If large stars leave behind black holes, there should be hundreds of millions of them in the universe. Black holes are not visible.
A team led by the University of California, Berkeley discovered a black hole by observing a star's light being distorted by the object's strong gravity.
The team estimates that the object's mass is between 1.6 and 4.4 times that of the sun. The UC Berkeley researchers caution that the object could be a neutron star instead of a black hole because the leftover remnant of a dead star must be heavier than 2.2 solar mass. The gravity of the stars is balanced by the internal pressure of the black hole.
The object is the first dark stellar remnant that isn'tpaired with another star.
This is the first free-floating black hole or neutron star discovered. Microlensing allows us to weigh the lonely, compact objects. I believe we have opened a new window onto these dark objects, which can't be seen without them.
Figuring out how many of these compact objects are in the Milky Way will help astronomer understand the evolution of stars, how they die, and whether any of the unseen black holes are primordial black holes.
The analysis is going to be published in The Astrophysical Journal Letters. Four other microlensing events that the team concluded were not caused by a black hole were included in the analysis. Most theorists predicted that there would be 200 million black holes in the universe.
Different conclusions from the same data.
The Space Telescope Science Institute (STScI) in Baltimore analyzed the same microlensing event and claimed that the object is closer to a black hole. The Astrophysical Journal accepted a paper about the analysis by theSTScI team.
The Microlensing Observations in Astrophysics (MOA) experiment is mounted on a 1.8 and uses a 1.3 meter telescope. The data came from a space telescope. The science program for the telescope is managed bySTScI
Both surveys caught the same object and it has two different names.
The two teams were able to determine the mass of the object and its distance from Earth thanks to the addition of Astrometric data. The team estimated that it lies between 2,280 and 6,260 light years away, in the direction of the center of the Milky Way.
It lies about 5,153 light years away from us.
Someone is looking for a needle.
They became interested in the object in 2020 after learning that the five microlensing events observed by Hubble might not have been black holes.
The abundance of black holes in the universe has been estimated to be between 10 million and 1 billion. Black holes of star size have only been found in the stars. When material from a star falls onto a black hole in a black hole, it can be seen in X-rays. These events aren't very common.
We were really interested after seeing the data. There were no black holes. Even though there should have been, that is amazing. We began to look at the data. If there were no black holes in the data, this wouldn't match our model for how many black holes there should be in the universe. Something would have to be changed in our understanding of black holes.
When she looked at the photometry and Astrometry for the five microlensing events, she was surprised that one had the characteristics of a compact object.
The main tip off was the length of the event. She showed that looking for long events was the best way to find black hole microlenses. She said that looking at all events would be like looking in a haystack. About 40% of microlensing events are likely to be black holes.
The amount of time the event lasts is a sign of how big the foreground lens is. Black holes can be the cause of long events. The duration of the brightening episode is dependent on how fast the foreground lens and background star are moving relative to each other and how big the foreground lens is. We can confirm that the foreground lens is a black hole by measuring the position of the background star.
Lu claims that the light of the background star was incredibly long-lived. It took about a year for the star to go from bright to dull.
The black hole is different from the star.
The request for more Hubble data was made by Lu and Lam in order to confirm the cause of OB110462. Ten years after the event, the change in the star's position is still visible. The fall of 2022 is when further Hubble observations of the microlens are likely to take place.
The new data showed that the black hole was probably a neutron star.
There are differences between the two teams. The UC Berkeley-led team hopes to resolve the discrepancy with more Hubble data and better analysis in the future.
We have to report all allowed solutions if we want to say that it is a black hole. Lu said that this could include both lower mass black holes and a neutron star.
It says something important if you can't believe the light curve. It tells you something important if you don't believe the position. We have to understand why one of them is incorrect. It is1-65561-65561-65561-65561-65561-65561-65561-65561-65561-65561-65561-65561-65561-65561-65561-65561-65561-65561-65561-65561-65561-65561-65561-65561-65561-65561-65561-65561-65561-65561-65561-65561-65561-65561-65561-65561-65561-65561-65561-65561-65561-65561-65561-65561-65561-65561-65561-65561-65561-65561-65561-65561-65561-65561-65561-6556 The photometry and Astrometry data come from the same physical process and must be consistent with each other. There is something missing there.
The teams estimated the object's speed. The Lu/Lam team found a slow speed. The 45 km/s speed that the team found was the result of an extra kick from the black hole that created it.
Lu believes that the team's low velocity estimate may support a new theory that black holes come from failed supernovas that don't make a bright splash in the universe or give the resulting black hole a kick.
More information: Casey Lam et al, An isolated mass gap black hole or neutron star detected with astrometric microlensing, The Astrophysical Journal Letters (2022). DOI: 10.48550/arXiv.2202.01903 Journal information: Astrophysical Journal Letters , Astrophysical Journal
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