Hubble's exquisite resolution reveals details of astronomical objects that have never before been seen. Often, these observations unmask the complex inner workings that help explain previous puzzles as well as lead to new questions. In the case of the so-called "peculiar" trio of galaxies named Arp 274, however, Hubble's clarity showed the situation to look simpler than suspected. Visual inspection shows some normal beautiful spiral galaxies that we've come to expect. It requires deeper investigation into the positions of these galaxies, as well as an exploration of redshift and Doppler shift, to show that this trio might really be considered strange after all. Join us, as we delve into and behind the picture that you, the public, chose to observe.

Hubble press release:

• Hubble Celebrates the International Year of Astronomy with the Galaxy Triplet Arp 274
• Hubble's Next Discovery, You Decide

Notes

• The initial voting for Hubble's Next Discovery seemed to be overwhelming. We received over 400,000 votes in just a few days. However, one object had garnered a large majority of the votes, and that made us suspicious. It turns out that someone found and exploited a flaw in our voting procedure to cast continuous votes all day long. After we fixed the code and removed the duplicated votes, we ended up with about 140,000 votes cast. The eventual winner did win by a wide margin, but we are fairly confident that the vote reflected the voice of the people.

• Another prominent NASA vote was held on the internet around the same time. NASA asked the public to vote on suggested names, or even suggest a different name, for a new module on the space station. The fans of Stephen Colbert flooded that vote, and his name became the top vote getter. Still, NASA kept the rules flexible enough to choose the name they wanted, and instead named a treadmill after Colbert.

• Yet a third public vote was run by the folks over at NASA Edge. In a takeoff on March Madness, they ran a Mission Madness bracket of 64 NASA missions. Folks were asked to vote on "the greatest NASA mission of all time." The rules allowed for the "vote early, vote often" strategy, and the contest was quickly hijacked by competing factions of internet groups, each vying to make their selected mission win. The truly great NASA missions, such as Apollo 11 and Hubble, didn't stand a chance. The eventual winner was a mission I had never heard about before the contest. Such are the lessons of internet voting.

• Measuring distance in the universe sounds like a basic and simple task. Most folks assume that astronomers know the distance to all astronomical objects. However, that is not at all true. Measuring accurate distances is a fundamental exercise in astronomy, but it is also very difficult. We can measure exact distances across our solar system and out to the nearest stars. Beyond that, we have developed many ways to estimate larger distances based upon the known distances. Each level of distance in the universe generally relies on calibration by distances to closer objects. We call this the "distance ladder," as one must work through the various estimates to climb from stars to star clusters to nearby galaxies to galaxy clusters to galaxies stretching across the universe.

• The image of Arp 274 from the Arp catalog is used in this video podcast with the kind permission of Dr. Halton Arp.

Image Notes

In May 2009, seven astronauts aboard Space Shuttle Atlantis visited the Hubble Space Telescope for a final servicing mission. The drama of a shuttle flight with ambitious and challenging spacewalks that refreshed, repaired, and renewed astronomy's most beloved telescope captured the attention of the world. The underlying reason for such heroic efforts is to enable Hubble to perform new science. Yet, these new capabilities are easily lost in the excitement as the adventure unfolds. This episode aims to remind us of the ultimate value of such an amazing mission.

Hubble press release:

• HubbleSite's Servicing Mission 4 page

Notes

• This episode was filmed prior to the launch of the Servicing Mission 4, but was not posted for viewing until afterwards (we were kinda busy and absorbed in the proceedings during the mission). However, note that the content of the episode is not time sensitive, and speaks to the scientific capabilities that the mission enabled on Hubble. Both new instruments, Wide Field Camera 3 (WFC3) and Cosmic Origins Spectrograph (COS), were successfully installed. In addition, repairs to both the Advanced Camera for Surveys (ACS) and the Space Telescope Imaging Spectrograph (STIS) were also successful.

• The graph labeled "Hubble Survey Discovery Efficiency" is just one way to compare the capabilities of instruments on Hubble. You can find other comparisons, and each will have a slightly different focus and slightly different numbers for the improvements in the new instruments. No one number is definitive, but the sweeping generality that the new instruments enable Hubble to do significant new science can not be argued.

• One can argue that after Servicing Mission 4, Hubble will be the best it has ever been -- not just in terms of the new instruments being better, but also in having more instruments operational. After launch, the telescope was hampered by the flaw in its mirror. Servicing Mission 1 installed COSTAR, the corrective optics, and that instrument has only now been removed during Servicing Mission 4. Hence, for 16 years, COSTAR has taken up an instrument slot, but not provided observing capabilities. If the NICMOS cooling system can be re-started, the observatory will return to its full capabilities with five science instruments.

• Many people have asked: given the improvements that WFC3 and COS will provide over ACS and STIS, why did we need to repair the older instruments? There are several answers. First, there is great value in redundancy. As we will not be able to return to Hubble once the space shuttle fleet is retired, having working backups in the event of a failure is a prudent move. Second, the older instruments are well-calibrated and familiar to scientists. Astronomers may choose to utilize the known instrument to speed-up their research or to retain consistent data processing as earlier observations. Third, the older instruments have different and complementary capabilities to the new instruments. The design of each instrument involves trade-offs, and each is optimized for a particular range of observations. Some observations can best or only be done with the older instruments, as they were optimized for that type of observing.

Image Notes

Space Shuttles Atlantis and Endeavor on the launch pads
Credit: NASA / Dimitri Gerondidakis

Astronauts working on the Hubble Space Telescope
Credit: NASA

Wide Field Camera 3 in the clean room
Credit: NASA

Animation illustrating the wavelengths that WFC3 observes
Credit: Greg Bacon, STScI

Drawing of the protoplanetary disk around the star NGC 1333-IRAS 4B
Credit: NASA/JPL-Caltech/R. Hurt (SSC)

Hubble Ultra Deep Field
Credit: NASA, ESA, S. Beckwith (STScI) and the HUDF Team

Core region of the Antennae Galaxies, 2006
Credit: NASA, ESA, and the Hubble Heritage Team (STScI/AURA)-ESA/Hubble Collaboration
Acknowledgment: B. Whitmore (Space Telescope Science Institute)

Cosmic Origins Spectrograph in the clean room
Credit: NASA

Visible light spectrum diagram
Credit: Philip Ronan

Visible spectrum of hydrogen
Credit: Jan Homann

Visible spectrum of helium
Credit: Jan Homann

Visible spectrum of neon
Credit: Jan Homann

Spectrum of the Sun
Credit: N.A.Sharp, NOAO/NSO/Kitt Peak FTS/AURA/NSF

Animation illustrating COS observations of large scale structure
Credit: Greg Bacon, STScI

Illustration of exploring the cosmic web with COS
Credit: NASA, ESA, A. Feild (STScI)

Hubble after Servicing Mission 3B
Credit: NASA

Here on Earth, the occasional alignments of the Sun and Moon with our planet are greeted with much fanfare. Solar and lunar eclipses are often spectacular sights. However, our solar system undergoes many other more subtle alignments that come under the general name of occultations. From Earth's ever-changing viewpoint, planets can be occulted by our Moon and other moons can be occulted by their planets. Consider the chances for such occultations on Jupiter, which has four of the seven large moons in the solar system. In this episode, we examine Hubble's observations of these otherworldly and somewhat poetic events.

Hubble press release:

• Hubble Catches Jupiter's Largest Moon Going to the 'Dark Side'
• Hubble Spots Rare Triple Eclipse on Jupiter
• Rare Hubble Portrait of Io and Jupiter

Notes

• Eclipses of the Sun can be seen from some point on Earth about every 6 months. Total solar eclipses occur, on average, about once every 18 months. The next total solar eclipse is on July 22, 2009, and is visible in India, through China, and across the southwest Pacific Ocean. A great place to get dates, maps, and other info about solar and lunar eclipses is the NASA Eclipse Web Site

• The similar apparent size on the sky of our Moon and the Sun does not occur for any of the other large moons of the solar system. For Jupiter, Saturn, and Neptune, the Sun is much farther away, and therefore much smaller in their skies. The large moons are similar in size to our Moon, though their orbital distances can be up to five times larger. Still, the combination of sizes and distances always produces moons that are much larger in the sky than the Sun. The closest is Callisto, which appears about 1.5 times the size of the Sun from Jupiter's view. The amazing views of the solar corona we get during total eclipses are a unique treat for our planet.

• In addition to the image from Bernd Nies (link below) used in the video podcast, I found several other very nice images of the Moon occulting Saturn. For example, here are two others by DJLand Job Gehenia

• Hubble has also seen occultations on Saturn. It is interesting that while Jupiter has four large moons, the rest of its moons are rather small. Not so with Saturn. Saturn has one large moon, Titan, and several medium-sized moons as well. These medium-sized moons cast shadows that Hubble can see, setting up this opportunity for an observation of four shadows on Saturn. Another cool observation occurred when Saturn's rings were edge-on to the Sun, and Hubble observed moon shadows across Saturn's rings.

Image Notes

Up until the 1990s, we only knew of the planets in our own solar system. Since then, we have discovered over 300 planets orbiting other stars. However, most of these planets were found when scientists observed the effect of the planet's gravity upon their host stars. Astronomers could not show the world what we wanted most: a visible light picture of a planet around a star like the Sun. That situation changed in November 2008 with a discovery by the Hubble Space Telescope. Join us for the story that begins a new era in our knowledge of planetary systems.

Hubble press release:

• Hubble Directly Observes Planet Orbiting Fomalhaut

Notes

• Note that Hubble's discovery of Fomalhaut b is billed as the "first visible-light snapshot of a planet orbiting another star." It is important to note that the first direct detection of a planet will likely turn out to be the planet known as 2M1207 b. However, the host, 2M1207, is not a full-fledged star, but a brown dwarf (see below). In addition, pictures of three planets around HR 8799, released the same day as the Fomalhaut discovery, were taken in the infrared.

• Let me clarify about 2M1207. It has less than 3% the mass of our Sun, roughly 25 times the mass of Jupiter. That mass places it in the brown dwarf category: large enough to ignite deuterium fusion in its core (thus not a planet), but not large enough for hydrogen fusion (thus not a star). Brown dwarfs glow faintly at formation and then spend the rest of their lives cooling and fading away. Brown dwarfs are generally thought to be those objects with between 15 and 70 times the mass of Jupiter.

• I wanted to make a joke that what the Hubble image of Fomalhaut looked most like is the "Eye of Sauron" from the "Lord of the Rings" movies. However, New Line Cinema did not respond to my requests for permission, and my producer would not let me use the image in the podcast. That joke is one reason why the episode is called "Eye Spy."

• A betting astronomer might have chosen Beta Pictoris as the first star around which a planet would have been seen. We have been getting intriguing evidence that planets should be there for more than a decade. However, since the disk in the Beta Pic system is roughly perpendicular to our line of sight, any planets will travel in front of and behind the star from our point of view. Hence, we could only observe them well during parts of their orbits. Face-on systems, like HR 8799, are much more favorable for direct images.

• If confirmed, the Beta Pictoris planet would indicate that giant planets can form quickly. Beta Pictoris is about 12 million years old. We believe that giant planets must form within the first 10 or so million years of a developing system, as winds and radiation from newborn stars should remove the gas from the system on that timescale. A giant planet needs to accrete some of that gas during its formation, and thus must form in millions of years. In contrast, it is thought that Earth may take as much as a couple hundred million years to form.

Image Notes

Four hundred years ago, Galileo improved the recently invented spyglass, pointed it toward the heavens, and saw things no one else had seen before. In celebration of this anniversary, 2009 has been declared the International Year of Astronomy. As part of the festivities, you have the chance help choose the Hubble telescope's next target. Cast a vote to pick an astronomical object that Hubble has never observed before. What will you choose? What wonders will the telescope reveal? In this episode, you can learn all the details of the selection process. But hurry - you must cast your vote by March 1, 2009.

Hubble press release:

• Hubble's Next Discovery, You Decide

Notes

• Correction: The image in the video podcast that is identified as Star-Forming Region NGC 6634 is mislabelled. It should be NGC 6334. The original press release got the number incorrect because the database it was pulled from was inaccurate. The error was not noticed until after the press release was issued. Since this vote only lasts for a month, we did not go back and correct the video podcast.

• Many folks think that Galileo invented the telescope. That is wrong. The telescope, or spyglass as it was called, was invented in the Netherlands. Several folks could be credited as the inventor, but Hans Lippershey is the most famous one, as he was the first to apply for a patent in 1608. Galileo improved the device from about 3X magnification to about 30X magnification. That and other improvements made the device useful for examining astronomical objects. The word "telescope" was not coined until about 1612.

• The International Year of Astronomy has adopted a motto of "The Universe: Yours to Discover." Many events designed to help you learn or re-learn the wonders of the cosmos are occurring worldwide, with special emphasis on enabling as many people as possible to look through a telescope. To look for events in your area, try the International IYA Web site, the US IYA Web site, or the NASA IYA Web site.

• The low resolution black-and-white images for the candidate objects are from the Digitized Sky Survey, or DSS. Astronomers use DSS images like these to see previews of any point in the sky, in advance of taking observations with Hubble or other telescopes. The exact positioning and orientation of the telescope are programmed in advance to optimize the precious observing time. For Hubble, observing commands are uploaded about 11 days in advance. The old idea of an astronomer adjusting the telescope on the fly is just that -- an old idea.

• Better images of the candidate objects can be found elsewhere on the internet. Type any object's name into an image search engine and you will find several that are higher in resolution and better in color. We chose to use only the DSS images so that each object would be presented in the same manner, and none would get an advantage due to different image sources. Just remember, no matter how good an image you may find out there, Hubble's image will be better.

Image Notes

Einstein's theory of general relativity says that the presence of matter warps the space around it. The more matter there is, the stronger the warp. For really strong distortions of space-time, like black holes, the warping acts like a lens and markedly changes the path of light that passes through it. Such gravitational lenses have been found, and astronomers can use them to study very distant and very faint galaxies. Join us and see how the combination of a huge galaxy cluster and the observations from two space telescopes enable study of a galaxy whose light would otherwise be unobservable.

Hubble press release:

• Astronomers Find One of the Youngest and Brightest Galaxies in the Early Universe

Notes

• The title of this video podcast, "Through a Lens, Brightly" plays off the familiar phrase "through a lens, darkly," which is a slightly shifted version of the phrase "through a glass, darkly." Wikipedia reports that the phrase originally comes from the New Testament and is taken to mean that we have an imperfect view of our world and ourselves. The "glass" in the original version of the phrase is said to be a mirror (i.e., a looking glass), and not a glass lens. Hence, the shifted version that I have used, in order to evoke the idea of a gravitational lens, is a misinterpretation of the original. However, since Hubble uses many mirrors and lenses in observing the universe, one could come up with some weasel excuse as to why it is appropriate. One could, but not me. It just sounded cool.

• The scientific visualization of a black hole passing through Baltimore's Inner Harbor was done with software graciously provided to me by Brian McLeod of Harvard University. The software accurately calculates the deviation of light as it bends around a point-mass black hole. Folks often ask the size of the black hole, but I don't truly know. The software allows me to specify the size of the ring in pixels, without reference to the mass of a black hole needed to produce that large of a ring. For Brian's lensed castle image, he states the mass required as being about the mass of Saturn. For the Baltimore image, the effect is bigger and the mass should be a bit larger. Perhaps Jupiter's mass would be a decent estimate.

• Almost all of the gravitationally lensed arcs seen in the galaxy cluster Abell 1689 are short segments of circles centered on the mass of the cluster. We call them "tangential arcs," and they are the dominant type of lensed arcs seen. However, Abell 1689 is massive enough that "radial arcs," which extend out along lines from the center, can be seen as well. One radial arc can be seen at about the eight o'clock position, below and to the left of the central galaxy. In most galaxy clusters, these radial arcs are too faint or too small or too close to the central galaxy to be seen.

• Gravitational lensing can produce multiple lensed images of the same object in the sky. Light from the object can reach us by taking multiple routes through the distorted space-time of the gravitational lens. Since these routes are of different lengths, light takes different amounts of time to travel along them. Hence, each lensed image shows the object at a slightly different time. In some lenses, we can see a change happen in one lensed image that doesn't show up until days, months, or even years later in another lensed image of that same object.

Image Notes

]]> http://imgsrc.hubblesite.org/hu/explore_astronomy/hubbles_universe_unfiltered/db#5-video/x-msvideo-640 http://hubblesite.org/explore_astronomy/hubbles_universe_unfiltered/5 Tue, 03 Feb 2009 00:00:00 -0500 outreach@stsci.edu

A third red spot appears in
Jupiter's atmosphere.

The most prominent feature on the planet Jupiter is a large, ruddy oval that is simply called the Great Red Spot (GRS). The GRS is a giant storm in Jupiter's atmosphere that has been remarkably stable. In fact, it may have been observed as early as the 1660s. During the intervening centuries, the GRS was not just the largest, but also the only red spot ever seen on Jupiter. That situation changed when a formerly white storm turned brown in late 2005, and then red in early 2006. And yet another red spot appeared in spring 2008. After such consistency for hundreds of years, Jupiter appears to be breaking out in red spots. Join us for a look at this historic case of planetary measles.

Hubble Press Release:

• Hubble Snaps Baby Pictures of Jupiter's "Red Spot Jr."
• New Red Spot Appears on Jupiter
• Three Red Spots Mix it Up on Jupiter

Notes

• 

  A great drawing of Jupiter (right) with something that looks an awful lot like the Great Red Spot was published by Giovanni Cassini in the "Journal des Scavans" (the earliest scientific journal published) in 1677. This spot was observed until the early 1700s. However, the observational record is continuous from the present day back to only about 1830. We do not know whether the spot observed by Cassini is the same spot that we call the Great Red Spot today.

• Some Hubble color images of Jupiter show a blue tint on one side of the planet and a red tint on the other side. See, for example, this image from 1994: The Giant Planet Jupiter

  The reason for the tints is that Jupiter rotates very quickly, in about ten hours. Hubble does not take color photos, but rather creates color from separate red, green, and blue exposures. Between the time that the red exposure was taken and the blue exposure was taken, the planet rotated a small amount. When the exposures were aligned and combined, a small part of Jupiter only appears in the red exposure (the red tint) and a small part only appears in the blue exposure (the blue tint). This combination of exposures also makes Jupiter appear more oval-shaped than it really is.

• The spot that we call "Red Jr." formed in the year 2000, but it did not turn red until early 2006. Astronomers know it by the simpler name, "Oval BA." It arose from the merger of Ovals FA, DE, and BC during 1998-2000. In late 2005, Oval BA was observed to turn brown, and by February of 2006, it was the same reddish color as the Great Red Spot. That is when folks started calling it Red Jr. Incidentally, some astronomers don't like the nickname of Red Jr., and one referred to it in a NASA press release as the "not-so-Great Red Spot."

• The "Baby Red Spot," as we call it, is a nickname for the South Tropical Little Red Spot. Subsequent observations to the ones shown in the video podcast show that the storm was disrupted by its encounter with the Great Red Spot and did not re-form. Some "probable" remnants remained together for several weeks, but at a much smaller size than when the storm was red. This smallest of red spots only lasted for about 3 months, and raises the intriguing possibility that there could be more to come.

Image Notes

Hurricane Isabel (2003) over the Atlantic Ocean
Credit: Jeff Schmaltz, MODIS Rapid Response Team, NASA/GSFC

Eye of Hurricane Isabel (2003) from the International Space Station
Credit: NASA

Hurricane Isabel (2003) off the Outer Banks
Credit: Jacques Descloitres, MODIS Rapid Response Team, NASA/GSFC

Hurricane Isabel (2003) from the International Space Station
Credit: NASA

Jupiter's Great Red Spot from Voyager 2
Credit: NASA/JPL-Caltech

Earth, Western Hemisphere
Credit: NASA, GSFC, et al. (follow link for complete credits)

Jupiter from Hubble
Credit: Reta Beebe, Amy Simon (New Mexico State Univ.), and NASA

Great Red Spot Montage
Credit: The Hubble Heritage Team (STScI/AURA/NASA) and Amy Simon (Cornell U.)

Great Red Spot and Red Jr. - April 25, 2006
Credit: NASA, ESA, I. de Pater, and M. Wong (UC Berkeley)

Jupiter Timelapse Sequence from Cassini
Credit: NASA/JPL/University of Arizona

Three Red Spots on Jupiter
Credit: M. Wong and I. de Pater (UC Berkeley)

Three Red Spots Sequence, May to July 2008
Credit: NASA, ESA, A. Simon-Miller (GSFC), N. Chanover (NMSU), and G. Orton (JPL)

Jupiter in infrared with Great Red Spot and Red Jr.
Credit: Gemini Observatory/AURA, Chris Go

]]> http://imgsrc.hubblesite.org/hu/explore_astronomy/hubbles_universe_unfiltered/db#4-video/x-msvideo-640 http://hubblesite.org/explore_astronomy/hubbles_universe_unfiltered/4 Mon, 05 Jan 2009 00:00:00 -0500 outreach@stsci.edu

NASA's Hubble Space Telescope
is back in business.

On September 27, 2008, NASA was two weeks away from a space shuttle mission to upgrade and repair the Hubble Space Telescope. That night, Hubble suffered an electronics failure and went into its protective safe mode. The servicing mission was soon put on hold as engineers scrambled to diagnose the problem and activate hardware that had not been used in eighteen years. Managers also had to consider whether the failure left Hubble without a backup for a critical system. Now, a month later, Hubble's vision has been restored, and the servicing mission, while delayed, has been expanded to include a complete fix for the problems encountered.

Hubble Press Release:

• Hubble Scores a Perfect Ten

Notes

• The next servicing mission to Hubble is commonly referred to as Servicing Mission 4, or SM4. It will be, however, the fifth servicing mission to Hubble. The third servicing mission was split into two pieces: SM3a occurred in 1999, while SM3b took place in 2002. The numbering of the servicing missions has stuck with the original plans, and was not updated to reflect the true count of the missions.

• In contrast with Hubble's low Earth orbit of about 600 km above the planet's surface, most communications satellites reside much higher in the sky. Communications satellites are generally in geosynchronous orbits, an orbit where the orbital period matches Earth's rotational period. Satellites in these orbits stay over the same spot on Earth and can therefore be found at the same position in the sky all the time. This feature allows you to point your satellite dish once and leave it pointed. The height of a geosynchronous orbit is about 36,000 km above Earth's surface. That is 60 times the height of Hubble's orbit.

• The September 2008 rollout of space shuttles Atlantis and Endeavor was not the first time that two shuttles had been at their launch pads at the same time. It happened as recently as July 2001, and there have been about 15 more occasions with two shuttles on launch pads simultaneously. Coincidentally, when Discovery launched Hubble into space on April 24, 1990, Columbia was also on the launch pad. You can see Columbia in the foreground of the Hubble launch picture noted below.

• The failure in Hubble's electronics occurred in the CU/SDF (Control Unit / Science Data Formatter) which is one part of the SIC & DH (Science Instrument Command and Data Handler). For simplicity, we did not differentiate between the component and the overall unit. There are two CU/SDF units on the SIC & DH unit, and we call one CU/SDF side A, and the other side B. More details on all the events can be found in the NASA SM4 press release archive at: http://www.nasa.gov/mission_pages/hubble/servicing/SM4/news/

• An astute viewer pointed out that while there are four main bolts holding the SIC & DH unit, there are also several other bolts or screws that need to be unfastened during the spacewalk. He suggested that the total number was around ten. Still, this is much, much less than the more than 100 screws that will need to be taken care of on a different spacewalk repair during Servicing Mission 4. Thanks for the correction.

Image Notes

Crew of Shuttle Mission STS-125
Credit: NASA

STS-125 Crew Training Underwater
Credit: NASA

Two Shuttles on Launch Pads with Rainbow, September 20, 2008
Credit: NASA/Troy Cryder

Shuttle Mission STS-31 Launch, Carrying Hubble into Orbit
Credit: NASA

Hubble After Servicing Mission 3B
Credit: NASA

Change-out of WFPC During Hubble Servicing Mission 1
Credit: NASA

Hubble Battery Module Assembly in Bay 2
Credit: NASA

Science Instrument Command and Data Handler
Credit: NASA

Interacting Galaxies Arp 147
Credit: NASA, ESA, and M. Livio (STScI)

]]> http://imgsrc.hubblesite.org/hu/explore_astronomy/hubbles_universe_unfiltered/db#3-video/x-msvideo-640 http://hubblesite.org/explore_astronomy/hubbles_universe_unfiltered/3 Mon, 17 Nov 2008 00:00:00 -0500 outreach@stsci.edu

The Coma Cluster of galaxies,
one of the densest known galaxy
collections in the universe.

The Coma Cluster of Galaxies is one of the richest collections of galaxies in the nearby universe. Several thousand galaxies are gathered together by their mutual gravity, making it an ideal location for observing the full diversity of galaxies in the universe. While ground-based telescopes can record the wide-angle view, Hubble's keen eye captures the details of not only spirals and ellipticals in the cluster, but also galaxies a billion light-years beyond. Join us, as we journey into the Coma Cluster and explore its rich landscape of galaxies.

Hubble press release:

• Hubble's Sweeping View of the Coma Cluster of Galaxies

Notes

• Johannes Hevelius' drawing of the Bootes, Coma Berenices, and Corona constellations is actually backward from the way we see them in the sky. Back in the day, constellation figures were drawn on the outside of a sphere, with the Earth located at the center of the sphere. Hence, the artist would have to flip the locations of the stars to present the correct orientation. The constellations on the ceiling of Grand Central Station in New York City used a similar ancient source. Thus, thousands of commuters look up each day and see the constellations backward.

• The Coma Cluster contains several thousand galaxies, has a diameter of roughly 15 million light-years, and is located about 300 million light-years away. Contrast that with our Local Group of galaxies, which has only two large galaxies, one medium-sized galaxy, and about three dozen small galaxies. The Local Group covers perhaps 3 million light-years. You can see that our Milky Way Galaxy does not live in one of the big cities of the universe. We are located in more of a small town, as galaxy collections go.

• The nearest large cluster of galaxies is the Virgo Cluster. It is about 50 million light-years away and contains a couple thousand galaxies. At this distance, however, we're actually too close to get a good look. The galaxies of Virgo appear to us to be spread across a large swath of the sky, tens of degrees wide. Hence, when we look at pictures of the Virgo Cluster, we don't see the dense collection of galaxies that it really is. It's like we can see the trees well, but don't get a good view of the whole forest.

• The movie that zooms into the Coma Cluster starts with a view that is about 20 degrees wide and ends with a view about one arc-minute wide. Since there are 60 arc minutes in a degree, that makes for about a 1200x zoom. For comparison, most cameras have less than a 10x zoom. To accomplish this extreme zoom, the animator used several different images at different resolutions and cross-faded between them during the zoom.

Image Notes

Coma Berenices constellation
Credit: A. Fujii

Gold octadrachm issued by Ptolemy III
Credit: Marie-Lan Nguyen and British Museum, London, United Kingdom

Bust of Queen Berenice II
Credit: Bibi Saint-Pol and Glyptothek, Munich, Germany

Constellations Bootes, Coma Berenices, and Corona
Credit: Johannes Hevelius, Uranographia, 1690

Wide-Field Image of the Coma Cluster of Galaxies
Credit: ESA/Hubble and Digitized Sky Survey
Acknowledgement: D. De Martin

Hubble Image of the Coma Cluster of Galaxies
Credit: NASA, ESA, and the Hubble Heritage Team (STScI/AURA)
Acknowledgment: D. Carter (Liverpool John Moores University) and the Coma HST ACS Treasury Team

Zoom Into the Coma Cluster of Galaxies
Credit: NASA, ESA, and G. Bacon (STScI)

]]> http://imgsrc.hubblesite.org/hu/explore_astronomy/hubbles_universe_unfiltered/db#2-video/x-msvideo-640 http://hubblesite.org/explore_astronomy/hubbles_universe_unfiltered/2 Tue, 04 Nov 2008 00:00:00 -0500 outreach@stsci.edu

Interacting galaxies morph into
wondrous new shapes.

Hubble celebrated its 18th anniversary by releasing a huge image gallery of interacting galaxies. Such galaxies pass close enough to each other that their mutual gravity can stretch and distort their shapes. Eventually, interacting galaxies merge together to form a single larger galaxy. However, since these interactions can take billions of years, how do we study them? And how do we make sense of the variety of strange shapes seen in these Hubble images?

Hubble press release:

• Cosmic Collisions Galore!

Notes

• Hubble was launched into orbit on April 24, 1990, aboard the space shuttle Discovery. However, there is a lot more to its history than just 18 years (so far) of cutting edge science. Take a look at Hubble Essentials for more of the story.

• Here are the numbers behind the size vs. distance comparison, using baseballs as stars.

  Let's take the stars first. The Sun is about 870,000 miles (1.4 million km) in diameter. The star Alpha Centauri is about 4.25 light-years away. A light-year is the distance light travels in one year at the speed of about 186,000 miles (300,000 km) per second, roughly 5.9 trillion miles (9.5 trillion km). That makes Alpha Centauri about 25 trillion miles (40 trillion km) distant. Hence the distance to Alpha Centauri is about 28 million times larger than the diameter of the Sun. I say "millions" in the podcast just to make it easy to remember.

  Since a baseball is about 3 inches (7.6 cm) in diameter, a scale model of our Sun and Alpha Centauri would be two baseballs separated by 28 million times 3 inches (7.6 cm). Do the math, and you get about 1,300 miles (2,092 km). The distance between Baltimore (where the Space Telescope Science Institute is located) and Houston is about 1,250 miles (2,011 km). Not exact, but close enough for a good comparison.

• The scientific visualization of the galaxy collision is based on a supercomputer simulation by two astronomers. The galaxies are represented in the computer by several hundred thousand particles that interact via the equations of gravity and hydrodynamics. The output of the simulation is just lists of positions, velocities, densities, temperatures, etc. for all the particles at each timestep of the simulation. Those data are then turned into pictures using custom visualization software designed to represent the physics of the simulation accurately. Commercial software, such as that producing the latest Hollywood computer graphics, is generally not that useful for scientific visualization, as it is optimized to produce fantasy instead of reality.

Image Notes

Hubble from Shuttle Mission STS-109
Credit: NASA

Orion star field
Credit: A. Fujii

Drawing used to represent the Milky Way
Credit: NASA, ESA, A. Feild (STScI)

Andromeda Galaxy
Credit: Bill Schoening, Vanessa Harvey/REU program/NOAO/AURA/NSF

Interacting Galaxies: Gallery and individual images of Arp 148, ESO 077, ESO 148, NGC 6240, UGC 09618, VV 705
Credit: NASA, ESA, the Hubble Heritage (STScI/AURA)-ESA/Hubble Collaboration, and A. Evans (University of Virginia, Charlottesville/NRAO/Stony Brook University)

Galaxy Collision: Simulation vs Observations
Credit: NASA, ESA, and F. Summers (STScI) Simulation Data: Chris Mihos (Case Western Reserve University) and Lars Hernquist (Harvard University)

]]> http://imgsrc.hubblesite.org/hu/explore_astronomy/hubbles_universe_unfiltered/db#1-video/x-msvideo-640 http://hubblesite.org/explore_astronomy/hubbles_universe_unfiltered/1 Fri, 25 Jul 2008 00:00:00 -0400 en-us http://hubblesite.org/explore_astronomy/hubbles_universe_unfiltered/db/ outreach@stsci.edu Mon, 31 Jan 2011 00:00:00 -0500