Tag Archives: Astronomy

Universe in a bubble

Maybe we don’t have to speculate about what life is like inside a bubble. It might be the only cosmic reality we know.
By J Richard Gott – The explanation for the accelerating cosmic expansion, surprising as it was at first, was readily available from the theoretical toolbox of physicists. It traced back to an idea from Albert Einstein, called the cosmological constant. Einstein invented it in 1917, as part of a failed attempt to produce a static Universe based on his general theory of relativity. At that time, the data seemed to support such a model.

In 1922, the Russian mathematician Alexander Friedmann showed that relativity in its simplest form, without the cosmological constant, seemed to imply an expanding or contracting Universe. When Hubble’s observations showed conclusively that the Universe was expanding, Einstein abandoned the cosmological constant, but the possibility that it existed never went away.

Then the Belgian physicist Georges Lemaître showed that the cosmological constant could be interpreted in a physical way as the vacuum of empty space possessing a finite energy density accompanied by a negative pressure. That idea might sound rather bizarre at first. We are accustomed, after all, to thinking that the vacuum of empty space should have a zero energy density, since it has no matter in it. But suppose empty space had a finite but small energy density – there’s no inherent reason why such a thing could not be possible.

Negative pressure has a repulsive gravitational effect, but at the same time the energy itself has an attractive gravitational effect, since energy is equivalent to mass. (This is the relationship described by E=mc2, another implication of special relativity.) Operating in three directions – left-right, front-back, and up-down – the negative pressure creates repulsive effects three times as potent as the attractive effects of the vacuum energy, making the overall effect repulsive. We call this vacuum energy dark energy, because it produces no light. Dark energy is the widely accepted explanation for why the expansion rate of the Universe is speeding up.

Distant galaxies will flee from us because of the stretching of space between us and them. After a sufficient number of doublings, the space between them and us will be stretching so fast that their light will no longer be able to cross this ever-widening gap to reach us. Distant galaxies will fade from view and we will find ourselves seemingly alone in the visible Universe. more>

Old astronomic riddle soon to be solved

By Olivia Poisson – Almost 100 years ago, astronomers discovered that the spectrum of star light arrived on earth with dark gaps, so-called interstellar bands.

Ever since, researchers have been trying to find out which type of matter in space absorbs the light and is responsible for these “diffuse interstellar bands” (DIB) of which over 400 are known today.

The research team led by Prof. John P. Maier from the Dept. of Chemistry at the Univ. of Basel has been studying the electronic absorption of the ionized Buckminsterfullerene since 1993. In fact, the spectrum measured in the lab did show absorption features at two wavelengths that were near two DIB that had been discovered by astronomers the following year. more> http://tinyurl.com/qjq2bjq

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Hubble Views a Galaxy on Edge

NASA – This NASA/ESA Hubble Space Telescope image shows an edge-on view of the spiral galaxy NGC 5023. Due to its orientation we cannot appreciate its spiral arms, but we can admire the elegant profile of its disk. The galaxy lies over 30 million light-years away from us.

NGC 5023 is part of the M51 group of galaxies. The brightest galaxy in this group is Messier 51, the Whirlpool Galaxy, which has been captured by Hubble many times. NGC 5023 is less fond of the limelight and seems rather unsociable in comparison — it is relatively isolated from the other galaxies in the group.

Astronomers are particularly interested in the vertical structure of disks like these. By analyzing the structure above and below the central plane of the galaxy they can make progress in understanding galaxy evolution. Astronomers are able to analyze the distribution of different types of stars within the galaxy and their properties, in particular how well evolved they are on the Hertzsprung–Russell Diagram — a scatter graph of stars that shows their evolution.

NGC 5023 is one of six edge-on spiral galaxies observed as part of a study using Hubble’s Advanced Camera for Surveys. They study this vertical distribution and find a trend which suggests that heating of the disc plays an important role in producing the stars seen away from the plane of the galaxy.

In fact, NGC 5023 is pretty popular when it comes to astronomers, despite its unsociable behavior. The galaxy is also one of 14 disk galaxies that are part of the GHOSTS survey — a survey which uses Hubble data to study galaxy halos, outer disks and star clusters. It is the largest study to date of star populations in the outskirts of disk galaxies.

The incredible sharp sight of Hubble has allowed scientist to count more than 30,000 individual bright stars in this image. This is only a small fraction of the several billion stars that this galaxy contains, but the others are too faint to detect individually even with Hubble.

European Space Agency

Credit: ESA/NASA

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Chandra Celebrates the International Year of Light

NASA – The year of 2015 has been declared the International Year of Light (IYL) by the United Nations. Organizations, institutions, and individuals involved in the science and applications of light will be joining together for this yearlong celebration to help spread the word about the wonders of light.

NASA’s Chandra X-ray Observatory explores the universe in X-rays, a high-energy form of light.  By studying X-ray data and comparing them with observations in other types of light, scientists can develop a better understanding of objects likes stars and galaxies that generate temperatures of millions of degrees and produce X-rays.

To recognize the start of IYL, the Chandra X-ray Center is releasing a set of images that combine data from telescopes tuned to different wavelengths of light. From a distant galaxy to the relatively nearby debris field of an exploded star, these images demonstrate the myriad ways that information about the universe is communicated to us through light.

In this image, an expanding shell of debris called SNR 0519-69.0 is left behind after a massive star exploded in the Large Magellanic Cloud, a satellite galaxy to the Milky Way. Multimillion degree gas is seen in X-rays from Chandra, in blue. The outer edge of the explosion (red) and stars in the field of view are seen in visible light from the Hubble Space Telescope.

> More: Chandra Celebrates the International Year of Light

Image Credit: NASA/CXC/SAO

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Hubble’s High-Definition Panoramic View of the Andromeda Galaxy

NASA – The largest NASA Hubble Space Telescope image ever assembled, this sweeping bird’s-eye view of a portion of the Andromeda galaxy (M31) is the sharpest large composite image ever taken of our galactic next-door neighbor. Though the galaxy is over 2 million light-years away, the Hubble Space Telescope is powerful enough to resolve individual stars in a 61,000-light-year-long stretch of the galaxy’s pancake-shaped disk. It’s like photographing a beach and resolving individual grains of sand. And there are lots of stars in this sweeping view — over 100 million, with some of them in thousands of star clusters seen embedded in the disk.

This ambitious photographic cartography of the Andromeda galaxy represents a new benchmark for precision studies of large spiral galaxies that dominate the universe’s population of over 100 billion galaxies. Never before have astronomers been able to see individual stars inside an external spiral galaxy over such a large contiguous area. Most of the stars in the universe live inside such majestic star cities, and this is the first data that reveal populations of stars in context to their home galaxy.

The Hubble Space Telescope is a project of international cooperation between NASA and the European Space Agency. NASA’s Goddard Space Flight Center in Greenbelt, Maryland, manages the telescope. The Space Telescope Science Institute (STScI) in Baltimore conducts Hubble science operations. STScI is operated for NASA by the Association of Universities for Research in Astronomy, Inc., in Washington.

> More: Hubble’s High-Definition Panoramic View of the Andromeda Galaxy

Image Credit: NASA, ESA, J. Dalcanton, B.F. Williams, and L.C. Johnson (U. of Washington), the Panchromatic Hubble Andromeda Treasury (PHAT) team, and R. Gendler

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Swift Gamma-Ray Burst Mission Marks Ten Years of Discovery

NASA – On Nov. 20, 2004, NASA’s Swift spacecraft lifted off aboard a Boeing Delta II rocket from Cape Canaveral Air Force Station, Fla., beginning its mission to study gamma-ray bursts and identify their origins. Gamma-ray bursts are the most luminous explosions in the cosmos. Most are thought to be triggered when the core of a massive star runs out of nuclear fuel, collapses under its own weight, and forms a black hole. The black hole then drives jets of particles that drill all the way through the collapsing star and erupt into space at nearly the speed of light.

Astronomers at NASA and Pennsylvania State University used Swift to create the most detailed ultraviolet light surveys ever of the Large and Small Magellanic Clouds, the two closest major galaxies. Nearly a million ultraviolet sources appear in this mosaic of the Large Magellanic Cloud, which was assembled from 2,200 images taken by Swift’s Ultraviolet/Optical Telescope (UVOT) and released on June 3, 2013.

The 160-megapixel image required a cumulative exposure of 5.4 days. The image includes light from 1,600 to 3,300 angstroms — UV wavelengths largely blocked by Earth’s atmosphere — and has an angular resolution of 2.5 arcseconds at full size. The Large Magellanic Cloud is about 14,000 light-years across.

Viewing in the ultraviolet allows astronomers to suppress the light of normal stars like the sun, which are not very bright at such higher energies, and provides a clearer picture of the hottest stars and star-formation regions. No telescope other than UVOT can produce such high-resolution wide-field multicolor surveys in the ultraviolet.

Pennsylvania State University manages the Swift Mission Operations Center, which controls Swift’s science and flight operations. Goddard manages Swift, which was launched in November 2004. The satellite is operated in collaboration with Penn State, the Los Alamos National Laboratory in New Mexico and Orbital Sciences Corp. in Dulles, Va. International collaborators are in the United Kingdom and Italy, and the mission includes contributions from Germany and Japan.

Image Credit: NASA/Swift/S. Immler (Goddard) and M. Siegel (Penn State)

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MSH 11-62 Supernova Remnant

NASA – A long observation with Chandra of the supernova remnant MSH 11-62 reveals an irregular shell of hot gas, shown in red, surrounding an extended nebula of high energy X-rays, shown in blue.

Even though scientists have yet to detect any pulsations from the central object within MSH 11-62, the structure around it has many of the same characteristics as other pulsar wind nebulas. The reverse shock and other, secondary shocks within MSH 11-62 appear to have begun to crush the pulsar wind nebula, possibly contributing to its elongated shape. (Note: the orientation of this image has been rotated by 24 degrees so that north is pointed to the upper left.)

Image credit:  NASA/CXC/SAO/P. Slane et al.

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Fifteen Years of NASA’s Chandra X-ray Observatory

NASA – This Chandra X-ray Observatory image of the Hydra A galaxy cluster was taken on Oct. 30, 1999, with the Advanced CCD Imaging Spectrometer (ACIS) in an observation that lasted about six hours. Hydra A is a galaxy cluster that is 840 million light years from Earth. The cluster gets its name from the strong radio source, Hydra A, that originates in a galaxy near the center of the cluster. Optical observations show a few hundred galaxies in the cluster. Chandra X-ray observations reveal a large cloud of hot gas that extends throughout the cluster. The gas cloud is several million light years across and has a temperature of about 40 million degrees in the outer parts decreasing to about 35 million degrees in the inner region.

NASA’s Chandra X-ray Observatory was launched into space fifteen years ago aboard the Space Shuttle Columbia. Since its deployment on July 23, 1999, Chandra has helped revolutionize our understanding of the universe through its unrivaled X-ray vision. Chandra, one of NASA’s current “Great Observatories,” along with the Hubble Space Telescope and Spitzer Space Telescope, is specially designed to detect X-ray emission from hot and energetic regions of the universe.

Image Credit: NASA/CXC/SAO

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Illusions in the Cosmic Clouds

NASA – Pareidolia is the psychological phenomenon where people see recognizable shapes in clouds, rock formations, or otherwise unrelated objects or data. There are many examples of this phenomenon on Earth and in space.

When an image from NASA’s Chandra X-ray Observatory of PSR B1509-58 — a spinning neutron star surrounded by a cloud of energetic particles –was released in 2009, it quickly gained attention because many saw a hand-like structure in the X-ray emission.

In a new image of the system, X-rays from Chandra in gold are seen along with infrared data from NASA’s Wide-field Infrared Survey Explorer (WISE) telescope in red, green and blue. Pareidolia may strike again as some people report seeing a shape of a face in WISE’s infrared data. What do you see?

NASA’s Nuclear Spectroscopic Telescope Array, or NuSTAR, also took a picture of the neutron star nebula in 2014, using higher-energy X-rays than Chandra.

PSR B1509-58 is about 17,000 light-years from Earth.

JPL, a division of the California Institute of Technology in Pasadena, manages the WISE mission for NASA. NASA’s Marshall Space Flight Center in Huntsville, Alabama, manages the Chandra program for. The Smithsonian Astrophysical Observatory in Cambridge, Massachusetts, controls Chandra’s science and flight operations.

Image Credit: X-ray: NASA/CXC/SAO; Infrared: NASA/JPL-Caltech

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Hubble Sees Turquoise-Tinted Plumes in Large Magellanic Cloud

NASA – The brightly glowing plumes seen in this image are reminiscent of an underwater scene, with turquoise-tinted currents and nebulous strands reaching out into the surroundings.

However, this is no ocean. This image actually shows part of the Large Magellanic Cloud (LMC), a small nearby galaxy that orbits our galaxy, the Milky Way, and appears as a blurred blob in our skies. The NASA/European Space Agency (ESA) Hubble Space Telescope has peeked many times into this galaxy, releasing stunning images of the whirling clouds of gas and sparkling stars (opo9944a, heic1301, potw1408a).

This image shows part of the Tarantula Nebula’s outskirts. This famously beautiful nebula, located within the LMC, is a frequent target for Hubble (heic1206, heic1402).

In most images of the LMC the color is completely different to that seen here. This is because, in this new image, a different set of filters was used. The customary R filter, which selects the red light, was replaced by a filter letting through the near-infrared light. In traditional images, the hydrogen gas appears pink because it shines most brightly in the red. Here however, other less prominent emission lines dominate in the blue and green filters.

This data is part of the Archival Pure Parallel Project (APPP), a project that gathered together and processed over 1,000 images taken using Hubble’s Wide Field Planetary Camera 2, obtained in parallel with other Hubble instruments. Much of the data in the project could be used to study a wide range of astronomical topics, including gravitational lensing and cosmic shear, exploring distant star-forming galaxies, supplementing observations in other wavelength ranges with optical data, and examining star populations from stellar heavyweights all the way down to solar-mass stars.

Image Credit: ESA/Hubble & NASA: acknowledgement: Josh Barrington
Text: European Space Agency