May 21, 2016

The Rosette Nebula

The Rosette Nebula x rayThe Rosette Nebula optical

  • The Rosette Nebula is a star-forming region about 5,000 light years from Earth.
  • X-rays from Chandra reveal about 160 stars in the cluster known as NGC 2237 (right side of the image).
  • Combining X-ray and optical data, astronomers determined that the central cluster formed first, followed by neighboring ones including NGC 2237.

This composite image shows the Rosette star formation region, located about 5,000 light years from Earth. Data from the Chandra X-ray Observatory are colored red and outlined by a white line (roll your mouse over the image above). The X-rays reveal hundreds of young stars clustered in the center of the image and additional fainter clusters on either side. These clusters are labeled in the X-ray only image, where they are more obvious to the eye. Optical data from the Digitized Sky Survey and the Kitt Peak National Observatory (purple, orange, green and blue) show large areas of gas and dust, including giant pillars that remain behind after intense radiation from massive stars has eroded the more diffuse gas.

A recent Chandra study of the cluster on the right side of the image, named NGC 2237, provides the first probe of the low-mass stars in this satellite cluster. Previously only 36 young stars had been discovered in NGC 2237, but the Chandra work has increased this sample to about 160 stars. The presence of several X-ray emitting stars around the pillars and the detection of an outflow -- commonly associated with very young stars -- originating from a dark area of the optical image indicates that star formation is continuing in NGC 2237 (the outflow and some of the pillars are labeled in a close-up view). By combining these results with earlier studies, the scientists conclude that the central cluster formed first, followed by expansion of the nebula, which triggered the formation of the neighboring clusters, including NGC 2237.

Image Credit: X-ray (NASA/CXC/SAO/J. Wang et al), Optical (DSS & NOAO/AURA/NSF/KPNO 0.9-m/T. Rector et al)
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Globular Cluster Messier 56

Globular Cluster Messier 56

The NASA/ESA Hubble Space Telescope has produced this beautiful image of the globular cluster Messier 56 (also known as M 56 or NGC 6779), which is located about 33 000 light years away from the Earth in the constellation of Lyra (The Lyre). The cluster is composed of a large number of stars, tightly bound to each other by gravity.

However, this was not known when Charles Messier first observed it in January 1779. He described Messier 56 as “a nebula without stars”, like most globular clusters that he discovered — his telescope was not powerful enough to individually resolve any of the stars visible here, making it look like a fuzzy ball through his telescope’s eyepiece. We clearly see from Hubble’s image how the development of technology over the years has helped our understanding of astronomical objects.

Astronomers typically infer important properties of globular clusters by looking at the light of their constituent stars. But they have to be very careful when they observe objects like Messier 56, which is located close to the Galactic plane. This region is crowded by “field-stars”, in other words, stars in the Milky Way that happen to lie in the same direction but do not belong to the cluster. These objects can contaminate the light, and hence undermine the conclusions reached by astronomers.

A tool often used by scientists for studying stellar clusters is the colour-magnitude (or Hertzsprung-Russell) diagram. This chart compares the brightness and colour of stars – which in turn, tells scientists what the surface temperature of a star is.

By comparing high quality observations taken with the Hubble Space Telescope with results from the standard theory of stellar evolution, astronomers can characterise the properties of a cluster. In the case of Messier 56, this includes its age, which at 13 billion years is approximately three times the age of the Sun. Furthermore, they have also been able to study the chemical composition of Messier 56. The cluster has relatively few elements heavier than hydrogen and helium, typically a sign of stars that were born early in the Universe’s history, before many of the elements in existence today were formed in significant quantities.

Astronomers have found that the majority of clusters with this type of chemical makeup lie along a plane in the Milky Way’s halo. This suggests that such clusters were captured from a satellite galaxy, rather than being the oldest members of the Milky Way's globular cluster system as had been previously thought.

This image consists of visible and near-infrared exposures from Hubble’s Advanced Camera for Surveys. The field of view is approximately 3.3 by 3.3 arcminutes.

Image Credit: NASA, ESA, Gilles Chapdelaine
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Total Solar Eclipse seen from plane above Turkana

Total Solar Eclipse seen from plane

Plane above Turkana, Kenya
November 3, 2013

Image Credit & Copyright: Catalin Beldea

May 20, 2016

Mars Near 2016 Opposition

Mars Opposition

Bright, frosty polar caps, and clouds above a vivid, rust-colored landscape reveal Mars as a dynamic seasonal planet in this NASA Hubble Space Telescope view taken on May 12, 2016, when Mars was 50 million miles from Earth. The Hubble image reveals details as small as 20 to 30 miles across.

The large, dark region at far right is Syrtis Major Planitia, one of the first features identified on the surface of the planet by seventeenth century observers. Christiaan Huygens used this feature to measure the rotation rate of Mars. (A Martian day is about 24 hours and 37 minutes.) Today we know that Syrtis Major is an ancient, inactive shield volcano. Late-afternoon clouds surround its summit in this view.

A large oval feature to the south of Syrtis Major is the bright Hellas Planitia basin. About 1,100 miles across and nearly five miles deep, it was formed about 3.5 billion years ago by an asteroid impact.

The orange area in the center of the image is Arabia Terra, a vast upland region in northern Mars that covers about 2,800 miles. The landscape is densely cratered and heavily eroded, indicating that it could be among the oldest terrains on the planet. Dried river canyons (too small to be seen here) wind through the region and empty into the large northern lowlands.

South of Arabia Terra, running east to west along the equator, are the long dark features known as Sinus Sabaeus (to the east) and Sinus Meridiani (to the west). These darker regions are covered by dark bedrock and fine-grained sand deposits ground down from ancient lava flows and other volcanic features. These sand grains are coarser and less reflective than the fine dust that gives the brighter regions of Mars their ruddy appearance. Early Mars watchers first mapped these regions.

An extended blanket of clouds can be seen over the southern polar cap. The icy northern polar cap has receded to a comparatively small size because it is now late summer in the northern hemisphere. Hubble photographed a wispy, afternoon, lateral cloud extending for at least 1,000 miles at mid-northern latitudes. Early morning clouds and haze extend along the western limb.

This hemisphere of Mars contains landing sites for several NASA Mars surface robotic missions, including Viking 1 (1976), Mars Pathfinder (1997), and the still-operating Opportunity Mars rover. The landing sites of the Spirit and Curiosity Mars rovers are on the other side of the planet.

This observation was made just a few days before Mars opposition on May 22, when the sun and Mars will be on exact opposite sides of Earth, and when Mars will be at a distance of 47.4 million miles from Earth. On May 30, Mars will be the closest it has been to Earth in 11 years, at a distance of 46.8 million miles. Mars is especially photogenic during opposition because it can be seen fully illuminated by the sun as viewed from Earth.

The biennial close approaches between Mars and Earth are not all the same. Mars' orbit around the sun is markedly elliptical; the close approaches to Earth can range from 35 million miles to 63 million miles.

They occur because about every two years Earth's orbit catches up to Mars' orbit, aligning the sun, Earth, and Mars in a straight line, so that Mars and the sun are on "opposing" sides of Earth. This phenomenon is a result of the difference in orbital periods between Earth's orbit and Mars' orbit. While Earth takes the familiar 365 days to travel once around the sun, Mars takes 687 Earth days to make its trip around our star. As a result, Earth makes almost two full orbits in the time it takes Mars to make just one, resulting in the occurrence of Martian oppositions about every 26 months.

Image Credit: NASA, ESA, the Hubble Heritage Team (STScI/AURA), J. Bell (ASU), and M. Wolff
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Millions of Galaxies

Millions of Galaxies

Millions of galaxies populate the patch of sky known as the COSMOS field, short for Cosmic Evolution Survey, a portion of which is shown here. Even the smallest dots in this image are galaxies, some up to 12 billion light-years away. The square region in the center of bright objects is where the telescope was blinded by bright light. However, even these brightest objects in the field are more than ten thousand times fainter than what you can see with the naked eye.

The picture is a combination of infrared data from Spitzer (red) and visible-light data (blue and green) from Japan's Subaru telescope atop Mauna Kea in Hawaii. These data were taken as part of the SPLASH (Spitzer large area survey with Hyper-Suprime-Cam) project.

Image Credit: NASA/JPL-Caltech
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Volcán de Colima Eruption

Volcán de Colima Eruption

Colima, Mexico
October 2015

Image Credit & Copyright: Notimex

Comparison of the Sun to UY Scuti

Comparison of the Sun to UY Scuti

The Sun

The Sun is the star at the center of the Solar System and is by far the most important source of energy for life on Earth. It is a nearly perfect spherical ball of hot plasma, with internal convective motion that generates a magnetic field via a dynamo process. Its diameter is about 109 times that of Earth, and it has a mass about 330,000 times that of Earth, accounting for about 99.86% of the total mass of the Solar System. About three quarters of the Sun's mass consists of hydrogen; the rest is mostly helium, with much smaller quantities of heavier elements, including oxygen, carbon, neon and iron.

The Sun is a G-type main-sequence star (G2V) based on spectral class and it is informally referred to as a yellow dwarf. It formed approximately 4.6 billion years ago from the gravitational collapse of matter within a region of a large molecular cloud. Most of this matter gathered in the center, whereas the rest flattened into an orbiting disk that became the Solar System. The central mass became increasingly hot and dense, eventually initiating nuclear fusion in its core. It is thought that almost all stars form by this process.

The Sun is roughly middle aged and has not changed dramatically for over four billion years, and will remain fairly stable for more than another five billion years. However, after hydrogen fusion in its core has stopped, the Sun will undergo severe changes and become a red giant. It is calculated that the Sun will become sufficiently large to engulf the current orbits of Mercury, Venus, and possibly Earth.

The enormous effect of the Sun on Earth has been recognized since prehistoric times, and the Sun has been regarded by some cultures as a deity. Earth's movement around the Sun is the basis of the solar calendar, which is the predominant calendar in use today.

UY Scuti

UY Scuti is a bright red supergiant and pulsating variable star in the constellation Scutum. It is a leading candidate for being the largest known star by radius and is also one of the most luminous of its kind. It has an estimated average median radius of 1,708 solar radii, or a diameter of 2.4 billion km (1.5 billion mi; 15.9 AU); thus a volume 5 billion times that of the Sun. It is approximately 2.9 kiloparsecs (9,500 light years) from Earth. If placed at the center of the Solar System, its photosphere would engulf the orbit of Jupiter, although the radius is not known for certain and may be larger than the orbit of Saturn.

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May 19, 2016

The R Coronae Australis region

R Coronae Australis

The nearby star-forming region around the star R Coronae Australis imaged by the Wide Field Imager (WFI) on the MPG/ESO 2.2-metre telescope at ESO’s La Silla Observatory in Chile. This picture, which covers a field of 33.7 x 31.9 arcminutes (about the diameter of the full Moon), is a combination of twelve CCD frames, 67 megapixels each, taken through B, V and R filters, with four exposures of five minutes each.

Image Credit: ESO
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ALMA beneath the stars

ALMA Telescope

Several of the 12-metre antennas that comprise a part of the Atacama Large Millimeter/submillimeter Array (ALMA) peer at targets in the night sky. The recognisable glow of the Milky Way cuts across the image amongst a sea of stars.

Image Credit: A. Duro/ESO
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VST image of the Fornax Galaxy Cluster

Fornax Galaxy Cluster

The Fornax Galaxy Cluster is one of the closest of such groupings beyond our Local Group of galaxies. This new VLT Survey Telescope image shows the central part of the cluster in great detail. At the lower-right is the elegant barred-spiral galaxy NGC 1365 and to the left the big elliptical NGC 1399.

Image Credit: ESO, Aniello Grado and Luca Limatola
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May 18, 2016

Spitzer and Hubble View of the Sombrero Galaxy

Sombrero Galaxy

NASA's Spitzer and Hubble Space Telescopes joined forces to create this striking composite image of one of the most popular sights in the universe. Messier 104 is commonly known as the Sombrero galaxy because in visible light, it resembles the broad-brimmed Mexican hat. However, in Spitzer's striking infrared view, the galaxy looks more like a "bull's eye."

In Hubble's visible light image, only the near rim of dust can be clearly seen in silhouette. Recent observations using Spitzer's infrared array camera uncovered the bright, smooth ring of dust circling the galaxy, seen in red. Spitzer's infrared view of the starlight, piercing through the obscuring dust, is easily seen, along with the bulge of stars and an otherwise hidden disk of stars within the dust ring.

Spitzer's full view shows the disk is warped, which is often the result of a gravitational encounter with another galaxy, and clumpy areas spotted in the far edges of the ring indicate young star-forming regions.

The Sombrero galaxy is located some 28 million light-years away. Viewed from Earth, it is just six degrees south of its equatorial plane. Spitzer detected infrared emission not only from the ring, but from the center of the galaxy too, where there is a huge black hole, believed to be a billion times more massive than our Sun. This magnificent galaxy has a diameter that is nearly one-fifth the diameter of the full Moon.

Image Credit: NASA/JPL-Caltech/R. Kennicutt (University of Arizona) and the SINGS Team
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Karymsky Volcano Eruption

Karymsky Volcano Eruption

Kamchatka Peninsula, Russia

Image Credit: Alexander Belousov

Artist's Impression of the most distant quasar

the most distant quasar ULAS J1120+0641

This artist’s impression shows how ULAS J1120+0641, a very distant quasar powered by a black hole with a mass two billion times that of the Sun, may have looked. This quasar is the most distant yet found and is seen as it was just 770 million years after the Big Bang. This object is by far the brightest object yet discovered in the early Universe.

Image Credit: ESO/M. Kornmesser
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May 17, 2016

The Milky Way seen from Malibu Sea Cave

The Milky Way seen from Malibu Sea Cave

Leo Carrillo State Park, Malibu, California, USA

Image Credit & Copyright: Jack Fusco

The rich celestial landscape around the aging double star IRAS 08544-4431

IRAS 08544-4431

This colourful image shows the rich celestial landscape in the constellation of Vela (The Sails) around the aging double star IRAS 08544-4431, which appears as the moderately bright star at the exact centre of the picture. The image was created from images forming part of the Digitized Sky Survey 2. It also includes several other interesting unrelated objects. At the bottom the Pencil Nebula (NGC 2736) is visible, along with the orange clouds of star formation regions and the blue filaments of part of the Vela Supernova Remnant.

Image Credit: ESO/Digitized Sky Survey 2, Davide De Martin
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Milky Way Nuclear Star Cluster

Milky Way Nuclear Star Cluster

Peering deep into the heart of our Milky Way galaxy, NASA's Hubble Space Telescope reveals a rich tapestry of more than half a million stars. Except for a few blue, foreground stars, the stars are part of the Milky Way's nuclear star cluster, the most massive and densest star cluster in our galaxy. So packed with stars, it is equivalent to having a million Suns crammed into the volume of space between us and our closest stellar neighbor, Alpha Centauri, 4.3 light-years away. At the very hub of our galaxy, this star cluster surrounds the Milky Way's central supermassive black hole, which is about 4 million times the mass of our Sun.

Astronomers used Hubble's infrared vision to pierce through the dust in the disk of our galaxy that obscures the star cluster. In this image, scientists translated the infrared light, which is invisible to human eyes, into colors our eyes can see. The red stars are either embedded or shrouded by intervening dust. Extremely dense clouds of gas and dust are seen in silhouette, appearing dark against the bright background stars. These clouds are so thick that even Hubble's infrared capability could not penetrate them.

Hubble's sharp vision allowed astronomers to measure the movements of the stars over four years. Using this information, scientists were able to infer important properties such as the mass and structure of the nuclear star cluster. The motion of the stars may also offer a glimpse into how the star cluster was formed — whether it was built up over time by globular star clusters that happen to fall into the galaxy's center, or from gas spiraling in from the Milky Way's disk to form stars at the core.

This picture, spanning 50 light-years across, is a mosaic stitched from nine separate images from Hubble's Wide Field Camera 3. The center of the Milky Way is located 27,000 light-years away. The "snowstorm" of stars in the image is just the tip of the iceberg: Astronomers estimate that about 10 million stars in this cluster are too faint to be captured in this image.

Image Credit: NASA, ESA, and the Hubble Heritage Team (STScI/AURA), T. Do and A. Ghez (UCLA), and V. Bajaj (STScI)
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May 16, 2016

The Whirlpool Galaxy

Whirlpool Galaxy

The Whirlpool galaxy, M51, has been one of the most photogenic galaxies in amateur and professional astronomy. Easily photographed and viewed by smaller telescopes, this celestial beauty is studied extensively in a range of wavelengths by large ground- and space-based observatories. This Hubble composite image shows visible starlight as well as light from the emission of glowing hydrogen, which is associated with the most luminous young stars in the spiral arms.

Image Credit: NASA/ESA and The Hubble Heritage Team STScI/AURA)
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Aurora over Iceland

Aurora over Iceland

Selfoss City, Iceland
August 2015

Image Credit & Copyright: Davide Necchi

The dusty ring around the aging double star IRAS 08544-4431

double star IRAS 08544-4431

The Very Large Telescope Interferometer at ESO’s Paranal Observatory in Chile has obtained the sharpest view ever of the dusty disc around the close pair of aging stars IRAS 08544-4431. For the first time such discs can be compared to the discs around young stars — and they look surprisingly similar. It is even possible that a disc appearing at the end of a star’s life might also create a second generation of planets.

This view shows the VLTI reconstructed image, with the brighter central star removed. A fainter glow from the secondary star is visible, which came as a surprise to the observers.

Image Credit: ESO
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May 15, 2016

Elephant's Trunk Nebula

Elephant's Trunk Nebula

The Elephant's Trunk nebula is a concentration of interstellar gas and dust within the much larger ionized gas region IC 1396 located in the constellation Cepheus about 2,400 light years away from Earth. The piece of the nebula shown here is the dark, dense globule IC 1396A; it is commonly called the Elephant's Trunk nebula because of its appearance at visible light wavelengths, where there is a dark patch with a bright, sinuous rim. The bright rim is the surface of the dense cloud that is being illuminated and ionized by a very bright, massive star (HD 206267) that is just to the west of IC 1396A. (In the Figure above, the massive star is just to the left of the edge of the image.) The entire IC 1396 region is ionized by the massive star, except for dense globules that can protect themselves from the star's harsh ultraviolet rays.

The Elephant's Trunk nebula is now thought to be a site of star formation, containing several very young (less than 100,000 yr) stars that were discovered in infrared images in 2003. Two older (but still young, a couple of million years, by the standards of stars, which live for billions of years) stars are present in a small, circular cavity in the head of the globule. Winds from these young stars may have emptied the cavity.

The combined action of the light from the massive star ionizing and compressing the rim of the cloud, and the wind from the young stars shifting gas from the center outward lead to very high compression in the Elephant's Trunk nebula. This pressure has triggered the current generation of protostars.

Image Credit & Copyright: J.C. Canonne, P. Bernhard, D. Chaplain & L. Bourgon
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Artist's Impression of the Surface of Neptune’s Moon Triton

Surface of Neptune’s Moon Triton

Artist’s impression of how Triton, Neptune’s largest moon, might look from high above its surface. The distant Sun appears at the upper-left and the blue crescent of Neptune right of centre. Using the CRIRES instrument on ESO’s Very Large Telescope, a team of astronomers has been able to see that the summer is in full swing in Triton’s southern hemisphere.

Image Credit: ESO/L. Calçada
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The Milky Way Galaxy and Total Lunar Eclipse

The Milky Way Galaxy and Total Lunar Eclipse

A total lunar eclipse took place between September 27 and 28, 2015. It was seen Sunday evening, September 27, in the Americas; while in Europe, Africa, and the Middle East, it was seen in the early hours of Monday morning, September 28. It was the latter of two total lunar eclipses in 2015, and the final in a tetrad (four total lunar eclipses in series). Other eclipses in the tetrad are those of April 15, 2014, October 8, 2014, and April 4, 2015.

The Moon appeared larger than normal because the Moon was just 59 minutes past its closest approach to Earth in 2015 at mid-eclipse, sometimes called a supermoon. The Moon's apparent diameter was larger than 34' viewed straight overhead, just off the coast of northeast Brazil.

The total lunar eclipse was darker than expected, possibly due to eruptions of Calbuco volcano.

Image Credit & Copyright: Amit Kamble
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