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Are Super-Earths Really Mini-Neptunes?

February 7, 2013 Leave a comment

In the last two decades astronomers have found hundreds of planets in orbit around other stars. One type of these so-called ‘exoplanets’ is the super-Earths that are thought to have a high proportion of rock but at the same time are significantly bigger than our own world. Now a new study led by Helmut Lammer of the Space Research Institute (IWF) of the Austrian Academy of Sciences suggests that these planets are actually surrounded by extended hydrogen-rich envelopes and that they are unlikely to ever become Earth-like. Rather than being super-Earths, these worlds are more like mini-Neptunes. The scientists publish their work in the journal Monthly Notices of the Royal Astronomical Society.

‘Super-Earths’ follow a different evolutionary track to the planets found in our Solar system but an open question is whether they can evolve to become rocky bodies like the ‘terrestrial planets’ Mercury, Venus, Earth and Mars. To try to answer this, Dr Lammer and his team looked at the impact of radiation on the upper atmospheres of super-Earths orbiting the stars Kepler-11, Gliese 1214 and 55 Cancri.

Full Story: http://www.ras.org.uk/news-and-press/224-news-2013/2217-are-super-earths-really-mini-neptunes

The Wings of the Seagull Nebula

February 7, 2013 Leave a comment

Credit:ESO

Credit:ESO

This new image from ESO shows a section of a cloud of dust and glowing gas called the Seagull Nebula. These wispy red clouds form part of the “wings” of the celestial bird and this picture reveals an intriguing mix of dark and glowing red clouds, weaving between bright stars. This new view was captured by the Wide Field Imager on the MPG/ESO 2.2-metre telescope at ESO’s La Silla Observatory in Chile.

Running along the border between the constellations of Canis Major (The Great Dog) and Monoceros (The Unicorn) in the southern sky, the Seagull Nebula is a huge cloud mostly made of hydrogen gas. It’s an example of what astronomers refer to as an HII region. Hot new stars form within these clouds and their intense ultraviolet radiation causes the surrounding gas to glow brightly.

Full Story: http://www.eso.org/public/news/eso1306/

Forecasting A Supernova Explosion

February 7, 2013 Leave a comment

Supernova picture taken by NASA's Spitzer Space Telescope provided courtesy of NASA

Supernova picture taken by NASA’s Spitzer Space Telescope provided courtesy of NASA

Type II supernovae are formed when massive stars collapse, initiating giant explosions. It is thought that stars emit a burst of mass as a precursor to the supernova explosion. If this process were better understood, it could be used to predict and study supernova events in their earliest stages. New observations from a team of astronomers including Carnegie’s Mansi Kasliwal show a remarkable mass-loss event about a month before the explosion of a type IIn supernova. Their work is published on February 7 in Nature.

Several models for the supernova-creation process predict pre-explosion outbursts, but it has been difficult for scientists to directly observe this process. Observations of emission lines radiating out form type IIn supernovae are thought to represent interactions between the mass ejected during and prior to the star’s explosion.

Full Story: http://carnegiescience.edu/news/forecasting_supernova_explosion

Where Are All The Dwarfs?

February 7, 2013 Leave a comment

Cosmic Web Stripping, Visualization Credits: Alejandro Benitez Llambay

Cosmic Web Stripping, Visualization Credits: Alejandro Benitez Llambay

Galaxies and matter in the universe clump in an intricate network of filaments and voids, known as the Cosmic Web. Computer experiments on massive supercomputers have shown that in such a Universe a huge number of small “dwarf” galaxies weighing just one thousandth of the Milky Way should have formed in our cosmic neighbourhood. Yet only a handful of these galaxies are observed orbiting around the Milky Way. The observed scarcity of dwarf galaxies is a major challenge to our understanding of galaxy formation.

An international team of researchers has studied this issue within the Constrained Local UniversE Simulations project (CLUES). The CLUES simulations use the observed positions and peculiar velocities of galaxies within Tens of Millions of light years of the Milky Way to accurately simulate the local environment of the Milky Way. “The main goal of this project is to simulate the evolution of the Local Group – the Andromeda and Milky Way galaxies and their low-mass neighbours – within their observed large scale environment”, said Stefan Gottlöber of the Leibniz Institute for Astrophysics Potsdam.

Analysing the CLUES simulations, the astronomers have now found that some of the far-out dwarf galaxies in the Local Group move with such high velocities with respect to the Cosmic Web that most of their gas can be stripped and effectively removed.

Full Story: http://www.aip.de/en/news/press/dwarfs

NASA’s Cassini Watches Storm Choke On Its Own Tail

February 7, 2013 Leave a comment

Image credit: NASA/JPL-Caltech/SSI/Hampton University

Image credit: NASA/JPL-Caltech/SSI/Hampton University

Call it a Saturnian version of the Ouroboros, the mythical serpent that bites its own tail. In a new paper that provides the most detail yet about the life and death of a monstrous thunder-and-lightning storm on Saturn, scientists from NASA’s Cassini mission describe how the massive storm churned around the planet until it encountered its own tail and sputtered out. It is the first time scientists have observed a storm consume itself in this way anywhere in the solar system.

“This Saturn storm behaved like a terrestrial hurricane – but with a twist unique to Saturn,” said Andrew Ingersoll, a Cassini imaging team member based at the California Institute of Technology, Pasadena, who is a co-author on the new paper in the journal Icarus. “Even the giant storms at Jupiter don’t consume themselves like this, which goes to show that nature can play many awe-inspiring variations on a theme and surprise us again and again.”

Full Story: http://www.jpl.nasa.gov/news/news.php?release=2013-040#2