Cassopeia A is a supernova remnant some 11,000 light years away. Turning the attention of the Spitzer Space Telescope on this object allows us to examine the different elements within it, a useful exercise because it helps to answer a question about the early universe: Where did the interstellar dust so essential for the formation of stars and planets — not to mention the creatures that live on planets like ours — come from?
Despite the ubiquity of space dust, the question has persisted because the first stars, so-called Population III, are the only ones to have formed without dust. We can see dust being pumped out by dying solar-type stars in the nearby universe, but in the infancy of the cosmos, such stars weren’t old enough to perform the job. So massive Population III stars are thought to have contributed dust in their violent death as supernovae, a theory in support of which Cassiopeia A provides data.
Jeonghee Rho (Spitzer Science Center, Caltech) seems certain of the result: “Now we can say unambiguously that dust – and lots of it – was formed in the ejecta of the Cassiopeia A explosion. This finding was possible because Cassiopeia A is in our own galaxy, where it is close enough to study in detail.” That’s helpful to know, but it doesn’t limit dust formation to supernovae alone. Other avenues exist for dust formation, including highly energetic black holes, whose role remains to be clarified.
Image (click to enlarge): The upper left panel is a composite made up of three infrared views shown in the remaining panels. The bottom left view shows argon gas (green) that was synthesized as it was ejected from the star. The bottom right view shows a collection of dust (red), including proto-silicates, silicate dioxide and iron oxide. The fact that these two features line up (as seen in yellow in the combined view) tells astronomers that the dust, together with the gas, was created in the explosion. The upper right panel shows silicon gas (blue) deep in the interior of the remnant. This cooler gas, called the unshocked ejecta, was also synthesized in the supernova blast. Credit: NASA/JPL-Caltech.
The mapping of Cassopeia A generates data on proto-silicates, silicon dioxide, iron oxide, pyroxene, carbon, aluminium oxide and other compounds. A close match between dust and ejecta expelled in the explosion ties the formation of the dust to the stellar blast. Rho’s team believes the dust would form days to months after the explosion, when the temperature of the gas in the ejecta has had the chance to cool. And although enough dust to form 10,000 Earths has been located in Cassopeia A, the quantity involved still doesn’t completely explain early dust formation, though it comes close. As the paper notes, “The freshly formed dust mass derived from Cas A is sufficient from SNe [supernovae] to explain the lower limit on the dust masses in high redshift galaxies.”
Next for such work: Studies of other supernovae at a range of distances, and better models for understanding how dust is destroyed. The paper is Rho et al., “Freshly Formed Dust in the Cassiopeia A Supernova Remnant as Revealed by the Spitzer Space Telescope,” accepted by The Astrophysical Journal (abstract).
Probing Interstellar Dust With Space-Based Coronagraphs
Authors: N. J. Turner, K. Grogan, J. B. Breckinridge
(Submitted on 14 Jan 2008)
Abstract: We show that space-based telescopes such as the proposed Terrestrial Planet Finder Coronagraph will be able to detect the light scattered by the interstellar grains along lines of sight passing near stars in our Galaxy.
The relative flux of the scattered light within one arcsecond of a star at 100 pc in a uniform interstellar medium of 0.1 H atoms cm^-3 is about 10^-7. The halo increases in strength with the distance to the star and is unlikely to limit the coronagraphic detection of planets around the nearest stars.
Grains passing within 100 AU of Sun-like stars are deflected by radiation, gravity and magnetic forces, leading to features in the scattered light that can potentially reveal the strength of the stellar wind, the orientation of the stellar magnetic field and the relative motion between the star and the surrounding interstellar medium.
Comments: Accepted for publication in ApJ Supplements
Subjects: Astrophysics (astro-ph)
Cite as: arXiv:0801.2177v1 [astro-ph]
Submission history
From: N. J. Turner [view email]
[v1] Mon, 14 Jan 2008 22:59:41 GMT (122kb)
http://arxiv.org/abs/0801.2177
Interstellar dust evolution in galaxies of different morphological types
Authors: F. Calura (1), A. Pipino (2,3), F. Matteucci (1,3)- ((1) INAF-Oss. Astronomico di Trieste, Italy; (2) Astrophysics, Oxford University, UK; (3) Dip. di Astronomia, Universita’ di Trieste, Italy)
(Submitted on 16 Jan 2008)
Abstract: We study interstellar dust evolution in various environments by means of chemical evolution models for galaxies of different morphological types. We start from the formalism developed by Dwek (1998) to study dust evolution in the solar neighbourhood and extend it to ellipticals and dwarf irregular galaxies, showing how the evolution of the dust production rates and of the dust fractions depend on the galactic star formation history. The observed dust fractions observed in the solar neighbourhood can be reproduced by assuming that dust destruction depends the condensation temperatures T_c of the elements. In elliptical galaxies, type Ia SNe are the major dust factories in the last 10 Gyr. With our models, we successfully reproduce the dust masses observed in local ellipticals (~10^6 M_sun) by means of recent FIR and SCUBA observations. We show that dust is helpful in solving the iron discrepancy observed in the hot gaseous halos surrounding local ellipticals. In dwarf irregulars, we show how a precise determination of the dust depletion pattern could be useful to put solid constraints on the dust condensation efficiencies. Our results will be helpful to study the spectral properties of dust grains in local and distant galaxies.
Comments: 22 pages, to appear on the proceedings of “XIXemes Rencontres de Blois”
Subjects: Astrophysics (astro-ph)
Cite as: arXiv:0801.2551v1 [astro-ph]
Submission history
From: Francesco Calura [view email]
[v1] Wed, 16 Jan 2008 18:53:10 GMT (160kb)
http://arxiv.org/abs/0801.2551
A Nova Doesn’t Create, It Destroys
Written by Fraser Cain
Astronomers used to think that brief stellar eruptions
called novae generated massive amounts of dust. But
new observations of a well known nova system called
RS Ophiuchus shows that isn’t the case. The dust was
there already, and a nova blast just clears it all away.
The discovery was made using the massive Keck
Interferometer, where the two 10-metre (33 feet)
Keck telescopes on Hawaii’s Mauna Kea are merged
together into a single super-telescope. It’s not like
some kind of Japanese anime robot linking together;
the telescopes just sit there. All the merging is done
behind the scenes, through optics, electronics, and
computers.
Full article here:
http://www.universetoday.com/2008/01/28/a-nova-doesnt-create-it-destroys/
Supernovae and Cosmology
Authors: Bruno Leibundgut
(Submitted on 28 Feb 2008)
Abstract: The extreme luminosity and their fairly unique temporal behaviour have made supernovae a superb tool to measure distances in the universe. As complex astrophysical events they provide interesting insights into explosion physics, explosive nucleosynthesis, hydrodynamics of the explosion and radiation transport. They are an end product of stellar evolution and provide clues to the stellar composition. Since they can be observed at large distances they have become critical probes to further explore astrophysical effects, like dust properties in external galaxies and the star formation history of galaxies.
Some of the astrophysics interferes with the cosmological applications of supernovae. The local velocity field, distorted by the gravitational attraction of the local large scale structure, and the reddening law appear at the moment the major limitations in the accuracy with which cosmological parameters can be determined. These absorption effects can introduce a secondary bias into the observations of the distant supernovae, which needs to be carefully evaluated. Supernovae have been used for the measurement of the Hubble constant, i.e. the current expansion rate of the universe, and the accelerated cosmic expansion directly inferred from the apparent faintness of the distant supernovae.
Comments: Published in General Relativity and Gravitation, 40, 221
Subjects: Astrophysics (astro-ph)
Journal reference: Gen Relativ Gravit (2008) 40, 221
DOI: 10.1007/s10714-007-0545-9
Cite as: arXiv:0802.4154v1 [astro-ph]
Submission history
From: Bruno Leibundgut [view email]
[v1] Thu, 28 Feb 2008 09:47:14 GMT (137kb)
http://arxiv.org/abs/0802.4154
The SuperNova Early Warning System
Authors: K. Scholberg
(Submitted on 4 Mar 2008)
Abstract: A core collapse in the Milky Way will produce an enormous burst of neutrinos in detectors world-wide. Such a burst has the potential to provide an early warning of a supernova’s appearance. I will describe the nature of the signal, the sensitivity of current detectors, and SNEWS, the SuperNova Early Warning System, a network designed to alert astronomers as soon as possible after the detected neutrino signal.
Comments: 3 pages, appearing in refereed proceedings of “Hotwiring the Transient Universe 2007”, eds. A. Allan, J. S. Bloom, R. Seaman, Astron. Nachr. vol. 329, March 2008
Subjects: Astrophysics (astro-ph)
Journal reference: Astron. Nachr. / AN 329, No. 3, 337-339 (2008)
DOI: 10.1002/asna.200710934
Cite as: arXiv:0803.0531v1 [astro-ph]
Submission history
From: Kate Scholberg [view email]
[v1] Tue, 4 Mar 2008 20:01:16 GMT (80kb)
http://arxiv.org/abs/0803.0531
Action replay of powerful stellar explosion
Astronomers have made the best ever determination of
the power of a supernova explosion that was visible from
Earth long ago.
By observing the remnant of a supernova and a light echo
from the initial outburst, they have established the validity
of a powerful new method for studying supernovas.
More at:
http://www.esa.int/esaSC/SEMPIBN5NDF_index_0.html
Galactic Outflows and the pollution of the Galactic Environment by Supernovae
Authors: E.M. de Gouveia Dal Pino, C. Melioli, A. D Ercole, F. Brighenti, A. Raga
(Submitted on 26 Mar 2008)
Abstract: We here explore the effects of the SN explosions into the environment of star-forming galaxies like the Milky Way. Successive randomly distributed and clustered SNe explosions cause the formation of hot superbubbles that drive either fountains or galactic winds above the galactic disk, depending on the amount and concentration of energy that is injected by the SNe. In a galactic fountain, the ejected gas is re-captured by the gravitational potential and falls back onto the disk.
From 3D nonequilibrium radiative cooling hydrodynamical simulations of these fountains, we find that they may reach altitudes up to about 5 kpc in the halo and thus allow for the formation of the so called intermediate-velocity-clouds (IVCs) which are often observed in the halos of disk galaxies.
The high-velocity-clouds that are also observed but at higher altitudes (of up to 12 kpc) require another mechanism to explain their production. We argue that they could be formed either by the capture of gas from the intergalactic medium and/or by the action of magnetic fields that are carried to the halo with the gas in the fountains.
Due to angular momentum losses to the halo, we find that the fountain material falls back to smaller radii and is not largely spread over the galactic disk. Instead, the SNe ejecta fall nearby the region where the fountain was produced, a result which is consistent with recent chemical models of the galaxy. The fall back material leads to the formation of new generations of molecular clouds and to supersonic turbulence feedback in the disk.
Comments: 10 pages, 5 figures; paper of invited talk for the Procs. of the 2007 WISER Workshop (World Space Environment Forum), Alexandria, Egypt, October 2007, Spa. Sci. Revs
Subjects: Astrophysics (astro-ph)
Cite as: arXiv:0803.3835v1 [astro-ph]
Submission history
From: Elisabete M. de Gouveia Dal Pino [view email]
[v1] Wed, 26 Mar 2008 22:37:33 GMT (346kb)
http://arxiv.org/abs/0803.3835
SN 1994W: a Type IIn Supernova without Core Collapse?
Authors: Luc Dessart, D. John Hillier, Suvi Gezari, Stephane Basa, Tom Matheson
(Submitted on 2 Apr 2008)
Abstract: We present a multi-epoch quantitative spectroscopic analysis of the Type IIn SN 1994W, an event interpreted by Chugai et al. as stemming from the interaction between the ejecta of a SN and a 0.4Msun circumstellar shell ejected 1.5yr before core collapse. During the brightening phase, our models suggest that the source of optical radiation is not unique, perhaps associated with an inner optically-thick Cold Dense Shell (CDS) and outer optically-thin shocked material. During the fading phase, our models support a {\it single} source of radiation, an hydrogen-rich optically-thick layer with a near-constant temperature of ~7000K that recedes from a radius of 4.3×10^15 at peak to 2.3×10^15 cm 40 days later.
We reproduce the hybrid narrow-core broad-wing line profile shapes of SN 1994W at all times, invoking an optically-thick photosphere exclusively (i.e., without any external optically-thick shell). In SN 1994W, slow expansion makes scattering with thermal electrons a key escape mechanism for photons trapped in optically-thick line cores, and allows the resulting broad incoherent electron-scattering wings to be seen around narrow line cores. In SNe with larger expansion velocities, the thermal broadening due to incoherent scattering is masked by the broad profile and the dominant frequency redshift occasioned by bulk motions.
We speculate that, given the absence of broad lines at all times and the very low 56Ni yields, SN 1994W may be the result of an interaction between two ejected shells with no core collapse.
Comments: 34 pages (includes online tables), 16 figures, paper submitted to MNRAS, high-resolution paper avaialable at this http URL
Subjects: Astrophysics (astro-ph)
Cite as: arXiv:0804.0428v1 [astro-ph]
Submission history
From: Luc Dessart [view email]
[v1] Wed, 2 Apr 2008 20:18:14 GMT (534kb)
http://arxiv.org/abs/0804.0428
Scattered-Light Echoes from the Historical Galactic Supernovae Cassiopeia A and Tycho (SN 1572)
Authors: A. Rest, D. L. Welch, N. B. Suntzeff, L. Oaster, H. Lanning, K. Olsen, R. C. Smith, A. C. Becker, M. Bergmann, P. Challis, A. Clocchiatti, K. H. Cook, G. Damke, A. Garg, M. E. Huber, T. Matheson, D. Minniti, J. L. Prieto, W. M. Wood-Vasey
(Submitted on 29 May 2008)
Abstract: We report the discovery of an extensive system of scattered light echo arclets associated with the recent supernovae in the local neighbourhood of the Milky Way: Tycho (SN 1572) and Cassiopeia A. Existing work suggests that the Tycho SN was a thermonuclear explosion while the Cas A supernova was a core collapse explosion. Precise classifications according to modern nomenclature require spectra of the outburst light.
In the case of ancient SNe, this can only be done with spectroscopy of their light echo, where the discovery of the light echoes from the outburst light is the first step. Adjacent light echo positions suggest that Cas A and Tycho may share common scattering dust structures. If so, it is possible to measure precise distances between historical Galactic supernovae.
On-going surveys that alert on the development of bright scattered-light echo features have the potential to reveal detailed spectroscopic information for many recent Galactic supernovae, both directly visible and obscured by dust in the Galactic plane.
Comments: 4 pages, 4 color figures, accepted for publication in ApJL
Subjects: Astrophysics (astro-ph)
Cite as: arXiv:0805.4607v1 [astro-ph]
Submission history
From: Armin Rest [view email]
[v1] Thu, 29 May 2008 19:28:29 GMT (899kb)
http://arxiv.org/abs/0805.4607
Legendary “royal star” was an actual supernova
By Alasdair Wilkins, Apr 18, 2011 04:00 PM
In 1660, Britain restored the monarchy after a decade of Oliver Cromwell’s puritanical dictatorship. Charles II’s supporters pointed out that his birth was marked by a glorious noon-day star, proving his divine right to rule…and that wasn’t necessarily just propaganda.
Royalist pamphleteer Edward Matthew offered this predictably flowery description of the star in 1661, the year of Charles II’s coronation:
“The Most Glorious Star… shining most brightly in a Miraculous manner in the Face of the Sun. Never any Starre [had] appeared before at the birth of any (the Highest humane Hero) except our Saviour.”
Yes, this “royal star” pretty much proved Charles II was only a notch below Jesus. Under those circumstances, a country would be crazy to not make him king, right? Considering Charles’s father, Charles I, had been kicked off the throne and decapitated in 1649, this royal star was just the sort of spectacular proof the United Kingdom needed to accept Charles II’s renewed claim to the throne.
It seems like far too good a story to be true, and historians have generally dismissed it as just royalist propaganda, particularly considering it only becomes a significant part of Charles II’s biography thirty years after it supposed happend. But now Martin Lunn, the former curator of astronomy at England’s Yorkshire Museum, thinks he’s found evidence that this royal star really did exist, and it was actually a rather well-timed supernova.
Specifically, Lunn points to Cassiopeia A, a massive star that exploded about 11,000 light-years away, with the light of the explosion finally reaching Earth in the 1600s. These days, Cassiopeia A is no longer visible to the naked eye, as it’s now just a faint X-ray source.
Full article here:
http://m.io9.com/5793260/legendary-royal-star-was-an-actual-supernova
To quote:
“A lot more attention should be paid to archival collections from the 1630s, not just in Britain, but in countries around the world. Researchers out there might be coming across references to this star and not realize its potential astronomical significance. I see our role as adding new evidence to the impressive and important body of work already done, and hopefully getting the scientific community to reconsider some of their assumptions about their dating method.”