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Illustration: Eniola Odetunde/Axios

Astronomers have found indirect evidence of a new type of black hole, and they're now making advances toward seeing one for the first time.

Why it matters: Known as intermediate-mass black holes, these mysterious objects could be the key to unlocking how galaxies evolved, revealing more about why our universe looks the way it does.

The big picture: Black holes are an extreme laboratory by which sweeping theories can be put to the test.

  • They are where the laws of cosmology, general relativity and quantum physics that govern the largest and smallest processes in the universe combine.
  • If there is another type of black hole out there that astronomers have yet to discover, it will play a critical role in piecing together how our universe evolved, experts say.

Details: Scientists think intermediate-mass black holes may exist, but it's not clear how they form or where exactly they might be hiding today.

  • These types of black holes — which are thought to be about 100–100,000 times the mass of the Sun — are too large to have formed during the death of a star but too small to be considered supermassive black holes like the one found in the center of the Milky Way.
"If you have a small and a large, it's weird to just not have the medium."
— NASA astronomer Varoujan Gorjian told Axios

Where it stands: Astronomers have found dozens of possible intermediate-mass black holes, yet none have been confirmed.

  • The LIGO and Virgo detectors are sensitive enough to pick up on gravitational waves sent out during the collision of two intermediate-mass black holes.
  • Astronomers also hope that X-ray observatories could detect how these black holes might affect gas, dust and other objects around them, however, the light emitted during feeding frenzies may not be quite luminous enough to see from Earth with our current tools.
  • Gravitational waves "would give you the smoking gun, that direct measurement of the mass of these objects," LIGO's Salvatore Vitale told Axios.

Yes, but: If they do collide, intermediate-mass black holes likely produce strong gravitational waves at a frequency that competes with seismic activities on Earth — like cars driving by or waves crashing on the shore — making them harder for LIGO and Virgo to distinguish.

What's next: The European Space Agency's LISA mission — expected to launch in the mid-2030s — will be able to measure mergers between intermediate-mass black holes even in the distant universe, hopefully giving scientists an answer to the mystery once and for all.

Go deeper: Event Horizon Telescope hopes to produce first-ever moving image of a black hole

Go deeper

3 mins ago - World

First look: Jill Biden’s troops trip

First lady Jill Biden speaks last week at the White House. Photo: Olivier Douliery/AFP via Getty Images

First lady Jill Biden on Monday will visit the military base that's home to pilots and aircrews who helped conduct the airlift out of Kabul to thank the service members and their families for their support in ending the 20-year war in Afghanistan.

Why it matters: When she stops at the crews' home at Joint Base Charleston in South Carolina, the first lady will be their most high-profile member from the Biden administration since the airlift ended on Aug. 31.

Pelosi expects “billionaire’s tax” to pay for Biden social spending

Photo: Yasin Ozturk/Anadolu Agency via Getty Images

House Speaker Nancy Pelosi (D-Calif.) said Sunday she expects the chamber to pass the bipartisan infrastructure plan by week’s end, and alternatives to corporate tax hikes and a “billionaires tax” will be used to finance President Biden’s promised expansion to the social safety net.

Why it matters: Pelosi’s comments come as House and Senate leaders try to wrap up a deal. What will get cut — and how the remainder will be paid — are linchpins to a final agreement.

Dan Primack, author of Pro Rata
5 mins ago - Axios on HBO

FTX CEO Sam Bankman-Fried mystified by value of NFTs

Crypto exchange FTX, valued last week at $25 billion, recently launched an NFT marketplace by selling an image of the word "Test" for $270,000.

  • FTX founder and CEO Sam Bankman-Fried tells "Axios on HBO" that he doesn't quite understand the appeal, but adds that he doesn't personally appreciate many visual arts.