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Three-mile-wide asteroid to make closest pass by Earth December 16



*‘Death planet’ with toxic atmosphere made almost entirely of carbon monoxide baffles astronomers

The United States National Aeronautic Space Agency (NASA) has confirmed that an enormous asteroid will brush pass Earth on December 16, 2017.The asteroid, called 3200 Phaethon, measures three miles (five kilometres) in diameter, and is classed as ‘potentially hazardous.’

During the pass, the asteroid is estimated to be around 6.4 million miles away from our planet – around 27 times the distance between the Earth and the moon.It will be the closest this asteroid has been to Earth since December 16, 1974, when it was around five million miles away.

Also, a mysterious planet that lies 325 light years away from Earth has been found to have one of the most bizarre atmospheres ever observed.The over-sized planet, called Wasp-18b, is wrapped in a smothering layer of carbon monoxide with absolutely no water – a finding that astronomers say “defies expectations’.

This is one of the first times that such a combination has been seen, and has led some to nickname Wasp-18b the ‘death planet.’Meanwhile, the asteroid is named after the son of the Greek sun god Helios ‘Phaethon’ because it passes so close to the sun.

Legend claims the young demi-god was challenged to prove he was related to Helios, who was said to pull the sun across the sky.To prove his divine provenance, Phaethon rode his father’s chariot, but was unable to control the horses, who then ran wild across the sky, dragging the sun with them.

Earth was almost destroyed in the ensuing chaos, which scorched the planet, burned vast amounts of vegetation and created the great deserts of Africa. In a statement about the asteroid, a spokesperson for NASA said: “With a diameter of about 5 km, Phaethon is the third largest near-Earth asteroid classified as ‘Potentially Hazardous’.”

NASA expects Phaethon to make its closest pass with Earth on December 16, during which time the space agency hopes to take detailed images of the asteroid.The NASA spokesperson said: “Phaethon will approach within 0.069 au of Earth on 2017 December 16 when it will be a strong radar imaging target at Goldstone and Arecibo.

“This will be the best opportunity to date for radar observations of this asteroid and we hope to obtain detailed images. The images should be excellent for obtaining a detailed 3D model.”The next pass is predicted to be in 2093.

NASA’s statement comes just day after experts at the Immanuel Kant Baltic Federal University in Konigsberg, Russia, published a video tracking the path of Phaethon.The video explains that the asteroid’s unusual orbit will see it pass closer to the sun than any other named asteroid. 3200 Phaethon has puzzled scientists because it has features of both an asteroid and a comet.

During a recent pass of another asteroid, NASA used its international network of observatories to recover, track and characterise asteroid 2012 TC4.

As it started to approach Earth in the coming months, large telescopes were used to detect it and establish the asteroid’s precise trajectory. The new observations have helped refine knowledge about its orbit, narrowing the uncertainty about how far it will be from Earth in future passes.

In one of its previous close encounters with Earth, scientists spotted dust streaming from the space rock that resembles the melting ice tails seen tailing most comets.But Phaethon’s orbit puts its origins in a region between Mars and Jupiter where asteroids commonly originate.

Typically, icy comets come from colder regions of space beyond Neptune. In a statement, Immanuel Kant Baltic Federal University said: “Apparently, this asteroid was once a much bigger object.“But its many approaches to the sun have caused it to crumble into smaller pieces which eventually formed this meteor shower. If so, the asteroid itself could be the residue of a comet nucleus.

“The asteroid’s extremely elongated orbit, thanks to which it sometimes gets to the Sun closer than Mercury and it sometimes moves away farther than Mars, is another argument in favour of this theory.”

Researchers from NASA’s Goddard Space Flight Center in Greenbelt, Maryland used the Hubble and Spitzer space telescopes to analyse Wasp-18b’s stratosphere.The unusual composition of carbon monoxide with no water suggests that the formation of the planet may have been very different to that of other gas giants.

Dr. Kyle Sheppard, lead author of the study, said: “The composition of WASP-18b defies all expectations.“We don’t know of any other extrasolar planet where carbon monoxide so completely dominates the upper atmosphere.”On Earth, ozone absorbs UV in the stratosphere, protecting our planet from a lot of the sun’s harmful radiation.

And for most other exoplanets with stratospheres, this absorber is usually a molecule such as titanium oxide.In the study, the researchers analysed data collected for Wasp-18b, including five eclipses from archived Hubble data and two from Spitzer.

By analysing the light emitted by the planet’s atmosphere, the researchers revealed Wasp-18b’s unusual fingerprint.Dr. Nikku Madhusadhan, co-author of the study, said: “The only consistent explanation for the data is an overabundance of carbon monoxide and very little water vapor in the atmosphere of WASP-18b, in addition to the presence of a stratosphere.

WASP-18b is a ‘hot Jupiter,’ a giant exoplanet that orbits very close to its star, located about 330 light years from Earth.Specifically, the mass of WASP-18b is estimated to be about ten times that of Jupiter, yet it orbits its star about once every 23 hours.

By comparison, it takes Jupiter about 12 years to complete one trip around the sun from its great distance.“This rare combination of factors opens a new window into our understanding of physicochemical processes in exoplanetary atmospheres.”The analysis suggests that Wasp-18b has hot carbon monoxide in the stratosphere and cooler carbon monoxide in the layer of the atmosphere below – called the troposphere.

Compared to other gas giants, the researchers suggest that Wasp-18b’s atmosphere would contain 300 times more ‘metals’ – elements heavier than hydrogen and helium.This very high metallicity indicates that Wasp-18b may have accumulated greater amounts of solid ices during its formation than Jupiter – suggesting it may have formed in a different way to other gas giants.

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