A preview from NASA JPL of night sky highlights for November:
Catch planet pairs and watch the moon pass stellar superstars! See Jupiter and Venus at dawn, the Moon shine near star clusters, and meteor activity all month long. For more astronomy events near you, check out https://nightsky.jpl.nasa.gov/ .
Another preview from the Hobble Telescope Observatory:
In November the northern hemisphere is treated to views of Pisces, Aries, Triangulum, and the Leonid Meteor Shower.
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Here are details from NASA about that object said to be passing by from beyond our solar system:
Small Asteroid or Comet ‘Visits’ from Beyond the Solar System
A small, recently discovered asteroid — or perhaps a comet — appears to have originated from outside the solar system, coming from somewhere else in our galaxy. If so, it would be the first “interstellar object” to be observed and confirmed by astronomers.
This unusual object – for now designated A/2017 U1 – is less than a quarter-mile (400 meters) in diameter and is moving remarkably fast. Astronomers are urgently working to point telescopes around the world and in space at this notable object. Once these data are obtained and analyzed, astronomers may know more about the origin and possibly composition of the object.
A/2017 U1 was discovered Oct. 19 by the University of Hawaii’s Pan-STARRS 1 telescope on Haleakala, Hawaii, during the course of its nightly search for near-Earth objects for NASA. Rob Weryk, a postdoctoral researcher at the University of Hawaii Institute for Astronomy (IfA), was first to identify the moving object and submit it to the Minor Planet Center. Weryk subsequently searched the Pan-STARRS image archive and found it also was in images taken the previous night, but was not initially identified by the moving object processing.
Weryk immediately realized this was an unusual object.
“Its motion could not be explained using either a normal solar system asteroid or comet orbit,” he said. Weryk contacted IfA graduate Marco Micheli, who had the same realization using his own follow-up images taken at the European Space Agency’s telescope on Tenerife in the Canary Islands. But with the combined data, everything made sense. Said Weryk, “This object came from outside our solar system.”
[Davide Farnocchia, a scientist at NASA’s Center for Near-Earth Object Studies (CNEOS) at the agency’s Jet Propulsion Laboratory in Pasadena, California, said, ]
“This is the most extreme orbit I have ever seen,” … “It is going extremely fast and on such a trajectory that we can say with confidence that this object is on its way out of the solar system and not coming back.”
The CNEOS team plotted the object’s current trajectory and even looked into its future. A/2017 U1 came from the direction of the constellation Lyra, cruising through interstellar space at a brisk clip of 15.8 miles (25.5 kilometers) per second.
The object approached our solar system from almost directly “above” the ecliptic, the approximate plane in space where the planets and most asteroids orbit the Sun, so it did not have any close encounters with the eight major planets during its plunge toward the Sun. On Sept. 2, the small body crossed under the ecliptic plane just inside of Mercury’s orbit and then made its closest approach to the Sun on Sept. 9. Pulled by the Sun’s gravity, the object made a hairpin turn under our solar system, passing under Earth’s orbit on Oct. 14 at a distance of about 15 million miles (24 million kilometers) — about 60 times the distance to the Moon. It has now shot back up above the plane of the planets and, travelling at 27 miles per second (44 kilometers per second) with respect to the Sun, the object is speeding toward the constellation Pegasus.
“We have long suspected that these objects should exist, because during the process of planet formation a lot of material should be ejected from planetary systems. What’s most surprising is that we’ve never seen interstellar objects pass through before,” said Karen Meech, an astronomer at the IfA specializing in small bodies and their connection to solar system formation.
The small body has been assigned the temporary designation A/2017 U1 by the Minor Planet Center (MPC) in Cambridge, Massachusetts, where all observations on small bodies in our solar system — and now those just passing through — are collected. Said MPC Director Matt Holman, “This kind of discovery demonstrates the great scientific value of continual wide-field surveys of the sky, coupled with intensive follow-up observations, to find things we wouldn’t otherwise know are there.”
Since this is the first object of its type ever discovered, rules for naming this type of object will need to be established by the International Astronomical Union.
“We have been waiting for this day for decades,” said CNEOS Manager Paul Chodas. “It’s long been theorized that such objects exist — asteroids or comets moving around between the stars and occasionally passing through our solar system — but this is the first such detection. So far, everything indicates this is likely an interstellar object, but more data would help to confirm it.”
The Panoramic Survey Telescope and Rapid Response System (Pan-STARRS) is a wide-field survey observatory operated by the University of Hawaii Institute for Astronomy. The Minor Planet Center is hosted by the Harvard-Smithsonian Center for Astrophysics and is a sub-node of NASA’s Planetary Data System Small Bodies Node at the University of Maryland (http://www.minorplanetcenter.net/ ). JPL hosts the Center for Near-Earth Object Studies (CNEOS). All are projects of NASA’s Near-Earth Object Observations Program, and elements of the agency’s Planetary Defense Coordination Office within NASA’s Science Mission Directorate.
More information about asteroids and near-Earth objects can be found at:
For more information about NASA’s Planetary Defense Coordination Office, visit: www.nasa.gov/planetarydefense
For asteroid and comet news and updates, follow AsteroidWatch on Twitter: twitter.com/AsteroidWatch
A new report from the Hubble Space Telescope collaboration:
Hubble discovers “wobbling galaxies”
Observations may hint at nature of dark matter
Using the NASA/ESA Hubble Space Telescope, astronomers have discovered that the brightest galaxies within galaxy clusters “wobble” relative to the cluster’s centre of mass. This unexpected result is inconsistent with predictions made by the current standard model of dark matter. With further analysis it may provide insights into the nature of dark matter, perhaps even indicating that new physics is at work.
This video pans over NASA/ESA Hubble Space Telescope observations of the galaxy cluster Abell S1063, which were made as part of the Frontier Fields programme. The many galaxies within the cluster become clearly visible, as well as the background galaxies, enlarged by gravitational lensing.
Dark matter constitutes just over 25 percent of all matter in the Universe but cannot be directly observed, making it one of the biggest mysteries in modern astronomy. Invisible halos of elusive dark matter enclose galaxies and galaxy clusters alike. The latter are massive groupings of up to a thousand galaxies immersed in hot intergalactic gas. Such clusters have very dense cores, each containing a massive galaxy called the “brightest cluster galaxy” (BCG).
This video pans across a giant cluster of elliptical galaxies which contains so much mass that its gravity bends light beams. This means that for very distant galaxies in the background, the cluster acts as a sort of magnifying glass, bending the path of the distant object’s light towards Hubble. These gravitational lenses are one tool that astronomers can use to extend Hubble’s vision beyond its normal range.
But now, a team of Swiss, French, and British astronomers have analysed ten galaxy clusters observed with the NASA/ESA Hubble Space Telescope, and found that their BCGs are not fixed at the centre as expected [1].
“We found that the BCGs wobble around centre of the halos,” explains David Harvey, astronomer at EPFL, Switzerland, and lead author of the paper. “This indicates that, rather than a dense region in the centre of the galaxy cluster, as predicted by the cold dark matter model, there is a much shallower central density. This is a striking signal of exotic forms of dark matter right at the heart of galaxy clusters.”
The wobbling of the BCGs could only be analysed as the galaxy clusters studied also act as gravitational lenses. They are so massive that they warp spacetime enough to distort light from more distant objects behind them. This effect, called strong gravitational lensing, can be used to make a map of the dark matter associated with the cluster, enabling astronomers to work out the exact position of the centre of mass and then measure the offset of the BCG from this centre.
If this “wobbling” is not an unknown astrophysical phenomenon and in fact the result of the behaviour of dark matter, then it is inconsistent with the standard model of dark matter and can only be explained if dark matter particles can interact with each other — a strong contradiction to the current understanding of dark matter. This may indicate that new fundamental physics is required to solve the mystery of dark matter.
Co-author Frederic Courbin, also at EPFL, concludes:
“We’re looking forward to larger surveys — such as the Euclid survey — that will extend our dataset. Then we can determine whether the wobbling of BGCs is the result of a novel astrophysical phenomenon or new fundamental physics. Both of which would be exciting!”
This video pans across galaxy cluster MACS J1206.2-0847 (or MACS 1206 for short). The cluster has been observed by Hubble as part of CLASH (Cluster Lensing and Supernova survey with Hubble), a major programme to observe galaxy clusters whose gravity bends and distorts light passing through them.
Notes
[1] The study was performed using archive data from Hubble. The observations were originally made for the CLASH and LoCuSS surveys.
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A new report from ESO (European Southern Observatory):
Captured using the exceptional sky-surveying abilities of the VLT Survey Telescope (VST) at ESO’s Paranal Observatory in Chile, this deep view reveals the secrets of the luminous members of the Fornax Cluster, one of the richest and closest galaxy clusters to the Milky Way. This 2.3-gigapixel image is one of the largest images ever released by ESO.
Perhaps the most fascinating member of the cluster is NGC 1316, a galaxy that has experienced a dynamic history, being formed by the merger of multiple smaller galaxies. The gravitational distortions of the galaxy’s adventurous past have left their mark on its lenticular structure [1]. Large ripples, loops and arcs embedded in the starry outer envelope were first observed in the 1970s, and they remain an active field of study for contemporary astronomers, who use the latest telescope technology to observe the finer details of NGC 1316’s unusual structure through a combination of imaging and modelling.
The mergers that formed NGC 1316 led to an influx of gas, which fuels an exotic astrophysical object at its centre: a supermassive black hole with a mass roughly 150 million times that of the Sun. As it accretes mass from its surroundings, this cosmic monster produces immensely powerful jets of high-energy particles , that in turn give rise to the characteristic lobes of emission seen at radio wavelengths, making NGC 1316 the fourth-brightest radio source in the sky [2].
NGC 1316 has also been host to four recorded type Ia supernovae, which are vitally important astrophysical events for astronomers. Since type Ia supernovae have a very clearly defined brightness [3], they can be used to measure the distance to the host galaxy; in this case, 60 million light-years. These “standard candles” are much sought-after by astronomers, as they are an excellent tool to reliably measure the distance to remote objects. In fact, they played a key role in the groundbreaking discovery that our Universe is expanding at an accelerating rate.
Notes
[1] Lenticular or “lens-shaped” galaxies are an intermediate form between diffuse elliptical galaxies and the better-known spiral galaxies such as the Milky Way.
[2] As this radio source is the brightest in the constellation of Fornax it is also known as Fornax A.
[3] Type Ia Supernovae occur when an accreting white dwarf in a binary star system slowly gains mass from its companion until it reaches a limit that triggers the nuclear fusion of carbon. In a brief period of time, a chain reaction is initiated that eventually ends in a huge release of energy: a supernova explosion. The supernova always occurs at a specific mass, known as the Chandrasekhar limit, and produces an almost identical explosion each time. The similarity of type Ia supernovae allow astronomers to use the cataclysmic events to measure distance.
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An announcement from Hubble Space Telescope observatory:
Hubble observes source of gravitational waves for the first time
On 17 August 2017 the Laser Interferometer Gravitational-Wave Observatory (LIGO) and the Virgo Interferometer both alerted astronomical observers all over the globe about the detection of a gravitational wave event named GW170817 [1]. About two seconds after the detection of the gravitational wave, ESA’s INTEGRAL telescope and NASA’s Fermi Gamma-ray Space Telescope observed a short gamma-ray burst in the same direction.
In the night following the initial discovery, a fleet of telescopes started their hunt to locate the source of the event. Astronomers found it in the lenticular galaxy NGC 4993, about 130 million light-years away. A point of light was shining where nothing was visible before and this set off one of the largest multi-telescope observing campaigns ever — among these telescopes was the NASA/ESA Hubble Space Telescope [2].
“Once I saw that there had been a trigger from LIGO and Virgo at the same time as a gamma-ray burst I was blown away,” recalls Andrew Levan of the University of Warwick, who led the Hubble team that obtained the first observations. “When I realised that it looked like neutron stars were involved, I was even more amazed. We’ve been waiting a long time for an opportunity like this!”
Hubble captured images of the galaxy in visible and infrared light, witnessing a new bright object within NGC 4993 that was brighter than a nova but fainter than a supernova. The images showed that the object faded noticeably over the six days of the Hubble observations. Using Hubble’s spectroscopic capabilities the teams also found indications of material being ejected by the kilonova as fast as one-fifth of the speed of light.
“It was surprising just how closely the behaviour of the kilonova matched the predictions,” said Nial Tanvir, professor at the University of Leicester and leader of another Hubble observing team. “It looked nothing like known supernovae, which this object could have been, and so confidence was soon very high that this was the real deal.”
Connecting kilonovae and short gamma-ray bursts to neutron star mergers has so far been difficult, but the multitude of detailed observations following the detection of the gravitational wave event GW170817 has now finally verified these connections.
“The spectrum of the kilonova looked exactly like how theoretical physicists had predicted the outcome of the merger of two neutron stars would appear,” says Levan. “It ties this object to the gravitational wave source beyond all reasonable doubt.”
The infrared spectra taken with Hubble also showed several broad bumps and wiggles that signal the formation of some of the heaviest elements in nature. These observations may help solve another long-standing question in astronomy: the origin of heavy chemical elements, like gold and platinum [5]. In the merger of two neutron stars, the conditions appear just right for their production.
The implications of these observations are immense. As Tanvir explains:
“This discovery has opened up a new approach to astronomical research, where we combine information from both electromagnetic light and from gravitational waves. We call this multi-messenger astronomy — but until now it has just been a dream!”
Levan concludes:
“Now, astronomers won’t just look at the light from an object, as we’ve done for hundreds of years, but also listen to it. Gravitational waves provide us with complementary information from objects which are very hard to study using only electromagnetic waves. So pairing gravitational waves with electromagnetic radiation will help astronomers understand some of the most extreme events in the Universe.”
Notes
[1] The ripples in spacetime known as gravitational waves are created by moving masses, but only the most intense waves, created by rapid speed changes of very massive objects, can be detected by the current generation of detectors. Gravitational waves detectable from Earth are generated by collisions of massive objects, such as when two black holes or neutron stars merge.
[2] Next to Hubble, ESO’s Very Large Telescope, ESO’s New Technology Telescope, ESO’s VLT Survey Telescope, the MPG/ESO 2.2-metre telescope, the Atacama Large Millimeter/submillimeter Array, the Visible and Infrared Survey Telescope for Astronomy, the Rapid Eye Mount (REM) telescope, the Swope Telescope, the LCO .4-meter telescope, the American DECcam, and the Pan-STAARS survey all helped to identify and observe the event and its after-effects over a wide range of wavelengths.
[3] A neutron star forms when the core of a massive star (above eight times the mass of the Sun) collapses. This process is so violent that it crushes protons and electrons together to form subatomic particles called neutrons. They are supported against further collapse only by neutron degeneracy pressure. This makes neutron stars the smallest and densest stars known.
[4] In 2013 astronomers published results on the evidence for a kilonova, associated with a short gamma-ray burst. The observations in 2013 were far less conclusive, and hence more controversial, than the new results.
[5] These observations pin down the formation of elements heavier than iron through nuclear reactions within high-density stellar objects, known as r-process nucleosynthesis, something which was only theorised before.
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