M4L3: ASTROPHYSICS-II

So, welcome back. Now we shall jump to the technical aspects of Space research

First of all, let us try to understand the Electromagnetic radiation band

These bands are arranged from highest to lowest energies in the following order

Gamma > X-rays > U.V. > Visible > IR > Radio waves

So, when the celestial object possesses the highest amount of energy, it releases Gamma. Therefore Gamma-ray telescopes focus on the highest-energy phenomena in the universe, such as black holes and exploding stars.  Let us talk this in the light of the events that are happening to the nearest star… The Sun

When, you look at the image below, you will find that the core of the sun is the hottest. This means, it should be releasing Gamma radiation. The layer at the top is called photosphere which is still very hot, but obviously cooler when compared to the core. That layer releases X rays. It is now very important to understand that layer as it is plasma layer. While a lot of research has been done on solids, liquids and gas has been done, very little is known about plasma. Further improvement in its understanding will help us make fusion reactors more stable. Recall that India is also a part of ITER project.

So, do we have any project to study the corona discharges from the sun’ photosphere? India is going to launch Aditya mission by the end of calendar year 2019. NASA is also trying to do this using Parker Solar probe.

Parker solar probe is the fastest spacecraft in the world. It will fly as fast as 690,000 km/h.  The spacecraft will approach too much close to sun, 9.86 solar radii (6.9 million km) from sun's center

·         The cost of project in 1.5 Billion dollars

·   The name of the mission is taken from Dr. Eugene Parker, who first theorized the existence of the solar wind

·       ·         Parker solar probe is completely developed by NASA and has been launched in 2018, it would be closest object to orbit around sun

·        ·         Mission type is solar helio-physics mission

·        ·         Parker solar probe has launch weight of 685 kg

Parker Solar Probe’s instruments

1.    The Fields Experiment (FIELDS) will make direct measurements of the Sun’s electric and magnetic fields, and sniff and taste the plasma and radiation around the spacecraft.

2.    The Integrated Science Investigation of the Sun experiment (IS☉IS) will observe energetic particles leaving the Sun, including electrons, protons and heavy ions that are accelerated to high energies in the solar corona.

3.    The Wide-field Imager for Solar PRobe (WISPR)

WISPR is the only imaging instrument aboard NASA’s Parker Solar Probe to take photos of the solar corona and inner heliosphere region of the Sun’s atmosphere. It contains two telescopes incorporating Active Pixel CMOS detectors that will capture images of the sun’s atmosphere (or corona), including coronal mass ejections (CMEs) and help derive the 3D structure of the solar corona (source of Solar Energetic Particles (SEP) producing shocks)

4.    Finally, the Solar Wind Electrons Alphas and Protons (SWEAP) investigation will count the most abundant particles in the solar wind – electrons, protons and helium ions – and measure how fast they travel, their density and temperature.

Let us turn back to Aditya.

Aditya is a 400 kg satellite and will orbit the Lagrangian point 1 (L1) of the Sun-Earth system, about 1.5 million kilometers from the Earth. Lagrangian points are those points where the cumulative force of all the planets equals to that of the gravitational force of the sun. There are total 5 of them. L1 is on the front side, facing towards the sun

The Aditya mission will help to answer

1.    What is the structure and dynamics of the solar interior?

2.    Why does the solar corona exist and how is it heated to the extremely high temperature? of about 1 000 000°C?

3.    Where is the solar wind produced and how is it accelerated?

This mission is not the first one to study Sun. Earlier, NASA & European Space agency have already launched SOHO, the Solar and Heliosphere Observatory, to study the Sun, from its deep core to the outer corona, and the solar wind.

The Lagrangian points are named for Joseph Louis Lagrange, who realized that there would be stable or semi-stable points in the vicinity of every two orbiting bodies in space.

Aditya-L1 will be able to provide observations of Sun's photosphere, chromosphere and corona. In addition, particle payloads will study the particle flux emanating from the Sun and reaching the L1 orbit, and the magnetometer payload will measure the variation in magnetic field strength at the halo orbit around L1.

The seven payloads, that will be taken on board of Aditya satellite to investigate the Sun's corona are as follows.

1.    Visible Emission Line Coronagraph (VELC): To study the diagnostic parameters of solar corona and dynamics and origin of Coronal Mass Ejections

2.    Solar Ultra-Violet Imaging Telescope (SUIT): To image the spatially resolved Solar Photosphere and Chromosphere in near Ultraviolet (200-400 nm) and measure solar irradiance variations

3.    Aditya Solar wind Particle Experiment (ASPEX) : To study the variation of solar wind properties as well as its distribution and spectral characteristics

4.    Plasma Analyser Package for Aditya (PAPA) : To understand the composition of solar wind and its energy distribution

5.    Solar Low Energy X-ray Spectrometer (SoLEXS) : To monitor the X-ray flares for studying the heating mechanism of the solar corona

6.    High Energy X-ray Spectrometer (HEL1OS): To observe the dynamic events in the solar corona and provide an estimate of the energy used to accelerate the particles during the eruptive events

7.    Magnetometer: To measure the magnitude and nature of the Interplanetary Magnetic Field.

Prior to Aditya, India had also launched one more mission to study the stars. The anme of it was AstroSat. However, in this case, the star supposed to be studied is not Sun. They belong to the outer space. So, can you guess, if this should have been placed at L1 or L2 point? (L2 point faces outer space making it free from obstructions)

ASTROSAT too carried a similar set of instruments. It carried 1 Hard X ray telescope (CZTI or Cadmium Zinc telluride imager), 1 Soft X ray telescope (SXT) and 1 UV telescope (UVIT) and two other instruments as follows.

1.    Large Area X-ray Proportional Counter (LAXPC), is designed for study the variations in the emission of X-rays from sources like X-ray binaries, Active Galactic Nuclei and other cosmic sources.

1.    Scanning Sky Monitor (SSM), is intended to scan the sky for long term monitoring of bright X-ray sources in binary stars, and for the detection and location of sources that become bright in X-rays for a short duration of time.

The question is why X rays?

When the star explodes, it releases an immense amount of energy in the form of Gamma and X ray.  If the size of the star is greater than the sun, it first collapses into neutron star and then into black hole and quasars

Do you know? A light ray coming from behind the black hole bends itself. This phenomenon is called as gravitational lensing

Do you know? NASA has, for the first time used ‘X ray ‘coming from the pulsars a tool to navigate autonomous spacecrafts going far beyond the earth. That will guide the space craft like the GPS System does to us. The GPS uses signals from three satellites upon you to detect your exact location. China too has started working on it. They recently launched a mini satellite XPNAV 1 (X-Ray Pulsar Navigation) or Maichong Xing Shiyan Weixing