Comet Leonard, which was expected to light up the skies throughout this month, appears to be fading, scientists say – but they don’t know why.
Since its discovery in January this year, the comet has been fast approaching both the Sun and Earth, at nearly 160,000 miles per hour.
But according to scientists, it may already be splitting up less than a year after it was first discovered, or it will begin to split up soon.
The cosmic ice ball is still set to offer stargazers a rare treat this weekend as it passes by Earth for the first time in 70,000 years.
It’s expected to be visible in the Northern Hemisphere’s pre-dawn sky as it increases in brightness during December, but after this it might disintegrate.
Visibility will be best through binoculars or a telescope, and in dark sky areas from this Sunday (December 12).
The comet will likely be lost to view after Christmas, reaching its closest point to the Sun on January 3 at a distance of 57.2 million miles (92 million km).
Once it rounds our star, it will be thrown out of the solar system into a slightly hyperbolic orbit, never to be seen again.
The newly discovered Comet Leonard (pictured) is set to light up the sky this month, as it passes by Earth for the first time in 70,000 years
LEONARD: AN INBOUND LONG PERIOD COMET
Catalogued as C/2021 AI, comet Leonard is named after the astronomer that first discovered it.
Gregory J Leonard spotted the comet using the Mount Lemmon Observatory on January 3, 2021 .
This was a year before it hit perihelion (the closest approach to the sun).
It last appeared in the inner solar system 70,000 years ago and so is on a 70,000 year orbit of the sun.
This will be its last orbit as it is on a hyperbolic trajectory, meaning it will leave the solar system after its close approach to our host star.
Comet Leonard was discovered by astronomer Gregory J Leonard on January 3 at the Mount Lemmon Infrared Observatory in Arizona and catalogued as C/2021 AI.
Quanzhi Ye, an astronomer at the University of Maryland, told Space.com that the comet is already fading as it approaches Earth, which is strange because it should be getting brighter before a close approach.
When a comet’s orbit brings it close to the Sun, it heats up and spews dust and gases into a giant glowing head larger than most planets.
‘It’s not great news. The comet should be brighter and brighter,’ Ye said. ‘If it’s not getting brighter then something’s wrong, but we don’t know exactly what at this stage.’
Comets – also called ‘cosmic snowballs’ or ‘icy dirtballs’ – are conglomerations of frozen gas, dust and ice left over from the formation of the solar system.
Comets go around the sun in an orbit that’s highly elliptical, meaning they’re not perfectly circular.
They can spend hundreds and thousands of years out in the depths of the Solar System before they return for their ‘perihelion’ – their closest approach to the Sun.
But Comet Leonard has a hyperbolic orbit, meaning once it passes the Sun it will be ejected out of the Solar System and never seen again by Earthlings.
Comet Leonard is already showing signs of a tail as it begins to warm up on its approach towards the inner solar system, astronomers explained
Comet C/2021 A1 Leonard on February 12. If it does fall apart, researchers may never know why
DIFFERENT TYPES OF SPACE ROCKS
An asteroid is a large chunk of rock left over from collisions or the early solar system. Most are located between Mars and Jupiter in the Main Belt.
A comet is a rock covered in ice, methane and other compounds. Their orbits take them much further out of the solar system.
A meteor is what astronomers call a flash of light in the atmosphere when debris burns up.
This debris itself is known as a meteoroid. Most are so small they are vapourised in the atmosphere.
If any of this meteoroid makes it to Earth, it is called a meteorite.
Meteors, meteoroids and meteorites normally originate from asteroids and comets.
Comet Leonard likely spent about 35,000 years coming inbound from about 323 billion miles (520 billion km) away and may have last visited the inner solar system about 70,000 years ago.
Ye said that the first sign a comet is doomed is that it loses its ion tail – a stream of charged particles pointing from the comet in the direction opposite the sun.
‘Comets do all sorts of weird things – sometimes they disintegrate before reaching perihelion, sometimes after, and there are even hypotheses saying that comets can disintegrate when they’re farther out from the Sun,’ Ye said. ‘So we won’t know until we see it happen.’
‘Why it’s fading, there are all kinds of hypotheses,’ Ye said. ‘The simplest and the most obvious one is something unhealthy is happening to the comet.’
One possibility, he told Space.com, is that it could it be running out of ice for the Sun to vaporise. Another is that the gravitational tug of the Sun or a large planet could pull it apart.
If it does fall apart, experts may never know why. However, Ye said the public will be able to enjoy ‘something pretty bright’ this month because it takes time for comets to fully disintegrate.
Comet Leonard makes its closest approach to Earth on Sunday, December 12, prior to its perihelion on January 3. On Sunday, it will be around 21.7 million miles away from our home planet.
Starting around December 14, the comet will appear in the evening sky for viewers in both hemispheres, according to the Planetary Society, before sweeping by Venus on December 18.
The newfound comet C/2021 A1 (Leonard) will make its closest approach to Earth on Dec. 12, 2021. Once it rounds our star it will be thrown out of the solar system into a slightly hyperbolic orbit, never to be seen again
People in the Southern Hemisphere should get their best view on December 14, when the comet may be visible above the horizon after sunset.
Throughout the month, including Christmas Day, it may even be possible to spot the bright green iceball briefly in the evening shortly after sunset, astronomers say.
The comet has a green tail because its icy rock interior heats up the closer it gets to the sun, first emitting a blue dust, then yellow or white and finally green.
When it turns this teal colour, it means the comet is warm, contains lots of cyanide and diatomic carbon and the potential for it to break up is at its highest.
‘MEGACOMET’ IS AMONG THE MOST DISTANT ICE BALLS WITH AN ACTIVE STREAM OF DUST AND GAS AROUND IT, STUDY CLAIMS
‘Megacomet’ Bernardinelli-Bernstein has been vaporising carbon monoxide as it gets warmer during its approach of the sun, a new study shows.
Astronomers have analysed satellite images of the comet, also known as C/2014 UN271, which was identified earlier this year.
Active comets, like Bernardinelli-Bernstein (BB), develop a thin envelope of vaporized ice and dust surrounding it, known as a coma, as they approach the Sun.
BB’s vaporised ice is not water, but carbon monoxide, the researchers found, which is known on Earth for its ability to fatally poison humans.
BB, named after its discoverers, measures 62 miles (100 km) across – more than 100 times the diameter of a typical comet. Usually comets are no bigger than about half a mile (1km) in diameter.
It’s been called the largest comet found in recorded history, though some have suggested that Comet Sarabat, which is more than 513,000 miles wide and spotted during a close approach of 1729, is larger.
BB is also thought to have a mass at least 1 million times greater than typical comets, as well as a diameter that’s 100 times greater.
BB is more than 1.8 billion miles (2.9 billion km) away from Earth, but is gradually getting closer to the centre of the Solar System.
Read more: Megacomet Bernardinelli-Bernstein is among most distant active comets