Hot Gas Bridge Discovered Connecting Galaxy Clusters

An “bridge” of hot gas stretches between galaxy clusters Abell 401 and Abell 399

It may not be good practice to burn bridges but this is one super-heated bridge that astronomers were happy to find: an enormous swath of hot gas connecting two galaxy clusters 10 million light-years apart, and nearly a billion light-years away.

Using ESA’s Planck space telescope, astronomers have identified leftover light from the Big Bang interacting with a filament of hot gas stretching between Abell 401 and Abell 399, two galactic clusters each containing hundreds of individual galaxies.

Launched in May 2009, Planck is designed to study the Cosmic Microwave Background (CMB) — the leftover light from the Big Bang. When this radiation interacts with large-scale cosmic structures, like the hot gas bridging clusters of galaxies, its energy is modified in a specific way. This is referred to as the Sunyaev–Zel’dovich Effect (SZE), and Planck is specifically attuned to finding it.

This, however, is Planck’s first discovery of inter-cluster gas found using the SZ technique.

The temperature of the gas is estimated to be around 80 million degrees C, similar to the temperature of the gas found within the clusters themselves. It’s thought that the gas may be a combination of cosmic web filaments left over from the early Universe mixed with gas from the clusters.

The image above shows the clusters Abell 401 and Abell 399 as seen at optical wavelengths with ground-based telescopes overlaid with the SZE from Planck. The entire bridge spans a distance about the size of two full Moons in the sky.

Read more on ESA’s news page here.

Top image: Sunyaev–Zel’dovich effect: ESA Planck Collaboration; optical image: STScI Digitized Sky Survey. Inset image: Artist’s impression of Planck against the CMB. (ESA and the HFI Consortium, IRAS)

How Do Microwaves Work

How Do Microwaves Work
microwave oven

[/caption]Microwave ovens don’t operate in the same manner as conventional ovens. So how do microwaves work then? Microwave ovens take advantage of the behavior of water molecules when subjected to electromagnetic waves found in the microwave band.

To understand how this happens, we’ll have to comprehend the basic properties of water molecules and microwaves (the electromagnetic waves, not the oven).

The mickey mouse-shaped water molecule is actually a dipole. That is, one side is positively charged while the other is negative.

Microwaves used for cooking, on the other hand, are electromagnetic waves possessing frequencies around the 2.45 GHz range. Now, electromagnetic waves are waves made up of alternating electric and magnetic fields. For this discussion, we’re more concerned with the alternating electric fields because charged particles readily react when exposed to them.

That is, when a positively charged particle is exposed to an electric field, it experiences a force (due to the field) pointing in the direction of the field. By contrast, when a negatively charged particle is exposed to the same field, it experiences a force in the direction opposite to the field.

Now, since an electromagnetic wave (like the microwave) is made up of alternating electric fields, a charge exposed to it will experience forces regularly changing in direction. For water molecules, which are dipoles, the net effect would force the molecules into rotation. Again, since the fields are alternating, the rotation will change from clockwise to counterclockwise at regular time intervals.

The agitated water molecules would then possess heat energy that can rub off (much like friction) to nearby molecules. If the water molecules are well distributed in the body subjected to the microwave (like food, for example), then the entire body can heat up quickly – not to mention, uniformly.

Electromagnetic waves in the microwave range are most suitable for this purpose because the water molecules readily rotate when exposed to such frequencies.

Avoid putting in metal into the microwave oven while heating. The reason is because pointed portions of the metal can accumulate high voltages which can cause dielectric breakdown of the air inside the oven. Once this happens, some harmful gases can be produced.

Since microwave ovens normally don’t have heating elements, temperature can drop right away in the inner walls of the oven. So you’ll only need to worry about getting burned by the food and not the walls.

You can read more about electromagnetic waves here in Universe Today. Want to know about how the 25-year old mystery of X-ray emissions was solved? We’ve also written about how astronomers resolved Milky Way’s mysterious X-Ray glow

There’s more about it at NASA and Physics World. Here are a couple of sources there:
X-Ray Astronomy
X-ray Beams Thin Out

Here are two episodes at Astronomy Cast that you might want to check out as well:
X-Ray Astronomy
Optical Astronomy

Source: Wikipedia