Dying star suffers ‘irregular heartbeats’

Some dying stars suffer from ‘irregular heartbeats’, research led by astronomers at the University of Warwick has discovered.

Captured at Last: The Tiny Stars that Spark Fierce Supernovae Explosions

A longstanding mystery about the tiny stars that let loose powerful explosions known as Type Ia supernovae might finally be solved. For brief periods, these cataclysmic blasts can outshine an entire galaxy of billions of stars. Astrophysicists want to understand their origins because they are integral to the evolution of galaxies and the study of dark energy.

Type 1a Supernova A visualization of a computer simulation of a Type Ia supernova. Ejected material (brown) from an exploding white dwarf star crashes into its companion star (blue), yielding an ultraviolet pulse of light streaming from the companion star’s location

Can Planets Be Rejuvenated Around Dead Stars?

For a planet, this would be like a day at the spa. After years of growing old, a massive planet could, in theory, brighten up with a radiant, youthful glow. Rejuvenated planets, as they are nicknamed, are only hypothetical. But new research from NASA’s Spitzer Space Telescope has identified one such candidate, seemingly looking billions of years younger than its actual age.

This artist’s concept shows a hypothetical “rejuvenated” planet – a gas giant that has reclaimed its youthful infrared glow. NASA’s Spitzer Space Telescope found tentative evidence for one such planet around a dead star, or white dwarf, called PG 0010+280 (depicted as white dot in illustration). Source: NASA

White Dwarf Migration in Globular Cluster 47 Tucanae

This diagram shows how white dwarfs, the burned-out relics of stars, are distributed in the ancient globular star cluster 47 Tucanae. The youngest white dwarfs are the hottest and bluest stars dwelling mostly in the cluster’s core, where the most massive stars reside. Shortly before collapsing to become white dwarfs, the stars shed most of their mass. Now, as lightweight white dwarfs, they interact gravitationally with more massive stars in the core. Through these gravitational encounters, the white dwarfs rob enough speed from their more massive cousins to begin migrating slowly outward from their home. During their journey, they become older and cooler white dwarfs, depicted in the orange dots. Eventually, the white dwarfs settle on the outskirts of the cluster, where the oldest, coolest, reddest white dwarfs reside.

X-ray image of NGC 6388

Using Chandra and several other telescopes, researchers have found evidence that a white dwarf star - the dense core of a star like the Sun that has run out of nuclear fuel - may have ripped apart a planet as it came too close. Chandra shows that the X-rays are not coming from the cluster’s center, as is evident when combined with visible light data from the Hubble Space Telescope. Instead, the details of the combined datasets point to a possible “tidal disruption” where one astronomical object destroys another through powerful gravitational forces. 

X-ray: NASA/CXC/IASF Palermo/M.Del Santo et al; Optical: NASA/STScI

Brake system for stars

According to the classical understanding of newly-born neutron stars they should rotate more than 1000 times per second. Observations tell, however, that they rotate "only" 10 to 100 times per second and that their specific angular momentum is with 10¹⁴ cm²/s only 1% of the predicted values for angular momentum conservation. Neutron stars share this strong discrepancy with white dwarfs for which new spectroscopic observations give a maximum surface rotation rate of 10 km/s. This also leads to low values of the specific angular momentum, much less than expected. How is it possible?

Type Ia supernovae, two (sources) of a kind

The exploding stars known as Type Ia supernovae serve an important role in measuring the universe, and were used to discover the existence of dark energy. They're bright enough to see across large distances, and similar enough to act as a "standard candle" - an object of known luminosity. The 2011 Nobel Prize in Physics was awarded for the discovery of the accelerating universe using Type Ia supernovae. However, an embarrassing fact is that astronomers still don't know what star systems make Type Ia supernovae.

The Tycho supernova remnant is the result of a Type Ia supernova explosion. The explosion was observed by Danish astronomer Tycho Brahe in 1572. More than 400 years later, the ejecta from that explosion has expanded to fill a bubble 55 light-years across. In this image, low-energy X-rays (red) show expanding debris from the supernova explosion and high energy X-rays (blue) show the blast wave - a shell of extremely energetic electrons. Credit: X-ray: NASA/CXC/Rutgers/K.Eriksen et al.; Optical: DSS

Studying Type Ia supernova progenitors

Type Ia supernovae are important stellar phenomena, used to measure the expansion of the universe. But astronomers know embarrassingly little about the stars they come from and how the explosions happen. New research from a team led by Harvard University and including Carnegie’s Josh Simon, Chris Burns, Nidia Morrell, and Mark Phillips examined 23 Type Ia supernovae and helped identify the formation process for at least some of them. Their work will be published in The Astrophysical Journal and is available online.

Possible progenitors of type Ia supernovae. Credit: A, ESO; B, STSCI, NASA; C, NASA/T. Strohmayer (Gsfc)/D. Berry (Chandra X-Ray Observ.)

A history of shattered exoplanets and hungry white dwarfs

University of Warwick astrophysicists have pinpointed four white dwarfs surrounded by dust from shattered planetary bodies which once bore striking similarities to the composition of the Earth.

The inner region of an exo-planetary system where four terrestrial planets orbit a solar-like star. Credit: Mark A. Garlick / space-art.co.uk / University of Warwick