The coldest place in the universe

photo: This Hubble image was recorded using polarizing filters (analogous to polaroid sunglasses) and color coded by the angle associated with the polarized light.

The Boomerang Nebula (also called the Bow Tie Nebula) is a protoplanetary nebula located 5,000 light-years away from Earth in the Centaurus constellation. The nebula is measured at 1 K (−272.15 °C/−457.87 °F), the coldest place known in the universe. The Boomerang Nebula was formed from the outflow of gas from a star at its core. The gas is moving outwards at a speed of about 164 km/s and expanding rapidly as it moves out into space. This expansion is the cause of the nebula's very low temperature.The Boomerang Nebula was photographed in detail by the Hubble Space Telescope in 1998. It is believed that the nebula is a star or stellar system evolving toward the planetary nebula phase.Keith Taylor and Mike Scarrott called it the 'Boomerang Nebula' in 1980 after observing it with the Anglo-Australian telescope at the Siding Spring Observatory. Unable to view it with the same detail as with the Hubble, the astronomers saw merely a slight asymmetry in the nebula's lobes, suggesting a curved shape like a boomerang. The high-resolution Hubble images indicate that the 'Bow Tie Nebula' would perhaps have been a better name.The Boomerang Nebula is one of the Universe's peculiar places. In 1995, using the 15-metre Swedish ESO Submillimetre Telescope in Chile, astronomers revealed that it is the coldest place in the Universe found so far. With a temperature of −272 °C, it is only 1 kelvin warmer than absolute zero (the lowest limit for all temperatures). Even the −270 °C background glow from the Big Bang is warmer than this nebula. It is the only object found so far that has a temperature lower than the background radiation.The Hubble Space Telescope has "caught" the Boomerang Nebula in these new images taken with the Advanced Camera for Surveys. This reflecting cloud of dust and gas has two nearly symmetric lobes (or cones) of matter that are being ejected from a central star. Over the last 1,500 years, nearly one and a half times the mass of our Sun has been lost by the central star of the Boomerang Nebula in an ejection process known as a bipolar outflow. The nebula's name is derived from its symmetric structure as seen from ground-based telescopes. Hubble's sharp view is able to resolve patterns and ripples in the nebula very close to the central star that are not visible from the ground.This Nebula is the coldest place yet found anywhere in the universe.

37-Year Search for Source of Mysterious 'X-ray Background' Ends

Date: 14 January 2000

Armed with the potent imaging power of the Chandra space telescope, a team of scientists claims to have answered a 37-year old question that has poked at astronomers since humanity’s first foray into high-energy astronomy: the mystery of the X-ray background radiation.

The Chandra telescope has given these scientists a glimpse at the source of the diffuse X-ray glow that seems to permeate the entire universe, said Richard Mushotzky, a researcher at NASA’s Goddard Space Flight Center.

That glow is produced by a "new class of objects" scattered throughout the universe that emit X-ray radiation, he said. The objects aren’t exactly unknown, but they were never before shown to be the sources of X-ray radiation, said Mushotzky, who leads a group of astronomers that used Chandra to study the puzzling universal X-ray glow.

He announced the discovery here Thursday at the meeting of the American Astronomical Society.X-ray astronomy must be done from space because Earth’s atmosphere blocks out X-ray radiation – the energy that comes from some of the hottest, most energetic objects in the universe.

The very first rocket flight that was capable of X-ray astronomy observed a diffuse glow that seemed to permeate the universe in every direction. The phenomenon was dubbed the X-ray background, and it has defied definitive explanation ever since.

Chandra’s ability to see objects 100 times fainter than previous X-ray instruments, though, means the telescope was, in some sense, built for the task, Mushotzky said.

The telescope allowed the astronomers to see the points that were emitting the peculiar brand of X-rays that seemed to come from everywhere and nowhere at all, and they discovered that these points were found throughout the universe -- perhaps 100 million of them spread over the entire sky, Mushotzky said.

"The heart of the background is made up of a rich assortment of X-ray sources which could not have been discovered by previous satellite missions," said Amy Barger, a University of Hawaii astronomer who worked to find optical counterparts to the X-ray sources.

Using ground-based telescopes, Barger chased down the source of many of the X-ray points and found that they could be classified into four categories.

Some of the X-rays come from galaxy clusters, and some from the energetic active galactic nuclei known as quasars. A third source seems to be bright galaxies, which look in most respects like any normal run-of-the-mill galaxy. The final category of sources simply can’t be seen at visible wavelengths, so Barger calls this class "optically-faint objects."

Most likely, the sources in all these cases are super-massive black holes, either in the centers of galaxies or galaxy clusters, or hidden from view by surrounding clouds of dust, Barger said.

She reasons that the optically faint sources might be black holes so shrouded by gunk that visible light is blocked out while X-rays escape to scatter throughout the universe.

Astronomers who worked on the problem are relieved, and are hailing the discovery as something big. Still, the answer is not a complete surprise, for many scientists have suggested that the background must be created by a diverse array of objects throughout the universe. Still, until now it has never been proved, Mushotzky said.

For years the uncertainty of the X-ray background's source has been an irritant to cosmologists, said Virginia Trimble, of the University of California at Irvine.

Trimble, who is not affiliated with the team that announced the discovery said that knowing the sources of the X-ray radiation should help cosmologists develop better understandings about the overall shape and structure of the universe. One of the great questions of the day, she said, is why is the universe lumpy, and not smooth and homogeneous throughout. The new discovery could help answer those questions, Trimble said.

"The X-ray background has subtle fluctuations in it. You could use those to trace large-scale structure if only you knew what was making that X-ray background. We now know what is making that X-ray background," she said.

Red Spot Junior

Photo: Hubble Spaps "Red Spot Junior"

NASA's Hubble Space Telescope is giving astronomers their most detailed view yet of a second red spot emerging on Jupiter. For the first time in history, astronomers have witnessed the birth of a new red spot on the giant planet, which is located half a billion miles away. The storm is roughly one-half the diameter of its bigger and legendary cousin, the Great Red Spot. Researchers suggest that the new spot may be related to a possible major climate change in Jupiter's atmosphere.

Like a butterfly In the Sky

photo: NGC 2440 Cocoon of a new White Dwarf

Like a butterfly, a white dwarf star begins its life by casting off a cocoon that enclosed its former self. In this analogy, however, the Sun would be a catepillar and the ejected shell of gas would become the prettiest of all! In the above cocoon, the planetary nebula designated NGC 2440, contains one of the hottest white dwarf stars known. The white dwarf can be seen as the bright dot near the photo's center. Our Sun will eventually become a white dwarf butterfly, but not for another 5 billion years. The false color image was post-processed by Forrest Hamilton.

Comet 73P Schwassman-Wachmann

photo: Comet 73P Schwassman-Wachmann

This infrared image from NASA's Spitzer Space Telescope shows the broken Comet 73P/Schwassman-Wachmann 3 skimming along a trail of debris left during its multiple trips around the sun. The flame-like objects are the comet's fragments and their tails, while the dusty comet trail is the line bridging the fragments.

Comet 73P /Schwassman-Wachmann 3 began to splinter apart in 1995 during one of its voyages around the sweltering sun. Since then, the comet has continued to disintegrate into dozens of fragments, at least 36 of which can be seen here. Astronomers believe the icy comet cracked due the thermal stress from the sun.

The Spitzer image provides the best look yet at the trail of debris left in the comet's wake after its 1995 breakup. The observatory's infrared eyes were able to see the dusty comet bits and pieces, which are warmed by sunlight and glow at infrared wavelengths. This comet debris ranges in size from pebbles to large boulders. When Earth passes near this rocky trail every year, the comet rubble burns up in our atmosphere, lighting up the sky in meteor showers. In 2022, Earth is expected to cross close to the comet's trail, producing a noticeable meteor shower.

Astronomers are studying the Spitzer image for clues to the comet's composition and how it fell apart. Like NASA's Deep Impact experiment, in which a probe smashed into comet Tempel 1, the cracked Comet 73P/Schwassman-Wachmann 3 provides a perfect laboratory for studying the pristine interior of a comet.

This image was taken from May 4 to May 6 by Spitzer's Multiband Imaging Photometer, using its 24-micron wavelength channel.

Galaxy Cluster SDSS J1004+4112

photo: Galaxy Cluster SDSS J1004+4112
NASA's Hubble Space Telescope has captured the first-ever picture of a group of five star-like images of a single distant quasar.

The multiple-image effect seen in the Hubble picture is produced by a process called gravitational lensing, in which the gravitational field of a massive object — in this case, a cluster of galaxies — bends and amplifies light from an object — in this case, a quasar — farther behind it.

Where did all the stars go?

photo: Molecular cloud Barnard 68

What used to be considered a hole in the sky is now known to astronomers as a dark molecular cloud . Here, a high concentration of dust and molecular gas absorb practically all the visible light emitted from background stars. The eerily dark surroundings help make the interiors of molecular cloudssome of the coldest and most isolated places in the universe. One of the most notable of these dark absorption nebulae is a cloud toward the constellation Ophiucus known as Barnard 68. That no stars are visible in the center indicates that Barnard 68 is relatively nearby, with measurements placing it about 500 light-years away and half al igth-year across. It is not known exactly how molecular clouds like Barnard 68 form, but it is known that these clouds are themselves likely placesfor new stars to form. It is possible to look right through the cloud in infrared light.

Eyes in the Sky

photo:NGC 2207 and IC 2163

These shape-shifting galaxies have taken on the form of a giant mask. The icy blue eyes are actually the cores of two merging galaxies, called NGC 2207 and IC 2163, and the mask is their spiral arms. The false-colored image consists of infrared data from NASA's Spitzer Space Telescope (red) and visible data from NASA's Hubble Space Telescope (blue/green).

NGC 2207 and IC 2163 met and began a sort of gravitational tango about 40 million years ago. The two galaxies are tugging at each other, stimulating new stars to form. Eventually, this cosmic ball will come to an end, when the galaxies meld into one. The dancing duo is located 140 million light-years away in the Canis Major constellation.

The infrared data from Spitzer highlight the galaxies' dusty regions, while the visible data from Hubble indicates starlight. In the Hubble-only image (not pictured here), the dusty regions appear as dark lanes.

The Hubble data correspond to light with wavelengths of .44 and .55 microns (blue and green, respectively). The Spitzer data represent light of 8 microns.

Stephan’s Quintet Galaxy Cluster - Credit: NASA/JPL-Caltech/Max Planck Institute

This false-color composite image of the Stephan’s Quintet galaxy cluster clearly shows one of the largest shock waves ever seen (green arc). The wave was produced by one galaxy falling toward another at speeds of more than one million miles per hour. The image is made up of data from NASA's Spitzer Space Telescope and a ground-based telescope in Spain.

Four of the five galaxies in this picture are involved in a violent collision, which has already stripped most of the hydrogen gas from the interiors of the galaxies. The centers of the galaxies appear as bright yellow-pink knots inside a blue haze of stars, and the galaxy producing all the turmoil, NGC7318b, is the left of two small bright regions in the middle right of the image. One galaxy, the large spiral at the bottom left of the image, is a foreground object and is not associated with the cluster.

The titanic shock wave, larger than our own Milky Way galaxy, was detected by the ground-based telescope using visible-light wavelengths. It consists of hot hydrogen gas. As NGC7318b collides with gas spread throughout the cluster, atoms of hydrogen are heated in the shock wave, producing the green glow.

Stephan's Quintet is located 300 million light-years away in the Pegasus constellation.

CG4 - A Ruptured Cometary Globule

Can a gas cloud eat a galaxy? It's not even close. The odd looking "creature" in the center of the photo is a gas cloud known as a cometary globule . This globule, however, has ruptured. Cometary globules are typically characterized by dusty heads and elongated tails . These features cause cometary globules to have visual similarities to comets, but in reality they are very much different. Globules are frequently the birthplaces of stars, and many show very young stars in their heads. The reason for the rupture in the head of this object is not completely known. The galaxy to the left of center is huge, very far in the distance, and only placed near CG4 by chance superposition.