Dwarf Galaxies Also Have Dark Matter
U.S. astronomers have discovered that stars in dwarf spheroidal galaxies behave in a way that suggests they are dominated by dark matter.
University of Michigan astronomy Professor Mario Mateo and post-doctoral researcher Matthew Walker measured the velocity of 6,804 stars in seven dwarf Milky Way satellite galaxies: Carina, Draco, Fornax, Leo I, Leo II, Sculptor, and Sextans. They found that, contrary to Newton's law of gravity, the stars in those galaxies don't move slower the farther they are from their galaxy's core. Instead, they stayed the same. Astronomers were already aware that the stars in spiral galaxies behave in a similar way.
Their research shows that, if Newtonian laws still apply, then dwarf galaxies must be dominated by dark matter.
Dark matter is a substance astronomers haven't directly observed. But they deduce its existence because of its gravitational effects on visible matter.
The findings more than double the amount of data having to do with dwarf galaxies, allowing the galaxies to be studied in an unprecedented manner. The findings appeared in the September 20 issue of the Astrophysical Journal, and Walker will present a paper on the findings October 30 at Magellan Science Meeting in Cambridge, Massachusetts.
To learn more about the University of Michigan Observatories, go here:
Exciting New Astronomy Journal
Astronomy enthusiasts, rejoice! It just became a lot easier for you to understand and explain the world of astronomy. On October 26 the International Astronomical Union (IAU) released the first issue of a new peer-reviewed journal. The publication will provide astronomy communicators with important tools and innovative resources to communicate more effectively the workings of the Universe to the public.
The publication is called the "Communicating Astronomy with the Public Journal," or "CAPjournal." The journal reflects the IAU's commitment to improve the global level of astronomy education and outreach.
The journal came about in this way. An IAU commission prepared a study assessing the feasibility of what became the "CAPjournal." The commission concluded that the present situation of public astronomy communication shows a clear need for a publication addressing the specific needs of the public astronomy communication community.
The main objectives of the new journal are:
- documenting and absorbing knowledge ("Teach and Train");
- providing a basis for discussions;
- compelling further progress;
- establishing priorities in a field;
- furthering careers (through documentation of the excellence of the individual);
- and helping to avoid the duplication of effort.
The journal will be published quarterly, and is divided in nine main sections dedicated to: "News", "Announcements", "Letters to the Editor", "Reviews", "Research & Applications", "Resources", "Innovations", "Best practices" and "Opinion". The "Research & Applications" section contains peer-reviewed science communication 'research' articles. "News" and "Announcements" present information and updates, such as conference reports from the astronomy outreach community. "Resources" and "Innovation" provide a repository of outreach ideas and cutting-edge astronomy communication methods respectively. "Best Practices" aims to be a guide, containing case studies, to the techniques that work best in communicating astronomy. "Opinion" provides space for subjective discussions of topics related to astronomy communication.
The quarterly journal will be published for free in print and online -- yes, I said free. It will act as a repository of ideas for astronomy communicators; for example in use with activities as part of the International Year of Astronomy 2009 which will be a global celebration of astronomy and its contributions to society and culture.
The first two issues are sponsored by the European Space Agency, the International Astronomical Union, Instituto de Astrofísica de Canarias (Spain) and ESO. I have seen no details as to how later issues will be sponsored, but let's hope they will continue to be free.
Free subscription forms and the online version of the journal can be found at http://www.capjournal.org
Three New Exoplanets
Three new planets have been discovered by a team from four UK universities. Powerful cameras in South Africa and the Canary islands found the planets, thought to be the size of Jupiter. The exoplanets (planets outside of our solar system) have been named WASP-3, WASP-4 and WASP-5, and are located in our galaxy.
The planets are so close to their stars that their 'year' (their orbit) lasts less than two days, among the shortest orbital periods yet discovered. Because they are so close to their stars, the surface temperatures of the planets will be more than 2,000C, so astronomers think it unlikely that life as we know it could survive there.
The new planets were discovered by the Wide Area Search for Planets (WASP) project. WASP comprises two robotic observatories designed to detect exoplanets using transiting techniques. The two observatories, located in La Palma and South Africa have been developed with funding by a consortium of four UK universities (Keele, St Andrews, Queen's University Belfast, and Leicester). Of the nearly 200 known exoplanets, less than a dozen are transiting. Using an all-sky survey such as WASP will identify many more candidate targets for more detailed investigation.
The WASP transiting technique is particularly powerful in that it enables the mass and size of the exoplanets to be studied, thereby allowing investigation of planet formation and development. Potentially, observations during primary and secondary eclipse could allow the derivation of spectral and spatial information about the detected planets.
The announcement of the discovery was made October 31. The WASP team are the only ones to find new planets in both the northern and southern hemispheres. To learn more about the WASP project, visit their Weblink: http://www.superwasp.org/wasp_planets.htm
Massive Black Hole Smashes Record
Do you remember the announcement on October 17 of M33 X-7, the stellar-mass black hole in M33? It has mass of 15.7 times that of the sun, which made it the most massive stellar-mass black hole known -- until now (My, how time flies).
Using two NASA satellites, astronomers have discovered the new most massive stellar-mass black hole to orbit a star. It has a mass 24 to 33 times that of our sun, more massive than scientists expected for a black hole that formed from a dying star.
The team which made the discovery was led by Andrea Prestwich of the Harvard-Smithsonian Center for Astrophysics in Cambridge, Massachusetts. Prestwich is also the lead author of the discovery paper in the November 1 Astrophysical Journal Letters. A team member and coauthor Roy Kilgard of Wesleyan University in Middletown, Connecticut.
"Stellar-mass" black holes form in the death throes of massive stars and they are, relatively speaking, much smaller than the supermassive black holes found in galactic cores. But the discovery of such a massive stellar-mass black hole was bit of a surprise. They had not expected a dying star to have that much leftover mass for the black hole. Astronomers are now rethinking what the new upper mass limit might be for a stellar-mass black hole.
The black hole is located in the nearby dwarf galaxy IC 10, which is 1.8 million light-years from Earth in the constellation Cassiopeia. The team could measure the mass of the black hole because it has an orbiting companion: a hot, highly evolved star (a Wolf-Rayet star, a type destined to explode as a supernova). The star is ejecting gas in the form of a solar wind. Some of this material spirals toward the black hole, heats up, and gives off powerful X-rays before crossing the black hole's event horizon -- the point of no return.
In November 2006, the team observed the dwarf galaxy with NASA's Chandra X-ray Observatory. The group discovered that the galaxy's brightest X-ray source, IC 10 X-1, exhibits sharp changes in X-ray brightness. That behavior suggested a star was periodically passing in front of a companion black hole and blocking the X-rays, creating an eclipse. In late November, NASA's Swift satellite confirmed the eclipses (which have a frequency of once every 34.4 hours) and Swift revealed more details about the star's orbit. The star in IC 10 X-1 appears to orbit in a plane that lies nearly edge-on to Earth's line of sight, The Swift observations, as well as observations from the Gemini Telescope in Hawaii, told the team how fast the two stars go around each other. Calculations showed that the companion black hole has a mass of at least 24 suns.
There are still some uncertainties in the black hole's mass estimate, but future optical observations will provide a final check. The team thinks that any refinements in the IC 10 X-1 measurement will likely increase the black hole's estimated mass rather than reduce it.
The black hole's large mass is surprising because massive stars generate powerful winds that blow off a large fraction of the star's mass before it explodes. Calculations suggest massive stars in our Milky Way galaxy leave behind black holes no heavier than about 15 to 20 suns.
The IC 10 X-1 black hole has gained mass since its birth by gobbling up gas from its companion star, but the rate is so slow that the black hole would have gained no more than 1 or 2 solar masses. The rest of the mass had to come from the original star. The team thinks the star probably started its life with 60 or more solar masses. Like its host galaxy, it was probably deficient in elements heavier than hydrogen and helium. In massive, luminous stars with a high fraction of heavy elements, the extra electrons of elements such as carbon and oxygen "feel" the outward pressure of light and are thus more susceptible to being swept away in stellar winds. But with its low fraction of heavy elements, the IC 10 X-1 progenitor shed comparatively little mass before it exploded, so it could leave behind a heavier black hole.
The team also noted that massive stars in our galaxy today are probably not producing very heavy stellar-mass black holes, but there could be, waiting to be discovered, many heavy stellar-mass black holes produced early in the Milky Way's history, before it had a chance to build up heavy elements.
To learn more about the discovery, and about the NASA' s Swift Gamma-Ray Burst Mission, go here: http://heasarc.gsfc.nasa.gov/docs/swift/swiftsc.html and to learn more about the Gemini Observatory, check out: http://www.gemini.edu
Robert T. McCall Artwork Donation
I mention this story because I think it is just so cool. On October 9, the amazing artist Robert T. McCall announced his donation to the University of Arizona Museum of Art (UAMA) of more than 200 original pieces. The collection is valued at nearly $3 million.
McCall has been painting for nearly seven-decade and the donated works include documentation of more than 35 years of the U.S. space program. McCall formally announced his gift at the opening of an exhibit of his works at the Paradise Valley Town Hall. The 18 pieces on display there are part of the collection going to the UA Museum of Art. The collection, which includes McCall's personal archives and notes, is a lead gift to establish the Archive of Visual Arts (AVA) at the UAMA.
In addition to being a visual historian for NASA, McCall has served as a conceptual artist for the entertainment industry. One of his most well known commercial pieces is the poster art for the classic motion picture 2001: A Space Odyssey.
McCall and his wife Louise live in Paradise Valley and McCall is a longtime supporter of the UA's efforts in space exploration, serving on the University's astronomy board.
To view wonderful examples of McCall's work, visit his online gallery:
MARS IS COMING, PART 1
Mars is approaching opposition and will give us its best views until the next opposition in early 2010. Mars will be closest to Earth on December 18/19 and will finally reach opposition with Earth on December 24. We have some time before then, but with every day that passes Mars will appear larger and larger in our eyepieces. I therefore thought I would take this opportunity to share bits of information about the Red Planet as we approach this opposition. Here is the first installment.
Mars, An Introduction
Mars is the fourth planet in the solar system in order of distance from the sun and the seventh planet in size and mass. It is a noticeable and sometimes very bright, reddish object in the night sky -- some would say blood-red -- and it is sometimes called the Red Planet. The reddish color is caused by high iron content on the Martian soil. Mars has long been associated with warfare, death and suffering. Today we call the planet by the name of the Roman god of war. But 3,000 years ago, Babylonian astronomers/astrologers called the planet Nergal, the name of their god of death and pestilence. Mars has two moons, named Phobos ("Fear") and Deimos ("Terror"). These were the names of two of the sons of the Greek god Ares (the counterpart of Mars) and the Greek goddess Aphrodite (the counterpart of Venus). Mars is designated by the symbol of a circle and angled arrow, representing a warrior's spear and shield.
Mars orbits the sun at an average distance of 227,936,640 km (141,633,260 miles). That is 1.523662 times the average distance of Earth, or 1.523662 A.U. The Martian day (called a "sol") lasts 24.62 Earth hours, and the Martian year lasts 686.93 Earth days. Mars' equatorial diameter is 6,794 km (4,220 miles) -- just over have the diameter of Earth. Its density is only 0.714 times that of Earth, and its mass is only 0.17044 times that of Earth. In addition, Mars has little or no magnetic field. This fact, combined with its mass and density, suggest that Mars has very little metal in its core. As you might have already guessed, the surface gravity of Mars is much less than Earth. If you weighted 100 on Earth you would way only 38 pounds on Mars.
Mars has an axial tilt to its orbital plane of 25.19°, so Mars has seasons. The planet surface temperature ranges from -87 to -5°C (-125 to 23°F) and the average daytime surface temperature is 20°C (10°F). Mars has a very thin atmosphere compared to Earth, 0.7–0.9 kilopascal units, about 1/126 that of Earth. The Martian atmosphere includes carbon dioxide (95%), some nitrogen (2.5%) and argon (1.5%) and traces of carbon monoxide, water vapor, and other molecules and compounds. The atmosphere in the past appears to have been much denser and warmer with much more water. Some spacecraft images suggest that some liquid water flowed near the surface in relatively recent times. To date, no life has been detected.
Spacecraft images show a long and complex history of geological activity. The most noticeable feature is the contrast between the mostly smooth, lowland volcanic plains of the northern hemisphere and the heavily cratered uplands of the southern hemisphere. Martian geological features include a cratered surface, volcanoes, lava plains, flood channels, and giant canyons. Olympus Mons, the largest known volcano in the solar system, is hundreds of kilometers across and 27km (17mi) high. The polar ice caps vary in size with the season and appear to be composed of solid carbon dioxide with smaller caps of water ice underneath. Wind is an important element on Mars. It sculpts features such as dunes, occasionally causing global dust storms.
Next Time: “Early Observations and Visible Surface Features”
Mars. (2007). In Encyclopædia Britannica. Retrieved October 26, 2007 , from Encyclopædia Britannica Online: http://www.britannica.com/eb/article-9110149
Mars (2007). In The Columbia Encyclopedia, Sixth Edition 2007. Copyright 2007 Columbia University Press. Retrieved October 26, 2007 from Encyclopedia.com
Mars (2005). In World Encyclopedia. Copyright 2005 World Encyclopedia 2005, originally published by Oxford University Press 2005. Retrieved October 26, 2007 from Encyclopedia.com
Planets: Mars. In NASA Solar System Exploration, Last updated October 23, 2007. Retrieved October 26, 2007, from the NASA Solar System Exploration website, maintained by NASA's Jet Propulsion Laboratory:
THE SKY THIS WEEK
Nov 3/4 - Peak of the Southern Taurid Meteor Shower. This is one of two showers visible in the fall and winter that originate from the constellation Taurus. Both of these showers appear to be caused by Periodic Comet Encke. The other shower is called the Northern Taurid shower The Southern Taurid meteors are visible from September 15 through December 15 with the peak on November 3. The average meteor rate ranges from 5 to 15 per hour. The coordinates for the radiant of the Southern Taurid shower is RA 03hrs 44min, +14°.
Meteors are best viewed from a dark-sky location. Observers in for the duration of the evening, or at least for several hours, should bring along a few things: a sleeping bag or blankets for warmth, a recliner or lawn chair, a hot beverage to help cut the chill, and binoculars to view the smoke trails of just-past meteors.
Nov 4 - End Daylight Saving in United States. Set clocks back 1 hour
Nov 5 - Venus is 3° north of Moon
Nov 8 - Mercury is 7° north of Moon
Nov 8 - Mercury is at its greatest western elongation (19°)
Nov 9, 6:03 P.M. EST - New Moon
Nov 9 - Moon at apogee, the point in the Moon's orbit when it is farthest from Earth.
Nov 9 - Dwarf Planet Ceres at opposition, the point when a solar system body orbiting farther from the Sun than Earth appears opposite the Sun in the sky. Opposition is the best time to observe a body.
THIS WEEK IN HISTORY
Nov 4, 1981 - Venera 14 Launch (USSR Venus Lander/Flyby)
Nov 5, 1906 - Fred Whipple's birthday
Nov 7, 1966 - Lunar Orbiter 2 launch
Nov 7, 1967 - Surveyor 6 launch (Moon Lander), 40th anniversary
Nov 7, 1996 - Mars Global Surveyor launch
Nov 8, 1656 - Edmund Halley's birthday
Nov 8, 1960 - Little Joe 5 launch, test of the launch escape system of Mercury production spacecraft #3. The flight was a failure and the spacecraft was destroyed.
Nov 8, 1982 - Wethersfield Meteorite Fall (Hit House), 25th anniversary
Nov 9, 1934 - Carl Sagan's birthday
Nov 9, 1967 - 1st Saturn V Launch (Apollo 4), 40th anniversary
Nov 10, 1970 - Luna 17 Launch (USSR Moon Rover)
"Tramp! Tramp! Tramp!" and "Jesus Loves the Little Children"
"Tramp! Tramp! Tramp!" was written in 1864 by George Frederick Root (1820-1895). Root, who was named after George Frideric Handel, was a music educator and composer, noted for his sacred and patriotic music. Among his other patriotic credits are "The Battle Cry of Freedom," "Just Before the Battle, Mother," "The Shining Shore," and "The First Gun Is Fired" which was written in April 1861 after the firing on Fort Sumter. "Tramp! Tramp! Tramp!" became one of the most popular songs of the American Civil War. The song opens in the cell of a military prison, but the chorus expresses hope for rescue and ultimate victory. At first, the song was sung only by the troupes in the Northern armies. Later, Confederate lyrics were written (by an author unknown) and the Confederate version became just as popular in the Southern armies.
Tramp! Tramp! Tramp!
(Original, Northern version)
In the prison cell I sit,
Thinking Mother dear of you,
And our bright and happy home so far away,
And the tears they fill my eyes
Spite of all that I can do
Though I try to cheer my comrades
and be gay.
Tramp! tramp! tramp!
The boys are marching
Cheer up comrades,
They will come.
And beneath the starry flag
We shall breathe the air again
Of the free land in our own beloved home.
In the battle front we stood
When their fiercest charge they made,
And they swept us off a hundred men or more;
But before we reached their lines
They were beaten back, dismayed,
And we heard the cry of vict'ry o'er and o'er.
So within the prison cell
We are waiting for the day
That shall come to open wide the iron door;
And the hollow eye grows bright
And the poor heart almost gay
As we think of seing home and friends once more.
Tramp! Tramp! Tramp!
In my prison cell I sit,
thinking, Mother, dear, of you,
and my happy Southern home so far away;
and my eyes they fill with tears
'spite of all that I can do,
though I try to cheer my comrades and be gay.
Tramp! Tramp! Tramp!
The boys are marching;
cheer up, comrades, they will come.
And beneath the stars and bars
we shall breathe the air again
of freemen in our own beloved home..
In the battle front we stood
when their fiercest charge they made,
and our soldiers by the thousands sank to die;
but before they reached our lines,
they were driven back dismayed,
and the "Rebel yell"went upward to the sky.
Now our great commander Lee
crosses broad potomac's stream,
and his legions marching Northward take their way.
On pennsylvania's roads
will their trusty muskets gleam,
and her iron hills shall echo to the fray.
In the cruel stockade-pen
dying slowly day by day,
for weary months we've waited all in vain;
but if God will speed the way
of our gallant boys in gray,
I shall see your face, dear Mother, yet again.
When I close my eyes in sleep,
all the dear ones 'round me come,
at night my little sister to me calls;
and mocking visions bring
all the warm delights of home,
while we freeze and starve in Northern prison walls.
So the weary days go by,
and we wonder as we sigh,
if with sight of home we'll never more be blessed.
Our hearts within us sink,
and we murmur, though we try
to leave it all with him who knowest best.
Some time after the war, the tune went in a different direction. One of Root's favorite lyricist, Clare Herbert Woolston (1856-1927), wrote a new hymn text that was set to Root's melody. It is said that Woolston was inspired by the Bible verse Matthew 1:14 where Jesus says, "Let the children come to me. Don't stop them! For the Kingdom of Heaven belongs to such as these." Not everyone recalls the verses of the hymn, but the refrain is often sung today as a hymn in itself.
Jesus Loves The Little Children
Jesus calls the children dear,
"Come to me and never fear,
For I love the little children of the world;
I will take you by the hand,
Lead you to the better land,
For I love the little children of the world."
Jesus loves the little children,
All the children of the world.
Red and yellow, black and white,
All are precious in His sight,
Jesus loves the little children of the world.
Jesus died for all the children,
All the children of the world.
Red and yellow, black and white,
All are precious in His sight,
Jesus died for all the children of the world.]
Jesus is the Shepherd true,
And He'll always stand by you,
For He loves the little children of the world;
He's a Savior great and strong,
And He'll shield you from the wrong,
For He loves the little children of the world.
I am coming, Lord, to Thee,
And Your soldier I will be,
For You love the little children of the world;
And Your cross I'll always bear,
And for You I'll do and dare,
For You love the little children of the world.
To review the Northern version of "Tramp! Tramp! Tramp!", visit this page of the "Popular Songs in American History" section of section of "Contemplations from the Marianas Trench - Music and Deep Thoughts" - http://www.contemplator.com/america/tramptramp.html
To review the Confederate version of "Tramp! Tramp! Tramp!", visit this page of the "Popular Songs in American History" section of section of "Contemplations from the Marianas Trench - Music and Deep Thoughts" - http://www.contemplator.com/america/trampsouth.html
To see and hear more on the hymn, " Jesus Loves the Little Children" visit this page of "The Cyber Hymnal" - http://www.cyberhymnal.org/htm/j/e/jesloves.htm