In the 1920s, Edwin Hubble made the groundbreaking discovery that the Universe was in a state of expansion. Originally predicted as a consequence of Einstein’s Theory of General Relativity, measurements of this expansion came to be known as Hubble’s Constant. Today, and with the help of next-generation telescopes – like the aptly-named Hubble Space Telescope (HST) – astronomers have remeasured and revised this law many times.
These measurements confirmed that the rate of expansion has increased over time, though scientists are still unsure why. The latest measurements were conducted by an international team using Hubble, who then compared their results with data obtained by the European Space Agency’s (ESA) Gaia observatory. This has led to the most precise measurements of the Hubble Constant to date, though questions about cosmic acceleration remain.
The study which describes their findings appeared in the July 12th issue of the Astrophysical Journal, titled “Milky Way Cepheid Standards for Measuring Cosmic Distances and Application to Gaia DR2: Implications for the Hubble Constant.” The team behind the study included members from the Space Telescope Science Institute (STScI), the Johns Hopkins University, the National Institute for Astrophysics (INAF), UC Berkeley, Texas A&M University, and the European Southern Observatory (ESO).
Since 2005, Adam Riess – a Nobel Laureate Professor with the Space Telescope Science Institute and the Johns Hopkins University – has been working to refine the Hubble Constant value by streamlining and strengthening the “cosmic distance ladder”. Along with his team, known as Supernova H0 for the Equation of State (SH0ES), they have successfully reduced the uncertainty associated with the rate of cosmic expansion to just 2.2%
To break it down, astronomers have traditionally used the “cosmic distance ladder” to measure distances in the Universe. This consists of relying on distance markers like Cepheid variables in distant galaxies – pulsating stars whose distances can be inferred by comparing their intrinsic brightness with their apparent brightness. These measurements are then compared to the way light from distant galaxies is redshifted to determine how fast the space between galaxies is expanding.
From this, the Hubble Constant is derived. Another method that is used is to observe the Cosmic Microwave Background (CMB) to trace the expansion of the cosmos during the early Universe – circa. 378,000 years after the Big Bang – and then using physics to extrapolate that to the present expansion rate. Together, the measurements should provide an end-to-end measurement of how the Universe has expanded over time.
However, astronomers have known for some time that the two measurements don’t match up. In a previous study, Riess and his team conducted measurements using Hubble to obtain a Hubble Constant value of 73 km/s (45.36 mps) per megaparsec (3.3 million light-years). Meanwhile, results based on the ESA’ Planck observatory (which observed the CMB between 2009 and 2013) predicted that the Hubble constant value should now be 67 km/s (41.63 mps) per megaparsec and no higher than 69 km/s (42.87 mps) – which represents a discrepancy of 9%.
As Riess indicated in a recent NASA press release:
“The tension seems to have grown into a full-blown incompatibility between our views of the early and late time universe. At this point, clearly it’s not simply some gross error in any one measurement. It’s as though you predicted how tall a child would become from a growth chart and then found the adult he or she became greatly exceeded the prediction. We are very perplexed.”
In this case, Riess and his colleagues used Hubble to gauge the brightness of distant Cepheid variables while Gaia provided the parallax information – the apparent change in an objects position based on different points of view – needed to determine the distance. Gaia also added to the study by measuring the distance to 50 Cepheid variables in the Milky Way, which were combined with brightness measurements from Hubble.
This allowed the astronomers to more accurately calibrate the Cepheids and then use those seen outside the Milky Way as milepost markers. Using both the Hubble measurements and newly released data from Gaia, Riess and his colleagues were able to refine their measurements on the present rate of expansion to 73.5 kilometers (45.6 miles) per second per megaparsec.
As Stefano Casertano, of the Space Telescope Science Institute and a member of the SHOES team, added:
“Hubble is really amazing as a general-purpose observatory, but Gaia is the new gold standard for calibrating distance. It is purpose-built for measuring parallax—this is what it was designed to do. Gaia brings a new ability to recalibrate all past distance measures, and it seems to confirm our previous work. We get the same answer for the Hubble constant if we replace all previous calibrations of the distance ladder with just the Gaia parallaxes. It’s a crosscheck between two very powerful and precise observatories.”
Looking to the future, Riess and his team hope to continue to work with Gaia so they can reduce the uncertainty associated with the value of the Hubble Constant to just 1% by the early 2020s. In the meantime, the discrepancy between modern rates of expansion and those based on the CMB will continue to be a puzzle to astronomers.
In the end, this may be an indication that other physics are at work in our Universe, that dark matter interacts with normal matter in a way that is different than what scientists suspect, or that dark energy could be even more exotic than previously thought. Whatever the cause, it is clear the Universe still has some surprises in store for us!
Further Reading: NASA
Back in the late 1980’s, Voyager 2 was the first spacecraft to capture images of the giant storms in Neptune’s atmosphere. Before then, little was known about the deep winds cycling through Neptune’s atmosphere. But Hubble has been turning its sharp eye towards Neptune over the years to study these storms, and over the past couple of years, it’s watched one enormous storm petering out of existence.
“It looks like we’re capturing the demise of this dark vortex, and it’s different from what well-known studies led us to expect.” – Michael H. Wong, University of California at Berkeley.
When we think of storms on the other planets in our Solar System, we automatically think of Jupiter. Jupiter’s Great Red Spot is a fixture in our Solar System, and has lasted 200 years or more. But the storms on Neptune are different: they’re transient.
The storm on Neptune moves in an anti-cyclonic direction, and if it were on Earth, it would span from Boston to Portugal. Neptune has a much deeper atmosphere than Earth—in fact it’s all atmosphere—and this storm brings up material from deep inside. This gives scientists a chance to study the depths of Neptune’s atmosphere without sending a spacecraft there.
The first question facing scientists is ‘What is the storm made of?’ The best candidate is a chemical called hydrogen sulfide (H2S). H2S is a toxic chemical that stinks like rotten eggs. But particles of H2S are not actually dark, they’re reflective. Joshua Tollefson from the University of California at Berkeley, explains: “The particles themselves are still highly reflective; they are just slightly darker than the particles in the surrounding atmosphere.”
“We have no evidence of how these vortices are formed or how fast they rotate.” – Agustín Sánchez-Lavega, University of the Basque Country in Spain.
But beyond guessing what chemical the spot might me made of, scientists don’t know much else. “We have no evidence of how these vortices are formed or how fast they rotate,” said Agustín Sánchez-Lavega from the University of the Basque Country in Spain. “It is most likely that they arise from an instability in the sheared eastward and westward winds.”
There’ve been predictions about how storms on Neptune should behave, based on work done in the past. The expectation was that storms like this would drift toward the equator, then break up in a burst of activity. But this dark storm is on its own path, and is defying expectations.
“We thought that once the vortex got too close to the equator, it would break up and perhaps create a spectacular outburst of cloud activity.” – Michael H. Wong, University of California at Berkeley.
“It looks like we’re capturing the demise of this dark vortex, and it’s different from what well-known studies led us to expect,” said Michael H. Wong of the University of California at Berkeley, referring to work by Ray LeBeau (now at St. Louis University) and Tim Dowling’s team at the University of Louisville. “Their dynamical simulations said that anticyclones under Neptune’s wind shear would probably drift toward the equator. We thought that once the vortex got too close to the equator, it would break up and perhaps create a spectacular outburst of cloud activity.”
Rather than going out in some kind of notable burst of activity, this storm is just fading away. And it’s also not drifting toward the equator as expected, but is making its way toward the south pole. Again, the inevitable comparison is with Jupiter’s Great Red Spot (GRS).
The GRS is held in place by the prominent storm bands in Jupiter’s atmosphere. And those bands move in alternating directions, constraining the movement of the GRS. Neptune doesn’t have those bands, so it’s thought that storms on Neptune would tend to drift to the equator, rather than toward the south pole.
This isn’t the first time that Hubble has been keeping an eye on Neptune’s storms. The Space Telescope has also looked at storms on Neptune in 1994 and 1996. The video below tells the story of Hubble’s storm watching mission.
The images of Neptune’s storms are from the Hubble Outer Planets Atmosphere Legacy (OPAL) program. OPAL gathers long-term baseline images of the outer planets to help us understand the evolution and atmospheres of the gas giants. Images of Jupiter, Saturn, Uranus and Neptune are being taken with a variety of filters to form a kind of time-lapse database of atmospheric activity on the four gas planets.
KENNEDY SPACE CENTER, FL – Today marked the end of an era for NASA as the last of the agency’s next generation Tracking and Data Relay Satellites (TRDS) that transmit the critical science data and communications for the Hubble Space Telescope and human spaceflight missions to the International Space Station, successfully rocketed to orbit this morning, Fri. Aug 18 from the Florida Space Coast.
The spectacular liftoff of the strangely fish-like TDRS-M science relay comsat atop a United Launch Alliance Atlas V rocket occurred at 8:29 a.m. EDT a.m. (2:29 GMT) Aug. 18 from Space Launch Complex 41 at Cape Canaveral Air Force Station.
The weather cooperated with relatively thin but artistic clouds and low winds and offered spectators a spectacular launch show that will not forget.
NASA’s $408 million next generation Tracking and Data Relay Satellites (TRDS) looks like a giant alien fish or cocooned creature. But actually plays an unparalleled role in relaying critical science measurements, research data and tracking observations gathered by the International Space Station (ISS), Hubble and a plethora of Earth science missions.
“TDRS is a critical national asset have because of its importance to the space station and all of our science missions, primarily the Hubble Space Telescope and Earth science missions that use TDRS,” said Tim Dunn, NASA’s TDRS-M launch director.
TDRS-M will provide high-bandwidth communications to spacecraft in low-Earth orbit. The TDRS network enables continuous communication with the International Space Station, the Hubble Space Telescope, the Earth Observing System and other programs supporting human space flight, said satellite builder Boeing, the prime contractor for the mission.
TDRS-M is the last of three satellites to be launched in the third generation of TDRS satellites. It is also the final satellite built based on Boeing’s 601 spacecraft bus series.
NASA plans to switch to much higher capacity laser communications for the next generation of TDRS-like satellites and therefore opted to not build a fourth third generation satellite after TDRS-M.
“The TDRS fleet is a critical connection delivering science and human spaceflight data to those who can use it here on Earth,” said Dave Littmann, the TDRS project manager at NASA’s Goddard Space Flight Center in Greenbelt, Maryland.
“TDRS-M will expand the capabilities and extend the lifespan of the Space Network, allowing us to continue receiving and transmitting mission data well into the next decade.”
TDRS-M joins a constellation of 9 TDRS satellites already in orbit and ups the fleet to ten orbiting satellites.
The Atlas V rocket and Centaur upper stage delivered TDRS-M to its desired preliminary orbit.
“Trajectory analysis in. Injection accuracy was within 1% of prediction #TDRSM,” tweeted ULA CEO Torey Bruno.
Several hours after the launch ground controllers reported the satellite was in good health.
On tap now is a four month period or orbit checkout by prime contractor Boeing as well as a series of five significant orbit raising maneuvers from its initial orbit to Geostationary orbit over the Pacific Ocean.
“This TDRS-M milestone is another step forward in Boeing’s commitment to developing technologies to support future NASA near-Earth, moon, Mars and deep space missions – and to do so affordably, drawing on our 40-plus years of strong Boeing-NASA partnership,” said Enrico Attanasio, executive director, Department of Defense and Civil Programs, Boeing Satellite Systems.
Ground controllers will then move it to its final orbit over the Atlantic Ocean.
NASA plans to conduct additional tests before putting TDRS-M into service early next year over the Atlantic.
The importance of the TDRS constellation of satellites can’t be overstated.
Virtually all the communications relay capability involving human spaceflight, such as the ISS, resupply vehicles like the SpaceX cargo Dragon and Orbital ATK Cygnus and the soon to launch human space taxis like crew Dragon, Boeing Starliner and NASA’s Orion deep space crew capsule route their science results voice, data, command, telemetry and communications via the TDRS network of satellites.
The TDRS constellation enables both space to space and space to ground communications for virtually the entire orbital period.
The two stage Atlas V rocket stands 191 feet tall.
TDRS-M, spacecraft, which stands for Tracking and Data Relay Satellite – M is NASA’s new and advanced science data relay communications satellite that will transmit research measurements and analysis gathered by the astronaut crews and instruments flying abroad the International Space Station (ISS), Hubble Space Telescope and over 35 NASA Earth science missions including MMS, GPM, Aura, Aqua, Landsat, Jason 2 and 3 and more.
The TDRS constellation orbits 22,300 miles above Earth and provide near-constant communication links between the ground and the orbiting satellites.
TRDS-M will have S-, Ku- and Ka-band capabilities. Ka has the capability to transmit as much as six-gigabytes of data per minute. That’s the equivalent of downloading almost 14,000 songs per minute says NASA.
The TDRS program is managed by NASA’s Goddard Space Flight Center in Greenbelt, Maryland.
TDRS-M is the third satellite in the third series of NASA’s American’s most powerful and most advanced Tracking and Data Relay Satellites. It is designed to last for a 15 year orbital lifetime.
The first TDRS satellite was deployed from the Space Shuttle Challenger in 1983 as TDRS-A.
TDRS-M was built by prime contractor Boeing in El Segundo, California and is the third of a three satellite series – comprising TDRS -K, L, and M. They are based on the Boeing 601 series satellite bus and will be keep the TDRS satellite system operational through the 2020s.
TDSR-K and TDRS-L were launched in 2013 and 2014.
The Tracking and Data Relay Satellite project is managed at NASA’s Goddard Space Flight Center.
TDRS-M was built as a follow on and replacement satellite necessary to maintain and expand NASA’s Space Network, according to a NASA description.
The gigantic satellite is about as long as two school buses and measures 21 meters in length by 13.1 meters wide.
It has a dry mass of 1800 kg (4000 lbs) and a fueled mass of 3,454 kilogram (7,615 lb) at launch.
Watch for Ken’s continuing onsite TDRS-M, CRS-12, ORS 5 and NASA and space mission reports direct from the Kennedy Space Center and Cape Canaveral Air Force Station, Florida.
Stay tuned here for Ken’s continuing Earth and Planetary science and human spaceflight news.
NASA has announced the discovery of hydrogen in the plumes on Enceladus. This is huge news, and Cassini scientists have looked forward to this day. What it means is that there is a potential source of energy for microbes in the oceans of Enceladus, and that energy from the Sun is not required to support life.
We’ve known about the plumes on Enceladus for a while now, and Cassini has even flown through those plumes to determine their content. But hydrogen was never discovered until now. What it means is that there is a geochemical source for hydrogen in Enceladus’ ocean, coming from the interaction between warm water and rocks.
“This is the closest we’ve come, so far, to identifying a place with some of the ingredients needed for a habitable environment.” – Thomas Zurbuchen, NASA.
This is a capstone finding, according to NASA. As far as we know, life needs three things to exist: water, energy, and the right chemicals. We know it has the necessary chemicals, we know it has water, and we now know it has a source of energy.
On Earth, hydrothermal vents deep in the ocean floor provide the energy for a web of life reliant on those vents. Bacteria live there, forming the base of a food chain that can include tube worms, shrimp, and other life forms. This discovery points to the possibility that similar communities might exist in the sub-surface ocean of Enceladus.
“This is the closest we’ve come, so far, to identifying a place with some of the ingredients needed for a habitable environment,” said Thomas Zurbuchen, associate administrator for NASA’s Science Mission Directorate at Headquarters in Washington.
Microbes in Enceladus’ ocean could use the hydrogen in a process called methanogenesis. They obtain energy by combining hydrogen with dissolved carbon dioxide in the water. This process produces a methane by-product. Methanogenesis is a bedrock process at the root of life here on Earth.
“Confirmation that the chemical energy for life exists within the ocean of a small moon of Saturn is an important milestone in our search for habitable worlds beyond Earth,” said Linda Spilker, Cassini project scientist at NASA’s Jet Propulsion Laboratory (JPL) in Pasadena, California.
Hubble Confirms Plumes On Europa
NASA has also announced that the Hubble Space Telescope has confirmed the presence of plumes on another of our Solar System’s icy moons, Europa.
These plumes were first seen by the Hubble in 2014, but were never seen again. Since repeatability is key in science, those findings were put on the back burner. But in 2016, NASA announced today, Hubble spotted them again, in the same place. This is the same spot that the Galileo probe noticed a thermal hot spot.
We don’t know if Europa has hydrogen in its oceans, but it’s easy to see where this is going. NASA’s excitement is palpable.
NASA’s Europa Clipper mission will visit Europa and determine the thickness of its ice layer, as well as the depth and salinity of its ocean. It will also analyze the atmosphere and the composition of the plumes. Europa Clipper will fill in a lot of gaps in our understanding.
Europa Clipper will be launched around 2022, but a mission to Enceladus will have to wait a little longer. One mission under consideration in NASA’s Discovery program is ELF, Enceladus Life Finder. ELF would fly through Enceladus’ plumes 8 or 10 times, taking more detailed samples of their content.
The discovery of hydrogen in the plumes of Enceladus is huge news any way you look at it. But that discovery begs the question: Are we doing it all wrong? Are we looking for life in the wrong places?
The search for life elsewhere in the Universe, so far, has mostly revolved around exoplanets. And then refining that search to identify exoplanets that are in the habitable zones of their stars. We’re searching for other Earths, basically.
But maybe we should be changing our focus. Maybe it’s the ice worlds, including icy exomoons, that are the most likely targets for our search. This new evidence from NASA’s Cassini mission, and from the Hubble Space Telescope, suggests that in our Solar System at least, they are the best place to search.
One Final Ingredient Needed?
There’s a fourth ingredient needed for life. Once there is water, energy, and the necessary chemicals, life needs time to get going. How much time, we’re not exactly certain. But this is where Enceladus and Europa are different.
Europa is about 4 billion years old, or so we think. That’s only half a billion years younger than Earth, and we think life started on Earth about 3.5 billion years ago. This hints that, if conditions on Europa are favorable, life has had a long time to get going. Of course, that doesn’t mean it has.
On the other hand, Enceladus is probably much younger. A study of the orbits of Saturn’s moons suggests that Enceladus may only be 100 million years old. If that’s true, it’s not very much time for life to get going.
The hydrogen discovery is huge news. There are still a lot of questions, of course, and lots to be debated. But confirming a source of energy on Enceladus builds the case for the same type of hydrothermal vent life that we see on Earth.
Now all we need is a mission to Enceladus.
Earth doesn’t have a corner on auroras. Venus, Mars, Jupiter, Saturn, Uranus and Neptune have their own distinctive versions. Jupiter’s are massive and powerful; Martian auroras patchy and weak.
Auroras are caused by streams of charged particles like electrons that originate with solar winds and in the case of Jupiter, volcanic gases spewed by the moon Io. Whether solar particles or volcanic sulfur, the material gets caught in powerful magnetic fields surrounding a planet and channeled into the upper atmosphere. There, the particles interact with atmospheric gases such as oxygen or nitrogen and spectacular bursts of light result. With Jupiter, Saturn and Uranus excited hydrogen is responsible for the show.
Auroras on Earth, Jupiter and Saturn have been well-studied but not so on the ice-giant planet Uranus. In 2011, the Hubble Space Telescope took the first-ever image of the auroras on Uranus. Then in 2012 and 2014 a team from the Paris Observatory took a second look at the auroras in ultraviolet light using the Space Telescope Imaging Spectrograph (STIS) installed on Hubble.
Two powerful bursts of solar wind traveling from the sun to Uranus stoked the most intense auroras ever observed on the planet in those years. By watching the auroras over time, the team discovered that these powerful shimmering regions rotate with the planet. They also re-discovered Uranus’ long-lost magnetic poles, which were lost shortly after their discovery by Voyager 2 in 1986 due to uncertainties in measurements and the fact that the planet’s surface is practically featureless. Imagine trying to find the north and south poles of a cue ball. Yeah, something like that.
In both photos, the auroras look like glowing dots or patchy spots. Because Uranus’ magnetic field is inclined 59° to its spin axis (remember, this is the planet that rotates on its side!) , the auroral spots appear far from the planet’s north and south geographic poles. They almost look random but of course they’re not. In 2011, the spots lie close to the planet’s north magnetic pole, and in 2012 and 2014, near the south magnetic pole — just like auroras on Earth.
An auroral display can last for hours here on the home planet, but in the case of the 2011 Uranian lights, they pulsed for just minutes before fading away.
Want to know more? Read the team’s findings in detail here.
It sometimes doesn’t take much to tear a family apart. A Christmas dinner gone wrong can do that. But for a family of stars to be torn apart, something really huge has to happen.
The dramatic break-up of a family of stars played itself out in the Orion Nebula, about 600 years ago. The Orion Nebula is one of the most studied objects in our galaxy. It’s an active star forming region, where much of the star birth is concealed behind clouds of dust. Advances in infrared and radio astronomy have allowed us to peer into the Nebula, and to watch a stellar drama unfolding.
Over the last few decades, observations showed the two of the stars in our young family travelling off in different directions. In fact, they were travelling in opposite directions, and moving at very high speeds. Much higher than stars normally travel at. What caused it?
Astronomers were able to piece the story together by re-tracing the positions of both stars back 540 years. All those centuries ago, around the same time that it was dawning on humanity that Earth revolved around the Sun instead of the other way around, both of the speeding stars were in the same location. This suggested that the two were part of a star system that had broken up for some reason. But their combined energy didn’t add up.
Now, the Hubble has provided another clue to the whole story, by spotting a third runaway star. They traced the third star’s path back 540 years and found that it originated in the same location as the others. That location? An area near the center of the Orion Nebula called the Kleinmann-Low Nebula.
The team behind these new results, led by Kevin Luhman of Penn State University, will release their findings in the March 20, 2017 issue of The Astrophysical Journal Letters.
“The new Hubble observations provide very strong evidence that the three stars were ejected from a multiple-star system,” said Luhman. “Astronomers had previously found a few other examples of fast-moving stars that trace back to multiple-star systems, and therefore were likely ejected. But these three stars are the youngest examples of such ejected stars. They’re probably only a few hundred thousand years old. In fact, based on infrared images, the stars are still young enough to have disks of material leftover from their formation.”
“The Orion Nebula could be surrounded by additional fledging stars that were ejected from it in the past and are now streaming away into space.” – Lead Researcher Kevin Luhman, Penn State University.
The three stars are travelling about 30 times faster than most of the Nebula’s other stellar inhabitants. Theory has predicted the phenomenon of these breakups in regions where newborn stars are crowded together. These gravitational back-and-forths are inevitable. “But we haven’t observed many examples, especially in very young clusters,” Luhman said. “The Orion Nebula could be surrounded by additional fledging stars that were ejected from it in the past and are now streaming away into space.”
The key to this mystery is the recently discovered third star. But this star, the so-called “source x”, was discovered by accident. Luhman is part of a team using the Hubble to hunt for free-floating planets in the Orion Nebula. A comparison of Hubble infrared images from 2015 with images from 1998 showed that source x had changed its position. This indicated that the star was moving at a speed of about 130,000 miles per hour.
Luhmann then re-traced source x’s path and it led to the same position as the other 3 runaway stars 540 years ago: the Kleinmann-Low Nebula.
According to Luhmann, the three stars were most likely ejected from their system due to gravitational fluctuations that should be common in a high-population area of newly-born stars. Two of the stars can come very close together, either forming a tight binary system or even merging. That throws the gravitational parameters of the system out of whack, and other stars can be ejected. The ejection of those stars can also cause fingers of matter to flow out of the system.
As we get more powerful telescopes operating in the infrared, we should be able to clarify exactly what happens in areas of intense star formation like the Orion Nebula and its embedded Kleinmann-Low Nebula. The James Webb Space Telescope should advance our understanding greatly. If that’s the case, then not only will the details of star birth and formation become much clearer, but so will the break up of young families of stars.
Welcome, come in to the 497th Carnival of Space! The Carnival is a community of space science and astronomy writers and bloggers, who submit their best work each week for your benefit. I’m Susie Murph, part of the team at Universe Today and CosmoQuest. So now, on to this week’s stories!
Continue reading “Carnival of Space #497”
The final servicing mission to the venerable Hubble Space Telescope (HST) was in 2009. The shuttle Atlantis completed that mission (STS-125,) and several components were repaired and replaced, including the installation of improved batteries. The HST is expected to function until 2030 – 2040. With the retiring of the shuttle program in 2011, it looked like the Hubble mission was destined to play itself out.
But now there’s talk of another servicing mission to the Hubble, to be performed by the Dream Chaser Space System.
The Hubble was originally deployed by the Space Shuttle Discovery in 1990. It was serviced by crew aboard the shuttles 5 times on 5 different shuttle missions. Unlike the other observatories in NASA’s Great Observatories, the Hubble was designed to be serviced during its lifetime.
Those servicing missions, which took place in 1993, 1997, 1999, 2002, and 2009, were complex missions which required coordination between the Kennedy Space Center, Johnson Space Center, and the Goddard Space Flight Center. Grasping Hubble with the robotic Canadarm and placing it inside the shuttle bay was a methodical process. So was the repair and replacement of components, and the testing of components once Hubble was removed from the cargo bay. Though complicated, these missions were ultimately successful, and the Hubble is still operating.
A future servicing mission to the Hubble would be a sort of insurance policy in case there are problems with NASA’s new flagship telescope, the James Webb Space Telescope (JWST.) The JWST is due to be launched in 2018, and its capabilities greatly exceed those of the Hubble. But the James Webb’s destination is LaGrange Point 2 (L2), a stable point in space about 1.5 million km (932,000 miles) from Earth. It will enter a halo orbit around L2, which makes a repair mission difficult. Though deployment problems with the JWST could be corrected by visiting spacecraft, the Telescope itself is not designed to be repaired like the Hubble is.
Since the JWST is risky, both in terms of its position in space and its unproven deployment method, some type of insurance policy may be needed to ensure NASA has a powerful telescope operating in space. But without Space Shuttles to visit the Hubble and extend its life, a different vehicle would have to be tasked with any potential future servicing missions. Enter the Dream Chaser Space System (DCSS).
The Dream Chaser Space System is like a smaller Space Shuttle. It can carry seven people into Low-Earth Orbit (LEO). Like the Shuttles, it then returns to Earth and lands horizontally on an airstrip. The DCSS, however, does not have a cargo bay or a robotic arm. If it were used for a Hubble repair mission, all repairs would likely have to be done during spacewalks. The DCSS is designed as a cargo and crew resupply ship for the International Space System. The much larger shuttles were designed with the Hubble in mind, as well as other tasks, like building and servicing the ISS and recovering satellites from orbit.
The DCSS is built by Sierra Nevada Corporation. It will be launched on an Atlas V rocket, and will return to Earth by gliding, where it can land on any commercial runway. The DCSS has its own reaction control system for manoeuvering in space. Like other commercial space ventures, the development of the DCSS has been partly funded by NASA.
The James Webb has a complex deployment. It will be launched on an Ariane 5 rocket, where it will be folded up in order to fit. The primary mirror on the JWST is made up of 18 segments which must unfold in three sections for the telescope to function. The telescope’s sun shield, which keeps the JWST cool, must also unfold after being deployed. Earlier in the mission, the Webb’s solar array and antennae need to be deployed.
This video shows the deployment of the JWST. It reminds one of a giant insect going through metamorphosis.
If either the mirror, the sunshield, or any of the other unfolding mechanisms fail, then a costly and problematic mission will have to be planned to correct the deployment. If some other crucial part of the telescope fails, then it probably can’t be repaired. NASA needs everything to go well.
People have been waiting for the JWST for a long time. It’s had kind of a tortured path to get this far. We all have our fingers crossed that the mission succeeds. But if there are problems, it may be up to the Hubble to keep doing what it’s always done: provide the kinds of science and stunning images that excites scientists and the rest of us about the Universe.
Host: Fraser Cain (@fcain)
Dr. Frank Timmes is an astrophysicist at Arizona State University and will be discussing online astronomy education and the Global Freshman Academy. His interests include the universe’s evolving composition and its implications for life in the universe. Dr. Timmes’ current area of research is nuclear astrophysics and the creation of the periodic table.
Morgan Rehnberg (MorganRehnberg.com / @MorganRehnberg)
Dave Dickinson (www.astroguyz.com / @astroguyz)
Kimberly Cartier ( KimberlyCartier.org / @AstroKimCartier )
Nicole Gugliucci (cosmoquest.org / @noisyastronomer)
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