Astronomy

The SOCIETY for POPULAR ASTRONOMY

Electronic News Bulletin No. 463 2018 February 18

GRAVITATIONAL LENS SETS NEW RECORD
University of Hawaii at Manoa

Extremely distant galaxies are mostly too faint to be seen, even by the
largest telescopes. But nature has a solution: gravitational lensing,
predicted by Einstein and observed many times by astronomers. Now, an
international team of astronomers has discovered one of the most extreme
instances of magnification by gravitational lensing. Using the Hubble
Telescope to survey a sample of huge clusters of galaxies, the team found a
distant galaxy, eMACSJ1341-QG-1, that is magnified 30 times thanks to the
distortion of space-time created by the massive 'foreground' galaxy cluster
dubbed eMACSJ1341.9-2441. The underlying physical effect of gravitational lensing was first confirmed during the solar eclipse of 1919, and can dramatically magnify images of distant celestial sources if a sufficiently massive object lies between the background source and the observers. Galaxy clusters, enormous concentrations of dark matter and hot gas surrounding hundreds or thousands of individual galaxies, all bound by the force of gravity, are valued by astronomers as powerful gravitational lenses. By magnifying the galaxies situated behind them, massive clusters act as natural telescopes that allow scientists to study faint and distant sources that would otherwise be beyond the reach of even the most powerful man-made telescopes. In the present instance, The high magnification of the image provides astronomers with a rare opportunity to investigate the stellar populations of that distant object and, ultimately, to reconstruct its undistorted shape and properties. Although similarly extreme magnifications have been observed before, the discovery sets a record for the magnification of a rare 'quiescent' background galaxy -- one that, unlike our Milky Way, is not forming new stars in giant clouds of cool gas. The team specializes in finding extremely massive clusters that act as natural telescopes and has already discovered many exciting cases of gravitational lensing. This discovery stands out, though, as the huge magnification provided by eMACSJ1341 allows us to study in detail a rare type of galaxy.

I think I understand the concept of Gravitational lensing from the above post.

Quote:

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By magnifying the galaxies situated behind them, massive clusters act as natural telescopes that allow scientists to study faint and distant sources that would otherwise be beyond the reach of even the most powerful man-made telescopes.

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This is not clear to me, how these massive clusters act as magnifying lenses.

Well, Einstein predicted this 100 year ago. But I agree, it is still unclear what he meant, as is the way it works.

A quite different kind of research:

A new study shows mankind’s reaction to alien life would be quite positive
News of extraterrestrials would likely generate upbeat attitudes.
"As technology rapidly advances, we’re making astronomical discoveries faster than ever before. Many think it’s just a matter of time before we come across extraterrestrial life and prove that we’re not alone in the universe. So let’s say it actually happens. We uncover or are approached by alien life. Now what? How does the public react? Do our defensive instincts or humble curiosities take over? New research suggests that the general population’s reaction would be quite positive."
http://www.astronomy.com/news/2018/0...quite-positive

I would agree with that conclusion, but the real test will come when we meet intelligent life. No sign of the yet.

I couldn´t agree more, DW!

Improved Hubble yardstick gives fresh evidence for new physics in the universe

Date:
February 22, 2018
Source:
NASA/Goddard Space Flight Center
Summary:
Astronomers have used NASA's Hubble Space Telescope to make the most precise measurements of the expansion rate of the universe since it was first calculated nearly a century ago. Intriguingly, the results are forcing astronomers to consider that they may be seeing evidence of something unexpected at work in the universe.
https://www.sciencedaily.com/release...0222162005.htm

Universe today https://www.universetoday.com has some interesting posts about NASA's SOHO - the Solar and Heliospheric Observatory - https://www.universetoday.com/138664...sun-from-soho/. This website has many different projects, including one when the total eclipse passed over the USA, which gave a prolonged view of solar eclipses.

This is one of the quiet successes of the study of solar eclipses.

"The Solar and Heliospheric Observatory (SOHO) is celebrating 22 years of observing the Sun, marking one complete solar magnetic cycle in the life of our star. SOHO is a joint project between NASA and the ESA and its mission is to study the internal structure of the sun, its extensive outer atmosphere, and the origin of the solar wind.

The activity cycle in the life of the Sun is based on the increase and decrease of sunspots. We’ve been watching this activity for about 250 years, but SOHO has taken that observing to a whole new level."

"Though sunspot cycles work on an 11-year period, they’re caused by deeper magnetic changes in the Sun. Over the course of 22 years, the Sun’s polarity gradually shifts. At the 11 year mark, the orientation of the Sun’s magnetic field flips between the northern and southern hemispheres. At the end of the 22 year cycle, the field has shifted back to its original orientation. SOHO has now watched that cycle in its entirety."

"SOHO is a real success story. It was launched in 1995 and was designed to operate until 1998. But it’s been so successful that its mission has been prolonged and extended several times."

An astroid will pass by Earth really close. There is no danger of it hitting Earth. See http://earthsky.org/space/asteroid-2...oon-mar-2-2018

Yes, it can be seen tomorrow.

I don't know if this is a practical joke or not but I add this post here: http://earthsky.org/space/signal-fro...tars-detected?

"By Karl Glazebrook, Swinburne University of Technology

A signal caused by the very first stars to form in the universe has been picked up by a tiny but highly specialised radio telescope in the remote Western Australian desert.

Details of the detection are revealed in a paper published February 28, 2018, in Nature, and tell us these stars formed only 180 million years after the Big Bang.

It’s potentially one of the most exciting astronomical discoveries of the decade. A second Nature paper, also published February 28, links the finding to possibly the first detected evidence that dark matter, thought to make up much of the universe, might interact with ordinary atoms."

I don´t think it is meant as a joke, DW. I read something about it in the Brazilian news. However no sources were mentioned so I couldn´t trace the information.
Your article mentions two papers published in Nature, which make a more sober approach. I reproduce both abstracts here:

1-An absorption profile centred at 78 megahertz in the sky-averaged spectrum

"Abstract
After stars formed in the early Universe, their ultraviolet light is expected, eventually, to have penetrated the primordial hydrogen gas and altered the excitation state of its 21-centimetre hyperfine line. This alteration would cause the gas to absorb photons from the cosmic microwave background, producing a spectral distortion that should be observable today at radio frequencies of less than 200 megahertz1. Here we report the detection of a flattened absorption profile in the sky-averaged radio spectrum, which is centred at a frequency of 78 megahertz and has a best-fitting full-width at half-maximum of 19 megahertz and an amplitude of 0.5 kelvin. The profile is largely consistent with expectations for the 21-centimetre signal induced by early stars; however, the best-fitting amplitude of the profile is more than a factor of two greater than the largest predictions2. This discrepancy suggests that either the primordial gas was much colder than expected or the background radiation temperature was hotter than expected. Astrophysical phenomena (such as radiation from stars and stellar remnants) are unlikely to account for this discrepancy; of the proposed extensions to the standard model of cosmology and particle physics, only cooling of the gas as a result of interactions between dark matter and baryons seems to explain the observed amplitude3. The low-frequency edge of the observed profile indicates that stars existed and had produced a background of Lyman-α photons by 180 million years after the Big Bang. The high-frequency edge indicates that the gas was heated to above the radiation temperature less than 100 million years later."

2-Possible interaction between baryons and dark-matter particles revealed by the first stars

"Abstract
The cosmic radio-frequency spectrum is expected to show a strong absorption signal corresponding to the 21-centimetre-wavelength transition of atomic hydrogen around redshift 20, which arises from Lyman-α radiation from some of the earliest stars1,2,3,4. By observing this 21-centimetre signal—either its sky-averaged spectrum5 or maps of its fluctuations, obtained using radio interferometers6,7—we can obtain information about cosmic dawn, the era when the first astrophysical sources of light were formed. The recent detection of the global 21-centimetre spectrum5 reveals a stronger absorption than the maximum predicted by existing models, at a confidence level of 3.8 standard deviations. Here we report that this absorption can be explained by the combination of radiation from the first stars and excess cooling of the cosmic gas induced by its interaction with dark matter8,9,10. Our analysis indicates that the spatial fluctuations of the 21-centimetre signal at cosmic dawn could be an order of magnitude larger than previously expected and that the dark-matter particle is no heavier than several proton masses, well below the commonly predicted mass of weakly interacting massive particles. Our analysis also confirms that dark matter is highly non-relativistic and at least moderately cold, and primordial velocities predicted by models of warm dark matter are potentially detectable. These results indicate that 21-centimetre cosmology can be used as a dark-matter probe."

Thanks for that, Danik.

THE SOCIETY FOR POPULAR ASTRONOMY

Electronic News Bulletin No. 464 2018 March 4

http://earthsky.org/earth/wildfires-forecast-US-west

My cousin in California, George Weisz, will know about this, I look forward to a brief correspondence on this.