ENGI

unknownskywalker:

A Laser Beam Towards the Milky Way’s Centre

In mid-August 2010, a group of astronomers were observing the centre of the Milky Way using the laser guide star facility at Yepun, one of the four Unit Telescopes of the Very Large Telescope (VLT).

Yepun’s laser beam crosses the majestic southern sky and creates an artificial star at an altitude of 90 km high in the Earth’s mesosphere. The Laser Guide Star (LGS) is part of the VLT’s adaptive optics system and is used as a reference to correct the blurring effect of the atmosphere on images. The colour of the laser is precisely tuned to energise a layer of sodium atoms found in one of the upper layers of the atmosphere.

This layer of sodium atoms is thought to be a leftover from meteorites entering the Earth’s atmosphere. When excited by the light from the laser, the atoms start glowing, forming a small bright spot that can be used as an artificial reference star for the adaptive optics.

Using this technique, astronomers can obtain sharper observations. For example, when looking towards the centre of our Milky Way, researchers can better monitor the galactic core, where a central supermassive black hole, surrounded by closely orbiting stars, is swallowing gas and dust.

[ESO]

unknownskywalker:

Laws of Physics Vary Throughout the Universe, New Study Suggests

A team of astrophysicists based in Australia and England has uncovered evidence that the laws of physics are different in different parts of the universe.

The report describes how one of the supposed fundamental constants of Nature appears not to be constant after all. Instead, this ‘magic number’ known as the fine-structure constant — ‘alpha’ for short — appears to vary throughout the universe.

After measuring alpha in around 300 distant galaxies, a consistency emerged: this magic number, which tells us the strength of electromagnetism, is not the same everywhere as it is here on Earth, and seems to vary continuously along a preferred axis through the universe.

The implications for our current understanding of science are profound. If the laws of physics turn out to be merely ‘local by-laws’, it might be that whilst our observable part of the universe favours the existence of life and human beings, other far more distant regions may exist where different laws preclude the formation of life, at least as we know it.

The researchers’ conclusions are based on new measurements taken with the Very Large Telescope (VLT) in Chile, along with their previous measurements from the world’s largest optical telescopes at the Keck Observatory in Hawaii.

The Keck telescopes and the VLT are in different hemispheres — they look in different directions through the universe. Looking to the north with Keck a smaller alpha is seen in distant galaxies, but when looking south with the VLT a larger alpha is detected. It varies by only a tiny amount over most of the observable universe, but it’s possible that much larger variations could occur beyond our observable horizon.

The discovery will force scientists to rethink the understanding of Nature’s laws. The fine structure constant, and other fundamental constants, are absolutely central to our current theory of physics. If they really do vary, we’ll need a better, deeper theory. While a ‘varying constant’ would shake our understanding of the world around us extraordinary claims require extraordinary evidence. This finding is extraordinary, no doubt about that.

Image: Illustration of the dipolar variation in the fine-structure constant, alpha, across the sky, as seen by the two telescopes used in the work: the Keck telescope in Hawaii and the ESO Very Large Telescope in Chile.

[Science Daily]