Scots scientists help create largest 3D map of universe ever made
Using cutting-edge technology, the researchers spent five years gathering data from about 47 million galaxies and quasars. Source link
All posts tagged: Astronomy
Largest ever map of universe captures 47 million galaxies and quasars
A thin slice of the map produced by the DESI five-year survey shows galaxies and quasars above and below the plane of the Milky Way, with Earth at the centre Claire Lamman/DESI collaboration A five-year survey of the sky that has captured more than 47 million galaxies and quasars is now complete, enabling researchers to put the finishing touches on the most detailed map of the universe ever made. The data could help solve the mystery of an apparent weakening of dark energy, which threatens to upend our standard model of the cosmos. The Dark Energy Spectroscopic Instrument (DESI) at Kitt Peak National Observatory in Arizona has been scanning the sky since 2021. Researchers originally expected its survey to gather data on 34 million galaxies and quasars, but DESI surprised researchers with its efficiency. Because of the vast distances involved, some of these extremely faint galaxies have been observed from just 100 or 200 photons. David Schlegel at the Lawrence Berkeley National Laboratory in California says our previous maps of the cosmos include a total …
We’ve caught a comet switching its spin direction for the first time
An artist’s impression of comet 41P as it approached the sun and shot material off into space NASA, ESA, CSA, Ralf Crawford (STScI) A small comet seems to have switched the direction in which it is rotating – the first time astronomers have seen evidence of such behaviour. Changes like this may help us learn about the insides of comets, which could reveal information about the composition of the early solar system. Comet 41P/Tuttle-Giacobini-Kresák, or simply 41P, measures about 1 kilometre across and takes around 5.4 years to orbit the sun. We can only see it when it visits the inner solar system and its trajectory happens to take it relatively close to Earth. It was last seen in 2017. In March that year, it was rotating at a rate of about one full spin every 20 hours. When astronomers observed it just two months later, it had slowed down dramatically to one spin every 46 to 60 hours. Now, David Jewitt at the University of California, Los Angeles, has reanalysed observations from the Hubble …
Our local universe’s expansion rate doesn’t add up, astronomers find
A difference of a few kilometers per second might not sound like much. In cosmology, it has become one of the field’s most stubborn problems. An international team of astronomers has now delivered one of the sharpest direct measurements yet of how fast the nearby Universe is expanding, and the answer again lands on the high side. Their new value for the Hubble constant, the number used to describe that expansion rate, is 73.50 ± 0.81 kilometers per second per megaparsec. That is just over 1% precision. It also keeps the long-running Hubble tension very much alive. The result, published in Astronomy & Astrophysics, comes from the H0 Distance Network Collaboration, or H0DN. The project grew out of a March 2025 workshop at the International Space Science Institute in Bern, Switzerland, where researchers from across the field worked to build a shared framework for combining local measurements of cosmic distance. This graphic represents the tension that exists between measurements of the expansion rate of the late, nearby Universe, versus what would be expected based on …
Richard Feynman explains why our night sky is dark despite trillions of stars
A black patch of sky looks empty until you stop taking it for granted. That is the starting point of a theory from Professor Richard Feynman, built around what sounds like a child’s question, why the night sky is dark. The usual answer feels obvious. The sun sets, Earth rotates, and night falls. That explains why it is not daytime. It does not explain why the sky itself turns black. For centuries, astronomers and philosophers worked from a set of assumptions that seemed reasonable enough. The universe, they thought, was infinite. It had existed forever. And stars were spread through it more or less everywhere, even if they clustered in galaxies. Put those ideas together, and the darkness overhead starts to look strange. The way into the problem is visual. Picture yourself in a forest so vast it never ends. In a small forest, you can look between trunks and catch glimpses of open sky. In an infinite one, every line of sight eventually hits a tree. Shift your gaze slightly, and you miss the …
Astronomers discover a mysterious duality in dark matter
A dark matter signal that appears in one place but not another might look like a contradiction. This new study argues it may be something else entirely. At the center of the Milky Way, astronomers have long seen an excess of gamma rays, a form of high-energy light. That glow, known as the Galactic Center Gamma-Ray Excess, has remained one of the more intriguing clues in the hunt for dark matter. Some researchers think it could come from dark matter particles annihilating each other. Others argue it may come from more ordinary sources. In particular, they suggest a large population of faint millisecond pulsars could be responsible. A paper published in the Journal of Cosmology and Astroparticle Physics takes aim at one of the strongest objections to the dark matter idea. If dark matter is causing the gamma-ray excess near the Milky Way’s center, then why do dwarf galaxies, which are also packed with dark matter, not show the same kind of signal? According to the authors, that absence does not necessarily sink the dark …
Astronomers discover a mysterious duality in dark matter
A dark matter signal that appears in one place but not another might look like a contradiction. This new study argues it may be something else entirely. At the center of the Milky Way, astronomers have long seen an excess of gamma rays, a form of high-energy light. That glow, known as the Galactic Center Gamma-Ray Excess, has remained one of the more intriguing clues in the hunt for dark matter. Some researchers think it could come from dark matter particles annihilating each other. Others argue it may come from more ordinary sources. In particular, they suggest a large population of faint millisecond pulsars could be responsible. A paper published in the Journal of Cosmology and Astroparticle Physics takes aim at one of the strongest objections to the dark matter idea. If dark matter is causing the gamma-ray excess near the Milky Way’s center, then why do dwarf galaxies, which are also packed with dark matter, not show the same kind of signal? According to the authors, that absence does not necessarily sink the dark …
If the universe is full of stars then why is the night sky dark?
A black patch of sky looks empty until you stop taking it for granted. That is the starting point of a theory from Professor Richard Feynman, built around what sounds like a child’s question, why the night sky is dark. The usual answer feels obvious. The sun sets, Earth rotates, and night falls. That explains why it is not daytime. It does not explain why the sky itself turns black. For centuries, astronomers and philosophers worked from a set of assumptions that seemed reasonable enough. The universe, they thought, was infinite. It had existed forever. And stars were spread through it more or less everywhere, even if they clustered in galaxies. Put those ideas together, and the darkness overhead starts to look strange. The way into the problem is visual. Picture yourself in a forest so vast it never ends. In a small forest, you can look between trunks and catch glimpses of open sky. In an infinite one, every line of sight eventually hits a tree. Shift your gaze slightly, and you miss the …
Astronomers discovered the most primitive star ever
A dim red giant just out of reach of the Milky Way is providing astronomers with an incredibly rare glimpse into the earliest days of our universe, at a time when it was not possible for a telescope to observe these objects directly. The star SDSS J0715-7334 is located about 80,000 light-years away, and it resides near the Large Magellanic Cloud, a satellite galaxy of the Milky Way. Unlike most red giants, which are known for their large sizes and brilliant brightness, SDSS J0715-7334 is notable for being one of the most chemically primitive (metal-poor) stars discovered. In addition to being composed of nearly entirely hydrogen and helium, with traces of other elements, it contains less than 0.005 percent of the total metallic content of our sun. This star is significant because it has long been theorized that the first stars to form in our universe (Population III stars) were composed almost entirely of hydrogen and helium. Population III stars have never been directly observed, as it is believed that these were very massive stars …
What if dark matter came in two states?
The absence of a signal could itself be a signal. This is the idea behind a new study published in the Journal of Cosmology and Astroparticle Physics (JCAP), which aims to redefine how we search for dark matter, showing that it may not be necessary to find the same “clues” everywhere in order to interpret it. In particular, the study suggests that even if we observe a certain type of signal at the center of our galaxy — an excess of gamma radiation that could result from the annihilation of dark matter particles — failing to detect the same signal in other systems, such as dwarf galaxies, is not enough to rule out this explanation. Dark matter, in fact, may not consist of a single particle, but of multiple slightly different components, whose behavior varies depending on the cosmic environment. The galactic center gamma-ray excess Dark matter: we know it exists and is abundant, but we have never observed it directly and therefore we still do not know what it is. For decades, it has been …