When our Sun runs out of nuclear fuel, it will shed its outer layers, while what’s left of the core will remain as a white dwarf: an object the size of Earth, but far more massive. During the final stages of the Sun’s life, Earth is likely to perish as a habitable world, but that’s not necessarily the case for every planet orbiting a Sunlike star. That’s the basis of a new paper, which posited that white dwarfs may even provide the best hope for detecting extraterrestrial life.

The advantages of these systems would be manifold: a white dwarf is much smaller than a star, so if a planet passes between it and us, far more light is blocked. And Avi Loeb and Dan Maoz proposed that at least some signs of life might have survived the deaths of these stars. The light emitted by the white dwarf could highlight any oxygen in the exoplanet’s atmosphere, which would be seen as a strong hint of life. [Read more…]

Living planets in a stellar graveyard

The region near a black hole is one of the most extreme environments in the Universe, but historically it’s been hard to study directly. Using the XMM-Newton and NuSTAR telescopes, astronomers have measured the rotation of gas near the supermassive black hole at the center of the Great Barred Spiral Galaxy. They found that this black hole is spinning nearly as fast as it can be, and that the matter orbiting the black hole is similarly moving near the speed of light—to the extent that the results of Einstein’s general relativity must be used to understand how it’s moving. The key measurement involved observing X-rays reflected off the matter whirling around the black hole, a significant observation of a relativistic phenomenon.

A new X-ray observation of the region surrounding the supermassive black hole in the Great Barred Spiral Galaxy may have answered one of the big questions. G. Risaliti and colleagues found the distinct signature of X-rays reflecting off gas orbiting the black hole at nearly the speed of light. The detailed information the astronomers gleaned allowed them to rule out some explanations for the bright X-ray emission, bringing us closer to an understanding of the extreme environment near these gravitational engines. [Read more…]

Measuring the spin of a black hole using X-rays

Forgive me if I get excited for a moment, but…today marks my first contribution to BBC Future! The feature I contributed is part of the “Will we ever?” series, in which science writers ask some big questions about what research may or may not be able to answer in the future. My article pondered whether we’ll ever be able to identify dark matter: the mysterious substance that comprises more than 80% of the mass of the Universe. (The link for my UK readers is here.)

Right now, a far easier question to answer is what dark matter isn’t. First of all, the name is misleading: dark matter isn’t “dark” in any usual sense of the word. “Invisible matter” is a better term: light shining on dark matter from any source passes right through without being absorbed or scattered, regardless of the type of light. This means dark matter can’t be made of atoms or of their constituent parts; that is, electrons, protons and neutrons.

In fact, dark matter doesn’t correspond to anything in the Standard Model, the best explanation we have for how the universe works. [Read more…]

Will we ever know the identity of dark matter?

Electron beams, like light, spread out when they pass through an opening. Even highly focused beams such as lasers spread over large distances, a result of the wave character of light. However, by manipulating the wave form near its source, researchers can create something known as an Airy beam, which doesn’t disperse—and in fact follows a curved path. A new experiment has created Airy beams using electrons, a significant step toward highly controllable electron beams. As a bonus, these beams can even “self-heal” after passing by a barrier.

Electrons also experience diffraction and interference, which is the source of the famous quantum double-slit experiment. In the new experiment, the researchers manipulated the wave function of an electron beam by sending it through a specific holographic pattern. They focused the beam using a magnetic field that acted much like a lens, producing a distinctive triangular bundle of electron beams. Each bundle followed a curved path, which the researchers determined by measuring the electron patterns at various distances from the hologram. [Read more…]

Electron, heal thyself! Making curved electron beams go around barriers

We often focus on the search for Earth-like planets (whatever that means) when we talk about exoplanets: planets orbiting other stars. However, another important goal is to categorize as many planetary systems as possible, determining what kind of planets orbit what sort of stars. That catalog is gradually revealing the way planets form, and how the detailed history of each system leads to what we observe today. For example, Mercury is the smallest planet in the Solar System, but it’s far from being the smallest spherical body—and nobody expects it to be the smallest planet of any star system. Now a new observation has found an exoplanet noticeably smaller than Mercury, which will help us fill in the catalog a little more.

Now researchers may have found the smallest exoplanet yet, a world with a diameter about 80 percent of Mercury’s. This planet candidate, named Kepler-37b, orbits very close to its star: its orbital radius is about 1/4 the size of Mercury’s, so it takes only about 13 days to zip around. Thomas Barclay and collaborators also identified two other planets in the same system—labeled Kepler-37c and Kepler-37d—one of which is slightly larger than Mars, and the other which has twice Earth’s diameter. [Read more…]

New exoplanet is smaller and hotter than Mercury

Double X Science chemistry editor Adrienne Roehrich started a new podcast series, discussing stories of the week. Her first cohost was…me! We talked about important women in biochemistry, the size of protons, the science of procrastination, and cosmic rays—all in 15 minutes.

You can download the podcast from the Double X site, or subscribe through Feedburner. Adrienne is also working on listing our content on iTunes; I’ll update when that happens. Update: the podcast is now available on iTunes!

Procrastination and protons

Any core-collapse supernova—the explosion of a massive star—is by nature powerful, destructive, and rare. The really dramatic supernovas have the extra effect of exploding in a non-spherical way, beaming a lot of their matter and energy along an axis. When Earth is aligned with those beams, we see the supernova as a gamma ray burst (GRB), the brightest of which can be seen from billions of light-years away. (As the name suggests, these events are exceptionally bright in gamma ray light. In fact, they were first discovered by spy satellites monitoring for illicit nuclear tests—which are also marked by heavy gamma ray emission.) Observations of a supernova remnant in our galaxy strongly hint both that it was a GRB, and that it harbors a black hole at its center. That would mean the supernova is the only known GRB in our galaxy, and its black hole is the youngest known—a wonderful double discovery.

While stars like our Sun go gently into that good night, stars more than 25 times more massive explode in violent supernovae. Since stars that big are rare, their explosions are too, so astronomers typically have to do forensic work on supernova remnants in our galaxy. One particular remnant is one the brightest X- and gamma-ray sources around, marking it as a relatively recent explosion. By studying the remnant, astronomers have determined it likely harbors the youngest black hole in the Milky Way, and the original explosion may have been extremely energetic. [Read more…]

Weird supernova marks the spot of a violent outburst…and black hole