Gravitational-Wave Observatories Should be Able to Detect Primordial Black Hole Mergers, if They’re out There

The early universe. Credit: Tom Abel & Ralf Kaehler (KIPACSLAC)/ AMNH/NASA

The tumultuous era of the big bang may have been chaotic enough to flood the universe with primordial black holes. Eventually some of those black holes will find each other and merge, sending out ripples of gravitational waves. A comprehensive search for those gravitational wave signatures hasn’t found anything, putting tight constraints on the abundance of these mysterious objects.

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Wind Speeds in Jupiter’s Great Red Spot are Picking up

Jupiter's Great Red Spot Region
Jupiter's Great Red Spot Region

The Great Red Spot of Jupiter – the largest storm in the solar system – has been raging for centuries. Over the past 100 years however, the cyclone has been dwindling, but recent observations with Hubble show that the wind speeds may be picking up again. Is this just temporary, or will the storm return to its former glory?

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Next-Generation Gravitational Wave Observatories Could Detect the First Stars When They Exploded as Supernovae

From the Ashes of the First Stars
From the Ashes of the First Stars

The first stars to appear in the universe are no longer with us – they died long ago. But when they died they released torrents of gravitational waves, which might still be detectable as a faint hum in the background vibrations of the cosmos.

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Early Massive Galaxies ran out of gas, Shutting Down Their Star Formation

This image taken by the NASA/ESA Hubble Space Telescope shows the galaxy NGC 4237. Located about 60 million light-years from Earth in the constellation of Coma Berenices (Berenice's Hair), NGC 4237 is classified as a flocculent spiral galaxy. This means that its spiral arms are not clearly distinguishable from each other, as in “grand design” spiral galaxies, but are instead patchy and discontinuous. This gives the galaxy a fluffy appearance, somewhat resembling fluffed cotton. Image Credit: ESA/Hubble & NASA, P. Erwin et al.

Galaxies that formed within the first few billion years after the Big Bang should have lived long, healthy lives. After all, they were born with rich supplies of cold hydrogen gas, exactly the fuel needed to continue star formation. But new observations have revealed “quenched” galaxies that have shut off star formation. And astronomers have no idea why.

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Are the Burned-Out Remnants of the First Stars all Around us?

An artist's illustration of the Universe's first stars, called Population 3 stars. Pop 3 stars would have been much more massive than most stars today, and would have burned hot and blue. Their lifetimes would've been much shorter than stars like our Sun. Image Credit: Public Domain, https://commons.wikimedia.org/w/index.php?curid=1582286

The first stars to appear in the universe lived fast and died young. Today, none of them likely remain. But their remnants, the black holes and neutron stars, might still wander around the cosmos. Unfortunately, they’re extremely difficult to detect unless they merge, and according to new research the only way to see them would be to conduct an unprecedented survey of the local volume of the universe.

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Astronomers Have a new way to Measure the Mass of Supermassive Black Holes

Even the most supermassive of the supermassive black holes aren’t very large, making it extremely difficult to measure their sizes. However, astronomers have recently developed a new technique that can estimate the mass of a black hole based on the movement of hot gas around them – even when the black hole itself it smaller than a single pixel.

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Astronomers Might use Pulsars to First Detect Merging Supermassive Black Holes

This artist’s impression shows the material ejected from the region around the supermassive black hole in the quasar SDSS J1106+1939. This object has the most energetic outflows ever seen, at least five times more powerful than any that have been observed to date. Quasars are extremely bright galactic centres powered by supermassive black holes. Many blast huge amounts of material out into their host galaxies, and these outflows play a key role in the evolution of galaxies. But, before this object was studied, the observed outflows weren’t as powerful as predicted by theorists. The very bright quasar appears at the centre of the picture and the outflow spreads about 1000 light-years out into the surrounding galaxy.

Astronomers have been using gravitational waves to detect merging black holes for years now, but may have to rely on pulsars – rapidly spinning neutron stars – to observe the mergers of supermassive black holes.

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The Milky Way Hasn’t Been Evenly Mixed

Artist impression: Clouds and streams of cosmic pristine gas (magenta) accrete onto the Milky Way, but this gas does not efficiently mix in the Galactic disk, as highlighted for the Solar neighborhood (zoom-in). © Dr Mark A. Garlick

Gas from the intergalactic medium constantly rains down on galaxies, fueling continued star formation. New research has shown that this gas is not evenly mixed, and stars are not equal across the galaxy. This result means that solar systems are not the same within the Milky Way.

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