Bizarre ‘asteroid’ with a TAIL of gas spotted orbiting the Sun ‘a simple comet’

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The space rock was spotted by astronomers using the ATLAS system. This ATLAS image of 2019 LD2 (indicated by two red lines) is almost lost in crowded field of stars


Bizarre ‘asteroid’ with a TAIL of gas spotted orbiting the Sun at the same distance as Jupiter turns out to be a comet ‘in disguise’

  • The asteroid was first spotted in 2019 and the tail was confirmed in April 2020 
  • 2019 LD2 is letting off gas which is trailing behind the space rock like a comet tail
  • Astronomers confirmed it was a comet in an unusual orbit in a follow up study 

An unusual stellar object – thought to be an asteroid with a comet like tail – was actually just a comet in disguise, according to astronomers.

Scientists discovered 2019 LD2 sharing an orbit with Jupiter earlier this month, leading them to believe it was a unique crossover between an asteroid and a comet.

A follow up study by the University of Hawaii confirmed they were wrong and in fact it was a simple comet that had a ‘chaotically changing orbit’.  

The newly discovered comet was found in a swarm of asteroids known as the Jupiter Trojans but astronomers now say it is part of the Jupiter-family of comets.

The space rock was spotted by astronomers using the ATLAS system. This ATLAS image of 2019 LD2 (indicated by two red lines) is almost lost in crowded field of stars

The comet is under the influence of Jupiter’s gravity and has been renamed to match its new designation – P/2019 LD2 – its orbit is expected to change again in future.

It’s been described by the Hawaii astronomers as an ‘interloper comet masquerading as a member of the Trojan population.’ 

It was found last year by astronomers using the Asteroid Terrestrial-Impact Last Alert System (ATLAS) and showed up as a faint new signal in the Trojan group.

Follow up observations of the asteroid in June 2019 allowed astronomers to believe it had comet like properties – a tail – this is because it was actually just a comet.

True Jupiter asteroids have orbits closely following Jupiter as it goes around the Sun – but they’re clumped ahead or behind the giant planet.

They sit at Lagrangian points – spots where the combined gravitational forces of two large bodies create an area of gravitational stability – in this case Jupiter and the Sun.

The Jupiter-family comets, that this is now a member of, have a more typical comet-like orbit that can extend from way out beyond Saturn to the inner solar system.

According to astronomers, P/2019 LD2 travels along this orbit close enough to Jupiter that the gas giant’s gravitational pull can dramatically change its orbit.

The team behind the study say that is what we’re seeing now but it is temporary.

‘In the case of P/2019 LD2, its location and orbit currently approximates the position and near-circular orbit of Jupiter Trojan asteroids,’ the team wrote. 

‘The current orbit is not stable, meaning Jupiter will alter it again in the coming decades and comet P/2019 LD2 will no longer be easily confused with a Jupiter Trojan asteroid.’ 

It was found last year by astronomers using the Asteroid Terrestrial-Impact Last Alert System (ATLAS) and showed up as a faint new signal in the Trojan group

It was found last year by astronomers using the Asteroid Terrestrial-Impact Last Alert System (ATLAS) and showed up as a faint new signal in the Trojan group

NASA is launching a spacecraft next year to visit and study the Jupiter Trojan asteroids – although LD2 isn’t on the list of asteroids it plans to visit.

For now we have ATLAS and other telescopes to study objects like P/2019 LD2.

‘Even though the ATLAS system is designed to search for dangerous asteroids, ATLAS sees other rare phenomena in our solar system and beyond while scanning the sky,’ said ATLAS project principal investigator Larry Denneau. 

‘It’s a real bonus for ATLAS to make these kinds of discoveries.’

The Hawaii team say it is still an important scientific discovery, despite not being a new kind of asteroid. 

Explained: The difference between an asteroid, meteorite and other 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.

For example, if Earth passes through the tail of a comet, much of the debris burns up in the atmosphere, forming a meteor shower.

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