Category: Astronomy

Artist’s impression of the Milky Way. Image credit: NASA/JPL-Caltech/R Click to enlarge
With the help of NASA’s Spitzer Space Telescope, astronomers have conducted the most comprehensive structural analysis of our galaxy and have found tantalizing new evidence that the Milky Way is much different from your ordinary spiral galaxy.

The survey using the orbiting infrared telescope provides the fine details of a long central bar feature that distinguishes the Milky Way from more pedestrian spiral galaxies.

“This is the best evidence ever for this long central bar in our galaxy,” says Ed Churchwell, a UW-Madison professor of astronomy and a senior author of a paper describing the new work in an upcoming edition of Astrophysical Journal Letters, a leading astronomy journal.

Using the orbiting infrared telescope, the group of astronomers surveyed some 30 million stars in the plane of the galaxy in an effort to build a detailed portrait of the inner regions of the Milky Way. The task, according to Churchwell, is like trying to describe the boundaries of a forest from a vantage point deep within the woods: “This is hard to do from within the galaxy.”

Spitzer’s capabilities, however, helped the astronomers cut through obscuring clouds of interstellar dust to gather infrared starlight from tens of millions of stars at the center of the galaxy. The new survey gives the most detailed picture to date of the inner regions of the Milky Way.

“We’re observing at wavelengths where the galaxy is more transparent, and we’re bringing tens of millions of objects into the equation,” says Robert Benjamin, the lead author of the new study and a professor of physics at the University of Wisconsin-Whitewater.

The possibility that the Milky Way Galaxy has a long stellar bar through its center has long been considered by astronomers, and such phenomena are not unheard of in galactic taxonomy. They are clearly evident in other galaxies, and it is a structural characteristic that adds definition beyond the swirling arms of typical spiral galaxies.

The new study provides the best estimates for the size and orientation of the bar, which are far different from previous estimates.

It shows a bar, consisting of relatively old and red stars, spanning the center of the galaxy roughly 27,000 light years in length – 7,000 light years longer than previously believed. It also shows that the bar is oriented at about a 45-degree angle relative to a line joining the sun and the center of the galaxy.

Previously, astronomers debated whether a presumed central feature of the galaxy would be a bar structure or a central ellipse – or both. The new research, the Wisconsin astronomers say, clearly shows a bar-like structure.

“To date, this is the best evidence for a long bar in our galaxy,” Benjamin asserts. “It’s hard to argue with this data.”

The Spitzer Space Telescope was lofted into orbit in August of 2003. It consists of a telescope and three science instruments, including the Infrared Array Camera, the primary instrument used for the new survey, known as GLIMPSE for Galactic Legacy Mid-Plane Survey Extraordinaire.

NASA’s Jet Propulsion Laboratory (JPL), Pasadena, Calif., manages the Spitzer Space Telescope mission for NASA’s Science Mission Directorate, Washington, D.C. Science operations are conducted at the Spitzer Science Center in Pasadena. JPL is a division of the California Institute of Technology.

Original Source: UW-Madison News Release

A wide-field view of NGC 300. Image credit: AAO-David Malin/Gemini Observatory. Click to enlarge
Like archaeologists unearthing a ‘lost city,’ astronomers using the 8-meter Gemini South telescope have revealed that the galaxy NGC 300 has a large, faint extended disk made of ancient stars, enlarging the known diameter of the galaxy by a factor of two or more.

The finding also implies that our own Milky Way Galaxy could be much larger than current textbooks say. Scientists will also need to explain the mystery of how galaxies like NGC 300 can form with stars so far from their centers.

The research, by an Australian and American team of scientists was just published in the August 10, 2005 issue of the Astrophysical Journal.

The team used the Gemini Multi-Object Spectrograph on the Gemini South telescope in Chile, and were able to clearly resolve extremely faint stars in the disk up to 47,000 light-years from the galaxy?s center?double the previously known radius of the disk. To detect these stars, images were obtained that went more than ten times ?deeper? than any previous images of this galaxy (Figure 1).

?A few billion years ago the outskirts of NGC 300 were brightly lit suburbs that would have shown up as clearly as its inner metropolis,? said the paper?s lead author, Professor Joss Bland-Hawthorn of the Anglo-Australian Observatory in Sydney, Australia. ?But the suburbs have dimmed with time, and are now inhabited only by faint, old stars?stars that need large telescopes such as Gemini South to detect them.?

The finding has profound implications for our own galaxy since most current estimates put the size of our Milky Way at about 100,000 light-years or about the size now estimated for NGC 300. ?However, the galaxy is much more massive and brighter than NGC 300 so on this basis, our galaxy is also probably much larger than we previously thought?perhaps as much as 200,000 light-years across,? said Bland-Hawthorn.

The Galaxy That Keeps On Keeping On!

Adding to these compelling findings is the fact that the team found no evidence for truncating, or an abrupt ?cutting-off’ of the star population as seen in many galaxies further from the central regions.

Team member Professor Bruce Draine of Princeton University explains: “It’s hard to understand how such an extensive stellar disk that falls off so smoothly in density could have formed ? this is really a huge surprise to us. Because it takes an incredibly long time to evenly disperse stars from a galaxy’s central disk to these extreme distances, it seems more likely that we are seeing the results of star formation that took place long ago, perhaps as much as ten billion years ago.”

?We now realize that there are distinctly different types of galaxy disks,? said team member Professor Ken Freeman of the Research School of Astronomy and Astrophysics at the Australian National University. ?Probably most galaxies are truncated?the density of stars in the disk drops off sharply. But NGC 300 just seems to go on forever. The density of stars in the disk falls off very smoothly and gradually.?

The observers traced NGC 300?s disk out to the point where the surface density of stars was equivalent to a one-thousandth of a sun per square light-year. ?This is the most extended and diffuse population of stars ever seen,? said Bland-Hawthorn.

NGC 300 is a spiral member of the Sculptor group of galaxies, the closest extragalactic cluster to us, and is about 6.1 million light-years away. Most of its stars lie in a fairly flat disk making it appear to be a very normal spiral galaxy like our Milky Way. NGC 300 is the first galaxy outside of our Local Group to be studied to this depth. There have only been two others studied to such faint levels, the Andromeda galaxy and its neighbor M33, both in our Local Group (see adjacent background information box).

The researchers have been granted more time on Gemini South to determine exactly what kind of stars they are seeing in the outskirts of NGC 300, and to make similar studies of other galaxies.

?We still have a lot to learn about how galaxies like ours formed,? said Bland-Hawthorn. ?Our next Gemini observations, that we have planned for later this year, should provide even more important clues and hopefully even more surprises!?

Original Source: Gemini Observatory

Spiral galaxy NGC 4565. Image credit: ESO Click to enlarge
How does the Galaxy in which we live look like?

It is almost certain that we will never be able to send a probe out of our Milky Way to take a snapshot, in the same way as the first satellites could do to give us striking images of planet Earth. But astronomers do not need this to imagine what our bigger home resembles. And they have a pretty good idea of it.

The Milky Way with its several hundreds of billion stars is thought to be a relatively flat disc -100,000 light-year across- with a central bulge lying in the direction of the constellation Sagittarius (The Archer) and six spiral arms. The Milky Way has most probably also a central bar made of young, bright stars.

If we can’t take pictures of the Milky Way, we may photograph others galaxies which astronomers think look similar to it. The two galaxies presented here are just two magnificient examples of barred spiral galaxies. One – Messier 83 – is seen face-on, and the other – NGC 4565 – appears edge-on. Together, they give us a nice idea of how the Milky Way may appear from outer space.

These images are based on data obtained with the twin FORS1 and FORS2 (FOcal Reducer and Spectrograph) instruments attached to two ESO’s 8.2-m Unit Telescopes of the Very Large Telescope Array located on Cerro Paranal. The data were extracted from the ESO Science Archive Facility, which contains approximately 50 Terabytes of scientific data and is, since April 1, 2005, open to the worldwide community. These invaluable data have already led to the publication of more than 1000 scientific papers. They also contains many nice examples of beautiful astronomical objects which could be the theme of as many midsummer’s dreams.

NGC 4565

The first galaxy pictured here is NGC 4565, which for obvious reasons is also called the Needle Galaxy. First spotted in 1785 by Uranus’ discoverer, Sir William Herschel (1738-1822), this is one of the most famous example of an edge-on spiral galaxy and is located some 30 million light-years away in the constellation Coma Berenices (Berenice’s Hair). It displays a bright yellowish central bulge that juts out above most impressive dust lanes.

Because it is relatively close (it is only 12 times farther away than Messier 31, the Andromeda galaxy, which is the major galaxy closest to us) and relatively large (roughly one third larger than the Milky Way), it does not fit entirely into the field of view of the FORS instrument (about 7 x 7 arcmin2).

Many background galaxies are also visible in this FORS image, giving full meaning to their nickname of “island universes”.

Messier 83

If our Milky Way were to resemble this one, we certainly would be proud of our home! The beautiful spiral galaxy Messier 83 is located in the southern constellation Hydra (the Water Snake) and is also known as NGC 5236 and as the Southern Pinwheel galaxy. Its distance is about 15 million light-years. Being about twice as small as the Milky Way, its size on the sky is 11×10 arcmin2.

The image show clumpy, well-defined spiral arms that are rich in young stars, while the disc reveals a complex system of intricate dust lanes. This galaxy is known to be a site of vigorous star formation.

Original Source: ESO News Release

Artist illustration of the newly discovered 10th planet. Image credit: NASA/JPL. Click to enlarge.
At the same time, another team led by astronomer Mike Brown of Caltech reported they had been observing 2003 EL61 for almost a year, but were waiting to analyze data from the Spitzer Space Telescope before announcing the discovery.

“There is no question that the Spanish group is rightly credited with discovery,” Brown stated on his personal website. “Even if they had found the object only this year and announced its existence, they would still be considered the rightful discovers. We took a chance that no one else would find it while we were awaiting our observations from the Spitzer Space Telescope. We were wrong! And we congratulate our colleagues on a very nice discovery.”

But just hours after that, Brown announced to the media the discovery of two other big TNOs, designated as 2003UB313 and 2005 FY9. Regarding the first one, he stated that it’s about three times as far from the Sun as Pluto, and “it’s definitely bigger” than the ninth planet.

Brown’s team discovered 2003 ub313 on January 8th, but wanted to further analyze their observations. However, they “were forced to announce their results on Friday evening because word had leaked out” he said.

“In mid-July, short abstracts of scientific talks to be given at a meeting in September became available on the web. We intended to talk about the object now known as 2003 EL61, which we had discovered around Christmas of 2004, and the abstracts were designed to whet the appetite of the scientists who were attending the meeting. In these abstracts we call the object a name that our software automatically assigned, K40506A -the first Kuiper belt object we discovered in data from 2004/05/06, May 6th-. Using this name was a very very bad idea on our part.”

“Unbeknownst to us, some of the telescopes that we had been using to study this object keep open logs of who has been observing, where they have been observing, and what they have been observing. A two-second Google search of “K40506A” immediately reveals these observing logs”.

According to Brown, from the moment the abstracts became public, anyone with an Internet connection and a little curiosity about the “K40506A” object could have found out where it was.

Brown was quick to point that he believes the fact that this discovery happened days after the data were potentially available on the Web is a coincidence. But “some people in the community privately expressed their concerns to me that this coincidence was too good to be true and wanted to know if there was any possible way that anyone could have found out the location of our object,” he added.

At this point, Brown contacted Brian Marsden at the International Astronomical Union’s Minor Planet Center (MPC). Brown told him confidentially about the two objects not yet announced (2003 UB313 and 2005 FY9), expressed his concerns that someone might be able to find their data and attempt to claim credit for discovering these objects, and sought advice.

Marden found that someone had already used the website of the MPC to access past observations of one of the objects and predict its location for that night. The past observations were precisely the logs from the telescope that Brown’s group had been using. “We had no choice but to hastily pull together a press conference which was held at 4pm on the last Friday in July, perhaps the single best time to announce news that you want no one to hear”, said Brown.

However, some astronomers have a very different opinion about Brown’s announcement.

“The group of Dr. Brown decided, as in previous cases, not to make public its detection until they finished their observations and their research work, and until the object was in conjunction with the Sun so that other people couldn’t observe it,” stated Dr. Javier Licandro in an e-mail sent to a Spanish-speaking astronomy mailing list. Licandro works at the Isaac Newton Group of Telescopes and the Instituto de Astrof?sica de Canarias, in Spain.

“They did it before with Sedna. But this time, by taking this ‘doubtful’ risk, they lost all the rights on the discovery of that object. Even more, their policy is, at least, criticizeable.”

“Due to the detection of 2003 EL61 by Ortiz et. al., and because of the fiasco that this has represented for Brown et. al., they decided to go public ‘ipso factum’ with their discoveries of two other objects that they knew at least from six months ago, 2005 FY y 2003 UB313,” said Licandro.

Contacted by AstronomiaOnline.com, Brown wouldn’t want to elaborate on Licandro’s comments. “I like Javier. It is unfortunate he feels the need to make such remarks,” he said.

But it didn’t take long for Ortiz to air his own feelings about the situation. “With technology many times more advanced than our own, Brown’s team had discovered three big objects many months ago, but they were hiding their findings from the international scientific community, as they did before with Quaoar and Sedna,” he declared to the Spaniard paper ABC.

“This secrecy was useful to Brown, as it allowed him to study the object in detail and exclusively. But his actions harm science and don’t follow the established procedures that imply notifying the existence of a new object to the astronomical community as soon as it’s discovered,” added Ortiz.

Brown indicated that he didn’t get that statement from Ortiz himself, so he would not want to comment on it directly. However, asked again by AstronomiaOnline.com, he said: “In general, there certainly are people who have that opinion, to which they are entitled. I, however, cannot think of any area of science in which an ‘established procedure’ is to announce a discovery with no time for thought and analysis. Anyone who feels otherwise is welcome to go and find these objects themselves -as did Ortiz- and get the credit for their own discoveries.”

Written by Ricardo J. Tohmé for Astronom?aOnline. If you want to read the original article in Spanish, click here.

A distant galaxy (yellow) that houses a quasar. Image credit: NASA Click to enlarge
Most of the biggest black holes in the universe have been eating cosmic meals behind closed doors ? until now.

With its sharp infrared eyes, NASA’s Spitzer Space Telescope peered through walls of galactic dust to uncover what may be the long-sought missing population of hungry black holes known as quasars.

“From past studies using X-rays, we expected there were a lot of hidden quasars, but we couldn’t find them,” said Alejo Martinez-Sansigre of the University of Oxford, England. He is lead author of a paper about the research in this week’s Nature. “We had to wait for Spitzer to find an entire population of these dust-obscured objects.”

Quasars are super-massive black holes that are circled by a giant ring of gas and dust. They live at the heart of distant galaxies and can consume up to the equivalent mass of one thousand stars in a single year. As their black holes suck in material from their dusty rings, the material lights up brilliantly, making quasars the brightest objects in the universe. This bright light comes in many forms, including X-rays, visible and infrared light.

Astronomers have puzzled for years over the question of how many of these cosmic behemoths are out there. One standard method for estimating the number is to measure the cosmic X-ray background. Quasars outshine everything else in the universe in X-rays. By counting the background buzz of X-rays, it is possible to predict the approximate total number of quasars.

But this estimate has not matched previous X-ray and visible-light observations of actual quasars, which number far fewer than expected. Astronomers thought this might be because most quasars are blocked from our view by gas and dust. They proposed that some quasars are positioned in such a way that their dusty rings hide their light, while others are buried in dust-drenched galaxies.

Spitzer appears to have found both types of missing quasars by looking in infrared light. Unlike X-rays and visible light, infrared light can travel through gas and dust.

Researchers found 21 examples of these quasars in a small patch of sky. All the objects were confirmed as quasars by the National Radio Astronomy Observatory’s Very Large Array radio telescope in New Mexico and by the Particle Physics and Astronomy Research Council’s William Herschel Telescope in Spain.

“If you extrapolate our 21 quasars out to the rest of the sky, you get a whole lot of quasars,” said Dr. Mark Lacy of the Spitzer Science Center, California Institute of Technology, Pasadena, Calif., a co-author of the Nature paper. “This means that, as suspected, most super-massive black hole growth is hidden by dust.”

The discovery will allow astronomers to put together a more complete picture of how and where quasars form in our universe. Of the 21 quasars uncovered by Spitzer, 10 are believed to be inside fairly mature, giant, elliptical galaxies. The rest are thought to be encased in thick, dusty galaxies that are still forming stars.

A team of researchers based at the University of Arizona, Tucson, found similar quasars using Spitzer. Their research is described at http://uanews.org/science.

Other authors of the Nature paper include Drs. Steve Rawlings and Matt Jarvis, University of Oxford; Drs. Dario Fadda and Francine Marleau, Spitzer Science Center; Dr. Chris Simpson, University of Durham, England; and Dr. Chris Willott, National Research Council Canada, Victoria.

The Jet Propulsion Laboratory, Pasadena, Calif., a division of Caltech, manages the Spitzer Space Telescope mission for NASA’s Science Mission Directorate, Washington. Science operations are conducted at the Spitzer Science Center at Caltech. Spitzer’s multiband imaging photometer, which observed the quasars, was built by Ball Aerospace Corporation, Boulder, Colo.; the University of Arizona; and Boeing North America, Canoga Park, Calif. Spitzer’s infrared array camera, which also observed the quasars, was built by NASA Goddard Space Flight Center, Greenbelt, Md.

A Spitzer false-colored picture of one of the newfound quasars is available at http://www.spitzer.caltech.edu/Media/index.shtml.

For information about NASA and agency programs visit http://www.nasa.gov/home/.

Original Source: NASA News Release

Observed Fields in NGC 300. Image credit: ESO Click to enlarge
Cepheid pulsating stars have been used as distance indicators since the early discovery of Henrietta Leavitt almost a hundred years ago. From her photographic data regarding one of the Milky Way’s neighbour galaxies, the Small Magellanic Cloud, she found that the brightness of these stars closely correlate with their pulsation periods.

This period-luminosity relation, once calibrated, allows a precise distance determination of a galaxy once Cepheids have been discovered in it, and their periods and mean magnitudes have been measured.

While the Cepheid method doesn’t reach out far enough in the Universe to directly determine cosmological parameters like the Hubble constant, Cepheid distances to relatively nearby resolved galaxies have laid the foundation for such work in the past, as in the Hubble Space Telescope Key Project on the Extragalactic Distance Scale. Cepheids indeed constitute one of the first steps in the cosmic distance ladder.

The current main problem with the Cepheid method is that its dependence on a galaxy’s metallicity, that is, its content in elements more heavy than hydrogen and helium, has never been measured accurately so far. Another intriguing difficulty with the method is the fact that the total absorption of the Cepheid’s light on its way to Earth, and in particular the amount of absorption within the Cepheid’s host galaxy, must be precisely established to avoid significant errors in the distance determination.

To tackle this problem, Wolfgang Gieren (University of Concepcion, Chile) and his team devised a Large Programme at ESO: the Araucaria Project. Its aim is to obtain distances to relatively nearby galaxies with a precision better than 5 percent.

One of the key galaxies of the team’s Araucaria Project is the beautiful, near face-on galaxy NGC 300 in the Sculptor Group. In a wide-field imaging survey carried out at the ESO/MPG 2.2-m telescope on La Silla in 1999-2000, the team had discovered more than a hundred Cepheid variables spanning a broad range in pulsation period. Pictures of the galaxy, and some of its Cepheids from these data were released in ESO Press Photos 18a-h in 2002. Last year, the team presented the distance of NGC 300 as derived from these optical images in V- and I-bands.

The team complemented this unique dataset with new data taken with the ISAAC near-infrared camera and spectrometer on ESO’s 8.2-m VLT Antu telescope.

“There are three substantial advantages in the Cepheid distance work when images obtained through near-infrared passbands are used instead of optical data”, says Wolfgang Gieren. The most important gain is the fact that the absorption of starlight in the near-infrared, and particularly in the K-band, is dramatically reduced as compared to the effect interstellar matter has at visible wavelengths. A second advantage is that Cepheid light curves in the infrared have smaller amplitudes and are much more symmetrical than their optical counterparts, making it possible to measure a Cepheid’s mean K-band brightness just from a very few, and in principle from just one observation at known pulsation phase. In contrast, optical work requires the observation of full light curves to determine accurate mean magnitudes. The third basic advantage in the infrared is a reduced sensitivity of the period-luminosity relation to metallicity, and to blending with other stars in the crowded fields of a distant galaxy.

Taking this into account, one of the main purposes of the team’s Large Programme has been to conduct near-infrared follow-up observations of Cepheids in their project’s target galaxies which have previously been discovered in optical wide-field surveys.

Deep images in the J and K bands of three fields in NGC 300 containing 16 Cepheids were taken with VLT/ISAAC in 2003.

“The high quality of the data allowed a very accurate measurement of the mean J- and K- magnitudes of the Cepheids from just 2 observations of each star obtained at different times”, says Grzegorz Pietrzynski, another member of the team, also from Concepcion.

Using these remarkable data the period-luminosity relations were constructed. “They are the most accurate infrared PL relations ever obtained for a Cepheid sample in a galaxy beyond the Magellanic Clouds”, emphasizes Wolfgang Gieren.

The total absorption of light (“reddening”) of the Cepheids in NGC 300 was obtained by combining the values for the distance of the galaxy obtained in the various optical and near-infrared bands in which NGC 300 was observed. This led to the discovery that there is a very significant contribution to the total reddening from absorption intrinsic to NGC 300. This intrinsic absorption has an important effect on the determination of the distance but had not been taken into account previously.

The team was able to measure the distance to NGC 300 with the unprecedented total uncertainty of only about 3 percent. The astronomers found that NGC 300 is located 6.13 million light-years away.

Original Source: ESO News Release

This new planet is larger than Pluto. Image credit: NASA/JPL. Click to enlarge.
A planet larger than Pluto has been discovered in the outlying regions of the solar system.

The 10th planet was discovered using the Samuel Oschin Telescope at Palomar Observatory near San Diego, Calif. The discovery was announced today by planetary scientist Dr. Mike Brown of the California Institute of Technology in Pasadena, Calif., whose research is partly funded by NASA.

The planet is a typical member of the Kuiper belt, but its sheer size in relation to the nine known planets means that it can only be classified as a planet, Brown said. Currently about 97 times further from the sun than the Earth, the planet is the farthest-known object in the solar system, and the third brightest of the Kuiper belt objects.

“It will be visible with a telescope over the next six months and is currently almost directly overhead in the early-morning eastern sky, in the constellation Cetus,” said Brown, who made the discovery with colleagues Chad Trujillo, of the Gemini Observatory in Mauna Kea, Hawaii, and David Rabinowitz, of Yale University, New Haven, Conn., on January 8.

Brown, Trujillo and Rabinowitz first photographed the new planet with the 48-inch Samuel Oschin Telescope on October 31, 2003. However, the object was so far away that its motion was not detected until they reanalyzed the data in January of this year. In the last seven months, the scientists have been studying the planet to better estimate its size and its motions.

“It’s definitely bigger than Pluto,” said Brown, who is a professor of planetary astronomy.

Scientists can infer the size of a solar system object by its brightness, just as one can infer the size of a faraway light bulb if one knows its wattage. The reflectance of the planet is not yet known. Scientists can not yet tell how much light from the sun is reflected away, but the amount of light the planet reflects puts a lower limit on its size.

“Even if it reflected 100 percent of the light reaching it, it would still be as big as Pluto,” says Brown. “I’d say it’s probably one and a half times the size of Pluto, but we’re not sure yet of the final size.

“We are 100 percent confident that this is the first object bigger than Pluto ever found in the outer solar system,” Brown added.

The size of the planet is limited by observations using NASA’s Spitzer Space Telescope, which has already proved its mettle in studying the heat of dim, faint, faraway objects such as the Kuiper-belt bodies. Because Spitzer is unable to detect the new planet, the overall diameter must be less than 2,000 miles, said Brown.

A name for the new planet has been proposed by the discoverers to the International Astronomical Union, and they are awaiting the decision of this body before announcing the name.

The Jet Propulsion Laboratory manages the Spitzer Space Telescope mission for NASA’s Science Mission Directorate, Washington. Science operations are conducted at the Spitzer Science Center at Caltech. Caltech manages JPL for NASA.

For more information and images see: http://www.nasa.gov/vision/universe/solarsystem/newplanet-072905-images.html

or http://www.astro.caltech.edu/palomarnew/sot.html

For information about NASA and agency programs on the Web, visit:

http://www.nasa.gov/home/index.

Original Source: NASA/JPL News Release

A view of the observatories atop Mount Lemmon’s summit. Image credit: Yvette Cendes. Click to enlarge.
Welcome to the world of astronomy camp. Every year, the University of Arizona astronomy camps host teenagers, adults, and educators from around the world. Taking place on Mount Lemmon, a mountain with numerous astronomical instruments near Tucson, Arizona, the camps allow the participants to become ?guest astronomers? from being housed in the professional astronomers? dormitories to learning how to use the various computer programs. The campers even get to do their own research using telescopes and instruments that would turn most professionals green with envy: a 12? equipped with a CCD camera, a 40? with a photometer, a 60? with an imager, and even a 61? with a spectrometer on nearby Mount Bigelow.

This year, the 2005 Advanced Teen Camp took place for nine days in late June and early July. The campers were diverse: 28 campers evenly divided between male and female, ranging from age 14 to age 18, from sixteen states and one foreign country. Each camper had to write an essay and have a letter of recommendation to be accepted, and all the campers arrived in Tucson excited but nervous about what to expect. ?We want this to be the best week of your life,? said Dr. Don McCarthy, a Steward Observatory astronomer and director of astronomy camp. By the last day, most campers agreed that it had been just that.

Before astronomy camp began, the campers were encouraged to begin brainstorming project ideas for research they would like to conduct during the week. The campers then had two days to refine ideas before they were written as proposals and submitted to the camp?s Telescope Allocation Committee (TAC), which then figured out an observing schedule on each telescope for the remainder of the week. After all the data had been collected and analyzed, the camp culminated on the last day with a miniature conference where each group presented their findings.

The projects that were carried out during astronomy camp varied in incredible amounts and showed just what the campers were interested in from imaging galaxies to finding the properties of planetary nebulae. One group was on the 61? every night taking data from quasars, which yielded things such as the distance and velocity of each object after careful calculation. Another group, which became all too painfully aware that astronomy is filled with problems, went through three different types of instrumentation before finally getting usable data on an asteroid?s light curve.

The campers even made observations that contributed to cutting edge astronomical research. Armed with the imaging capabilities of the 60? and the help of the Catalina Sky Survey, the campers tracked the movements for several Kuiper Belt Objects (KBOs) and conducted a search for Near Earth Objects (NEOs). The KBO group was successful in tracking the KBOs and even recovered a previously lost object. The NEO group topped even that: after ?blinking? several hundred images taken of the same parts of the sky at various times the group not only recovered several lost NEOs but discovered a completely new one themselves! The newly discovered asteroid, 2005 MG5, was discovered on the nearest point of its orbit to Earth, and was followed up on by several other observatories around the world. Not bad for a few teenagers still in high school!

When not observing or sleeping off the effects of staying up all night (to the excitement of any teenager, the campers did not have to wake before noon) the days were filled with lectures on various astronomical topics from the camp counselors on everything from the properties of reflecting telescopes to the Deep Impact mission. There was also time to observe our nearest star, the Sun, through numerous safe ways including pinhole projection and through a hydrogen alpha filter. The days were rounded off with other interesting activities, such as watching astronomy-related Simpsons episodes and numerous chess duels.

In the middle of camp, there was a break from the usual schedule for an overnight trip to Mount Graham International Observatory, which houses the Large Binocular Telescope (LBT), the Sub-Millimeter Telescope (SMT), and the Vatican Observatory (jokingly referred to as the ?pope scope?). This caused great excitement among the campers for good reason: the LBT will become the largest telescope in the world upon completion with its twin 8.4m mirrors, the first of which saw first light in 2004. Not only did the campers sleep in the telescope building, they got to see the building open up at sunset! To top it off, the campers had the opportunity to use the SMT telescope, observing various objects throughout the night in radio wavelengths not available on Mount Lemmon.

Before the campers knew it, it was the last day of camp and graduation was being held in downtown Tucson in the additional company of camper relatives. While handing out the certificates, however, the campers were roasted a little by the counselors, who singled out campers for everything from ?The Falsetto Award? to ?Greatest Fruit Lover? and ?Best Impersonation of Spock.? After numerous hugs all around and sorrowful goodbyes, the campers left for homes scattered around the globe. Would there be another reunion sometime in the future? It is likely: down the line most campers end up in the most top-notch universities, and many continue on in similar engineering and science fields. Not surprisingly, many even go on to become the next generation of astronomers, citing their week in Arizona as the primary inspiration in their decision.

What does the future hold for astronomy camp? It appears the program will soon be expanding: numerous plans are in the works for Mount Lemmon, including a brand-new 2.4 meter telescope exclusively for camp use. In the world of astronomy camp, the sky is truly the limit.

Visit the Astronomy Camp website

Written by Yvette Cendes

Ultra-violet image of the hidden spiral arms of NGC 4625. Image credit: NASA/JPL/Caltech. Click to enlarge
A new image from NASA’s Galaxy Evolution Explorer shows that a galaxy once thought to be rather plain and old is actually endowed with a gorgeous set of young spiral arms.

The unusual galaxy, called NGC 4625, is a remarkable find because it is relatively nearby. Until now, astronomers had thought that this kind of youthful glow in galaxies was a thing of the past.

“This galaxy is an amazing surprise,” said Dr. Armando Gil de Paz of the Carnegie Observatories, Pasadena, Calif., lead author of a paper appearing in the July issue of Astrophysical Journal Letters. “We are practically up-close and personal with a galaxy undergoing an evolutionary stage that was thought to occur only at the dawn of the universe, in very young and faraway galaxies.”

The image can be found at http://www.nasa.gov/centers/jpl/missions/galex.html or http://www.galex.caltech.edu/ . It offers astronomers their best look yet at what our Milky Way galaxy might have looked like in earlier times.

“We do not fully understand how stars were created in our galaxy,” said Dr. Barry Madore of the Carnegie Observatories, co-author of the new paper. “This nearby galaxy represents one of our possible histories, in which stars developed first in the galaxy core and then later in the arms.”

Previous visible-light images of NGC 4625 showed only an oval-shaped ball of light, with very faint hints of a halo of spiral arms. These arms were finally revealed to the ultraviolet eyes of the Galaxy Evolution Explorer. Their intense brightness indicates that the arms are teeming with hot, newborn stars, which shine primarily with ultraviolet light.

“The stars in the arms are about one billion years old, while the stars in the body are about ten times older,” said Gil de Paz.

NGC 4625’s spiral arms are very lengthy, extending four times beyond the size of the core of the galaxy. They represent the largest ultraviolet galactic disk discovered so far.

Also of interest in the new Galaxy Evolution Explorer image is a nearby companion galaxy, which looks very similar to NGC 4625, yet has no arms. How could this galactic duo have turned out so differently? Astronomers do not know, but some theories hold that the presence of the armless galaxy was required for NGC 4625 to grow a set.

“We know that interactions between galaxies can spur the creation of stars, but it is not clear why only one galaxy ended up with arms,” said Dr. Chris Martin of the California Institute of Technology in Pasadena, Calif, principal investigator for the Galaxy Evolution Explorer.

Previous studies of the gas distribution around the two galaxies indicate that NGC 4625 might have developed in a more dynamically stable environment, while the armless galaxy grew up in a more chaotic and turbulent setting.

Other authors of this paper include: Dr. S. Boissier, Carnegie Observatories; Dr. R. Swaters, University of Maryland, College Park; Dr. R. J. Tuffs, Max Planck Institut fur Kernphysik, Germany; Dr. K. Sheth, Caltech; Dr. R.C. Kennicutt, University of Arizona, Tucson; Drs. L. Bianchi and D. Thilker, Johns Hopkins University, Baltimore, Md.

Caltech leads the Galaxy Evolution Explorer mission and is responsible for science operations and data analysis. NASA’s Jet Propulsion Laboratory, Pasadena, Calif., manages the mission and built the science instrument. The mission was developed under NASA’s Explorers Program managed by the Goddard Space Flight Center, Greenbelt, Md. South Korea and France are the international partners in the mission.

For images and information about the Galaxy Evolution Explorer on the Internet, visit http://www.galex.caltech.edu/ .

Original Source: NASA News Release

UV image of supernova in spiral galaxy M100. Image credit: ESA/NASA/Immer et al. Click to enlarge
Scientists have found that a star that exploded in 1979 is as bright today in X-ray light as it was when it was discovered years ago, a surprise finding because such objects usually fade significantly after only a few months.

Using ESA?s XMM-Newton space observatory, a team of astronomers has discovered that this supernova, called SN 1979C, shows no sign of fading. The scientists can document a unique history of the star, both before and after the explosion, by studying rings of light left over from the blast, similar to counting rings in a tree trunk.
?This 25-year-old candle in the night has allowed us to study aspects of a star explosion never before seen in such detail,? said Dr Stefan Immler, leader of the team, from NASA?s Goddard Space Flight Center, USA. ?All the important information that usually fades away in a couple of months is still there.?

Among the many unique finds is the history of the star?s stellar wind dating back 16 000 years before the explosion. Such a history is not even known about our Sun. Also, the scientists could measure the density of the material around the star, another first. The lingering mystery, though, is how this star could fade away in visible light yet remain so radiant in X-rays.

Without fuel and thus energy to support their gravity, such stars first implode. The core reaches a critical density, and much of the collapsing matter gets bounced back out violently into space by powerful shockwaves.

Supernovae can outshine an entire galaxy and are often easily seen in neighbouring galaxies with simple amateur telescopes. Supernovae are typically half as bright after about ten days and fade steadily after that, regardless of the wavelength.

SN 1979C has in fact faded in optical light by a factor of 250 becoming barely visible with a good amateur telescope. In X-rays, however, this supernova is still the brightest object in its host galaxy, M100, in the constellation ?Coma Berenices?.

In identifying the history of the star that created SN 1979C, the team found that this star, about 18 times more massive than our Sun, produced fierce stellar winds. That material was flung into space for millions of years, creating concentric rings around the star.

The X-rays – produced after the explosion when the supernova shock caught up with the stellar wind and heated it to a temperature of several million degrees – illuminated 16 000 years? worth of stellar activity.

?We can use the X-ray light from SN 1979C as a ?time machine? to study the life of a dead star long before it exploded,? said Immler.

The detailed analysis was only possible because SN 1979C has not yet faded away. Scientists have 25 years? worth of data in a variety of wavelengths, from radio waves through to optical/ultraviolet and X-rays. They speculate that the abundance of stellar wind has provided ample material to keep SN 1979C glowing so brightly.

The team also captured a rare glimpse of the ultraviolet radiation from the supernova using XMM-Newton. The ultraviolet image independently confirms what the X-ray analysis found: that the circumstellar material ? covering a region 25 times larger than our Solar System – has a relatively high density of 10 000 atoms per cubic centimetre, or about 1000 times denser than the wind from our Sun. The ultraviolet image also shows galaxy M100 in detail never seen before.

?XMM-Newton is known among scientists as a superior X-ray observatory, but the study of SN 1979 demonstrates the importance of the satellite’s simultaneously observing ultraviolet and optical telescope,? said Dr Norbert Schartel, XMM-Newton Project Scientist at ESA’s European Space Astronomy Centre (ESAC) in Spain.

Original Source: ESA Portal