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Photo: NASA/ESA

A large cluster of stars 19,000 light-years from Earth harbors something strange: Within the cluster, a neutron star left over after a supernova explosion orbits a star not too different from our Sun.

The big picture: The Chandra observatory has been observing that star system — known as Terzan 5 CX1 — for more than a decade, and in that time, Terzan 5 CX1 has gone from looking like one type of star system to another and back again.

  • As that neutron star orbits the other in the pair, its immense gravity pulls material from the companion star, forming a disk around the neutron star.
  • All that material falling in on the neutron star makes it spin quickly, blowing away any extra material encircling the star and transforming it into what's known as a millisecond pulsar.

Yes, but: Chandra found this star system has gone from behaving like a more typical binary to a millisecond pulsar and then back again.

  • It's not yet clear why the pair has done this dance multiple times, but scientists expect this is a phase in the evolution of these types of star systems.

Go deeper: Space tourism gets ready for launch

Go deeper

Dion Rabouin, author of Markets
10 mins ago - Economy & Business

Janet Yellen said all the right things to reassure the markets

Illustration: Aïda Amer/Axios

Treasury Secretary nominee and former Fed chair Janet Yellen's confirmation hearing before the Senate Finance Committee on Tuesday showed markets just what they can expect from the administration of President-elect Joe Biden: more of what they got under President Trump — at least for now.

What it means: Investors and big companies reaped the benefits of ultralow U.S. interest rates and low taxes for most of Trump's term as well as significant increases in government spending, even before the coronavirus pandemic.

Updated 44 mins ago - Politics & Policy

Biden to sign 15 executive actions on Day One

President-elect Joe Biden. Photo: SAUL LOEB/AFP via Getty Images

President-elect Joe Biden is expected to sign 15 executive actions upon taking office Wednesday, immediately reversing key Trump administration policies.

Why it matters: The 15 actions — aimed at issues like climate change and immigration — mark more drastic immediate steps compared with the two day-one actions from Biden's four predecessors combined, according to incoming White House press secretary Jen Psaki.

Mike Allen, author of AM
44 mins ago - Politics & Policy

The Swamp wins

President Trump on Jan. 28, 2017, with two aides he later pardoned — national security adviser Michael Flynn and strategist Steve Bannon. Photo: Drew Angerer/Getty Images

It was 12:50 a.m. on Inauguration Day when President Trump announced 143 pardons and commutations — including a pardon for Steve Bannon. 17 minutes later, the White House released an executive order that said it all about his failure to "drain the Swamp," as he'd promised in the '16 campaign.

Driving the news: Trump revoked an executive order, signed eight days after he took office, that limits his appointees' lobbying for five years after leaving the administration.