Universality in Space Plasmas?


In the Dark

It’s been a while since I posted anything reasonably technical, largely because I’ve been too busy, so I thought I’d spend a bit of time today on a paper (by Livadiotis & McComas in the journal Entropy) that provoked a Nature News item a couple of weeks ago and caused a mild flutter around the internet.

Here’s the abstract of the paper:

In plasmas, Debye screening structures the possible correlations between particles. We identify a phase space minimum h* in non-equilibrium space plasmas that connects the energy of particles in a Debye sphere to an equivalent wave frequency. In particular, while there is no a priori reason to expect a single value of h* across plasmas, we find a very similar value of h* ≈ (7.5 ± 2.4)×10−22 J·s using four independent methods: (1) Ulysses solar wind measurements, (2) space plasmas that typically reside…

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Looking at the Most Distant Galaxy in the Universe


Background

The Hubble Space Telescope was launched into space in 1990. Due to a technical problem that occurred during its installation, earlier images taken by the space telescope had some deformities in them. This problem was resolved in 1993. NASA published the first picture taken by the Hubble Space telescope back in January 1994.

The First Image taken by the Hubble Space Telescope Courtesy: Hubble Site

The First Image taken by the Hubble Space Telescope
Courtesy: The Hubble Site

Since then, the Hubble Space Telescope has been capturing a significant number of images of various celestial objects including stars and galaxies, which help to understand how our universe, galaxies and stars behave at a large-scale.

NASA’s Spitzer Space Telescope was launched in 2003, primarily aiming to do infrared observing. Infrared light is a form of electromagnetic radiation. As most of the infrared radiation gets absorbed by the earth’s atmosphere, the Spitzer Space Telescope was also launched into space to make observations in the infrared spectrum of the electromagnetic radiations.

Let’s remind ourselves a few definitions before we go farther. Stars are primarily composed of hydrogen, which fuses into helium. During this process energy is released. It causes the stars to shine in the night sky. Our sun is a star and we reside in a galaxy named the Milky Way. Assuming the universe is finite, the scientists found that the early universe was a very different place than the present observable universe. Right after the Big Bang, the universe was immensely hot. Eventually, the universe cooled off, and hydrogen atoms were formed.

News Headline

Last November, NASA announced that a joint collaboration between the Hubble Space Telescope and the Spitzer Space Telescope discovered the most distant galaxy in the observable universe. The galaxy was cataloged as MACS0647-JD. Surely, it does not have any fancy name like our own galaxy or our neighboring galaxy, Andromeda.

The Distant Galaxy  Image Courtesy: The Hubble Site

The Distant Galaxy
Image Courtesy: The Hubble Site

In astronomy, looking at a distant object is simply analogous to looking back in time. Astronomers found that the most distant galaxy was formed when the universe was only about 430 million years old; whereas, currently the universe is about 13.7 billion years old.

News Analysis

In a research paper published by Coe et al. from the Space Telescope Science Institute, the researchers claimed that their team found the most distant galaxy in our observable universe. The visual images were obtained using the Wide Field Camera 3 (WFC3) and the Advanced Camera for Surveys (ACS). For the infrared part, the Spitzer Space Telescope’s InfraRed Array Camera (IRAC) was exposed over 5 hours. As the object is really far away, the exposure time increases.

Importance

This galaxy was directly viewed because gravitational lensing helped us to see this distant celestial object. In principle, light can be bent by gravity. In the case of this distant object, there are numerous massive sources lie in between the light source and us. One can consider other galaxies and stars to be the intermediate massive sources, which bend light.These massive sources can also magnify the source you are aiming to look at. This phenomenon is known as gravitational lensing. The distant galaxy is visible to us because the intermediate mass-sources bend light and magnify its real size.

Finding this galaxy successfully testified various models on gravitational redshift. When a fast paced object moves towards the observer, its frequency gets shorter and the wavelength gets compressed. Blue light has a shorter wavelength than red light. That is why blue shift refers to an object moving towards us with a high speed. On the other hand, when an object moves away from us, it exhibits a red shift. The wavelength gets stretched away. Red light has a longer wavelength than blue light. In reality, gravity has the same effect on mass-less photons or light particles. By testing various models for gravitational redshifts, researchers concluded that this distant object first emitted light from it when the universe was only about 430 million years old. This observed galaxy had a really high red shift.

Researchers think that this distant object can be studied using the futuristic James Webb Space Telescope. This will reveal many unknown facts about the formation of big structures such as how primordial galaxies and stars shape our universe.