Tips on what to watch for in the night sky this month from NASA JPL:

Another night sky highlights report from the Hubble Telescope institute:

 

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Tabby’s Star is currently one of the oddest objects observed in our galaxy. Citizen scientists working in the Planet Hunters program were the first to notice that the light output of the star, which is 1300 light years from earth, was fluctuating downward in an irregular manner never seen before with similar type stars. (See posts here and here.) Subsequent research looking back at telescopic images of the star indicated that the brightness may have been falling over the past 100 years.

The star (also known as Boyajian’s Star) is named after LSU assistant professor Tabetha Boyajian and on Friday she posted on Twitter: “#TabbysStar IS DIPPING! OBSERVE!!” This led observatories around the world to aim their telescopes and radio dishes at the star to observe it in as many wavelengths as possible. She also posted a graph showing the drop in brightness:

@ajebson @NASAKepler @LCO_Global @keckobservatory @AAVSO @nexssinfo @NASA @NASAHubble @Astro_Wright @BerkeleySETI @ESO its 2% in r’ band and looks like its the start pic.twitter.com/TjJdSY2ar9

— Tabetha Boyajian (@tsboyajian) May 19, 2017

Boyajian is posting updates on Twitter and on the website Where’s the Flux? E.g. WTF Has Gone Into a Dip! | Where’s the Flux?

Currently, we are organizing and cataloging dozens of observations from multiple observers worldwide. Planned responses include photometric observations in multiple bands, spectrometry, and more exotic observations such as polarimetry. We are also continuing the monitoring with the Las Cumbres telescopes at an increased cadence (probably three or four sequences every hour),

Stay tuned for more news about this exciting event!

More about Tabby’s Star:

• Tabby’s star is dimming again, and astronomers are excited | Ars Technica
• Bizarre Star Dims Again, and Astronomers Scramble to Catch It in the Act – Scientific American
• Finally! The Galaxy’s Most Mysterious Star Is Dipping – Sky & Telescope

A new report from the NASA/ESA Hubble Space Telescope:

The final frontier of the Frontier Fields 

The NASA/ESA Hubble Telescope has peered across six billion light years of space to resolve extremely faint features of the galaxy cluster Abell 370 that have not been seen before. Imaged here in stunning detail, Abell 370 is part of the Frontier Fields programme which uses massive galaxy clusters to study the mysteries of dark matter and the very early Universe.

Six billion light-years away in the constellation Cetus (the Sea Monster), Abell 370 is made up of hundreds of galaxies [1]. Already in the mid-1980s higher-resolution images of the cluster showed that the giant luminous arc in the lower left of the image was not a curious structure within the cluster, but rather an astrophysical phenomenon: the gravitationally lensed image of a galaxy twice as far away as the cluster itself. Hubble helped show that this arc is composed of two distorted images of an ordinary spiral galaxy that just happens to lie behind the cluster.

This zoom starts with a ground-based view of the sky and zooms in on the distant galaxy cluster Abell 370, as seen by the NASA/ESA Hubble Space Telescope.  The mass of the cluster is large enough to bend the light of more distant objects along the line of sight. This creates interesting distortions, fascinating arcs and it even magnifies objects which would otherwise be to faint and tiny to be seen by Hubble. Credit: ESA/Hubble Music: Richard Hasbia “Stan Dart”

Abell 370’s enormous gravitational influence warps the shape of spacetime around it, causing the light of background galaxies to spread out along multiple paths and appear both distorted and magnified. The effect can be seen as a series of streaks and arcs curving around the centre of the image. Massive galaxy clusters can therefore act like natural telescopes, giving astronomers a close-up view of the very distant galaxies behind the cluster — a glimpse of the Universe in its infancy, only a few hundred million years after the Big Bang.

This image of Abell 370 was captured as part of the Frontier Fields programme, which used a whopping 630 hours of Hubble observing time, over 560 orbits of the Earth. Six clusters of galaxies were imaged in exquisite detail, including Abell 370 which was the very last one to be finished. An earlier image of this object  — using less observation time and therefore not recording such faint detail — was published in 2009.

During the cluster observations, Hubble also looked at six “parallel fields”, regions near the galaxy clusters which were imaged with the same exposure times as the clusters themselves. Each cluster and parallel field were imaged in infrared light by the Wide Field Camera 3 (WFC3), and in visible light by the Advanced Camera for Surveys (ACS).

This video pans across the massive galaxy cluster Abell 370, the last cluster to be observed as part of the Frontier Fields programme. The huge mass of the cluster bends the light from more distant objects, creating distorted and magnified images of them. This allows astronomers to calculate the total mass of the cluster — both normal matter and dark matter — and to investigate objects in the early Universe that would be otherwise too faint and tiny for Hubble to see. Astronomers believe this distortion is caused by dark matter that holds together the mix of galaxies and intergalactic hot gas. Credit: ESA/Hubble Music: Richard Hasbia “Stan Dart”

The Frontier Fields programme produced the deepest observations ever made of galaxy clusters and the magnified galaxies behind them. These observations are helping astronomers understand how stars and galaxies emerged out of the dark ages of the Universe, when space was dark, opaque, and filled with hydrogen.

Studying massive galaxy clusters like Abell 370 also helps with measuring the distribution of normal matter and dark matter within such clusters [heic1506]. By studying its lensing properties, astronomers have determined that Abell 370 contains two large, separate clumps of dark matter, contributing to the evidence that this massive galaxy cluster is actually the result of two smaller clusters merging together.

Now that the observations for the Frontier Fields programme are complete, astronomers can use the full dataset to explore the clusters, their gravitational lensing effects and the magnified galaxies from the early Universe in full detail.

Notes

[1] Galaxy clusters are the most massive structures in the Universe that are held together by gravity, generally thought to have formed when smaller groups of galaxies smashed into each other in ever-bigger cosmic collisions. Such clusters can contain up to 1000 galaxies, along with hot intergalactic gas that often shines brightly at X-ray wavelengths, all bound together primarily by the gravity of dark matter.

The latest report from ESO (European Southern Observatory):

VISTA Peeks Through the Small Magellanic Cloud’s Dusty Veil

The Small Magellanic Cloud galaxy is a striking feature of the southern sky even to the unaided eye. But visible-light telescopes cannot get a really clear view of what is in the galaxy because of obscuring clouds of interstellar dust. VISTA’s infrared capabilities have now allowed astronomers to see the myriad of stars in this neighbouring galaxy much more clearly than ever before. The result is this record-breaking image — the biggest infrared image ever taken of the Small Magellanic Cloud — with the whole frame filled with millions of stars.

The Small Magellanic Cloud (SMC) is a dwarf galaxy, the more petite twin of the Large Magellanic Cloud (LMC). They are two of our closest galaxy neighbours in space — the SMC lies about 200 000 light-years away, just a twelfth of the distance to the more famous Andromeda Galaxy.  Both are also rather peculiarly shaped, as a result of interactions with one another and with the Milky Way itself.

This video takes a quick look at a remarkable new image from ESO’s VISTA survey telescope at the Paranal Observatory in Chile. The huge picture shows one of our neighbouring galaxies, the Small Magellanic Cloud, in remarkable detail and in infrared light.

Their relative proximity to Earth makes the Magellanic Clouds ideal candidates for studying how stars form and evolve. However, while the distribution and history of star formation in these dwarf galaxies were known to be complex, one of the biggest obstacles to obtaining clear observations of star formation in galaxies is interstellar dust. Enormous clouds of these tiny grains scatter and absorb some of the radiation emitted from the stars — especially visible light — limiting what can be seen by telescopes here on Earth. This is known as dust extinction.

The SMC is full of dust, and the visible light emitted by its stars suffers significant extinction. Fortunately, not all electromagnetic radiation is equally affected by dust. Infrared radiation passes through interstellar dust much more easily than visible light, so by looking at the infrared light from a galaxy we can learn about the new stars forming within the clouds of dust and gas.

VISTA, the Visible and Infrared Survey Telescope, was designed to image infrared radiation. The VISTA Survey of the Magellanic Clouds (VMC) is focused on mapping the star formation history of the SMC and LMC, as well as mapping their three-dimensional structures. Millions of SMC stars have been imaged in the infrared thanks to the VMC, providing an unparalleled view almost unaffected by dust extinction.

The video sequence takes the viewer from a wide view of the southern skies deep into a small nearby galaxy, the Small Magellanic Cloud. The final close-up infrared views are from a very detailed huge image of the galaxy taken using ESO’s VISTA infrared survey telescope at the Paranal Observatory in Chile. Millions of stars and many star clusters and much more distant galaxies are visible. Credit: ESO/VISTA VMC/N. Risinger (skysurvey.org). Music: Astral electronic.

The whole frame of this massive image is filled with stars belonging to the Small Magellanic Cloud. It also includes thousands of background galaxies and several bright star clusters, including 47 Tucanae at the right of the picture, which lies much closer to the Earth than the SMC. The zoomable image will show you the SMC as you have never seen it before!

The wealth of new information in this 1.6 gigapixel image (43 223 x 38 236 pixels) has been analysed by an international team led by Stefano Rubele of the University of Padova. They have used cutting-edge stellar models to yield some surprising results.

This view compares a huge new infrared image of the Small Magellanic Cloud from ESO’s VISTA telescope to a more traditional view in visible light. By observing at longer infrared wavelengths VISTA can penetrate the dust clouds of this small neighbouring galaxy and reveal the stars much more clearly. Credit: ESO/VISTA VMC/Digitized Sky Survey 2. Music: Astral electronic. [Larger versions.]

The VMC has revealed that most of the stars within the SMC formed far more recently than those in larger neighbouring galaxies. This early result from the survey is just a taster of the new discoveries still to come, as the survey continues to fill in blind spots in our maps of the Magellanic Clouds.

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