The Milky Way’s New Neighbor May Tell Us Things About the Universe


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(Click Image to Download)

As part of the Local Group, a collection of 54 galaxies and dwarf galaxies that measures 10 million light years in diameter, the Milky Way has no shortage of neighbors. However, refinements made in the field of astronomy in recent years are leading to the observation of neighbors that were previously unseen. This, in turn, is changing our view of the local universe to one where things are a lot more crowded.

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Dwarf spheroidal galaxies, like this one seen in the constellation Fornax, may exist in greater numbers than previously thought. Credit: ESO/Digital Sky Survey 2 (Click Image to Download)

For instance, scientists working out of the Special Astrophysical Observatory in Karachai-Cherkessia, Russia, recently found a previously undetected dwarf galaxy that exists 7 million light years away. The discovery of this galaxy, named KKs3, and those like it is an exciting prospect for scientists, since they can tell us much about how stars are born in our universe.

The Russian team, led by Prof Igor Karachentsev of the Special Astrophysical Observatory (SAO), used the Hubble Space Telescope Advanced Camera for Surveys (ACS) to locate KKs3 in the southern sky near the constellation of Hydrus. The discovery occurred back in August 2014, when they finalized their observations a series of stars that have only one ten-thousandth the mass of the Milky Way.

Such dwarf galaxies are far more difficult to detect than others due to a number of distinct characteristics. KKs3 is what is known as a dwarf spheroid (or dSph) galaxy, a type that has no spiral arms like the Milky Way and also suffers from an absence of raw materials (like dust and gas). Since they lack the materials to form new stars, they are generally composed of older, fainter stars.

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Image of the KKR 25 dwarf spheroid galaxy obtained by the Special Astrophysical Observatory using the HST. Credit: SAO RAS (Click Image to download)

In addition, these galaxies are typically found in close proximity to much larger galaxies, like Andromeda, which appear to have gobbled up their gas and dust long ago. Being faint in nature, and so close to far more luminous objects, is what makes them so tough to spot by direct observation.

Team member Prof Dimitry Makarov, also of the Special Astrophysical Observatory, described the process: “Finding objects like Kks3 is painstaking work, even with observatories like the Hubble Space Telescope. But with persistence, we’re slowly building up a map of our local neighborhood, which turns out to be less empty than we thought. It may be that are a huge number of dwarf spheroidal galaxies out there, something that would have profound consequences for our ideas about the evolution of the cosmos.”

Painstaking is no exaggeration. Since they are devoid of materials like clouds of gas and dust fields, scientists are forced to spot these galaxies by identifying individual stars. Because of this, only one other isolated dwarf spheroidal has been found in the Local Group: a dSph known as KKR 25, which was also discovered by the Russian research team back in 1999.

But despite the challenges of spotting them, astronomers are eager to find more examples of dSph galaxies. As it stands, it is believed that these isolated spheroids must have been born out of a period of rapid star formation, before the galaxies were stripped of their dust and gas or used them all up.

Studying more of these galaxies can therefore tell us much about the process star formation in our universe. The Russian team expects that the task will become easier in the coming years as the James Webb Space Telescope and the European Extremely Large Telescope begin service.

Much like the Spitzer Space Telescope, these next-generation telescopes are optimized for infrared detection and will therefore prove very useful in picking out faint stars. This, in turn, will also give us a more complete understanding of our universe and all that it holds.

Source : universe today

Webb Space Telescope promises astronomers new scientific adventures


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Astronomers are hoping that the Webb will be able to collect light that is very far away from us and is moving still farther away. The universe has been expanding ever since the big bang got it started, but scientists reckon that if the telescope is powerful enough, they just might be able to see the birth of the first galaxies, some 13.5 billion years ago.

“This is similar to archaeology,” says Harvard astrophysicist Avi Loeb, who helped plan Webb’s science mission. “We are digging deep into the universe. But as the sources of light become fainter and farther away, you need a big telescope like the James Webb.”

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Named for a former NASA director, the 21-foot-diameter Webb telescope will be 100 times as powerful as the Hubble Space Telescope, which was launched in 1990. Although Hubble wasn’t the first space telescope, its images of far-off objects have dazzled the public and led to breakthroughs in astrophysics, such as determining how fast the universe is expanding.

The Webb will be both bigger and located in a darker part of space than Hubble, enabling it to capture images from the faintest galaxies. Four infrared cameras will capture light that is moving away from us very quickly and that has shifted from the visible to the infrared spectrum, described as red-shifted. The advantage of using infrared light is that it is not blocked by clouds of gas and dust that may lie between the telescope and the light. Webb’s mirrors are covered in a thin layer of gold that absorbs blue light but reflects yellow and red visible light, and its cameras will detect infrared light and a small part of the visible spectrum. As objects move away from us, the wavelength of their light shifts from visible light to infrared light. That’s why the Webb’s infrared cameras will be able to see things that are both far away and moving away from us.

In the meantime, scientists such as Sara Seager of MIT, who studies exoplanets that revolve around distant stars, are imagining the discoveries that will occur once Webb directs its mirrors toward deep space. As a planet moves in front of a star, researchers hope to see the fingerprints of its atmosphere, which absorbs starlight. By analyzing the chemical spectrum of the light, they may be able to determine the atmosphere’s composition. Oxygen has a spectral fingerprint, as does methane, carbon dioxide and other gases found in atmospheres.

Continue reading Webb Space Telescope promises astronomers new scientific adventures