Here’s the NASA JPL preview of the night sky for September:
And TMRO.tv offers a Space Pod about the coming month’s cosmic highlights:
Astronomer of TMRO, Jared Head takes a look at what is in the sky for September, 2015. Don’t forget to look up!
TMRO Space Pods are crowd funded shows. If you like this episode consider contributing to help us to continue to improve. Head over tohttp://www.patreon.com/spacepod for information, goals and reward levels. Don’t forget to check out our weekly live show campaign as well over at http://www.patreon.com/tmro
The Twin Jet Nebula, or PN M2-9, is a striking example of a bipolar planetary nebula. Bipolar planetary nebulae are formed when the central object is not a single star, but a binary system, Studies have shown that the nebula’s size increases with time, and measurements of this rate of increase suggest that the stellar outburst that formed the lobes occurred just 1200 years ago. Larger image
The shimmering colours visible in this NASA/ESA Hubble Space Telescope image show off the remarkable complexity of the Twin Jet Nebula. The new image highlights the nebula’s shells and its knots of expanding gas in striking detail. Two iridescent lobes of material stretch outwards from a central star system. Within these lobes two huge jets of gas are streaming from the star system at speeds in excess of one million kilometres per hour.
The cosmic butterfly pictured in this NASA/ESA Hubble Space Telescope image goes by many names. It is called the Twin Jet Nebula as well as answering to the slightly less poetic name of PN M2-9.
The M in this name refers to Rudolph Minkowski, a German-American astronomer who discovered the nebula in 1947. The PN, meanwhile, refers to the fact that M2-9 is a planetary nebula. The glowing and expanding shells of gas clearly visible in this image represent the final stages of life for an old star of low to intermediate mass. The star has not only ejected its outer layers, but the exposed remnant core is now illuminating these layers — resulting in a spectacular light show like the one seen here. However, the Twin Jet Nebula is not just any planetary nebula, it is a bipolar nebula.
Ordinary planetary nebulae have one star at their centre, bipolar nebulae have two, in a binary star system. Astronomers have found that the two stars in this pair each have around the same mass as the Sun, ranging from 0.6 to 1.0 solar masses for the smaller star, and from 1.0 to 1.4 solar masses for its larger companion. The larger star is approaching the end of its days and has already ejected its outer layers of gas into space, whereas its partner is further evolved, and is a small white dwarf.
The characteristic shape of the wings of the Twin Jet Nebula is most likely caused by the motion of the two central stars around each other. It is believed that a white dwarf orbits its partner star and thus the ejected gas from the dying star is pulled into two lobes rather than expanding as a uniform sphere. However, astronomers are still debating whether all bipolar nebulae are created by binary stars. Meanwhile the nebula’s wings are still growing and, by measuring their expansion, astronomers have calculated that the nebula was created only 1200 years ago.
Within the wings, starting from the star system and extending horizontally outwards like veins are two faint blue patches. Although these may seem subtle in comparison to the nebula’s rainbow colours, these are actually violent twin jets streaming out into space, at speeds in excess of one million kilometres per hour. This is a phenomenon that is another consequence of the binary system at the heart of the nebula. These jets slowly change their orientation, precessing across the lobes as they are pulled by the wayward gravity of the binary system.
The two stars at the heart of the nebula circle one another roughly every 100 years. This rotation not only creates the wings of the butterfly and the two jets, it also allows the white dwarf to strip gas from its larger companion, which then forms a large disc of material around the stars, extending out as far as 15 times the orbit of Pluto! Even though this disc is of incredible size, it is much too small to be seen on the image taken by Hubble.
A version of this image was entered into the Hubble’s Hidden Treasures image processing competition, submitted by contestant Judy Schmidt.
This image shows the region of sky around the planetary nebula called the Twin Jet Nebula. The bipolar planetary nebula lies about 4200 light-years away. Larger image.
Astro Maven Rick Boozer points me to the video below showing a talk he gave
at the University of NC at Asheville as the guest of the Astronomy Club of Asheville. In it I discuss astronomical history using photos I shot at the Museo Galileo in Florence, Italy.
Open star clusters like the one seen here are not just perfect subjects for pretty pictures. Most stars form within clusters and these clusters can be used by astronomers as laboratories to study how stars evolve and die. The cluster captured here by the Wide Field Imager (WFI) at ESO’s La Silla Observatory is known as IC 4651, and the stars born within it now display a wide variety of characteristics.
This rich view of a tapestry of colourful stars was captured by the Wide Field Imager (WFI) camera, on the MPG/ESO 2.2-metre telescope at ESO’s La Silla Observatory in Chile. It shows a open cluster of stars known as IC 4651, a stellar grouping that lies at in the constellation of Ara (The Altar). Credit: ESO Larger image.
The loose speckling of stars in this new ESO image is the open star cluster IC 4651, located within the Milky Way, in the constellation of Ara (The Altar), about 3000 light-years away. The cluster is around 1.7 billion years old — making it middle-aged by open cluster standards. IC 4651 was discovered by Solon Bailey, who pioneered the establishment of observatories in the high dry sites of the Andes, and it was catalogued in 1896 by the Danish–Irish astronomer John Louis Emil Dreyer.
The Milky Way is known to contain over a thousand of these open clusters, with more thought to exist, and many have been studied in great depth. Observations of star clusters like these have furthered our knowledge of the formation and evolution of the Milky Way and the individual stars within it. They also allow astronomers to test their models of how stars evolve.
This chart shows the constellation of Ara (The Altar). Most of the stars visible to the naked eye on a clear night are shown. The location of the open cluster, IC 4651, which can be well seen in a medium-sized telescope, is marked with the red circle.
The stars in IC 4651 all formed around the same time out of the same cloud of gas [1]. These sibling stars are only bound together very loosely by their attraction to one another and also by the gas between them. As the stars within the cluster interact with other clusters and clouds of gas in the galaxy around them, and as the gas between the stars is either used up to form new stars or blown away from the cluster, the cluster’s structure begins to change. Eventually, the remaining mass in the cluster becomes small enough that even the stars can escape. Recent observations of IC 4651 showed that the cluster contains a mass of 630 times the mass of the Sun [2] and yet it is thought that it initially contained at least 8300 stars, with a total mass 5300 times that of the Sun.
This wide-field view of the sky around the cluster IC 4651 was created from photographic material forming part of the Digitized Sky Survey 2. The cluster itself is the clump of faint stars in the central part of the picture. The bright star at the left is Alpha Arae, one of the brightest stars in the constellation of Ara (The Altar).
As this cluster is relatively old, a part of this lost mass will be due to the most massive stars in the cluster having already reached the ends of their lives and exploded as supernovae. However, the majority of the stars that have been lost will not have died, but merely moved on. They will have been stripped from the cluster as it passed by a giant gas cloud or had a close encounter with a neighbouring cluster, or even simply drifted away.
This video starts with a view of the southern Milky Way and takes us on a journey towards the open star cluster IC 4651, in the constellation of Ara (The Altar). The MPG/ESO 2.2-metre telescope at ESO’s La Silla Observatory in Chile captured the final rich and colourful close-up view. Credit: ESO/Digitized Sky Survey 2/N. Risinger (skysurvey.org)
A fraction of these lost stars may still be gravitationally bound to the cluster and surround it at a great distance. The remaining lost stars will have migrated away from the cluster to join others, or have settled elsewhere in the busy Milky Way. The Sun was probably once part of a cluster like IC 4651, until it and all its siblings were gradually separated and spread across the Milky Way.
This image was taken using the Wide Field Imager. This camera is permanently mounted at the MPG/ESO 2.2-metre telescope at the La Silla Observatory. It consists of several CCD detectors with a total of 67 million pixels and can observe an area as large as the full Moon. The instrument allows observations from visible light to the near infrared, with more than 40 filters available. For this image, only three of these filters were used.
This pan video gives a close-up view of a rich array of colourful stars known as IC 4651. It was captured by the Wide Field Imager (WFI) camera, on the MPG/ESO 2.2-metre telescope at ESO’s La Silla Observatory in Chile. Credit: ESO
Notes
[1] Although many of the stars captured here belong to IC 4651, most of the very brightest in the picture actually lie between us and the cluster and most of the faintest ones are more distant.
[2] This quantity is in fact much larger than the numbers quoted by previous studies which surveyed smaller regions, leaving out many of the cluster’s stars that lie further from its core.
The Planetary Society‘s Planetary Radio program recently webcast two programs about the Breakthrough Initiative (see earlier post), which plans to spend $10M per year for the next ten years on a search for intelligent life beyond earth.
The Breakthrough Initiatives will pump $100 million into the Search for Extraterrestrial Intelligence in the next 10 years, vastly expanding humanity’s quest to learn if it has company in the universe. Among the leaders of this brave new project is Cosmos creator Ann Druyan. Join us for a special, extended conversation with Ann.
We follow last week’s conversation with Ann Druyan about the $100 million funding of the Search for Extraterrestrial Intelligence by visiting with two of the scientists who will do the work: Dan Werthimer of UC Berkeley and Karen O’Neil of the Green Bank Telescope.
According to Ruslan Belikov and Eduardo Bendek, two research scientists at NASA’s Ames Research Center in California, a 45-kilogram space telescope with a 30-to-45-centimeter mirror would be sufficient to deliver images of rocky planets in the habitable zones of either Alpha Centauri A or B. That’s smaller than some of the telescopes you can buy on Amazon.com, though you can’t purchase a planet-imaging space observatory off-the-shelf quite yet. Belikov, Bendek, and their collaborators call the concept ACESat – the Alpha Centauri Exoplanet Satellite – and have submitted it to NASA in response to the agency’s October 2014 call for proposals for Small Explorer missions, which have budgets capped at $175 million. If selected, the mission would be ready to launch no later than the end of 2020.
The brevity of the bursts is particularly unusual because it means their source has to be extremely small, hundreds of kilometers across at most. And because they exhibit such a high pulse dispersion — a measure of the distance between the arrival of higher frequency waves within the signal compared to lower frequency waves — scientists believe they come from very far away, possibly another galaxy entirely.
All 10 of the bursts detected so far have dispersion measures that are multiples of a single number: 187.5. That’s the mathematical regularity that is hard to shake off. The breakdown of the pattern implies five sources for the bursts all at regularly spaced distances from Earth, billions of light-years away. Scientists have calculated this to be a five in 10,000 probability of a coincidence. In other words, not likely.
“If the pattern is real, it is very, very hard to explain,” said John Learned, a scientist at the University of Hawaii in Manoa who analyzed the FRBs.
