Brown dwarfs, sometimes called failed stars, are a hot topic in astronomy right now. Smaller than stars and bigger than giant planets, they hold promise for helping us understand both stellar evolution and planet formation. New work by a team of astronomers has discovered several ultra-cool brown dwarfs in our own solar neighborhood. In essence, they are hiding in plain sight.
As we all learned in elementary school, Alpha Centauri is the closest star system to the Solar System. At a distance of 4.37 light-years (25 trillion miles), it consists of three stars -- the pair Alpha Centauri A and Alpha Centauri B and a small and faint red dwarf, Proxima Centauri, which may or may not be gravitationally bound to the other two stars. Astronomers using ESO telescopes have found clear evidence of a planet orbiting this third star, Proxima Centauri. This long-sought world, designated Proxima b, orbits its cool red parent star every 11 days and has a temperature suitable for liquid water to exist on its surface. This rocky world is a little more massive than the Earth and is the closest exoplanet to us. It may also be the closest possible abode for life outside the Solar System.
Lie on the beach this summer and your body will be bombarded by about one sextillion photons of light per second. Most of these photons originate from the Sun. But a very small fraction have traveled across the Universe for billions of years before ending up on your skin. Astronomers have now accurately measured the light hitting the Earth from outside our galaxy over a very broad wavelength range and it amounts to about only ten trillionths of your suntan.
The Crab Nebula is the remnant of a supernova explosion that was observed on Earth in the year 1054. The pulsar at the center of the Crab Nebula is extremely small, with a diameter of just around ten kilometers, and rotates around its own axis at approximately 30 times per second. Thus, it emits light pulses like a lighthouse and these pulses stretch across the entire electromagnetic spectrum -- from long radio waves, to visible light, to the short waves of energetic gamma rays. Recent observations show that the Crab Pulsar has now set a new record. It is sending out the most energetic light radiation, in the form of photons, that has ever been measured from a star. This could challenge our current understanding of pulsars.
One of the biggest problems when studying black holes is that the laws of physics as we know them cease to apply. The conventional wisdom is that in a black hole, large quantities of matter and energy concentrate in an infinitely small space (known as a gravitational singularity), space-time curves towards infinity, and all matter is destroyed... Or is it? New research at the Universitat de Valencia in Spain suggests that if the singularity is treated as an imperfection in the geometric structure of space-time, matter may indeed survive its foray into the black hole and come out the other side -- And by doing so, resolve the problem of the infinite, space deforming, gravitational pull.
Jupiter's Red Spot is the greatest storm on the grandest planet in the Solar System -- a colossal hurricane with 400 mile per hour winds that makes Earth's worst gales look positively tranquil. Discovered within years of Galileo's introduction of telescopic astronomy in the 17th Century, its swirling pattern of colorful gases is often called a "perpetual hurricane." The Red Spot has varied in size and color over the centuries and spans a distance equal to three earth diameters. It has winds that take six days to complete one spin. Now, a team of astronomers from Boston University and the University of Leicester in the UK think they have found the solution to some of the mysteries surrounding Jupiter's iconic Great Red Spot.
Astronomers at the University of Michigan have discovered that the hot gas in the halo of the Milky Way galaxy is spinning in the same direction and at a comparable speed to the galaxy's spiral-shaped disk. Until now, people have assumed that the disk of the Milky Way spins at a high speed, while the enormous reservoir of hot gas in the halo is stationary. But that is wrong -- The hot gas in the halo appears to be rotating almost as fast as the disk.
Celebrating its 50th anniversary this year, the TV series "Star Trek" captured the public's imagination with the signature phrase "To boldly go where no one has gone before." As we all know, the Hubble Space Telescope simply orbits Earth and doesn't "boldly go" anywhere. But it looks deeper into the universe than ever before to explore the fabric of time and space and find the farthest objects ever seen. This is epitomized in this Hubble image that is part of its Frontier Fields program to probe the far universe. This view of a massive cluster of galaxies unveils a very cluttered-looking universe filled with galaxies near and far. Some are distorted as in a funhouse mirror through gravitational lensing -- a warping of space phenomenon first predicted by Einstein a century ago.
Earth's atmosphere is leaking. Every day, around 90 tons of material -- consisting primarily of oxygen, hydrogen, and helium ions -- escapes from our planet's upper atmosphere and streams out into space. Although missions such as ESA's fleet of four Cluster spacecraft flying in formation around Earth have long been investigating this leakage, there are still many open questions. How and why is Earth losing its atmosphere. How do the ions escape? Where do they originate? What processes are at play?
You can never predict what treasure might be hiding in your own basement. The Carnegie Institution for Science didn't know it, but it turns out that a 1917 image on an astronomical glass photographic plate from the Carnegie Observatory archives shows the first-ever evidence of a planetary system beyond our own Sun. This accidental (and highly unexpected) find was recognized by Jay Farihi of University College in London, while researching an article about planetary systems surrounding white dwarf stars.
Mercury passes between Earth and the Sun only about 13 times a century, with its last trek taking place in 2006. Due to its diminutive size, viewing this event safely requires a telescope or high-powered binoculars fitted with solar filters made of specially-coated glass or Mylar. Mercury will appear as a small black dot as it crosses the edge of the Sun and into view at 7:12 AM EDT. The planet will make a leisurely journey across the face of the Sun, reaching mid-point at approximately 10:47 AM EDT, and exiting the golden disk at 2:42 PM EDT. The entire 7.5 hour path across the Sun will be visible across the United States, Canada, Europe, South America, Africa, and most of Asia.
Our senses experience space-time in a continuous way, without gaps or discontinuities, just as described by classical physics. In quantum physics however, the texture of space-time is granular at tiny scales (below the so-called Planck scale of 10^-33 cm), as if it were a variable mesh of discrete solids and voids. What happens at the classical physics to quantum physics boundary of space-time? Is there an abrupt change or is there a gradual transition? A recent theoretical study led by the International School for Advanced Studies (SISSA) in Trieste, Italy, has developed a model to help find this transition boundary. What makes this model most unique, and no doubt highly precious, is that it is formulated in such a way as to make experimental testing possible. The team is already collaborating on developing an experiment, which will take place at the European Laboratory for Non-linear Spectroscopy (LENS) in Florence, Italy.
A team of astronomers has discovered one of the youngest and brightest free-floating, planet-like objects in relatively close proximity to the Sun. Only 95 light years away and at an age of only 10 million years, which means it's practically a baby on a galactic time scale, the object is between four and eight times the mass of Jupiter, and hence falls in the mass range between a large planet and a small brown dwarf star. Free-floating exo-planet analogs such as this are much easier to scrutinize than planets orbiting around stars since they are drifting in space all alone and observations are not overwhelmed by the brightness of a host star sitting right next door.
An international team of scientists has found evidence, in the form of radioactive iron-60 in sediment and crust samples taken from the Pacific, Atlantic, and Indian Oceans, which is indicative of a series of massive supernova explosions that showered the Earth with radioactive debris between 3.2 and 1.7 million years ago. The scientists believe the series of supernovae were less than 300 light years away -- Close enough to be visible during the day and comparable to the brightness of the Moon at night. Although Earth would have been exposed to an increased cosmic ray bombardment, the radiation would have been too weak to cause direct biological damage or trigger mass extinctions.
The baffling and strange behavior of black holes has become somewhat less mysterious recently. As we know, super-massive black holes don't give off any light themselves, but are often encircled by disks of hot, glowing material. The gravity of a black hole pulls swirling gas into it, heating this material and causing it to shine brightly in multiple wavelengths. Another source of radiation near a black hole is the corona, which is made up of highly energetic particles that generate massive amounts of X-rays. In September 2014, NASA's Explorer missions Swift and NuSTAR caught Markarian 335, a super-massive black hole near the constellation Pegasus, in a huge flare. After careful scrutiny, the astronomers realized they were seeing the ejection, and eventual collapse, of the black hole's corona shooting away at about 20 percent the speed of light.
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