Black hole beginnings

In its second year of operations, Chandra was hitting its stride. Regular updates appeared talking about the telescope's investigations: X-ray emanating stars embedded in the Orion Nebula, a galaxy growing by gobbling up its neighbors, and evidence of baby stars.

The telescope also began a series of discoveries concerning black holes. It spotted evidence of a Type 2 quasar black hole emanating X-rays behind a thick sheet of material that previously hid the black hole's existence.

Later, scientists announced a possible new kind of black hole in the galaxy M82. From eight months of observations, the scientists said the black hole could represent an evolutionary stage between small black holes formed from stars, and the much more massive ones lurking in the centers of galaxies.

"The black hole in M82 packs the mass of at least 500 suns into a region about the size of the moon," NASA wrote in September 2000.

"Such a black hole would require extreme conditions for its creation, such as the collapse of a 'hyperstar' or the merger of scores of black holes."

X-ray Vision Reveals the Insides of Stars

Possible dark matter and other findings

Astronomers are on a continual hunt for "dark" matter, which is believed to be practically invisible stuff that makes most of the universe. So far, we can only detect it through its gravity.

In 2006, a team of astronomers spent more than 100 hours using Chandra to watch the galaxy cluster 1E0657-56, which contains gas from a galaxy cluster collision. Chandra's observations were combined with that of several other observatories.

Researchers examined the effect the galaxy cluster had on gravitational lensing, which is a known way that gravity distorts the light from background galaxies. Their observations of the gravity showed that normal matter and dark matter ripped apart during the galaxy collision.

While the dark matter search continues, Chandra has been used to find other missing matter. In 2010, researchers used Chandra and the European Space Agency's XMM-Newton observatory, probing a reservoir of gas resting along a wall of galaxies about 400 million light-years away from Earth.

Scientists found evidence of baryons, which are electrons, protons and other particles that compose matter found through much of our universe. The researchers suspected the gas would contain a significant amount of this matter.

While scientists continue to probe the nature of matter, Chandra continues to produce stunning pictures that also reveal the structure of the universe. These pictures include a survey of planetary nebulas and a fast-growing galaxy cluster, as well as a "superbubble" found in the Large Magellanic Cloud.

In 2013, Chandra detected a record-breaking outburst from the Milky Way's supermassive black hole, an object known as Sagittarius A*, or Sgr A*. At the time, astronomers were observing how Sgr A* would react to what was then suspected to be a cloud of gas but later determined to be a cloud surrounding a compact object. While G2 didn't produce the fireworks scientists hoped for, scientists did spot a megaflare that was 400 times brighter than the black hole's normal quiescent state, three times brighter than the previous record holder. 

"If an asteroid was torn apart, it would go around the black hole for a couple of hours – like water circling an open drain – before falling in," Fred Baganoff of the Massachusetts Institute of Technology in Cambridge, Massachusetts, said in a statement. "That's just how long we saw the brightest X-ray flare last, so that is an intriguing clue for us to consider."

Another theory suggests that the magnetic field lines within G2 became tangled as they flowed toward Sgr A*. The occasional reconfiguration of the field lines produces a bright x-ray outburst similar to magnetic flares seen on the sun.

In 2017, Chandra was one of several instruments that picked up a pulse of high-energy light from the powerful explosion caused by two merging neutron stars. Observations with the National Science Foundation's Laser Interferometer Gravitational-wave Observatory (LIGO) had spotted gravitational waves tied to the collision, encouraging scientists to hunt for signs of the explosion's aftermath.

"This is extremely exciting science," Paul Hertz, director of NASA's Astrophysics Division, said in a statement. "Now, for the first time, we've seen light and gravitational waves produced by the same event. The detection of a gravitational-wave source's light has revealed details of the event that cannot be determined from gravitational waves alone. The multiplier effect of study with many observatories is incredible."

Chandra is even helping prepare humans for voyages to other star systems. In 2018, Chandra announced the results of a decade-long study of Alpha Centauri, the closest star system to the sun. The triple star system lies just over four light-years from Earth and is the target for projects like Breakthrough Starshot, which aims to send a swarm of nanocrafts to the system in search of potential life. After observing the system, Chandra data revealed that X-ray bombardment around Alpha Centauri A is slightly better than the sun, and only slightly worse around Alpha Centauri B.

"This is very good news for Alpha Cen AB in terms of the ability of possible life on any of their planets to survive radiation bouts from the stars," Tom Ayres, a researcher at the University of Colorado Boulder, said in a statement. "Chandra shows us that life should have a fighting chance on planets around either of these stars."

Chandra's mission, originally expected to last five years and then extended to at least 10, is still going strong after more than 18 years of operations. In a 2010 interview with Space.com, Roger Brissenden, Chandra's manager and flight director, said that the instrument had enough power and propulsion systems reserves to last until "at least 2018."

"There's enough fuel for many tens of years," Brissenden said. "The 20-year mission would be within reach."

High Energy Vision: The Chandra X-ray Observatory

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