Hubble Observations: From the Ground to Your Computer

This post is the second in a two-part series.

In my last post, “Hubble Observations: From the Sky to the Ground,” I wrote about the route Hubble images take as they are digitally transferred from space to the ground.

This is the story of what happens after that data makes the 30-mile trip over land-lines from NASA’s Goddard Space Flight Center in Greenbelt, Md., to the Space Telescope Science Institute in Baltimore, Md., and ultimately to your computer as iconic Hubble pictures.

Hubble generates approximately 855 gigabytes of new science data each month. That’s the equivalent of an 8,550-yard-long shelf of books. Astronomers, in turn, typically download six terabytes of data monthly from this growing archive. That would be the equivalent of the printed paper from 300,000 trees. By the beginning of April 2014, Hubble data had been used to publish more than 12,000 peer-reviewed scientific papers.

The raw Frontier Fields data are available to the public immediately from a repository called the Barbara A. Mikulski Archive for Space Telescopes, or MAST. However, these data are not the beautiful, color Hubble images we have come to know and love. Raw images from the telescope are black and white, and include distortions introduced by the instruments, as well other unwanted artifacts from Earthshine, occasional Earth-orbiting satellite trails, bad pixels, and random hits by small, charged particles called cosmic rays.

Cosmic ray signatures are removed by combining two exposures in a way that removes everything not in both images. Credit: NASA, ESA, and J. Lotz, M. Mountain, A. Koekemoer, the HFF Team, and Ann Feild (STScI).

Cosmic ray signatures are removed by combining two exposures in a way that removes everything not in both images. Credit: NASA, ESA, and J. Lotz, M. Mountain, A. Koekemoer, the HFF Team, and Ann Feild (STScI).

 

It takes a team of about a dozen instrument analysts to “clean” these images by removing the distortions and artifacts. The refined images are posted once a week on MAST. These are the combination of multiple exposures taken in seven different filters, which allow light at specific wavelengths to enter the instruments.

Hubble’s instruments have many filters. The Frontier Fields observations use four in infrared from the Wide Field Camera 3 (WFC3), and three in visible light from the Advanced Camera for Surveys (ACS). The final, deep, combined color image for each Frontier Field will have a total of 560 exposures, divided evenly between the main cluster and its parallel field.

To produce a color picture, exposures from the seven filters are assigned the three primary colors of blue, green, and red based on their wavelengths.  Images from the shortest, bluest wavelengths are assigned to blue, while images from the longest, reddest wavelengths are assigned to red, and intermediate wavelengths are assigned to green. These primary color images are then composited to produce the full-color picture so familiar to Hubble followers.

The top row shows the combined exposures through each of the seven filters as single images.  To produce the color pictures, exposures from several, selected filters from Hubble’s WFC3 and ACS were combined into one of three primary colors based on their wavelengths. The primary color images were then composited to produce the full-color image. Credit: NASA, ESA, and J. Lotz, M. Mountain, A. Koekemoer, the HFF Team, and Ann Feild (STScI).

The top row shows the combined exposures through each of the seven filters as single images. To produce the color pictures, exposures from several selected filters from Hubble’s WFC3 and ACS were combined into one of three primary colors based on their wavelengths. The primary color images were then composited to produce the full-color image. Credit: NASA, ESA, and J. Lotz, M. Mountain, A. Koekemoer, the HFF Team, and Ann Feild (STScI).

See a large collection of color Hubble images.

Amateur astronomers may want to see the raw Frontier Fields images.

There is a Facebook page  for amateur astronomical image processors to exchange information, tips and techniques, and share their work.

 

Hubble Observations: From the Sky to the Ground

This post is part one in a two-part series.

How does what Hubble sees become what you see? The first part involves moving science data from the sky to the ground—a complicated matter.

When Hubble views an astronomical target, the digital information from that observation is stored onboard the telescope’s solid-state data recorders. The telescope records all of its science data to prevent any possible loss of unique information. Hubble’s flight operations team at Goddard Space Flight Center, in Greenbelt, Maryland manages the content of these recorders.

Four antennae aboard Hubble send and receive information between the telescope and the ground. To communicate with the flight operations team, Hubble uses a group of NASA satellites called the Tracking and Data Relay Satellite System (TDRSS). Located in various positions across the sky, the TDRSS satellites provide nearly continuous communications coverage with Hubble.

Hubble’s operators periodically transmit the data from Hubble through TDRSS to TDRSS’s ground terminal at White Sands, New Mexico. From there, the data are sent via landline to Goddard to ensure their completeness and accuracy.

Goddard then transfers the data over landlines to the Space Telescope Science Institute in Baltimore, Maryland for processing, calibration, and archiving. There, they are translated into scientific information, such as wavelength and brightness, and ultimately into the iconic images that have become the hallmark of Hubble.

We’ll discuss how those images are made in a future post.

Image Credit: Ann Feild, STScI

Image Credit: Ann Feild, STScI

How Were the Galaxy Clusters Chosen?

The 12 Frontier Fields will greatly expand upon our knowledge of the earliest galaxies to form in the universe. These images of the distant universe (in space and time), will provide us with a sneak peek at the first billion years of the universe. So how were these fields chosen?

The Frontier Fields program was sketched out by the Frontier Fields team in the earliest phases of a recommendation process. Much can change in the process of going from an initial recommendation to a final program. The final program hinged upon finding the best galaxy clusters to anchor the Frontier Fields program. Team members deliberated between several different galaxy clusters, nominated by both those directly involved in the program and the broader astronomical community, before settling on the final candidates.

Special consideration was given to galaxy clusters that

  1. maximize magnification and fit within Hubble’s view;
  2. were located in “clean” locations on the sky;
  3. were observable by ground-based observatories in the Northern and Southern hemispheres.

The Frontier Fields team, with input from the broader astronomical community, was able to narrow down the galaxy cluster candidates to the six chosen for the program. Although it was not possible to select six clusters that met all of the criteria, most of the clusters satisfied most of the criteria. Let us explore the three criteria in a little bit more depth.

 

Maximize Magnification

Astronomers focused on massive galaxy clusters as candidates because the gravitational lenses they create are likely to provide the greatest magnification of background galaxies, but there were other considerations as well.

Hubble is observing the Frontier Fields with a visible-light instrument and an infrared-light instrument. The fields of view of these instruments, defined to be the area of the sky they can image in one pointing, are relatively small – a box with sides about 1/15 the width of the full moon. Because of the small fields of view, the galaxy clusters need to be relatively compact so that any magnified background galaxy remains within the fields of view.

There is another reason why the galaxy clusters must  be relatively compact in size. For each of the galaxy clusters, Hubble is also imaging an adjacent parallel field. For the goals of the program, the parallel fields need to contain unobstructed views of the early universe, devoid of the metropolis of galaxies that make up the galaxy clusters. Astronomers lose the magnifying power of the galaxy clusters, but gain simplicity. For the parallel fields, astronomers do not require detailed models of how the light from the distant galaxies are lensed by the foreground clusters.

 

Clean Locations on the Sky

Below is a map of the sky showing the locations of the six pointings required for Hubble to acquire the 12 Frontier Fields, labeled in order of when Hubble plans to observe them. The green labels are previous deep-field programs. The map is in right ascension and declination coordinates.

For a map of the Frontier Fields on the sky, with respect to the constellations, see this previous post.  Note: The right ascension of the map in the previous post is flipped with respect to the map below in order to portray the constellations as they appear to us on Earth.

 

Locations of the Frontier Fields on the sky. The colors denote the amount of extinction of background light due to dust - red is greatest dust extinction, blue is least dust extinction. The wavy dust band across the sky is our Milky Way galaxy. Credit: D. Coe (STScI),  D. Schlegel (LBNL), D. P. Finkbeiner (Harvard), M. Davis (Berkeley)

This map shows the locations of the Frontier Fields on the sky using right ascension and declination coordinates. The Frontier Fields are numbered in the order of their observations. The colors denote the amount of extinction, or dimming, of light from distant galaxies due to foreground dust. Dark red denotes the greatest dust extinction. Dark blue denotes the least dust extinction. The wavy dust band across the sky is our Milky Way galaxy. The thick purple line is the ecliptic, which is the plane of our solar system. The two thinner parallel purple lines mark 30 degrees north and 30 degrees south of the ecliptic. Previous deep-field programs are labeled on the map in green: HDF-N (Hubble Deep Field North), HDF-S (Hubble Deep Field South), UDF (Ultra Deep Field), UDS (Ultra Deep Survey), COSMOS (the Cosmic Evolution Survey), and EGS (the Extended Groth Strip). Sgr A* denotes the position of the center of our Milky Way galaxy.
Credit: D. Coe (STScI), D. Schlegel (LBNL), D. P. Finkbeiner (Harvard), M. Davis (Berkeley)

 

The two main features to note on the above map are the colors that signify dust that can lessen the light from distant galaxies reaching Hubble’s mirror and the thick purple line that marks the plane of our solar system, known as the ecliptic. The locations of the Frontier Fields’ galaxy clusters were chosen to be in relatively “clean” parts of the sky.  By that we mean that the galaxy clusters are not located where there is a large quantity of foreground dust.

Dust Extinction

The galaxy clusters in the Frontier Fields were chosen to avoid areas of greatest dust extinction. Dust extinction is the scattering or absorption of light by dust. It is problematic because it lessens the light we receive from distant objects. On the above map, dark red denotes areas of greatest dust extinction. Dark blue denotes little dust extinction. The red, high-extinction band in the all-sky map is due to the dusty disk of our own Milky Way galaxy. It appears wavy due to the projection of the sky onto the right ascension and declination coordinate system.

Zodiacal Light

The thick purple line denotes the plane of our solar system, called the ecliptic. Dust within our solar system is clustered around the ecliptic. This dust scatters the light from our Sun and produces a bright haze. It can be very difficult to observe faint objects through the zodiacal light. For this reason, the galaxy clusters were chosen to avoid the ecliptic.

 

Observable from Telescopes across the Earth

Much of what we learn from the Frontier Fields will come from follow-up observations using ground-based telescopes. Most of the galaxy clusters in the Frontier Fields are observable by state-of-the-art astronomical telescopes in both the Northern and Southern hemispheres. These include the new radio telescope in Chile, named ALMA, and the suite of telescopes on Mauna Kea in Hawaii.

For more info, the Frontier Fields galaxy cluster selection was also recently described in a Google+ Hubble Hangout.

 

 

Frontier Fields: Locations on the Sky

The galaxies in Hubble’s Frontier Fields project are so far away that they cannot be seen with either your eyes or a backyard telescope. It takes a state-of-the-art telescope like Hubble, Spitzer, or Chandra to collect enough of the scant photons streaming in from the most distant galaxies to produce a scientifically valuable image. In fact, Hubble’s views of the Frontier Fields, coupled with the natural lensing power of the galaxy clusters, allow astronomers to potentially detect objects that are 40 billion – yes, billion – times fainter than your eyes can see.

The galaxies in the Frontier Fields are so far away that they appear absolutely tiny in the night sky, even to Hubble. Hubble has the exquisite ability to resolve tremendously small features on the sky and discern details that would otherwise be blurred beyond recognition. If prior deep field observations are any indication, Hubble will observe thousands of galaxies in an area approximately the size of a pin-prick in a piece of paper held up at arm’s length.

The 12 Frontier Fields are located at six positions in the sky. You may not be able to see the Frontier Fields galaxies, but you can still find the area of the sky where they are located using the graphic below.  

The location of the Frontier Fields on the sky, using Right Ascension and Declination coordinates.  The Milky Way in this coordinate system is shown as a wavy band of diffuse light across the sky.

The location of the Frontier Fields on the sky, using Right Ascension and Declination coordinates. The Frontier Fields are numbered in the order that Hubble plans to observe them over the three-year program. The names refer to the galaxy clusters targeted in each pointing. Each pointing also has an adjacent parallel field. A few of the previous Hubble deep-field observations are labeled as well – Hubble Deep Field North (HDF-N), Hubble Deep Field South (HDF-S), and the Hubble Ultra Deep Field (HUDF). The Milky Way in this coordinate system is shown as a wavy band of diffuse light across the sky.
SOURCES: Frontier Fields locations: STScI; All-sky star chart: J. Cornmell and
IAU

The map above uses a coordinate system familiar to astronomers. Right Ascension is similar to longitude in that it measures the position of an object east or west of a reference position. Right Ascension is measured in hours, from 0 to 24 hours, with the reference position set at 0 hours. Declination is similar to latitude. It measures the position of an object, in degrees from 0 to 90, north or south of a reference position. The reference position (0 degrees) for declination is the celestial equator, which is the projection of Earth’s equator onto the sky.  In this particular map we have truncated declination at 70 degrees north and south.

The Frontier Field’s site map (above) is a representation of the sky on a rectangular grid. When we view the sky from the surface of the Earth, it appears as the interior surface of a hemisphere, or dome — half of what people in ancient times referred to as the “celestial sphere” surrounding the Earth. Just as there are distortions when map-makers make a rectangular map of the spherical Earth, there are distortions in projecting the celestial sphere onto a rectangular grid. Constellations located near the northern and southern celestial poles (90 degrees north and south in declination) are represented on the map as spanning more of the sky than they actually do.

To help find the locations of the Frontier Fields, zoomed-in regions of the six pointings are shown below:

1) Abell 2744

Location of the Abell 2744 galaxy cluster field and its parallel field in the Sculptor constellation.SOURCES: Frontier Field location: STScI; Enlarged constellation map: International Astronomical Union (IAU)

Location of the Abell 2744 galaxy cluster field and its parallel field in the Sculptor constellation.
SOURCES: Frontier Field location: STScI; Enlarged constellation map: International Astronomical Union (IAU)

2) MACS J0416

Location of the MACS J0416 galaxy cluster field and its parallel field in the Eridanus constellation.SOURCES: Frontier Field location: STScI; Enlarged constellation map: International Astronomical Union (IAU)

Location of the MACS J0416 galaxy cluster field and its parallel field in the Eridanus constellation.
SOURCES: Frontier Field location: STScI; Enlarged constellation map: International Astronomical Union (IAU)

3) MACS J0717

Location of the MACS J0717 galaxy cluster field and its parallel field in the Eridanus constellation.SOURCES: Frontier Field location: STScI; Enlarged constellation map: International Astronomical Union (IAU)

Location of the MACS J0717 galaxy cluster field and its parallel field in the Auriga constellation.
SOURCES: Frontier Field location: STScI; Enlarged constellation map: International Astronomical Union (IAU)

4) MACS J1149

Location of the MACS J1149 galaxy cluster field and its parallel field in the Eridanus constellation.SOURCES: Frontier Field location: STScI; Enlarged constellation map: International Astronomical Union (IAU)

Location of the MACS J1149 galaxy cluster field and its parallel field in the Leo constellation.
SOURCES: Frontier Field location: STScI; Enlarged constellation map: International Astronomical Union (IAU)

5) Abell S1063

Location of the Abell S1063 galaxy cluster field and its parallel field in the Eridanus constellation.SOURCES: Frontier Field location: STScI; Enlarged constellation map: International Astronomical Union (IAU)

Location of the Abell S1063 galaxy cluster field and its parallel field in the Grus constellation.
SOURCES: Frontier Field location: STScI; Enlarged constellation map: International Astronomical Union (IAU)

6) Abell 370

Location of the Abell 370 galaxy cluster field and its parallel field in the Eridanus constellation.SOURCES: Frontier Field location: STScI; Enlarged constellation map: International Astronomical Union (IAU)

Location of the Abell 370 galaxy cluster field and its parallel field in the Cetus constellation.
SOURCES: Frontier Field location: STScI; Enlarged constellation map: International Astronomical Union (IAU)

For more tips and information about observing the night sky, including access to free monthly sky charts, visit the NASA Night Sky Network. For monthly highlights of interesting objects to observe in the night sky, visit Hubblesite’s Tonight’s Sky.

Meet the Frontier Fields: Abell 370

This is the last in a series of six posts introducing and providing essential facts about each of the Frontier Fields.

Abell 370 has several hundred galaxies in its core, or center. This galaxy cluster has a storied astronomical history and was one of the first clusters in which astronomers observed gravitational lensing. In the archival Hubble image at below right, the long arc on the right was found not to be a member of the cluster by ground-based observations. The arc is actually a lensed galaxy residing two times farther away than the cluster.

The Abell catalogue of galaxy clusters was first compiled by astronomer George O. Abell in 1958, with over 2,700 galaxy clusters observable from the Northern Hemisphere. The Abell catalogue was updated in 1989 with galaxy clusters from the Southern Hemisphere. Abell 370 is the most distant galaxy cluster in the Abell catalogue, but we now know of many galaxy clusters that are even more distant.

(Left) Locations of Hubble’s observations of the Abell 370 galaxy cluster, right, and the nearby parallel field, left, plotted over a Digital Sky Survey (DSS) image. The blue boxes outline the regions of Hubble’s visible light observations, and the red boxes indicate areas of Hubble’s infrared light observations. The 1’ bar, read as one arcminute, corresponds to approximately 1/30 the apparent width of the full moon as seen from Earth.   (Right) Archival Hubble image of the Abell 370 galaxy cluster taken in visible light. Left Credit: Digitized Sky Survey (STScI/NASA) and Z. Levay (STScI). Right Credit: NASA, ESA, the Hubble SM4 ERO Team, and ST-ECF

Left: The locations of Hubble’s observations of the Abell 370 galaxy cluster (right) and the adjacent parallel field (left) are plotted over a Digitized Sky Survey (DSS) image. The blue boxes outline the regions of Hubble’s visible-light observations, and the red boxes indicate areas of Hubble’s infrared-light observations. A scale bar in the lower left corner of the image indicates the size of the image on the sky. The scale bar corresponds to approximately 1/30th the apparent width of the full moon as seen from Earth. Astronomers refer to this unit of measurement as one arcminute, denoted as 1′.
Right: Hubble’s view of the galaxy cluster is displayed using archival visible-light observations. Deeper Frontier Fields observations of Abell 370 are being planned.
Left Credit: Digitized Sky Survey (STScI/NASA) and Z. Levay (STScI).
Right Credit: NASA, ESA, the Hubble SM4 ERO Team, and ST-ECF

Estimated Dates of Observations: TBD

The planned dates for Hubble observations of the Frontier Fields include observations approximately six months apart. This is the time it takes for the cameras on Hubble to swap positions so that both visible-light data and infrared-light data can be captured from the galaxy cluster field and the adjacent parallel field, as described in this post.

Galaxy Cluster Redshift: 0.375

Redshift measures the lengthening of a light wave from an object that is moving away from an observer. For example, when a galaxy is traveling away from Earth, its observed wavelength shifts toward the red end of the electromagnetic spectrum. The galaxy cluster’s cosmological redshift refers to a lengthening of a light wave caused by the expansion of the universe. Light waves emitted by a galaxy cluster stretch as they travel through the expanding universe. The greater the redshift, the farther the light has traveled to reach us.

Galaxy Cluster Distance: approximately 4 billion light-years

Galaxy Cluster Field Coordinates (R.A., Dec.): 02:39:52.9, -01:34:36.5

Parallel Field Coordinates (R.A., Dec.): 02:40:13.4, -01:37:32.8

Constellation: Cetus

Related Hubble News:

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Meet the Frontier Fields: Abell S1063

This is the fifth in a series of posts introducing and providing essential facts about each of the Frontier Fields.

As observed by NASA’s Chandra X-ray Observatory, the Abell S1063 galaxy cluster is incredibly bright in high-energy X-ray light1. When neighboring galaxies or clusters of galaxies merge due to gravity, the infalling gases collide. The resulting shock heats the gas, which then emits high-energy X-ray light. The Abell S1063 galaxy cluster’s X-ray brightness is one of the clues that suggests we may actually be observing a major event involving the merging of multiple galaxy clusters.

The Abell catalogue of galaxy clusters was first compiled by astronomer George O. Abell in 1958, with over 2,700 galaxy clusters observable from the Northern Hemisphere. The Abell catalogue was updated in 1989 with galaxy clusters from the Southern Hemisphere.

Locations of Hubble's observations of the Abell S1063 galaxy cluster (right) and the nearby parallel field (left), plotted over a Digital Sky Survey (DSS) image. The blue boxes outline the regions of Hubble's visible light observations, and the red boxes indicate areas of Hubble's infrared light observations. The 1’ bar, read as one arcminute, corresponds to approximately 1/30 the apparent width of the full moon as seen from Earth. Credit: Digitized Sky Survey (STScI/NASA) and Z. Levay (STScI).

The locations of Hubble’s observations of the Abell S1063 galaxy cluster (right) and the adjacent parallel field (left) are plotted over a Digitized Sky Survey (DSS) image. The blue boxes outline the regions of Hubble’s visible-light observations, and the red boxes indicate areas of Hubble’s infrared-light observations. A scale bar in the lower left corner of the image indicates the size of the image on the sky. The scale bar corresponds to approximately 1/30th the apparent width of the full moon as seen from Earth. Astronomers refer to this unit of measurement as one arcminute, denoted as 1′.
Credit: Digitized Sky Survey (STScI/NASA) and Z. Levay (STScI).

Estimated Dates of Observations: TBD

The planned dates for Hubble observations of the Frontier Fields include observations approximately six months apart. This is the time it takes for the cameras on Hubble to swap positions so that both visible-light data and infrared-light data can be captured from the galaxy cluster field and the adjacent parallel field, as described in this post.

Galaxy Cluster Redshift: 0.348

Redshift measures the lengthening of a light wave from an object that is moving away from an observer. For example, when a galaxy is traveling away from Earth, its observed wavelength shifts toward the red end of the electromagnetic spectrum. The galaxy cluster’s cosmological redshift refers to a lengthening of a light wave caused by the expansion of the universe. Light waves emitted by a galaxy cluster stretch as they travel through the expanding universe. The greater the redshift, the farther the light has traveled to reach us.

Galaxy Cluster Distance: approximately 4 billion light-years

Galaxy Cluster Field Coordinates (R.A., Dec.): 22:48:44.4, -44:31:48.5

Parallel Field Coordinates (R.A., Dec.): 22:49:17.7, -44:32:43.8

Constellation: Grus

Related Hubble News:

Looking for Hubble data used by scientists?

References to science journal articles:

1: X-ray and Optical Observations of the Merging Cluster Abell S1063

Galaxy Find Showcases Frontier Fields’ Potential

A faraway object in Frontier Fields cluster Abell 2744 could be one of the most distant galaxies found to date, according to an international team studying a combination of Hubble and Spitzer data on the cluster.

The galaxy, called Abell2744_Y1, is about 30 times smaller than our Milky Way galaxy but is producing at least 8 times more stars. Further observations are needed to verify the galaxy’s redshift, which will help determine how truly distant it is. The highest-redshift galaxies, with values greater than 8 or 9, are so distant we see them as they were about 13 billion years ago. For comparison, galaxies with a redshift around 0 are in our local neighborhood and galaxies with a redshift of around 1 appear as they were halfway back to the Big Bang. Astronomers are hoping Abell2744_Y1 is in the high-redshift range.

hs-2014-17-a-web_printAbell2744_Y1 (right) and its location in the Abell 2744 galaxy cluster (left). Credit: NASA, ESA, and J. Lotz, M. Mountain, A. Koekemoer, and the HFF Team (STScI), and N. Laporte (Instituto de Astrofisica de Canarias)

Though scientists are interested in galaxies with redshifts in the lower range, technological advances have made those discoveries far more routine. For many astronomers, the focus today is on galaxies with the higher redshifts. The difference is significant, since lower-redshift galaxies appear in our observations as they were billions of years after the Big Bang, but higher-redshift galaxies can show us the state of the universe just hundreds of millions of years after the Big Bang.

Astronomers can find these high-redshift objects with modern telescopes, but the ones they see tend to be the biggest, brightest galaxies of the early universe — the unusual objects, the outliers. To see the more normal objects — the typical galaxies of the time — astronomers use natural gravitational lenses in space to extend the reach of telescopes. And that’s where Frontier Fields comes in.

The Frontier Fields project will be looking at galaxy cluster Abell 2744 again in May, and using its natural lens to find more galaxies like Abell2744_Y1. The more ordinary, representative galaxies astronomers encounter, the better they can understand and explain the development of the early universe. Just as you couldn’t draw an accurate portrait of humanity by only examining the tallest people on the planet, scientists can’t build a complete picture of the universe when they can only detect its biggest and brightest galaxies. Astronomers need a large sample of everyday galaxies to learn what that population is really like.

Since 2006, the number of high-redshift galaxies known has increased from a dozen to 236, but only two have been confirmed as actually being high-redshift galaxies. To truly confirm the objects’ distances, astronomers need to obtain spectra of the galaxies. When Hubble looks at Abell 2744, it won’t be taking spectra of Abell2744_Y1, but the galaxy is bright enough to be detected by major ground-based telescopes, so it’s possible an Earth-based observatory may confirm its distance.

The small galaxy is producing stars at a rate of anywhere from eight to 60 solar masses per year, much more than the Milky Way’s star production rate of about one to three solar masses per year. A solar mass is the equivalent of our Sun’s mass. That number may not sound like much, but remember that stars develop over the course of millions of years, meaning that tiny galaxy is pumping out stars at a thoroughly respectable pace. Will other distant galaxies magnified by Abell 2744′s gravitational lens match its production? We’ll learn more as the Frontier Fields data begins to pour in.

Meet the Frontier Fields: MACS J1149.5+2223

This is the fourth in a series of posts introducing and providing essential facts about each of the Frontier Fields.

The gravitational lens created by the galaxy cluster MACS J1149 already has a record of stirring up excitement. In 2012, observations from NASA’s Hubble and Spitzer space telescopes found the cluster had magnified a distant background galaxy. The galaxy turned out to be extremely far away — in fact, the light we detected from the galaxy likely began its intergalactic journey approximately 500 million years after the Big Bang1. This galaxy appears to us as it looked when the universe was just 3.6 percent of its present age of 13.7 billion years — a baby picture of a (very) distant relative. Astronomers estimate that the gravitational lens of MACS J1149 magnified the brightness of this distant galaxy by 15 times; it would have remained undetected were it not for the help from one of nature’s powerful lenses. This discovery bodes well for the deeper images of galaxy clusters being undertaken in the Frontier Fields program.

The Massive Cluster Survey (MACS) contains a sample of more than 100 galaxy clusters, measured by the ROSAT telescope to be bright in high-energy X-ray light. The goal of the MACS survey is to understand distant, massive galaxy clusters.

(Left) Locations of Hubble’s observations of the MACS  J1149 galaxy cluster, top, and the nearby parallel field, bottom, plotted over a Digital Sky Survey (DSS) image. The blue boxes outline the regions of Hubble’s visible light observations, and the red boxes indicate areas of Hubble’s infrared light observations. The 1’ bar, read as one arcminute, corresponds to approximately 1/30 the apparent width of the full moon as seen from Earth. (Right) Archival Hubble image of the MACS J1149 galaxy cluster taken in visible light. Left Credit: Digitized Sky Survey (STScI/NASA) and Z. Levay (STScI). Right Credit: NASA, ESA, and M. Postman (STScI), and the CLASH team.

Left: The locations of Hubble’s observations of the MACS J1149 galaxy cluster (top) and the adjacent parallel field (bottom) are plotted over a Digitized Sky Survey (DSS) image. The blue boxes outline the regions of Hubble’s visible-light observations, and the red boxes indicate areas of Hubble’s infrared-light observations. A scale bar in the lower left corner of the image indicates the size of the image on the sky. The scale bar corresponds to approximately 1/30th the apparent width of the full moon as seen from Earth. Astronomers refer to this unit of measurement as one arcminute, denoted as 1′.
Right: Hubble’s view of the galaxy cluster is displayed using archival visible-light observations. Deeper Frontier Fields observations of MACS J1149 are planned for 2014 and 2015.
Left Credit: Digitized Sky Survey (STScI/NASA) and Z. Levay (STScI).
Right Credit: NASA, ESA, and M. Postman (STScI), and the CLASH team.

Estimated Dates of Observations: April-June 2014, November 2014-February 2015, and April-July 2015

The planned dates for Hubble observations of the Frontier Fields include observations approximately six months apart. This is the time it takes for the cameras on Hubble to swap positions so that both visible-light data and infrared-light data can be captured from the galaxy cluster field and the adjacent parallel field, as described in this post.

Galaxy Cluster Redshift: 0.543

Redshift measures the lengthening of a light wave from an object that is moving away from an observer. For example, when a galaxy is traveling away from Earth, its observed wavelength shifts toward the red end of the electromagnetic spectrum. The galaxy cluster’s cosmological redshift refers to a lengthening of a light wave caused by the expansion of the universe. Light waves emitted by a galaxy cluster stretch as they travel through the expanding universe. The greater the redshift, the farther the light has traveled to reach us.

Galaxy Cluster Distance: approximately 5 billion light-years

Galaxy Cluster Field Coordinates (R.A., Dec.): 11:49:36.3, +22:23:58.1

Parallel Field Coordinates (R.A., Dec.): 11:49:40.5, +22:18:02.3

Constellation: Leo

Related Hubble News:

Looking for Hubble data used by scientists?

References to science journal articles:

1: A highly magnified candidate for a young galaxy seen when the Universe was 500 Myrs old

Meet the Frontier Fields: MACS J0717.5+3745

This is the third in a series of posts introducing and providing essential facts about each of the Frontier Fields.

MACS J0717 has been observed by telescopes in many visible and invisible wavelengths of light. It is one of the most massive galaxy clusters known, and it is the largest known gravitational lens1. Of all of the galaxy clusters known and measured, MACS J0717 lenses the largest area of the sky.

The Massive Cluster Survey (MACS) contains a sample of more than 100 galaxy clusters, measured by the ROSAT telescope to be bright in high-energy X-ray light. The goals of the MACS survey are to categorize and better understand distant massive galaxy clusters. J0717 has the highest X-ray temperature in the MACS survey.

(Left) Locations of Hubble’s observations of the MACS J0717 galaxy cluster, bottom, and the nearby parallel field, top, plotted over a Digital Sky Survey (DSS) image. The blue boxes outline the regions of Hubble’s visible light observations, and the red boxes indicate areas of Hubble’s infrared light observations. The 1’ bar, read as one arcminute, corresponds to approximately 1/30 the apparent width of the full moon as seen from Earth. (Right) Archival Hubble image of the MACS J0717 galaxy cluster taken in visible light. Left Credit: Digitized Sky Survey (STScI/NASA) and Z. Levay (STScI). Right Credit: NASA, ESA, and H. Ebeling (University of Hawaii).

Left: The locations of Hubble’s observations of the MACS J0717 galaxy cluster (bottom) and the adjacent parallel field (top) are plotted over a Digitized Sky Survey (DSS) image. The blue boxes outline the regions of Hubble’s visible-light observations, and the red boxes indicate areas of Hubble’s infrared-light observations. A scale bar in the lower left corner of the image indicates the size of the image on the sky. The scale bar corresponds to approximately 1/30th the apparent width of the full moon as seen from Earth. Astronomers refer to this unit of measurement as one arcminute, denoted as 1′.
Right: Hubble’s view of the galaxy cluster is displayed using archival visible-light observations. Deeper Frontier Fields observations of MACS J0717 are planned for 2014 and 2015.
Left Credit: Digitized Sky Survey (STScI/NASA) and Z. Levay (STScI).
Right Credit: NASA, ESA, and H. Ebeling (University of Hawaii).

Estimated Dates of Observations: September-November 2014 and February-May 2015

The planned dates for Hubble observations of the Frontier Fields include observations approximately six months apart. This is the time it takes for the cameras on Hubble to swap positions so that both visible-light data and infrared-light data can be captured from the galaxy cluster field and the adjacent parallel field, as described in this post.

Galaxy Cluster Redshift: 0.545

Redshift measures the lengthening of a light wave from an object that is moving away from an observer. For example, when a galaxy is traveling away from Earth, its observed wavelength shifts toward the red end of the electromagnetic spectrum. The galaxy cluster’s cosmological redshift refers to a lengthening of a light wave caused by the expansion of the universe. Light waves emitted by a galaxy cluster stretch as they travel through the expanding universe. The greater the redshift, the farther the light has traveled to reach us.

Galaxy Cluster Distance: approximately 5 billion light-years

Galaxy Cluster Field Coordinates (R.A., Dec.): 07:17:34.0, +37:44:49.0

Parallel Field Coordinates (R.A., Dec.): 07:17:17.0, +37:49:47.3

Constellation: Auriga

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References to science journal articles:

1: CLASH: Complete Lensing Analysis of the Largest Cosmic Lens MACS J0717.5+3745 and Surrounding Structures

Meet the Frontier Fields: MACS J0416.1-2403

This is the second in a series of posts introducing and providing essential facts about each of the Frontier Fields.

Einstein’s theory of general relativity tells us how the curvature of space causes the path of light from a more distant galaxy to bend as the light passes near a massive cluster of galaxies. The cluster of galaxies acts as a lens, magnifying and distorting the light from the more distant galaxy. This often leads to astronomers observing multiple “lensed images” of the distant galaxy. Compared to other commonly observed galaxy clusters, MACS J0416 is more efficient at producing multiple lensed images of background galaxies1. This means that we expect to find a higher than usual number of images for every galaxy lensed by MACS J0416.

The Massive Cluster Survey (MACS) contains a sample of more than 100 galaxy clusters, measured by the ROSAT telescope to be bright in high-energy X-ray light. The goals of the MACS survey are to categorize and better understand distant massive galaxy clusters.

(Left) Locations of Hubble’s observations of the MACS J0416 galaxy cluster, right, and the nearby parallel field, left, plotted over a Digital Sky Survey (DSS) image. The blue boxes outline the regions of Hubble’s visible light observations, and the red boxes indicate areas of Hubble’s infrared light observations. The 1’ bar, read as one arcminute, corresponds to approximately 1/30 the apparent width of the full moon as seen from Earth. (Right) Archival Hubble image of the MACS J0416 galaxy cluster taken in visible light. Left Credit: Digitized Sky Survey (STScI/NASA) and Z. Levay (STScI). Right Credit: NASA, ESA, and M. Postman (STScI), and the CLASH team.

Left: The locations of Hubble’s observations of the MACS J0416 galaxy cluster (right) and the adjacent parallel field (left) are plotted over a Digitized Sky Survey (DSS) image. The blue boxes outline the regions of Hubble’s visible-light observations, and the red boxes indicate areas of Hubble’s infrared-light observations. A scale bar in the lower left corner of the image indicates the size of the image on the sky. The scale bar corresponds to approximately 1/30th the apparent width of the full moon as seen from Earth. Astronomers refer to this unit of measurement as one arcminute, denoted as 1′.
Right: Hubble’s view of the galaxy cluster is displayed using archival visible-light observations. Deeper Frontier Fields observations of MACS J0416 are ongoing.
Left Credit: Digitized Sky Survey (STScI/NASA), and Z. Levay (STScI).
Right Credit: NASA, ESA, M. Postman (STScI), and the CLASH team.

Estimated Dates of Observations: January-February 2014 and August-September 2014

The planned dates for Hubble observations of the Frontier Fields include observations approximately six months apart. This is the time it takes for the cameras on Hubble to swap positions so that both visible-light data and infrared-light data can be captured from the galaxy cluster field and the adjacent parallel field, as described in this post.

Galaxy Cluster Redshift: 0.396

Redshift measures the lengthening of a light wave from an object that is moving away from an observer. For example, when a galaxy is traveling away from Earth, its observed wavelength shifts toward the red end of the electromagnetic spectrum. The galaxy cluster’s cosmological redshift refers to a lengthening of a light wave caused by the expansion of the universe. Light waves emitted by a galaxy cluster stretch as they travel through the expanding universe. The greater the redshift, the farther the light has traveled to reach us.

Galaxy Cluster Distance: approximately 4 billion light-years

Galaxy Cluster Field Coordinates (R.A., Dec.): 04:16:08.9, -24:04:28.7

Parallel Field Coordinates (R.A., Dec.): 04:16:33.1, -24:06:48.7

Constellation: Eridanus

Related Hubble News:

Looking for Hubble data used by scientists?

References to science journal articles:

1: CLASH: The enhanced lensing efficiency of the highly elongated merging cluster MACS J0416.1-2403