NASA's SOHO Mission

News Excerpt: 

NASA's SOHO mission celebrates a milestone as it captures the 5,000th comet on its journey around the Sun.

About SOHO Mission:

  • Soho, the Solar & Heliospheric Observatory was launched on December 2, 1995 with a package of 12 instruments onboard
    • The mission has 12 instruments, including telescopes and spectrometers, which observe the Sun in various wavelengths of light, from ultraviolet to visible X-rays
  • A joint project of the European Space Agency (ESA) and NASA. It is designed to study the Sun, its atmosphere, and the solar wind.
  • It has provided knowledge into the structure of the Sun, including its magnetic field, solar flares, coronal mass ejections (CMEs), and solar variability.
  • SOHO monitors the effects of space weather on our planet, and it plays a vital role in forecasting potentially dangerous solar storms.
  • SOHO is the most prolific discoverer of comets in astronomical history,

Latest Findings: 

  • Now,the SOHO mission has achieved a milestone in its journey by capturing its 5,000th comet as it traverses around the solar star in our cosmic neighborhood.
  • These observations help scientists better understand solar phenomena and their impact on space weather, which can affect satellites, power grids, and communication systems on Earth.
  • The latest comet, named SOHO-5000, belongs to the Marsden group. 
    • It is a part of the larger comet 96P/Machholz.
  • SOHO remains the most successful comet-hunting spacecraft to date and shows no signs of slowing down.
  • SOHO has provided information about its core and outer atmosphere
    • Notable achievements include the first-ever images of the Sun's convection zone and sub-surface sunspots, as well as detailed measurements of rotation and temperature.
  • It has also pinpointed the origins and acceleration mechanisms of the solar wind, particularly in magnetically "open" polar regions 
    • while uncovering novel solar phenomena like coronal waves and solar tornadoes

What is a Comet?

A comet is a small celestial object composed of ice, gas, dust, and a small amount of organic material that orbits the Sun. They are often referred to as "dirty snowballs" due to their composition. Comets are visible to us when they approach the Sun and begin to heat up, causing the emission of gasses and dust that form their characteristic tails. Comets are remnants from the early stages of the solar system's formation, approximately 4.6 billion years ago.

Comets originate from two main regions in the outer solar system:

  • Kuiper Belt: This is a region beyond the orbit of Neptune containing icy bodies. Comets originating from here are termed short-period comets because their orbits take less than 200 years to complete.
  • Oort Cloud: This is a much more distant region surrounding the solar system, containing icy objects. Comets from the Oort Cloud have highly eccentric orbits and can take millions of years to complete one orbit around the Sun.

The main parts of a comet include:

  • Nucleus: The solid center of the comet, comprising ice, rock, dust, gases (such as carbon dioxide, methane, and ammonia), and organic material.
  • Coma: The coma surrounds the nucleus and is essentially the comet's atmosphere. It consists of gas and dust emitted from the nucleus as it heats up near the Sun.
  • Hydrogen Cloud: This is part of the coma and consists of hydrogen gas.
  • Dust Tail: As the comet approaches the Sun, the solar wind blows the coma's dust particles away from the Sun, forming a long, whitish-yellow tail. Dust tails can be millions of kilometers long.
  • Gas Tail (Plasma Tail): Composed of ionized gas, mainly carbon monoxide ions, the gas tail tends to appear bluish and can stretch for tens of millions of kilometers into space. It forms when solar ultraviolet light breaks down gas molecules in the coma, causing them to glow.
  • Sodium Tail: Although less common, some comets, like Comet Hale-Bopp, exhibit a third tail composed of sodium.

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