Astronomy Archives

May 4, 2009December 24, 2015 by Fraser Cain

Quasars

When astronomers first started using radio telescopes in the 1950s to study the Universe, they discovered a strange phenomenon. They found objects that shone brightly in the radio spectrum, but they couldn’t see any visible object associated with them. They called them quasi-stellar radio sources, or “quasars” for short.

Within a decade of their discovery, astronomers learned that these quasars were moving away at tremendous velocities. This velocity, or red-shift of their light, indicated that they were billions of light-years away; beyond the capabilities of most optical telescopes. It wasn’t until the 1960s when a quasar was finally tied to an optical object, a distant galaxy.

Since then, thousands of quasars have been discovered, but astronomers had no idea what they were. Finally in the 1980s, astronomers developed unified models that identified quasars as active galaxies. The bright radiation coming from them is because of the accretion disks surrounding the supermassive black holes at their centers. We see a quasar when a supermassive black hole is actively feeding on the surrounding material.

Since our own Milky Way has a supermassive black hole, it’s likely that we have gone through many active stages, whenever material is falling into the black hole; our galaxy would be seen as a quasar. But other times, like now, the supermassive black hole is quiet.

With new powerful telescopes, astronomers have observed that some quasars have long jets of material firing out from the center of the galaxy. These are channeled by the magnetic fields created by the supermassive black hole’s rotation in the accretion disk. The most luminous quasars can exceed the radiation output of an average quasar.

We have written many articles about quasars for Universe Today. Here’s an article about the first triple quasar ever found, and some hidden quasars… found!

If you’d like more info on galaxies, check out Hubblesite’s News Releases on Galaxies, and here’s NASA’s Science Page on Galaxies.

We have also recorded an episode of Astronomy Cast about galaxies – Episode 97: Galaxies.

May 2, 2009December 24, 2015 by Fraser Cain

Galaxy Pictures

Spiral galaxy M101. Image credit: Hubble

The best photographs captured from ground and the Hubble Space Telescopes. I could look at pictures of beautiful spiral galaxies all day. So let’s take a look at some of the most beautiful galaxy photos ever taken.

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This is a classic picture of the spiral galaxy M101, captured by the Hubble Space Telescope. Since this galaxy is seen almost face-on, it allows astronomers to see what a large spiral galaxy, like our own Milky Way, looks like. M101 is located in the constellation of Ursa Major and measures 170,000 light-years across; twice the diameter of the Milky Way.

This is the Andromeda Galaxy, also known as M31. It’s the closest large galaxy to the Milky Way; in fact, Andromeda is currently on a collision course with the Milky Way, and will collide with us in about 10 billion years. After that, the two galaxies will collect together into an enormous irregular galaxy, and our supermassive black holes will merge together.

Andromeda galaxy photo. Image credit: Spitzer

Here’s another Andromeda galaxy picture, but this time captured in the infrared spectrum by the Spitzer Space Telescope. By seeing Andromeda in infrared, astronomers can see regions that would normally be obscured by dust, like new star forming regions, or the center of the galaxy.

This is a photo of galaxy M81 captured by the Hubble Space Telescope. This is another example of a grand spiral galaxy, seen from a bit of an angle. This galaxy is located 11.6 million light-years away in the constellation Ursa Major.

Here’s a picture of the galaxy Centaurus A, located in the constellation of the same name. The huge sprays of material above and below the galaxy demonstrate the power of the supermassive black hole located at the heart of the galaxy. The jets of material extend more than 13,000 light-years away from the center of the galaxy.

If you’d like more info on galaxies, check out Hubblesite’s News Releases on Galaxies, and here’s NASA’s Science Page on Galaxies.

We have also recorded an episode of Astronomy Cast about galaxies – Episode 97: Galaxies.

May 1, 2009December 24, 2015 by Fraser Cain

Spiral Galaxy

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When you think of a galaxy, you’re probably thinking of a spiral galaxy. You know, with the central bulge and grand sweeping arms that spiral outward from the center. In fact, our own Milky Way is a spiral galaxy, and there are many others out there in the Universe. But have you ever thought about how they form in such a beautiful shape?

A spiral galaxy is shaped like a flat disk with a thicker bulge in the center. Bright spiral arms start from the center and then coil outward like a pinwheel. All spiral galaxies rotate, but very slowly; our own Milky Way completes a single revolution once every 250 million years or so.

The spiral arms are actually density waves that move around the disk of the spiral galaxy. As the density wave passes over a region, masses are pulled together, and you get bright pockets of star formation. Then the density wave moves on, and encourages another region to begin star formation.

The central bulge at the center of a spiral galaxy contains older stars, similar to an elliptical galaxy. And at the very center, there’s always a supermassive black hole containing millions of times the mass of the Sun.

Spiral galaxies are also surrounded by a vast spheroidal halo of stars. These stars might not have formed in the galaxy, but were stolen through successive mergers with other galaxies. This galactic halo also contains many globular star clusters.

Astronomers think that spiral galaxies are slowly built over time through the merger of smaller galaxies. As these tiny galaxies came together, their total momentum set the merged galaxy spinning. This spin flattened out the galaxy and set the spiral arms in motion.

We have written many articles about the galaxies for Universe Today. Here’s an article with twin spiral galaxies interacting, and here’s spiral galaxy NGC 2403.

If you’d like more info on galaxies, check out Hubblesite’s News Releases on Galaxies, and here’s NASA’s Science Page on Galaxies.

We have also recorded an episode of Astronomy Cast about galaxies – Episode 97: Galaxies.

May 1, 2009December 24, 2015 by Tammy Plotner

Weekend SkyWatcher’s Forecast – May 1-3, 2009

Greetings, fellow StarGazers! Let’s start the weekend off right by taking on a lunar club challenge and then kicking back to enjoy yet another spring meteor shower! (After all, if April showers bring May flowers, you do know what May flowers bring, don’t you? That’s right… Pilgrims!) Now that I’ve got you at least smiling, take out your binoculars, too… Because there’s two asteroids that are ripe for plucking – Hebe and Ceres. If you feel like being a little more serious about your lunar studies, why not do a little photographic map work? Just match the picture to what you see in the eyepiece and log your studies! Are you ready? Then I’ll see you in the back yard…

Friday, May 1, 2009 – This date is a rather special one in history. In 1543 on this date, Copernicus published and distributed the ‘‘ The Little Commentary ,’’ which described his heliocentric beliefs. In 1949, Gerard Kuiper discovered Nereid, a 150-kilometer-wide satellite of Neptune. It’s so distant from the planet that it requires almost one Earth year (360 days) to complete an orbit! At magnitude 18.7, Nereid is beyond the detection point of most average telescopes but can be ‘‘seen’’ using long exposure charge coupled AQ1 device (CCD) image stacking devices. Other sights that can’t be seen are the Van Allen Radiation Belts of our Earth, the discovery of which was announced in 1958 in this day’s copy of the Washington Evening Star. Thanks to James A. Van Allen’s use of the data from the Explorer I and Pioneer III space probes, we know that Earth’s magnetosphere contains concentrations of electrically charged particles. Say Happy Birthday to American astronaut M. Scott Carpenter, who was born on this date in 1925 and was one of the original seven Mercury astronauts to reach space in 1962.

Tonight’s outstanding lunar feature will be crater Maurolycus , just southwest of the three rings of Theophilus, Cyrillus, and Catharina. This Lunar Club Challenge spans 114 kilometers and goes below the lunar surface by 4,730 meters. Be sure to look for Gemma Frisius just to its north!

Now, relax and enjoy the peak of the Phi Bootid meteor shower, whose radiant is near the constellation Hercules. The best time to view most meteor showers is around 2:00 a.m. local time, but you may have good success watching for these meteors as soon as the Moon westers. The average fall rate is only about 6 per hour, but it’s a great way to spend a spring evening out under the stars!

Saturday, May 2, 2009 – Today, let’s start with the 1868 birth on this date of Robert Williams Wood. Although Wood’s primary research was on sound waves, he devised a ‘‘zone plate’’ that could replace the objective lens of a telescope! He also improved the diffraction grating, did research in spectroscopy, and made photographs showing both infrared and ultraviolet radiations. Also, take a moment to note the 1925 passing of the star cataloger, Johann Palisa. Palisa remains the most successful visual discoverer in the history of minor planet research, discovering 122 asteroids with a 600 telescope and no photographic plates!

Why not salute his achievements by looking for the asteroid Hebe, which reaches opposition tonight? Hebe is the 13th largest asteroid by mass and the 5th brightest to observe. If you collect meteorites and have an H chondrite, chances are good you have a physical piece of Hebe, since it is thought to have contributed up to 40% of all recovered chrondites! Hebe is now coming in at 6th magnitude and given its prime location shouldn’t make it fairly easy for even those with just binoculars to find this cool asteroid.

Now, let’s have a look at the Moon! Tonight’s challenges are craters Cassini and Cassini A, which come into view just south of the black slash of the Alpine Valley. The major crater spans 57 kilometers and reaches a floor depth of 1,240 meters. Your assignment, should you decide to accept it, is to spot the central crater A. It only spans 17 kilometers, yet drops down another 2,830 meters below the primary crater’s floor!

Sunday, May 3, 2009 – How about starting the day with the bizarre and unusual? In 1375 BC, the oldest recorded total solar eclipse occurred—if we can believe eighth century Babylonian records! If you have a green laser pointer, or a telrad, you might want to wish Alfred Kastler a happy birthday. Born on this date in 1902, the physicist was very interested in what happened to atoms when excited by light or radio waves. Kastler developed a method called ‘‘optical pumping,’’ where atoms enter a higher energy state. Optical pumping is what makes your laser work!

Tonight notice just how close bright Regulus is to the Moon! If you’d like to try your hand at asteroid Ceres, you’ll find it approximately another 15 degrees north of the ‘‘Little King.’’

Tonight let’s take a long Moonwalk together and do some major crater exploration. Try using mid-range magnification in your telescope and see how many of the craters in this photograph you can identify!.

Ptolemaeus area: (1) Sinus Asperitatis, (2) Theophilus, (3) Cyrillus, (4) Catharina, (5) Rupes Altai, (6) Piccolomini, (7) Sacrobosco, (8) Abulfeda, (9) Almanon, (10) Taylor, (11) Abenezra, (12) Apianus (13) Playfair, (14) Aliacensis, (15) Werner, (16) Blanchinus, (17) Lacaille, (18) Walter, (19) Regiomontanus, (20) Purbach, (21) Thebit, (22) Arzachel, (23) Alphonsus, (24) Ptolemaeus, and (25) Albategnius.

Until next week? Ask for the Moon… But keep on reaching for the stars!

This week’s awesome images are (in order of appearance): M. Scott Carpenter (credit—NASA), Maurolycus (credit—Alan Chu), Johann Palisa (historical image), Hebe Chart (Your Sky), Cassini (credit—Wes Higgins), Alfred Kastler (historical image) and the Ptolemaeus area (credit—Greg Konkel). We thank you so much!

May 1, 2009December 24, 2015 by Anne Minard

Cosmic Rays too Wimpy to Influence Climate

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People looking for new ways to explain climate change on Earth have sometimes turned to cosmic rays, showers of atomic nuclei that emanate from the Sun and other sources in the cosmos.

But new research, in press in the journal Geophysical Research Letters, says cosmic rays are puny compared to other climatic influences, including greenhouse gases — and not likely to impact Earth’s climate much.

Jeffrey Pierce and Peter Adams of Carnegie Mellon University in Pittsburgh, Pennsylvania, point out that cycles in numerous climate phenomena, including tropospheric and stratospheric temperatures, sea-surface temperatures, sea-level pressure, and low level cloud cover have been observed to correlate with the 11-year solar cycle.

However, variation in the Sun’s brightness alone isn’t enough to explain the effects and scientists have speculated for years that cosmic rays could fill the gap.

For example, Henrick Svensmark, a solar researcher at the Danish Space Research Institute, has proposed numerous times, most recently in 2007, that solar cosmic rays can seed clouds on Earth – and he’s seen indications that periods of intense cosmic ray bombardment have yeilded stormy weather patterns in the past.

Others have disagreed.

“Dust and aerosols give us much quicker ways of producing clouds than cosmic rays,” said Mike Lockwood, a solar terrestrial physicist at Southampton University in the UK. “It could be real, but I think it will be very limited in scope.”

To address the debate, Pierce and Adams ran computer simulations using cosmic-ray fluctuations common over the 11-year solar cycle.

“In our simulations, changes in [cloud condensation nuclei concentrations] from changes in cosmic rays during a solar cycle are two orders of magnitude too small to account for the observed changes in cloud properties,” they write, “consequently, we conclude that the hypothesized effect is too small to play a significant role in current climate change.”

The results have met a mixed reception so far with other experts, according to an article in this week’s issue of the journal Science: Jan Kazil of the University of Colorado at Boulder has reported results from a different set of models, confirming that cosmic rays’ influence is similarly weak. But at least one researcher — Fangqun Yu of the University at Albany in New York — has questioned the soundness of Pierce and Adams’ simulations.

And so, the debate isn’t over yet …

Sources: The original paper (available for registered AGU users here) and a news article in the May 1 issue of the journal Science. See links to some of Svensmark’s papers here.

May 1, 2009April 26, 2016 by Nancy Atkinson

A Stunning Look at “The Big Picture”

My friend Carolyn Collins Petersen, a.k.a. The Spacewriter, has just started a new gig with Astrocast.tv. She now has a regular monthly show called “The Astronomer’s Universe.” Her first episode aired today, and it features “The Big Picture,” an image from the Palomar-Quest digital sky survey. It shows the Virgo Cluster of galaxies, and is something akin to the Hubble Deep Field image. Carolyn’s webcast is a stunning and beautiful look at this amazing part of our night sky, and with wonderful background music and Carolyn’s great voice, (can’t find enough superlatives!) this is must-see TV! Thanks to Carolyn and Astrocast.tv for sharing the video.
Continue reading “A Stunning Look at “The Big Picture””

April 30, 2009December 24, 2015 by Fraser Cain

Galaxies

Hello, is there anyone out there? With all of the galaxies in the Universe, is it possible that there is cognizant life somewhere else? Well, I can not answer that question for you, but I can offer you a great deal of information about galaxies so that you can make your own informed decision on the matter.

Our’s is a spiral galaxy. A spiral galaxy is shaped like a flat disk with a thicker bulge in the center. Bright spiral arms start from the center and then coil outward like a pinwheel. All spirals rotate very slowly. The Milky Way completes a single revolution once every 250 million years.

Most galaxies are billions of years old. The youngest known galaxy is 1 Zwicky 18. At an estimated age of a mere 500 million years, it is a babe in diapers compared to the Milky Way at 10-14 billion years, which is the average age of the known galaxies.

Scientists think that galaxy formation was led by dark matter. This invisible material clumped together and it attracted regular mass with its gravity, channeling material together into larger and larger collections. This process of matter accretion led to the first proto-galaxies.

The Canis Major Dwarf Galaxy is the closest galaxy to ours. It is actually contained within the Milky Way and only 42,000 light years form the galactic core.

In the links below you will find thousands of facts, figures, and images that will help you understand many things about galaxies in general and some specific types. Enjoy your reading.

April 29, 2009December 24, 2015 by Nancy Atkinson

Confirmed: Chocolate and Astronomy Go Together

Chocolate astronomy sculpture. Credit: Museo de Chocolate.

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Two of my greatest loves are coming together at the Museo de Chocolate (Chocolate Museum) of Barcelona. To celebrate the International Year of Astronomy 2009, this year’s International Contest of Chocolate Figures has chosen astronomy as its theme. And the fourteen sculptures that are part of the competition –in which the designers use chocolate to embody creative astronomical interpretations, as the one seen here — will be on display at the Museo de Chocolate starting on May 7 in a new temporary exhibition, “Los Mundos Celestes-400 años del descubrimiento del sistema solar” (Celestial Worlds – 400 years since the discovery of the Solar System). I understand the exhibition as being temporary, but my question is, who gets to eat them?

Source: Pasteleria.com

April 29, 2009December 24, 2015 by Anne Minard

Nearsighted No More: Astronomers Resolve Milky Way’s Mysterious X-Ray Glow

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The map above details the Galactic ridge X-ray emission, first detected 25 years ago and observed recently by NASA’s Rossi X-ray Timing Explorer (RXTE) observatory. The inset shows the zoomed Chandra image of the region, close to the center of the galaxy.

The mysterious — and formerly blurry — X-ray source puzzled astronomers for a quarter century, but a new paper release today by the journal Nature has helped to clear the air.

spitzer_region — Region close to the Galactic Center obtained by Spitzer infrared telescope in three spectral band. The field of view of CHANDRA is shown by the white square. Credit: M. Revnivtsev

Lead author Mikhail Revnivtsev, of Munich Technical University in Garching, Germany, and his colleagues report that the formerly unresolved X-ray glow has a spectrum characteristic of a hot (100 million degrees Kelvin) optically thin plasma, with a prominent iron emission line.

But the gravitational well of the Galactic disk is far too shallow to confine such a hot interstellar medium; it would flow away at a velocity of a few thousand kilometers per second, exceeding the speed of sound in the gas.

Replenishing such energy losses would require a source that exceeds all plausible energy sources in the Milky Way — including supernovae — by orders of magnitude, they write.

Based on their observations, the team is proposing that the hot plasma is instead bound to many faint sources: plain old stars.

“Here we report that at energies of 6–7 keV, more than 80 percent of the seemingly diffuse X-ray emission is resolved into discrete sources, probably accreting white dwarfs and coronally active stars,” they write.

“Such stellar X-ray sources are of the common ‘garden variety’ in the Sun’s neighbourhood,” writes Michael Shull, an astrophysicist at the University of Colorado at Boulder, in an accompanying editorial. “However, at the distance of the Galactic ridge from Earth, their combined light becomes a diffuse blur, the X-ray equivalent of the many stars that make up the Milky Way, as Galileo first saw with his telescope in visible light.”

Shull notes that the results are a testament to the increased power of telescopes like Chandra, which de-mystified the source of the X-ray glow — and he cautions astronomers about describing faint backgrounds at all wavelengths, before getting a good look.

“As Revnivtsev and colleagues’ work demonstrates, sometimes the exotic explanation can be set aside by more accurate imaging and spectroscopy,” he writes.

LOWER IMAGE CAPTION: Region close to the Galactic Center obtained by Spitzer infrared telescope in three spectral band. The field of view of CHANDRA is shown by the white square. Credit: M. Revnivtsev

Source: Nature

April 28, 2009December 24, 2015 by Tammy Plotner

In Your Eyes – The NGC 4486 Jet by JP Metsavainio

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We’re all familiar with the photo of the jet of material emanating from the core of the Virgo A galaxy as imaged by the Hubble Space Telescope, but this 5,000 light year long streamer coming from the nucleus of M87 has never been more “in your eyes” than it is through the stereo magic visualizations produced by Jukka Metsavainio. Are you ready to take a closer look at this relativistic jet of extremely powerful plasma emerging from one of the best studied radio galaxies around? Then step inside…

Whenever we present a dimensional visualization it is done in two fashions. The first is called “Parallel Vision” and it is much like a magic eye puzzle. When you open the full size image and your eyes are the correct distance from the screen, the images will seem to merge and create a 3D effect. However, for some folks, this doesn’t work well – so Jukka has also created the “Cross Version”, where you simply cross your eyes and the images will merge, creating a central image which appears 3D. As we learned with the last image, it might not always work for all people, but there are a few other tricks you can try. Now sit back and prepare to be blown away…

The year is 1918, and high on top of Mt. Hamilton at Lick Observatory an astronomer named Herbert Curtis is busy studying Messier Object 87. But, Mr. Curtis isn’t your ordinary garden-variety astronomer. In just two more years, he and a man named Harlow Shapely were going to have it out publicly about the nature of these “distant fuzzies” and Curtis was going to be eventually proved correct: Spiral “nebulae” were indeed galaxies just like our own. However, good old Herbert was noticing something about M87 that would take nearly 8 decades to discover its true nature… a “curious straight ray” coming straight from its heart. Now, you’ve got to give Herbert some very big credit for being an astute visual observer, because this was back in the day long before wide field imaging camera, infra-red technology, x-ray photography, radio studies and more. Heck, it would be 2 more years before Hubble began identifying Cepheid variables and 10 more years before interstellar absorption was discovered!

Are you ready to fast forward to 1977? Because it would be about that long before another noble name in galaxy studies would again reveal astonishing visual things about M87’s jet by resolving knots and clouds – Halton C. Arp of Mt. Palomar and J. Lorre of JPL. “The shred itself, however, is the object of most significance for establishing the reality of the ejection of the radio source. It is difficult to make a quantitative statement, but objects of this nature are not frequently seen. The inference is plain that the radio source has either left a wake behind it, (i.e. condensations along its track) or that this is some kind of jet or material associated with the ejection of the radio source form the parent peculiar galaxy.”

It wasn’t long until the discovery of a disk of rapidly rotating gas around the nucleus of M87 occurred and thanks to the Hubble Space telescope, we were taking closer than ever looks into the violent active nucleus of this galaxy. “We see almost a dozen clouds which appear to be moving out from the galaxy’s center at between four and six times the speed of light. These are all located in a narrow jet of gas streaming out from the region of the black hole at the galaxy’s center,” said Dr. John Biretta of the Space Telescope Science Institute. “We believe this apparent speed translates into an actual velocity just slightly below that of light itself.”

What we know now is the jet in M87 connects the innermost black hole to the outer parts of the source. It supplies the radio source and the surrounding region with energy and relativistic plasma. The speeds reported are two to three times faster than the fastest motions previously recorded in M87, the only nearby galaxy to show evidence for superluminal motion. “This discovery goes a long way towards confirming that radio galaxies, quasars and exotic BL Lac objects are basically the same beast, powered by super massive black holes, and differ only in orientation with respect to the observer,” Biretta said.

And this time the orientation is right in your eyes…

Many thanks to JP Metsavainio of Northern Galactic for his magic with Hubble Space Telescope images and allowing us this incredible look inside another mystery of space.