Category Archives: Hubble Telescope

Peering way back in time, astronomers have discovered the faintest galaxy ever detected in the early universe.

No more than a few pixels in Hubble images, the galaxy appears as it did 13.1 billion years ago just 700 million years after the big bang.

The discovery, reported in the journal Nature Astronomy, sheds light on a critical period in the evolution of the universe.

Up to a billion years after the big bang, light from the earliest stars and galaxies ionised hydrogen atoms.

This process produced charged plasma instead of opaque, neutral hydrogen gas, bringing an end to the cosmic "dark ages" and creating the transparent universe we know today.

Study co-author Michele Trenti of the University of Melbourne said that faint galaxies, which are the most common in the universe, were thought to be responsible for this crucial "cosmic reionisation".

But up until now, astronomers had only found a handful of bright galaxies at this distance.

"The further back in time you look at distant objects, the harder it is to find the smaller, more common galaxies," Dr Trenti said.

Austin Hoag, who led the study, said the newly discovered galaxy, known as MACS1423-z7p64, was about 10 times fainter than other galaxies that have been found at the same distance.

"That might not sound like much, but when you are looking for galaxies at such a vast distance, even the very brightest ones are hard to confirm," said Mr Hoag, a PhD candidate at the University of California, Davis.

Dr Trenti said the galaxy was estimated to have about 500 million stars.

"To put that in context, our own galaxy, the Milky Way, has about 100 billion stars. Thus we are talking about a galaxy that is about 200 times less massive than the Milky Way."

He said the discovery pushed the limits of what was possible using current telescopes.

"The smallest galaxies might have just one million stars, so there is still room for future discoveries of even less luminous distant galaxies as our telescope technology improves," Dr Trenti said.

Gravitational lensing: The researchers focused the Hubble Telescope on a bigger, closer galaxy to bend light and magnify more distant galaxies

(Supplied: NASA/W. M. Keck Observatory/A. Hoag/M. Bradac)

Gravitational lensing: The researchers focused the Hubble Telescope on a bigger, closer galaxy to bend light and magnify more distant galaxies

Supplied: NASA/W. M. Keck Observatory/A. Hoag/M. Bradac

The international team of astronomers made the discovery using the Hubble Space Telescope and the Keck Observatory in Hawaii.

First, they used a technique known as gravitational lensing to locate and identify distant galaxies.

"It happens when the galaxy you are looking for is behind a very massive structure, in our case a cluster of galaxies at a much closer distance than the galaxy itself," explained Mr Hoag.

"The mass from the structure bends the light of the more distant galaxy, and in some cases causes the galaxy to be magnified."

The galaxy was sitting in a sweet spot behind a giant cluster that magnified its brightness by a factor of 10, so it could be detected by the Hubble telescope.

Then, to get a precise measurement of the distance, a team led by Mr Hoag used the Keck Observatory to analyse the light spectrum coming from the galaxy.

"Because the light has to travel all the way from the distant sources to us in an expanding universe it gets shifted towards the red wavelength," Dr Trenti explained.

The galaxy had a redshift of 7.6, meaning its light came from when the universe was only about 700 million years old.

A team led by Dr Trenti repeated the observations again a year later in 2016 to confirm the distance was correct.

Dr Trenti said it was likely more faint galaxies at this distance would be revealed by more powerful telescopes, such as the James Webb Telescope, which is due to be launched in 2018.

"It took us two nights staring at the source with the Keck telescope in different years [to confirm this galaxy]," Dr Trenti said.

"The James Webb will get much higher quality spectrum in one or two hours of observation. It will be the next really giant leap forward in the field."

The James Webb Space Telescope will be able to see further back in space than current telescopes.

(Supplied: NASA)

The James Webb Space Telescope will be able to see further back in space than current telescopes.

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Astronomers detect ultra-faint galaxy from the very early universe - ABC Online

Unlike its more glamorous relatives Mars, Jupiter and Saturn, Uranus gets a bit of a bum deal when it comes to planetary popularity; often the butt of jokes thanks to its slightly inelegant name.

SEE ALSO: Watch NASA Footage Of An Exploding Star

This is, in our opinion, is grossly unfair, so it's good to see Uranus getting a bit of love thanks to some powerful, naturally-occurring auroras that were spotted by the Hubble Telescope.

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Scientists at the Paris Observatory were able to capture a dazzling light show occurring around Uranus, a sight not dissimilar from the Northern Lights here on earth.

Caused by solar winds colliding with oxygen and nitrogen gas particles in the planet's outer atmosphere, it was discovered in 2012 that these light shows actually rotate with the planet.

Despite these new images, little is known about the seventh planet from the sun, aside from the fact that it's very cold, 63 times bigger than our fair planet and that its winds can travel at speeds reaching more than 500 miles per hour.

Another view of Uranus

NASA

We'll just wait for the inevitable Mars colony, if that's ok...

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The Hubble Telescope Spotted Something Strange Going On Around Uranus - Esquire.co.uk

NASA is set to reveal this week at a news conference new results about ocean worlds in our solar system. The announcements will be related particularly to findings from the agencys Saturn probe Cassini spacecraft and the Hubble space telescope, NASA said in a statement. These new discoveries will also help inform future ocean world exploration including NASAs upcoming Europa Clipper mission planned for launch in the 2020s and the broader search for life beyond the Earth.

The event, to be held at the James Webb Auditorium at NASA Headquarters in Washington on Thursday at 2.00PM EDT (11.30PM India time), will include remote participation from experts across the US. NASAs Cassini spacecraft, which was launched in 1997 and arrived at Saturn in 2004, is set to end its 20-year journey on September 15 this year with a planned plunge.

The agencys planned Europa Clipper would place a spacecraft in orbit around Jupiter in order to perform a detailed investigation of the giant planets moon Europa a world that shows strong evidence for an ocean of liquid water beneath its icy crust and which could host conditions favorable for life. ALSO READ:NASAs Hubble telescope shows close-up image of Jupiter, Great Red Spot

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NASA to reveal findings from Saturn probe Cassini, Hubble telescope this week - BGR India

Amid plenty of political turmoil on Earth on Thursday, NASA and the European Space Agency quietly released the latest photo of Jupiter taken by the Hubble Space Telescope.

This picture revealed no new discoveries, unlike a Hubble image last fall that detected evidence of water vapor plumes from one of Jupiter's moons. Nor did it capture the aftermath of some significant event, such as when a comet or asteroid collided with Jupiter's atmosphere and left it "bruised."

Instead, Thursday's picture was simply a reminder that, somewhere out there above the heavens, a decades-old space telescope is still doing what it has done best: capturing spectacularly detailed images of the universe to blow the minds of those on Earth.

Courtesy of NASA, the European Space Agency, A. Simon via GSFC

Jupiter, as captured by the Hubble Space Telescope on Monday.

This month, Jupiter is in opposition, meaning it is at its closest to our planet (416 million miles away), with its Earth-facing hemisphere fully illuminated by the sun. It will shine especially brightly Friday night and early Saturday morning, when it makes its absolute closest approach.

Never ones to miss an opportunity, NASA and the ESA decided to point the Hubble toward Jupiter while it was in opposition, so that it could capture the atmosphere of the largest planet in the solar system in more detail.

The image it took Monday didn't disappoint. Hubble was able to capture surface features that are just 80 miles across.

"The final image shows a sharp view of Jupiter and reveals a wealth of features in its dense atmosphere," NASA and the ESA, which cooperate on the Hubble project, said in a statement. The picture "reveals the intricate, detailed beauty of Jupiter's clouds as arranged into bands of different latitudes."

Clearly visible in the photo are Jupiter's famous atmospheric bands, created by different-colored clouds. The lighter bands have higher concentrations of frozen ammonia in them, compared with the darker ones, the agencies said.

On the lower left side of the image is Jupiter's famous Great Red Spot, an ongoing larger-than-Earth storm on the gas giant planet's surface. A smaller storm, dubbed "Red Spot Junior," is visible farther south. Winds on the planet can reach up to 400 mph.

"However, as with the last images of Jupiter taken by Hubble and telescopes on the ground, this new image confirms that the huge storm that has raged on Jupiter's surface for at least 150 years continues to shrink," the agencies said. "The reason for this is still unknown. So Hubble will continue to observe Jupiter in the hope that scientists will solve this stormy riddle."

The Hubble Space Telescope was launched into orbit in 1990, and ever since its first photo an underwhelming grainy, black-and-white image of some stars, thanks to a flaw in a primary mirror it has gone on to deliver some truly dazzling images from space. Time magazine has a roundup of the 50 "best" photos taken by Hubble, though all are quite extraordinary in their own way, depending on one's interest in any particular corner of the universe.

NASA has been developing a new telescope, the $8 billion James Webb Space Telescope, that will be able to see back in time, almost to the beginning of the universe. The Webb will be able to collect seven times the starlight as the Hubble and observe the universe in infrared wavelengths of light, which the Hubble can't, The Washington Post's Joel Achenbach reported in February. Eventually, the Webb telescope is expected to replace the Hubble, which "is still working fabulously but getting long in the tooth," Achenbach wrote.

Until then, the Hubble will continue capturing away. The photo released Thursday was part of the Outer Planet Atmospheres Legacy program, according to NASA and the ESA. The program, which allows the telescope to study the outer planets each year, started in 2014 with Uranus and has been observing Jupiter and Neptune since 2015. In 2018, the Hubble will turn its focus to Saturn.

Behold, the Hubble Telescope's latest close-up photo of Jupiter 04/07/17 [Last modified: Friday, April 7, 2017 2:31pm] Photo reprints | Article reprints

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Behold, the Hubble Telescope's latest close-up photo of Jupiter - Tampabay.com

WESTPORT, Conn. Ys Man Marty Yellin will once again share his knowledge of the scientific world, thistime updating the group on the work of the Hubble Telescope.

The Hubble was sent into low Earthorbit in 1990 and remains the most productive astronomical instrument ever built.

Yellin will speak to Ys Men of Westport/Weston on April 13 at the SaugatuckCongregational Church at 245 Post Road E., Westport.

He will speak about some ofthe latest findings from the telescope, with an emphasis on its recent discoveries of manyexoplanets, which seem to have the conditions for life of some kind.

He will also talkabout some of the most recently discovered Black Holes, including showing the first-ever picture of a Black Hole swallowing a star like our Sun.

Yellin earned bachelor's and master's degrees in electrical engineering from CUNY.

He joined Perkin-Elmer, where he was a member of the top-secret Hexagon program,the largest and most successful spy satellite ever to be flown up to that time. He laterworked on the team that designed and fabricated the Hubble Space Telescope.

In his "retirement," Yellin earned a doctorate at New York University in biomedical engineering, then joined aprogram evaluating new approaches to cancer treatment.

If youre a retired or semi-retired man living in Westport or Weston and looking forsomething new, for an active group with over 400 men like yourself, drop by Thursdaymorning.

Coffee, doughnuts and schmoozing are on the agenda as you learn about Ys Men, hear aninteresting speaker, meet old friends and make new ones. Ys Men gets you out of yourhouse and into your choice of over two dozen activities, from bridge to boating to hikingto international affairs and book discussions.

Click here to learn more about the group.

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Satellite Expert To Speak On Hubble Telescope, Exoplanets In Westport - Westport Daily Voice

Hubble stuns once again with an image of a super star cluster called Westerlund 1. A massive star resides here, dwarfing Earth's sun handily.

Westerlund 1, the glittering star cluster that is home to a truly massive hypergiant star, takes center stage in this photo bythe Hubble Space Telescope.

Located about 15,000 light-years away,Westerlund 1 is the cosmic homeofthe giant star Westerlund 1-26, a monster red supergiant star (also known as a hypergiant). The star is so big, its radius is more than 1,500 times that of our sun, NASA officials said in an image description.

"IfWesterlund 1-26 were placed where our sun is in our solar system, it would extend out beyond the orbit of Jupiter," NASA officials wrote.

At around 3 million years old, the Westerlund 1 cluster is a young collection of stars when compared toour own sun which is roughly 4.6 billion years old. This super star cluster likely was birthed in a singleflurry of events making all the stars residing here roughly the same age and composition, NASA officials explained.

Follow us @Spacedotcom, Facebook and Google+. Original article on Space.com.

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Hubble Telescope Snaps Sparkly Photo of Hypergiant Star's Home - Space.com

NASAs Hubble telescope has revealed a real space battle.

Researchers found that around 1400, in theOrion Nebula, a group of stars was engaged in an even more impressive battle.

The gravitational tussle ended with the system breaking apart and at least three stars being ejected in different directions.

The stars went unnoticed for hundreds of years, NASA revealed.

However, over the past few decades, two of them were spotted in infrared and radio observations, which were able to penetrate the thick dust in the Orion Nebula.

The observations showed that the two stars were traveling at high speeds in opposite directions from each other.

The stars origin, however, was a mystery.

Astronomers traced both stars back 540 years to the same location and suggested they were part of a now-defunct multiple-star system.

But the duos combined energy, which is propelling them outward, didnt add up.

The researchers reasoned there must be at least one other culprit that robbed energy from the stellar toss-up.

Now NASAs Hubble Space Telescope has helped astronomers find the final piece of the puzzle by spotting a third runaway star.

The astronomers followed the path of the newly found star back to the same location where the two previously known stars were located 540 years ago.

The trio reside in a small region of young stars called the Kleinmann-Low Nebula, near the center of the vast Orion Nebula complex, located 1,300 light-years away.

All three stars are moving extremely fast on their way out of the Kleinmann-Low Nebula, up to almost 30 times the speed of most of the nebulas stellar inhabitants.

Based on computer simulations, astronomers predicted that these gravitational tugs-of-war should occur in young clusters, where newborn stars are crowded together.

But we havent 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.

What often happens when a multiple system falls apart is that two of the member stars move close enough to each other that they merge or form a very tight binary.

In either case, the event releases enough gravitational energy to propel all of the stars in the system outward.

The energetic episode also produces a massive outflow of material, which is seen in the NICMOS images as fingers of matter streaming away from the location of the embedded source I star.

The teams results will appear in the March 20, 2017 issue of The Astrophysical Journal Letters.

Luhman stumbled across the third speedy star, called source x, while he was hunting for free-floating planets in the Orion Nebula as a member of an international team led by Massimo Robberto of the Space Telescope Science Institute in Baltimore, Maryland.

The team used the near-infrared vision of Hubbles Wide Field Camera 3 to conduct the survey.

During the analysis, Luhman was comparing the new infrared images taken in 2015 with infrared observations taken in 1998 by the Near Infrared Camera and Multi-Object Spectrometer (NICMOS).

He noticed that source x had changed its position considerably, relative to nearby stars over the 17 years between Hubble images, indicating the star was moving fast, about 130,000 miles per hour.

The astronomer then looked at the stars previous locations, projecting its path back in time.

He realized that in the 1470s source x had been near the same initial location in the Kleinmann-Low Nebula as two other runaway stars, Becklin-Neugebauer (BN) and source I.

BN was discovered in infrared images in 1967, but its rapid motion wasnt detected until 1995, when radio observations measured the stars speed at 60,000 miles per hour.

Source I is traveling roughly 22,000 miles per hour.

The star had only been detected in radio observations; because it is so heavily enshrouded in dust, its visible and infrared light is largely blocked.

The three stars were most likely kicked out of their home when they engaged in a game of gravitational billiards, Luhman said.

What often happens when a multiple system falls apart is that two of the member stars move close enough to each other that they merge or form a very tight binary.

In either case, the event releases enough gravitational energy to propel all of the stars in the system outward.

The energetic episode also produces a massive outflow of material, which is seen in the NICMOS images as fingers of matter streaming away from the location of the embedded source I star.

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NASA's Hubble telescope reveals a real space battle - The Marshalltown

Hubble collected this stunning image of galaxy UGC 12591, located in the Pisces-Perseus Supercluster. This hybrid galaxy is a combination of a lenticular and a spiral galaxy and is one of the largest known structures in the Universe.

The Hubble Space Telescope has captured an amazing view of a strange hybrid galaxy 400 million light-years away.

The galaxy, called UGC 12591, is odd because it's a cross betweena typical lenticular and spiral galaxy. It is located in the westernmost reaches of the Pisces-Perseus Supercluster - a vast chain of galaxy clusters that extends across hundreds of millions of light-years. The galaxy is also a fast spinner, rotating at a mind-boggling 1.1 million mph (1.8 million km/h), according to a NASA description. [8 Galaxies With Really Weird Names]

"The galaxy itself is also extraordinary: it is incredibly massive," NASA officials wrote in an image description. The galaxy and its halo together contain several hundred billion times the mass of the sun; four timesmass of the Milky Way."

Using the Hubble Space Telescope astronomers are beginning to understand the mass of UGC 12951, NASA officials added. Scientists are using data from Hubble to establish whether the monster galaxy formed and stretched over time, or if it was formed from two large galaxies colliding at some point in the distant past, they added.

The Pisces-Perseus Supercluster of galaxy clusters, which UGC 12951 calls home, is one of the largest known structures in the universe, NASA officials added.

You can follow us @Spacedotcom and on Facebook & Google+. Original story on Space.com.

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Hubble Telescope Snaps Photo of Massive (and Weird) Hybrid Galaxy - Space.com

The Indian Express

Hubble Space Telescope spots galaxy four times the mass of the Milky way The Indian Express The Hubble space telescope has captured a new image showcasing an incredibly massive galaxy located under 400 million light-years away from the Earth. The galaxy UGC 12591 sits somewhere between a lenticular and a spiral, according to NASA. NASA's Hubble telescope captures image of UGC 12591 galaxyBGR India NASA/ESA Hubble Space Telescope Image Showcases ...SpaceCoastDaily.com Hubble showcases a remarkable galactic hybridPhys.Org all 17 news articles »

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Hubble Space Telescope spots galaxy four times the mass of the Milky way - The Indian Express

By Joshua SokolMar. 8, 2017 , 8:00 AM

It was the early 1990s, and the Carnegie Observatories in Pasadena, California, had emptied out for the Christmas holiday. Wendy Freedman was toiling alone in the library on an immense and thorny problem: the expansion rate of the universe.

Carnegie was hallowed ground for this sort of work. It was here, in 1929, that Edwin Hubble first clocked faraway galaxies flying away from the Milky Way, bobbing in the outward current of expanding space. The speed of that flow came to be called the Hubble constant.

Freedman's quiet work was soon interrupted when fellow Carnegie astronomer Allan Sandage stormed in. Sandage, Hubble's designated scientific heir, had spent decades refining the Hubble constant, and had consistently defended a slow rate of expansion. Freedman was the latest challenger to publish a faster rate, and Sandage had seen the heretical study.

"He was so angry," recalls Freedman, now at the University of Chicago in Illinois, "that you sort of become aware that you're the only two people in the building. I took a step back, and that was when I realized, oh boy, this was not the friendliest of fields."

A 1923 image of the Andromeda galaxy. A cepheid, or variable star (marked VAR!), helped Edwin Hubble determine the vast distance to Andromeda.

The Carnegie Observatories

The acrimony has diminished, but not by much. Sandage died in 2010, and by then most astronomers had converged on a Hubble constant in a narrow range. But in a twist Sandage himself might savor, new techniques suggest that the Hubble constant is 8% lower than a leading number. For nearly a century, astronomers have calculated it by meticulously measuring distances in the nearby universe and moving ever farther out. But lately, astrophysicists have measured the constant from the outside in, based on maps of the cosmic microwave background (CMB), the dappled afterglow of the big bang that is a backdrop to the rest of the visible universe. By making assumptions about how the push and pull of energy and matter in the universe have changed the rate of cosmic expansion since the microwave background was formed, the astrophysicists can take their map and adjust the Hubble constant to the present-day, local universe. The numbers should match. But they don't.

It could be that one approach has it wrong. The two sides are searching for flaws in their own methods and each other's alike, and senior figures like Freedman are racing to publish their own measures. "We don't know which way this is going to land," Freedman says.

But if the disagreement holds, it will be a crack in the firmament of modern cosmology. It could mean that current theories are missing some ingredient that intervened between the present and the ancient past, throwing off the chain of inferences from the CMB to the current Hubble constant. If so, history will be repeating itself. In the 1990s, Adam Riess, now an astrophysicist at Johns Hopkins University in Baltimore, Maryland, led one of the groups that discovered dark energy, a repulsive force that is accelerating the expansion of the universe. It is one of the factors that the CMB calculations must take into account.

Now, Riess's team is leading the quest to pin down the Hubble constant in nearby space and beyond. His goal is not just to refine the number, but to see whether it is changing over time in ways that even dark energyas currently conceivedcan't explain. So far, he has few hints about what the missing factor might be. "I'm really wondering what is going on," he says.

In1927, Hubble was moving beyond the Milky Way with what was then the world's biggest telescope, the 100-inch (2.5-m) Hooker telescope that loomed over Pasadena on top of Mount Wilson. He photographed the faint spiral smudges we know as galaxies and measured the reddening of their light as their motions Doppler-shifted it to longer wavelengths, like the keening of a receding ambulance. By comparing the galaxies' redshifts to their brightness, Hubble stumbled on something revolutionary: The dimmer and presumably farther away a galaxy was, the faster it was receding. That meant the universe was expanding. It also meant the universe had a finite age, beginning in a big bang.

Debate over the Hubble constant, the expansion rate of the universe, has exploded again. Astronomers had mostly settled on a number using a classical techniquethe "distance ladder," or astronomical observations from the local universe on out. But these values conflict with cosmological estimates made from maps of the early universe and adjusted to the present day. The dispute suggests a missing ingredient may be fueling the growth of the universe.

J. You

To pin down the expansion ratehis eponymous constantHubble needed actual distances to the galaxies, not just relative ones based on their apparent brightness. So he began the laborious process of building up a distance ladderfrom the Milky Way to neighboring galaxies to the far reaches of expanding space. Each rung in the ladder has to be calibrated by "standard candles": objects that shift, pulse, flash, or rotate in a way that reliably encodes how far away they are.

The first rung seemed reasonably sturdy: variable stars called cepheids, which ramp up and down in brightness over the course of days or weeks. The length of that cycle indicates the star's intrinsic brightness. By comparing the observed brightness of a cepheid to the brightness inferred from its oscillations, Hubble could gauge its distance. The Mount Wilson telescope was only good enough to see a few cepheids in the nearest galaxies. For more distant galaxies, he assumed that the brightest star in each had the same intrinsic brightness. Even farther out, he assumed that entire galaxies were standard candles, with uniform luminosities.

C. Bickel

They weren't good assumptions. Hubble's first published constant was 500 kilometers per second per megaparsecmeaning that for every 3.25 million light-years he looked out into space, the expanding universe was ferrying away galaxies 500 kilometers per second faster. The number was way offan order of magnitude too fast. It also implied a universe just 2 billion years old, a baby compared with current estimates. But it was a start.

By 1949, construction had finished on the 200-inch (5.1-m) telescope at Palomar in southern Californiajust in time for Hubble to suffer a heart attack. Hubble passed the mantle to Sandage, an ace observer who spent the subsequent decades exposing photographic plates during all-night sessions suspended in the telescope's vast apparatus, shivering and in desperate need of a bathroom break.

With Palomar's higher resolution and light-gathering power, Sandage could pluck cepheids from more distant galaxies. He also realized that Hubble's bright stars were in fact entire star clusters. They were intrinsically brighter and thus farther away than Hubble thought, which, in addition to other corrections, implied a much lower Hubble constant. By the 1980s, Sandage had settled on a value of about 50, which he zealously defended. Perhaps his most famous foil, French astronomer Grard de Vaucouleurs, promoted a competing value of 100. One of the key parameters of cosmology was contested to an embarrassing factor of two.

In the late 1990s, Freedman, having survived Sandage's verbal abuse, was determined to solve the puzzle with a powerful new tool designed with just this job in mind: the Hubble Space Telescope. Its sharp view from above the atmosphere allowed Freedman's team to pick out individual cepheids up to 10 times farther away than Sandage had with Palomar. Sometimes those galaxies happened to host both cepheids and an even brighter beacona type Ia supernova. These exploding white dwarf stars are visible across space and flare to a consistent, maximum brightness. Once calibrated with the cepheids, the supernovae could be used on their own to probe the most distant reaches of space. In 2001, Freedman's team narrowed the Hubble constant to 72 plus or minus eight, a definitive effort that ended Sandage and De Vaucouleurs's feud. "I was done," she says. "I never thought I'd work on the Hubble constant again."

Edwin Hubble poses inside the 200-inch Palomar telescope a few years before his death in 1953.

Ned/Steer/Huchra/Riess; NASA/ESA

But then came the physicist, who had an independent way of calculating the Hubble constant with the most distant, redshifted thing of all: the microwave background. In 2003, the Wilkinson Microwave Anisotropy Probe (WMAP) published its first map showing the speckles of temperature variations on the CMB. The maps provided not a standard candle, but a standard yardstick: a pattern of hotter and colder spots in the primordial soup created by sound waves rippling through the newborn universe.

With a few assumptions about the ingredients in that soupfamiliar particles like atoms and photons, some extra invisible stuff called dark matter, and dark energythe WMAP team could calculate the physical size of those primordial sound waves. That could be compared to the apparent size of the sound waves as recorded in the CMB speckles. The comparison gave the distance to the microwave background, and a value for the expansion rate of the universe at that primordial moment. By making assumptions about how regular particles, dark energy, and dark matter have altered the expansion since then, the WMAP team could tune the constant to its current rate of swelling. Initially, they came up with a value of 72, right in line with what Freedman had found.

But since then, the astronomical measurements of the Hubble constant have inched higher, even as error bars have narrowed. In recent publications, Riess has leapfrogged ahead of competitors like Freedman by using the infrared camera installed in 2009 on the Hubble Telescope, which can both pinpoint the distances to Milky Way cepheids and pick out their faraway, reddish cousins from the bluer stars that tend to surround cepheids. The most recent result from Riess's team is 73.24.

Meanwhile, Planck, a European Space Agency (ESA) mission that has imaged the CMB at higher resolution and greater temperature sensitivity, has settled on 67.8. In statistical terms, the two values are separated by a gulf of 3.4 sigma not quite the 5 sigma that in particle physics signals a significant result, but getting there. "That, I think, is hard to explain as a statistical fluke," says Chuck Bennett, an astrophysicist at Johns Hopkins who led the WMAP team.

Each side is pointing its finger at the other. George Efstathiou, a leading cosmologist for the Planck team at the University of Cambridge in the United Kingdom, says the Planck data are "absolutely rock solid." Fresh off analyzing the first Planck results in 2013, Efstathiou cast his eyes elsewhere. He downloaded Riess's data and published his own analysis with a lower and less-precise Hubble constant. He found the astronomers' outwardly groping ladder "messy," he says.

Allan Sandage, Edwin Hubble's designated scientific heir, consistently defended a lower value for the Hubble constant.

The Carnegie Observatories

In response, the astronomers argue that they are making an actual measurement in the present-day universe, whereas the CMB technique relies on many cosmological assumptions. If the two don't agree, they ask, why not change the cosmology? Instead, "The George Efstathious of the world moved in and said, I'm going to reanalyze all of your data," says the University of Chicago's Barry Madore, who has been Freedman's collaborator and husband since the 1980s. "So what do you do? You have to find a tiebreaker."

Wendy Freedman thought her 2001 study pinned down the Hubble constant, but debate has resumed.

Yuri Beletsky, Carnegie Institution for Science

In the astronomers' corner is a technique called gravitational lensing. Around massive galaxy clusters, gravity itself warps space, forming a giant lens that can bend light from a more distant light source, like a quasar. If the alignment of the lens and quasar is just right, the light can follow several paths to Earth, creating multiple images around the lensing cluster. In even luckier circumstances, the quasar flickers in brightness. That causes each cloned image to flicker, too, but at different times, because the light rays for each image take different paths through the bent space. The delays between the flickers indicate differences in the path lengths; by combining those with the size of the cluster, astronomers can use trigonometry to calculate the absolute distance to the lensing galaxy cluster. Only three gravitational lenses have been rigorously measured this way, with six more under study now. But in late January, astrophysicist Sherry Suyu of the Max Planck Institute for Astrophysics in Garching, Germany, and her collaborators published their current best guess at the Hubble constant. "Our measurement is in agreement with the distance ladder approach," Suyu says.

The cosmologists, meanwhile, have their own sister technique: baryon acoustic oscillations (BAOs). As the universe aged, the same sound wave patterns imprinted on the CMBthe primordial yardstickseeded the nuggets of matter that grew into galaxy clusters. The patterning of galaxies on the sky should preserve the original dimensions of the sound waves, and as before, comparing the apparent scale of the pattern to its calculated actual size leads to a distance. Like the CMB technique, the BAO method makes cosmological assumptions. But over the past few years, it has been yielding Hubble constant values in line with Planck's. The ongoing fourth iteration of the Sloan Digital Sky Survey, a vast galaxy mapping effort, should help refine these measurements.

That's not to say that the bickering distance ladder and CMB teams are simply waiting for other methods to settle the dispute. To firm up the foundation of the distance ladder, the distances to cepheids in the Milky Way, ESA's Gaia mission is trying to find precise distances to about a billion different nearby stars, cepheids included. Gaia, in orbit around the sun beyond Earth, uses the surest of all measures: parallax, or the apparent shift of the stars against the background sky, as the spacecraft swings to opposite sides of its orbit. When Gaia's full data set is released in 2022, it should provide another leap forward in certainty for the astronomers. (Already, Riess has found that his higher Hubble constant persists when he uses the preliminary Gaia results.)

The cosmologists expect to firm up their measurements, too, using the Atacama Cosmology Telescope in Chile and the South Pole Telescope, which can check Planck's high-resolution results. "It's not going to remain ambiguous," says Lyman Page, an astrophysicist at Princeton University. And if the divergent results prove rock solid, it will be up to the theorists to try to close the gap. "The gold is where the model breaks down," Page says. "Confirming the model isblah."

The South Pole Telescope will help astrophysicists map the tiny temperature variations of the cosmic microwave background, refining one Hubble measurement.

Keith Vanderlinde

One fixis to add an extra particle to the standard model of the universe. The CMB offers an estimate of the overall energy budget of the universe soon after the big bang, when it was divided into matter and high-energy radiation. Because of Albert Einstein's famous equivalence E=mc2, energy acted like matter, slowing the expansion of space with its gravity. But matter is a more effective brake. As time passed, radiationphotons of light and other lightweight particles like neutrinoscooled and lost energy, diluting its gravitational influence.

There are currently three known kinds of neutrinos. If there were a fourth, as some theorists have speculated, it would have claimed a little more of the universe's initial energy budget for the radiation side, which would dissipate faster. That, in turn, would mean an early universe that expanded faster than the one predicted by standard cosmology's list of ingredients. Fast-forwarding that adjustment into the present brings the two measurements in line. Yet neutrino detectors haven't turned up any evidence for a fourth kind, and other Planck measurements put a tight cap on the total amount of surplus radiation.

Another possible fix is so-called phantom dark energy. Current cosmological models assume a constant strength for dark energy. If dark energy becomes slightly stronger over time, though, it would explain why the cosmos is expanding faster today than one might guess from looking at the early universe. But critics like Hiranya Peiris, a Planck astrophysicist based at University College London, says variable dark energy seems "ad hoc and contrived." And her work suggests that new neutrino physics doesn't work either. Right now, she says, flaws in the different techniques are more likely than new physics.

For Freedman, now a dean of the field, the only solution to the squabble is to fight fire with firewith new observations of the universe. She and Madore are now preparing a separate measurement calibrated not just with cepheids, but other types of variable stars and bright red giantsusing an automated telescope only 30 centimeters across to study the nearest examples, and the Hubble and Spitzer space telescopes to monitor them in remote galaxies. If she could handle the dark and stormy Sandage, she's ready to stand with Riess and answer the brash challenge from the Planck team. "The message was You guys are wrong. Well, maybe," she says, chuckling. "We'll see."

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A recharged debate over the speed of the expansion of the universe could lead to new physics - Science Magazine