Newsletter from The Society for Popular Astronomy

*********************************** The SOCIETY for POPULAR ASTRONOMY *********************************** ==================================================== Electronic News Bulletin No. 287 2010 April 25 ==================================================== Here is the latest round-up of news from the Society for Popular Astronomy. The SPA is Britain's liveliest astronomical society, with members all over the world. We accept subscription payments online at our secure site and can take credit and debit cards. You can join or renew via a secure server or just see how much we have to offer by visiting http://www.popastro.com/ EARLY APRIL FIREBALLS By Alastair McBeath, SPA Meteor Section Director The first part of April this year has brought a healthy crop of fireballs (meteors of magnitude -3 or brighter) to the Section so far. Single- observer meteors were reported at 03:17 UT on April 6-7 (magnitude -7, seen from Edinburgh), about 04:25 UT on April 11-12 (very bright; Cornwall) and 21:31 UT on April 14-15 (-5/-7; Gwent), plus there were two others seen from more than one location. At 20:15 ± 5 minutes UT on April 9-10, a magnitude -10 or so meteor was spotted from Glasgow and Edinburgh. Reports from the witnesses suggested the object may have followed a roughly south to north trajectory over eastern Scotland north of the Fife peninsula, perhaps across part of the eastern Grampian Mountains of the "Aberdeen angle", or the North Sea offshore of there. On April 16-17 near 22:00 UT, a very bright, green fireball was seen from four locations in southern England - Gloucester, Surrey, Hampshire, and Devon. Two of the initial sightings can be found on the UK Weather World's Space Weather Forum (at: http://snipurl.com/vobdi ). This fireball seemed to have been out high above the western Channel, and part of its flight may have been some way offshore of the English coast between roughly Prawle Point in Devon and Lizard Point in Cornwall. Most observers were impressed both by its brilliance and its vivid green colour, though suggestions the colour may have been due to the volcanic ash cloud over and near the British Isles from Iceland, were without foundation. Bright green, though not common, does occur in meteors, particularly the brighter ones, without any such assistance. All further sightings of these, or other fireballs, made from the British Isles and nearby, would be welcomed by the Section. The minimum details required are: 1) Exactly where you were (give the name of the nearest town or large village and county if in Britain, or your geographic latitude and longitude if elsewhere in the world); 2) The date and timing of the event in UT (remember to subtract one hour from current clock time, BST, to get UT); and 3) Where the fireball started and ended in the sky, as accurately as possible, or where the first and last points you could see of the trail were if you did not see the whole flight. More advice and a fuller set of details to send (including an e-mail report form) are given on the "Making and Reporting Fireball Observations" page of the SPA website, at: http://snipurl.com/u8aer . The Easter break has also prompted another flurry of "sky lantern" sightings, sadly. These were last so problematic back in January (see ENB 280, at: http://snipurl.com/ucps9 ). In order not to miss genuine fireball observations, the Meteor Section is willing to receive reports of any unusual moving star-like light in the sky, where the witness could not be sure what the object was. However, it is very important to send as many details as possible - ideally completing the electronic Fireball Report Form fully - to enable the object's nature to be determined swiftly and accurately. An unhelpfully large number of the recent potential lantern sightings have had insufficient information provided initially to allow this, to the extent some could even have been genuine fireballs. Please remember this when sending in a possible fireball sighting, and help us to better help you! BRILLIANT IMAGED FIREBALL OVER THE USA By Alastair McBeath, SPA Meteor Section Director Around 22:05 local time on April 14, a spectacular fireball was seen from at least six states in the Midwest and Great Lakes regions of the USA, lighting-up the sky. Video recordings of the very slow, brilliant meteor were made by-chance, which were quickly picked-up by TV news stations and broadcast across the world. The videos are available online - try the BBC's News webpage at http://snipurl.com/voeg5 , for instance - while there are more comments, and links to additional Internet sites on the UK Weather World's Space Weather Forum topic at: http://snipurl.com/voekk . As too often, an immediate claim was made that the fireball had come from a meteor shower, this time the very minor Gamma Virginids, based on nothing more than a wild guess, because of when it had happened. Another week, and doubtless it would have been called a Lyrid! If the videos as broadcast were accurate to the object's appearance, especially its apparent speed, the actual fireball seemed to have been well below the slow-medium atmospheric velocity, around 30 km/sec, expected for the Virginids or any of the Antihelion Source meteors (as we currently term meteors from the many, very weak, radiants clustered near the ecliptic nearly opposite the Sun in the sky, and active for most of the year - see the April meteor activity webpage for notes on the Antihelion Source this month, at http://snipurl.com/vogzo ). None of this detracts from the magnificence of the fireball, of course! COMET McNAUGHT HAD UNUSUALLY LONG ION TAIL RAS British scientists have shown from Ulysses spacecraft data that Comet McNaught, which in early 2007 became the brightest comet seen for 40 years, disturbed a region of space much larger than that occupied by the visible tail. Analysis of magnetometer data suggests that the comet was surrounded by a shock wave created where the fast-flowing particles of the solar wind were slowed down abruptly when they impinged on the ionized gas emitted from the comet's nucleus. It was just by chance that Ulysses happened to pass through Comet McNaught's tail; it encountered the tail of ionized gas at a distance downstream of the comet's nucleus more than 1.5 times the distance between the Earth and the Sun -- much further away than the visible dust tail extended. Ulysses took 8 days to traverse the shocked solar wind surrounding Comet McNaught, compared to 2.5 days in shocked wind surrounding Comet Hyakutake in 1996. The Giotto spacecraft's encounter with Comet Grigg-Skjellerup in 1992 took less than an hour from one shock crossing to another; to cross the shocked region at Comet Halley took a few hours. The comparisons show that Comet McNaught was not only spectacular from the ground but was an unusually large obstacle to the solar wind. VENUS IS VOLCANICALLY ACTIVE ESA Venus Express has returned the clearest indication yet that Venus is still active. Relatively young lava flows have been identified by their emission of infrared radiation. The finding suggests that the planet remains capable of volcanic eruptions. The sparseness of craters on Venus suggests that something is wiping the planet's surface clean. That something is thought to be volcanic activity, but the question is whether it happens quickly or slowly -- whether there is some sort of cataclysmic volcanic activity that resurfaces the entire planet with lava, or a gradual sequence of smaller volcanic eruptions. The latter are suggested by maps of the infrared brightness or 'emissivity'. Astronomers concentrated on three regions that are analogous to Hawaii, well-known for its active vulcanism. Those regions on Venus have higher emissivities than their surroundings, indicating different compositions. On Earth, lava flows react rapidly with oxygen and other elements in the atmosphere, changing their composition. On Venus, the process should be similar, though more vigorous because of the hotter, denser atmosphere. The researchers interpret the areas of high emissivity as lava flows that have not undergone as much weathering as their surroundings, implying that they are relatively recent, possibly even still forming. PLUTO SHOWS CHANGES NASA A comparison of Hubble Telescope images of Pluto obtained in 1994 and 2003 shows that the northern hemisphere has brightened while the southern hemisphere has dimmed. Ground-based observations suggest that Pluto's atmosphere doubled in mass during approximately the same interval. Pluto gets so cold that its atmosphere can actually freeze and fall to the ground. If the Earth's atmosphere did that, it would make a layer 30 feet thick, but Pluto has far less atmosphere. When it is on the ground, Pluto's entire blanket of air is no more than a frosty film of nitrogen and methane. Until the mid-1980s, Pluto's northern hemisphere had been tilted away from the Sun for over 100 years, accumulating a substantial amount of frost. Now the northern hemisphere is coming into sunlight and appears, as shown in the Hubble images, to have been growing brighter. The atmosphere might also be changing in response to Pluto's highly eccentric orbit. During the late 1980s, Pluto approached as close to the Sun as it ever gets and was consequently warming. Surface frosts exposed to such 'warmth' may be subliming -- that is, changing back into gas. DUSTY DISCS IN PLANETARY SYSTEMS RAS Two stars observed in the infrared with the MIDI interferometer, which combines the light from the 8-m units of the VLT in Chile, appear to have discs of rocky and dusty material at distances comparable to that from the Earth to the Sun. The stars concerned, both considerably younger than the Sun, are HD 69830, of spectral type K0 V, in the constellation Puppis and thought to have three planets with masses comparable to Neptune, and Eta Corvi, type F2 V. Earlier observations had indicated that both stars had discs; Eta Corvi is known to have cold material around it at a distance of 150 Astronomical Units (Earth--Sun distances; 1 AU is about 150 million km). With MIDI a relatively small dusty disc around HD 69830 was clearly seen; it lies between 7.5 and 360 million km from the star. A similar disc was found close to Eta Corvi, lying between 24 to 450 million km out. Those results represent the first resolution of dusty discs so close to their parent stars. COOLEST BROWN DWARF FOUND NEAR SUN University of Hertfordshire Brown dwarfs are bodies with masses in the range between those of giant planets and the faintest stars. Some are isolated, while others orbit normal stars or exist in star clusters. Astronomers have now discovered a previously unknown brown dwarf just 2.9 parsecs (9 light- years) away -- the seventh-closest star, and the first to be found so close since Luyten 726-8 was discovered in 1948. The star, UGPS J0722-05, has a temperature of 400-500 K and is far less luminous and significantly cooler than previously known objects. The Jupiter-sized object emits only 0.000026% as much energy as the Sun. Since 1995, more than 100 methane brown dwarfs, or T dwarfs, have been found, with spectra similar to that of the planet Jupiter and with effective temperatures in the range 500-1300 K. The detection of even cooler bodies will open a new arena for atmospheric physics and may help to determine the formation rate of stars and brown dwarfs in our Galaxy as a function of both mass and time. ROCKY PLANETS MAY BE COMMON IN THE MILKY WAY RAS Astronomers have found evidence that rocky planets are commonplace in our Galaxy. A survey of white dwarfs, the compact remnants of stars that were once like our Sun, found that many show signs of contamination by heavier elements and possibly water. White dwarfs are the endpoint of stellar evolution for the vast majority (>90%) of all stars in the Milky Way. Because they ought to have almost pure hydrogen or helium atmospheres, if heavier elements such as calcium, magnesium and iron are found then they are interpreted as external pollutants. For decades, it was believed that the interstellar medium (the tenuous gas between the stars) was the source of the metals in the polluted white dwarfs. The team used data from the Sloan Digital Sky Survey (SDSS), a project that aims to survey the sky in infrared light, imaging more than 100 million objects and following up 1 million of them by obtaining their spectra. By examining the positions, motions and spectra of the white dwarfs identified in the SDSS, the team shows that an interstellar origin for the metals is no longer a satisfactory theory. Instead, rocky planetary debris is probably the usual culprit. The new work indicates that at least 3% and perhaps as much as 20% of all white dwarfs are contaminated in this way, with the debris most likely in the form of rocky minor planets with a total mass of about that of an asteroid 140 km in diameter. That implies that a similar proportion of stars like our Sun, as well as stars that are somewhat more massive, like Vega and Fomalhaut, build terrestrial-type planetary systems. The scientists also measured the composition of the pollutants through their spectroscopic signatures, which stand out in the otherwise pure atmosphere of the white dwarfs. It appears that a significant fraction of the stars are polluted with material that contained water, with implications for the frequency of habitable planets around other stars. BLACK HOLES AND GALAXY DEATH RAS Black holes are thought to reside at the centre of almost every galaxy, with some growing to more than a billion times the mass of the Sun. Now a team of UK astronomers has proposed that such super- massive black holes are commonplace, release more than enough energy to strip their host galaxies apart, and in the process shut down star formation in their galaxies for good. For many years black holes have fascinated scientists and the public alike, with their peculiar ability to warp space and time and their sinister tendency to devour everything they encounter. Before matter falls in, as it swirls around the black hole it forms an 'accretion disc', where it heats up and radiates energy. The super-massive black holes have such strong gravitational fields that the infalling matter releases a vast amount of energy, making each accretion disc far brighter than the combined output of the billions of stars in the galaxy around it. One of the consequences of such outpouring of energy is that it drives away cool gas and dust, the raw ingredients of new stars. That permanently shuts down star-formation in the surrounding galaxy, whose remaining stars age, end their lives, and are never replaced. The new study considered the role of super-massive black holes in the development of galaxies. To search for them, the team used the Hubble telescope and the Chandra X-ray observatory to observe in optical, near-infrared and X-ray light. In particular, the astronomers looked for galaxies which have a very high emission of X-rays, a probable signature of black holes devouring gas and dust. From the space telescopes' data astronomers find that at least 1/3 of all the massive galaxies they observed not only contain super-massive black holes, but that at some point in their histories the emission from the holes' accretion discs far outshines the galaxies themselves. The energy output of regions around the black holes is high enough to strip apart every massive galaxy in the cosmos 25 times over, whilst the X-ray emission from them turns out to dwarf that from every other source in the Universe put together. POSSIBLE MICROQUASAR IN STARBURST GALAXY M82 RAS Radio astronomers at Jodrell Bank have discovered a strange new object in M82, a galaxy that is 10 million light-years away and is forming new stars at a prodigious rate, many of them massive stars that die quickly, a supernova explosion occurring every 20 to 30 years. The new object, which appeared last May, has perplexed astronomers, who have never seen anything quite like it before. The object turned on very rapidly within a few days and has shown no sign of decaying in brightness over the first months of its existence. The new young supernova explosions that astronomers expect to see in M82 brighten at radio wavelengths over several weeks and then decay over several months, so that explanation seems unlikely. The plausibility of a supernova explanation was further undermined when very accurate positional monitoring by the UK network of radio telescopes, MERLIN, tentatively detected a change in position for the object over the first 50 days. It was equivalent to an apparent motion of over four times the speed of light. Such large apparent velocities are not seen in supernova remnants and are usually only found with relativistic jets ejected from accretion discs around massive black-hole systems. The nucleus of M82 may contain a super-massive black hole. The new detection lies at a position close to, but several arcseconds away from, the dynamical centre of M82 -- far enough away that it would seem unlikely that this object is associated with the central collapsed core of the galaxy. The new source could be the first radio detection of an extragalactic 'micro-quasar'. Examples of such systems within the Milky Way are found as X-ray binaries with relativistic jets ejected from an accretion disc around a collapsed star fuelled with material dragged from a close binary companion. However, this object would be brighter than any Galactic example yet detected, has lasted months longer than any known X-ray binary, and lies at a position in M82 where no variable X-ray source has been yet been detected. LOFAR OPENS UP LOW-FREQUENCY UNIVERSE RAS The Low Frequency Array (LOFAR), a new pan-European radio-astronomy instrument, has started mapping the Universe at very long wavelengths, a part of the electromagnetic spectrum that is relatively unexplored. Astronomers hope LOFAR will allow them to study cosmic rays, pulsars, and the magnetic field within our own and nearby galaxies. LOFAR will also compile a census of radio-emitting galaxies from the very early Universe, which may help us to understand how galaxies formed and evolved over cosmic time. NEXT BULLETIN Owing to holidays, the next scheduled bulletin will be issued on May 16. Bulletin compiled by Clive Down (c) 2010 the Society for Popular Astronomy The Society for Popular Astronomy has been helping beginners to amateur astronomy -- and more experienced observers -- for more than 50 years. If you are not a member then you may be missing something. Membership rates are extremely reasonable, starting at just £16 a year in the UK. You will receive our bright quarterly magazine Popular Astronomy, regular printed News Circulars, help and advice in pursuing your hobby, the chance to hear top astronomers at our regular meetings, and other benefits. The best news is that you can join online right now with a credit card or debit card at our lively website: http://www.popastro.com/ Astronomica is a firm set up by astronomers to sell astronomical equipment at affordable prices, and offers SPA members a 10% discount on all products. Details of any special offers can be found at http://www.astronomica.co.uk

Comet Lovejoy Update

Comet Lovejoy Update 

                 ***********************************
                  The SOCIETY for POPULAR ASTRONOMY
                 ***********************************
         ====================================================
          Electronic News Bulletin No. 324    2012 January 1
         ====================================================


Here is the latest round-up of news from the Society for Popular
Astronomy.  The SPA is Britain's liveliest astronomical society, with
members all over the world.  We accept subscription payments online
at our secure site and can take credit and debit cards.  You can join
or renew via a secure server or just see how much we have to offer by
visiting     http://www.popastro.com/



COMET LOVEJOY PLUNGES PAST THE SUN AND SURVIVES
NASA

In mid-December there was an exciting event, when Comet Lovejoy passed
through the Sun's corona and emerged intact.  The comet's close
encounter was recorded by at least five spacecraft.  In movies made by
the SDO (Solar Dynamics Observatory), the comet's tail was seen to
wriggle wildly, no doubt as a result of electrical or magnetic
interaction in the corona, as the comet plunged through the Sun's
corona only 120,000 km above the photosphere.  Comet Lovejoy was
discovered on December 2 by amateur astronomer Terry Lovejoy in
Australia.  Researchers quickly realized that the new find was a
member of the Kreutz family of Sun-grazing comets.  Named after the
German astronomer Heinrich Kreutz, who first studied them, Sun-grazers
are fragments of a giant comet that broke apart in the 12th century
(probably the Great Comet of 1106).  Kreutz Sun-grazers are very
numerous and typically small (~10 metres), although there have been
major examples such as Ikeya-Seki in 1965, which on the day of
perihelion passage was visible to the naked eye in full daylight (the
Sun of course having to be hidden from view behind a chimney or
something!)  The Solar and Heliospheric Observatory sees one falling
into the Sun every few days.  At the time of discovery, Comet Lovejoy
appeared to be much larger than the usual run of Kreutz Sun-grazers,
perhaps in the 100-200-m range, but researchers are revising those
numbers upward.


ASTRONOMERS FIND EARTH-SIZED PLANETS
NASA

Astronomers think that they have found two Earth-sized planets
orbiting a star similar to the Sun.  The discovery follows
confirmation last month of a super-Earth-sized planet, called
Kepler-22b, that circles the right distance from its parent star for
liquid water to exist on its surface.  The newly discovered planets,
called Kepler-20e and 20f, have at least three gas-giant siblings, in
one of the larger planetary systems found to date.  But the family is
nothing like our Solar System, where rocky planets like Venus, the
Earth and Mars are grouped together relatively near the Sun, while gas
giants like Jupiter and Saturn are segregated in the outer regions.
The two Earth-like and three Neptune-sized planets in the Kepler-20
system are interspersed, and all of them orbit closer to the parent
star than Mercury does to the Sun.  The system is located about 1,000
light-years away in the constellation Lyra.


RAPID STAR FORMATION IN A GALAXY ALMOST AT THE DAWN OF TIME
University of California

One of the most distant galaxies known, GN-108036, which is at a
red-shift of 7.2 and a distance of about 12.9 billion light-years, has
been found to be forming stars at a particularly high rate.  The
galaxy is the brightest one found to date at such a great distance.
An international team of astronomers using the Japanese Subaru
telescope on Mauna Kea in Hawaii first identified it; then infrared
observations from Spitzer and Hubble were used to estimate that the
galaxy's star-formation rate is equivalent to about 100 Suns per year.
For comparison, our Milky Way galaxy is about five times larger and
100 times more massive than GN-108036, but makes stars at a rate of
about 3 Suns per year.  The discovery is surprising, because previous
surveys had not found such bright galaxies so early in the history of
the Universe.  According to the researchers, GN-108036 may be a
special, rare object that they happened to observe during an extreme
burst of star formation.



Bulletin compiled by Clive Down


(c) 2012 the Society for Popular Astronomy


The Society for Popular Astronomy has been helping beginners to
amateur astronomy -- and more experienced observers -- for more than
50 years.  If you are not a member then you may be missing something.
Membership rates are extremely reasonable, starting at just £16 a year
in the UK.  You will receive our bright bi-monthly magazine Popular
Astronomy, help and advice in pursuing your hobby, the chance to hear
top astronomers at our regular meetings, and other benefits.  The best
news is that you can join online right now with a credit card or debit
card at our lively website:   http://www.popastro.com/

latest news from the Society for Popular Astronomy

[Their formatting, not mine!]

Get the 3D Sun app from the Android market. 

                ***********************************
                 The SOCIETY for POPULAR ASTRONOMY
                ***********************************
        ====================================================
         Electronic News Bulletin No. 320   2011 November 6
        ====================================================

Here is the latest round-up of news from the Society for Popular
Astronomy.  The SPA is one of Britain's liveliest astronomical
societies, with members all over the world.  We accept subscription
payments online at our secure site and can take credit and debit
cards. You can join or renew via a secure server or just see how much
we have to offer by visiting    http://www.popastro.com/

SOLAR ACTIVITY
By Richard Bailey, SPA Solar Section Director

One of the largest active regions in years, AR 1339, has come into
view around the east limb of the Sun, and will change shape over the
coming days.  It could be a source of flares, as well as filaments and
bright plaging.  The main sunspot is Earth-sized.  It can be viewed by
projecting an image of it with a telescope or binoculars onto a shaded
white screen, of with specialist solar-filter systems.  To see any
flares, filaments and plaging, H-alpha filter systems will be needed.
A picture of the sunspot can be seen on the Solar link from the SPA
website, under News.  No attempt must be made to see it by looking
directly at the Sun, as permanent eye damage could result.


COMET SECTION NEWS
By Jonathan Shanklin, Comet Section Director

The remains of comet 2010 X1 (Elenin) have been recovered after
perihelion by a Spanish observer, working at a remote mountain
location in the Cantabrian Mountains.  The comet was probably a small
object as it had a faint absolute magnitude, and as it approached
perihelion it was seen to become more diffuse and fade.  In October,
over a month after perihelion, Juan Gonzalez detected a cloud of
material in the expected location, though his observations were
doubted by many Internet 'experts'.  They believed that it had
completely disintegrated, and when no object could be detected by deep
imaging, they poured scorn on the visual observation.  They should
have remembered history.  Similar scorn was heaped on George Alcock
when he drew intricate tail detail, but newer technology showed that
his visual observations were correct.  The long-exposure photographs
of the mid-twentieth century had simply blurred out the structure.  In
the case of the recent disputed observation, amateur wide-field CCD
imaging was able (after a few days) to provide the proof that the
visual observation was correct.  A superb image taken remotely by
Rolando Ligustri showed a diffuse cloud of material representing the
disintegrated comet.  The lesson is that visual observation still has
a part to play in scientific discovery.

There is a comet that is well placed for observation if you want to
see what one looks like.  From light-polluted city skies comet 2009 P1
(Garradd) is not easy in binoculars, but in darker rural skies you get
a more impressive view.  Observations so far show it to have a small,
moderately condensed coma about 4 or 5 minutes of arc in diameter, but
from my urban location I have not been able to see anything of a tail.
Its brightness has not changed much over the last month, as its
decreasing distance from the Sun is balanced by its increasing
distance from us.  The comet will reach perihelion at 1.6 AU just
before Christmas, but it is then 2 AU from the Earth.  It should be
around 7th magnitude, much as it is at the moment.  In the new year it
will be receding from the Sun, but our distance from it is decreasing,
and the comet could become a little brighter.  The comet is nearly
stationary in southern Hercules in November, but then accelerates
northwards, though it is still in Hercules at the end of the year.

http://www.ast.cam.ac.uk/~jds/


PLANETS
By Andrew Robertson, SPA Planetary Section Director

MERCURY reaches eastern elongation on the 14th (23°) but being at only
4° altitude at sunset is effectively unobservable from the UK.

VENUS is only slightly better placed, being at 6° altitude at sunset
on the 14th, but as it is magnitude -3.9 (compared to Mercury's -0.2)
there is a good chance of locating it towards the end of the month
just after sunset in the SSW when it will be 8° altitude, provided
you have a clear sky and horizon.

MARS is an early-morning object.  By mid-month at the end of
astronomical dark (0515 UT) it is at 47° altitude in the SSE shining
at magnitude 1.0 in Leo, near to Regulus which being a blue-white star
of magnitude 1.4 will make a pleasant pairing.

JUPITER is still king of the planets, having just passed opposition on
October 29 and shining at magnitude -2.8.  It is observable most of
the night.  Displaying a diameter of 49" it shows a wealth of detail
even in a small telescope, and I have been receiving lots of images
and sketches from SPA members.

Any reports of observations would be most welcome via:
http://popastro.com/planet/contact/

You can see a selection of members' images/sketches at:
http://snipurl.com/12a79y



ASTEROID 2005 YU55 TO APPROACH THE EARTH ON 2011 NOVEMBER 8
NASA

Near-Earth asteroid 2005 YU55 will pass within 0.85 lunar distances
of the Earth on November 8.  The close approach of this 400-metre
C-type asteroid presents an excellent opportunity for optical, near-
infrared and radar observations.  On November 8 and 9 the object will
reach visual magnitude 11 and should be easily visible in modest
telescopes.  The closest approach to the Earth and the Moon will be
respectively 0.00217 AU and 0.00160 AU on November 8 at 23:28 and
November 9 at 07:13 UT.  Discovered on 2005 December 28 by the
Spacewatch Program, the object has been previously observed with the
Arecibo radar in 2010 and shown to be a very dark, nearly spherical
object 400 metres in diameter.  As well as aiding the interpretation
of the radar observations, visual and near-infrared observations could
define the object's rotational characteristics and provide constraints
on the nature of the object's surface roughness and mineral
composition.  Since the asteroid will approach the Earth from the
Sunward direction, it will be a daylight object until the time of
closest approach.  Although classified as a potentially hazardous
object, 2005 YU55 poses no threat of an Earth collision over at least
the next 100 years.  However, this will be the closest approach to
date by an object of such a large size that we know about in advance,
and (as far as is known) such an event will not happen again until
2028 when asteroid (153814) 2001 WN5 will pass to within 0.6 lunar
distances.


ERIS IS PLUTO'S TWIN
ESO

Eris is one of the largest trans-Neptunian 'Kuiper-Belt' objects in
the outer Solar System; it was discovered in 2005, and its discovery
was one of the factors that led to the adoption by the IAU of a new
class of objects called dwarf planets and the re-classification of
Pluto from planet to dwarf planet in 2006.  Eris is currently three
times further from the Sun than Pluto.  In 2010 November, it occulted
a faint background star; such occurrences are rare and difficult to
observe, as Eris is so distant and its angular diameter is so small.
Occultations provide the most accurate, and often the only, way to
measure the shape and size of a distant Solar-System body.
Observations were attempted from 26 locations around the globe,
including several telescopes at amateur observatories, on the
predicted path of the shadow, but only at two sites, both in Chile, at
one of which there were two telescopes, was an actual occultation
observed.  The combined observations from the two Chilean sites are
consonant with a model of Eris that is close to spherical.

While earlier observations by other methods suggested that Eris was
probably about 25% larger than Pluto, with an estimated diameter of
3000 km, the new study indicates that the two objects are pretty well
the same size.  Eris's newly determined diameter stands at 2326 km,
with an accuracy assessed at 12 km -- but that is valid only on the
assumption that the object is a sphere.  Pluto has a diameter
estimated to be between 2300 and 2400 km.  Pluto's diameter is harder
to measure because of the presence of an atmosphere, albeit very
tenuous, which creates ambiguities in the understanding of occultation
light-curves.

The motion of Eris's satellite Dysnomia enables the mass of Eris to be
determined; it is 27% greater than that of Pluto.  Together, its mass
and diameter give its density as 2.52 times that of water, implying
that Eris is probably a rocky body covered in a rather thin mantle of
ice.  The surface of Eris appears to be extremely reflective,
reflecting 96% of the light that falls on it (a visible albedo of
0.96 -- brighter even than fresh snow), making Eris one of the most
reflective objects in the Solar System, along with Saturn's icy moon
Enceladus.  The bright surface of Eris is most likely composed of a
nitrogen-rich ice mixed with frozen methane, whose presence is
suggested by the spectrum, coating the surface in a thin and very
reflective icy layer less than 1 mm thick.  The layer of ice could
result from a nitrogen/methane atmosphere having condensed as frost
onto the surface as Eris moved away from the Sun in its elongated
orbit into an increasingly cold environment.  The temperature of the
surface of Eris facing the Sun is estimated to be -238 C at most, and
even lower on the night side.  The ice could turn back to gas as Eris
approaches its closest point to the Sun.


COMET STORM IN A NEARBY STAR SYSTEM
NASA

Astronomers using the Spitzer space telescope believe that they see
evidence of an ongoing 'Late Heavy Bombardment' in the 'nearby'
southern-hemisphere star system Eta Corvi, occurring at about the same
stage of formation of a planetary system as in our Solar System.
The Eta Corvi system is approximately one billion years old, which
researchers think is about the right age for such a storm.  Some
scientists think that, about 4 billion years ago, about 600 million
years after the Solar System formed, the Kuiper Belt was disturbed by
a migration of Jupiter and Saturn, and that the shift in the Solar
System's gravitational balance scattered the icy bodies in the Kuiper
Belt, ejecting the vast majority into interstellar space and producing
a lot of dust in the belt.  Some Kuiper-Belt objects, however, were
set on inward paths that crossed the orbits of the Earth and other
rocky planets.  The resulting bombardment of comets lasted until 3.8
billion years ago.  The barrage scarred our Moon and produced large
amounts of dust.  Spitzer has observed around Eta Corvi a band of dust
whose spectrum resembles that of the Almahata Sitta meteorite, which
fell to Earth in fragments across Sudan in 2008.  It is tempting to
imagine that the Eta Corvi dust band represents the remnants of an
obliterated giant comet, which might have been destroyed by a
collision with a planet or some other large body.  The dust is located
close enough to Eta Corvi that Earth-like planets could exist in the
collision zone.  A second, more massive ring of colder dust located
further out in the Eta Corvi system could be interpreted as a
reservoir of cometary bodies.  That ring, discovered in 2005, matches
the size of the region in the Solar System known as the Kuiper Belt,
where icy and rocky left-overs from planet-formation linger.  The
comets of Eta Corvi, and the Almahata Sitta meteorite, may have each
originated in the Kuiper Belts of their respective star systems.


BLUE STRAGGLERS IN NGC 188
Northwestern University

A consortium of astronomers led from Wyoming has published a study of
the old open star cluster NGC 188, which is to be found in Cepheus
only 5° from the celestial North Pole.  The cluster has around 3,000
stars, all about the same age.  In the ordinary course of their
evolution, stars burn out, starting from the brightest and most
massive ones which burn up their hydrogen much more quickly than those
of modest mass.  In most cases they finish up by ejecting much of
their mass, leaving behind the compact stellar core as a white dwarf.
In NGC 188, as in many other clusters, we see a few stars that seem
anomalously young, blue and bright, ones that according to the age of
the cluster ought to have burnt up and become white dwarfs by now.
They are known as 'blue stragglers', and are unusually abundant in
NGC 188, which includes 21 of them.  It was recognised in the 1960s by
W. H. (later Sir William) McCrea that blue stragglers arise from
binary-star systems in which the less-massive star collects the
expelled envelope of its companion in the final stages of the latter's
evolution, and thereby becomes an object that is more massive -- and
accordingly burns brighter and bluer -- than any of the stars that are
evolving normally as single objects in the cluster.  The stripped core
of the formerly more-massive star remains as a white dwarf, still in
orbit with the rejuvenated blue straggler.  The orbital periods are
typically of the order of 1000 days.  The white-dwarf components of
the binaries are not actually detectable directly, being very faint,
but their existence is manifested by the orbital motion of their blue-
straggler companions.

Much of the NGC 188 data set was collected during the last decade by
the 3.5-m WIYN Telescope on Kitt Peak in Arizona, but a considerable
part was supplied from the Dominion Astrophysical Observatory in
Victoria, B.C., and a contribution was subscribed by the moderator of
these Bulletins from observations that he made in collaboration with
J. E. Gunn with their own radial-velocity spectrometer on the Palomar
200-inch reflector in the 1970s.


ANCIENT SUPERNOVA MYSTERY SOLVED
NASA

In 185 AD Chinese astronomers noted a "guest star" that appeared
in the sky and stayed for about 8 months.  By the 1960s, scientists had
recognized that the object was the first documented supernova.  Later,
they pinpointed its remnant, called RCW 86, located about 8,000
light-years away.  The spherical remains, which cover an area of sky
larger than the Full Moon (and can be viewed online at
http://go.nasa.gov/pnv6Oy ) are larger than expected.  New infrared
observations made with Spitzer space telescope and other instruments
indicate that the event was a 'Type Ia' supernova, created by the
relatively peaceful death of a star like our Sun, which then shrank to
become a white dwarf.  The white dwarf is thought to have blown up
later as a supernova after siphoning matter from a nearby star.  The
observations also show for the first time that a white dwarf can
create a cavity around it before blowing up in a Type Ia event.
A cavity would explain why the remains of RCW 86 are so big.  When
the explosion occurred, the ejected material would have travelled
unimpeded by gas and dust and spread out quickly.


VISTA FINDS NEW GLOBULAR CLUSTERS
ESO

Two previously unknown globular clusters were found in new images from
ESO's VISTA survey telescope, adding to the total of 158 known
globular clusters in our Milky Way.  The two faint clusters are known
as VVV CL001 and VVV CL002.  This small and faint grouping may also be
the globular clusters that are the closest known to the centre of the
Milky Way.  As well as globular clusters, VISTA is finding many open,
or 'galactic'. clusters, which generally contain fewer, younger, stars
than globular clusters and are far more common.  Another newly
announced cluster, VVV CL003, seems to be an open cluster that lies in
the direction of the Galactic centre, but much further away, about
15000 light-years beyond the centre.  It is the first such cluster to
be discovered on the far side of the Milky Way.  The newly found
clusters are so faint that it is no wonder that they have remained
un-discovered until now.  Because of the absorption of visible
starlight by interstellar dust, such objects can be seen only in
infrared light.


HOW MILKY WAY KILLED OFF SATELLITE GALAXIES
RAS

Researchers have noticed for the first time the existence of a new
signature of the birth of the first stars in our Galaxy.  More than 12
billion years ago, the intense ultraviolet light from those stars
dispersed the gas of our Galaxy's nearest companions, virtually
putting a halt to their ability to form stars and consigning them to a
dim future.  That explains why some galaxies were killed off, while
stars continued to form in more distant objects.  The first stars of
the Universe appeared about 150 million years after the Big Bang.
Back then, the hydrogen and helium gas filling the Universe was cold
enough for its atoms to be electrically neutral.  As the ultraviolet
light of the first stars propagated through the gas, it broke apart
the proton--electron pairs that make up hydrogen atoms, returning them
to the so-called plasma state in which they existed in the first
moments of the Universe.  That process, known as re-ionization, also
resulted in significant heating, which had dramatic consequences --
the gas became so hot that it escaped the weak gravity of the galaxies
of lowest mass, thereby depriving them of the material needed to form
stars.

The process appears to explain the small number and large ages of the
stars seen in the faintest dwarf-galaxy satellites of the Milky Way,
and why galaxies like the Milky Way have so few satellites around
them.  The model appears to match observations of our Galaxy and its
neighbourhood and suggests that the first stars of our Galaxy played a
major role in the photo-evaporation of the satellite galaxies' gas.
It is not large nearby galaxies but our own that caused the demise of
its tiny neighbours, evaporating them through its intense radiation.


COMPLEX CARBON COMPOUNDS EXIST THROUGHOUT THE UNIVERSE
University of Hong Kong

Astronomers at the University of Hong Kong have shown that a substance
commonly found throughout the Universe contains a mixture of component
molecules having many carbon atoms in both 'aromatic' (benzene-ring)
and 'aliphatic' (chain-like) arrangements.  The compounds are so
complex that their chemical structures resemble those in coal and
petroleum.  Since coal and oil are remnants of ancient life, such
matter was thought to arise only from living organisms, but the team's
discovery suggests that complex carbon compounds can be synthesized in
space even in the absence of life forms.

The researchers investigated a set of infrared emissions detected in
stars, interstellar space, and galaxies -- spectral signatures known
as 'unidentified infrared emission features'.  The features have been
supposed to come from simple molecules made of carbon and hydrogen
atoms, called polycyclic aromatic hydrocarbon (PAH) molecules.  From
observations taken by the Infrared Space Observatory and Spitzer, the
observers show that the spectra cannot be explained by PAH molecules
but must arise from chemical structures that are much more complex.
>From spectra of novae, they show that stars can make such complex
compounds on extremely short time scales (weeks).  Not only are stars
producing such matter, but they are also ejecting it into interstellar
space in the form of what astronomers call dust.  The work supports
an earlier idea that old stars can act as molecular factories.
Interestingly, the compounds in star dust are somewhat similar to some
found in meteorites, so they must have been present in the early Solar
System, of which many meteorites are thought to be relics.

Bulletin compiled by Clive Down and moderated by Professor Roger Griffin

(c) 2011 the Society for Popular Astronomy

Telescope finds fewer asteroids near Earth

News item from SPA 

New observations by the Wide-field Infrared Survey Explorer (WISE) indicate that there are significantly fewer near-Earth asteroids in the mid-size range than previously thought. 

WISE scanned the entire celestial sky twice in infrared light between 2010 January and 2011 February.  It observed more than 100,000 asteroids in the main belt between Mars and Jupiter, in addition to at least 585 'near-Earth' ones. 

It observed in the infrared, detecting objects by their heat rather than by reflected light, and is supposed to have taken a more accurate census of the asteroid population than previous visible-light surveys which were affected by the differing albedos of asteroids. 

The WISE data suggest that more than 90% of the largest near-Earth asteroids (1 km or larger), which would have global consequences if they were to strike the Earth, have been found.

It is believed that all near-Earth asteroids as much as 10 kilometres across, as big as the one that is thought to have wiped out the dinosaurs, are now known.

The new estimate for the number of mid-sized near-Earth asteroids, about 20,000, is lower than the 35,000 previously suggested.  However, the majority of mid-size asteroids remains to be discovered.

The Moon's role in trying to find Neutrinos

Just came across this - thought it was interesting. Love the image too.

Full credit:
Radio astronomers get an assist from the Moon. Credit: Ted Jaeger, University of Iowa, NRAO/AUI/NSF

New Comet Ikeya-Murakami

I don;t have much time right now, so here's a quick bulletin from the SPA. 

NEW COMET IKEYA-MURAKAMI:
Spaceweather.com

Newly-discovered comet C/2010 V1 (Ikeya-Murakami) is putting on a good
show for anyone with a telescope and an alarm clock.  The comet is
rapidly changing, and the shape of its atmosphere is similar to that
of Comet Holmes after it had an outburst in 2007.  Indeed, Comet
Ikeya-Murakami seems likely to be experiencing a similar event.  It
has been in the far reaches of the Solar System for a very long time,
but has been falling in towards the Sun, to which it made its closest
approach (1.7 AU) in late October, so it has recently been receiving a
dose of solar heating.  The various automated search programmes that
have taken so much of the fun (or at least success) out of old-
fashioned comet-hunting in recent years, finding comets of the
twentieth magnitude that nobody can see, did not discover this one.
It was two Japanese amateurs, looking through their respective
telescopes, who discovered it, after perihelion and already at about
its present brightness; if it had been of a comparable brightness for
months before, it could be expected to have been discovered sooner,
although it has been approaching from behind the Sun.  Ikeya was the
first to see it; his name is familiar from his discovery 45 years ago
of the Sun-grazing Comet Ikeya-Seki, one of the most spectacular
comets of the 20th century.

Amateur astronomers are encouraged to monitor developments.  Various
reports put the brightness of the comet between 7th and 9th magnitude,
invisible to the naked eye but easy to see in telescopes and likely to
be visible even binoculars.  It is easy to find, in the eastern sky
before dawn, a degree or so south of Saturn this morning and moving
slowly south-east more or less parallel to the ecliptic, a little
less than one degree a day.



Bulletin compiled by Clive Down


(c) 2010 the Society for Popular Astronomy

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Planck telescope reveals - the universe

This is just amazing!

http://news.bbc.co.uk/1/hi/science_and_environment/10501154.stm