How Could Laser-Driven Lightsails Remain Stable?

Project Starshot, an initiative sponsored by the Breakthrough Foundation, is intended to be humanity's first interstellar voyage. Credit: breakthroughinitiatives.org

It’s a long way to the nearest star, which means conventional rockets won’t get us there. The fuel requirements would make our ship prohibitively heavy. So an alternative is to travel light. Literally. Rather than carrying your fuel with you, simply attach your tiny starship to a large reflective sail, and shine a powerful laser at it. The impulse of photons would push the starship to a fraction of light speed. Riding a beam of light, a lightsail mission could reach Proxima Centauri in a couple of decades. But while the idea is simple, the engineering challenges are significant, because, across decades and light-years, even the smallest problem can be difficult to solve.

Continue reading “How Could Laser-Driven Lightsails Remain Stable?”

Atmospheres in the TRAPPIST-1 System Should be Long Gone

Illustration of the Trappist-1 system. Credit: NASA/JPL-Caltech

Trappist-1 is a fascinating exoplanetary system. Seven worlds orbiting a red dwarf star just 40 light-years away. All of the worlds are similar to Earth in mass and size, and 3 or 4 of them are potentially habitable. Imagine exploring a system of life-rich worlds within easy traveling distance of each other. It’s a wonderful dream, but as a new study shows it isn’t likely that life exists in the system. It’s more likely the planets are barren and stripped of their atmospheres.

Continue reading “Atmospheres in the TRAPPIST-1 System Should be Long Gone”

How Dangerous are Kilonovae?

An illustration of the kilonova GW170817. Credit: NASA/CXC/M.Weiss

When we look up at the sky on a particularly dark night, there is a sense of timelessness. We might see the flash of a meteor, and occasionally a comet is visible to the naked eye, but the cold and distant stars are unchanging. Or so it seems. There can also be a sense of calm, that despite all the uncertainty of the world, the stars will always watch over us. So it’s hard to imagine that light years away there could be a lurking event that poses an existential threat to humanity. That threat is extremely tiny, but not zero, and it is the focus of a recent paper published in The Astrophysical Journal.

Continue reading “How Dangerous are Kilonovae?”

Dark Matter Might Help Explain How Supermassive Black Holes Can Merge

A lopsided starburst galaxy known as NGC 1313. Credit: International Gemini Observatory

Although the exact nature of dark matter continues to elude astronomers, we have gained some understanding of its general physical properties. We know how it clusters around galaxies, how it makes up much of the matter in the Universe, and even how it can interact with itself. Now a new study looks at just how fast dark matter can move.

Continue reading “Dark Matter Might Help Explain How Supermassive Black Holes Can Merge”

Even Early Galaxies Grew Hand-in-Hand With Their Supermassive Black Holes

An artist’s impression of a quasar. Credit: NASA / ESA / J. Olmsted, STScI

Within almost every galaxy there is a supermassive black hole. This by itself implies some kind of formative connection between the two. We have also observed how gas and dust within a galaxy can drive the growth of galactic black holes, and how the dynamics of black holes can both drive star formation or hinder it depending on how active a black hole is. But one area where astronomers still have little information is how galaxies and their black holes interacted in the early Universe. Did black holes drive the formation of galaxies, or did early galaxies fuel the growth of black holes? A recent study suggests the two evolved hand in hand.

Continue reading “Even Early Galaxies Grew Hand-in-Hand With Their Supermassive Black Holes”

It's a Fine Line Between a Black Hole Energy Factory and a Black Hole Bomb

Ray traced shadow of a spinning and charged black hole. Credit: Simon Tyran, CC BY-SA 4.0

Black holes are powerful gravitational engines. So you might imagine that there must be a way to extract energy from them given the chance, and you’d be right. Certainly, we could tap into all the heat and kinetic energy of a black hole’s accretion disk and jets, but even if all you had was a black hole in empty space, you could still extract energy from a trick known as the Penrose process.

Continue reading “It's a Fine Line Between a Black Hole Energy Factory and a Black Hole Bomb”

New Types of Hidden Stars Seen for the First Time

Artist’s impression of a cloud of smoke and dust being thrown out by a red giant star. Credit: Philip Lucas/University of Hertfordshire

In the early days of telescopic astronomy, you could only focus on one small region of the sky at a time. Careful observations had to be done by hand, and so much of the breakthrough work centered around a particular object in the sky. A nebula or galaxy, quasar or pulsar. But over the years we’ve been able to build telescopes capable of capturing a wide patch of sky all at once, and with automation, we can now map the entire sky. Early sky surveys took years to complete, but many modern sky surveys can look for changes on the order of weeks or days. This ability to watch for changes across the sky is changing the way we do astronomy, and it is beginning to yield some interesting results. As a case in point, an infrared sky survey is revealing hidden stars we hadn’t noticed before.

Continue reading “New Types of Hidden Stars Seen for the First Time”

Nancy Grace Roman Could Find the First Stars in the Universe

Simulation of a star ripped apart in a tidal disruption event. Credit: NASA’s Goddard Space Flight Center/Chris Smith (USRA/GESTAR)

In the beginning, the Universe was so hot and so dense that light could not travel far. Photons were emitted, scattered, and absorbed as quickly as the photons in the heart of the brightest stars. But in time the cosmos expanded and cooled to the point that it became transparent, and the birthglow of the Big Bang could traverse space and time for billions of years. We still see it as the microwave cosmic background. As the Universe expanded it grew dark, filled only with warm clouds of hydrogen and helium. In time those clouds collapsed to form the first stars, and light again filled the heavens.

Continue reading “Nancy Grace Roman Could Find the First Stars in the Universe”

Webb Sees Dozens Of Young Quasars in the First Billion Years of the Universe

Artist's impression of blue quasar in the early universe. Credit: S. Munro / CC BY 4.0

Within almost every galaxy is a supermassive black hole. Millions, sometimes billions of solar masses locked within an event horizon of space and time. They can power luminous quasars, drive star formation, and change the evolution of a galaxy. Because of their size and abundance, supermassive black holes must have formed early in cosmic history. But how early is still an unanswered question. It’s a focus of a recent study on the arXiv.

Continue reading “Webb Sees Dozens Of Young Quasars in the First Billion Years of the Universe”

What Could the Extremely Large Telescope See at Proxima Centauri's Planet?

Artist’s impression of the surface of the planet Proxima b orbiting the red dwarf star Proxima Centauri. The double star Alpha Centauri AB is visible to the upper right of Proxima itself. Credit: ESO

Proxima Centauri B is the closest exoplanet to Earth. It is an Earth-mass world right in the habitable zone of a red dwarf star just 4 light-years from Earth. It receives about 65% of the energy Earth gets from the Sun, and depending on its evolutionary history could have oceans of water and an atmosphere rich with oxygen. Our closest neighbor could harbor life, or it could be a dry rock, but is an excellent target in the search for alien life. There’s just one catch. Our usual methods for detecting biosignatures won’t work with Proxima Centauri B.

Continue reading “What Could the Extremely Large Telescope See at Proxima Centauri's Planet?”