Astronomers spot first activity on giant mega comet beyond Saturn
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Spotting the first signs of activity on a comet of gargantuan size came down to a time-zone advantage. Astronomers in New Zealand were the first to spot a coma spreading around the mega comet C/2014 UN271, also known as Bernardinelli-Bernstein, which may be 1,000 times more massive than a typical comet. It could even be the most massive comet ever found in all of recorded history.
The team that monitors images captured by the Las Cumbres Observatory (LCO) is spread around the world, and images from one of LCO’s one-metre telescopes hosted at the South African Astronomical Observatory were available on 23 June at 05:00 BST. That happens to be afternoon in New Zealand. “The other folks were asleep,” recalled LCO team member Michele Bannister, of New Zealand’s University of Canterbury.
At first glance, however, she thought the new imagery was a bust thanks to the ever-present problem of satellites going through the field of view of telescopes. “The first image had the comet obscured by a satellite streak, and my heart sank,” she continued. “But then the others were clear enough, and there it was, definitely a beautiful little fuzzy dot, not at all crisp like its neighbouring stars.”
What caught Bannister’s attention was a foamy coma emerging at an incredible distance from the Sun, as the comet has a lot of mass available to heat up. Bernardinelli-Bernstein’s huge core is estimated to be more than 100 kilometres (62 miles) in diameter, three times as large as the next-largest comet nucleus – that of Hale-Bopp, a famous naked-eye comet that passed by Earth in 1998. Unfortunately for eager astronomers, however, Bernardinelli-Bernstein won’t get very close to our planet for observations.
Bernardinelli-Bernstein’s closest approach to the Sun will still be beyond Saturn in January 2031, but astronomers have a decade to plan for that approach. If history is any guide, telescopes around the world and in space, along with any spacecraft that happen to be nearby, will peer at the comet to learn as much as possible about its composition and history. And the LCO Outbursting Objects Key (LOOK) Project will continue to watch. It’s expected to be of help since its network of telescopes allows for a ‘rapid response’ within 15 minutes whenever any outbursts occur. But LCO won’t be the only one.
“There are now a large number of surveys, such as the Zwicky Transient Facility and the upcoming Vera C. Rubin Observatory, that are monitoring parts of the sky every night,” said LOOK member Tim Lister, an LCO scientist. “These surveys can provide alerts if one of the comets changes brightness suddenly,” he added. “Then we can trigger the robotic telescopes of LCO to get us more detailed data and a longer look at the changing comet while the survey moves on to other areas of the sky.”
Curiosity made a surprising discovery while investigating clay-rich sedimentary rocks around Gale crater, a former lake that was made when an asteroid struck the Red Planet roughly 3.6 billion years ago. Clay is a good signpost towards evidence of life because it’s usually created when rocky minerals weather away and rot after contact with water – a key ingredient for life. It’s also an excellent material for storing microbial fossils.
But when Curiosity took two samples of ancient mudstone, a sedimentary rock containing clay, from patches of the dried-out lake bed – dated to 3.5 billion years ago and just 400 metres (1,312 feet) apart – researchers found one patch contained only half the expected amount of clay minerals. Instead that patch held a greater quantity of iron oxides, the compounds that give Mars its rusty hue. The team believes the culprit behind this geological disappearing act is brine: super-salty water that leaked into the mineral-rich clay layers and destabilised them, flushing them away and wiping patches of both the geological and possibly even biological record clean. “We used to think that once these layers of clay minerals formed at the bottom of the lake in Gale crater they stayed that way, preserving the moment in time they formed for billions of years,” said Tom Bristow, a researcher at NASA’s Ames Research Center. “But later brines broke down these clay minerals in some places – essentially resetting the rock record.”
Astronomers have discovered a rare, teardropshaped star swirling through the cosmos some 1,500 light years from the Sun. Why does the star have this unusual shape? Because it’s in a toxic relationship with a partner, which is ripping the life from its body. In stellar relationships like these, there is no amicable uncoupling; the romance only ends when both stars explode in a violent, thermonuclear explosion that’s visible across the galaxy. But astronomers are fired up about this twisted stellar relationship. The system, HD265435, is one of only three known binary star systems in the universe – and the closest one to Earth – that is clearly destined to end in a Type Ia supernova.
These types of stellar explosions occur when a white dwarf shares an orbit with a larger, younger star that still has some fuel left to burn. Small but gravitationally massive, the white dwarf gladly gobbles up this fuel, yanking so much matter away from its companion that the younger star begins to change shape from a sphere into an ellipse, or teardrop. The older star grows larger and larger over millions of years, becoming too big for its own good. Nuclear reactions reignite in its core, the dwarf goes boom and both stars become an irradiated smudge of gas and dust in the night sky.
These stars fully orbit each other once every 90 minutes or so, indicating that they are extremely close and will probably merge completely millions of years from now. The pair has the right total mass to suggest that a Type Ia supernova is on the horizon – just another 70 million years or so away.