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(CNN) -- Scientists have discovered a "monster black hole" so massive that, in theory, it shouldn't exist.It's a stellar black hole — the type that forms after stars die, collapse, and explode. Researchers had previously believed that the size limit was no more than 20 times the mass of our sun because as these stars die, they lose most of their mass through explosions that expel matter and gas swept away by stellar winds.This theory has now been toppled by LB-1, the newly-discovered black hole. Located about 15,000 light years away, it has a mass 70 times greater than our sun, according to a press release from the Chinese Academy of Sciences.The findings were published by Chinese researchers in the journal Nature on Wednesday."Black holes of such mass should not even exist in our galaxy, according to most of the current models of stellar evolution," said Liu Jifeng, head of the team that made the discovery. "LB-1 is twice as massive as what we thought possible. Now theorists will have to take up the challenge of explaining its formation."Scientists are now scratching their heads at how LB-1 got so huge.The Chinese team has proposed a number of theories. LB-1's sheer size suggests that it "was not formed from the collapse of only one star," the study said -- instead, it could potentially be two smaller black holes orbiting each other.Another possibility is that it formed from a "fallback supernova." This is when a supernova -- the last stage of an exploding star -- ejects material during the explosion, which then falls back into the supernova, creating a black hole.This fallback formation is theoretically possible, but scientists have never been able to prove or observe it. If this is how LB-1 formed, then we may have "direct evidence for this process" for the first time, the study said.LB-1 is not the biggest black hole ever discovered -- but it may be the largest of its kind. There are several types of black holes, and stellar black holes like LB-1 are on the smaller side, according to NASA. Supermassive black holes are much bigger -- they can be billions of times the mass of our sun.Scientists believe supermassive black holes may be connected to the formation of galaxies, as they often exist at the center of the massive star systems -- but it is still not clear exactly how, or which form first.Stellar renaissanceStellar black holes are believed to be commonly scattered across the universe, but they are difficult to detect because they do not normally emit X-rays -- only doing so when they gobble up gas from a star that has ventured close enough. They are so elusive that scientists have only found, identified, and measured about two dozen stellar black holes, the press release said.The researchers at the Chinese Academy of Sciences tried a different approach. Instead of looking for X-rays emitted by black holes, the team looked for stars that were orbiting some invisible object, being pulled in by its gravity.Their efforts paid off -- they soon spotted a giant star eight times heavier than the sun, orbiting around what turned out to be LB-1."This discovery forces us to re-examine our models of how stellar-mass black holes form," said David Reitze, a physicist at the University of Florida. In May, Reitze's team made its own breakthrough discovery -- observing the never-before-seen collision of a neutron star and a black hole, which sent out ripples in space and time.These twin discoveries -- the collision, and now LB-1 -- indicate that scientists are reaching "a renaissance in our understanding of black hole astrophysics," said Reitze in the press release.There have been several other discoveries over the past year that have added to this renaissance. In October, researchers discovered what they believe to be a new type of black hole, smaller than the other kinds. And earlier this week, astronomers discovered a black hole that is actually helping baby stars grow instead of destroying them. 3971

(CNN) -- President Trump is giving most federal workers the gift of an extra day off this holiday season.The president issued an executive order Tuesday ordering that all executive departments and federal agencies close on Tuesday, December 24 in honor of Christmas Eve.The holidays for federal employees include Christmas Day, but not Christmas Eve.Certain employees, or "emergency employees," will have to work that day "for reasons of national security, defense, or other public need."News of an extra day off comes after Congress recently approved 12 weeks of paid parental leave for all federal employees for the first time in American history. The legislation heads to Trump's desk for his signature. 714

(KGTV) - Does a busy California building really have "Riot" buttons in its elevators?Yes.The California Dept. of Tax and Fee Administration building in Sacramento installed the buttons.The building manager says they're supposed to light up to alert riders the elevators won't go to the 1st floor in the event of a security scare, such as a riot. 353

(KGTV) — California has already received more than 1.5 million vote-by-mail ballots back with just under three weeks left until the 2020 election.At least 1,511,522 mail-in ballots have been recorded by the state, according to the California Secretary of State office. At this point ahead of the 2016 election, the state had received only 150,000 mail-in ballots.During the 2016 election, a total of 8,443,594 mail-in ballots were recorded, according to the state.RELATED: A step-by-step guide to voting by mail or in person in San Diego CountyThis year, election officials are preparing for an avalanche of ballots to travel through the postal system. California sent a mail-in ballot to every active, registered voter due to the coronavirus pandemic, totaling more than 21 million ballots.In San Diego County, as of Sept. 4, there were about 1,869,527 active, registered voters.Voters can still cast their ballot in person or drop off their ballot at an official. An official search to find the closest polling or drop off location to you is available online.New this year, voters across the state can also track their ballot online and find out when it was mailed, received, and counted.According to the San Diego Registrar of Voters' Michael Vu, voters are encouraged to return their ballots with plenty of time to make sure they are counted. Vu says voters should, "clearly mark that ballot, similar to when you’re going to a polling place with an ink pen. Black or blue is preferred."Vu says missing or mismatched signatures, meaning the signature on the ballot doesn’t match the one on file, are one of the most common reasons ballots get disqualified. The number one reason, however, is that ballots are sent back too late. Ballots must be postmarked on or before Election Day, Nov. 3, Vu says. 1810

(KGTV) - A CH-53 helicopter pilot is inspiring a younger generation at the MCAS Miramar Air Show.10News reporter Natay Holmes talked with her about the aircraft.Learn more about the MCAS Miramar Air Show here. 217

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