What Type of Star is Our Sun?

High-spatial and temporal resolution view from the Hinode SOT G-band filter (NASA)

High-spatial and temporal resolution view from the Hinode SOT G-band filter (NASA)

Our Sun is often called an “average” or “unremarkable” star. This is a little unfair, after all this unremarkable specimen is responsible for generating all the energy for all the planets in the Solar System and it has nurtured life on Earth for the past four billion years. We are also very lucky in that the Sun (or “Sol”) is comparatively stable with a periodic cycle. What’s more, it is alone, with no binary partner complicating matters. We live in a very privileged corner of the Milky Way, within the “Goldilocks Zone” (i.e. “just right” for life – as we know it – to thrive) from Sol, where there is a unique and delicate relationship between our star, the Earth and interplanetary space. This is all great, but in the star club, how does Sol measure up? Is it really just an average, boring star?
Continue reading

About these ads

Recoiling Supermassive Black Holes and Stellar Flares

Simulation of black holes colliding. In a word, awesome (Max Planck Group)

Astrophysicists love to simulate huge collisions, and they don’t get much bigger than this. From the discoverers of the first ever observed black hole collision back in April, new observational characteristics have been researched and Max Planck astrophysicists believe that after two supermassive black holes (SMBHs) have collided, they recoil and drag flaring stars with them. By looking out for anomalous X-ray flares in intergalactic space, or off-galactic nuclei locations, repelled black holes may be spotted powering their way into deep space at velocities of up to 4000 kms-1
Continue reading

Observing Red Dwarf Stars May Reveal Habitable “Super-Earths” Sooner

A planet orbiting a red dwarf (NASA)

OK, so if you’re an exoplanet hunter, which stars would you focus your attention on? Would you look at bright blue young stars? Or would you look at dim, long-lived red stars? If you think about it, trying to see a small exoplanet eclipse (or transit) a very bright star would be very hard, the luminosity would overwhelm any attempt at seeing a tiny planet pass in front of the star. On the other hand, observing a planet transiting a dimmer stellar object, like a red dwarf star, any transit of even the smallest planet will create a substantial decrease in luminosity. What’s more, ground-based observatories can do the work rather than depending on expensive space-based telescopes…
Continue reading

Wolf-Rayet Star: My Favourite Stellar Object

Artist impression of a Wolf-Rayet star (NASA)

Wolf-Rayet (WR) stars are my favourite stellar objects bar none. Due to the excitement factor I find them even more interesting than black holes, pulsars and quasars. Why? Well, they are a significant period of a massive star’s lifetime making its violent, self-destructive death, possibly culminating in a supernova or gamma ray burst (GRB). WR stars blast out dense stellar winds creating a bubble of matter that completely obscures the star’s surface from any attempts at observation. They are also very noisy neighbours, disrupting binary partners and messing up huge volumes of space. If you thought a star might die quietly, the WR phase ensures this isn’t the case and astronomers are paying attention, making some of the most detailed observations of WR stars yet…
Continue reading

The Crab Pulsar is Probed By LIGO. Is it Really a Smooth Neutron Star?

The Crab Nebula contains the famous Crab Pulsar (NASA/JPL-Caltech/R. Gehrz)

Scientists working with the Laser Interferometer Gravitational-Wave Observatory (LIGO) have announced their first land-mark discovery. LIGO was built to detect gravitational waves (as predicted by Einstein’s general relativity), but this discovery is actually about not detecting gravitational waves. Hold on, what’s all the fuss about then? This sounds like a null result, and in some ways it is. But on the other hand it may be one of the most important neutron star observations ever. So what has LIGO (not) seen?
Continue reading

Collapsing Wolf-Rayet Stars and Inverse Compton Scattering of Stellar Photons

A Wolf-Rayet star WR124 with surrounding nebula M1-67 (NASA)

Wolf-Rayet stars are a violent and self-destructive phase of a massive star’s lifetime. This is the point at which they begin to die as a prelude to a supernova and black hole formation. Often, large nebulae can be found around these bright stellar objects (pictured), emitting strong ultraviolet radiation. As Wolf-Rayet (WR) stars continue to lose huge amounts of mass and deplete all their fuel, they become even more unstable, resulting in a huge supernova. Exploding WR stars have been linked with powerful gamma ray (γ-ray) bursts; in fact the largest, most distant GRB was observed on March 19th in the constellation of Boötes by NASA’s Swift Observatory and the Polish “Pie of the Sky” GRB detector. There is some evidence that this GRB was the result of a WR star/neutron star binary pair, but what would happen if a WR star is sitting close to an O-type star just as it explodes?

As the WR star collapses, a shock wave (containing hot, relativistic electrons) sent hurtling toward the O-type star may cause inverse Compton scattering of the stellar photon field, generating powerful, long period emissions of γ-ray radiation. New research suggests that this mechanism may explain the 1-100 GeV γ-rays observed minutes or hours after the main GRB…
Continue reading

How Big is the Biggest Star in the Universe?

A comparison between the Sun and a hypermassive star. Credit: NASA

So how big is it? According to Fraser at the Universe Today, the largest known star is VY Canis Majoris. This is a massive star, otherwise known as a red hypergiant star and this one sits in the constellation Canis Major, about 5000 light years from Earth. Apparently it is more than 2100 times the size of our Sun, a monster! This star is so big that light takes more than eight hours to cross its circumference. In fact, this star, if placed in the centre of the Solar System, it would reach as far as the orbit of Saturn.

Although VY Canis Majoris is big, it isn’t as big as the biggest star could be. If it was cooler, a similar star could reach over 2600 times the size of our Sun…