and their total area, as well as frequent flares and coronal mass ejections. In particular, in the current cycle, a total of more than 50 powerful class X flares have already been recorded. In particular, X9.05 (3 October) and X8.79 (14 May), which rank 15th and 18th respectively in the top of the most powerful flares in the history of regular observations since 1996.
Spectacular auroras
Although the aurora is most often associated with the Arctic Circle or Norway or Finland, this year Ukraine and the rest of Europe could enjoy this extraordinary atmospheric phenomenon in one way or another. We owe it primarily to solar activity, as the prerequisite for an aurora is a powerful coronal mass ejection directed toward the Earth.
Faint auroras were observed several times this year, including on the night of the maximum of the Perseids meteor shower (12-13 August). But they were most beautiful on the night of 10-11 May, and also almost six months later on 10-11 October.
The season of transits of Titan’s shadow across Saturn’s disc, which occurs once every 15 years, has begun
Once every 15 years, near the equinox on the planet Saturn, the necessary specific conditions are in place: the largest moon, Titan, casts a shadow on the planet, and we can see it from Earth. Fortunately, this rare phenomenon is not just one, but several such events in a series that can be observed over several months. And it was in November 2024 that one of them began.
The period of Titan’s orbit around Saturn is close to 16 days, so it is with this frequency that shadows can be observed on the surface of The Lord of the Rings. The series will continue in January 2025, so hurry up and see it or be patient to wait another 15 years.
