Activity within the jet from NGC 3852 imaged by Hubble. Credit: NASA, ESA, and E. Meyer (STScI).
Even the Empire’s planet-blasting battle station has nothing compared to the immense energy being fired from the heart of NGC 3862, a supermassive black hole-harboring elliptical galaxy located 300 million light-years away.
And while jets of high-energy plasma coming from active galactic nuclei have been imaged before, for the first time activity within a jet has been observed in optical wavelengths, revealing a quite “forceful” collision of ejected material at near light speeds.
Using archived image data acquired by Hubble in 1994, 1996, and 2002 combined with new high-resolution images acquired in 2014, Eileen Meyer at the Space Telescope Science Institute (STScI) in Baltimore, Maryland identified movement in visible clumps of plasma within the jet emitted from the nucleus of NGC 3862 (aka 3C 264). One of the outwardly-moving larger clumps could be seen gaining on a slower, smaller one in front of it and the two eventually collide, creating a shockwave that brightens the resulting merged mass dramatically.
Such a collision has never been witnessed before, and certainly not thousands of light-years out from the central supermassive black hole.
Close-up image of the jet as seen in 2014. Credit: NASA, ESA, and E. Meyer (STScI).
“Something like this has never been seen before in an extragalactic jet,” Meyer said. “This will allow us a very rare opportunity to see how the kinetic energy of the collision is dissipated into radiation.”
Jets like this are created when infalling material around an active (that is, “feeding”) supermassive black hole gets caught up in its powerful spinning and twisting magnetic fields. This accelerates the material even further and, rather than permitting it to descend down past the black hole’s event horizon, results in it getting shot out into space at velocities close to the speed of light.
When material approaches the black hole in even amounts the jets are fairly consistent. But if the inflow is uneven, the jets can consist of clumps or knots traveling outward at different speeds.
Because of the motion of the galaxy itself related to our own, the speed of the clumps can appear to actually move faster than the speed of light, especially when – as seen in NGC 3862 – a large clump has already paved the way within the jet. In reality the light speed limit has not been broken, but the apparent superluminal motion so far from the SMBH indicates that the material was ejected extremely energetically.
It’s expected that the combined clusters of material will continue to brighten over the next several decades.
You can see a video of the observations below, and watch a Google+ Hangout with Hubble team members about these observations here.
Latest image released by NASA of the spatter of white spots in the 57-mile-wide crater on the dwarf planet Ceres. Scientists with the Dawn mission believe they're highly reflective material, likely ice. Credit: NASA/JPL-Caltech/UCLA/MPS/DLR/IDA
The latest views of Ceres’ enigmatic white spots are sharper and clearer, but it’s obvious that Dawn will have to descend much lower before we’ll see crucial details hidden in this overexposed splatter of white dots. Still, there are hints of interesting things going on here.
Comparison of the most recent photos of the white spots taken Dawn’s current 4,500 miles vs. 8,400 miles on May 4. Credit: NASA/JPL-Caltech/UCLA/MPS/DLR/IDA
The latest photo is part of a sequence of images shot for navigation purposes on May 16, when the spacecraft orbited 4,500 miles (7,200 km) over the dwarf planet. Of special interest are a series of troughs or cracks in Ceres crust that appear on either side of the crater housing the spots.
While the exact nature of the spots continues to baffle scientists, Christopher Russell, principal investigator for the Dawn mission, has narrowed the possibilities: “Dawn scientists can now conclude that the intense brightness of these spots is due to the reflection of sunlight by highly reflective material on the surface, possibly ice.”
The bright material in both photos was excavated from below the surface and deposited nearby by a 2008 impact that dug a crater about 26 feet (8 meters) in diameter. The extent of the bright patch was large enough for the Compact Reconnaissance Imaging Spectrometer for Mars, an instrument on NASA’s Mars Reconnaissance Orbiter, to obtain information confirming it as water ice. Credit: NASA/JPL-Caltech/University of Arizona
We’ve seen ice exposed by meteorite / asteroid impact before on Mars where recent impacts have exposed fresh ice below the surface long hidden by dust. In most cases the ice gradually sublimates away or covered by dust over time. But if Ceres’ white spots are ice, then we can reasonably assume they must be relatively new features otherwise they would have vaporized or sublimated into space like the Martian variety.
NASA’s Hubble Space Telescope took these images of the asteroid 1 Ceres over a 2-hour and 20-minute span, the time it takes the Texas-sized object to complete one quarter of a rotation. The observations were made in visible and in ultraviolet light. Hubble took the snapshots between December 2003 and January 2004. Credit: NASA, ESA, J. Parker, P. Thomas and L. McFadden
Much has been written – including here – that these spots are the same as those photographed in much lower resolution by the Hubble Space Telescope in 2004. But according the Phil Plait, who writes the Bad Astronomy blog, that’s false. He spoke to Joe Parker, who was part of the team that made the 2004 photos, and Parker says the Dawn spots and Hubble spots are not the same.
Could the spots have formed post-2004 or were they simply too small for Hubble to resolve them? That seems unlikely. The chances are slim we’d just happen to be there shortly after such a rare event occurred? And what happened to Hubble’s spot – did it sublimate away?
Video compiled from Dawn’s still frames of Ceres by Tom Ruen. Watch as the spots continue to reflect light even at local sunset.
Watching the still images of Ceres during rotation, it’s clear that sunlight still reflects from the spots when the crater fills with shadow at sunset and sunrise. This implies they’re elevated, and as far as I can tell from the sunrise photo (see below), the brightest spots appear to shine from along the the side of a hill or mountain. Could we be seeing relatively fresh ice or salts after recent landslides related to impact or tectonic forces exposed them to view?
Single from from the video shows the white spots shortly after sunrise. The brightest appear to be located on a central mountain peak. It’s unclear if the pair of spots below the bright pair are situated on a rise or the flat floor. Credit: NASA
Let’s visit another place in the Solar System with an enigmatic white spot, or should I say, white arc. It’s Wunda Crater on Uranus’ crater-blasted moon Umbriel. The 131-mile-wide crater, situated on the moon’s equator, is named for Wunda, a dark spirit in Aboriginal mythology. But on its floor is a bright feature about 6 miles (10 km) wide. We still don’t know what that one is either!
The moon Umbriel, 727 miles in diameter, with Wunda Crater and its bright internal ring of unknown origin. The moon’s equator is vertical in this photo. Credit: NASA
Andromeda's halo is gargantuan. Extending millions of light years, if we could see in our night sky it would be 100 times the diameter of the Moon or 50 degrees across! Credit: NASA
The merger of the Milky Way and Andromeda galaxy won’t happen for another 4 billion years, but the recent discovery of a massive halo of hot gas around Andromeda may mean our galaxies are already touching. University of Notre Dame astrophysicist Nicholas Lehner led a team of scientists using the Hubble Space Telescope to identify an enormous halo of hot, ionized gas at least 2 million light years in diameter surrounding the galaxy.
The Andromeda Galaxy is the largest member of a ragtag collection of some 54 galaxies, including the Milky Way, called the Local Group. With a trillion stars — twice as many as the Milky Way — it shines 25% brighter and can easily be seen with the naked eye from suburban and rural skies.
Six examples of quasars photographed with the Hubble. Quasars are distant, brilliant sources of light, believed to occur when a massive black hole in the center of a galaxy feeds on gas and stars. As the black hole consumes the material, it emits intense radiation, which is then detected as a quasar. Lehner and team measured Andromeda’s halo by studying how its gas affected the light from 18 different quasars. Credit: NASA/ESA
Think about this for a moment. If the halo extends at least a million light years in our direction, our two galaxies are MUCH closer to touching that previously thought. Granted, we’re only talking halo interactions at first, but the two may be mingling molecules even now if our galaxy is similarly cocooned.
Lehner describes halos as the “gaseous atmospheres of galaxies”. Despite its enormous size, Andromeda’s nimbus is virtually invisible. To find and study the halo, the team sought out quasars, distant star-like objects that radiate tremendous amounts of energy as matter funnels into the supermassive black holes in their cores. The brightest quasar, 3C273 in Virgo, can be seen in a 6-inch telescope! Their brilliant, pinpoint nature make them perfect probes.
To detect Andromeda’s halo, Lehner and team studied how the light of 18 quasars (five shown here) was absorbed by the galaxy’s gas. Credit: NASA
“As the light from the quasars travels toward Hubble, the halo’s gas will absorb some of that light and make the quasar appear a little darker in just a very small wavelength range,” said J. Christopher Howk , associate professor of physics at Notre Dame and co-investigator. “By measuring the dip in brightness, we can tell how much halo gas from M31 there is between us and that quasar.”
Astronomers have observed halos around 44 other galaxies but never one as massive as Andromeda where so many quasars are available to clearly define its extent. The previous 44 were all extremely distant galaxies, with only a single quasar or data point to determine halo size and structure.
Andromeda’s close and huge with lots of quasars peppering its periphery. The team drew from about five years’ worth of observations of archived Hubble data to find many of the 18 objects needed for a good sample.
This illustration shows a stage in the predicted merger between our Milky Way galaxy and the neighboring Andromeda galaxy, as it will unfold over the next several billion years. In this image, representing Earth’s night sky in 3.75 billion years, Andromeda (left) fills the field of view and begins to distort the Milky Way with tidal pull. Credit: NASA; ESA; Z. Levay and R. van der Marel, STScI; T. Hallas; and A. Mellinger
The halo is estimated to contain half the mass of the stars in the Andromeda galaxy itself, in the form of a hot, diffuse gas. Simulations suggest that it formed at the same time as the rest of the galaxy. Although mostly composed of ionized hydrogen — naked protons and electrons — Andromeda’s aura is also rich in heavier elements, probably supplied by supernovae. They erupt within the visible galaxy and violently blow good stuff like iron, silicon, oxygen and other familiar elements far into space. Over Andromeda’s lifetime, nearly half of all the heavy elements made by its stars have been expelled far beyond the galaxy’s 200,000-light-year-diameter stellar disk.
You might wonder if galactic halos might account for some or much of the still-mysterious dark matter. Probably not. While dark matter still makes up the bulk of the solid material in the universe, astronomers have been trying to account for the lack of visible matter in galaxies as well. Halos now seem a likely contributor.
The next clear night you look up to spy Andromeda, know this: It’s closer than you think!
This NASA/ESA Hubble Space Telescope image of the cluster Westerlund 2 and its surroundings has been released to celebrate Hubble’s 25th year in orbit and a quarter of a century of new discoveries, stunning images and outstanding science. Credit: NASA, ESA, the Hubble Heritage Team (STScI/AURA), A. Nota (ESA/STScI), and the Westerlund 2 Science Team.
Images from space don’t get any prettier than this. A new image from the Hubble Space Telescope was released today to commemorate a quarter century of exploring the Solar System and beyond since the launch of the telescope on April 24, 1990. It shows a giant cluster of about 3,000 stars called Westerlund 2, located 20,000 light-years away from Earth in the constellation Carina. NASA describes the new image as a “brilliant tapestry of young stars flaring to life resemble a glittering fireworks display.”
The Hubble Teams are giving away a few “gifts” to everyone to celebrate this silver anniversary — see below!
“Hubble has completely transformed our view of the universe, revealing the true beauty and richness of the cosmos” said John Grunsfeld, astronaut and associate administrator of NASA’s Science Mission Directorate. “This vista of starry fireworks and glowing gas is a fitting image for our celebration of 25 years of amazing Hubble science.”
The cluster is named after Swedish astronomer Bengt Westerlund who discovered the grouping in the 1960s.
There are anniversary events occurring around the US and the world. Here is a listing of at the Hubble anniversary site, where people can also find science articles, educational resources, downloadable presentations, and more:
And here’s a downloadable 25th anniversary gift for everyone: Hubble is offering a free ebook of 25 of Hubble’s most significant images, which can be found at this link or at iTunes.
See a stunning gallery of all the ‘anniversary’ images that have been released by the Hubble teams over the last 25 years at this Flickr gallery.
And finally, here’s an excellent visualization of a flight to the star cluster Westerlund 2:
Hubble Servicing Mission astronaut training in the water of the Neutral Buoyancy Lab in Houston, Texas, February 2009. Credit and copyright: Michael Soluri.
Photographer Michael Soluri was granted unprecedented access to document the people and events behind the final Hubble Space Telescope Servicing Mission 4, STS-125, which launched in 2009. He has published these images in a new book, “Infinite Worlds: People & Places of Space Exploration.” Soluri has provided Universe Today with an exclusive gallery of images from the book, and also told us about his experiences in being able to follow for three years the behind the scenes lead-up to the mission.
Read his account and see more images below. You can read our full review of Infinite Worldshere.
K. Megan McArthur (PH.D.), the STS-125 Hubble SM4 Robotic Arm engineer during final servicing mission to Hubble, May 2009. Credit and copyright: Michael Soluri.
From a very early age following the space program and over the decades as a documentary photographer on location at various NASA flight centers, I always felt something was missing: an honest, unscripted visual sense of the people behind the scenes that make human and robotic space flight possible.
Yes, it’s always inspiring to experience and photograph a rocket launch with remote equipment or from 3 miles away. However, the access pattern over time has been the same. Writers and photographers herded together into controlled situations that in the end capture the same shot. Given security issues, this is understandable and the results over the decades are predictable.
To achieve the results experienced in Infinite Worlds required earning the trust of both the crew as well as Hubble and shuttle flight management. That trust contributed to being asked by the STS-125 crew to coach them in making better more visually communicative images of their experiences at Hubble. It also enabled me to be a part of and be accepted into the many worlds of that mission during good times and challenging ones.
The edited results comprise my book and exhibitions. Looking back on that journey, I am humbled by the mutual respect and trust extended to me by a remarkable, “made in the USA” labor force that for the most part no longer exists.
— Michael Soluri
Mark Turczyn, Hubble Space Telescope Senior Systems Engineer. In ‘Infinite Worlds’ he said, “”Every time we ran out of time … we created more.” Credit and copyright: Michael Soluri.Office white-board of Mark Turczyn, HST Senior Systems Engineer. Credit and copyright: Michael Soluri.Greg Cecil, a Thermal Protection Systems Technician, replaced and caulked damaged tiles on the cockpit area of the space shuttle. He is currently a middle school science teacher. Credit and copyright: Michael Soluri.Christy Hansen, EVA Task Lead and STS-125 SM4 astronaut Drew Feustel in cargo bay of Atlantis in July 2008. Credit and copyright: Michael Soluri.Four of the “space-walking” astronauts and their mission trainers reviewing one of the tool boxes they will be accessing in the cargo bay of the shuttle during the last service mission to the Hubble Space Telescope. Credit and copyright: Michael Soluri.Mini Power Drill System, designed at NASA Goddard SpaceFlight Center used by astronauts on the final mission to the Hubble Space Telescope, May 2009. Credit and copyright: Michael Soluri.The astronaut EVA crew of Hubble SM4 – last servicing mission to the Hubble by a space shuttle crew. From left to right: John Grunsfeld, Drew Feustel, Michael Good, and Mike Massimino. Image taken at Goddard Space Flight Center, July 2008. Credit and copyright: Michael Soluri.John Grunsfeld, just before entering shuttle Atlantis for his fifth mission in space and his third to the Hubble Space Telescope. Grunsfeld wrote “Climbing Mountains” for Infinite Worlds. Credit and copyright: Michael Soluri.Atlantis just after roll out and pad lock down at Pad 39A at Kennedy Space Center for the STS-125 Hubble Servicing Mission. March 31, 2009. Credit and copyright: Michael Soluri.Jill McGuire, Manager, Hubble SM4 Crew Aids and Tools, in Mission control in Houson during EVA 4, May 2009. Credit and copyright: Michael Soluri.Self Portrait by John Grunsfeld and shuttle Atlantis on the Hubble Space Telescope — orbiting Earth. Image courtesy Michael Soluri.
Soluri will give a presentation and do a book signing on April 11, 2015 at the Smithsonian’s Hirshhorn Museum & Sculpture Garden. Soluri will be joined by four individuals who played key roles in Service Mission SM4: astronaut Scott Altman, the STS-125 shuttle commander; David Leckrone, senior project scientist; Christy Hansen, EVA spacewalk flight controller and astronaut instructor; and Hubble systems engineer Ed Rezac. More information on that event can be found here.
Infinite Worlds - People & Places of Space Exploration: by Michael Soluri, Foreword by John Glenn. Cover image courtesy of Michael Soluri and Simon & Schuster.
On April 24, 1990, the Hubble Space Telescope was launched from Kennedy Space Center into low Earth orbit. Hubble was the first telescope designed to operate in space, so it was able to avoid interference from Earth’s atmosphere – an inconvenience that had limited astronomers since they first looked up to the skies. However, scientists quickly realized that something was wrong; the images were blurry. Despite being among the most precisely ground instruments ever made, the primary mirror in the Hubble was about 2,200 nanometers too flat at the perimeter (for reference, the width of a typical sheet of paper is about 100,000 nanometers). Luckily, there was a solution.
Hubble was designed to be serviced in space. As NASA writes on the telescope’s website, “a series of small mirrors could be used to intercept the light reflecting off the mirror, correct for the flaw, and bounce the light to the telescope’s science instruments.” A series of five missions lasting from 1993 to 2009 was devised to correct the mirror and perform various upgrades. Despite being the first of their kind, the missions were declared a resounding success – and they enabled the Hubble Space Telescope to remain operational to this day. Many of Hubble’s images are among the most incredible ever produced by mankind, yet few people know anything about the remarkable men and women who made them possible.
ohn Grunsfeld, just before entering shuttle Atlantis for his fifth mission in space and his third to the Hubble Space Telescope. Grunsfeld wrote “Climbing Mountains” for Infinite Worlds. Credit and copyright: Michael Soluri.
Infinite Worlds: People & Places of Space Exploration, the latest book from photographer Michael Soluri, documents the people who worked on the last of these repair missions, STS-125 (also known as Hubble Space Telescope Servicing Mission 4 [HST-SM4]). The nearly two-week journey aboard Space Shuttle Atlantis saw the successful installation of two new instruments and the repair of two others. Like the four other shuttle crews that came before them, the men and women aboard STS-125 enabled Hubble to see deeper and farther into the past than ever before.
Michael Massimino, a veteran of the earlier STS-109 mission, is one of these people. Massimino and Soluri became fast friends after a chance encounter, when Soluri asked: “What is the quality of light really like in space?” Following their discussion, Massimino asked Soluri to teach him and the rest of the crew how to take photographs that would better communicate their experiences in space. Astronauts are always taking pictures, but the lighting in space is, understandably, not always ideal. Like Soluri himself in Infinite Worlds, the astronauts repairing Hubble were looking for better ways to communicate the beauty of space travel through photography.
Soluri was granted unprecedented access to document the people and events behind the mission throughout a period of more than four years. The photographs in the book “give deserved attention to a few of the many thousands of people who worked on the Space Shuttle and Hubble Space Telescope programs,” reads an inspiring foreword by John Glenn, the first American to orbit the Earth. Infinite Worlds reveals a side of space travel that most of us would never otherwise see, including the training sessions, tools, and trials that make success possible. NASA, notorious for keeping their employees tightly scripted and inaccessible, rarely grants such access – and with the closing of the Space Shuttle Program in 2011, such intimacy may never be seen again.
Jill McGuire, Manager, Hubble SM4 Crew Aids and Tools, in Mission control in Houson during EVA 4, May 2009. Credit and copyright: Michael Soluri.
Science is a cooperative discipline, but most people only ever see the results. The tireless work of thousands of individuals is often taken for granted and forgotten. Although many people still hold the false idea that scientific accomplishments are made by individual geniuses working in an armchair, now more than ever before we are entering an age where science is performed by large teams working cooperatively. To mention just one example, CERN hosts scientists of more than 100 nationalities. As Jill McGuire, a manager at Goddard Space Flight Center, writes about the field in the book, “the best way to move forward in the business was to get my hands dirty by working with the skilled machinists and technicians in the branch to learn everything I could.”
Infinite Worlds grants readers an exhilarating glimpse into this cooperative world. One particularly inspiring section follows the immediate buildup to the launch of STS-125. The transcript of the pre-launch quality check is paralleled by images of the situation as it happened. Black and white photographs from both cockpit and control room highlight the tension behind “the most risky thing NASA does,” according to Space Shuttle Launch Director Michael Leinbach. He continues, “they were real people with real families, real children, real lives.” Infinite Worlds reminds us of this: the work behind every scientific breakthrough is not magic, but rather the result of talented and dedicated individuals.
As we approach the 25th anniversary of the Hubble Space Telescope’s launch and look to the future, a book like Infinite Worlds is more relevant now than ever before. The beautiful photographs in Soluri’s book tell two kindred stories: not only the heroic report of repairing a multi-billion dollar piece of equipment, but also a unique glimpse at the inspiring men and women who made it all possible. Whether humanity’s next missions are to Mars, Europa, or elsewhere, one thing will remain constant – we will only reach the stars through the work of exceptional people.
Soluri will give a presentation and do a book signing on April 11, 2015 at the Smithsonian’s Hirshhorn Museum & Sculpture Garden. Soluri will be joined by four individuals who played key roles in Service Mission SM4: astronaut Scott Altman, the STS-125 shuttle commander; David Leckrone, senior project scientist; Christy Hansen, EVA spacewalk flight controller and astronaut instructor; and Hubble systems engineer Ed Rezac. More information on that event can be found here.
Cosmologists are intellectual time travelers. Looking back over billions of years, these scientists are able to trace the evolution of our Universe in astonishing detail. 13.8 billion years ago, the Big Bang occurred. Fractions of a second later, the fledgling Universe expanded exponentially during an incredibly brief period of time called inflation. Over the ensuing eons, our cosmos has grown to such an enormous size that we can no longer see the other side of it.
But how can this be? If light’s velocity marks a cosmic speed limit, how can there possibly be regions of spacetime whose photons are forever out of our reach? And even if there are, how do we know that they exist at all?
The Expanding Universe
Like everything else in physics, our Universe strives to exist in the lowest possible energy state possible. But around 10-36 seconds after the Big Bang, inflationary cosmologists believe that the cosmos found itself resting instead at a “false vacuum energy” – a low-point that wasn’t really a low-point. Seeking the true nadir of vacuum energy, over a minute fraction of a moment, the Universe is thought to have ballooned by a factor of 1050.
Since that time, our Universe has continued to expand, but at a much slower pace. We see evidence of this expansion in the light from distant objects. As photons emitted by a star or galaxy propagate across the Universe, the stretching of space causes them to lose energy. Once the photons reach us, their wavelengths have been redshifted in accordance with the distance they have traveled.
Two sources of redshift: Doppler and cosmological expansion; modeled after Koupelis & Kuhn. Bottom: Detectors catch the light that is emitted by a central star. This light is stretched, or redshifted, as space expands in between. Credit: Brews Ohare.
This is why cosmologists speak of redshift as a function of distance in both space and time. The light from these distant objects has been traveling for so long that, when we finally see it, we are seeing the objects as they were billions of years ago.
The Hubble Volume
Redshifted light allows us to see objects like galaxies as they existed in the distant past; but we cannot see all events that occurred in our Universe during its history. Because our cosmos is expanding, the light from some objects is simply too far away for us ever to see.
The physics of that boundary rely, in part, on a chunk of surrounding spacetime called the Hubble volume. Here on Earth, we define the Hubble volume by measuring something called the Hubble parameter (H0), a value that relates the apparent recession speed of distant objects to their redshift. It was first calculated in 1929, when Edwin Hubble discovered that faraway galaxies appeared to be moving away from us at a rate that was proportional to the redshift of their light.
Fit of redshift velocities to Hubble’s law. Credit: Brews Ohare
Dividing the speed of light by H0, we get the Hubble volume. This spherical bubble encloses a region where all objects move away from a central observer at speeds less than the speed of light. Correspondingly, all objects outside of the Hubble volume move away from the center faster than the speed of light.
Yes, “faster than the speed of light.” How is this possible?
The Magic of Relativity
The answer has to do with the difference between special relativity and general relativity. Special relativity requires what is called an “inertial reference frame” – more simply, a backdrop. According to this theory, the speed of light is the same when compared in all inertial reference frames. Whether an observer is sitting still on a park bench on planet Earth or zooming past Neptune in a futuristic high-velocity rocketship, the speed of light is always the same. A photon always travels away from the observer at 300,000,000 meters per second, and he or she will never catch up.
General relativity, however, describes the fabric of spacetime itself. In this theory, there is no inertial reference frame. Spacetime is not expanding with respect to anything outside of itself, so the the speed of light as a limit on its velocity doesn’t apply. Yes, galaxies outside of our Hubble sphere are receding from us faster than the speed of light. But the galaxies themselves aren’t breaking any cosmic speed limits. To an observer within one of those galaxies, nothing violates special relativity at all. It is the space in between us and those galaxies that is rapidly proliferating and stretching exponentially.
The Observable Universe
Now for the next bombshell: The Hubble volume is not the same thing as the observable Universe.
To understand this, consider that as the Universe gets older, distant light has more time to reach our detectors here on Earth. We can see objects that have accelerated beyond our current Hubble volume because the light we see today was emitted when they were within it.
Strictly speaking, our observable Universe coincides with something called the particle horizon. The particle horizon marks the distance to the farthest light that we can possibly see at this moment in time – photons that have had enough time to either remain within, or catch up to, our gently expanding Hubble sphere.
And just what is this distance? A little more than 46 billion light years in every direction – giving our observable Universe a diameter of approximately 93 billion light years, or more than 500 billion trillion miles.
The observable universe, more technically known as the particle horizon.
(A quick note: the particle horizon is not the same thing as the cosmological event horizon. The particle horizon encompasses all the events in the past that we can currently see. The cosmological event horizon, on the other hand, defines a distance within which a future observer will be able to see the then-ancient light our little corner of spacetime is emitting today.
In other words, the particle horizon deals with the distance to past objects whose ancient light that we can see today; the cosmological event horizon deals with the distance that our present-day light that will be able to travel as faraway regions of the Universe accelerate away from us.)
Dark Energy
Thanks to the expansion of the Universe, there are regions of the cosmos that we will never see, even if we could wait an infinite amount of time for their light to reach us. But what about those areas just beyond the reaches of our present-day Hubble volume? If that sphere is also expanding, will we ever be able to see those boundary objects?
This depends on which region is expanding faster – the Hubble volume or the parts of the Universe just outside of it. And the answer to that question depends on two things: 1) whether H0 is increasing or decreasing, and 2) whether the Universe is accelerating or decelerating. These two rates are intimately related, but they are not the same.
In fact, cosmologists believe that we are actually living at a time when H0 is decreasing; but because of dark energy, the velocity of the Universe’s expansion is increasing.
That may sound counterintuitive, but as long as H0 decreases at a slower rate than that at which the Universe’s expansion velocity is increasing, the overall movement of galaxies away from us still occurs at an accelerated pace. And at this moment in time, cosmologists believe that the Universe’s expansion will outpace the more modest growth of the Hubble volume.
So even though our Hubble volume is expanding, the influence of dark energy appears to provide a hard limit to the ever-increasing observable Universe.
Our Earthly Limitations
Cosmologists seem to have a good handle on deep questions like what our observable Universe will someday look like and how the expansion of the cosmos will change. But ultimately, scientists can only theorize the answers to questions about the future based on their present-day understanding of the Universe. Cosmological timescales are so unimaginably long that it is impossible to say much of anything concrete about how the Universe will behave in the future. Today’s models fit the current data remarkably well, but the truth is that none of us will live long enough to see whether the predictions truly match all of the outcomes.
Disappointing? Sure. But totally worth the effort to help our puny brains consider such mind-bloggling science – a reality that, as usual, is just plain stranger than fiction.
A proposed LEGO version of the Hubble Space Telescope won't be produced, Credit: LEGO.
This week the official LEGO review board announced their newest official LEGO model kits that were chosen from fan-suggested ideas, submitted through its LEGO Ideas website. While a Hubble Space Telescope kit seemed an obvious choice (this year is Hubble’s 25th anniversary), instead the review board chose a Pixar WALL-E robot set and a Doctor Who set.
“We reviewed eight amazing projects that reached 10,000 supporters between June and September,” said Signe Lonholdt from the LEGO Ideas team said in a video (below) announcing the winners. The eight sets had each reached 10,000 fan votes, which Lonholdt said is a “tremendous accomplishment,” but the final decision is up to the review board. The board considers factors such as “playability, safety and fit within the LEGO brand.”
The LEGO Hubble Space Telescope set was designed and submitted by fan Gabriel Russo, who said the kit would be “the perfect homage to its 25th anniversary in 2015.” According to Robert Pearlman at collectSpace.com, it reached 10,000 votes last August. You can see the Hubble submission page here.
Other fan-submitted ideas that didn’t make the cut were three different Star Wars sets (an AT-AT, a Lightsaber set and an Invisible Hand set) along with a Ghostbusters HQ building.
Previous space-related fan-created/submitted kits that were chosen and produced by LEGO are models of Japan’s Hayabusa spacecraft and NASA’s Mars Curiosity rover.
You can see other submitted ideas and vote for them on the LEGO Ideas site.
Play the skywatching game long enough, and anything can happen.
Well, nearly anything. One of the more unique clockwork events in our solar system occurs this weekend, when shadows cast by three of Jupiter’s moons can be seen transiting its lofty cloud tops… simultaneously.
How rare is such an event? Well, Jean Meeus calculates 31 triple events involving moons or their shadows occurring over the 60 year span from 1981 to 2040.
But not all are as favorably placed as this weekend’s event. First, Jupiter heads towards opposition just next month. And of the aforementioned 31 events, only 9 are triple shadow transits. Miss this weekend’s event, and you’ll have to wait until March 20th, 2032 for the next triple shadow transit to occur.
Hubble spies a triple shadow transit on March 28th, 2004 . Credit: NASA/JPL/Arizona.
Of course, double shadow transits are much more common throughout the year, and we included some of the best for North America and Europe in 2015 in our 2015 roundup.
The key times when all three shadows can be seen crossing Jupiter’s 45” wide disk are on the morning of Saturday, January 24th starting at 6:26 Universal Time (UT) as Europa’s shadow ingresses into view, until 6:54 UT when Io’s shadow egresses out of sight. This converts to 1:26 AM EST to 1:54 AM EST. The span of ‘triplicate shadows’ only covers a period of slightly less than 30 minutes, but the action always unfolds fast in the Jovian system with the planet’s 10 hour rotation period.
The view on January 24th at 6:41 UT/1:41 AM EST. Credit: Created using Starry Night Education software.
Unfortunately, the Great Red Spot is predicted to be just out of view when the triple transit occurs, as it crosses Jupiter’s central meridian over three hours later at 10:28 UT.
The moons involved in this weekend’s event are Io, Callisto and Europa. Now, I know what you’re thinking. Seeing three shadows at once is pretty neat, but can you ever see four?
The short answer is no, and the reason has to do with orbital resonance.
The orbital resonance of the three innermost Galilean moons. (Credit: Wikimedia Commons).
The three innermost Galilean moons of Jupiter (Io, Europa and Ganymede) are locked in a 4:2:1 resonance. Unfortunately, this resonance assures that you’ll always see two of the innermost three crossing the disk of Jupiter, but never all three at once. Either Europa or Ganymede is nearly always the “odd moon out.”
To complete a ‘triple play,’ outermost Callisto must enter the picture. Trouble is, Callisto is the only Galilean moon that can ‘miss’ Jupiter’s disk from our line of sight. We’re lucky to be in an ongoing season of Callisto transits in 2015, a period that ends in July 2016.
Perhaps, on some far off day, a space tourism agency will offer tours to that imaginary vantage point on the surface of one of Jupiter’s moons such as Callisto to watch a triple transit occur from close up. Sign me up!
Jupiter currently rises in late January around 5:30 PM local, and sets after sunrise. It is also well placed for northern hemisphere observers in Leo at a declination 16 degrees north . This weekend’s event favors Europe towards local sunrise and ‘Jupiter-set,’ and finds the gas giant world well-placed high in the sky for all of North America in the early morning hours of the 24th.
Jupiter rides high to the south at 1:45 AM EST for the US East Coast. Credit: Stellarium.
Look closely. Do the shadows of the individual moons appear different to you at the eyepiece? It’s interesting to note during a multiple transit that not all Jovian moon shadows are ‘created equal’. Distant Callisto casts a shadow that’s broad, with a ragged gray and diffuse rim, while the shadow of innermost Io appears as an inky black punch-hole dot. If you didn’t know better, you’d think those alien monoliths were busy consuming Jupiter in a scene straight out of the movie 2010. Try sketching multiple shadow transits and you’ll soon find that you can actually identify which moon is casting a shadow just from its appearance alone.
The orientation of Earth’s nighttime shadow at mid-triple transit. Credit: Created using Orbitron.
Other mysteries of the Galilean moons persist as well. Why did late 19th century observers describe them as egg-shaped? Can visual observers tease out such elusive phenomena as eruptions on Io by measuring its anomalous brightening? I still think it’s amazing that webcam imagers can now actually pry out surface detail from the Galilean moons!
The 2004 triple shadow transit. Photo by author.
Observing and imaging a shadow transit is easy using a homemade planetary webcam. We’d love to see someone produce a high quality animation of the upcoming triple shadow transit. I know that such high tech processing abilities — to include field de-rotation and convolution mapping of the Jovian sphere — are indeed out there… its breathtaking to imagine just how quickly the fledgling field of ad hoc planetary webcam imaging has changed in just 10 years.
The moons and Jupiter itself also cast shadows off to one side of the planet or the other depending on our current vantage point. We call the point when Jupiter sits 90 degrees east or west of the Sun quadrature, and the point when it rises and sets opposite to the Sun is known as opposition. Opposition for Jupiter is coming right up for 2015 on February 6th. During opposition, Jupiter and its moons cast their respective shadows nearly straight back.
Did you know: the speed of light was first deduced by Danish astronomer Ole Rømer in 1671 using the discrepancy he noted while predicting phenomena of the Galilean moons at quadrature versus opposition. There were also early ideas to use the positions of the Galilean moons to tell time at sea, but it turned out to be hard enough to see the moons and their shadows with a small telescope based on land, let alone from the pitching deck of a ship in the middle of the ocean.
And speaking of mutual events, we’re still in the midst of a season where it’s possible to see the moons of Jupiter eclipse and occult one another. Check out the USNO’s table for a complete list of events, coming to a sky near you.
And let’s not forget that NASA’s Juno spacecraft is headed towards Jupiter as well., Juno is set to enter a wide swooping orbit around the largest planet in the solar system in July 2016.
Now is a great time to get out and explore Jove… don’t miss this weekend’s triple shadow transit!
Read Dave Dickinson’s sci-fi tale of astronomical eclipse tourism through time and space titled Exeligmos.
The Hubble Space Telescope's extreme close-up of M31, the Andromeda Galaxy. Picture released in January 2015. Credit: NASA, ESA, J. Dalcanton, B.F. Williams, and L.C. Johnson (University of Washington), the PHAT team, and R. Gendler
Woah, is that ever close! The Hubble Space Telescope’s new picture of the Andromeda Galaxy makes us feel as though we’re hovering right above the iconic structure, which is visible with the naked eye from Earth under the right conditions.
Just to show you how awesome this close-up is, we’ve posted a picture below the jump showing what is the typical view of M31 in a more modest telescope.
“This ambitious photographic cartography of the Andromeda galaxy represents a new benchmark for precision studies of large spiral galaxies that dominate the universe’s population of over 100 billion galaxies,” stated the Space Telescope Science Institute (STScI), which operates the telescope.
“Never before have astronomers been able to see individual stars inside an external spiral galaxy over such a large contiguous area. Most of the stars in the universe live inside such majestic star cities, and this is the first data that reveal populations of stars in context to their home galaxy.”
M31 (image credit: Noel Carboni).
Andromeda is about 2.5 million light-years from us and on a collision course with our galaxy. The image at the top of this story is actually not a single picture; it was assembled from an astounding 7,398 exposures taken over 411 individual pointings, according to STScI.
The image is so big, in fact, that there’s a zoomable version that was released separately so that you can get a better sense of how high-definition this view is. Dontcha wish you could take a light-travel ship and see this thing up close, for real?
