CAA: Cuyahoga Astronomical Association

Auroral display, Knox County, Ohio, Oct. 24, 2011, by Joe Golias.

The event began, for many of us, with a flash message from SpaceWeather.com early Monday evening:

CME IMPACT: A coronal mass ejection (CME) hit Earth’s magnetic field on Oct. 24th around 1800 UT (2 pm EDT).  The impact strongly compressed our planet’s magnetosphere and may have exposed geosynchronous satellites to solar wind plasma.  Mild to moderate geomagnetic storms are possible in the hours ahead as Earth’s magnetic field continues to reverberate from the hit.  Sky watchers in Scandinavia, Canada, and northern-tier US States should be alert for auroras, especially during the hours around local midnight.  Check http://spaceweather.com for updates.

As it happened, not only were the “northern-tier US States” treated but locales as far south as Mississippi and Arkansas saw vivid displays of the northern lights. Relatively rare red auroral activity was reported commonly during the event.

CAA members Bob Pence, Steve Gallant, Chris Christie, and Susan Petsche were among the lucky ones who viewed the display over Greater Cleveland.

Member and accomplished astro-photographer Joe Golias was even more fortunate. Golias was at his dark-sky observing location in Knox County with a grand opportunity for the surprise show. He was also on-site with the right gear to record and share the sight.

Bright red aurora, a relative rarity, dominates the Knox County sky. Photo by Joe Golias.

“The auroras from my location in Knox County were visible between 7:30 PM until 2:00 AM,” said Golias. “The green aurora was present continuously throughout the night while the red rays were visible during the peak time and on an off until 2:00 AM.”

For many other views of the surprise aurora of October 24, visit SpaceWeather.com and stay alert… solar activity is already high and is rising.

Two spiral arms emerge from the gas-rich disk around SAO 206462, a young star in the constellation Lupus. Credit: NAOJ/Subaru

A new image of the disk of gas and dust around a sun-like star has spiral-arm-like structures. These features may provide clues to the presence of embedded but as-yet-unseen planets.

“Detailed computer simulations have shown us that the gravitational pull of a planet inside a circumstellar disk can perturb gas and dust, creating spiral arms. Now, for the first time, we’re seeing these features,” said Carol Grady, a National Science Foundation (NSF)-supported astronomer with Eureka Scientific, Inc.

The newly imaged disk surrounds SAO 206462, a star located about 456 light-years away in the constellation Lupus. Astronomers estimate that the system is only about 9 million years old. The gas-rich disk spans some 14 billion miles, which is more than twice the size of Pluto’s orbit in our own solar system.

“The surprise,” said Grady, “was that we caught a glimpse of this stage of planet formation. This is a relatively short-lived phase.”

A near-infrared image from the National Astronomical Observatory of Japan shows a pair of spiral features arcing along the outer disk. Theoretical models show that a single embedded planet may produce a spiral arm on each side of a disk. The structures around SAO 206462 do not form a matched pair, suggesting the presence of two unseen worlds, one for each arm. However, the research team cautions that processes unrelated to planets may also give rise to these structures.

“What we’re finding is that once these systems reach ages of a few million years, their disks begin to show a wealth of structure–rings, divots, gaps and now spiral features,” said John Wisniewski, a collaborator at the University of Washington in Seattle. “Many of these structures could be caused by planets within the disks.”

Grady’s research is part of the Strategic Exploration of Exoplanets and Disks with Subaru (SEEDS), a five-year-long near-infrared study of young stars and their surrounding dust disks using the Subaru Telescope atop Mauna Kea in Hawaii. The international consortium of researchers now includes more than 100 scientists at 25 institutions.

“These arm-like structures have been predicted by models, but have never before been seen,” said Maria Womack, program director for the division of Astronomical Sciences at NSF. “It is the first observation of spiral arms in a circumstellar disk, and an important test for models of planetary formation.”

Source: National Science Foundation news release.

Hubble Space Telescope image of galaxy cluster MACS J1206.2-0847. Credit: NASA, ESA, M. Postman (STScI) and the CLASH Survey Team

October 13 — The NASA/ESA Hubble Space Telescope has been used to make an image of galaxy cluster MACS J1206.2-0847. The apparently distorted shapes of distant galaxies in the background is caused by an invisible substance called dark matter, whose gravity bends and distorts their light rays. MACS 1206 has been observed as part of a new survey of galaxy clusters using Hubble.

Cluster MACS J1206.2-0847 (or MACS 1206 for short) is one of the first targets in a Hubble survey that will allow astronomers to construct the highly detailed dark matter maps of more galaxy clusters than ever before. These maps are being used to test previous but surprising results that suggest that dark matter is more densely packed inside clusters than some models predict. This might mean that galaxy cluster assembly began earlier than commonly thought.

The Cluster Lensing And Supernova survey with Hubble (CLASH) probes, with unparalleled precision, the distribution of dark matter in 25 massive clusters of galaxies. So far, the CLASH team has observed six of the 25 clusters.

Dark matter makes up the bulk of the Universe’s mass, yet it can only be detected by measuring how its gravity tugs on visible matter and warps the fabric of space-time like a fairground mirror so that the light from distant objects is distorted.

Galaxy clusters like MACS 1206 are perfect laboratories for studying dark matter’s gravitational effects because they are the most massive structures in the Universe to be held together by gravity. Because of their immense gravitational pull, the clusters act like giant cosmic lenses, amplifying, distorting and bending any light that passes through them — an effect known as gravitational lensing.

Lensing effects can also produce multiple images of the same distant object, as is evident in this Hubble picture. In particular, the apparent numbers and shapes of the distant galaxies far beyond a galaxy cluster become distorted as the light passes through, yielding a visible measurement of how much mass there is in the intervening cluster, and how it is distributed. The substantial lensing distortions seen are proof that the dominant mass component of the clusters is dark matter. The distortions would be far weaker if the clusters’ gravity came only from visible matter.

MACS 1206 lies four billion light-years from Earth. Hubble’s keen vision helped CLASH  astronomers to uncover 47 multiple images of 12 newly identified faraway galaxies. Finding  so many multiple images in a cluster is a unique capability of Hubble, and the CLASH survey  is optimised to find them. The new observations build on earlier work by Hubble and  ground-based telescopes.

Among the observations which complement Hubble’s is a major project using the  European Southern Observatory’s Very Large Telescope. Unlike Hubble, which is making  images of the clusters, the VLT is carrying out spectroscopic observations, where  instruments split up the galaxies’ light into their component colours letting the scientists  draw inferences about many of the properties of the cluster galaxies, including their  distance and chemical makeup.

Taking advantage of two of Hubble’s powerful cameras, the Advanced Camera for Surveys  and the Wide Field Camera 3, the CLASH survey covers a broad wavelength range, from  ultraviolet to near-infrared.

Astronomers need the diverse colors to estimate the distances to the lensed galaxies  and to study them in more detail. Hubble’s unique capabilities allow astronomers to  estimate distances to galaxies that are four times fainter than those that ground-based  telescopes can see.

The era when the first clusters formed is not precisely known, but is estimated to be at  least nine billion years ago and possibly as far back as twelve billion years ago. If most of  the clusters in the CLASH survey are found to have excessively high accumulations of dark  matter in their central cores, then it may yield new clues about the early stages of the  origin of structure in the Universe.

by Bill Murmann

Constellation Cygnus with Albireo circled at the Swan's head. Image via Stellarium by James Guilford.

During the summer, one of the best colorful double stars is Albireo, the head of the “Swan” in the constellation Cygnus. “Double Stars” was the topic for the program at our monthly meeting on Monday, September 12, and Albireo is a great example. Albireo is 380 light years away; the pair of stars is designated “Albireo A” and “Albireo B.”

Albireo A is yellow star, slightly cooler than our Sun. It has a surface temperature estimated at 7,000 degrees F., compared to the Sun’s 9,000-degree F. surface temperature.

Its companion, Albireo B, is a hot, blue star with an estimated surface temperature of about 23,000 degrees F. It also rotates very fast — at about 560,000 MPH.

When we are looking at Albireo, we are actually seeing three stars. Albireo A is, itself, a close binary star. Most of us, however, can’t split this pair with our telescopes. It takes a minimum 20-inch telescope under really good sky conditions to split Albireo A. Paul Leopold with his 20-inch scope is probably the only CAA member who has a chance to see all three stars in Albireo.