The Cosmic Conundrum: A Billion-Light-Year Hole Around Earth Unmasks Faster Space Expansion

Astronomers have long been puzzled by the discrepancy in the measured expansion rate of the universe, which they refer to as the Hubble tension. This conundrum has left scientists searching for a solution, and recent research suggests that our galaxy might be situated within a massive, billion-light-year hole that makes the cosmos expand faster here than in neighboring regions.

The idea is not new, but it gained momentum with the latest study presented at the Royal Astronomical Society’s National Astronomy Meeting (NAM) in Durham. The researchers’ theory proposes that our galaxy sits near the center of a large, local void, which would cause matter to be pulled by gravity towards the higher-density exterior of the void.

As the void empties out over time, the velocity of objects away from us would increase, giving the appearance of a faster local expansion rate. This potential solution to the Hubble tension is largely a local phenomenon, with little evidence that the expansion rate disagrees with expectations in the standard cosmology further back in time.

The researchers also used baryon acoustic oscillations (BAOs) – essentially the sound waves from the early universe – to support their theory. These sound waves travelled for only a short while before becoming frozen in place once the universe cooled enough for neutral atoms to form. They act as a standard ruler, whose angular size can be used to chart the cosmic expansion history.

By considering all available BAO measurements over the last 20 years, the researchers showed that a void model is about one hundred million times more likely than a void-free model with parameters designed to fit the CMB observations taken by the Planck satellite, the so-called homogeneous Planck cosmology.

The next step for researchers is to compare their local void model with other methods to estimate the history of the universe’s expansion. This involves looking at galaxies that are no longer forming stars and observing their spectra or light to find what kinds of stars they have and in what proportion.

Astronomers can then combine this age with the galaxy’s redshift – how much the wavelength of its light has been stretched – which tells us how much the universe has expanded while light from the galaxy was traveling towards us. This sheds light on the universe’s expansion history.

The Hubble constant was first proposed by Edwin Hubble in 1929 to express the rate of the universe’s expansion. It can be measured by observing the distance of celestial objects and how fast they are moving away from us. The Hubble tension refers to the discrepancy in the measured expansion rate of the universe, specifically between the value based on observations of the early universe and the value related to observations of the local universe.

Baryon acoustic oscillations provide an independent way to measure the expansion rate of the universe and how that rate has changed throughout cosmic history. The discovery of a billion-light-year hole around Earth might be just the solution scientists need to unravel the mysteries of the cosmos.

NASA’s Parker Solar Probe has captured stunning new images from within the Sun’s atmosphere, revealing the origins of solar storms that can affect Earth. The probe, which flew closer to the Sun than ever before, has helped scientists better understand the Sun’s influence across the solar system.

The newly released images show the corona and solar wind, a constant stream of electrically charged particles from the Sun that rage across the solar system. The solar wind expands throughout the solar system with wide-ranging effects, including generating auroras, stripping planetary atmospheres, and inducing electric currents that can overwhelm power grids and affect communications at Earth.

Understanding the impact of solar wind starts with understanding its origins at the Sun. The WISPR images give scientists a closer look at what happens to the solar wind shortly after it is released from the corona. The images show the important boundary where the Sun’s magnetic field direction switches from northward to southward, called the heliospheric current sheet.

The collision of multiple coronal mass ejections (CMEs), or large outbursts of charged particles, has been captured for the first time in high resolution. “In these images, we’re seeing the CMEs basically piling up on top of one another,” said Angelos Vourlidas, the WISPR instrument scientist at the Johns Hopkins Applied Physics Laboratory.

When CMEs collide, their trajectory can change, making it harder to predict where they’ll end up. Their merger can also accelerate charged particles and mix magnetic fields, which makes the CMEs’ effects potentially more dangerous to astronauts and satellites in space and technology on the ground.

The solar wind was first theorized by preeminent heliophysicist Eugene Parker in 1958. His theories about the solar wind, which were met with criticism at the time, have now been confirmed through Parker Solar Probe’s close-up views of the Sun.

As it spiraled closer to the Sun, Parker Solar Probe helped scientists pinpoint the origin of switchbacks at patches on the visible surface of the Sun where magnetic funnels form. The fast solar wind, which travels at just 220 miles per second, has been shown to be in part powered by these switchbacks, adding to a 50-year-old mystery.

The slow solar wind, which is twice as dense and more variable than fast solar wind, is important to study because its interplay with the fast solar wind can create moderately strong solar storm conditions at Earth sometimes rivaling those from CMEs. Prior to Parker Solar Probe, distant observations suggested there are actually two varieties of slow solar wind, distinguished by the orientation or variability of their magnetic fields.

One type of slow solar wind, called Alfvénic, has small-scale switchbacks. The second type, called non-Alfvénic, doesn’t show these variations in its magnetic field. As it spiraled closer to the Sun, Parker Solar Probe confirmed there are indeed two types.

Its close-up views are also helping scientists differentiate the origins of the two types, which scientists believe are unique. The non-Alfvénic wind may come off features called helmet streamers — large loops connecting active regions where some particles can heat up enough to escape — whereas Alfvénic wind might originate near coronal holes, or dark, cool regions in the corona.

In its current orbit, bringing the spacecraft just 3.8 million miles from the Sun, Parker Solar Probe will continue to gather additional data during its upcoming passes through the corona to help scientists confirm the slow solar wind’s origins. The next pass comes Sept. 15, 2025.

The cosmic explosion that marks the end of a star’s life has long been a topic of fascination for astronomers. For the first time, scientists have captured visual evidence of a star meeting its end by detonating twice. The remains of supernova SNR 0509-67.5, studied with the European Southern Observatory’s Very Large Telescope (ESO’s VLT), show patterns that confirm its star suffered a pair of explosive blasts.

The explosions of white dwarfs play a crucial role in astronomy. Much of our knowledge of how the Universe expands rests on Type Ia supernovae, and they are also the primary source of iron on our planet, including the iron in our blood. However, despite their importance, the exact mechanism triggering these explosions remains unsolved.

All models that explain Type Ia supernovae begin with a white dwarf in a pair of stars. If it orbits close enough to the other star in this pair, the dwarf can steal material from its partner. In the most established theory behind Type Ia supernovae, the white dwarf accumulates matter from its companion until it reaches a critical mass, at which point it undergoes a single explosion.

However, recent studies have hinted that at least some Type Ia supernovae could be better explained by a double explosion triggered before the star reached this critical mass. This alternative model suggests that the white dwarf forms a blanket of stolen helium around itself, which can become unstable and ignite. This first explosion generates a shockwave that travels around the white dwarf and inwards, triggering a second detonation in the core of the star — ultimately creating the supernova.

Until now, there had been no clear, visual evidence of a white dwarf undergoing a double detonation. Recently, astronomers have predicted that this process would create a distinctive pattern or fingerprint in the supernova’s still-glowing remains, visible long after the initial explosion. Research suggests that remnants of such a supernova would contain two separate shells of calcium.

Astronomers have now found this fingerprint in a supernova’s remains. Ivo Seitenzahl, who led the observations and was at Germany’s Heidelberg Institute for Theoretical Studies when the study was conducted, says these results show “a clear indication that white dwarfs can explode well before they reach the famous Chandrasekhar mass limit, and that the ‘double-detonation’ mechanism does indeed occur in nature.”

The team were able to detect these calcium layers (in blue in the image) in the supernova remnant SNR 0509-67.5 by observing it with the Multi Unit Spectroscopic Explorer (MUSE) on ESO’s VLT. This provides strong evidence that a Type Ia supernova can occur before its parent white dwarf reaches a critical mass.

Type Ia supernovae are key to our understanding of the Universe. They behave in very consistent ways, and their brightness allows them to be seen from vast distances. By studying these cosmic events, scientists gain insights into the life cycles of stars and the evolution of the cosmos itself.

The discovery of a double-detonation mechanism in Type Ia supernovae has significant implications for our understanding of the Universe. It suggests that these explosions can occur at different stages of a star’s life, potentially leading to new observations and a deeper understanding of the cosmic web.

As scientists continue to study the remnants of supernova SNR 0509-67.5, they may uncover more secrets about the double-detonation mechanism and its role in shaping the Universe. The findings of this research have far-reaching implications for our understanding of the cosmos and the life cycles of stars.