Astronomy

Concern over the risks of enabling nuclear weapons development is usually focused on nuclear fission reactors, but the potential harm from more advanced fusion reactors has been underappreciated

Concern over the risks of enabling nuclear weapons development is usually focused on nuclear fission reactors, but the potential harm from more advanced fusion reactors has been underappreciated

Europe’s newest rocket soon launches, taking with it many space missions each with a unique objective, destination and team at home, cheering them on. Whether launching new satellites to look back and study Earth, peer out to deep space or test important new technologies in orbit, Ariane 6’s first flight will showcase the versatility and flexibility of this impressive, heavy-lift launcher. Read on for all about 3Cat-4, then see who else is flying first.

Researchers are aiming to make the northern quoll resistant to the toxic cane toads wiping it out in Australia, but little progress has been made

Researchers are aiming to make the northern quoll resistant to the toxic cane toads wiping it out in Australia, but little progress has been made

Majestic on a truly cosmic scale, M100 is appropriately known as a

Global temperatures in April 2024 were 1.6°C higher than the average for April during the pre-industrial era

Global temperatures in April 2024 were 1.6°C higher than the average for April during the pre-industrial era

Birman and Burmese cats typically live for more than 14 years while sphynxes live less than half as long on average, finds a study of pet cats in the UK

Birman and Burmese cats typically live for more than 14 years while sphynxes live less than half as long on average, finds a study of pet cats in the UK

The Gum Nebula is an emission nebula almost 1400 light-years away. It’s home to an object known as “God’s Hand” among the faithful. The rest of us call it CG 4.

Many objects in space take on fascinating, ethereal shapes straight out of someone’s psychedelic fantasy. CG4 is definitely ethereal and extraordinary, but it’s also a little more prosaic. It looks like a hand extending into space.

The Dark Energy Camera (DECam) on the NSF’s Víctor M. Blanco 4-meter Telescope captured the image. DECam’s primary job is to survey hundreds of millions of galaxies in its study of dark energy. But it’s also a general-purpose instrument used for other scientific endeavours.

CG 4 is called a cometary globule because of its appearance. But it’s actually a star-forming region. It has a head that’s about 1.5 light-years in diameter and a tail that’s about 8 light-years long. The head is dense and opaque and is lit up by a nearby star. The globule is surrounded by a diffuse red glow, emissions from ionized hydrogen.

This excerpt shows a close-up of CG 4. The hand looks like it’s about to grasp an edge-on spiral galaxy named ESO 257-19 (PGC 21338). But the galaxy is more than a hundred million light-years beyond CG 4. Only a chance alignment makes it seem close. Near the head of the cometary globule are two young stellar objects (YSOs). They’re stars in their early stage of evolution before they become main-sequence stars. Image Credits: Credit: CTIO/NOIRLab/DOE/NSF/AURA
Image Processing: T.A. Rector (University of Alaska Anchorage/NSF’s NOIRLab), D. de Martin & M. Zamani (NSF’s NOIRLab)

There are lots of cometary globules in the Milky Way. They’re a sub-class of objects called Bok globules, after astronomer Bart Bok, who discovered them. Both types of globules are dark nebulae, molecular clouds so dense they block optical light. Astronomers aren’t absolutely certain how cometary globules get their shape.

But they do know what’s happening to them.

The red glow surrounding CG 4 is ionized hydrogen lit up by radiation from nearby hot, massive stars. That same radiation is eroding CG 4 away. Since the globule is denser than its surroundings, it’s resisting diffusion. It still contains enough gas and dust to form several new stars about as massive as the Sun.

In this zoom-in, the hand looks more like the mouth of the Shai-Hulud, reaching out into space to destroy the approaching Sardaukar. Image Credit: CTIO/NOIRLab/DOE/NSF/AURA. Image Processing: T.A. Rector (University of Alaska Anchorage/NSF’s NOIRLab), D. de Martin & M. Zamani (NSF’s NOIRLab)

Even though there are many of these globules in the Milky Way, the majority of them are in the Gum Nebula. Scientists know of 31 other globules in the nebula. This one’s called CG 4 (Cometary Globule 4) because they’re all numbered.

This image shows three of the 32 CGs in the Gum Nebula: CG 30, 31, and 8. Image Credit: By Legacy Surveys / D.Lang (Perimeter Institute) & Meli Thev – Own work, CC BY 4.0, https://commons.wikimedia.org/w/index.php?curid=143429111

The Gum Nebula is likely the remnant of a huge supernova explosion, and that could be the reason the globules have their unique shape. They may have originally been spherical nebula like the Ring Nebula. But a powerful supernova explosion about one million years ago stretched them into their long, comet-like forms.

The James Webb Space Telescope captured this image of the Southern Ring Nebula, or NGC 3132, with its NIRCAM instrument. Cometary globules could’ve started out as ring-shaped nebulae before being deformed by supernova explosions. Image Credit: By Image: NASA/ESA/CSA/Space Telescope Science Institute. Public Domain

Astronomers also suggest another reason for their shape. Nearby hot, massive stars exert radiation pressure on the globules, and their stellar wind also slams into them. In the Gum Nebula, their tails point away from the Vela Supernova Remnant and the pulsar that sits in its centre. Since the Vela Pulsar is a spinning neutron star, it’s possible that its winds and radiation pressure are shaping CG 4.

Whatever its cause, the Hand of God is a visually intriguing object. If you really want to lose yourself in this amazing nebula, download the TIFF file here.

The post A Nebula that Extends its Hand into Space appeared first on Universe Today.

The rapid growth of solar power led to a record-breaking year for clean energy generation in 2023, and the year is expected to mark the start of a long-term decline in fossil fuels

The rapid growth of solar power led to a record-breaking year for clean energy generation in 2023, and the year is expected to mark the start of a long-term decline in fossil fuels

Earth is naked without its protective barrier. The planet’s magnetic shield surrounds Earth and shelters it from the natural onslaught of cosmic rays. But sometimes, the shield weakens and wavers, allowing cosmic rays to strike the atmosphere, creating a shower of particles that scientists think could wreak havoc on the biosphere.

This has happened many times in our planet’s history, including 41,000 years ago in an event called the Laschamps excursion.

Cosmic rays are high-energy particles, usually protons or atomic nuclei, that travel through space at relativistic speeds. Normally, they’re deflected into space and away from Earth by the planet’s magnetic shield. But the shield is a natural phenomenon and its strength fluctuates, as does its orientation. When that happens, cosmic rays strike the Earth’s atmosphere.

That creates a shower of secondary particles called cosmogenic radionuclides. These isotopes become embedded in sediments and ice cores and even in the structure of living things like trees. There are different types of these isotopes, including ones like Calcium 41 and Carbon 14.

Showers of high-energy particles occur when energetic cosmic rays strike the top of the Earth’s atmosphere. Illustration Credit: Simon Swordy (U. Chicago), NASA.

Some of the isotopes are stable, and some are radioactive. The radioactive ones have half-lives ranging from only 20 minutes (Carbon 11) up to 15.7 million years (Xenon 129.)

When Earth’s shield weakens, more of these isotopes reach the planet’s surface and collect in sediments and ice. By studying these cores and sediments, scientists can determine the magnetic shield’s history. Their observations show that Earth experienced a geomagnetic excursion or reversal 41,000 years ago. It’s called the Laschamps excursion after the Laschamps lava flows in France, where geomagnetic anomalies revealed its occurrence.

Every few hundred thousand years, the Earth’s magnetic poles flip. North becomes South and vice versa. In between those major events are more minor events called excursions. During excursions, the poles shift around for a while without swapping places. The excursions weaken the Earth’s shield and can last from a few thousand to tens of thousands of years. When that happens, more cosmic rays strike the atmosphere, creating more radionuclides that shower down onto Earth.

Scientists often focus on one particular radioactive isotope in paleomagnetic studies. Beryllium 10 has a relatively long half-life of 1.36 million years and tends to accumulate on the soil surface.

Sanja Panovska is a researcher at GFZ Potsdam, Germany, who studies geomagnetism. At the recent European Geosciences Union (EGU) General Assembly 2024, Panovska presented new research on the Laschamps excursion. She found that during the Laschamps excursion, production of Be 10 was twice as high as normal.

To understand the Laschamps excursion more thoroughly, Panovska combined cosmogenic radionuclide and paleomagnetic data to reconstruct the Earth’s magnetic field at the time. She found that when the field decreased in strength, it also shrank. The transition from normal field to reversed field took about 250 years, and it stayed flipped for about 440 years. During the transition, the Earth’s shield weekend to as little as 5% of its normal strength. When it was fully reversed, it was at about 25% of its regular strength. This weakening allowed more Be 10 and other cosmogenic radionuclides to reach Earth’s surface.

Each map shows the intensity of Earth’s geomagnetic field at different snapshots in time, according to Panovska’s reconstructions that are constrained by both paleomagnetic data and records of cosmogenic beryllium-10 radionuclides. DM stands for Dipole Moment, which is a measure of the field’s polarity or separation of positive and negative. Age [ka BP] is the age measures in thousands of years before the present. Image Credit: Sanja Panovska.

These radionuclides do more than collect in sediments and ice. Some of them are radioactive. The weakening of the shield also weakened the ozone layer, letting more UV radiation reach Earth’s surface. The high-altitude atmosphere also cooled, which changed the wind flows. This could’ve caused drastic changes on the Earth’s surface.

For these reasons, the Laschamps event has been linked to the extinction of the Neanderthals, the extinction of Australian megafauna, and even to the appearance of cave art. Those links haven’t withstood scientific scrutiny, but that doesn’t mean that events like the Laschamps event aren’t hazardous. If it occurred now, it would knock out our power grids. The Earth’s equatorial region would light up with aurorae.

“Understanding these extreme events is important for their occurrence in the future, space climate predictions, and assessing the effects on the environment and on the Earth system,” Panovska said.

Scientists are learning that the magnetic shield isn’t static. There are anomalies. One of them is the South Atlantic Anomaly, a region where the magnetic field is weakest near Earth. When satellites pass over this region, they’re exposed to higher levels of ionizing radiation. The anomaly is likely caused by a reservoir of dense rock inside Earth, illustrating how complex the magnetic shield is.

The ‘South Atlantic Anomaly’ refers to an area where Earth’s protective magnetic shield is weak. Image Credit: By Christopher C. Finlay, Clemens Kloss, Nils Olsen, Magnus D. Hammer, Lars Tøffner-Clausen, Alexander Grayver & Alexey Kuvshinov – “The CHAOS-7 geomagnetic field model and observed changes in the South Atlantic Anomaly”, Earth, Planets and Space, Volume 72, Article number 156 (2020), https://earth-planets-space.springeropen.com/articles/10.1186/s40623-020-01252-9, CC BY-SA 4.0, https://commons.wikimedia.org/w/index.php?curid=99760567

Scientists are uncertain about what effect the cosmic rays have on life when the magnetic shield is weak. It’s tempting to correlate extinctions with events like the Laschamps excursion when they line up temporally. But the poles have shifted, weakened, and reversed many times and life is still here and still thriving.

If humanity lasts long enough, we’ll go through one of these reversals. Then we’ll know.

The post 41,000 Years Ago Earth’s Shield Went Down appeared first on Universe Today.

No human being will ever encounter a black hole. But we can’t stop wondering what it would be like to fall into one of these massive, beguiling, physics-defying singularities.

NASA created a simulation to help us imagine what it would be like.

Jeremy Schnittman is an astrophysicist at NASA’s Goddard Space Flight Center and he created the visualizations. “People often ask about this, and simulating these difficult-to-imagine processes helps me connect the mathematics of relativity to actual consequences in the real universe,” he said. “So I simulated two different scenarios, one where a camera — a stand-in for a daring astronaut — just misses the event horizon and slingshots back out, and one where it crosses the boundary, sealing its fate.”

In one, the viewpoint plunges directly into the black hole like a free-falling astronaut, with explanatory text to guide us through what we’re seeing. The other is a 360-degree view of the black hole.

Schnittman created them with a NASA supercomputer called Discover in only five days, generating about 10 terabytes of data. The computer used only about 0.3% of its power. The same visualization would’ve taken more than a decade to create on an average laptop computer.

The black hole in the visualization is the same size as Sagittarius A star, the supermassive black hole (SMBH) at the heart of the Milky Way. It has 4.3 million solar masses and dominates the galaxy’s inner regions. Its event horizon reaches about 25 million km (16 million miles). That’s about 17% of the distance from Earth to the Sun. The event horizon is surrounded by an accretion disk, a swirling disk of superheated material drawn in by the black hole’s overpowering gravity.

Another type of black hole, the stellar-mass black hole, is much less massive. Schnittman says that if you’re going to fall into a black hole, you’d rather fall into the supermassive one.

“If you have the choice, you want to fall into a supermassive black hole,” Schnittman explained. “Stellar-mass black holes, which contain up to about 30 solar masses, possess much smaller event horizons and stronger tidal forces, which can rip apart approaching objects before they get to the horizon.”

Powerful gravity is the reason. The SMBH’s gravity is so strong that it pulls harder on the end of the object nearest it. That stretches the object and elongates it. Stephen Hawking was the first to call this ‘spaghettification,’ and the name has stuck. Presumably, you’d get a better look if you fall into an SMBH.

In the movies, the camera begins at a distance of 640 million km (400 million miles.) Since space-time is warped around a black hole, so are the images of the sky, the black hole’s disk, and the photon ring. It takes the camera three hours of real-time to fall into the event horizon, and it completes almost two 30-minute orbits as it falls. A distant observer would never see an object ever reach the black hole. From a distance, the object would freeze at the event horizon.

When a falling object reaches the event horizon, it and space-time itself reach the speed of light. After crossing the horizon, the object and the space-time around it surge toward the singularity, a point of infinite density and gravity. “Once the camera crosses the horizon, its destruction by spaghettification is just 12.8 seconds away,” Schnittman said.

In the second video, the camera never crosses the event horizon and instead escapes. But the powerful black hole still has an effect. Imagine if the camera were an astronaut, and they flew this six-hour roundtrip while a separate astronaut stayed far away from the SMBH. The astronaut would return and be 36 minutes younger than the astronaut who never approached the black hole.

“This situation can be even more extreme,” Schnittman noted. “If the black hole were rapidly rotating, like the one shown in the 2014 movie ‘Interstellar,’ she would return many years younger than her shipmates.”

The bottom line is, don’t fall into a black hole. In fact, resist your fascination and don’t even approach one.

Leave them for the physicists.

The post Fall Into a Black Hole With this New NASA Simulation appeared first on Universe Today.

From tracking hazards in the ocean to predicting the strength of hurricanes, NOAA's GeoXO series continues on the legacy of the GOES-R series — but with exciting upgrades.

The rings that circle gas giants like Saturn are composed mostly of water-ice particles. Could life exist in these beautiful and enigmatic structures?

This image of Jupiter’s iconic Great Red Spot and surrounding turbulent zones was captured by NASA’s Juno spacecraft. The color-enhanced image is a combination of three separate images taken on April 1, 2018, as Juno performed its 12th close flyby of Jupiter. At the time the images were taken, the spacecraft was 15,379 miles (24,749 kilometers) to 30,633 miles (49,299 kilometers) from the tops of the clouds of the planet.

The mystery of how early universe supermassive black holes grew so quickly may be solved, with the James Webb Space Telescope finding the first evidence of "heavy seeds."