Sunday, 26 August 2012

Astrophysics stuff from the week 20-26/8/12

A surprisingly good picture of one of Mars' two moons - Phobos - if you have 3D glasses, that is.

'First evidence discovered of planet's destruction by its star'
Evidence has been seen of a planet destroyed by its host star, as it inflated during its red dwarf stage -- this is expected to happen to our own star, with the Sun ingesting Mercury, Venus, and possibly Earth. Regardless of whether Earth is absorbed, everything on it will be roasted!
The star itself - 'BD+48 740' - is older than the Sun, and 11 times bigger by radius - it also has a planet of 1.6 Jupiter masses orbiting it, in a highly elliptical orbit.
The astronomers were notified of the other planet's absorption, by spectroscopic analysis of the star, which revealed a high lithium signature.
Lithium is known to be fused away into other elements, within the first 3 million years of stars' lives. Presence of lithium usually indicates that the star will not have yet made its way onto the Main Sequence of the Hertzsprung-Russell diagram - where most stars (like our one) are situated.
Clearly, being a Red Dwarf, this isn't quite right - the lithium must have been absorbed from somewhere else - a metallic body - a planet.
The astronomers suspect that the subject planet's dive into the star was part of an interaction that 'boomeranged' the other planet into the exceptionally elliptical orbit that it now occupies.

More about oddly orbiting planets:
'Jet-set young sun pushed baby planets off kilter'
Exoplanets have been seen in weirdly off-centre orbits around their stars, and this is inferred to be because of interactions with other planets, causing them to ping off in an odd direction.
But the planets of our own solar system are also off-kilter - 6 degrees mis-aligned from the Sun's equator. This mild eccentricity suggests it's the Sun that's been shoved.
"Hubble observations in the past 10 years have revealed that young stars with planet-forming discs can shoot jets of material from their poles. Often one jet can carry up to twice as much material as the other. Whichever jet is stronger pushes on the star."
"[Namouni] ran 2000 supercomputer simulations of the orbits of Jupiter and Saturn, which hold most of the solar system's planetary mass, over the lifetime of the sun. In most cases, the simulations that included the asymmetric jets produced planets with a 6-degree tilt."

[video] BIG cosmology, now:
'WiggleZ confirms the Big Picture of the Universe'
Einstein's cosmological equations assumed that the universe would be smooth at the largest scales, but this was an assumption. If wrong, it would mean a rewrite to cope with those largest scales.
Using the Anglo-Australian Telescope, PhD student Morag Scrimgeour has found that on scales larger than 350 million light years, matter is distributed extremely evenly, with little sign of fractal-like patterns, finding Einstein's assumption to be well-founded after all.

'The Milky Way now has a twin (or two)'
The Milky Way is not peculiar, it seems. While typical, in isolation, the Milky Way has been thought odd to have the Magellanic clouds as companions through the cosmos.
Astronomers from Australia to Scotland have teamed up, and found that there are galaxies in a similar position.
"Everything had to come together at once: we needed telescopes good enough to detect not just galaxies but their faint companions, we needed to look at large sections of the sky, and most of all we needed to make sure no galaxies were missed in the survey"
"We found about 3% of galaxies similar to the Milky Way have companion galaxies like the Magellanic Clouds, which is very rare indeed. In total we found 14 galaxy systems that are similar to ours, with two of those being an almost exact match," says Dr Robotham.

[video] I mentioned this a couple of weeks ago, in 'Astrophysics', and the event has arrived -- Voyager 2's journey into space is now 35 years old!
Voyagers 1 and 2 are 18 and 15 billion kilometres from the Sun, respectively, and are telling us things about the solar system that no-one sitting on Earth could possibly see from here.
As Voyager 1 makes its way out of the Sun's heliosphere, we will for the first time, be able to say that mankind has put something into inter-stellar space, and we will finally be able to find out what's really going on 'outside'.

'Supernovae of the same brightness, cut from vastly different cosmic cloth'
Unlike in a Type II supernova, where the mass of the star itself is purely to blame for the subsequent explosion, Type Ia supernova can be caused by different conditions, so long as there is a White Dwarf star to 'go bang'.
One of the mentioned supernovae occurred as a Red Giant's matter was cleaved off, onto the White Dwarf, resulting in a very bright supernova. This, of course, can happen repeatedly, as long as the White Dwarf remains existant.
In comparison, the system SN 2011fe shows no evidence of a Red Giant, indicating that there multiple ways to 'cut a stellar rug'.


Recently Sally Ride, and now Neil Armstrong has died, aged 82. It's a reminder to us all, how time passes - all our heroes are getting old.
Sally Ride:

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