A mystery: an unknown star, too faint to notice, suddenly expanded to a huge size, increasing in brightness to become one of the most luminous stars known. This star doesn’t even have a real name, just a “license plate” catalog number: V838 Monocerotis, indicating that it’s a not very important star in the constellation the Unicorn (Monoceros). However, a new paper has proposed the powerful flare could be explained by a well-accepted theory of binary star behavior, in which one star strips enough matter off the other until it suddenly grows to a huge size. These common envelope events (as they are known) could explain the V838 Monocerotis outburst, along with some other currently mysterious flares.
A new Science paper proposes that a class of violent astronomical events that we’ve observed may be due to common envelope stars, providing more direct evidence for their existence. These cataclysms are known as “red transient outbursts,” and in brightness terms, they’re somewhere between novas (flares of nuclear activity at the surfaces of white dwarfs) and supernovas, the violent deaths of stars. N. Ivanova, S. Justham, J. L. Avendado Nandez, and J. C. Lombardi Jr. identified a possible physical model for these outbursts, based on the recombination of electrons and ions in the plasma when the stars’ envelopes merge. [Read more…]
Every exoplanet discovery seems to bring us closer to understanding the variety of planetary systems out there in our galaxy. The latest find is particularly exciting: an Earth-mass planet orbiting around Alpha Centauri B, one of three stars in the closest system to the Solar System. The planet isn’t very Earthlike in most respects, but it’s still an incredibly exciting discovery.
However, the discovery is still exciting for a number of reasons. First is the proximity of the star system to us: Alpha Centauri is 4.4 light years away, a tiny distance in cosmic terms. The stars Alpha Centauri A and B are some of the brightest in the sky in the Southern Hemisphere. (Sorry, fellow Northern Hemisphere-dwellers; we can’t see them from here.) We don’t have starship technology to travel there, but we could conceivably send a robotic probe that could arrive within my lifetime, and 4.4 years isn’t a terribly long time for data to travel back to Earth. No one has such a probe in the works yet, but the mere fact of discovery of a planet might encourage investment in that direction. [Read more…]
The ALMA telescopes found a spiral pattern surrounding the dying star R Sculpturis.
Though it may seem sad on the surface, the death of a star is a beautiful thing—and an important precursor to the birth of new stars and planets. The Atacama Large Millimeter Array (ALMA) in Chile has provided a breathtaking view of a star nearing the end of its life. One unexpected feature was a lovely spiral pattern that probably indicates the presence of a hidden companion.
While earlier observations showed a thin spherical shell of gas perfectly centered on R Sculptoris, the ALMA data revealed unexpected structure inside. The details included clumps in the gas shell and a winding spiral pattern, as seen in the image above. Additionally, the amount of mass contained in the surrounding matter is approximately three times what was estimated from earlier observations and models of similar stars. [Read more….]
(This headline was my original choice for the article, which was understandably rejected by my editors. So, you get to read it here instead.)
Pulsars are rapidly-spinning neutron stars, the very small dense remnants of stars at least 8 times more massive than the Sun. Their pulses are intense beams of light that sweep across our field of view each time the neutron star rotates. A pulsar’s rotation slows down over time, though, and some researchers in the UK have proposed a simple physical model that refines the most widely accepted theory.
Observations of the matter expelled by the initial supernova can be used to estimate the age of the pulsar; those numbers can be compared to age estimates based on its spin slowdown. In some cases, these estimates match reasonably well, but in others, they give wildly different results, differing by thousands of years at the extreme. The researchers’ model began with a different assumption: that the superfluid comprised a higher fraction of the core before things start to cool down. The result is pinning: the vortices in the superfluid stick to one spot relative to each other. That means the superfluid’s rotation rate remains the same, while the rest of the pulsar continues to slow down. [Read more….]
The long jet of gas in the galaxy M87, which is driven by the supermassive black hole at the galaxy’s center. New observations have revealed the structure of the gas disk near the black hole.
A collection of four big telescopes in Arizona, California, and Hawaii have banded together to examine one of the biggest black holes we know: the beast at the heart of the galaxy M87. What they found: the disk of gas driving M87’s huge jet rotates the same direction as the black hole that made it.
New observations from the Event Horizon Telescope (actually an array of four millimeter-wave telescopes working in concert) have revealed the best view so far of the supermassive black hole in the galaxy M87. As described in a Science paper, astronomers measured the motion of gas to a distance approximately 5.5 times the event horizon radius. That is close enough to confirm the gas circles in the same direction the black hole itself rotates. These observations help clarify the origin of the powerful jet of gas streaming from the galaxy’s center at a high fraction of the speed of light: it is likely driven by the swirling matter near the black hole’s boundary. [Read more….]