On July 19, 1952, Palomar Observatory was undertaking a photographic survey of the night sky. Part of the project was to take multiple images of the same region of sky, to help identify things such as asteroids. At around 8:52 that evening a photographic plate captured the light of three stars clustered together. At a magnitude of 15, they were reasonably bright in the image. At 9:45 pm the same region of sky was captured again, but this time the three stars were nowhere to be seen. In less than an hour they had completely vanished.

Stars don't just vanish. They can explode, or experience a brief period of brightness, but they don't vanish. And yet, the photographic proof was there. The three stars are clearly in the first image, and clearly not in the second. The assumption then is that they must have suddenly dimmed, but even that is hard to accept. Later observations found no evidence of the stars to dimmer than magnitude 24. This means they likely dimmed by a factor of 10,000 or more. What could possibly cause the stars to dim by such an astounding amount so quickly?

One idea is that they are not three stars, but one. Perhaps a star happened to brighten for a short time, such as a fast radio burst from a magnetar. While this happened, perhaps a stellar-mass black hole passed between it and us, causing the flare to gravitationally lens as three images for a brief time. The problem with this idea is that such an event would be exceedingly rare, but other photographic images taken during the 1950s show similar rapid disappearances of multiple stars. In some cases, the stars are separated by minutes of arc, which would be difficult to produce by gravitational lensing.

New artificial intelligence tool removes humans from entire search, discovery process.
A fully automated process, including a brand-new artificial intelligence (AI) tool, has successfully detected, identified and classified its first supernova.

Developed by an international collaboration led by Northwestern University, the new system automates the entire search for new supernovae across the night sky — effectively removing humans from the process. Not only does this rapidly accelerate the process of analyzing and classifying new supernova candidates, it also bypasses human error.

The team alerted the astronomical community to the launch and success of the new tool, called the Bright Transient Survey Bot (BTSbot), this week. In the past six years, humans have spent an estimated total of 2,200 hours visually inspecting and classifying supernova candidates. With the new tool now officially online, researchers can redirect this precious time toward other responsibilities in order to accelerate the pace of discovery.

"For the first time ever, a series of robots and AI algorithms has observed, then identified, then communicated with another telescope to finally confirm the discovery of a supernova," said Northwestern's Adam Miller, who led the work. "This represents an important step forward as further refinement of models will allow the robots to isolate specific subtypes of stellar explosions. Ultimately, removing humans from the loop provides more time for the research team to analyze their observations and develop new hypotheses to explain the origin of the cosmic explosions that we observe."

"We achieved the world's first fully automatic detection, identification and classification of a supernova," added Northwestern's Nabeel Rehemtulla, who co-led the technology development with Miller. "This significantly streamlines large studies of supernovae, helping us better understand the life cycles of stars and the origin of elements supernovae create, like carbon, iron and gold."

Miller is an assistant professor of physics and astronomy at Northwestern's Weinberg College of Arts and Sciences and a member of the Center for Interdisciplinary Exploration and Research in Astrophysics (CIERA). Rehemtulla is an astronomy graduate student in Miller's research group.

An international team of scientists have discovered a huge spike in radiocarbon levels 14,300 years ago by analysing ancient tree-rings found in the French Alps.

The radiocarbon spike was caused by a massive solar storm, the biggest ever identified. A similar solar storm today would be catastrophic for modern technological society - potentially wiping out telecommunications and satellite systems, causing massive electricity grid blackouts, and costing us billions of pounds.

The academics are warning of the importance of understanding such storms to protect our global communications and energy infrastructure for the future.

Collaboration

The collaborative research, which was carried out by an international team of scientists, is published today (Oct 9) in The Royal Society's Philosophical Transactions A: Mathematical, Physical and Engineering Sciences and reveals new insights into the Sun's extreme behaviour and the risks it poses to Earth.

A team of researchers from the Collège de France, CEREGE, IMBE, Aix-Marseille University and the University of Leeds measured radiocarbon levels in ancient trees preserved within the eroded banks of the Drouzet River, near Gap, in the Southern French Alps.

The tree trunks, which are subfossils - remains whose fossilisation process is not complete - were sliced into tiny single tree-rings. Analysis of these individual rings identified an unprecedented spike in radiocarbon levels occurring precisely 14,300 years ago. By comparing this radiocarbon spike with measurements of beryllium, a chemical element found in Greenland ice cores, the team proposes that the spike was caused by a massive solar storm that would have ejected huge volumes of energetic particles into Earth's atmosphere.

Edouard Bard, Professor of Climate and Ocean Evolution at the Collège de France and CEREGE, and lead author of the study, said: "Radiocarbon is constantly being produced in the upper atmosphere through a chain of reactions initiated by cosmic rays. Recently, scientists have found that extreme solar events including solar flares and coronal mass ejections can also create short-term bursts of energetic particles which are preserved as huge spikes in radiocarbon production occurring over the course of just a single year."

The sun is about to lose something important: Its magnetic poles.

Recent measurements by NASA's Solar Dynamic Observatory reveal a rapid weakening of magnetic fields in the polar regions of the sun. North and south magnetic poles are on the verge of disappearing. This will lead to a complete reversal of the sun's global magnetic field perhaps before the end of the year.
If this were happening on Earth, there were be widespread alarm. Past reversals of our planet's magnetic field have been linked to calamities ranging from sudden climate change to the extinction of Neanderthals. On the sun, it's not so bad.

"In fact, it's routine," says Todd Hoeksema, a solar physicist at Stanford University. "This happens every 11 years (more or less) when we're on the verge of Solar Maximum."

Vanishing poles and magnetic reversals have been observed around the peak of every single solar cycle since astronomers learned to measure magnetic fields on the sun. Hoeksema is the director of Stanford's Wilcox Solar Observatory (WSO), that is observing its fifth reversal since 1980.

Icy bodies at Solar System's edge found during target hunt for NASA spacecraft.
There just doesn't seem to be enough of the Solar System. Beyond Neptune's orbit lie thousands of small icy objects in the Kuiper belt, with Pluto its most famous resident. But after 50 astronomical units (AU) — 50 times the distance between Earth and the Sun — the belt ends suddenly and the number of objects drops to zero. Meanwhile, in other solar systems, similar belts stretch outward across hundreds of AU. It's disquieting, says Wesley Fraser, an astronomer at the National Research Council Canada. "One odd thing about the known Solar System is just how bloody small we are."

A new discovery is challenging that picture. While using ground-based telescopes to hunt for fresh targets for NASA's New Horizons spacecraft, now past Pluto on a course out of the Solar System, Fraser and his colleagues have made a tantalizing, though preliminary, discovery: about a dozen objects that lie beyond 60 AU — nearly as far from Pluto as Pluto is from the Sun. The finding, if real, could suggest that the Kuiper belt either extends much farther than once thought or — given the seeming 10-AU gap between these bodies and the known Kuiper belt — that a "second" belt exists.

The discovery, being prepared for publication and not yet peer reviewed, is supported by measurements from New Horizons itself, which at 57 AU continues to streak beyond the edge of the known Kuiper belt. Many of its instruments are in hibernation, but a dust counter has run continuously during the mission. Dust is a telltale sign of colliding planetary bodies, and so the New Horizons team expected the amount of dust to fall off steeply after the probe left the Kuiper belt, where it had rendezvoused with an object called Arrokoth. Instead, "The number of impacts is not declining," says Alan Stern, the mission's principal investigator and a planetary scientist at the Southwest Research Institute. "And the simplest explanation for that is that there is more stuff out there that we haven't detected."

Approximately every 80 years, a faint 10th magnitude star in the constellation of Corona Borealis dramatically increases its brightness. This star, T CrB, is known as a recurrent nova and last flared in 1946, peaking at magnitude 2.0, temporarily making it one of the 50 brightest stars in the night sky.

Aside from the 1946 eruption, the only other confirmed observation of this star's outburst was in 1866. But new research by Dr. Bradley Schaefer suggests that a medieval monk may have spied T CrB brightening in 1217.

In medieval monasteries, monks would regularly keep chronicles - a list of notable events that happened throughout the year. In 1217, the abbot of Ursberg Abbey (in southern Germany, west of Augsberg) was Burchard. In the chronicle for that year, he wrote:

In the autumn season of [1217], in the early evening, a wonderful sign was seen in a certain star in the west. This star was located a little west of south, in what astrologers call Ariadne's Crown [Corona Borealis]. As we ourselves have observed, it was originally a faint star that, for a time, shone with great light, and then returned to its original faintness. There was also a very bright ray reaching up the sky, like a large tall beam. This was seen for many days that autumn.

But was this "wonderful sign" a nova, or one of many other types of transient events that could grace the night sky?

Alex Filippenko is the kind of guy who brings a telescope to a party. True to form, at a soiree on May 18 this year, he wowed his hosts with images of star clusters and colorful galaxies — including the dramatic spiral Pinwheel Galaxy — and snapped telescopic photos of each.

Only late the next afternoon did he learn that a bright supernova had just been discovered in the Pinwheel Galaxy. Lo and behold, he'd also captured it, at 11 p.m. the night before — 11 and a half hours before the explosion's discovery on May 19 by amateur astronomer Koichi Itagaki in Japan.

Filippenko, a professor of astronomy at the University of California, Berkeley, graduate student Sergiy Vasylyev and postdoctoral fellow Yi Yang threw out their planned observations at the UC's Lick Observatory on Mount Hamilton a few hours later to focus on the exploding star, which had been dubbed SN 2023ixf. They and hundreds of other astronomers were eager to observe the nearest supernova since 2014, a mere 21 million light years from Earth.

These observations were the earliest-ever measurements of polarized light from a supernova, showing more clearly the evolving shape of a stellar explosion. The polarization of light from distant sources like supernovae provides the best information on the geometry of the object emitting the light, even for events that cannot be spatially resolved.

"Some stars prior to exploding go through undulations — fitful behavior that gently ejects some of the material — so that when the supernova explodes, either the shock wave or the ultraviolet radiation causes the stuff to glow," Filippenko said. "The cool thing about the spectropolarimetry is that we get some indication of the shape and extent of the circumstellar material."

The spectropolarimetry data told a story in line with current scenarios for the final years of a red supergiant star about 10 to 20 times more massive than our sun: Energy from the explosion lit up clouds of gas that the star shed over the previous few years; the ejecta then punched through this gas, initially perpendicular to the bulk of the circumstellar material; and finally, the ejecta engulfed the surrounding gas and evolved into a rapidly expanding, but symmetric, cloud of debris.

A captivating and unusual meteorological phenomenon, known as Mammatus clouds, recently graced the skies of China's Hubei province.

A fast stream of solar wind hit Earth over the weekend, sparking a rare display of August auroras around the Arctic Circle. "On Saturday, Aug. 19th, I got to see my first Northern Lights of the season," reports Göran Strand, who sends this picture from Östersund, Sweden (latitude +63N):

In the Arctic, August auroras are extra-special because the glow of the Midnight Sun has not yet faded away. This gives observers a chance of see a mix of colors: Twilight blue and geomagnetic green. "Blue night-sky auroras are so beautiful with a warm horizon at the bottom," notes Strand.

More than 200 km inside the Arctic Circle, an automated camera at the STF Turiststation in Abisko, Sweden, photographed the same display. "This is the earliest we have seen auroras in at least 17 years," says Chad Blakley of Lights over Lapland. "Our automated camera has been in operation since 2005-2006. I checked the archives. Aug. 19, 2023, is the earliest display on record, edging out Aug. 20, 2013 by a single day."

The early start to aurora season highlights the increasing strength of Solar Cycle 25, now racing toward a Solar Max expected as early as next year. Earth's magnetosphere is buzzing with energy, and it only takes a single stream of solar wind to light up our planet's poles. Note to Arctic sky watchers: Be alert for green+blue in the weeks ahead as the Midnight Sun fades to black. Aurora alerts: SMS Text

Increases in CO₂ in the atmosphere brought about by anthropogenic activity was expected to increase the rate of photosynthesis in plants and perhaps increase plant yield and growth.

New science has showed the rate of photosynthesis around the globe has been increasing, but now there is evidence the rate has slowed and might soon plateau.

During photosynthesis plants take water and CO₂ and convert it into oxygen and carbohydrates - storing carbon inside the plant and soil. A higher availability of CO₂ increases the rate of this process, acting as a sort of brake on global warming by sequestering more CO₂.