From a press release of the Space Telescope Science Institute, January 26, 2017:
By using galaxies as giant gravitational lenses, an international group of astronomers using the Hubble Space Telescope have made an independent measurement of how fast the Universe is expanding. The newly measured expansion rate for the local Universe is consistent with earlier findings. These are, however, in intriguing disagreement with measurements of the early Universe. This hints at a fundamental problem at the very heart of our understanding of the cosmos.
The Hubble constant — the rate at which the Universe is expanding — is one of the fundamental quantities describing our Universe. A group of astronomers used the Hubble Space Telescope and other telescopes in space and on the ground to observe five galaxies in order to arrive at an independent measurement of the Hubble constant. This new measurement is completely independent of — but in excellent agreement with — other measurements of the Hubble constant in the local Universe that used Cepheid variable stars and supernovae as points of reference.
However, the value measured by this team, as well as those measured using Cepheids and supernovae, are different from the measurement made by the ESA Planck satellite. But there is an important distinction — Planck measured the Hubble constant for the early Universe by observing the cosmic microwave background.
Credit: ESA/Hubble, NASA, Suyu et al.
The targets of the new study were massive galaxies positioned between Earth and very distant quasars — incredibly luminous galaxy cores. The light from the more distant quasars is bent around the huge masses of the galaxies as a result of strong gravitational lensing. This creates multiple images of the background quasar, some smeared into extended arcs.
Because galaxies do not create perfectly spherical distortions in the fabric of space and the lensing galaxies and quasars are not perfectly aligned, the light from the different images of the background quasar follows paths which have slightly different lengths. Since the brightness of quasars changes over time, astronomers can see the different images flicker at different times, the delays between them depending on the lengths of the paths the light has taken. These delays are directly related to the value of the Hubble constant.
Links: the full STScI press release, including further figures and links to published papers.
From an ESA press release, September 14, 2016 :
The first catalogue of more than a billion stars from ESA’s Gaia satellite was published on September 14, 2016 – the largest all-sky survey of celestial objects to date.
On its way to assembling the most detailed 3D map ever made of our Milky Way galaxy, Gaia has pinned down the precise position on the sky and the brightness of 1.142 billion stars. As a taster of the richer catalogue to come in the near future, this data release also features the distances and the motions across the sky for more than two million stars.
The map projection above shows an all-sky view of stars in the Milky Way and our neighboring galaxies, based on the first year or so of Gaia’s observations. It shows the density of stars observed by Gaia in each portion of the sky. Brighter regions indicate denser concentrations of stars, while darker regions correspond to patches of the sky where fewer stars are observed. Darker regions across the Galactic Plane correspond to dense clouds of interstellar gas and dust that absorb starlight along the line of sight. Many globular and open clusters – groupings of stars held together by their mutual gravity – are also sprinkled across the image.
Note that the faint curved features and dark stripes are not of astronomical origin but rather reflect Gaia’s scanning procedure. As this map is based on observations performed during the mission’s first year, the survey is not yet uniform across the sky. These artefacts will gradually disappear as more data are gathered during the five-year mission.
Links: ESA press release, Gaia sky map.
From a press release of the European Space Agency (ESA), September 5, 2016:
Less than a month before the end of the mission, the Rosetta orbiter’s high-resolution camera has revealed the Philae lander wedged into a dark crack on Comet 67P/Churyumov-Gerasimenko.
Credit: ESA/Rosetta/MPS for OSIRIS Team
The images were taken on September 2 by the OSIRIS narrow-angle camera as the orbiter came within 2.7 km of the surface and show the main body of the lander, along with two of its three legs.
The images also provide proof of Philae’s orientation, making it clear why establishing communications was so difficult following its landing on November 12, 2014.
The discovery comes less than a month before Rosetta descends to the comet’s surface. On September 30, the orbiter will be sent on a final one-way mission to investigate the comet from close up, including the open pits in the Ma’at region, where it is hoped that critical observations will help to reveal secrets of the body’s interior structure.
Link: full Rosetta mission press release, including further images and explanations.
From an article in the New York Times, August 31, 2016:
Geologists in Greenland have discovered evidence for ancient life in rocks that are 3.7 billion years old.
Credit: Allen Nutman/NYT
They are thought to be stromatolites, layers of sediment packed together by microbial communities living in shallow water. They are some 220 million years more ancient than the oldest previously known fossils, also stromatolites, from the Pilbara region of Western Australia.
The find, if confirmed, would make these fossils the oldest on Earth and may change scientific understanding of the origins of life.
Link: the full NYT article.
The Laser Interferometer Gravitational Wave Observatory (LIGO) was a topic of NPR’s Morning Edition, August 17, 2016.
Credit: Caltech/MIT/LIGO Lab
Read a full transcript or listen to the broadcast here (5 min 30s).
From a Berkeley Lab press release (July 21, 2016):
Scientists with the Large Underground Xenon (LUX) dark matter experiment, which operates beneath a mile of rock at the Sanford Underground Research Facility in the Black Hills of South Dakota, have completed their search for the missing matter of the Universe. (See The Cosmos, Section 16.4c, p. 430.)
Although LUX’s sensitivity far exceeded the original expectations of the experiment, it yielded no trace of a dark matter particle. LUX’s extreme sensitivity makes the team confident that if dark matter particles had interacted with the LUX’s xenon target, the detector would almost certainly have seen them. These new limits on dark matter detection will allow scientists to eliminate many potential models for dark matter particles, offering critical guidance for the next generation of dark matter experiments.
While the LUX experiment successfully eliminated a large swath of mass ranges and interaction-coupling strengths where so-called WIMPs might exist, physicists believe the WIMP model itself remains alive and viable.
Links: full LBL press release, LUX homepage.
Adapted from an article in the LA Times (July 15, 2016):
A layer of soot deposited after the K/T extinction event may explain why dinosaurs but not everything else died. (See The Cosmos, A Closer Look 8.5, p. 220.)
Researchers from Japan argue that the 6-mile-wide asteroid slammed into an oil field in the present day Yucatán Peninsula and triggered an inferno that launched a massive cloud of smoke into the sky. The resulting layer of soot that enveloped the globe would have been just the right thing to kill the dinosaurs and most other land-dwelling creatures.
Previous theories have postulated that the asteroid sparked the mass extinction by releasing high levels of sulfuric acid particles in the atmosphere. The particles would have caused complete darkness, near-freezing temperatures and acid rain. However, sulfuric acid particles don’t hang around for very long — and if they did, the results would have been catastrophic for many species besides dinosaurs. Instead, soot from the immense fire caused by the Chicxulub impact was a prime candidate.
The scientists collected soot samples from the thin band of rock that marks the timing of the extinction of dinosaurs and found the same composition from locations around the world. They hypothesize that soot was slowly deposited on land in the five years following the massive collision. The powdery substance is primarily made of black carbon that results from incineration of organic matter.
The tiny particles are about a million times more light-absorbing than carbon dioxide. They would have blocked about 85% of sunlight from reaching Earth and cut rainfall by nearly 80%, creating near-drought conditions, as well as causing temperatures to plummet. In this post-asteroid wasteland, plants began to die off, cutting off the food supply to creatures higher up the food chain — such as the dinosaurs — while allowing smaller mammals, birds and aquatic creatures to survive.
Link: the LA Times article
From a report in the New York Times by Nicholas St Fleur:
Continents cruise in the slow lane. Moving just millimeters at a time, it took the ancient supercontinent Pangea hundreds of millions of years to break apart into today’s landmasses. But a study published Tuesday shows that the journey wasn’t always a leisurely drive. When under extreme strain, the tectonic plates hit the throttle and accelerated to speeds 20 times faster than they were traveling before.
Credit: Sascha Brune
After analyzing seismic data from across the world and building a model, a team of geophysicists have discovered that plates move in two distinct phases: a slow phase and a fast one. During the slow phase, the continental crusts, which can be more than 20 miles thick, are stretched out little by little while remaining connected. But then suddenly, one or both of the continents step on the gas pedal. A critical point is reached when the connection between the two continents becomes so weak it can no longer resist the forces trying to pull it apart. This acceleration is directly related to the thinning of the crust.
Links: NYT article; computer simulation illustrating the movement of different continents.
From JPL press releases, July 4, 2016:
While Americans celebrated the evening of Independence Day, 1.7 billion miles (2.7 billion kilometres) NASA’s Juno spacecraft, launched nearly five years ago, reached its final destination: the most massive planet in our Solar System, Jupiter.
Juno now starts its tour of Jupiter in a 53.5-day orbit. The spacecraft saves fuel by executing a burn that places it in a capture orbit with a 53.5-day orbit instead of going directly for the 14-day orbit that will occur during the mission’s primary science collection period. The 14-day science orbit phase will begin after the final burn of the mission for Juno’s main engine on October 19.
Most of Juno’s instruments deal with Jupiter’s particles and magnetic field, which is 20,000 times more powerful than Earth’s. The main instruments are in a vault made of 400 pounds of titanium to protect them from the strong radiation. The Junocam, its imaging camera, is outside that protection, and may not last as long as other instruments; further, it will give images as it rotates that will have to be transformed to the equivalent of steady views.
Links: Full details via the JPL press release; NASA Juno mission page; NY Times: Jupiter and its moons graphic.
A report published on June 30, 2016, in the journal Science indicates that the hole in the ozone layer above Antarctica shows signs of beginning to heal. Since its discovery in 1985 the ozone hole has grown bigger each Spring, reaching a size of 10.9 million square miles in 2015.
The main cause of the hole is man-made chemicals known as CFCs (chlorofluorocarbons), which were widely used as propellants, refrigerants and solvents until they were banned by an international treatment in 1987 – use of CFCs had to be phased out by 1996. However, CFCs in the atmosphere are long-lived, so it will be decades, possibly centuries, before the ozone layer can fully repair itself. Naturally-released sulphur gases, for example, from volcanic eruptions can also affect the ozone layer, acting to slow its recovery.
Links: LA Times article; Science news feature and video.