Whether The Galaxy Grow ...?

Galaxy clusters are the largest collapsed objects in the Universe and are ideal for studying the properties of dark energy, the mysterious form of repulsive gravity that is driving the accelerated expansion of the Universe. The growth of these structures was initially driven only by the attractive force of gravity, but then later there was competition with the repulsive force of dark energy.

Understanding the nature of dark energy is one of the biggest problems in science. Possibilities include the cosmological constant, equivalent to the energy of empty space, a modification in general relativity on the largest scales, or a more general physical field. The results are remarkably consistent with those from previous results that measure the expansion of the Universe using distance measurements, revealing that general relativity works as expected on large scales. 

And Today 

Herschel Mission Finds Galactic Growth Slow and Steady

The Herschel Infrared Space Observatory discovered that galaxies do not always need to collide with each other to drive vigorous star birth. The finding overturns a long-held assumption and paints a more stately picture of how galaxies evolve. The new results are based on Herschel's observations of two patches of sky, each about one-third the size of the full moon.

These observations are unique because Herschel can obtain data at a wide range of infrared light and reveal a more complete picture of star birth than ever seen before.

Herschel is a European Space Agency cornerstone mission, with science instruments provided by consortia of European institutes and with important participation by NASA JPL, which contributed mission-enabling technology for two of Herschel's three science instruments.

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Our Planet and Sun

What causes the sun to vary? 

We live in the extended atmosphere of a magnetic variable star that drives our solar system and sustains life on Earth. Our Sun varies in every way we can observe it. The Sun gives off light in the infrared, visible, ultraviolet, and at x-ray energies, and it gives off magnetic field, bulk plasma (the solar wind) and energetic particles moving up to nearly the speed of light, and all of these emissions vary. These variations occur on timescales from milliseconds to billions of years. Most of these variations are related to the solar magnetic field, which is caused by the moving plasma inside the rotating Sun, which make a dynamo. 

How do the Earth and Heliosphere respond?

Our planet is immersed in this seemingly invisible yet exotic and inherently dangerous environment. Above the protective cocoon of Earth’s lower atmosphere is a plasma soup composed of electrified and magnetized matter entwined with penetrating radiation and energetic particles. The Earth’s magnetic field interacts with the Sun’s outer atmosphere to create this extraordinary environment.

Our Sun’s explosive energy output forms an immense, complex magnetic fields structure. Hugely inflated by the solar wind, this colossal bubble of magnetism known as the heliosphere stretches far beyond the orbit of Pluto, from where it controls the entry of cosmic rays into the solar system. On its way through the Milky Way this extended atmosphere of the Sun affects all planetary bodies in the solar system. It is itself influenced by slowly changing interstellar conditions that in turn can affect Earth’s habitability. In fact, the Sun’s extended atmosphere drives some of the greatest changes in the near-Earth space environment affecting our magnetosphere, atmosphere, ionosphere, and potentially our climate.

What are the impacts on humanity?

Modern society depends heavily on a variety of technologies that are susceptible to the extremes of space weather — severe disturbances of the upper atmosphere and of the near-Earth space environment that are driven by the magnetic activity of the Sun. Strong electrical currents driven in the Earth’s surface during auroral events can disrupt and damage modern electric power grids and may contribute to the corrosion of oil and gas pipelines. Changes in the ionosphere during geomagnetic storms driven by magnetic activity of the Sun interfere with high-frequency radio communications and GPS navigation. During polar cap absorption events caused by solar protons, radio communications can be severely compromised for commercial airliners on transpolar crossing routes. Exposure of spacecraft to energetic particles during solar energetic particle events and radiation belt enhancements can cause temporary operational anomalies, damage critical electronics, degrade solar arrays, and blind optical systems such as imagers and star trackers used on commercial and government satellites.

Harsh conditions in the space environment also pose significant risks for the journey of exploration. Although space is a near-vacuum, the very-thinly-spread particles and fields are like an ocean that can affect the spacecraft and astronauts that travel through it. Like seafaring voyagers, space explorers must be constantly aware of the current space weather and be prepared to handle the most extreme conditions that might be encountered.

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The Andromeda Galaxy

Andromeda is the nearest major galaxy to our own Milky Way Galaxy. Our Galaxy is thought to look much like Andromeda. Together these two galaxies dominate the Local Group of galaxies. The diffuse light from Andromeda is caused by the hundreds of billions of stars that compose it. The several distinct stars that surround Andromeda's image are actually stars in our Galaxy that are well in front of the background object. Andromeda is frequently referred to as M31 since it is the 31st object on Messier's list of diffuse sky objects. M31 is so distant it takes about two million years for light to reach us from there. Much about M31 remains unknown, including why the center contains two nuclei.

The immense Andromeda galaxy, also known as Messier 31 or simply M31, is captured in full in this new image from NASA's Wide-field Infrared Survey Explorer, or WISE. The mosaic covers an area equivalent to more than 100 full moons, or five degrees across the sky. WISE used all four of its infrared detectors to capture this picture (3.4- and 4.6-micron light is colored blue; 12-micron light is green; and 22-micron light is red). Blue highlights mature stars, while yellow and red show dust heated by newborn, massive stars.

Andromeda is the closest large galaxy to our Milky Way galaxy, and is located 2.5 million light-years from our sun. It is close enough for telescopes to spy the details of its ringed arms of new stars and hazy blue backbone of older stars. Also seen in the mosaic are two satellite galaxies, known as M32, located just a bit above Andromeda to the left of center, and the fuzzy blue M110, located below the center of the great spiral arms. These satellites are the largest of several that are gravitationally bound to Andromeda.

The Andromeda galaxy is larger than our Milky Way and contains more stars, but the Milky Way is thought to perhaps have more mass due to its larger proportion of a mysterious substance called dark matter. Both galaxies belong to our so-called Local Group, a collection of more than 50 galaxies, most of which are tiny dwarf systems. In its quest to map the whole sky, WISE will capture the entire Local Group.

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A Green Comet "going green"

We hear a lot about "going green" these days. The latest to join in the trend is comet Lulin, which is making an appearance in the nighttime sky this month. Don Yeomans of JPL, manager for NASA's Near-Earth Object Program Office, answers a few questions about this odd comet.

Q: Why is comet Lulin green?
A: The ices in comet Lulin vaporize into gases when its nucleus gets close enough to the sun. These gases appear greenish due to the emission of carbon (C2) and the lack of a significant yellowish dust tail that sometimes dominates the color of an active comet.

Q: What other unusual characteristics does the comet have?
A: Comet Lulin is moving nearly in the same orbital plane around the sun as do the planets, but in the opposite (retrograde) direction. It is probably the first time this comet has entered the inner solar system, so some of its original volatile ices in its nucleus may still be present, and should be identifiable during observations.

Q: Will we be able to see comet Lulin and its greenish color? If so, where, when and how?
A: The comet should be observable in dark skies with binoculars. The best time to observe might be near its closest approach to Earth (about 38 million miles) on Tues., Feb. 24, when the comet appears just below the planet Saturn in the constellation of Leo (high in the southeast in late evening for observers in mid- northern latitudes, for example, in the United States and Europe.

Q: Will NASA astronomers be tracking the comet?
A: A small army of amateur and professional astronomers will certainly take advantage of this young comet using various telescopes and in many different wavelengths. It is not that often that a relatively bright, young comet is seen in the inner solar system, and astronomers will take advantage of this opportunity to identify some of the gases that make up its greenish atmosphere - and infer what exotic ices make up its unseen nucleus.

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Sparkle

This Hubble Space Telescope image of galaxy NGC 1275 reveals the fine, thread-like filamentary structures in the gas surrounding the galaxy. The red filaments are composed of cool gas being suspended by a magnetic field, and are surrounded by the 100-million-degree Fahrenheit hot gas in the center of the Perseus galaxy cluster.

The filaments are dramatic markers of the feedback process through which energy is transferred from the central massive black hole to the surrounding gas. The filaments originate when cool gas is transported from the center of the galaxy by radio bubbles that rise in the hot interstellar gas.

At a distance of 230 million light-years, NGC 1275 is one of the closest giant elliptical galaxies and lies at the center of the Perseus cluster of galaxies.

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Fornax Galaxy Cluster

This image of a dense cluster of galaxies was captured by NASA's Wide-field Infrared Survey Explorer, or WISE. The cluster, called Fornax because of its location in a constellation of the same name, is 60 million light-years from Earth, and is one of the closest galaxy clusters to the Milky Way. Clusters are large families of galaxies that are gravitationally bound together, containing enough matter to pull even distant galaxies toward them.


WISE's large field of view and multi-wavelength infrared sight allowed it to form this complete view of the cluster, containing dozens of bright galaxies and hundreds of smaller ones. Old stars show up at the shorter infrared wavelengths, color coded blue. Dust heated by new generations of stars lights up at longer infrared wavelengths, colored red here.


The center of the cluster is dominated by the galaxy known as NGC 1399, a large spheroidal galaxy whose light is almost exclusively from old stars and thus appears blue.   The most spectacular member of Fornax is the galaxy known as NGC 1365, a giant barred spiral galaxy, located in the lower right of the mosaic.  Against a backdrop of blue light from old stars, the dusty spiral arms in NGC 1365 stand out. The arms contain younger stars that are heating up their dust-enshrouded birth clouds, causing them to glow at longer infrared wavelengths.  This galaxy is one of only a few in the Fornax cluster where prolific star formation can be seen. WISE will search the sky out to distances of 10 billion light-years looking for the most luminous cousins of NGC 1365.


In this image, 3.4- and 4.6-micron light is colored blue; 12-micron light is green; and 22-micron light is red.

Image credit: NASA/JPL-Caltech/UCLA

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