Exploring the Galactic Center

The center of our Milky Way galaxy is a mysterious place. Not only is it thousands of light-years away, it’s also cloaked in so much dust that most stars within are rendered invisible. Harvard researchers are proposing a new way to clear the fog and spot stars hiding there. They suggest looking for radio waves coming from supersonic stars.

“There’s a lot we don’t know about the galactic center, and a lot we want to learn,” says lead author Idan Ginsburg of the Harvard-Smithsonian Center for Astrophysics (CfA). “Using this technique, we think we can find stars that no one has seen before.”

The long path from the center of our galaxy to Earth is so choked with dust that out of every trillion photons of visible light coming our way, only one photon will reach our telescopes. Radio waves, from a different part of the electromagnetic spectrum, have lower energies and longer wavelengths. They can pass through the dust unimpeded.

On their own, stars aren’t bright enough in the radio for us to detect them at such distances. However, if a star is traveling through gas faster than the speed of sound, the situation changes. Material blowing off of the star as a stellar wind can plow into the interstellar gases and create a shock wave. And through a process called synchrotron radiation, electrons accelerated by that shock wave produce radio emission that we could potentially detect.

“In a sense, we’re looking for the cosmic equivalent of a sonic boom from an airplane,” explains Ginsburg.

To create a shock wave, the star would have to be moving at a speed of thousands of miles per second. This is possible in the galactic center since the stars there are influenced by the strong gravity of a supermassive black hole. When an orbiting star reaches its closest approach to the black hole, it can easily acquire the required speed.

The researchers suggest looking for this effect from one already known star called S2. This star, which is hot and bright enough to be seen in the infrared despite all the dust, will make its closest approach to the Galactic center in late 2017 or early 2018. When it does, radio astronomers can target it to look for radio emission from its shock wave.

“S2 will be our litmus test. If it’s seen in the radio, then potentially we can use this method to find smaller and fainter stars – stars that can’t be seen any other way,” says co-author Avi Loeb of the CfA.

This work is reported in a paper authored by Idan Ginsburg, Xiawei Wang, Avi Loeb, and Ofer Cohen (CfA). It has been accepted for publication in the Monthly Notices of the Royal Astronomical Society.

Headquartered in Cambridge, Mass., the Harvard-Smithsonian Center for Astrophysics (CfA) is a joint collaboration between the Smithsonian Astrophysical Observatory and the Harvard College Observatory. CfA scientists, organized into six research divisions, study the origin, evolution and ultimate fate of the universe.

– See more at: https://www.cfa.harvard.edu/news/2015-19#sthash.Clt874mE.dpuf

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No Asteroid Impact Expected

meteorshowerThis would have been more fun at the end of October.

NASA: There is No Asteroid Threatening Earth

Numerous recent blogs and web postings are erroneously claiming that an asteroid will impact Earth, sometime between Sept. 15 and 28, 2015. On one of those dates, as rumors go, there will be an impact — “evidently” near Puerto Rico — causing wanton destruction to the Atlantic and Gulf coasts of the United States and Mexico, as well as Central and South America.

That’s the rumor that has gone viral — now here are the facts.

“There is no scientific basis — not one shred of evidence — that an asteroid or any other celestial object will impact Earth on those dates,” said Paul Chodas, manager of NASA’s Near-Earth Object office at the Jet Propulsion Laboratory in Pasadena, California.

In fact, NASA’s Near-Earth Object Observations Program says there have been no asteroids or comets observed that would impact Earth anytime in the foreseeable future.  All known Potentially Hazardous Asteroids have less than a 0.01% chance of impacting Earth in the next 100 years.

The Near-Earth Object office at JPL is a key group involved with the international collaboration of astronomers and scientists who keep watch on the sky with their telescopes, looking for asteroids that could do harm to our planet and predicting their paths through space for the foreseeable future. If there were any observations on anything headed our way, Chodas and his colleagues would know about it.

“If there were any object large enough to do that type of destruction in September, we would have seen something of it by now,” he stated.

Another thing Chodas and his team do know — this isn’t the first time a wild, unsubstantiated claim of a celestial object about to impact Earth has been made, and unfortunately, it probably won’t be the last.  It seems to be a perennial favorite of the World Wide Web. 

In 2011 there were rumors about the so-called “doomsday” comet Elenin, which never posed any danger of harming Earth and broke up into a stream of small debris out in space. Then there were Internet assertions surrounding the end of the Mayan calendar on Dec. 21, 2012, insisting the world would end with a large asteroid impact. And just this year, asteroids 2004 BL86 and 2014 YB35 were said to be on dangerous near-Earth trajectories, but their flybys of our planet in January and March went without incident — just as NASA said they would.

“Again, there is no existing evidence that an asteroid or any other celestial object is on a trajectory that will impact Earth,” said Chodas. “In fact, not a single one of the known objects has any credible chance of hitting our planet over the next century.”

NASA detects, tracks and characterizes asteroids and comets passing 30 million miles of Earth using both ground- and space-based telescopes. The Near-Earth Object Observations Program, commonly called “Spaceguard,” discovers these objects, characterizes the physical nature of a subset of them, and predicts their paths to determine if any could be potentially hazardous to our planet. There are no known credible impact threats to date — only the continuous and harmless infall of meteoroids, tiny asteroids that burn up in the atmosphere.

JPL hosts the office for Near-Earth Object orbit analysis for NASA’s Near Earth Object Observations Program of the Science Mission Directorate in Washington. JPL is a division of the California Institute of Technology in Pasadena

Image Credit: A Geminid meteor by  Jimmy Westlake
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Edge On


The Cassini spacecraft captures two of Saturn’s moons as it looks across the ring plane from below almost edge on – less than a degree below the ring plane.

Both moons show up nicely in the larger version (click the image above)

Prometheus and Pandora are almost hidden in Saturn’s rings in this image.

Prometheus (53 miles or 86 kilometers across) and Pandora (50 miles or 81 kilometers across) orbit along side Saturn’s narrow F ring, which is shaped, in part, by their gravitational influences help to shape that ring. Their proximity to the rings also means that they often lie on the same line of sight as the rings, sometimes making them difficult to spot.

In this image, Prometheus is the left most moon in the ring plane, roughly in the center of the image. Pandora is towards the right. — 

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Glaciers on Pluto


The flow front of the ice moving into the informally named Sputnik Planum is outlined by the blue arrows (Figure 1). The origin of the ridges and pits on the right side of the image remains uncertain. This image is 390 miles (630 kilometers) across. — New Horizons

Image: NASA/Johns Hopkins University Applied Physics Laboratory/Southwest Research Institute

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Fog on Pluto?


This image is supposed to show fog on Pluto’s surface, not sure I can tell.


In this small section of the larger crescent image of Pluto, taken by NASA’s New Horizons just 15 minutes after the spacecraft’s closest approach on July 14, 2015, the setting sun illuminates a fog or near-surface haze, which is cut by the parallel shadows of many local hills and small mountains. The image was taken from a distance of 11,000 miles (18,000 kilometers), and the width of the image is 115 miles (185 kilometers). – New Horizons

Image Credit:  NASA/Johns Hopkins University Applied Physics Laboratory/Southwest Research Institute



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Pluto’s Horizon



Just 15 minutes after its closest approach to Pluto on July 14, 2015, NASA’s New Horizons spacecraft looked back toward the sun and captured this near-sunset view of the rugged, icy mountains and flat ice plains extending to Pluto’s horizon. The smooth expanse of the informally named icy plain Sputnik Planum (right) is flanked to the west (left) by rugged mountains up to 11,000 feet (3,500 meters) high, including the informally named Norgay Montes in the foreground and Hillary Montes on the skyline. To the right, east of Sputnik, rougher terrain is cut by apparent glaciers. The backlighting highlights more than a dozen layers of haze in Pluto’s tenuous but distended atmosphere. The image was taken from a distance of 11,000 miles (18,000 kilometers) to Pluto; the scene is 780 miles (1,250 kilometers) wide.

The Johns Hopkins University Applied Physics Laboratory in Laurel, Maryland, designed, built, and operates the New Horizons spacecraft, and manages the mission for NASA’s Science Mission Directorate. The Southwest Research Institute, based in San Antonio, leads the science team, payload operations and encounter science planning. New Horizons is part of the New Frontiers Program managed by NASA’s Marshall Space Flight Center in Huntsville, Alabama. – New Horzons

Image Credit: NASA/Johns Hopkins University Applied Physics Laboratory/Southwest Research Institute


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