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Remnants of a supernova

Scientists at the Kitt Peak National Observatory in Arizona have spotted a half-burnt white dwarf star hurtling across the galaxy. They think the unique star, described Thursday in the journal Science, was launched by an exploding supernova that didn't entirely destroy it. If confirmed, it would be the first direct evidence of these unique supernovae.

Why it matters: Recently, researchers discovered a type of dim supernova. These mini-novas are thought to be formed when a white dwarf partially explodes. If that is what sent this star flying, it could confirm that theory.

What happened: Once small or medium-mass stars (like our own sun, stop using hydrogen) they expand to red giants. Red giants normally fuse carbon, but if they don't have enough mass to do that, carbon and oxygen will build up in their cores and eventually the Earth-sized ultra-dense white dwarves are all of the star that remains.

Getting explosive: It's thought that white dwarf stars can only support so much mass because of their unique chemistry. Once they pass an upper mass limit, they can explode in a particular type of supernova (type 1a). Some scientists think another, dimmer type of supernova called a type 1ax starts the same way, but only ruptures part of the star. It's possible that's how LP 40-365 began its journey.

What they know: The unusual speed of LP 40-365 is the first clue: it's traveling really fast, fast enough that it could escape the gravitational pull of our galaxy. LP 40-365 is also fairly light, like part of it burned away in a supernova. Finally, the researchers looked at the chemical composition of the star and found that its atmosphere contained elements like aluminum and silicon, both of which scientists expect to show up in white dwarfs ejected by this type of galactic explosion.

Go deeper

Updated 1 hour ago - Politics & Policy

In photos: The Biden and Harris inauguration

President Biden and first lady Jill Biden watch a fireworks show on the National Mall from the Truman Balcony at the White House on Wednesday night. Photo: Chip Somodevilla/Getty Images

President Biden signed his first executive orders into law from the Oval Office on Wednesday evening after walking in a brief inaugural parade to the White House with First Lady Jill Biden and members of their family. He was inaugurated with Vice President Kamala Harris at the U.S. Capitol on Wednesday morning.

Why it matters: Many of Biden's day one actions immediately reverse key Trump administration policies, including rejoining the Paris Agreement and the World Health Organization, launching a racial equity initiative and reversing the Muslim travel ban.

Republicans pledge to set aside differences and work with Biden

President Biden speaks to Sen. Mitch McConnell after being sworn in at the West Front of the U.S. Capitol on Wednesday. Photo: Erin Schaff-Pool/Getty Images

Several Republicans praised President Biden's calls for unity during his inaugural address on Wednesday and pledged to work together for the benefit of the American people.

Why it matters: The Democrats only have a slim majority in the Senate and Biden will likely need to work with the GOP to pass his legislative agenda.

The Biden protection plan

Joe Biden announces his first run for the presidency in June 1987. Photo: Howard L. Sachs/CNP/Getty Images

The Joe Biden who became the 46th president on Wednesday isn't the same blabbermouth who failed in 1988 and 2008.

Why it matters: Biden now heeds guidance about staying on task with speeches and no longer worries a gaffe or two will cost him an election. His staff also limits the places where he speaks freely and off the cuff. This Biden protective bubble will only tighten in the months ahead, aides tell Axios.