Astronomers find stream of gas, 2.6 million light years long

The bridge of gas (shown in green) stretches from the large galaxy at the bottom left to the group of galaxies at the top. 

A third nearby galaxy to the right also has a shorter stream of gas attached to it. 

The three insets show expanded views of the different galaxies and the green circle indicates the Arecibo telescope beam.

Credit: Rhys Taylor /Arecibo Galaxy Environment Survey /The Sloan Digital Sky Survey Collaboration

Atronomers and students have found a bridge of atomic hydrogen gas 2.6 million light years long between galaxies 500 million light years away.

They detected the gas using the William E. Gordon Telescope at the Arecibo Observatory, a radio astronomy facility of the US National Science Foundation sited in Puerto Rico.

The results are published today in a paper in Monthly Notices of the Royal Astronomical Society.

The stream of atomic hydrogen gas is the largest known, a million light years longer than a gas tail found in the Virgo Cluster by another Arecibo project a few years ago.

Dr Rhys Taylor, a researcher at the Czech Academy of Sciences and lead author of the paper, said "This was totally unexpected.

We frequently see gas streams in galaxy clusters, where there are lots of galaxies close together, but to find something this long and not in a cluster is unprecedented."

It is not just the length of the stream that is surprising but also the amount of gas found in it. Roberto Rodriguez, a 2014 graduate from the University of Puerto Rico in Humacao who worked on the project as an undergraduate, explained "We normally find gas inside galaxies, but here half of the gas, 15 billion times the mass of the Sun, is in the bridge. That's far more than in the Milky Way and Andromeda galaxies combined!"

The team is still investigating the origin of the stream. One notion surmises that the large galaxy at one end of the stream passed close to the group of smaller galaxies at the other end in the past, and that the gas bridge was drawn out as they moved apart, while a second notion presumes that the large galaxy plowed straight through the middle of the group, pushing gas out of it.

The team plan to use computer simulations to find out which of these ideas can best match the shape of the bridge that is seen with the Arecibo Telescope.

The project involved three undergraduate researchers: Roberto Rodriguez and Clarissa Vazquez from UPR Humacao, and Hanna Herbst, now a graduate student at the University of Florida. Dr Robert Minchin, a staff astronomer at Arecibo Observatory and the principal investigator on the project, said "Student involvement is very important to us."

"We are proud to be inspiring the next generation of astronomers, and particularly proud of the involvement of Puerto Rican students."

The bridge was found in data taken between 2008 and 2011 for the Arecibo Galaxy Environment Survey (AGES), which is using the power of the Arecibo Telescope to survey a large area of sky with a high level of sensitivity.

Journal Reference: R. Taylor, R. F. Minchin, H. Herbst, J. I. Davies, R. Rodriguez And C. Vazquez. The Arecibo Galaxy Environment Survey – VII. A dense filament with extremely long H i streams. Monthly Notices of the Royal Astronomical Society, 2014 DOI: 10.1093/mnras/stu1305

Giant telescopes pair up to image near-Earth asteroid - video

NASA scientists used Earth-based radar to produce these sharp views - an image montage and a movie sequence, of the asteroid designated '2014 HQ124' on June 8, 2014. 

Credit: NASA /JPL-Caltech /Arecibo Observatory /USRA /NSF

NASA scientists using Earth-based radar have produced sharp views of a recently discovered asteroid as it slid silently past our planet.

Captured on June 8, 2014, the new views of the object designated "2014 HQ124" are some of the most detailed radar images of a near-Earth asteroid ever obtained.

An animation of the rotating asteroid and a collage of the images are available below.

The radar observations were led by scientists Marina Brozovic and Lance Benner of NASA's Jet Propulsion Laboratory, Pasadena, California.

The JPL researchers worked closely with Michael Nolan, Patrick Taylor, Ellen Howell and Alessondra Springmann at Arecibo Observatory in Puerto Rico to plan and execute the observations.

According to Benner, 2014 HQ124 appears to be an elongated, irregular object that is at least 1,200 feet (370 meters) wide on its long axis.

"This may be a double object, or 'contact binary,' consisting of two objects that form a single asteroid with a lobed shape," he said.

The images reveal a wealth of other features, including a puzzling pointy hill near the object's middle, on top as seen in the images.

The 21 radar images were taken over a span of four-and-a-half hours. During that interval, the asteroid rotated a few degrees per frame, suggesting its rotation period is slightly less than 24 hours.

At its closest approach to Earth on June 8, the asteroid came within 776,000 miles (1.25 million kilometers), or slightly more than three times the distance to the moon.

Scientists began observations of 2014 HQ124 shortly after the closest approach, when the asteroid was between about 864,000 miles and 902,000 miles (1.39 million kilometers and 1.45 million kilometers) from Earth.

Each image in the collage and movie represents 10 minutes of data.


Credit: NASA

The new views show features as small as about 12 feet (3.75 meters) wide. This is the highest resolution currently possible using scientific radar antennas to produce images.

Such sharp views for this asteroid were made possible by linking together two giant radio telescopes to enhance their capabilities.

To obtain the new views, researchers paired the 230-foot (70-meter) Deep Space Network antenna at Goldstone, California, with two other radio telescopes, one at a time.

Using this technique, the Goldstone antenna beams a radar signal at an asteroid and the other antenna receives the reflections.

The technique dramatically improves the amount of detail that can be seen in radar images.

To image 2014 HQ124, the researchers first paired the large Goldstone antenna with the 1,000-foot (305-meter) Arecibo radio telescope in Puerto Rico.

They later paired the large Goldstone antenna with a smaller companion, a 112-foot (34-meter) antenna, located about 20 miles (32 kilometers) away.

A recent equipment upgrade at Arecibo enabled the two facilities to work in tandem to obtain images with this fine level of detail for the first time.

"By itself, the Goldstone antenna can obtain images that show features as small as the width of a traffic lane on the highway," said Benner.

"With Arecibo now able to receive our highest-resolution Goldstone signals, we can create a single system that improves the overall quality of the images."

The first five images in the new sequence, the top row in the collage, represent the data collected by Arecibo, and are 30 times brighter than what Goldstone can produce observing on its own.