News Feeds

Neolithic people buried hundreds of stones carved with images of the sun about 4900 years ago and they may have done it because a volcanic eruption covered the sky

The ESA has announced that Gaia’s primary mission is coming to an end. The spacecraft’s fuel is running low, and the sky-scanning phase of its mission is over. The ground-breaking mission has taken more than three trillion observations of two billion objects, mostly stars.

The ESA launched Gaia in December 2013. It’s an astrometry mission that measures the positions, motions, and distances of stars with extreme accuracy. It created the largest and most accurate 3D map of space ever, including about one billion objects, mostly stars but also quasars, comets, asteroids, and planets.

Gaia’s mission lasted twice as long as expected, and its data has changed astronomy. It serves as the foundation for many new discoveries and insights into the Milky Way. Astronomy and astrophysics would be far behind where they are now if it weren’t for Gaia. Regular Universe Today readers have encountered its data frequently.

“Today marks the end of science observations and we are celebrating this incredible mission that has exceeded all our expectations, lasting for almost twice its originally foreseen lifetime,” says ESA Director of Science Carole Mundell. “The treasure trove of data collected by Gaia has given us unique insights into the origin and evolution of our Milky Way galaxy, and has also transformed astrophysics and Solar System science in ways that we are yet to fully appreciate. Gaia built on unique European excellence in astrometry and will leave a long-lasting legacy for future generations.”

Gaia hasn’t always had it easy at its position at the Sun-Earth L2 Lagrange point, about 1.5 million kilometres from Earth. In April 2024, a tiny micrometeorite smaller than a grain of sand struck, puncturing a tiny hole in the satellite’s protective cover. The hole allowed a tiny bit of sunlight into the spacecraft, disrupting its sensors. In May 2024, a solar storm struck, and it suffered an electronics malfunction that led to an inordinately high number of false detections. In both cases, Gaia recovered and continued normal operations.

Gaia has three instruments that allow it to be so accurate. Its astrometric instrument (ASTRO) determines the positions of stars in the sky. By measuring the same stars multiple times over different years, Gaia can measure a star’s position and proper motion.

Gaia’s radial velocity spectrometer (RVS) measures the Doppler shift of a star’s absorption lines. This reveals the star’s velocity along Gaia’s line of sight.

The photometric instrument (BP/RP) provides colour information on stars, allowing astronomers to measure critical stellar characteristics like mass, chemical composition, and temperature.

These instruments have worked together to create the largest and most accurate map of the Milky Way ever.

A model image of what our home galaxy, the Milky Way, might look like face-on: as viewed from above the disc of the galaxy, with its spiral arms and bulge in full view. In the centre of the galaxy, the bulge shines as a hazy oval, emitting a faint golden gleam. Starting at the central bulge, several glistening spiral arms coil outwards, creating a perfectly circle-shaped spiral. They give the impression of someone having sprinkled pastel purple glitter on the pitch-black background in the shape of sparkling, curled-up snakes. Image Credit: ESA/Gaia/DPAC, Stefan Payne-Wardenaar

Among its other achievements, Gaia has captured pinpoint precision orbits of more than 150,000 asteroids, accurate enough to uncover possible moons. It also discovered a new type of black hole revealed only through its gravitational influence on nearby stars.

Though its science operations are at an end, it still has data to deliver.

“After 11 years in space and surviving micrometeorite impacts and solar storms along the way, Gaia has finished collecting science data. Now all eyes turn towards the preparation of the next data releases,” says Gaia Project Scientist Johannes Sahlmann.

“This is the Gaia release the community has been waiting for, and it’s exciting to think this only covers half of the collected data.”

Antonella Vallenari, Deputy Chair of DPAC, Istituto Nazionale di Astrofisica (INAF), Padua, Italy.

Gaia’s Data Release 4 (DR4) is expected in 2026. The volume and quality of data have increased with each DR. DR 4 should contain 500 terabytes of data covering the mission’s first 5.5 years, corresponding to the length of the mission’s originally foreseen duration.

“This is the Gaia release the community has been waiting for, and it’s exciting to think this only covers half of the collected data,” says Antonella Vallenari, Deputy Chair of DPAC based at the Istituto Nazionale di Astrofisica (INAF), Astronomical Observatory of Padua, Italy. “Even though the mission has now stopped collecting data, it will be business as usual for us for many years to come as we make these incredible datasets ready for use.”

The data release will feature more binary stars and exoplanets, among other things.

The Milky Way. This image is constructed from data from the ESA’s Gaia mission, which is mapping over one billion of the galaxy’s stars. Image Credit: ESA/Gaia/DPAC

Gaia’s final data release, DR5, is a few years away. “Over the next months we will continue to downlink every last drop of data from Gaia, and at the same time the processing teams will ramp up their preparations for the fifth and final major data release at the end of this decade, covering the full 10.5 years of mission data,” says Rocio Guerra, Gaia Science Operations Team Leader based at ESA’s European Space Astronomy Centre (ESAC) near Madrid in Spain.

Though the fuel that allows it to point itself with such accuracy is almost gone, Gaia won’t meet its demise just yet. It still has enough fuel for about 15 days of operations. Instead of using its final 15 days to take more astrometric measurements, it’s going to do some technology testing.

“The Gaia spacecraft has been constructed using a wide range of technologies which have been combined to create a unique machine that operates in a very stable environment,” the ESA explains. “The spacecraft’s stability is essential for the science observations. These technology tests would have disrupted the spacecraft for an extended period and, therefore, could not be performed during the normal science observation campaign.”

These tests will teach engineers more about Gaia’s instruments and will allow engineers to study their behaviour and the behaviour of the spacecraft as a whole. The goal is to improve the calibrations for future Gaia data releases. They will also inform the design of the next mission.

“Some of the Gaia technologies have already been re-used, for example the mirror-drive electronics and cold-gas thrusters on EUCLID,” the ESA writes. Other future missions like LISA will require extreme accuracy, and the results of these tests can help them achieve that.

Once its testing is complete, Gaia will be placed in a heliocentric orbit far away from Earth’s influence. At the end of March 2025, it will be passivated to avoid any potential harm or disruption to other spacecraft.

Though the mission will end, Gaia’s data will be used for decades. So, in that sense, it will live on.

The post The Gaia Mission’s Science Operations are Over appeared first on Universe Today.

For humans, the most important star in the universe is our Sun. The second-most important star is nestled inside the Andromeda galaxy. Don't go looking for it -- the flickering star is 2.2 million light-years away, and is 1/100,000th the brightness of the faintest star visible to the human eye. Yet, a century ago, its discovery by Edwin Hubble opened humanity's eyes as to how large the universe really is, and revealed that our Milky Way galaxy is just one of hundreds of billions of galaxies in the universe ushered in the coming-of-age for humans as a curious species that could scientifically ponder our own creation through the message of starlight.

A new analysis of data from the PHENIX experiment at the Relativistic Heavy Ion Collider (RHIC) reveals fresh evidence that collisions of even very small nuclei with large ones might create tiny specks of a quark-gluon plasma (QGP). Scientists believe such a substance of free quarks and gluons, the building blocks of protons and neutrons, permeated the universe a fraction of a second after the Big Bang.

For decades there has been near constant progress in reducing the size, and increasing the performance, of the circuits that power computers and smartphones. But Moore's Law is ending as physical limitations -- such as the number of transistors that can fit on a chip and the heat that results from packing them ever more densely -- are slowing the rate of performance increases. Computing capacity is gradually plateauing, even as artificial intelligence, machine learning and other data-intensive applications demand ever greater computational power.

For decades there has been near constant progress in reducing the size, and increasing the performance, of the circuits that power computers and smartphones. But Moore's Law is ending as physical limitations -- such as the number of transistors that can fit on a chip and the heat that results from packing them ever more densely -- are slowing the rate of performance increases. Computing capacity is gradually plateauing, even as artificial intelligence, machine learning and other data-intensive applications demand ever greater computational power.

Engineers have found a way to eliminate the fluid flow 'dead zones' that plague the types of electrodes used for battery-based seawater desalination. The new technique uses a physics-based tapered flow channel design within electrodes that moves fluids quickly and efficiently, potentially requiring less energy than reverse osmosis techniques currently require.

New insect-scale microrobots can fly more than 100 times longer than previous versions. The new bots, also significantly faster and more agile, could someday be used to pollinate fruits and vegetables.

New insect-scale microrobots can fly more than 100 times longer than previous versions. The new bots, also significantly faster and more agile, could someday be used to pollinate fruits and vegetables.

Researchers have demonstrated new wearable technologies that both generate electricity from human movement and improve the comfort of the technology for the people wearing them. The work stems from an advanced understanding of materials that increase comfort in textiles and produce electricity when they rub against another surface.

Researchers have designed process that uses ultrasound to modify the behavior of cancer-fighting T cells by increasing their cell permeability. They targeted freshly isolated human immune cells with tightly focused ultrasound beams and clinically approved contrast agent microbubbles. When hit with the ultrasound, the bubbles vibrate at extremely high frequency, acting as a push-pull on the walls of the T cell's membranes. This can mimic the T cell's natural response to the presence of an antigen. The T cell then begins to secrete vital signalling molecules that would otherwise be restricted by the tumor's hostile microenvironment. The process does not damage the cell itself.

A new initiative is challenging the conversation around the direction of artificial intelligence (AI). It charges that the current trajectory is inherently biased against non-Western modes of thinking about intelligence -- especially those originating from Indigenous cultures. Abundant Intelligences is an international, multi-institutional and interdisciplinary program that seeks to rethink how we conceive of AI. The driving concept behind it is the incorporation of Indigenous knowledge systems to create an inclusive, robust concept of intelligence and intelligent action, and how that can be embedded into existing and future technologies.

A new initiative is challenging the conversation around the direction of artificial intelligence (AI). It charges that the current trajectory is inherently biased against non-Western modes of thinking about intelligence -- especially those originating from Indigenous cultures. Abundant Intelligences is an international, multi-institutional and interdisciplinary program that seeks to rethink how we conceive of AI. The driving concept behind it is the incorporation of Indigenous knowledge systems to create an inclusive, robust concept of intelligence and intelligent action, and how that can be embedded into existing and future technologies.

Astronomers have detected an intensely brightening and dimming quasar that may help explain how some objects in the early universe grew at a highly accelerated rate. The discovery is the most distant object detected by the NuSTAR X-ray space telescope (which launched in 2012) and stands as one of the most highly 'variable' quasars ever identified.

Astronomers have detected an intensely brightening and dimming quasar that may help explain how some objects in the early universe grew at a highly accelerated rate. The discovery is the most distant object detected by the NuSTAR X-ray space telescope (which launched in 2012) and stands as one of the most highly 'variable' quasars ever identified.

Supermassive black holes can have trillions of times more mass than the Sun, only exist in specific locations, and could number in the trillions. How can objects like that be hiding? They’re shielded from our view by thick columns of gas and dust.

However, astronomers are developing a way to find them: by looking for donuts that glow in the infrared.

It seems almost certain that large galaxies like our own Milky Way host supermassive black holes (SMBHs) in their centers. They grow through mergers with other SMBHs and through accretion. When they’re actively accreting material, they’re called Active Galactic Nuclei (AGN) and become so bright they can outshine all of the stars in their entire galaxy. The most luminous AGN are called quasars.

SMBHs, like all black holes, emit no light themselves. Instead, the light comes from the torus of swirling gas and dust that forms an accretion ring around the SMBH. The gas and dust become superheated and emit electromagnetic radiation. So far, scientists have only imaged two SMBHs, both with the Event Horizon Telescope (EHT). (To be clear, the EHT doesn’t actually “see” the SMBH. Instead, it sees the light coming from the accretion disk and the shadow the SMBH casts on the disk.)

The first ever actual image of a black hole was taken in 2019. This shows the black hole at the heart of galaxy M87. Image Credit: Event Horizon Telescope Collaboration

Even without seeing them, astronomers are pretty certain that most large galaxies host an SMBH. How? Stars near the center of galaxies move in unusual ways as if they’re under the influence of an extremely massive object. The intense radiation from AGN is also strong evidence of an SMBH. Galaxy formation and evolution models and gravitational lensing provide additional evidence.

However, astronomers still want to find more of them so they can confirm their models or adapt them to suit observational results. The problem is that many of them are hidden from view by gas and dust. If that gas and dust are thick and dense enough, they act as a veil, blocking even low-energy X-ray light. That means our view of the galaxy centre is obscured, even if it is an AGN.

Whether or not we can see the centre of a galaxy like this depends on our viewing. From a “side” view, the torus blocks it out, while from a “top” or “bottom” view, it doesn’t.

Astronomers want to understand how many SMBHs there are in the Universe, but obviously, there’s no way to find them and count them all. What they hope to do is determine the ratio between hidden and unhidden SMBHs. To do that, they need a large enough sample to extrapolate from. That way, they can get a more accurate idea of how many SMBHs there are.

A new survey using data from multiple NASA telescopes has advanced our understanding of SMBHs. The survey and its results are detailed in a paper titled “The NuSTAR Local AGN NH Distribution Survey (NuLANDS). I. Toward a Truly Representative Column Density Distribution in the Local Universe.” It’s published in The Astrophysical Journal, and the lead author is Peter G. Boorman, an astrophysicist from the Cahill Center for Astrophysics at the California Institute of Technology.

The NuLANDS aims to find the thick dust and gas that obscures AGN. Previous efforts to detect AGN have been hampered by relying on hard X-rays, the highest-energy portion of the X-ray spectrum, often defined as X-rays with energies greater than 10 kiloelectronvolts (keV). Accretion disks around SMBHs can be heated to extremely high temperatures and emit hard X-rays.

However, thick enough gas and dust can block even hard X-rays. If the column density of the gas is too high, no hard X-rays can get through. “Hard X-ray-selected samples of active galactic nuclei (AGN) provide one of the cleanest views of supermassive black hole accretion but are biased against objects obscured by Compton-thick gas column densities of NH > 1024 cm-2,” the authors write in their paper. Compton-thick means thick enough to obscure an AGN.

The thick gas and dust that block hard X-rays absorb them and then re-emit them as lower-energy infrared light. This creates a glowing torus, or donut, of gas and dust. This is where IRAS comes in.

IRAS was the Infrared Astronomical Satellite, launched in January 1983 and operated for 10 months. It performed an infrared survey of the entire sky, and it spotted the infrared emissions from the toruses around SMBHs. Critically, it spotted these toruses whether they were face-on or edge-on.

However, IRAS didn’t discriminate against infrared sources. It also spotted galaxies undergoing rapid star formation, which emit similar infrared light as AGN. In this new research, the authors used ground-based telescopes to differentiate between the two.

At that stage, the researchers had a sample of toruses around SMBHs emitting infrared light. However, they didn’t know if they were seeing them face-on or edge-on. Remember, their goal was to determine how many SMBHs are hidden and how many aren’t. With a large enough sample containing good data, they could extrapolate how many SMBHs there are and whether all large galaxies have one.

This is where another NASA satellite comes in. NuSTAR is an X-ray space telescope that was launched in June 2012 and is still operating. One of its primary goals was to detect SMBHs one billion times more massive than the Sun.

An artist’s illustration of NASA’s NuSTAR X-ray satellite. Image Credit: NASA/JPL-Caltech

NuSTAR can detect high-energy X-rays that pass through thick dust and gas, so it can detect edge-on SMBHs. However, it can use hours of observation time to detect these X-rays, so for it to be effective, it has to know where to look first. That’s what IRAS helped with.

“It amazes me how useful IRAS and NuSTAR were for this project, especially despite IRAS being operational over 40 years ago,” said lead author Boorman. “I think it shows the legacy value of telescope archives and the benefit of using multiple instruments and wavelengths of light together.”

In their NuLANDS survey, the researchers looked at 122 nearby AGN chosen for their warm infrared colours. “To tackle this issue, we present the NuSTAR Local AGN NH Distribution Survey (NuLANDS)—a legacy sample of 122 nearby (z < 0.044) AGN primarily selected to have warm infrared colors from IRAS between 25 and 60 ?m,” the authors write.

Their sample of galaxies is also biased towards those whose AGN is obscured by something close to them rather than by some large-scale feature of the galaxy itself. “By construction, our sample will miss sources affected by severe narrow-line reddening, and thus segregates sources dominated by small-scale nuclear obscuration from large-scale host-galaxy obscuration,” the authors explain.

The researchers found that 35% ± 9% of galaxies have Compton-thick dust, meaning their AGN and SMBH are obscured. So, about one-third of the Universe’s SMBHs are obscured. However, these are only the first results from NuLANDS, and while 122 AGN is a sizeable survey, there’s more to come.

These results support some of the thinking around SMBHs, their masses, and their numbers. SMBHs must consume an enormous amount of material to reach their enormous sizes. That means many of them should be obscured by the very dust they’ll eventually consume. Boorman and his co-authors say their results support this idea.

“If we didn’t have black holes, galaxies would be much larger,” said study co-author Poshak Gandhi, a professor of astrophysics at the University of Southampton in the UK. That’s for two reasons. First, they consume material that would otherwise form more stars. Second, sometimes too much material falls toward the black hole, and they belch up the excess. That ejected material can disperse the clouds of gas where stars form, slowing the galaxy’s star formation.

“So if we didn’t have a supermassive black hole in our Milky Way galaxy, there might be many more stars in the sky. That’s just one example of how black holes can influence a galaxy’s evolution,” said Gandhi.

The post About a Third of Supermassive Black Holes are Hiding appeared first on Universe Today.

The shipping industry is planning to swap some fossil fuels for green ammonia – but that could create a major new source of nitrogen pollution

Most people don’t adhere to their New Year’s fitness resolutions. These science-backed tips can make you the exception

At his best, Iain M. Banks could be extraordinarily stylish, inventive and downright funny. So how does his genre-redefining science fiction stand up to the test of time? Emily H. Wilson rereads the greats

From windswept craters to frigid ice caps, explore Martian landscapes through the eyes of NASA’s orbiters, probes and rovers