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Saturday, July 28, 2012

A Jupiter-mass exoplanet detected by microlensing

This is an artist's concept of a gas giant planet orbiting a red dwarf K star (system name OGLE-2003-BLG-235L/MOA-2003-BLG-53L). The planet has not been directly imaged, but its presence was detected in 2003 microlensing observations of a field star in our galaxy. Gravitational microlensing happens when a foreground star amplifies the light of a background star that momentarily aligns with it. Follow-up observations by Hubble Space Telescope in 2005 separated the light of the slightly offset foreground star from the background star. This allowed the host star to be identified as a red dwarf star located 19,000 light-years away. The Hubble observations allow for the planet's mass to be estimated at 2.6 Jupiter masses. The characteristics of the lensing event show that the planet is in a Jupiter-sized orbit around its parent red star. The rings and moon around the gas giant are hypothetical, but plausible, given the nature of the family of gas giant planets in our solar system.
Credit: NASA, ESA, and G. Bacon (STScI)

Friday, July 27, 2012

Vampires and victims in O-type binary systems

A new study using ESO’s Very Large Telescope (VLT) has shown that most very bright high-mass stars, which drive the evolution of galaxies, do not live alone. Almost three quarters of these stars are found to have a close companion star, far more than previously thought. Surprisingly most of these pairs are also experiencing disruptive interactions, such as mass transfer from one star to the other, and about one third are even expected to ultimately merge to form a single star. The results are published in the 27 July 2012 issue of the journal Science.

This artist's impression shows how hot, brilliant and high-mass stars evolve. New work using ESO telescopes has shown that most such stars are in pairs. These stars are up to one million times brighter than the Sun, and evolve about one thousand times more quickly. As the stars evolve they expand slowly. The more massive brighter star expands first, until the outer layers start to strongly feel the gravitational pull of the companion, deforming the star into a teardrop shape. The companion then starts to suck material from the primary star. When the primary has been stripped from its entire hydrogen rich envelope it shrinks. At this point the secondary star is now rotating very fast and has an oblate shape. The hot compact star continues to fuse heavier and heavier elements in its centre until it explodes as a supernova. During the explosion a neutron star is born which probably escapes. The secondary is left behind alone. It swells up and becomes a red supergiant with a radius a few times larger than the orbit of the Earth around the Sun. Eventually the second star also explodes as a supernova. Note: this video is based on simulations but is not intended to be quantitatively accurate in detail.
Credit: ESO/L. Cal├žada/M. Kornmesser/S.E. de Mink

Thursday, July 26, 2012

A pure gamma-ray pulsar that rotates 38 millionths of a Hertz faster than before

Max Planck scientists discover a young and energetic neutron star with unusually irregular rotation

A gamma-ray pulsar is a compact neutron star that accelerates charged particles to relativistic speeds in its extremely strong magnetic field. This process produces gamma radiation (violet) far above the surface of the compact remains of the star, while radio waves (green) are emitted over the magnetic poles in the form of a cone. The rotation sweeps the emission regions across the terrestrial line of sight, making the pulsar light up periodically in the sky.
Credit: NASA/Fermi/Cruz de Wilde

Monday, July 23, 2012

Rivers of methane produced surprisingly little erosion on Titan

For many years, Titan's thick, methane- and nitrogen-rich atmosphere kept astronomers from seeing what lies beneath. Saturn's largest moon appeared through telescopes as a hazy orange orb, in contrast to other heavily cratered moons in the solar system.

Sunday, July 22, 2012

The Whirlpool Galaxy done slicing

The Whirlpool Galaxy (or M51 or NGC 5194) in all its glory, with the companion galaxy NGC 5195 (top right).
Credit: NASA, ESA, S. Beckwith (STScI), and The Hubble Heritage Team STScI/AURA)

A snow line, a dead zone and a nearly dry planet

In the standard disk model, shown above, Earth formed beyond the snow line, in an icy region of the protoplanetary disk that encircled the newborn Sun 4.6 billion years ago. Our planet should, therefore, contain lots of water because it formed from ices that would have been a major fraction of its composition. However, it's estimated that less than 1 percent of Earth's mass is locked up in water, which has puzzled scientists.
Credit: NASA, ESA, and A. Feild (STScI)

Saturday, July 21, 2012

BX442, a spiral galaxy from the depths of time

Artist's rendering of galaxy BX442 and companion.
Credit: Dunlap Institute for Astronomy & Astrophysics; Joe Bergeron