Tag Archives: Gravitational Lensing

NASA Space Place – One Incredible Galaxy Cluster Yields Two Types Of Gravitational Lenses

Poster’s Note: One of the many under-appreciated aspects of NASA is the extent to which it publishes quality science content for children and Ph.D.’s alike. NASA Space Place has been providing general audience articles for quite some time that are freely available for download and republishing. Your tax dollars help promote science! The following article was provided for reprinting in September, 2016.

By Dr. Ethan Siegel

2013february2_spaceplaceThere is this great idea that if you look hard enough and long enough at any region of space, your line of sight will eventually run into a luminous object: a star, a galaxy or a cluster of galaxies. In reality, the universe is finite in age, so this isn’t quite the case. There are objects that emit light from the past 13.7 billion years—99 percent of the age of the universe—but none before that. Even in theory, there are no stars or galaxies to see beyond that time, as light is limited by the amount of time it has to travel. But with the advent of large, powerful space telescopes that can collect data for the equivalent of millions of seconds of observing time, in both visible light and infrared wavelengths, we can see nearly to the edge of all that’s accessible to us.

The most massive compact, bound structures in the universe are galaxy clusters that are hundreds or even thousands of times the mass of the Milky Way. One of them, Abell S1063, was the target of a recent set of Hubble Space Telescope observations as part of the Frontier Fields program. While the Advanced Camera for Surveys instrument imaged the cluster, another instrument, the Wide Field Camera 3, used an optical trick to image a parallel field, offset by just a few arc minutes. Then the technique was reversed, giving us an unprecedentedly deep view of two closely aligned fields simultaneously, with wavelengths ranging from 435 to 1600 nanometers.

With a huge, towering galaxy cluster in one field and no comparably massive objects in the other, the effects of both weak and strong gravitational lensing are readily apparent. The galaxy cluster—over 100 trillion times the mass of our sun—warps the fabric of space. This causes background light to bend around it, converging on our eyes another four billion light years away. From behind the cluster, the light from distant galaxies is stretched, magnified, distorted, and bent into arcs and multiple images: a classic example of strong gravitational lensing. But in a subtler fashion, the less optimally aligned galaxies are distorted as well; they are stretched into elliptical shapes along concentric circles surrounding the cluster.

A visual inspection yields more of these tangential alignments than radial ones in the cluster field, while the parallel field exhibits no such shape distortion. This effect, known as weak gravitational lensing, is a very powerful technique for obtaining galaxy cluster masses independent of any other conditions. In this serendipitous image, both types of lensing can be discerned by the naked eye. When the James Webb Space Telescope launches in 2018, gravitational lensing may well empower us to see all the way back to the very first stars and galaxies.

If you’re interested in teaching kids about how these large telescopes “see,” be sure to see our article on this topic at the NASA Space Place: spaceplace.nasa.gov/telescope-mirrors/en/

This article was provided by the Jet Propulsion Laboratory, California Institute of Technology, under a contract with the National Aeronautics and Space Administration.

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Caption: Galaxy cluster Abell S1063 (left) as imaged with the Hubble Space Telescope as part of the Frontier Fields program. The distorted images of the background galaxies are a consequence of the warped space dues to Einstein’s general relativity; the parallel field (right) shows no such effects. Image credit: NASA, ESA and Jennifer Lotz (STScI)

About NASA Space Place

With articles, activities, crafts, games, and lesson plans, NASA Space Place encourages everyone to get excited about science and technology. Visit spaceplace.nasa.gov (facebook|twitter) to explore space and Earth science!

NASA News Digest: Space Science For 15 March – 26 March 2015

Greetings fellow astrophiles,

The NASA News service provides up-to-date announcements of NASA policy, news events, and space science. A recent selection of space science articles are provided below, including direct links to the full announcements. Those interested in receiving these news announcements directly from NASA can subscribe to their service by sending an email to:

hqnews-request@newsletters.nasa.gov?subject=subscribe

New Desktop Application Has Potential To Increase Asteroid Detection, Now Available To Public

RELEASE 15-041 (Click here for the full article) – 15 March 2015

2015april2_15_041A software application based on an algorithm created by a NASA challenge has the potential to increase the number of new asteroid discoveries by amateur astronomers.

Analysis of images taken of our solar system’s main belt asteroids between Mars and Jupiter using the algorithm showed a 15 percent increase in positive identification of new asteroids.

During a panel Sunday at the South by Southwest Festival in Austin, Texas, NASA representatives discussed how citizen scientists have made a difference in asteroid hunting. They also announced the release of a desktop software application developed by NASA in partnership with Planetary Resources, Inc., of Redmond, Washington. The application is based on an Asteroid Data Hunter-derived algorithm that analyzes images for potential asteroids. It’s a tool that can be used by amateur astronomers and citizen scientists.

The new asteroid hunting application can be downloaded at: topcoder.com/asteroids

For information about NASA’s Asteroid Grand Challenge, visit: www.nasa.gov/asteroidinitiative

NASA Spacecraft Detects Aurora And Mysterious Dust Cloud Around Mars

RELEASE 15-045 (Click here for the full article) – 18 March 2015

2015april2_15_045aNASA’s Mars Atmosphere and Volatile Evolution (MAVEN) spacecraft has observed two unexpected phenomena in the Martian atmosphere: an unexplained high-altitude dust cloud and aurora that reaches deep into the Martian atmosphere.

The presence of the dust at orbital altitudes from about 93 miles (150 kilometers) to 190 miles (300 kilometers) above the surface was not predicted. Although the source and composition of the dust are unknown, there is no hazard to MAVEN and other spacecraft orbiting Mars.

“If the dust originates from the atmosphere, this suggests we are missing some fundamental process in the Martian atmosphere,” said Laila Andersson of the University of Colorado’s Laboratory for Atmospherics and Space Physics (CU LASP), Boulder, Colorado.

For images related to the findings, visit: http://www.nasa.gov/maven

NASA’s SOFIA Finds Missing Link Between Supernovae And Planet Formation

RELEASE 15-044 (Click here for the full article) – 19 March 2015

2015april2_15_044aUsing NASA’s Stratospheric Observatory for Infrared Astronomy (SOFIA), an international scientific team discovered that supernovae are capable of producing a substantial amount of the material from which planets like Earth can form.

These findings are published in the March 19 online issue of Science magazine.

“Our observations reveal a particular cloud produced by a supernova explosion 10,000 years ago contains enough dust to make 7,000 Earths,” said Ryan Lau of Cornell University in Ithaca, New York.

The research team, headed by Lau, used SOFIA’s airborne telescope and the Faint Object InfraRed Camera for the SOFIA Telescope, FORCAST, to take detailed infrared images of an interstellar dust cloud known as Supernova Remnant Sagittarius A East, or SNR Sgr A East.

For more information about SOFIA, visit: www.nasa.gov/sofia or www.dlr.de/en/sofia

For information about SOFIA’s science mission and scientific instruments, visit: www.sofia.usra.edu or www.dsi.uni-stuttgart.de/index.en.html

NASA’s Opportunity Mars Rover Finishes Marathon, Clocks In At Just Over 11 Years

RELEASE 15-049 (Click here for the full article) – 24 March 2015

2015april2_15_049cThere was no tape draped across a finish line, but NASA is celebrating a win. The agency’s Mars Exploration Rover Opportunity completed its first Red Planet marathon Tuesday — 26.219 miles (42.195 kilometers) – with a finish time of roughly 11 years and two months.

“This is the first time any human enterprise has exceeded the distance of a marathon on the surface of another world,” said John Callas, Opportunity project manager at NASA’s Jet Propulsion Laboratory (JPL) in Pasadena, California. “A first time happens only once.”

The rover team at JPL plans a marathon-length relay run at the laboratory next week to celebrate.

The long-lived rover surpassed the marathon mark during a drive of 153 feet (46.5 meters). Last year, Opportunity became the long-distance champion of all off-Earth vehicles when it topped the previous record set by the former Soviet Union’s Lunokhod 2 moon rover.

For more information about Opportunity, visit www.nasa.gov/rovers

Follow the project on social media at: twitter.com/MarsRovers and www.facebook.com/mars.rovers

NASA’s Hubble, Chandra Find Clues That May Help Identify Dark Matter

RELEASE 15-046 (Click here for the full article) – 26 March 2015

2015april2_15_046Using observations from NASA’s Hubble Space Telescope and Chandra X-ray Observatory, astronomers have found that dark matter does not slow down when colliding with itself, meaning it interacts with itself less than previously thought. Researchers say this finding narrows down the options for what this mysterious substance might be.

Dark matter is an invisible matter that makes up most of the mass of the universe. Because dark matter does not reflect, absorb or emit light, it can only be traced indirectly by, such as by measuring how it warps space through gravitational lensing, during which the light from a distant source is magnified and distorted by the gravity of dark matter.

To learn more about dark matter and test such theories, researchers study it in a way similar to experiments on visible matter — by watching what happens when it bumps into other objects. In this case, the colliding objects under observation are galaxy clusters.

For images and more information about the Hubble Space Telescope, visit: www.nasa.gov/hubble

For more Chandra images, multimedia and related materials, visit: www.nasa.gov/mission_pages/chandra/main

NASA Space Place – The Heavyweight Champion Of The Cosmos

Poster’s Note: One of the many under-appreciated aspects of NASA is the extent to which it publishes quality science content for children and Ph.D.’s alike. NASA Space Place has been providing general audience articles for quite some time that are freely available for download and republishing. Your tax dollars help promote science! The following article was provided for reprinting in February, 2015.

By Dr. Ethan Siegel

2013february2_spaceplaceAs crazy as it once seemed, we once assumed that the Earth was the largest thing in all the universe. 2,500 years ago, the Greek philosopher Anaxagoras was ridiculed for suggesting that the Sun might be even larger than the Peloponnesus peninsula, about 16% of modern-day Greece. Today, we know that planets are dwarfed by stars, which themselves are bound together by the billions or even trillions into galaxies.

But gravitationally bound structures extend far beyond galaxies, which themselves can bind together into massive clusters across the cosmos. While dark energy may be driving most galaxy clusters apart from one another, preventing our local group from falling into the Virgo Cluster, for example, on occasion, huge galaxy clusters can merge, forming the largest gravitationally bound structures in the universe.

Take the “El Gordo” galaxy cluster, catalogued as ACT-CL J0102-4915. It’s the largest known galaxy cluster in the distant universe. A galaxy like the Milky Way might contain a few hundred billion stars and up to just over a trillion (1012) solar masses worth of matter, the El Gordo cluster has an estimated mass of 3 × 1015 solar masses, or 3,000 times as much as our own galaxy! The way we’ve figured this out is fascinating. By seeing how the shapes of background galaxies are distorted into more elliptical-than-average shapes along a particular set of axes, we can reconstruct how much mass is present in the cluster: a phenomenon known as weak gravitational lensing.

That reconstruction is shown in blue, but doesn’t match up with where the X-rays are, which are shown in pink! This is because, when galaxy clusters collide, the neutral gas inside heats up to emit X-rays, but the individual galaxies (mostly) and dark matter (completely) pass through one another, resulting in a displacement of the cluster’s mass from its center. This has been observed before in objects like the Bullet Cluster, but El Gordo is much younger and farther away. At 10 billion light-years distant, the light reaching us now was emitted more than 7 billion years ago, when the universe was less than half its present age.

It’s a good thing, too, because about 6 billion years ago, the universe began accelerating, meaning that El Gordo just might be the largest cosmic heavyweight of all. There’s still more universe left to explore, but for right now, this is the heavyweight champion of the distant universe!

Learn more about “El Gordo” here: www.nasa.gov/press/2014/april/nasa-hubble-team-finds-monster-el-gordo-galaxy-cluster-bigger-than-thought/

El Gordo is certainly huge, but what about really tiny galaxies? Kids can learn about satellite galaxies at NASA’s Space Place spaceplace.nasa.gov/satellite-galaxies/.

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Image credit: NASA, ESA, J. Jee (UC Davis), J. Hughes (Rutgers U.), F. Menanteau (Rutgers U. and UIUC), C. Sifon (Leiden Observatory), R. Mandelbum (Carnegie Mellon U.), L. Barrientos (Universidad Catolica de Chile), and K. Ng (UC Davis). X-rays are shown in pink from Chandra; the overall matter density is shown in blue, from lensing derived from the Hubble space telescope. 10 billion light-years distant, El Gordo is the most massive galaxy cluster ever found.

This article was provided by the Jet Propulsion Laboratory, California Institute of Technology, under a contract with the National Aeronautics and Space Administration.

About NASA Space Place

The goal of the NASA Space Place is “to inform, inspire, and involve children in the excitement of science, technology, and space exploration.” More information is available at their website: http://spaceplace.nasa.gov/