New Horizons Flies By Neptune Exactly 25 Years After Voyager 2 In what NASA is calling a “cosmic coincidence” the New Horizons probe makes its flyby of Neptune on the 25th anniversary of Voyager 2’s Neptune encounter. On August 25, 1989, Voyager 2 made its closest flyby of Neptune, making it the first spacecraft to study the planet. During Voyager 2’s flyby, it discovered a massive anticyclonic storm system called the Great Dark Spot, similar to Jupiter’s Great Red Spot. Today, NASA’s New Horizons probe is embarking on an equally exciting journey to another world never before visited by a spacecraft. When the spacecraft arrives on July 14, 2015, it will provide the first detailed images of Pluto. The dwarf planet is so distant from us that even images captured by the Hubble Space Telescope appear blurry. Read more about the New Horizons mission and Voyager 2’s flyby of Neptune here:
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Buzz Aldrin: I made a new friend at the #ChelseaFinale named Dave Grohl and he’s on board with GetYourAssToMars. Who’s with us?

Eta Carinae: our neighboring superstars

The Eta Carinae star system does not lack for superlatives. Not only does it contain one of the biggest and brightest stars in our galaxy, weighing at least 90 times the mass of the sun, it is also extremely volatile and is expected to have at least one supernova explosion in the future.
As one of the first objects observed by NASA’s Chandra X-ray Observatory after its launch some 15 years ago, this double star system continues to reveal new clues about its nature through the X-rays it generates.
Astronomers reported extremely volatile behavior from Eta Carinae in the 19th century, when it became very bright for two decades, outshining nearly every star in the entire sky. This event became known as the “Great Eruption.” Data from modern telescopes reveal that Eta Carinae threw off about ten times the sun’s mass during that time. Surprisingly, the star survived this tumultuous expulsion of material, adding “extremely hardy” to its list of attributes.
Today, astronomers are trying to learn more about the two stars in the Eta Carinae system and how they interact with each other. The heavier of the two stars is quickly losing mass through  wind streaming away from its surface at over a million miles per hour. While not the giant purge of the Great Eruption, this star is still losing mass at a very high rate that will add up to the sun’s mass in about a millennium. 
Though smaller than its partner, the companion star in Eta Carinae is also massive, weighing in at about 30 times the mass of the sun. It is losing matter at a rate that is about a hundred times lower than its partner, but still a prodigious weight loss compared to most other stars. The companion star beats the bigger star in wind speed, with its wind clocking in almost ten times faster.
When these two speedy and powerful winds collide, they form a bow shock – similar to the sonic boom from a supersonic airplane – that then heats the gas between the stars. The temperature of the gas reaches about ten million degrees, producing X-rays that Chandra detects.
The Chandra image of Eta Carinae shows low energy X-rays in red, medium energy X-rays in green, and high energy X-rays in blue. Most of the emission comes from low and high energy X-rays. The blue point source is generated by the colliding winds, and the diffuse blue emission is produced when the material that was purged during the Great Eruption reflects these X-rays. The low energy X-rays further out show where the winds from the two stars, or perhaps material from the Great Eruption, are striking surrounding material. This surrounding material might consist of gas that was ejected before the Great Eruption.     An interesting feature of the Eta Carinae system is that the two stars travel around each other along highly elliptical paths during their five-and-a-half-year long orbit. Depending on where each star is on its oval-shaped trajectory, the distance between the two stars changes by a factor of twenty. These oval-shaped trajectories give astronomers a chance to study what happens to the winds from these stars when they collide at different distances from one another.
Throughout most of the system’s orbit, the X-rays are stronger at the apex, the region where the winds collide head-on. However, when the two stars are at their closest during their orbit (a point that astronomers call “periastron”), the X-ray emission dips unexpectedly. To understand the cause of this dip, astronomers observed Eta Carinae with Chandra at periastron in early 2009. The results provided the first detailed picture of X-ray emission from the colliding winds in Eta Carinae. The study suggests that part of the reason for the dip at periastron is that X-rays from the apex are blocked by the dense wind from the more massive star in Eta Carinae, or perhaps by the surface of the star itself.  Another factor responsible for the X-ray dip is that the shock wave appears to be disrupted near periastron, possibly because of faster cooling of the gas due to increased density, and/or a decrease in the strength of the companion star’s wind because of extra ultraviolet radiation from the massive star reaching it. Researchers are hoping that Chandra observations of the latest periastron in August 2014 will help them determine the true explanation.

Image credit: NASA/CXC/GSFC/K.Hamaguchi, et al.

Witnessing the early growth of a giant

Astronomers have uncovered for the first time the earliest stages of a massive galaxy forming in the young Universe. The discovery was made possible through combining observations from the NASA/ESA Hubble Space Telescope, NASA’s Spitzer Space Telescope, ESA’s Herschel Space Observatory, and the W.M. Keck Observatory in Hawaii. The growing galaxy core is blazing with the light of millions of newborn stars that are forming at a ferocious rate.
Elliptical galaxies are large, gas-poor gatherings of older stars and are one of the main types of galaxy along with their spiral and lenticular relatives. Galaxy formation theories suggest that giant elliptical galaxies form from the inside out, with a large core marking the very first stages of formation.

However, evidence of this early construction phase has eluded astronomers — until now.
Astronomers have now spotted a compact galactic core known as GOODS-N-774, and nicknamed Sparky. It is seen as it appeared eleven billion years ago, just three billion years after the Big Bang.
"This core formation process is a phenomenon unique to the early Universe,"explains Erica Nelson of Yale University, USA, lead author of the science paper announcing the results, "we do not see galaxies forming in this way any more. There’s something about the Universe at that time that could form galaxies in this way that it now can’t. We suspect that the Universe could produce denser objects because the Universe as a whole was denser shortly after the Big Bang. It is much less dense now, so it can’t do it anymore."
Although only a fraction of the size of the Milky Way, the infant galaxy is crammed with so many young stars that it already contains twice as much mass as our entire galaxy. It is thought that the fledgling galaxy will continue to grow, eventually becoming a giant elliptical galaxy. The astronomers think that this barely visible galaxy may be representative of a much larger population of similar objects that are too faint or obscured by dust to be spotted — just like the Sun can appear red and faint behind the smoke of a forest fire.
Alongside determining the galaxy’s size from the Hubble images, the team dug into archival far-infrared images from NASA’s Spitzer Space Telescope and the ESAHerschel Space Observatory to see how fast the compact galaxy is churning out stars. GOODS-N-774 is producing 300 stars per year. "By comparison, the Milky Way produces thirty times fewer than this — roughly ten stars per year," says Marijn Franx of Leiden University in the Netherlands, a co-author of the study. "This star-forming rate is really intense!"
This tiny powerhouse contains about twice as many stars as our galaxy, all crammed into a region only 6000 light-years across. The Milky Way is about 100 000 light-years across.
Astronomers believe that this frenzied star formation occurs because the galactic centre is forming deep inside a gravitational well of dark matter, an invisible form of matter that makes up the scaffolding upon which galaxies formed in the early Universe. A torrent of gas is flowing into the well and into the compact galaxy, sparking waves of star birth.
The sheer amount of gas and dust within an extreme star-forming region like this may explain why they have eluded astronomers until now. Bursts of star formation create dust, which builds up within the forming core and can block some starlight— GOODS-N-774 was only just visible, even using the resolution and infrared capabilities of Hubble’s Wide Field Camera 3.

Image credit: NASA, ESA, Z. Levay and G. Bacon (Space Telescope Science Institute)

The mix of colors in this photo of an aurora from Reid Wiseman aboard the ISS is amazing. The thin strip of deep blue is the first glimpse of sunrise.

Mapping the Mass of an Enormous Galaxy Cluster

  You are looking at the most precise gravity map ever made of a distant galaxy cluster. Using the map, astronomers have determined that the cluster is roughly 650,000 light-years across and contains enough matter to make 160 trillion suns.
  Image: ESA/Hubble, NASA, HST Frontier Fields Acknowledgement: Mathilde Jauzac (Durham University, UK and Astrophysics & Cosmology Research Unit, South Africa) and Jean-Paul Kneib (École Polytechnique Fédérale de Lausanne, Switzerland)
  The cluster, known as MCS J0416.1–2403, is located about 4 billion light-years away and consists of hundreds of galaxies all orbiting one another. Newton’s gravitational equations can tell you the mass of two objects orbiting one another, provided you already know the mass of one of them. However, because these galaxies are all so distant, there is no way for scientists to determine any of their individual masses.
  But there is another way. Einstein’s theory of general relativity tells us that heavy objects warp the fabric of space-time around them. As light travels through these warped regions it will become distorted, and we see that as smeared out rings and arcs in our telescopes, an effect known as gravitational lensing. Using the Hubble space telescope, astronomers identified smudges in the light seen around MCS J0416.1–2403. These distortions are images of even more distant galaxies sitting behind the cluster; their light has been lensed by its enormous mass. By carefully determining just how much the light is smeared out, researchers can calculate the amount of matter sitting within the galaxy cluster.
  The 160 trillion solar masses includes both visible matter and dark matter, which gives off no light but makes up the bulk of the cluster’s mass. By studying the dynamics of all the galaxies within the cluster, astronomers can better understand this mysterious substance. Researchers will also continue mapping the smeared out images to increase the precision of their mass calculations, learning about the cluster’s finer details to figure out its history and evolution.

Crescent Moon (NASA, International Space Station Science, 11/03/07) | NASA’s Marshall Space Flight Center