NASA’s Solar and Heliospheric Observatory, better known as SOHO, has just released a 15-second video featuring a rare sight: a comet flying by the sun at perihelion. What was remarkable about this adventure was that the comet, aside from its feat of travelling perilously close to the sun, actually survived this journey, which occurred from February 18 to February 21.
Comets which are this “brave” in their space travels, have been nicknamed sungrazers. It is, however, rare for these sungrazers to not disintegrate during these trips because of the intense sunlight, strong evaporation and tidal forces at that distance, which usually crumbles the fast-moving, mostly-ice heavenly bodies.
This sungrazer is also uncommon for NASA because it is what they call a non-group comet, that is, a comet that belongs to a family that NASA is not yet aware of. Most comets that travel within SOHO’s vicinity are part of the Kreutz family – bits of a larger comet that broke off several centuries ago.
This sungrazer which has been named C/2015 D1 (SOHO) travelled to within 2.2 million miles of the sun’s surface. Though it might have initially survived this trip, solar scientist Karl Battams suggests that the comet’s journey might cause it to die out faster.
SOHO is a joint effort between two space agencies, the National Aeronautics and Space Administration (NASA) and the European Space Agency (ESA), which was launched on December 2, 1995. SOHO was originally intended to study the internal structure of the sun, its atmosphere, flows of energized particles or solar winds, and the ionized gas that it has been expelling to the rest of the solar system. However, since its launch, it has become famous for finding comets that travel to our side of the universe. This current comet was SOHO’s 2,875th discovery.
Though comets are a common sight for SOHO, it rarely picks up non-group sungrazers that survive the close distance to the sun, which is why this risk-taker was definitely cause for excitement.
The video, which is posted on the NASA website and in SOHO’s mission page, shows the miniscule body (compared to the sun) passing very near the sun at perihelion, even disappearing behind the sun’s energy field for a few seconds, only to later reveal itself on the other side. And the sun, seemingly in response to this invasion of personal space, releases solar material, or a coronal mass ejection, a few seconds afterwards.
It was only in the 20th century that cosmologists realized that what they initially thought to be one comet orbiting close around the sun several times was actually numerous comets that were instead related to each other. This led to the creation of the families of comets.
For these sungrazing comets, the closer they get to the sun, the more dazzling they seem to be since the extreme heat from this solar system’s biggest star causes the ice that makes up a huge mass of the comet to evaporate into gas. This gas then reflects the light from the sun, which shows as a brilliant tail for us observers here on earth.