Researchers have hypothesized that the universe contains a 'dark matter.' They have also posited the existence of a 'dark energy.' These two hypotheses account for the movement of stars in galaxies and for the accelerating expansion of the universe. But -- according to a researcher at UNIGE -- these concepts may be no longer valid: the phenomena can be demonstrated without them. This research exploits a new theoretical model based on the scale invariance of the empty space.
Municipalities, enterprises, and households are switching to LED lights in order to save energy. But these savings might be lost if their neighbors install new or brighter lamps. Scientists fear that this 'rebound effect' might partially or totally cancel out the savings of individual lighting retrofit projects, and make skies over cities considerably brighter.
Astronomers have discovered some of the oldest stars in our Milky Way galaxy by determining their locations and velocities, according to a study led by scientists at Georgia State University.
Gemini Observatory provided key observations in characterizing an object visiting from outside our solar system, 'Oumuamua. After the object was discovered by Pan-STARRS1 on Haleakala, both Gemini telescopes dropped everything to observe 'Oumuamua for three nights as it quickly dimmed from view. Researchers found that despite its interstellar origin, the object is similar in composition to some objects in our Solar System but its shape is unlike anything found around our Sun.
For the first time ever astronomers have studied an asteroid that has entered the Solar System from interstellar space. Observations from ESO's Very Large Telescope in Chile and other observatories around the world show that this unique object was traveling through space for millions of years before its chance encounter with our star system. It appears to be a dark, reddish, highly-elongated rocky or high-metal-content object.
The vault-like, 40-foot diameter, 40-ton door of Chamber A at NASA's Johnson Space Center in Houston was unsealed on Nov. 18, signaling the end of cryogenic testing for NASA's James Webb Space Telescope.
Objects scattered to the inner region of the Solar System by Jupiter's growth brought most of the water now found on Earth. Authors of an journal Icarus article describe a computational model which simulates the gravitational interaction between celestial bodies during the era of planet formation, also providing basis for the hypothesis of the dragging of water-rich "planetesimals".
Using more than half a century of observations, Japanese astronomers have discovered that the microwaves coming from the Sun at the minimums of the past five solar cycles have been the same each time, despite large differences in the maximums of the cycles. This is an important step in understanding the creation and amplification of solar magnetic fields, which generate sunspots and other solar activity.
There are too many high-energy positrons in the cosmic rays reaching the Earth. These positrons (particles that are antimatter equivalents of electrons) could be being produced by pulsars in our vicinity. The most recent measurements from the HAWC Observatory in Mexico have practically excluded this possibility, strengthening the competing and much more exotic hypothesis concerning the origin of the excess positrons.
Researchers working with the High-Altitude Water Cherenkov (HAWC) Gamma-Ray Observatory have made the first detailed measurements of two pulsars suspected as the source of a mysterious positron accumulation near Earth. Despite being the right age and the right distance from Earth, the pulsars lie within an extended murky cloud that prevents most positrons from escaping. The results suggest there must be an alternate explanation for the positron excess -- perhaps one involving dark matter.