Tonight begins a series of three “supermoons” in a row. The July full Moon arrives Saturday morning (12 July) at 7:25 am EDT (1125 GMT); that’s about 21 hours before the Moon arrives at the closest point in is orbit to Earth, a mere 358,284 km distant. This combination of circumstances, illustrated in the diagram above, is known as a “perigee moon,” a “perigean full moon,” or — more more commonly in the news media — a “supermoon”. By a quirk of orbital mechanics, the full Moons of summer 2014 (12 July, 10 August, and 9 September) will all be supermoons. Of these, the August full Moon is even closer (356,922 km), making it the closest full Moon of 2014.
There are several popular myths associated with supermoons: they’re much larger and brighter than ordinary full Moons, they can cause earthquakes, they trigger flooding. None, of course, are true. In fact, the difference in apparent angular size and brightness between a supermoon and their more common cousins is so slight as to be not discernible by typical observers.
Still, it’s worth having a look outside over the next two nights to see our nearest neighbor as big, bright, and beautiful as it ever gets.
(Photo credits. Top: the blogger. Bottom: NASA.)
A skywatcher “lifts up” the star clouds of our home galaxy in an amazing photograph. Astrophotographer Miguel Claro took this photo in the Azores, Portugal, on 4 May 2014. The constellation Sagittarius glows at the left, with Scorpius on the right. The Milky Way runs diagonally through the photo at left, bisected by a dark lane of absorbing dust.
Just in time for World Cup 2014 madness: a dying star puffs out a “soccer ball” in space. This object is known as Kronberger 61 and is an example of a planetary nebula, so named for their resemblance in early telescopes to distant Solar System planets like Uranus and Neptune.
As a star with roughly the mass of the Sun ends the main phase of life, having exhausted its supply of hydrogen fuel, its core contracts and its outer layers expand. For a few tens of millions of years, it shines brightly as a red giant star, fusing the helium ash of its former hydrogen-burning existence into carbon. Eventually even the helium runs out, and the core contracts further; despite vastly increased core temperatures, it is unable to fuse the carbon and the star’s life effectively runs out.
The red giant then sheds its outer layers to space, creating a planetary nebula. The core, consisting mostly of carbon, some oxygen and a little leftover helium, is exposed and becomes known as a white dwarf. A shadow of its former self, this “star” will cool over billions of years as remnant interior heat from the fires of nuclear fusion in its past slowly radiate away. The outer layers of the star blown out into space become seed material for future generations of stars.
The oldest white dwarf stars in the Universe may now have surface temperatures similar to those of household ovens. In the distant future of the Universe, these stars should cool until they come into equilibrium with the cosmic background radiation as “black dwarfs”.
Very few planetary nebulae are this spherical, says astronomer George Jacoby of the Giant Magellan Telescope Organization in Pasadena, California, who helped image the nebula with the Gemini North Telescope in Hawaii. “They’re usually elongated and look like butterflies and other objects,” he said. The origin of the complex structures seen among planetary nebulae is still not well understood by astronomers.
In terms of the mass required to produce a planetary nebula, “The sun is right on the edge of being able to do this. It’s not quite massive enough,” Jacoby said. “I suspect it’ll have trouble.”
The new soccer-ball nebula image was presented Monday at an International Astronomical Union symposium in Puerto de la Cruz, Spain.
Cosmic violence revealed in new NASA/NRAO image of colliding galaxy clusters MACS J0717+3745. Researchers attending the American Astronomical Society’s meeting in Boston, Mass., released this image today made from data collected by the Karl G. Jansky Very Large Array (VLA), the Chandra X-Ray Observatory, and the Hubble Space Telescope. It shows a region of space more than 5 billion light-years from Earth where complex physical process are taking place that scientists don’t fully understand.
From the NASA press release: “The HST image forms the background of this composite, with the X-ray emission detected by Chandra in blue and radio emission seen by the VLA in red. The X-rays indicate hot, tenuous gas that pervades the region containing the galaxy clusters. The large, oddly-shaped red feature at the center probably is a region where shocks caused by the collisions are accelerating particles that then interact with magnetic fields and emit the radio waves. ‘The complex shape of this region is unique; we’ve never spotted anything like this before,’ said Reinout van Weeren, an Einstein Fellow at the Harvard-Smithsonian Center for Astrophysics.”
A larger version of the image can be found here.
The NASA Cassini spacecraft orbiting Saturn spies its next most-distant planetary neighbor for the first time. This image made by Cassini on 11 April 2014 looks across Saturn’s rings in the foreground and includes the planet Uranus, some 1.4 billion kilometers more distant (upper left). While the rings show mostly golden hues of light reflected from ice and rock, distant Uranus is blue; molecules like methane in its atmosphere preferentially absorb blue light and reflect the blues and greens back to space.
A rare annular solar eclipse happens in a few hours, and no one on Earth will see it. Solar eclipses themselves are not all that unusual, but one happens tonight (daytime in the eastern hemisphere) that’s only happened a few times in the past thousand years. Due to a particular arrangement of the Moon in its orbit around the Earth and the point in Earth’s orbit where we are today, the dark, central part of the Moon’s shadow sweeping past the Earth will barely graze our planet, and for less than a minute over one of the most remote places on Earth.
Called a “non-central antumbral" eclipse, in this case the deepest part of the Moon’s shadow will touch the Earth for all of 43 seconds in a far-flung corner of Antarctica. The Moon is just far enough from Earth right now that it’s face will not completely cover the Sun’s disc from this location; rather, it will leave a thin sliver of sunlight all the way around the Sun in an event often called a "ring of fire”. The third image above is a simulation of how the event would look from a few hundred feet above Antarctica at mid-eclipse; the ring of fire just touches the horizon.
Although only penguins might see this sight, it is possible that some Earth-orbiting spacecraft may glimpse it too. The European Space Agency’s Sun observing Proba-2 (aka “Solar B”) satellite and NASA/JAXA Hinode probe could find themselves in just the right place at the right time and see what no human eyes can reveal. The eclipse begins shortly before 06:00 GMT.