Hundreds of galaxies hidden behind Milky Way discovered

(Representative image) Scientists have discovered hundreds of galaxies just 250 million light years away from Earth which had been hidden from view until now by our Milky Way galaxy.

MELBOURNE: Scientists have discovered hundreds of galaxies just 250 million light years away from Earth which had been hidden from view until now by our Milky Way galaxy. 

The discovery may help to explain the mysterious gravitational anomaly dubbed the Great Attractor, that appears to be drawing the Milky Way and hundreds of thousands of other galaxies towards it with a gravitational force equivalent to a million billion Suns. 

Using Commonwealth Scientific and Industrial Research Organisation's ( CSIRO) Parkes radio telescope in Australia equipped with an innovative receiver, scientists were able to see through the stars and dust of the Milky Way, into a previously unexplored region of space. 

According to Lister Staveley-Smith, professor at The University of Western Australia node of the International Centre for Radio Astronomy Research (ICRAR), the team found 883 galaxies, a third of which had never been seen before. 

Scientists have been trying to get to the bottom of the mysterious Great Attractor since major deviations from universal expansion were first discovered in the 1970s and 1980s, said Staveley-Smith. 

"We don't actually understand what's causing this gravitational acceleration on the Milky Way or where it's coming from," he said. 

"We know that in this region there are a few very large collections of galaxies we call clusters or superclusters, and our whole Milky Way is moving towards them at more than two million kilometres per hour," he said. 

The research identified several new structures that could help to explain the movement of the Milky Way, including three galaxy concentrations (named NW1, NW2 and NW3) and two new clusters (named CW1 and CW2). 

Astronomers have been trying to map the galaxy distribution hidden behind the Milky Way for decades. 

"We've used a range of techniques but only radio observations have really succeeded in allowing us to see through the thickest foreground layer of dust and stars," said Renee Kraan-Korteweg, a professor at University of Cape Town, in South Africa. 

"An average galaxy contains 100 billion stars, so finding hundreds of new galaxies hidden behind the Milky Way points to a lot of mass we didn't know about until now," she said. 

The study was published in the Astronomical Journal

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TYPES OF GALAXIES

                  The most widely used classification scheme for galaxies is based on one devised by Edwin P. Hubble and further refined by astronomer Gerard de Vaucouleurs. It uses the three main types, and then further breaks them down by specific characteristics (openness of spirals, size and extent of bars, size of galactic bulges). In this age of multi-wavelength observing, the subclassifications also include markers for such characteristics as a galaxy’s star-formation rate and age spectrum of its stars.

Types of galaxies according to the Hubble classification scheme: an E indicates a type of elliptical galaxy; an S is a spiral; and SB is a barred-spiral galaxy

Spiral Galaxies:(s)

Spiral galaxies are the most common type in the universe. Our Milky Way is a spiral, as is the rather close-by Andromeda Galaxy. Spirals are large rotating disks of stars and nebulae, surrounded by a shell of dark matter. The central bright region at the core of a galaxy is called the “galactic bulge”. Many spirals have a halo of stars and star clusters arrayed above and below the disk.

the galaxy Messier 101 (M101, also known as NGC 5457 and also nicknamed the Pinwheel Galaxy) lies in the northern circumpolar constellation, Ursa Major (The Great Bear), at a distance of about 21 million light-years from Earth. This is one of the largest and most detailed photo of a spiral galaxy that has been released from Hubble. The galaxy's portrait is actually composed of 51 individual Hubble exposures, in addition to elements from images from ground-based photos. 

Spiral Barred Galaxies:(Sb)

Spirals that have large, bright bars of stars and material cutting across their central sections are called “barred spirals”. A large majority of galaxies have these bars, and astronomers study them to understand what function they play within the galaxy. In addition to bars, many spirals may also contain supermassive black holes in their cores. Subgroups of spirals are defined by the characteristics of their bulges, spiral arms, and how tightly wound those arms are.

Barred spiral galaxy NGC 1300 photographed by Hubble telescope.

In the core of the larger spiral structure of NGC 1300, the nucleus shows its own extraordinary and distinct "grand-design" spiral structure that is about 3,300 light-years (1 kiloparsec) long. Only galaxies with large-scale bars appear to have these grand-design inner disks — a spiral within a spiral. Models suggest that the gas in a bar can be funneled inwards, and then spiral into the center through the grand-design disk, where it can potentially fuel a central black hole. NGC 1300 is not known to have an active nucleus, however, indicating either that there is no black hole, or that it is not accreting matter.

The image was constructed from exposures taken in September 2004 by the Advanced Camera for Surveys onboard Hubble in four filters. Starlight and dust are seen in blue, visible, and infrared light. Bright star clusters are highlighted in red by their associated emission from glowing hydrogen gas. Due to the galaxy's large size, two adjacent pointings of the telescope were necessary to cover the extent of the spiral arms. The galaxy lies roughly 69 million light-years away (21 megaparsecs) in the direction of the constellation Eridanus.

Elliptical Galaxies:(e)

Elliptical galaxies are roughly egg-shaped (ellipsoidal or ovoid) found largely in galaxy clusters and smaller compact groups. Most ellipticals contain older, low-mass stars, and because they lack a great deal of star-making gas and dust clouds, there is little new star formation occurring in them. Ellipticals can have as few as a hundred million to perhaps a hundred trillion stars, and they can range in size from a few thousand light-years across to more than a few hundred thousand. Astronomers now suspect that every elliptical has a central supermassive black hole that is related to the mass of the galaxy itself. Messier 87 is an example of an elliptical galaxy. There are some subgroups of ellipticals, including “dwarf ellipticals” with properties that put them somewhere between regular ellipticals and the tightly knit groups of stars called globular clusters.

Irregular Galaxies:

Irregular galaxies are as their name suggests: irregular in shape. The best example of an irregular that can be seen from Earth is the Small Magellanic Cloud. Irregulars usually do not have enough structure to characterize them as spirals or ellipticals. They may show some bar structure, they may have active regions of star formation, and some smaller ones are listed as “dwarf irregulars”, very similar to the very earliest galaxies that formed about 13.5 billion years ago. Irregulars are characterized by their structures (or lack of them).


Other Galaxies:

shell galaxy:

A shell galaxy is a type of elliptical galaxy where the stars in the galaxy's halo are arranged in concentric shells. About one-tenth of elliptical galaxies have a shell-like structure, which has never been observed in spiral galaxies. The shell-like structures are thought to develop when a larger galaxy absorbs a smaller companion galaxy. As the two galaxy centers approach, the centers start to oscillate around a center point, the oscillation creates gravitational ripples forming the shells of stars, similar to ripples spreading on water. For example, galaxy NGC 3923 has over twenty shells

The glowing object in this image is an elliptical galaxy called NGC 3923. It is located over 90 million light-years away in the constellation of Hydra. NGC 3923 is an example of a shell galaxy where the stars in its halo are arranged in layers. NGC 3923 has over twenty shells, with only a few of the outer ones visible in this image and its shells are much more subtle than those of other shell galaxies. The shells of this galaxy are also interestingly symmetrical, while other shell galaxies are more skewed.

lenticular galaxy:

A lenticular galaxy is an intermediate form that has properties of both elliptical and spiral galaxies. These are categorized as Hubble type S0, and they possess ill-defined spiral arms with an elliptical halo of stars (barred lenticular galaxies receive Hubble classification SB0.)

This is a unique view of the disk galaxy NGC 5866 tilted nearly edge-on to our line-of-sight. Hubble's sharp vision reveals a crisp dust lane dividing the galaxy into two halves. The image highlights the galaxy's structure: a subtle, reddish bulge surrounding a bright nucleus, a blue disk of stars running parallel to the dust lane, and a transparent outer halo. NGC 5866 is a disk galaxy of type "S0" (pronounced s-zero). Viewed face on, it would look like a smooth, flat disk with little spiral structure. It remains in the spiral category because of the flatness of the main disk of stars as opposed to the more spherically rotund (or ellipsoidal) class of galaxies called ellipticals. Such S0 galaxies, with disks like spirals and large bulges like ellipticals, are called lenticular galaxies. NGC 5866 lies in the Northern constellation Draco, at a distance of 44 million light-years. It has a diameter of roughly 60,000 light-years only two-thirds the diameter of the Milky Way, although its mass is similar to our galaxy. This Hubble image of NGC 5866 is a combination of blue, green and red observations taken with the Advanced Camera for Surveys in February 2006.

Starburst:

 Black Hole-Powered Jet of Electrons and Sub-Atomic Particles Streams From Center of Galaxy M87

To celebrate the Hubble Space Telescope's 16 years of success, the two space agencies involved in the project, NASA and the European Space Agency (ESA), are releasing this image of the magnificent starburst galaxy, Messier 82 (M82). This mosaic image is the sharpest wide-angle view ever obtained of M82. The galaxy is remarkable for its bright blue disk, webs of shredded clouds, and fiery-looking plumes of glowing hydrogen blasting out of its central regions.

Throughout the galaxy's center, young stars are being born 10 times faster than they are inside our entire Milky Way Galaxy. The resulting huge concentration of young stars carved into the gas and dust at the galaxy's center. The fierce galactic superwind generated from these stars compresses enough gas to make millions of more stars.

In M82, young stars are crammed into tiny but massive star clusters. These, in turn, congregate by the dozens to make the bright patches, or "starburst clumps," in the central parts of M82. The clusters in the clumps can only be distinguished in the sharp Hubble images. Most of the pale, white objects sprinkled around the body of M82 that look like fuzzy stars are actually individual star clusters about 20 light-years across and contain up to a million stars.

The rapid rate of star formation in this galaxy eventually will be self-limiting. When star formation becomes too vigorous, it will consume or destroy the material needed to make more stars. The starburst then will subside, probably in a few tens of millions of years.

Located 12 million light-years away, M82 appears high in the northern spring sky in the direction of the constellation Ursa Major, the Great Bear. It is also called the "Cigar Galaxy" because of the elliptical shape produced by the oblique tilt of its starry disk relative to our line of sight.

The observation was made in March 2006, with the Advanced Camera for Surveys' Wide Field Channel. Astronomers assembled this six-image composite mosaic by combining exposures taken with four colored filters that capture starlight from visible and infrared wavelengths as well as the light from the glowing 

Interacting:

“This NASA Hubble Space Telescope image of the Antennae galaxies (NGC 4038 & 4039) is the sharpest yet of this merging pair of galaxies. During the course of the collision, billions of stars will be formed. The brightest and most compact of these star birth regions are called super star clusters.”

“ The two spiral galaxies started to interact a few hundred million years ago, making the Antennae galaxies one of the nearest and youngest examples of a pair of colliding galaxies. Nearly half of the faint objects in the Antennae image are young clusters containing tens of thousands of stars. The orange blobs to the left and right of image center are the two cores of the original galaxies and consist mainly of old stars criss-crossed by filaments of dust, which appear brown in the image. The two galaxies are dotted with brilliant blue star-forming regions surrounded by glowing hydrogen gas, appearing in the image in pink.”

Courtesy and source: nasa, esa, space telescope, 

What is Auroras?

What is Auroras?

If you’re ever near the North or South Pole, you may be in for a very special treat. Frequently there are beautiful light shows in the sky. These lights are called auroras. If you’re near the North Pole, it is called an aurora borealis or northern lights. If you’re near the South Pole, it is called an aurora australis or the southern lights. 

This beautiful view of the aurora was taken from the International Space Station as it crossed over the southern Indian Ocean on September 17, 2011.

What makes this happen?

Even though auroras are best seen at night, they are actually caused by the sun.

                           

The sun sends us more than heat and light; it sends lots of otherenergy and small particles our way. The protective magnetic fieldaround Earth shields us from most of the energy and particles, and we don’t even notice them.

But the sun doesn’t send the same amount of energy all the time. There is a constant streaming solar wind and there are also solar storms. During one kind of solar storm called a coronal mass ejection, the sun burps out a huge bubble of electrified gas that can travel through space at high speeds.

When a solar storm comes toward us, some of the energy and small particles can travel down the magnetic field lines at the north and south poles into Earth’s atmosphere.

                           

There, the particles interact with gases in our atmosphere resulting in beautiful displays of light in the sky. Oxygen gives off green and red light. Nitrogen glows blue and purple

The green bands of light in the sky are an aurora australis, an aurora at the south pole. Credit: Keith Vanderlinde, National Science Foundation

Do other planets get auroras?

These swirls of red light are an aurora on the south pole of Saturn. Image courtesy of NASA/ESA/STScI/A. Schaller.

They sure do! Auroras are not just something that happen on Earth. If a planet has an atmosphere and magnetic field, they probably have auroras. We’ve seen amazing auroras on Jupiter and Saturn.

                        

                     The NASA Hubble Space Telescope took this picture of a bright blue aurora on Jupiter.

credits: NASA

Why the Planets are Round?

Why the planets are round?

Scaled image of planets and sun relative to each other

Big, small, but all round

The eight planets in our solar system differ in lots of ways. They are different sizes. They are different distances from the sun. Some are small and rocky, and others are big and gassy. But they're all nice and round. Why is that? Why aren't they shaped like cubes, pyramids, or discs?

Planets form when material in space starts to bump and clump together. After a while it has enough stuff to have a good amount of gravity. That's the force that holds stuff together in space. When a forming planet is big enough, it starts to clear its path around the star it orbits. It uses its gravity to snag bits of space stuff.

A planet's gravity pulls equally from all sides. Gravity pulls from the center to the edges like the spokes of a bicycle wheel. This makes the overall shape of a planet a sphere, which is a three-dimensional circle.

Are they all perfect, though?

While all the planets in our solar system are nice and round, some are rounder than others. Mercury and Venus are the roundest of all. They are nearly perfect spheres, like marbles.

But some planets aren't quite so perfectly round.

Saturn and Jupiter are bit thicker in the middle. As they spin around, they bulge out along the equator. Why does that happen? When something spins, like a planet as it rotates, things on the outer edge have to move faster than things on the inside to keep up. This is true for anything that spins, like a wheel, a DVD, or a fan. Things along the edge have to travel the farthest and fastest.

Courtesy. NASA. 

What is Galaxy?

What is Galaxy?

We live on a planet called Earth that is part of our solar system. But where is our solar system? It’s a small part of the Milky Way Galaxy.

A galaxy is a huge collection of gas, dust, and billions of stars and their solar systems. A galaxy is held together by gravity. Our galaxy, the Milky Way, also has a supermassive black hole in the middle.

 

When you look up at stars in the night sky, you’re seeing other stars in the Milky Way. If it’s really dark, far away from lights from cities and houses, you can even see the dusty bands of the Milky Way stretch across the sky.

Courtesy. Nasa and 500px

About Space Science

Space science

Study of everything in outer space. This has sometimes been called Astronomy, but recently astronomy has come to be regarded as a division of broader space science,which has grown to include other related fields, such as studying issues related to space travel and space exploration (including space medicine), space archaeology and science performed in outer space

Milky way Galaxy