Posted on by Nancy Atkinson

Has a Recent, Nearby Supernova Become a Baby Black Hole?

This composite image shows a supernova within the galaxy M100 that may contain the youngest known black hole in our cosmic neighborhood. Credits: X-ray: NASA/CXC/SAO/D.Patnaude et al, Optical: ESO/VLT, Infrared: NASA/JPL/Caltech

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Back in 1979, amateur astronomer Gus Johnson discovered a supernova about 50 million light years away from Earth, when a star about 20 times more massive than our Sun collapsed. Since then, astronomers have been keeping an eye on SN 1979C, located in M 100 in the Virgo cluster. With observations from the Chandra telescope, the X-ray emissions from the object have led astronomers to believe the supernova remnant has become a black hole. If so, it would be the youngest black hole known to exist in our nearby cosmic neighborhood and would provide astronomers the unprecedented opportunity to watch this type of object develop from infancy.

“If our interpretation is correct, this is the nearest example where the birth of a black hole has been observed,” said astronomer Daniel Patnaude during a NASA press briefing on Monday. Patnaude is from the Harvard-Smithsonian Center for Astrophysics and is the lead author of a new paper.


SN 1970C belongs to a type of supernova explosions called Type II linear, or core collapse supernovae, which make up about 6% of known stellar explosions. While many new black holes in the distant universe previously have been detected in the form of gamma-ray bursts (GRBs), SN 1979C is different because it is much closer and core collapse supernovae are unlikely to be associated with a GRB. Theories say that most black holes should form when the core of a star collapses and a gamma-ray burst is not produced, but this may be the first time that this method of making a black hole has been observed.

There has been a debate on what size star will create a black hole what size will create a neutron star. The 20 solar mass size is right on the boundary between the two, so astronomers are not completely sure this is a black hole or a neutron star. But since the X-ray emissions from this object have been steady over the past 31 years, astronomers believe this is a black hole, since as a neutron star cools, the X-ray emissions fade.

This animation shows how a black hole may have formed in SN 1979C. The collapse of a massive star is shown, after it has exhausted its fuel. A flash of light from a shock breaking through the surface of the star is then shown, followed by a powerful supernova explosion. The view then zooms into the center of the explosion: Credits: NASA/CXC/A.Hobart

However, as a caveat, co-author Avi Loeb said, it really takes about a lot longer than 31 years to see big changes, but he said the fact that the illumination has been steady gives evidence for a black hole.

Although the evidence does point to a newly formed black hole, there are a few other possibilities of what it could be. Some have suggested the object could be a magnetar or a blast wave, but the evidence is showing those two options are not very probable.

Another intriguing possibility is that a young, rapidly spinning neutron star with a powerful wind of high energy particles could be responsible for the X-ray emission. This would make the object in SN 1979C the youngest and brightest example of such a “pulsar wind nebula” and the youngest known neutron star. The Crab pulsar, the best-known example of a bright pulsar wind nebula, is about 950 years old.

“I’m excited about this discovery regardless if it turns out to be black hole or a pulsar wind nebula,” said astrophysicst Alex Fillipenko, who participated in the briefing. “A pulsar wind nebula would be interesting because it would be the youngest known in that category.”

“What is really exciting is that for the first time we know the exact birth date of this object,” said Kim Weaver, an astrophycisict from Goddard Space Flight Center, “We know it is very young and we want to watch how the system evolves and changes, as it grows into a child and becomes a teenager. More importantly, we’ll be able to understand the physics. This is a story of science in action.”

The age of the possible black hole is, of course, based on our vantage point. Since the galaxy is 50 million light years away, the supernova occurred 50 million years ago. But for us, the explosion took place just 31 years ago.

Read the team’s paper: Evidence for a Black Hole Remnant in the Type IIL Supernova 1979C
Authors: D.J. Patnaude, A. Loeb, C. Jones.

Source: NASA TV briefing, NASA

Posted on by Jon Voisey

Spectroscopy in 1881

Instrument for imaging solar spectra on photographic plate. Also contains electric arc lamp which can be focused above solar spectra to allow for comparison.

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Presently, I’ve been reading a lot of very old papers and books in astronomy. The work I’m currently reading a portion of, is from 1881, and is a summary of all the findings of the year in all fields of Science. For those that aren’t familiar with that time period in astronomy, the big thing was spectroscopy. It was only ~30 years earlier that chemists and astronomers had begun to work out methods by which to investigate spectra and with the newly developed tools in hand, astronomers were pointing them at anything they could find sufficiently bright to get a spectra. Obviously, this meant the first target was the Sun. This work provides an interesting snapshot at a developing era in astronomical history.

The article describes a brief bit of background, noting that the pioneering work of spectroscopy was done by Fraunhofer, Kirchoff, Angstrom, and Thalen (but manages to leave out Kirchoff’s colleague, Robert Bunsen!). These early explorers noted that, although spectral lines may appear unique, several had lines that would appear in very nearly the same positions.

Another discovery around that time was the phenomenon of emission lines from the Sun’s corona. This had officially been discovered in 1868 during a solar eclipse, but now that astronomers knew about the occurrence, they began to explore it further and discovered that many of the features had no apparent explanation as the chemicals causing them had yet to be discovered on Earth. Incidentally, it would be a year following this publication that helium, one of the chief components of the Sun, would be found and isolated on Earth.

As the astronomers explored the corona, they inspected the various layers and found a bizarre thing: Magnesium appeared higher in the corona than sodium despite magnesium having a higher atomic weight which astronomers realized, should cause it to sink. While this is not explained, I should note that spectra often play tricks like this. It may well have been that magnesium simply emits better at the temperatures in that region given an overestimation of the abundance. This odd behavior, as well as the inconstant nature of the spectra on various portions of the Sun was described as “a great screw loose”.

Another portion of the paper provides another somewhat humorous snapshot of this moment in history as the writer remarks just how different the Sun is from the Earth. He states, “It was difficult to imagine a stronger difference to exist between any two masses of matter than the chemical constitution of the incandescent sun, and of the earth, which is now cooling.” He wonders if perhaps planets evolved from failed stars in which the Sun’s “immense temperature had not allowed a complex evolution of higher complex forms of chemical matter to take place”. While this may seem quaint, the periodic table had only been developed 12 years prior and the creation of heavy elements would not be well understood until the 1950’s.

Similarly, the confusion on the varying spectral lines between stars is apparent although the author shows that the answers were already being developed, although still not fully fleshed out. He cites Angstrom stating: “In increasing successively the temperature I have found that the lines of the spectra vary in intensity in an exceedingly complicated way, and consequently new lines even may present themselves if the temperature is raised sufficiently high.”

In this single flash of insight, Angstrom had predicted a methodology by which astronomers could have begun to classify stars. Unfortunately, the standard of classification had already been set and it would take until the next century for astronomers to begin classifying stars by temperature (thanks to the work of Annie Jump Cannon). However, the author demonstrates that investigation was underway as to the relationship between temperature and line intensity. This work would eventually connect to our modern understanding of stellar temperatures.

Posted on by Mike Simonsen

The Furor over FUORs

FU Orionis and its associated nebula. Image cedit: ESO

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In 1937, an ordinary 16th magnitude star in the constellation Orion began to brighten steadily. Thinking it was a nova, astronomers were astounded when the star just kept getting brighter and brighter over the course of a year. Most novae burst forth suddenly and then begin to fade within weeks. But this star, now glowing at 9th magnitude, refused to fade. Adding to the puzzle, astronomers could see there was a gaseous nebula nearby shining from the reflected light of this mysterious star, now named FU Orionis. What was this new kind of star?

FU Ori has remained in this high state, around 10th magnitude ever since. Because this was a form of stellar variability never seen before and there were no other examples of this behavior, astronomers were forced to learn what they could from the only known example, or wait for another event to provide more clues.

Finally, more than 30 years later, FU Ori-like behavior appeared again in 1970 when the star now known as V1057 Cyg increased in brightness by 5.5 magnitudes over 390 days. Then in 1974, a 3rd example was discovered when V1515 Cyg rose from 17th magnitude to 12th magnitude over an interval lasting years. Astronomers began piecing the puzzle together from these clues.

FU Orionis stars, commonly called FUOrs, are pre-main sequence stars in the early stages of stellar development. They have only just formed from clouds of dust and gas in interstellar space, which occur in active star- forming regions. They are all associated with reflection nebulae, which become visible as the star brightens.

This artist's concept shows a young stellar object and the whirling accretion disk surrounding it. NASA/JPL-Caltech

Astronomers are interested in these systems because FUOrs may provide us with clues to the early history of stars and the formation of planetary systems. At this early stage of evolution, a young stellar object (YSO) is surrounded by an accretion disk, and matter is falling onto the outer regions of the disk from the surrounding interstellar cloud. Thermal instabilities, most likely in the inner portions of the accretion disk, initiate an outburst and the young star increases its luminosity. Our Sun probably went through similar events as it was developing.

One of the major challenges in studying FU Orionis stars is the relatively small number of known examples. Although approximately 20 FU Orionis candidates have been identifed, only a handful of these stars have been observed to rise from their pre-outburst state to their eruptive state.

Now, in the last year, several new FUOrs have been discovered. In November 2009, two newly discovered objects were announced. Patrick Wils, John Greaves and the Catalina Real-time Transient Survey (CRTS) collaboration had discovered them in CRTS images.

The first of these objects appeared to coincide with the infrared source IRAS 06068-0641 in Monoceros. Discovered on Nov. 10, it had been continuously brightening from at least early 2005, when it was magnitude 14.8, to its present 12.6 magnitude. A faint cometary reflection nebula was visible to the east. A spectrum taken with the SMARTS 1.5-m telescope at Cerro Tololo, on Nov. 17, confirmed it to be a YSO. The object lies inside a dark nebula to the south of the Monocerotis R2 association, and is likely related to it.

Also inside this dark nebula, a second object, coincident with IRAS 06068-0643, had been varying between mag 15 and 20 over the past few years, much like UX-Ori-type objects with very deep fades. This second object is also associated with a variable cometary reflection nebula, extending to the north.

Light curves, spectra and images can be found here.

Then, in August 2010, two new eruptive, pre-main sequence stars were discovered in Cygnus. The first object was an outburst of the star HBC 722. The object was reported to have risen by 3.3 magnitudes from May 13 to August 16, 2010. Spectroscopy reported by Ulisse Munari on August 23rd, support this object’s classification as an FU Ori star. Munari and his team reported the object at 14.04V on Aug 21, 2010.

The second object, coincident with another infrared source, IRAS 20496+4354, was discovered by K. Itagaki of Yamagata, Japan, on August 23, 2010. The object appears very faint, approximately magnitude 20, in a Digital Sky Survey image taken in 1990. Subsequent spectroscopy and photometry of this object by Munari showed that this object also has the characteristics of an FU Ori star. Munari reported the object at 14.91V on August 26, 2010.

Both these objects are now the subjects of an AAVSO observing campaign announced October 1, 2010 in AAVSO Alert Notice 425. Dr. Colin Aspin, University of Hawai’i, has requested the help of AAVSO observers in performing long-term photometric monitoring of these two new YSOs in Cygnus. AAVSO observations will be used to help calibrate optical and near-infrared spectroscopy to be obtained during the next year.

Since these stars are newly discovered, very little is known about their behavior. Their classification as FU Ori variables is based on spectroscopy, but establishing a good optical light curve and maintaining it, over the next several years, will be crucial to understanding these stars. This kind of long-term monitoring is one of the things at which amateur astronomers excel.

So after a very slow start, discoveries of new YSOs and our understanding of the dusty disk environments around them are starting to heat up. With new tools and new examples to study we are peering into the early stages of stellar and planetary formation and finding some of our models have been pretty close to the truth. We expect to find more and similar objects as new all-sky surveys begin to cover the sky, but these objects will still be relatively rare and therefore interesting, because this period in a star’s evolution is short-lived and only takes place in the active star forming regions of galaxies.

Posted on by Nancy Atkinson

Stunning Image, Heartfelt Poetry Could Become Icons of Space Age

Astronaut Tracy Caldwell Dyson reflects on the view from the ISS's Cupola. Credit: Doug Wheelock/NASA

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Undoubtedly, this picture has what it takes to become an iconic image of human spaceflight, much like Apollo 8’s Earthrise or Bruce McCandless’ untethered spacewalk. Here, astronaut Tracy Caldwell Dyson looks down at Earth from the Cupola on the International Space Station, likely reflecting on both her home and her home in space. Everyone I know who has seen this image has just melted, with a sigh that says, “Oh, wow — that is just amazing!” (It made today’s Astronomy Picture of the Day.) My initial thoughts were that this is the one of the most poetic image of human spaceflight I have ever seen. And sure enough, Stuart Atkinson (the guy who I nominate at the Poet Laureate of Space) was inspired by this image, too. He has written a magnificent, heartfelt poem that captures the spirit –as well as the technology — of this image, and very likely sums up Caldwell Dyson’s thoughts as she gazes out the Cupola windows.

Read “Blue” by Stuart Atkinson:

BLUE

Ignoring the tsunami of technology humming behind her,
The chaos of cameras, computers and calculators
Covering the walls, she shuts her eyes and smiles.
This isn’t what she imagined as a girl.
In all those classroom daydreams she always saw herself
Looking down – or up – at the world from high above – or below –
Beside a plate-sized portal, straining to glimpse
Some small portion of the planet spinning silently beyond
The scratched and fingerprint-smeared glass, unable to see
More than mere hints of the colours, shadows and shapes
Shown in all the books and magazines…

But this…

Earth is there… everywhere…
A ball of burning blue close enough to touch.
Painted on the heavens in all its Van Gogh glory
It fills the sky, overflows her sight,
A startling Stargate of colour in an ocean of emptiness.
Even with her eyes closed she still sees its azure glow,
Feels its sapphire shades blazing in the ink-black night.
In the work-day-over darkness, Earthlight
Washes her face like cool rain as painfully beautiful
Whirls and whorls of milk-white cloud swirl
O’er the world below and she knows, in her aching
Heart, that long after she has returned to Terra,
To walk barefoot on its dew-drenched grass and
Splash in its ocean’s surging surf a part of her
Will always be here, at this window, gazing down
Upon the Earth.

© Stuart Atkinson 2010

Thanks to Stu for allowing us to publish his poem, a Universe Today exclusive! To see more of his poetry and imagery, check out his websites, Cumbrian Sky, and Road to Endeavour.

Posted on by Nancy Atkinson

Carnival of Space #177

This week’s Carnival of Space is hosted by Brian Wang over at Next Big Future.

Click here to read the Carnival of Space #177.

And if you’re interested in looking back, here’s an archive to all the past Carnivals of Space. If you’ve got a space-related blog, you should really join the carnival. Just email an entry to [email protected], and the next host will link to it. It will help get awareness out there about your writing, help you meet others in the space community – and community is what blogging is all about. And if you really want to help out, let Fraser know if you can be a host, and he’ll schedule you into the calendar.

Posted on by Nancy Atkinson

Astronomy Cast Ep. 206: Fission

Nuclear reactor

Last week we talked about fusion, where atoms come together to form heavier elements. This week, everything comes apart as we talk about nuclear fission. How it occurs naturally in the Universe, and how it has been harnessed by science to produce power, and devastating weapons.

Click here to download the episode

Fission – Show notes and transcript

Or subscribe to: astronomycast.com/podcast.xml with your podcatching software.

Posted on by Steve Nerlich

Astronomy Without A Telescope – Necropanspermia

Exogenesis
A new instrument called the Search for Extra-Terrestrial Genomes (STEG) is being developed to find evidence of life on other worlds. Credit: NASA/Jenny Mottor

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The idea that a tiny organism could hitchhike aboard a mote of space dust and cross vast stretches of space and time until it landed and took up residence on the early Earth does seem a bit implausible. More likely any such organisms would have been long dead by the time they reached Earth. But… might those long dead alien carcasses still have provided the genomic template that kick started life on Earth? Welcome to necropanspermia.

Panspermia, the theory that life originated somewhere else in the universe and was then transported to Earth requires some consideration of where that somewhere else might be. As far as the solar system is concerned – the most likely candidate site for the spontaneous formation of a water-solvent carbon-based replicator is… well, Earth. And, since all the planets are of a similar age, the only obvious reason to appeal to the notion that life must have spontaneously formed somewhere else, is if a much longer time span than was available in the early solar system is required.

Opinions vary, but Earth may have offered a reasonably stable and watery environment from about 4.3 billion years until 3.8 billion years ago – which is about when the first evidence of life becomes apparent in the fossil record. This represents a good half billion years for some kind of primitive chemical replicator to evolve into a self-contained microorganism capable of metabolic energy production and capable of building another self-contained microorganism.

Half a billion years sounds like a generous amount of time – although with only one example to go by, who knows what a generous amount of time really is. Wesson (below) argues that it is not enough time – referring to other researchers who calculate that random molecular interactions over half a billion years would only produce about 194 bits of information – while a typical virus genome carries 120,000 bits – and an E. coli bacterial genome carries about 6 million bits.

A counter argument to this is that any level of replication in a environment with limited raw materials favors those entities that are most efficient at replication – and continues to do so generation after generation – which means it very quickly ceases to be an environment of random molecular interactions.

Put the term panspermia in a search engineand you get (left) ALH84001, a meteorite from Mars which has some funny looking structures which may just be mineral deposits; and (right) a tardigrade - a totally terrestrial organism that can endure high levels of radiation, desiccation and near vacuum conditions - although it much prefers to live in wet moss. Credit: NASA

The mechanism through which a dead alien genome usefully became the information template for further organic replication on Earth is not described in detail and the case for necropanspermia is not immediately compelling.

The theory still requires that the early Earth was ideally primed and ripe for seeding – with a gently warmed cocktail of organic compounds, shaken-but-not-stirred, beneath a protective atmosphere and a magnetosphere. Under these circumstances, the establishment of a primeval replicator through a fortuitous conjunction of organic compounds remains quite plausible. It is not clear that we need to appeal to the arrival of a dead interstellar virus to kick start the world as we know it.

Further reading: Wesson, P. Panspermia, past and present: Astrophysical and Biophysical Conditions for the Dissemination of Life in Space.

Posted on by Matt Williams

How Much Does the Earth Weigh?

Winter Solstice
Earth as viewed from the cabin of the Apollo 11 spacecraft. Credit: NASA

Earth is, by any reckoning, a pretty big place. Ever since humanity first began the process of exploring, philosophers and scholars have sought to understand its exact dimensions. In addition to wanting to quantify its diameter, circumference, and surface area, they have also sought to understand just how much weight it packs on.

In terms of mass, Earth is also a pretty big customer. Compared to the other bodies of the Solar System, it is the largest and densest of the rocky planets. And over the course of the past few centuries, our methods for determining its mass have improved – leading to the current estimate of 5.9736×1024kg (1.31668×1025 lbs).

Size and Composition:

With a mean radius of 6,371.0 km (3,958.8 mi), Earth is the largest terrestrial planet in our Solar System. This means that it is composed primarily of silicate rock and metals, which are differentiated between a solid inner core, an outer core of molten metal, and a silicate mantle and crust made of silicate material.

This cutaway of planet Earth shows the familiar exterior of air, water and land as well as the interior: from the mantle down to the outer and inner cores. Currents in hot, liquid iron-nickel in the outer core create our planet's protective but fluctuating magnetic field. Credit: Kelvinsong / Wikipedia
This cutaway of planet Earth shows the familiar exterior of air, water and land as well as the interior: from the mantle down to the outer and inner cores. Credit: Kelvinsong / Wikipedia

Earth is composed approximately of 32% iron, 30% oxygen, 15% silicon, 14% magnesium, 3% sulfur, 2% nickel, 1.5% calcium, and 1.4% aluminum, with the remaining made up of trace elements. Meanwhile, the core region is primarily composed of iron (88.8%), with smaller amounts of nickel (5.8%), sulfur (4.5%), and less than 1% trace elements.

Mass and Density:

Earth is also the densest planet in the Solar System, with a mean density of 5.514 g/cm3 (0.1992 lbs/cu in). Between its size, composition, and the distribution of its matter, the Earth has a mass of 5.9736×1024 kg (~5.97 billion trillion metric tons) or 1.31668×1025 lbs (6.585 billion trillion tons).

But since the Earth’s density is not even throughout – i.e. it is denser towards the core than it is at its outer layers – its mass is also not evenly distributed. In fact, the density of the inner core (at 12.8 to 13.1 g/cm³; 0.4624293 lbs/cu in), while the density of the crust is just 2.2–2.9 g/cm³ (0.079 – 0.1 lbs/cu in).

The layers of the Earth, a differentiated planetary body. Credit: Wikipedia Commons/Surachit
The layers of the Earth, a differentiated planetary body. Credit: Wikipedia Commons/Surachit

This overall mass and density are also what causes Earth to have a gravitational pull equivalent to 9.8 m/s² (32.18 ft/s2), which is defined as 1 g.

History of Study:

Modern scientists discerned what the mass of the Earth was by studying how things fall towards it. Gravity is created by mass, so the more mass an object has, the more gravity it will pull with. If you can calculate how an object is being accelerated by the gravity of an object, like Earth, you can determine its mass.

In fact, astronomers didn’t accurately know the mass of Mercury or Venus until they finally put spacecraft into orbit around them. They had rough estimates, but once there were orbiting spacecraft, they could make the final mass calculations. We know the mass of Pluto because we can calculate the orbit of its moon Charon.

The Geoid 2005 model, which was based on data of two satellites (CHAMP and GRACE) plus surface data. Credit: GFZ
The Geoid 2005 model, which was based on data of two satellites (CHAMP and GRACE) plus surface data. Credit: GFZ

And by studying other planets in our Solar System, scientists have had a chance to improve the methods and instruments used to study Earth. From all of this comparative analysis, we have learned that Earth outstrips Mars, Venus, and Mercury in terms of size, and all other planets in the Solar System in terms of density.

In short, the saying “it’s a small world” is complete rubbish!

We have written many articles about Earth for Universe Today. Here’s Ten Interesting Facts About Earth, What is the Diameter of the Earth?, How Strong is the Force of Gravity on Earth?, What is the Rotation of the Earth?

If you’d like more info on Earth, check out NASA’s Solar System Exploration Guide on Earth. And here’s a link to NASA’s Earth Observatory.

We’ve also recorded an episode of Astronomy Cast all about planet Earth. Listen here, Episode 51: Earth.

Sources:

Posted on by Nancy Atkinson

Aurora Alert! Solar Flare Heading Our Way

This image shows a three and a half hour (0000 - 0330 UT) time lapse movie of the flare and filament event. Credit: NASA/SDO

An active sunspot (1123) erupted early this morning (Nov. 12th), producing a C4-class solar flare and apparently hurling a filament of material in the general direction of Earth. Coronagraph images from the Solar and Heliospheric Observatory (SOHO) and NASA’s twin STEREO spacecraft show a faint coronal mass ejection emerging from the blast site and heading off in a direction just south of the sun-Earth line. The cloud could deliver a glancing blow to Earth’s magnetic field sometime between Nov. 13th to the 15th. High latitude sky watchers could see auroras on those dates.
Continue reading “Aurora Alert! Solar Flare Heading Our Way”

Posted on by Nancy Atkinson

Stellar Occultation by Eris

On November 6, 2010, the dwarf planet Eris occulted a faint 16 magnitude star and this was the first time astronomers were able to witness an occultation by Eris. Additionally, at 96.6 Astronomical Units away, it was the most distant object for which this kind of occultation — where one astronomical object passes in front of another — had been seen. Why was this dim, distant event important? It has helped refine the size of what is (was?) thought to be the biggest dwarf planet (yes, I know, an oxymoron) we know of.

“Most of the ways we have of measuring the sizes of objects in the outer solar system are fraught with difficulties,” wrote astronomer and discoverer of Eris, Mike Brown, on his website ‘Mike Brown’s Planets.’ “But, precisely timed occultations like these have the potential to provide incredibly precise answers.”
Continue reading “Stellar Occultation by Eris”