In a blog post published Friday, NASA shared some of the latest photos of comet 46P/Wirtanen, an object that has frequently been described as the brightest comet to be visible from Earth in 2018.
As noted by NASA, some of the original photos were taken by the Hubble Space Telescope on December 13, at a time when the comet was approximately 7.4 million miles (12 million kilometers) from Earth. These shots were then blended into a composite image, as the space agency added shades of blue to the high-resolution grayscale exposures captured by Hubble’s Wide Field Camera 3 (WFC3) instrument.
This composite was a visible-light image that, according to BGR, made 46P/Wirtanen a bit difficult to pinpoint, as it was shown “tucked away” within the brightest part of the blue cloud’s center. Per NASA, the blue cloud in the composite represented the comet’s coma, or a cloud of gas and dust ejected by the object as it makes its way through the inner solar system and moves closer to the sun.
“The inner part of a comet’s coma is normally not accessible from Earth,” NASA explained.
“The close flyby of comet 46P/Wirtanen allowed astronomers to study it in detail. They combined the unique capabilities of Hubble, NASA’s Chandra X-ray Observatory and the Neil Gehrels Swift Observatory to study how gases are released from the nucleus, what the comet’s ices are composed of, and how gas in the coma is chemically altered by sunlight and solar radiation.”
Aside from the above composite image, NASA’s blog post included a second photo of the so-called brightest comet of the year. This image was taken by the space agency’s Stratospheric Observatory for Infrared Astronomy (SOFIA) on December 16 and 17 as the craft flew at about 40,000 feet, and allowed for a more defined look at 46P/Wirtanen’s nucleus.
Per NASA, the photo was taken with SOFIA’s visible-light guide camera and made use of an orange filter to represent the intensity of light from the comet in relation to other objects.
Late last week, Hubble captured an image of Comet 46P/Wirtanen, just before the comet made its closest approach to Earth. The comet is currently visible with binoculars and telescopes near the constellation Taurus: https://t.co/EIR4hBuJDA pic.twitter.com/6Mcg3jQK4t— Hubble (@NASAHubble) December 20, 2018
As comets and asteroids are thought to have been one of the key sources of water on our planet in its earlier years, NASA pointed out the importance of SOFIA’s findings, as the team behind the spacecraft analyzes the chemical fingerprints of the various hydrogen isotopes in the water content of comets, 46P/Wirtanen included.
Despite being the brightest comet of 2018, 46P/Wirtanen is only “barely visible” without the use of a telescope or binoculars, even in situations where the sky is extremely dark. According to NASA, the comet made its closest approach to Earth on Sunday, December 16, when it was approximately 7 million miles away from Earth, or about 30 times the distance separating our planet from the moon.
Unlike the far more iconic Halley’s Comet, which orbits the sun every 75 years, 46P/Wirtanen does so once every 5.4 years, though previous passes through the inner solar system were considerably farther away from Earth as compared to this month’s flybys.