At the beginning of time, all the matter in the universe was compressed into an infinitesimally small point. That tiny speck of everything then exploded and formed the universe.
In some sense, it’s still exploding, expanding at an accelerating rate.
In the past, scientists have looked to the radiation left behind from the Big Bang — its smoking gun — to calculate what the rate of the expanding universe ought to be today.
But new evidence, soon to be published in The Astrophysical Journal, suggests these estimates may be wrong, or at least incomplete.
New observations from the Hubble Space Telescope have indicated that the universe may be expanding 5 to 9 percent faster than predicted by the Big Bang.
Using the Hubble, scientists from across the US were able to painstakingly measure the distance to stars and supernovae in many galaxies.
They then used this data to refine what’s known as the “Hubble constant,” the rate by which the universe expands, as measured by direct observations.
But when this new “Hubble constant” was compared with the estimates from the Big Bang inferences, the numbers just didn’t match.
“You start at two ends, and you expect to meet in the middle if all of your drawings are right and your measurements are right,” Adam Riess, the Nobel laureate at the Space Telescope Science Institute and Johns Hopkins University, who led the project, explained Thursday in a statement.
“But now the ends are not quite meeting in the middle and we want to know why.”
The prediction based on the Big Bang “should match our measurement,” Lucas Macri, a Texas A&M physicist and one of the study’s co-authors, tells me.
“If they don’t … there must be a physical reason why these two things are not agreeing.”
So what accounts for the discrepancy?
Either there’s something about the Big Bang that previous estimates have not accounted for or there are factors that come into play after the Big Bang that scientist don’t yet understand.
Macri highlights four possible explanations.
The first is related to the Big Bang.
) “We’re seeing evidence of a previously unknown subatomic particle that was abundant right after the Big Bang (a.k.a. ‘dark radiation’),” he says.
“If you change the assumptions about what was in the primordial soup, things will have shifted a bit.”
The other possibilities are related to “dark energy” and “dark matter,” the substances that make up most of the universe yet can’t be directly observed.
2) Dark energy — the mysterious force that opposes gravity and is causing the universe to accelerate — “is growing in strength and ‘pushing’ galaxies apart faster than it did before,” he says.
3) Dark matter — matter that we can’t see but that is theorized to exist and make up most of the matter in the universe — “is even weirder than we thought.”
Or it could not so simply be:
4) “Our theory of gravity is incomplete.”
He also mentions that their results aren’t set in stone. “There’s one chance in 1,000 that we got this measurement by accident,” he says.
Physics requires a one in 4 million chance for results to be considered truth. More observations will need to be made.
Macri says he and other researchers will know more soon, especially if they get to use the James Webb Space Telescope, which will replace Hubble in the year 2018.
The James Webb will be able to look much deeper into space than Hubble and can refine the Hubble constant estimate further.
“A modest amount of time with James Webb will allow us to make a very significant improvement on our measurement,” Macri says.
Overall, he says, it’s important to know the exact rate of universal expansion because it will yield a more accurate age of the universe.
“To get the age of the universe you need to have the Hubble constant,” he says. Right now the uncertainty of their estimate is 2.4 percent, which is the best yet. But not good enough.
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The Nobel Prize–winning Laser Interferometer Gravitational-Wave Observatory (LIGO) observatory has already changed the world of astronomy.
When the scientists in the LIGO collaboration announced the first detection of gravitational waves in 2016, it meant they’d discovered a new way to observe the universe.
For the first time, scientists could “listen” to ripples in spacetime created by the collision of massive objects like black holes.
But that was just the beginning. The dream, all along, was to combine gravitational wave detections with observations from more traditional telescopes.
On Monday, a team of thousands of LIGO scientists around the globe published an incredible finding spread throughout several papers in the journal Physical Review Letters.
Not only did these scientists detect, for the first time, the gravitational waves produced from two colliding neutron stars, but they were able to pinpoint their location in the sky and witness the event with optical and electromagnetic telescopes.
The gravitational waves tell physicists how large and how far away the objects are, and allow scientists to recreate the moments before they collided.
Then the observations in optical light and electromagnetic waves fill in the blanks that gravitational waves can’t answer.
They help astronomers nail down exactly what the objects were made out of, and which elements their collisions produced.
In this case, the scientists were able to conclude that the resulting explosion from a neutron star merger produces heavy elements like gold, platinum, and uranium.
On August 17 at 8:41 am, LIGO detected gravitational waves — literal distortions in space and time — passing through Earth.
LIGO is a pair of L-shaped observatories in Washington state and Louisiana that can detect when these waves temporarily squish and stretch the fabric of spacetime around us.
In the past two years, LIGO had detected gravitational waves generated by black holes that had crashed into one another.
When LIGO detects gravitational waves, it automatically sends out alerts to hundreds of scientists across the world. Brown was one of them.
“We got on the phone very quickly, and we realized this was a very loud gravitational wave signal. It blew our socks off,” he says.
On the day of the gravitational wave detection, the scientists immediately got another clue that something big was happening.
Two seconds after LIGO detected the gravitational waves, Fermi, a NASA satellite, detected a gamma-ray burst, one of the most powerful explosions of energy we know of in the universe.
It had long been theorized that neutron star mergers could create gamma-ray bursts. This couldn’t be a coincidence.
But light from the neutron star merger and subsequent explosion would soon dim. And so the LIGO collaboration scientists were suddenly under intense pressure to move quickly.
“The sooner you get telescopes on this thing, the more information you get,” Brown says.
Studying that light, and how it changes, would teach scientists a huge amount about neutron stars and how their collisions transform matter.
This discovery is so exciting because it means we’re truly in a new age of astronomy.
It means scientists can study celestial objects not just in terms of the light or radiation they emit they can also combine those observations with data from gravitational waves.
It means scientists have data on the entirety of this collision. They have data on how the two neutron stars danced around each other, they have data on the moment of impact, and they have extensive data on the aftermath.
Scientists expect to observe more black hole mergers, more neutron star mergers. But stranger, cooler observations may come through as well.
If LIGO and VIRGO continue to be upgraded, it’s possible they could detect gravitational waves still rippling away from the Big Bang.
Or, more excitingly, they could detect sources of gravitational waves that have never been predicted or observed.
“I was a little sad I was not alive for the first moon landing,” Thomas Corbitt, a physicist and LIGO collaborator at Louisiana State University, says.
“But when you see things like this, which are a testament to what people can do when they work together, it really is inspiring, and it teaches us about the universe.”
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Pass it on: Popular Science
An international team of researchers, led by the University of Exeter with contributions from the University of Maryland, made the new discovery by observing glowing water molecules in WASP-121b’s atmosphere using NASA’s Hubble Space Telescope.
Previous research spanning the past decade has indicated possible evidence for stratospheres on other exoplanets, but this is the first time that glowing water molecules have been detected – the clearest signal yet to indicate an exoplanet stratosphere.
To study the gas giant’s stratosphere, scientists used spectroscopy to analyze how the planet’s brightness changed at different wavelengths of light.
Water vapor in the planet’s atmosphere, for example, behaves in predictable ways in response to certain wavelengths of light, depending on the temperature of the water.
At cooler temperatures, water vapor blocks light from beneath it. But at higher temperatures, the water molecules glow.
The phenomenon is similar to what happens with fireworks, which get their colors when metallic substances are heated and vaporized, moving their electrons into higher energy states.
Depending on the material, these electrons will emit light at specific wavelengths as they lose energy. For example, sodium produces orange-yellow light and strontium produces red light.
The water molecules in the atmosphere of WASP-121b similarly give off radiation as they lose energy, but it is in the form of infrared light, which the human eye is unable to detect.
The exoplanet orbits its host star every 1.3 days, and the two bodies are about as close as they can be to each other without the star’s gravity ripping the planet apart.
This close proximity also means that the top of the atmosphere is heated to a blazing hot 2,500 degrees Celsius — the temperature at which iron exists in gas rather than solid form.
In Earth’s stratosphere, ozone traps ultraviolet radiation from the sun, which raises the temperature of this layer of atmosphere.
Other solar system bodies have stratospheres, too – methane is responsible for heating in the stratospheres of Jupiter and Saturn’s moon Titan, for example.
In solar system planets, the change in temperature within a stratosphere is typically less than 100 degrees Celsius. However, on WASP-121b, the temperature in the stratosphere rises by 1,000 degrees Celsius.
Vanadium oxide and titanium oxide gases are candidate heat sources, as they strongly absorb starlight at visible wavelengths, much like ozone absorbs UV radiation.
These compounds are expected to be present in only the hottest of hot Jupiter, such as WASP-121b, as high temperatures are required to keep them in the gaseous state.
Indeed, vanadium oxide and titanium oxide are commonly seen in brown dwarfs, ‘failed stars’ that have some commonalities with exoplanets.
NASA’s forthcoming James Webb Space Telescope will be able to follow up on the atmospheres of planets like WASP-121b with higher sensitivity than any telescope currently in space.
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Pass it on: Popular Science