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

Pascal the cat knows about particle physics.

Pascal the cat knows about particle physics.

It’s fundamental and natural to ask this question about an object: “how big is it?” For many things—most everyday objects, people, planets, stars—size is easy to measure. However, other things are more challenging, including the size of a proton: one of the three particles that make up every ordinary bit of matter. The major challenge is its tiny size, which precludes using light of any kind to measure it. To make matters worse, the size of a proton may depend strongly on what method you use to measure it, as I explained for Double X Science.

The simplest way to measure the size of a proton involves shooting electrons at it, and measuring the paths the electrons take as they feel the influence of the various forces. Because of those forces, in fact, the proton can’t be said to have a single size! Instead, physicists use three different size measurements, which are all pretty close to each other, but not exactly the same. The one most important to us for this post is the charge radius. Electron bombardment measurements found that to be about 0.88 femtometers.

However, electron bombardment only gets us so far; if we want better accuracy, we need another method. [Read more…]

How big is a proton?

Where do cosmic rays originate? Cosmic rays are mostly high-energy protons from deep space that hit Earth’s upper atmosphere, creating showers of other particles that can be detected at the surface. Some of these protons are so incredibly high energy—meaning they’re moving just a whisker slower than the speed of light—that only exceptional astronomical events could accelerate them. The prime suspect: supernova explosions. Up until now, though, nobody had confirmed this suspicion. However, a new observation using gamma ray emissions from supernova remnants found the telltale signature of particle collisions, which could only be present if protons were getting that extra boost of energy.

On October 15, 1991, a high-energy proton from deep space struck Earth’s upper atmosphere. Known as the “Oh My God Particle”, this proton was by far the highest energy cosmic ray ever seen. This one proton’s energy was equivalent to a regulation soccer ball traveling at 15 meters per second (34 miles per hour). In the two decades following, observers spotted several similarly energetic cosmic rays, which left a big question: what was accelerating these protons to higher speeds than anything we can achieve in on Earth? [Read more….]

High-energy cosmic rays are sped on their way by exploding stars

Vesta is the second-largest asteroid in the Solar System, and recent measurements by the Dawn mission showed that it’s actually a protoplanet: a piece of planet-like material left over from the early days of our Solar System. However, Dawn is significantly non-spherical and very battered. Most notably, it has two huge overlapping craters near its south pole, marking impacts that nearly shattered the asteroid, and which raised a mountain higher than any other in the Solar System. Now, a computer simulation may have showed how Vesta came to be the fascinating, scarred, wonderful object we see today.

As with other Solar System bodies, Vesta bears the scars of its history. The most substantial of these scars are the two large impact basins, Veneneia and Rheasilvia. (Both craters were named for virgins who served the goddess Vesta in Roman mythology—the vestals.) Rheasilvia formed about 1 billion years ago and is larger. Veneneia is smaller and formed at least 2 billion years ago; its presence was partly obscured by the later impact. Meteorites from Vesta, possibly ejected by the impacts forming Rheasilvia and Veneneia, have been found on Earth. [Read more….]

Kaboom! A simulation shows how impacts shaped and nearly destroyed Vesta