From The Editors Science

Witness the Closest Earth Pass-by of Comet Wirtanen in Centuries This Sunday

After the spectacular display put up by the Perseid meteor shower that came in the wake of the comet 109P/Swift-Tuttle this past August, Earthlings are about to witness another major cosmic event when Comet 46P/Wirtanen makes its closest approach to Earth on Sunday (Dec 16).

It will pass within 7.1 million miles of our planet, which is about thirty times the distance between and us and the moon, and although it sounds like way too far away, it’s close enough to be observed without a telescope, provided the sky above your vantage point is dark enough.

In fact, it will be the closest Wirtanen has come to Earth in centuries and it’s unlikely that it will happen again for centuries.

NASA says this will be one among the ten closest comet flybys of Earth in the last seventy years and the twentieth closest approach since as far back as the ninth century.

“This will be the closest comet Wirtanen has come to Earth for centuries and the closest it will come to Earth for centuries,” said Paul Chodas – Manager of the NASA NEO (Near-Earth Objects) Program Office at the space agency’s Jet Propulsion Laboratory (JPL) in Pasadena, California.

“This could be one of the brightest comets in years, offering astronomers an important opportunity to study a comet up close with ground-based telescopes, both optical and radar,” Chodas said.

For scientists, the proximity of the Wirtanen flyby will provide a rare and welcome opportunity to glean as much comet data as possible, which should go a long way in helping them unravel some of the longstanding mysteries of the solar system.

Dennis Bodewits, an astrophysicist and researcher at the Auburn University in Alabama, will have the best seat in the house to view and study the event for his intended research on the icy composition of the comet and the chemical processes that change the gas around it.

He is being given access to not one, not two, but three powerful NASA telescopes, including the Hubble Space Telescope, the Chandra X-ray Observatory and the Neil Gehrels Swift Observatory for his study.

“We’re going to be observing Comet 46P/Wirtanen with as many telescopes as we can get our hands on,” Bodewits said.

“The timing of this comet could not be better as our observations will allow us to apply all we learned from Rosetta to a completely different comet,” he added.

“These observations are like a space mission in reverse because the comet flies by us,” he explained.

While the Sunday flyby is important for scientists under any circumstances, it is even more so because it is likely to add more meaning to the European Space Agency’s Rosetta and NASA’s Deep Impact missions in 2004 and 2005, respectively.

The Rosetta spacecraft chased the Churyumov-Gerasimenko comet for more than two years around the sun, while Deep Space studied the interior of a comet by colliding an impactor with the comet’s nucleus so it could trigger the release of material from below the surface.

The Deep Space probe also managed to capture detailed images of another the comet – the Hartley 2 – as well.

“Because the comet comes very close to Earth, we can investigate the inner 200 kilometers around the nucleus, a region we cannot resolve for most comets,” he said.

“The comet appears to be a close twin to comet Hartley 2, the second target of the Deep Impact mission,” Bodewits said.

“Hartley 2 puzzled astronomers because it releases much more gas than was expected from its size,” he said, adding that comparing data would allow researchers to get a better understanding of the workings of comets.

ESA’s Rosetta mission, on the other hand, allowed scientists to learn more about a comet’s nucleus and, to some extent, the origins of the solar system, as well.

“It unexpectedly found a lot of molecular oxygen gas and discovered that electron collisions can change the comet gas,” he said.

“These are both important because they inform us what ices made up the building blocks of our solar system, and how they were altered by light and radiation from the Sun,” added the Auburn University researcher.

According to Brad Tucker from the Australian National University Research School of Astronomy and Astrophysics, your best bet to see the fuzzy green-tailed comet would be to “look towards the east with a small pair of binoculars or a telescope.”

He said it will be near the Orion constellation – “the saucepan” – which is “always easy to find by the bright stars that make up his belt.”

“Wirtanen’s comet could easily be chosen again for another mission,” CNN quoted Jim Lattis – director of the University of Wisconsin astronomy outreach center, UW Space Place – as saying.

“So that means watching this comet each time it comes near could be important,” he said.

“We’re getting a look at stuff that was formed during the formation of the solar system and has been out in the deep freeze since then,” Lattis added.

“When these things come in and we get a chance to study them, we’re seeing some of the raw materials out of which the Earth and the other planets and everything else formed,” he also told CNN.

Earlier this week, NASA’s NORISIS-REx (Origins, Spectral Interpretation, Resource Identification, Security, Regolith Explorer) made a stunning discovery within a week of reaching the proximity of asteroid Bennu.

Spectroscopic surveys of its surface revealed the presence of hydrated minerals, signifying that the space rock had interacted with liquid water at some point in its past

Although NORISIS-REx’s onboard spectrometers didn’t detect water per se, they did find hydrogen and oxygen bonds called hydroxyls trapped in clay-bearing material all over Bennu’s rock-strewn topography.

Over the coming months, the NASA spaceship, which is on an asteroid probe and sample-return mission to Bennu, will make increasingly closer passes of the asteroid, entering orbit on New Year’s Eve.

It will then begin mapping the asteroid to identify the best possible sample site before making a slow descent to the surface to collect samples using its robotic arm.

OSIRIS-REx is capable of making as many as three attempts at collecting the samples, after which it will have to begin its return journey, with its precious cargo of Bennu samples safely tucked away inside a Sample-Return Capsule (SRC).

The SRC is expected to re-enter Earth’s atmosphere and land at the US Air Force’s Utah Test and Training Range on Sep 24, 2023.

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