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Using various space telescopes, an international team of astronomers have observed a recently detected luminous quasar known as SMSS J114447.77–430859.3, or J1144 for short. Results of the observational campaign, available in the July 2023 edition of Monthly Notices of the Royal Astronomical Society, shed more light on the properties of this source.

Quasars, or quasi-stellar objects (QSOs) are active galactic nuclei (AGN) of very high luminosity, emitting electromagnetic radiation observable in radio, infrared, visible, ultraviolet and X-ray wavelengths. They are among the brightest and most distant objects in the known universe, and serve as fundamental tools for numerous studies in astrophysics as well as cosmology. For instance, quasars have been used to investigate the large-scale structure of the universe and the era of reionization. They also improved our understanding of the dynamics of supermassive black holes and the intergalactic medium.

J1144 was detected in June 2022 at a redshift of 0.83. It has a bolometric luminosity of about 470 quattuordecillion erg/s, which makes it the most luminous quasar over the last 9 billion years of cosmic history. It is also the optically brightest (unbeamed) quasar at a redshift greater than 0.4.

In a distant star system, a sunlike star orbits an invisible object that may be the first example of a ‘boson star’ made of dark matter, new research suggests.

Perspective from a very-educated layman. Er, laywoman.

This is Hello, Computer, a series of interviews carried out in 2023 at a time when artificial intelligence appears to be going everywhere, all at once.

Continue reading “Hello, Computer — Sabine Hossenfelder — A.I. going mainstream” »

Black holes have always been fascinating to scientists and the general public alike as even light can’t escape their gravitational pull.

This year marks the 100th anniversary of Edwin Hubble’s observation of a pulsating star called a Cepheid variable in the Andromeda nebula. The star was surprisingly faint, implying that it was very far away and that Andromeda must be a separate galaxy—the first evidence that our Milky Way is not alone. Hubble went on to uncover other galaxies and found that they were all moving away from us—a cosmic expansion characterized by the so-called Hubble constant. Astronomers have now used another star, an exploding supernova whose light was bent as it traveled to Earth, to probe the expansion [1]. By determining a time delay between different images of the supernova, the team has recovered a value of the Hubble constant that is lower than estimates based on Cepheids and on other distance markers. However, the error bars are large for the new measurement, so astronomers will need more observations to make lensed supernovae a precision speed check on cosmic expansion.

A lensed supernova is created by the light-bending power of gravity. When a supernova is behind a galaxy, relative to Earth, the light from the exploding star gets curved around the galaxy by the galaxy’s gravity. This action both distorts the star’s image and magnifies it, just like a magnifying glass. Sometimes this lensing can produce multiple images of the star, with each appearing at a different point in the sky. The light from such a set of images travels to Earth along different paths, and so arrives at Earth at different times. In 1964, the astronomer Sjur Refsdal proposed using the time delays to measure the Hubble constant. But detecting a multi-imaged supernova has proved tricky.

Luck finally came 50 years after Refsdal’s proposal. In a Hubble space telescope image from December 2014, Patrick Kelly, then at the University of California, Berkeley, and now at the University of Minnesota, spotted four lensed images of the same supernova [2]. The team was unable to determine the exact time delays between these images, but from previous observations of this part of the sky, Kelly and his colleagues predicted that a fifth image was on the way. This expectation was based on the spotted supernova sitting behind a galaxy cluster, rather than a single galaxy, so the supernova light had multiple paths to reach Earth. The astronomers kept a steady watch, and sure enough the fifth image appeared in December 2015, roughly 376 days after the other four images. This long time delay, which was caused by the cluster’s large mass density, was a boon to the cosmic expansion measurement.

It says our world arose from the explosion of singularity or a point in space-time where energy, density, and mass go to infinity, and any dimension goes to zero. It’s a point where there’s no space, time, or matter.

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What we do know is that there is some mysterious force at work attracting and holding galaxies together, while dark energy is accelerating the universe at the same time…but neither one of these mysterious particles has been detected.

But now some scientists believe that dark matter might be swirling around the edges of black holes, and other physicists believe they have found dark energy right here on Earth, and some say dark energy might not be real after all. Could it be true? Get ready to find out the answers to this and more!

When stars like our Sun die, they tend to go out with a whimper and not a bang – unless they happen to be part of a binary (two) star system that could give rise to a supernova explosion.

Now, for the first time, astronomers have spotted the radio signature of just such an event in a galaxy more than 400 million light-years away. The finding, published today in Nature, holds tantalizing clues as to what the companion star must have been like.

Dark matter, matter in the universe that does not emit, absorb or reflect light, cannot be directly detected using conventional telescopes or other imaging technologies. Astrophysicists have thus been trying to identify alternative methods to detect dark matter for decades.

Researchers at Tsinghua University, the Purple Mountain Observatory and Peking University recently carried out a study exploring the possibility of directly detecting dark photons, prominent dark matter candidates, using radio telescopes. Their paper, published in Physical Review Letters, could inform future searches for dark photons, which are hypothetical particles that would carry a force in dark matter, similarly to how photons carry electromagnetism in normal matter.

“Our previous work studied the conversion of dark photons into photons in the solar corona,” Haipeng An, one of the researchers who carried out the study, told Phys.org.