Astronomy Archives

August 21, 2009December 24, 2015 by John Carl Villanueva

Interesting Facts About the Universe

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So you think you know your universe? We’ve got our own top 10 list on the most interesting facts about the Universe.

1. It was hot when it was young

The most widely accepted cosmological model is that of the Big Bang. This was proven since the discovery of the cosmic microwave background radiation or CMBR. Although, strictly speaking, no one knows exactly what ‘banged’, we know from extrapolation that the Universe was infinitely hot at birth, cooling down as it expanded.

In fact, even only within minutes of expansion, scientists predict its temperature to have been about a billion Kelvin. Moving backward to 1 second, it is said to have been at 10 billion Kelvin. For comparison, today’s universe is found to have an average temperature of only 2.725 Kelvin.

2. It will be cold when it grows old

Observations made especially on galaxies farthest from us show that the Universe is expanding at an accelerated rate. This, and data that show that the Universe is cooling allows us to believe that the most probable ending for our universe is that of a Big Freeze.

That is, it will be devoid of any usable heat (energy). It is due to this prediction that the Big Freeze is also known as the Heat Death.Accurate measurements made by the Wilkinson Microwave Anisotropy Probe (WMAP) on the current geometry and density of the Universe favor such an ending.

3. The Universe spans a diameter of over 150 billion light years

Current estimates as with regards to the size of the Universe pegs it at a width of 150 billion light years. Although it may seem peculiarly inconsistent with the age of the Universe, which you’ll read about next, this value is easily understood once you consider the fact that the Universe is expanding at an accelerated rate.

4. The Universe is 13.7 billion years old

If you think that is amazing, perhaps equally remarkable is the fact that we know this to better than 1% precision. Credit goes to the WMAP team for gathering all the information needed to come up with this number. The information is based on measurements made on the CMBR.

Older methods which have contributed to confirming this value include measurements of the abundances of certain radioactive nuclei. Observations made on globular clusters, which contain the oldest stars, have also pointed to values close to this.

5. The Earth is not flat – but the Universe is

Based on Einstein’s Theory of General Relativity, there are three possible shapes that the Universe may take: open, closed, and flat. Once again, measurements by WMAP on the CMBR have revealed a monumental confirmation – the Universe is flat.

Combining this geometry and the idea of an invisible entity known as dark energy coincides with the widely accepted ultimate fate of our universe, which as stated earlier, is a Big Freeze.

6. Large Scale Structures of the Universe

Considering only the largest structures, the Universe is made up of filaments, voids, superclusters, and galaxy groups and clusters. By combining galaxy groups and clusters, we come up with superclusters. Some superclusters in turn form part of walls, which are also parts of filaments.

The vast empty spaces are known as voids. That the Universe is clumped together in certain parts and empty in others is consistent with measurements of the CMBR that show slight variations in temperature during its earliest stages of development.

7. A huge chunk of it is made up of things we can’t see

Different wavelengths in the electromagnetic spectrum such as those of radio waves, infrared, x-rays, and visible light have allowed us to peer into the cosmos and ‘see’ huge portions of it. Unfortunately, an even larger portion cannot be seen by any of these frequencies.

And yet, certain phenomena such as gravitational lensing, temperature distributions, orbital velocities and rotational speeds of galaxies, and all others that are evidence of a missing mass justify their probable existence. Specifically, these observations show that dark matter exists. Another invisible entity known as dark energy, is believed to be the reason why galaxies are speeding away at an accelerated rate.

8. There is no such thing as the Universe’s center

Nope. The earth is not the center of the Universe. It’s not even the center of the galaxy. And no again, our galaxy is not the entire universe, neither is it the center. Don’t hold your breath but the Universe has no center. Every galaxy is expanding away from one another.

9. Its members are in a hurry to be as far away from each other as possible

The members that we are talking about are the galaxies. As mentioned earlier, they are rushing away from each other at increasing rates. In fact, prior to the findings of most recently gathered data, it was believed that the Universe might end in a Big Rip. That is, everything, down to the atoms, would be ripped apart.

This idea stemmed from this observed accelerated rate of expansion. Scientists who supported this radically catastrophic ending believed that this kind of expansion would go on forever, and thus would force everything to be ripped apart.

10. To gain a deeper understanding of it, we need to study structures smaller than the atom

Ever since cosmologists started to trace events backward in time based on the Big Bang model, their views, which focused only on the very large, got smaller and smaller. They knew, that by extrapolating backward, they would be led into a universe that was very hot, very dense, very tiny, and governed by extremely high energies.

These conditions were definitely within the realm of particle physics, or the study of the very small. Hence, the most recent studies of both cosmology and particle physics saw an inevitable marriage between the two.

There you have it. Feel free to come up with a longer list of your own.

Sources:
UT-Knoxville
NASA WMAP
NASA: Age of the Universe
NASA: Shape of the Universe
UCLA: Center of the Universe
Hubblesite: Fate of the Universe

August 21, 2009December 24, 2015 by Tammy Plotner

Weekend SkyWatcher’s Forecast – August 21-23, 2009

Greetings, fellow SkyWatchers! Are you ready for the weekend? Then let’s enjoy the nights ahead as we fly along the Milky Way on the wings of the Swan and hunt down some very different star clusters in the night with the Fox. Do you need a smile? Then you’ll find one with with a delightful asterism called the “Coat Hanger”! How about a Herschel challenge? We’ve got that, too. In the mood to just stargaze? Then stick around – because the Perseid Meteor Shower hasn’t ended just yet. (We’ve got something very special inside here to show you!) Time to get out your telescopes and binoculars and I’ll see you outside…

Friday, August 21, 2009 – On this date in 1993, the Mars Observer was lost. . . But you can’t miss Mars at its peak just before dawn!

Tonight it’s time for us to fly with the ‘‘Swan’’ as the graceful arch of the Milky Way turns overhead. We’ll start by taking a look at a bright star cluster that’s equally great in either binoculars or telescope, M39.

Located about a fist-width northeast of Deneb (Alpha Cygni), you will easily see a couple of dozen stars in a triangular pattern. M39 (RA 21 31 48 Dec +48 27 00) is particularly beautiful because it will seem almost three-dimensional against its backdrop of fainter stars. Younger than the Coma Berenices cluster, and older than the Pleiades, the estimated age of M39 is at least 230 million years. This loose, bright, galactic cluster is around 800 light-years away. Its members are all main sequence stars, and the brightest of them are beginning to evolve into giants.

For more of a challenge, try dropping about a degree south-southwest (RA 21 29 00 Dec +47 08 00) for NGC 7082, also known as H VII.52. Although it is a less rich, less bright, and far less studied open cluster, at magnitude 7.5 NGC 7082 is within range of binoculars and is on many open cluster observing lists. With only a handful of bright stars to NGC 7082’s credit, larger telescopes are needed to resolve out many of the fainter members. Be sure to mark your notes for both objects!

Saturday, August 22, 2009 – Born this date in 1833 was Samuel Pierpont Langley, who investigated the relationship between solar phenomena and meteorology. Is that why we always have clouds when solar activity is at its best?

Tonight we’ll hunt with the ‘‘Fox’’ as we head to Vulpecula to try two more open star cluster studies. The first can be done easily with large binoculars or a low power scope. It’s a rich beauty in the constellation of Vulpecula but is more easily found by moving around 3 degrees southeast of Beta Cygni (RA 19 35 48 Dec +25 13 00).

Known as Stock 1, this stellar swarm contains 50 or so members of varying magnitudes, which you will return to often. With a visual magnitude of near 5, loose associations of stars—like Stock clusters—are the subject of recent research. The latest information indicates that the members of this cluster are truly associated with one another.

A little more than a degree to the northeast is NGC 6815 (RA 19 40 44 Dec +26 45 32). Although NGC 6815 is a slightly more compressed open cluster, it has no real status among deep-sky objects, but it is another one to add to your collection of things to do and see!

Sunday, August 23, 2009 – On this date in 1609, Galileo demonstrated the telescope for the first time. Tonight we’ll aim our own optics at an asterism known as the ‘‘Coat Hanger,’’ which is also known as Brocchi’s Cluster, or Collinder 399. Let the colorful double star Beta Cygni—Albireo—be your guide as you move about 4 degrees to its south-southwest (RA 19 25 24 Dec +20 11 00). You will know this cluster when you see it, because it really does look like a coat hanger!

Enjoy its red stars! Discovered by Al Sufi in 964 AD, this 3.5 magnitude collection of stars was again recorded by Hodierna. Thanks to its extended size of more than 60′ it escaped the catalogs of both Messier and Herschel. Only around a half dozen stars share the same proper motion, which may make it a cluster much like the Pleiades, but studies suggest it is merely an asterism—but one with two binary stars at its heart.

And for larger scopes? Fade east to the last prominent star in the cluster (RA 19 30 36 Dec +20 16 00) and power up. NGC 6802 awaits you! At near magnitude 9, Herschel VI.14 is a well-compressed open cluster of faint members. The subject of ongoing research in stellar evolution, this 100,000-year old cluster is on many observing challenge lists!

Over the weekend, be sure to keep an eye out for stray Perseid meteors, because the show hasn’t ended yet! Although activity has slowed considerably, your chances are above average of catching a bright streak while you’re out enjoying the stars. It was a wonderful year for the Perseids and even if you were clouded out, we’ve still managed to catch the action for you…

Many thanks to John Chumack of Chumack Observatory (Dayton, Ohio) for all of his hard work in capturing and editing the footage from his All Sky Camera from the nights of August 11-14th. He’s trimmed the video to 5 frames per second and within this less than one minute clip, you’ll see over 200 meteors and the Moon rise three times! Were the Perseids a success? You bet. Just as John how he finished his film… “I ended it with the brightest…” said John, “A -8 magnitude fireball!”

Keep looking up! You’ll never know when it might be your lucky night…

This week’s awesome images are (in order of appearance): M39, NGC 7082, Stock 1, NGC 6815 (credit—Palomar Observatory, courtesy of Caltech), Collinder 399 (credit—Gil Estel), NGC 6802 (credit—Palomar Observatory, courtesy of Caltech) and Perseid Meteor Storm Video courtesy of John Chumack. We thank you so much!!

August 19, 2009December 24, 2015 by Nancy Atkinson

New Limits on Gravitational Waves From the Big Bang

Artists concept of graviational waves. Credit: NASA

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The only way to know what the Universe was like at the moment of the Big Bang requires analysis of gravitational waves created when the Universe began. Scientists working with the Laser Interferometer Gravitational-Wave Observatory (LIGO) say their initial investigations of these gravitiation waves have turned up nothing. But that’s a good thing. Not detecting the waves provides constraints about the initial conditions of the universe, and narrows the field of where we actually do need to look in order to find them.

Much like it produced the cosmic microwave background, the Big Bang is believed to have created a flood of gravitational waves — ripples in the fabric of space and time. From our current understanding, gravitational waves are the only known form of information that can reach us undistorted from the beginnings of the Universe. They would be observed as a “stochastic” or random background, and would carry with them information about their violent origins and about the nature of gravity that cannot be obtained by conventional astronomical tools. The existence of the waves was predicted by Albert Einstein in 1916 in his general theory of relativity.

Analysis of data taken over a two-year period, from 2005 to 2007, yields that the stochastic background of gravitational waves has not yet been discovered. But the nondiscovery of the background, described in a new paper in the August 20 Nature, offers its own brand of insight into the universe’s earliest history.

“Since we have not observed the stochastic background, some of these early-universe models that predict a relatively large stochastic background have been ruled out,” said Vuk Mandic, assistant professor at the University of Minnesota and the head of the group that performed the analysis. “We now know a bit more about parameters that describe the evolution of the universe when it was less than one minute old.”

According to Mandic, the new findings constrains models of cosmic strings, objects that are proposed to have been left over from the beginning of the universe and subsequently stretched to enormous lengths by the universe’s expansion; the strings, some cosmologists say, can form loops that produce gravitational waves as they oscillate, decay, and eventually disappear.

“Since we have not observed the stochastic background, some of these early-universe models that predict a relatively large stochastic background have been ruled out,” said Mandic. “If cosmic strings or superstrings exist, their properties must conform with the measurements we made—that is, their properties, such as string tension, are more constrained than before.”

This is interesting, he says, “because such strings could also be so-called fundamental strings, appearing in string-theory models. So our measurement also offers a way of probing string-theory models, which is very rare today.”

The analysis used data collected from the LIGO interferometers in Hanford, Wash., and Livingston, La. Each of the L-shaped interferometers uses a laser split into two beams that travel back and forth down long interferometer arms. The two beams are used to monitor the difference between the two interferometer arm lengths.

The next phase of the project, called Advanced LIGO, will go online in 2014, and be 10 times more sensitive than the current instrument. It will allow scientists to detect cataclysmic events such as black-hole and neutron-star collisions at 10-times-greater distances.

The Nature paper is entitled “An Upper Limit on the Amplitude of Stochastic Gravitational-Wave Background of Cosmological Origin.”

Source: EurekAlert

August 17, 2009December 24, 2015 by Jerry Coffey

Where Do Asteroids Come From?

An artists impression of an asteroid belt. Credit: NASA

[/caption]Where do asteroids come from? Most of them are grouped in the main belt, but that is not the only asteroid field in the solar system. There are actually four sets of asteroids grouped into different fields: the main belt, Trojans, scattered disc, and the Kuiper belt. To understand where do asteroids come from, you need to know the theory on how they were formed.

Most scientists agree that all of the asteroids are the result of the the big bang. After the initial turmoil, large asteroids collided together and through the process known as accretion planets and dwarf planets were formed. The planets and dwarfs grew large enough to develop gravity and became rounded and able to sustain their own gravity. Asteroids continued to collide and destroy each other until we have the elliptical and other odd shaped, pock-marked solar objects that we have today. Here is a little information to help you understand where do asteroids come from today.

The asteroid field known as the main belt is a large collection of objects that are in orbit between Jupiter and Mars. The largest known asteroid in the belt is Ceres which accounts for 27% of the belts’ total mass. Ceres is also the only asteroid in the belt that is classified as a dwarf planet. Vesta, Hygeia, and Pallas are the other of the four largest bodies in the asteroid field. There have been several space missions that have crossed the field. The asteroids are far enough apart that traversing it is easily done. The Dawn space mission to the next to visit the main belt and will visit two of the largest bodies, hopefully it will be able to help reclassify Vesta as a dwarf planet.

The Kuiper belt is populated with thousands of icy bodies. The only one that is currently designated as a dwarf planet is the former planet Pluto. That may change in the near future since there are at least two bodies in the belt that are larger than Pluto. Our ability to send spacecraft that far out is what is holding us back right now.

The Trojans asteroid field, originally referred to the Trojan asteroids, orbits around Jupiter’s 4th and 5th Lagrangian points. Subsequently objects have been found orbiting the same Lagrangian points of Neptune and Mars. The word Trojan, in astronomy, refers to a natural satellite that shares an orbit with a larger planet or moon, but does not collide with it because it orbits around one of the two Lagrangian points of stability.

The scattered disc asteroid field is a subset of the Kuiper belt. Because their orbits take them well beyond 100AU from the Sun they are the coldest objects in the Solar System. Due to its unstable nature, astronomers now consider the scattered disc to be the place of origin for most periodic comets. Many of the objects in the Oort cloud are thought to have originated in the scattered disc.

Answering the question: ”Where do asteroids come from?” is pretty easy, but it is ambiguous at the same time. What we have are mostly theories and few definite facts. Things get even more blurry as you study different asteroids and find that some from different belts have somehow inter-mixed. Ah, the beauty of astronomy!

There is some good info on the asteroid belt here. NASA has a good piece on KBO’s. Here on Universe Today there is an article on the possibility of an alien asteroid belt and the Milky Ways’ own asteroid belts.

Reference:
Wikipedia

August 16, 2009December 24, 2015 by Abby Cessna

Solar System Orbits

Take a look at the Solar System from above, and you can see that the planets make nice circular orbits around the Sun. But dwarf planet’s Pluto’s orbit is very different. It’s highly elliptical, traveling around the Sun in a squashed circle. And Pluto’s orbit is highly inclined, traveling at an angle of 17-degrees. This strange orbit gives Pluto some unusual characteristics, sometimes bringing it within the orbit of Neptune. Credit: NASA

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One of the International Astronomical Union’s (IAU) requirements for a celestial body to be classified as a planet (or a dwarf planet) is that it orbits the Sun. All of the planets have different orbits, which affect many of the planets’ other characteristics.

Since Pluto became a dwarf planet, Mercury is the planet with the most eccentric orbit. The eccentricity of an orbit is the measurement of how different the orbit is from a circular shape. If an orbit is a perfect circle, its eccentricity is zero. As the orbit becomes more elliptical, the eccentricity increases. Mercury’s orbit ranges from 46 million kilometers from the Sun to 70 million kilometers from the Sun.

Venus, which is right next to Mercury, has the least eccentric orbit of any of the planet in the Solar System. Its orbit ranges between 107 million km and 109 million km from the Sun and has an eccentricity of .007 giving it a nearly perfect circle for its orbit.

Earth also has a relatively circular orbit with an eccentricity of .017. Earth has a perihelion of 147 million kilometers; the perihelion is the closest point to the Sun in an object’s orbit. Our planet has an aphelion of 152 million kilometers. An aphelion is the furthest point from the Sun in an object’s orbit.

Mars has one of the most eccentric orbits in our Solar System at .093. Its perihelion is 207 million kilometers, and it has an aphelion of 249 million kilometers.

Jupiter has a perihelion of 741 million kilometers and an aphelion of 778 million kilometers. Its eccentricity is .048. Jupiter takes 11.86 years to orbit the Sun. Although this seems a long time compared to the time our own planet takes to orbit, it is only a fraction of the time of some of the other planets’ orbits.

Saturn is 1.35 billion kilometers at its perihelion and 1.51 billion kilometers from the Sun at its furthest point. It has an eccentricity of .056. Since it was first discovered in 1610, Saturn has only orbited the Sun 13 times because it takes 29.7 years to orbit once.

Uranus is 2.75 billion miles from the Sun at its closest point and 3 billion miles from the Sun at its aphelion. It has an eccentricity of .047 and takes 84.3 years to orbit the Sun. Uranus has such an extreme axial tilt (97.8°) that rotates on its side. This causes radical changes in seasons.

Neptune is the furthest planet from the Sun with a perihelion of 4.45 billion kilometers and an aphelion of 4.55 billion kilometers. It has an eccentricity of .009, which is almost as low as Venus’ eccentricity. It takes Neptune 164.8 years to orbit the Sun.

Universe Today has articles on orbits of the planets and asteroid orbits.

For more information, check out articles on an overview of the Solar System and new planet orbits backwards.

Astronomy Cast has episodes on all the planets including Mercury.

References:
NASA: Transits of Mercury
NASA: Solar System Math
NASA: Mars, You’re So Complicated
NASA Solar System Exploration

August 15, 2009December 24, 2015 by John Carl Villanueva

Structure of the Universe

Galaxy cluster Abell 85, seen by Chandra, left, and a model of the growth of cosmic structure when the Universe was 0.9 billion, 3.2 billion and 13.7 billion years old (now). Credit: Chandra

[/caption]The large-scale structure of the Universe is made up of voids and filaments, that can be broken down into superclusters, clusters, galaxy groups, and subsequently into galaxies. At a relatively smaller scale, we know that galaxies are made up of stars and their constituents, our own Solar System being one of them.

By understanding the hierarchical structure of things, we are able to gain a clearer visualization of the roles each individual component plays and how they fit into the larger picture. For example, if we go down to the world of the very small, we know that molecules can be chopped down into atoms; atoms into protons, electrons, and neutrons; then the protons and neutrons into quarks and so on.

But what about the very large? What is the large-scale structure of the universe? What exactly are superclusters and filaments and voids? Let’s start by looking at galaxy groupings and move on to even larger structures.

Although there are some galaxies that are found to stray away by their lonesome, most of them are actually bundled into groups and clusters. Groups are smaller, usually made up of less than 50 galaxies and can have diameters up to 6 million light-years. In fact, the group in which our Milky Way is a member of is made up of only a little over 40 galaxies.

Generally speaking, clusters are bunches of 50 to 1,000 galaxies that can have diameters of up to 2-10 megaparsecs. One very peculiar property of clusters is that the velocities of their galaxies are supposed to be too high for gravity alone to keep them bunched together … and yet they are.

The idea that dark matter exists starts at this scale of structure. Dark matter is believed to provide the gravitational force that keeps them all bunched up.

A great number of groups, clusters and individual galaxies can come together to form the next larger structure – superclusters. Superclusters are among the largest structures ever to be discovered in the universe.

The largest single structure to be identified is the Sloan Great Wall, a vast sheet of galaxies that span a length of 500 million light-years, a width of 200 million light-years and a thickness of only 15 million light-years.

Due to the limitations of today’s measuring devices, there is a maximum level to which we can zoom out. At that level, we see a universe made up of mainly two components. There are the threadlike structures known as filaments that are made up of isolated galaxies, groups, clusters and superclusters. And then there are vast empty bubbles of empty space called voids.

You can read more about structure of the universe here in Universe Today. Want to read about the cosmic void: could we be in the middle of it? We’ve also written about probing the large scale structure of the universe.

There’s more about it at NASA. Here are a couple of sources there:

Here are two episodes at Astronomy Cast that you might want to check out as well:

Sources: NASA WMAP, NASA: Sheets and Voids

August 14, 2009December 24, 2015 by Tammy Plotner

Weekend SkyWatcher’s Forecast – August 14-16, 2009

Greetings, fellow SkyWatchers! Have you had a wonderful week chasing the Perseid Meteor shower? Well, the show isn’t over yet. Enjoy this weekend’s darker skies and keep watching! While you’re out, why not take a pair of binoculars with you and do a little cluster hunting? If you’re feeling energetic – take out the telescope and resolve them. Who knows what you might learn if you listen to what’s out there… Things like where to find chemically peculiar stars – or a runaway black hole! It’s all waiting for you in the night….

Friday, August 14, 2009 – If you were up well before dawn this morning watching the Perseids, did you notice the Pleiades brushing by the Moon? What a lovely sight! I wonder if it was an occultation event somewhere?

Tonight let’s venture about three finger-widths northeast of Lambda Sagittarii to visit a well known but little visited galactic cluster—M25 (RA 18 31 42 Dec -19 07 00). Discovered by Cheseaux and then cataloged by Messier, it was observed and recorded by William Herschel, Johann Elert Bode, Admiral Smythe, and T.W.Webb but never added to the NGC catalog of John Herschel! Thanks to J.L.E. Dreyer, it did make the second Index Catalog as IC 4725.

M25 is seen even with the slightest optical aid, and this 5th magnitude cluster contains two G-type giants as well as a Delta Cephei-type variable with the designation of U, which changes about 1 magnitude in a period of less than a week. It’s very old for an open cluster, perhaps near 90 million years, and the light you see tonight left the cluster over 2,000 years ago. Although binoculars will see about a double handful of bright stars overlying fainter members, telescopes will reveal more and more as aperture increases. At one time it was believed to have only about 30 members, but this was later revised to 86. But recent studies by Archinal and Hynes indicate it may have as many as 601 member stars!

Saturday, August 15, 2009 – On this date in 2006, Voyager 1, the most distant manmade object, reached 100 astronomical units (AUs) from the Sun—meaning 100 times more distant from the Sun than Earth—about 15,000 million kilometers (9,300 million miles). Voyager 1 continues traveling at a rate of about a million miles per day and could cross into interstellar space within 10 years. What fanastic sights do you think it is seeing?

Tonight we’ll head toward the riches of Scorpius to have a look at three pristine open clusters. Begin your starhop at the colorful southern Zeta pair and head north less than 1 degree for NGC 6231 (RA 16 54 08 Dec -41 49 36).

Wonderfully bright in binoculars and well resolved in the telescope, this tight-open cluster was discovered by Hodierna before 1654. De Cheseaux cataloged it as object 9, Lacaille as II.13, Dunlop as 499, Melotte as 153, and Collinder as 315. No matter what catalog number you choose to put in your notes, you’ll find the 3.2-million-year young cluster shining as the ‘‘Northern Jewelbox!’’ For high power fans, look for the brightest star in this group, called van den Bos 1833, a
splendid binary.

About another degree north is the loose open cluster Collinder 316, with its stars scattered widely across the sky. Caught on its eastern edge is another cluster known as Trumpler 24, a site where new variables might be found. This entire region is encased in a faint emission nebula called IC 4628, making this low-power journey through southern Scorpius a red-hot summer treat!

Sunday, August 16, 2009 – Before dawn, look for the close pair of Mars and the Moon celebrating the 1744 birth on this date of Pierre Mechain! We know Mechain as Charles Messier’s assistant, but Mechain was himself a fine astronomer and mathematical prodigy. He discovered 11 comets, and provided 26 entries to Messier’s catalog. If he were alive today, Pierre would be eager to join us tonight for our studies.

Begin about a degree and a half south of twin Nu Scorpii for NGC 6242 (RA 16 55 36 Dec -39 28 00).

Discovered by Lacaille and cataloged as I.4, this object is also known as Dunlop 520, Melotte 155, and Collinder 317. At roughly magnitude 6, this open cluster is within binocular range but truly needs a telescope to appreciate its fainter stars. Although NGC 6242 might seem like nothing more than a pretty little cluster with a bright double star, it contains an X-ray binary that is a ‘‘runaway’’ black hole, surmised to have formed near the galactic center and vaulted into an eccentric orbit when the progenitor star exploded. Its kinetic energy is much like that of a neutron star or a millisecond pulsar, and it was the first black hole confirmed to be in motion.

Now head a little more than a degree east-southeast for NGC 6268 (RA 17 02 40 Dec -39 44 18).

At a rough magnitude of 9, this small open cluster can be easily observed in smaller scopes and resolved in larger ones. NGC 6268 itself is somewhat lopsided, with more of its members clustered near its western border. Although it, too, might not seem particularly interesting, this young cluster is highly evolved and contains some magnetic, chemically peculiar stars; it has some Be-class, or metal weak, members as well.

Until next week? Keep on yelling when the Perseids fly over! I’m sure St. Lawrence would approve…

This week’s awesome images are (in order of appearance): M25 (credit—Palomar Observatory, courtesy of Caltech), Voyager 1 (credit—NASA), NGC 6231, NGC 6242 and NGC 6268 (credit—Palomar Observatory, courtesy of Caltech). We thank you so much!

August 14, 2009December 24, 2015 by Nancy Atkinson

Found: Planetary Nebula Around Heavy Stars

An optical image from the 0.6-m University of Michigan/CTIO Curtis Schmidt telescope of the brightest Radio Planetary Nebula in the Small Magellanic Cloud, JD 04. The inset box shows a portion of this image overlaid with radio contours from the Australia Telescope Compact Array. The planetary nebula is a glowing record of the final death throes of the star. (Optical images are courtesy of the Magellanic Cloud Emission Line Survey (MCELS) team).

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Planetary nebula – the glowing gaseous shells thrown off by stars during the latter stages of their evolution – were thought to only form around stars the size of our Sun or smaller. Although astronomers had predicted these shells should form around “heavier” stars, none had ever been detected. Until now. An international team of scientists have discovered a new class of object which they call “Super Planetary Nebulae,” found around stars up to 8 times the mass of the Sun.

“This came as a shock to us,” said Miroslav Filipovic from the University of Western Sydney “as no one expected to detect these object at radio wavelengths and with the present generation of radio telescopes. We have been holding up our findings for some 3 years until we were 100% sure that they are indeed Planetary Nebulae”.

The team surveyed the Magellanic Clouds, the two companion galaxies to the Milky Way, with radio telescopes of the Commonwealth Scientific and Industrial Research Organisation (CSIRO) Australia Telescope National Facility. They noticed that 15 radio objects in the Clouds match with well known planetary nebulae observed by optical telescopes.

The new class of objects are unusually strong radio sources and are associated with larger original stars (progenitors), up to 8 times the mass of the Sun. The nebular material around each star may have as much as 2.6 times the mass of the Sun.

Filipovic’s team argues that the detections of these new objects may help to solve the so called “missing mass problem” – the absence of planetary nebulae around central stars that were originally 1 to 8 times the mass of the Sun. Up to now most known planetary nebulae have central stars and surrounding nebulae with respectively only about 0.6 and 0.3 times the mass of the Sun but none have been detected around more massive stars.

Some of the 15 newly discovered planetary nebulae in the Magellanic Clouds are 3 times more luminous than any of their Milky Way cousins. But to see them in greater detail astronomers will need the power of a coming radio telescope – the Square Kilometre Array planned for the deserts of Western Australia.

The scientist’s paper appears in the journal Monthly Notices of the Royal Astronomical Society.

Lead image caption: An optical image from the 0.6-m University of Michigan/CTIO Curtis Schmidt telescope of the brightest Radio Planetary Nebula in the Small Magellanic Cloud, JD 04. The inset box shows a portion of this image overlaid with radio contours from the Australia Telescope Compact Array. The planetary nebula is a glowing record of the final death throes of the star. (Optical images are courtesy of the Magellanic Cloud Emission Line Survey (MCELS) team).

Source: RAS

August 12, 2009December 24, 2015 by Anne Minard

Titan’s Desert Sports a Surprising, Powerful Storm

CREDIT: Gemini Observatory/AURA/Henry Roe, Lowell Observatory/Emily Schaller, Insitute for Astronomy, University of Hawai‘i

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Titan is just fun. Seems like every other week, another fascinating tidbit emerges about how interesting Saturn’s famous moon really is — and how compellingly similar to Earth.

A United States team of astronomers is releasing this image today in Nature. It’s an adaptive optics peek at a storm over the wild object’s parched, dry desert.

The new research, to be published in the August 13 issue of the journal, announces the discovery of significant cloud formation (about three million square kilometers, or 1.16 million square miles) within the moon’s tropical zone near its equator. Prior to this event (in April 2008) it was not known whether significant cloud formation was possible in Titan’s tropical regions. This activity in Titan’s tropics and mid-latitudes also seems to have triggered subsequent cloud development at the moon’s south pole where it was considered improbable due to the Sun’s seasonal angle relative to Titan.

The evidence comes from astronomers using the Gemini North telescope and NASA’s Infrared Telescope Facility (IRTF), both on Hawaii’s Mauna Kea.

“We obtain frequent observations with IRTF giving us a ‘weather report’ of sorts for Titan. When the IRTF observations indicate that cloud activity has increased, we are able to trigger the next night on the Gemini telescope to determine where on Titan the clouds are located,” said team member Emily Schaller, who was at the University of Hawai‘i Institute for Astronomy when this work was done.

Saturn and Titan (six o'clock). CREDIT: Gemini Observatory/AURA/Henry Roe, Lowell Observatory/Emily Schaller, Insitute for Astronomy, University of Hawai‘i

Titan, the solar system’s second largest moon, has received considerable attention by scientists since NASA’s Cassini mission deployed the Huygens probe that descended through the moon’s atmosphere in January 2005. During its descent, the probe’s cameras revealed small-scale channels and what appear to be stream beds in the equatorial regions that seemed to contradict atmospheric models predicting extremely dry desert-like conditions near the equator. Until now these erosional (fluvial) features have been explained by the possibility of liquid methane seeping out of the ground.

“In April 2008 we observed what was a global event that shows how storm activity in one region can trigger clouds, and probably rainfall, over arid regions, such as the tropics where Huygens landed,” said team member Henry Roe, an astronomer at Lowell Observatory. “Of course these rain showers are not liquid water like here on Earth, but are instead made of liquid methane. Just like the streambeds and channels that are carved by liquid water on Earth, we see features on Titan that have been created by flowing liquid methane.”

Unlike the Earth, on Titan, where the temperature is hundreds of degrees below freezing, methane (or natural gas) is a liquid and it the dominant driver of the moon’s weather and surface erosion. Any water on Titan is frozen on or below the moon’s surface and resemble rocks or boulders on Titan’s surface.

Mid-latitude and polar cloud formations have been bserved for many years (by this team and others) but the combination of extensive monitoring at the IRTF with rapid follow-up using Gemini allowed the team to capture the process as it unfolded near the equator. The team monitored Titan on 138 nights over 2.2 years and during that time cloud cover was well under one percent. Then, mid-April of 2008, just after team member and Ph.D. candidate Schaller had handed in her doctoral dissertation focusing on Titan’s minimal cloud cover she noticed the dramatic increase in cloud cover.

During this three-week episode clouds forming at about 30 degrees south latitude were observed, followed several days later by clouds closer to the equator and at the moon’s south pole. The apparent connection between the cloud formations leads to the possibility that cloud formation in one area of the moon can instigate clouds in other areas by a process known as atmospheric teleconnections. This same phenomena occurs in the Earth’s atmosphere and is caused by what are called planetary Rossby waves which are well understood.

The high-resolution Gemini images of Titan were all obtained with adaptive optics technology which uses a deformable mirror to remove distortions to light caused by the Earth’s atmosphere and produce images showing remarkable detail in the tiny disk of the moon.

“Without this technology this discovery would be impossible from the surface of the Earth,” said Schaller. Currently the Cassini spacecraft is orbiting Saturn but only flies by Titan once every 6 weeks or so. This makes continuous ground-based monitoring important for studying features like these with shorter periods on the order of 3-weeks like this storm.

Further detail about the lead image: Gemini North adaptive optics image of Titan showing storm feature (bright area). Titan is about 0.8 arcsecond across in this 2.12 micron near-infrared image obtained on April 14, 2008 (UTC). CREDIT: Gemini Observatory/AURA/Henry Roe, Lowell Observatory/Emily Schaller, Insitute for Astronomy, University of Hawai‘i

Source: Gemini. Other information available through the University of Hawaii, the National Science Foundation (NSF), Lowell Observatory in Flagstaff, Arizona and, of course, Nature.

August 10, 2009December 24, 2015 by John Carl Villanueva

Fate of the Universe

Images of three galaxies from the Galaxy Zoo (top) and STAGES surveys (bottom) show examples of how the newly discovered population of red spiral galaxies on the outskirts of crowded regions in the Universe may be a missing link in our understanding of galaxy evolution.

[/caption]What is the ultimate fate of our universe? A Big Crunch? A Big Freeze? A Big Rip? or a Big Bounce? Measurements made by WMAP or the Wilkinson Microwave Anisotropy Probe favor a Big Freeze. But until a deeper understanding of dark energy is established, the other three still cannot be totally ignored.

Ever since scientists proved the Big Bang to be the most plausible cosmological theory, and since it only focused more on how it might have all began, their attention started to shift to how the Universe would end. Thus, all 4 theories mentioned above (Big Crunch, Big Freeze, etc.) are actually offshoots of the Big Bang.

The Big Crunch predicts that, after having expanded to its maximum size, the Universe will finally collapse into itself to form the greatest black hole ever.

On the opposite side of the coin, the Big Freeze foretells of a universe that will continue to stretch forever, distributing heat evenly in the process until none is left to be usable enough. Hence, it is also known as the Heat Death.

A more dramatic version of the Big Freeze is the Big Rip. In this scenario, the Universe’s rate of expansion will increase substantially so that everything in it, down to the smallest atom, will be ripped apart.

In a cyclic or oscillatory model of the Universe, there will be no end … for matter and energy, that is. But for us and the Universe that we know of, there will definitely be a conclusion. In an oscillatory model, the Big Bang and Big Crunch form a pair known as the Big Bounce. Essentially, such a universe would simply expand and contract (or bounce) forever.

For astronomers to determine what the ultimate fate of the Universe should be, they would need to know certain information. Its density is supposedly one of the most telling.

You see, if its density is found to be less than the critical density, then only a Big Freeze or a Big Rip would be possible. On the other hand, if it is greater than the said critical value, then a Big Crunch or Big Bounce would most likely ensue.

The most accurate measurements on the cosmic microwave background radiation (CMBR), which is also the most persuasive evidence of the Big Bang, shows a universe having a density virtually equal to the critical density. The measurements also exhibit the characteristics of a flat universe. Right now, it looks like all gathered data indicate that a Big Crunch or a Big Bounce is highly unlikely to occur.

To render finality to these findings however, scientists will need to know the exact behavior of dark energy. Is its strength increasing? Is it diminishing? Is it constant? Only by answering these will they know the ultimate fate of the Universe.

We’ve got a few articles that touch on the fate the universe here in Universe Today. Here are two of them:

NASA also has some more:

Tired eyes? Let your ears help you learn for a change. Here are some episodes from Astronomy Cast that just might suit your taste:

Sources: NASA, Hubblesite