Artistic view of a radiating black hole. Credit: NASA
A new paper has been posted on the arxiv (a repository of research preprints) introducing the idea of a Planck star arising from a black hole. These hypothetical objects wouldn’t be a star in the traditional sense, but rather the light emitted when a black hole dies at the hands of Hawking radiation. The paper hasn’t been peer reviewed, but it presents an interesting idea and a possible observational test.
When a large star reaches the end of its life, it explodes as a supernova, which can cause its core to collapse into a black hole. In the traditional model of a black hole, the material collapses down into an infinitesimal volume known as a singularity. Of course this doesn’t take into account quantum theory.
Although we don’t have a complete theory of quantum gravity, we do know a few things. One is that black holes shouldn’t last forever. Because of quantum fluctuations near the event horizon of a black hole, a black hole will emit Hawking radiation. As a result, a black hole will gradually lose mass as it radiates. The amount of Hawking radiation it emits is inversely proportional to its size, so as the black hole gets smaller it will emit more and more Hawking radiation until it finally radiates completely away.
Because black holes don’t last forever, this has led Stephen Hawking and others to propose that black holes don’t have an event horizon, but rather an apparent horizon. This would mean the material within a black hole would not collapse into a singularity, which is where this new paper comes in.
Diagram showing how matter approaches Planck density. Credit: Carlo Rovelli and Francesca Vidotto
The authors propose that rather than collapsing into a singularity, the matter within a black hole will collapse until it is about a trillionth of a meter in size. At that point its density would be on the order of the Planck density. When the the black hole ends its life, this “Planck star” would be revealed. Because this “star” would be at the Planck density, it would radiate at a specific wavelength of gamma rays. So if they exist, a gamma ray telescope should be able to observe them.
Just to be clear, this is still pretty speculative. So far there isn’t any observational evidence that such a Planck star exists. It is, however, an interesting solution to the paradoxical side of black holes.
The Universe is vast bubble of space and time, expanding in volume. Run the clock backward and you get to a point where everything was compacted into a microscopic singularity of incomprehensible density. In a fraction of a second, it began expanding in volume, and it’s still continuing to do so today.
So how old is the Universe? How long has it been expanding for? How do we know? For a good long while, Astronomers assumed the Earth, and therefore the Universe was timeless. That it had always been here, and always would be.
In the 18th century, geologists started to gather evidence that maybe the Earth hadn’t been around forever. Perhaps it was only millions or billions of years old. Maybe the Sun too, or even… the Universe. Maybe there was a time when there was nothing? Then, suddenly, pop… Universe.
It’s the science of thermodynamics that gave us our first insight. Over vast lengths of time, everything moves towards entropy, or maximum disorder. Just like a hot coffee cools down, all temperatures want to average out. And if the Universe was infinite in age, everything should be the same temperature. There should be no stars, planets, or us.
The brilliant Belgian priest and astronomer, George Lemaitre, proposed that the Universe must be either expanding or contracting. At some point, he theorized, the Universe would have been an infinitesimal point – he called it the primeval atom. And it was Edwin Hubble, in 1929 who observed that distant galaxies are moving away from us in all directions, confirming Lemaitre’s theories. Our Universe is clearly expanding.
Which means that if you run the clock backwards, and it was smaller in the distant past. And if you go back far enough, there’s a moment in time when the Universe began. Which means it has an age. The next challenge… figuring out the Universe’s birthdate.
Time line of the Universe (Credit: NASA/WMAP Science Team)
In 1958, the astronomer Allan Sandage used the expansion rate of the Universe, otherwise known as the Hubble Constant, to calculate how long it had probably been expanding. He came up with a figure of approximately 20 billion years. A more accurate estimation for the age of the Universe came with the discovery of the Cosmic Microwave Background Radiation; the afterglow of the Big Bang that we see in every direction we look.
Approximately 380,000 years after the Big Bang, our Universe had cooled to the point that protons and electrons could come together to form hydrogen atoms. At this point, it was a balmy 3000 Kelvin. Using this and by observing the background radiation, and how far the wavelengths of light have been stretched out by the expansion, astronomers were able to calculate how long it has been expanding for.
Initial estimates put the age of the Universe between 13 and 14 billion years old. But recent missions, like NASA’s WMAP mission and the European Planck Observatory have fine tuned that estimate with incredible accuracy. We now know the Universe is 13.8242 billion years, plus or minus a few million years.
We don’t know where it came from, or what caused it to come into being, but we know exactly how our Universe is. That’s a good start.
Shepherd moon Prometheus hovers just inside the reflective F ring
Lit by eerie, reflected light from Saturn’s F ring (and a casting a faint shadow through a haze of icy “mist”) Saturn’s moon Prometheus can be seen in the raw image above, captured by Cassini’s narrow-angle camera on Feb. 5 from a distance of 667,596 miles (1,074,392 km). It’s also receiving some light reflected off Saturn, which is off frame at the top (where the outermost edge of the A ring and the Keeler gap can be seen.)
As the potato-shaped Prometheus approaches the ring it yanks fine, icy material in towards itself, temporarily stretching the bright particles into long streamers and gaps and even kicking up bright clumps in the ring. It’s a visual demonstration of gravity at work! Watch an animation of this below, made from images acquired just before and after the one above:
Streamers and clumps created by the passing Prometheus on Feb. 5, 2014. (NASA/JPL/SSI. Animation by Jason Major.)
At its longest Prometheus is about 92 miles (148 km) across, but only 42 miles (68 km) in width. It circles Saturn in a wave-shaped, scalloping orbit once every 14.7 hours.
Spectacular photo of Comets C/2012 X1 LINEAR (top) and C/2013 R1 Lovejoy taken with a wide field 4-inch telescope before dawn Feb. 9, 2014. Credit: Damian Peach
Remember comets Lovejoy and C/2012 X1 LINEAR? Wedropped in on them in late January. On Feb. 6 the two cruised within 2 degrees of each other as they tracked through Ophiuchus before dawn. Were it not for bad weather, astrophotographer Damian Peach would have been out to record the cometary conjunction, but this unique photo, taken two mornings later, shows the two comets chasing each other across the sky. Of course they’re not really following one another, nor are they related, but the illusion is wonderful.
Comets Lovejoy and X1 LINEAR are neighbors in northern Ophiuchus through Feb. 25. This map shows the sky facing east about 1 hour 45 minutes before sunrise shortly before the start of morning twilight. Tick marks show the comets’ position every 5 days. Detailed map below. Created with Chris Marriott’s SkyMap software.
Rarely do two relatively bright comets align so closely. Even more amazing was how much they looked alike. By good fortune I was able to see them both through a 15-inch (37-cm) under a very dark sky this morning. Although Lovejoy’s faint, approximately 20′ long tail was fanned out more than X1’s, both tails were faint, short and pointed to the west-northwest. Lovejoy’s coma was slightly larger and brighter, but both comets’ comas diplayed similarly compact, bright centers.
This deeper map shows stars to about magnitude 8. Although both comets appear to be getting lower every morning, the westward seasonal drift of the stars will keep them in good view for the next few months. Click to enlarge. Created with Chris Marriott’s SkyMap software
Lovejoy currently hovers around magnitude 8.1, X1 LINEAR at 8.8 – less than a magnitude apart. If you haven’t seen them yet, they’re still the brightest comets we’ll have around for another few months unless an unexpected visitor enters the scene.
After converging for weeks, the comets’ paths are now slowly diverging and separating. Look while you can; the waxing moon will soon rob these fuzzies of their fading glory when it enters the morning sky this coming Tuesday or Wednesday.
See this earlier article for more information on both comets.
Curiosity scans Moonlight Valley beyond Dingo Gap Dune. Curiosity’s view to “Moonlight Valley” beyond after crossing over ‘Dingo Gap’ sand dune. This photomosaic was taken after Curiosity drove over the 1 meter tall Dingo Gap sand dune and shows dramatic scenery in the valley beyond, back dropped by eroded rim of Gale Crater. Assembled from navigation camera (navcam) raw images from Sol 535 (Feb. 6, 2104) Credit: NASA/JPL-Caltech/Ken Kremer- kenkremer.com/Marco Di Lorenzo
Curiosity scans Moonlight Valley beyond Dingo Gap Dune.
Curiosity’s view to “Moonlight Valley” beyond after crossing over ‘Dingo Gap’ sand dune. This photomosaic was taken after Curiosity drove over the 1 meter tall Dingo Gap sand dune and shows dramatic scenery in the valley beyond, back dropped by eroded rim of Gale Crater. Assembled from navigation camera (navcam) raw images from Sol 535 (Feb. 6, 2104) Credit: NASA/JPL-Caltech/Ken Kremer- kenkremer.com/Marco Di Lorenzo
See below more before/after Dingo Gap imagery
Story updated[/caption]
NASA’s Curiosity mega rover has successfully crossed over the ‘Dingo Gap’ sand dune- opening the gateway to the science rich targets in the “Moonlight Valley” and Martian mountain beyond.
“I’m over the moon that I’m over the dune! I successfully crossed the “Dingo Gap” sand dune on Mars,” Curiosity tweeted overnight Thursday.
“Moonlight Valley” is the name of the breathtaking new locale beyond Dingo, Curiosity Principal Investigator John Grotzinger, of Caltech, told Universe Today.
Curiosity drove westward over the 1 meter ( 3 foot) tall Dingo Gap dune in stellar style on Thursday, Feb. 6, on Sol 535.
Curiosity looks back to ‘Dingo Gap’ sand dune after crossing over, backdropped by Mount Sharp on Sol 535, Feb. 5, 2014. Hazcam fisheye image linearized and colorized. Credit: NASA/JPL/Marco Di Lorenzo/Ken Kremer- kenkremer.com
Dramatic before and after photos reveal that the rover passed over the Red Planet dune without difficulty. They also show some interesting veins and mineral fractures are visible in the vicinity just ahead.
“Moonlight Valley has got lots of veins cutting through it,” Grotzinger told me.
“We’re seeing recessive bedrock.”
The Martian dune lies between two low scarps sitting at the north and south ends.
“The rover successfully traversed the dune in Dingo Gap,” wrote science team member Ken Herkenhoff in an update.
“The data look good.”
Curiosity Crosses ‘Dingo Gap’ sand dune – Looking forward and back on Sol 535. Hazcam camera images. Credit: NASA
Since arriving at the picturesque “Dingo Gap” sand dune about a week ago, Curiosity’s handlers had pondered whether to breach the dune as an alternate pathway into the smoother terrain of the valley beyond as a work around to avoid fields of rough rocks that have been ripping holes into the robots six aluminum wheels in recent months.
“We’re guessing it will be softer on the wheels,” Grotzinger informed me.
Before giving the go ahead to move forward, engineers took a few days to carefully assess the dune’s integrity and physical characteristics with the rovers science instruments and cameras to insure there wasn’t the potential to get irretrievably stuck in a deep sand trap.
The team even commanded Curiosity to carry out a toe dip by gently rolling the 20 inch (50 cm) diameter wheels back and forth over the crest on Tuesday, Feb. 4 to insure it was safe to mount.
They won’t take any chances with safety, recalling that rover Spirit’s demise occurred when she because mired in a hidden sand trap in 2010 from which there was ultimately no escape. She froze to death during the bitter Martin winter – more than 6 years into her 90 day mission.
Opportunity also got wedged at the seemingly endless dune field at “Purgatory Dune”, that nearly doomed her early in the now decade long trek. Engineers spent weeks on the extrication effort.
Curiosity does a “toe dip” wheel motion test at Dingo Gap sand dune on Sol 534, Feb 5, 2014 before crossing dune on Sol 535. Hazcam image linearized and colorized. Credit: NASA/JPL/Marco Di Lorenzo/Ken Kremer- kenkremer.com
Since last summer, Curiosity has been traveling on a southwestward route to the breathtaking foothills of Mount Sharp, her ultimate science destination.
The westward route though Dingo will soon lead Curiosity to a spot dubbed “KMS-9” where the team hopes to conduct the first rock drilling operations since departing the Yellowknife Bay quadrant in July 2013, into areas of intriguing bedrock.
“At KMS-9, we see three terrain types exposed and a relatively dust-free surface,” said science team collaborator Katie Stack of the California Institute of Technology, Pasadena.
The missions science focus has shifted to “search for that subset of habitable environments which also preserves organic carbon,” says Curiosity Principal Investigator John Grotzinger, of the California Institute of Technology in Pasadena.
But first, with the dune now safely in the rear view mirror, the team plans a busy weekend of research activities.
A big science program using the X-Ray spectrometer and high resolution MAHLI camera on the robotic arm is already planned for this weekend.
“The arm will be deployed to investigate some interesting veins or minerals filling fractures in front of the rover,” says Herkenhoff.
“ChemCam will search for frost early on the morning of Sol 538 (Saturday), then analyze targets Collett and Mussell along the vein/fracture fill later in the day.”
Thereafter Curiosity will continue on its journey across the floor of Gale Crater, taking images and atmospheric measurements along the way to the sedimentary layers at the base of Mount Sharp.
Curiosity has already accomplished her primary goal of discovering a habitable zone on Mars that could support Martian microbes if they ever existed.
And be sure to check out Curiosity’s first ever image of Earth from Mars in my new story – here.
To date Curiosity’s odometer stands at nearly 5 kilometers and she has taken over 118,000 images.
The robot has about another 5 km to go to reach Mount Sharp.
Stay tuned here for Ken’s continuing Curiosity, Opportunity, Chang’e-3, SpaceX, Orbital Sciences, LADEE, MAVEN, MOM, Mars and more planetary and human spaceflight news.
You are here! As an Evening Star in the Martian Sky
This evening-sky view taken by NASA’s Mars rover Curiosity shows the Earth and Earth’s moon as seen on Jan. 31, 2014, or Sol 529 shortly after sunset at the Dingo Gap inside Gale Crater. Credit: NASA/JPL-Caltech/MSSS/TAMUCuriosity’s View Past Tall Dune at edge of ‘Dingo Gap’
This photomosaic from Curiosity’s Navigation Camera (Navcam) taken at the edge of the entrance to the Dingo Gap shows a 3 foot (1 meter) tall dune and valley terrain beyond to the west, all dramatically back dropped by eroded rim of Gale Crater. View from the rover’s overlook position on Sol 528 (Jan. 30, 2014). The rover team has now commanded Curiosity to bridge the dune gap as a smoother path to next science destination. Credit: NASA/JPL-Caltech/Marco Di Lorenzo/Ken Kremer- kenkremer.comUp close view of hole in one of rover Curiosity’s six wheels caused by recent driving over rough Martian rocks. Mosaic assembled from Mastcam raw images taken on Dec. 22, 2013 (Sol 490). Credit: NASA/JPL/MSSS/Ken Kremer – kenkremer.com/Marco Di Lorenzo
Around this time last year a space rock crashed into the Earth above Chelyabinsk, Russia. It brightened the skies for hundreds of kilometers, broke windows and injured many people. Let’s look back at the event. What happened, and what did we learn? Continue reading “Astronomy Cast Ep. 334: Chelyabinsk”
Just take a look at the surface of the Moon and you can see it experienced a savage beating in the past. Turns out, the whole Solar System is a cosmic shooting gallery, with stuff crashing into other stuff. It sure sounds violent, but then, we wouldn’t be here without it. Continue reading “Astronomy Cast Ep. 333: When Worlds Collide”
The aurora of February 3-4, 2014 seen from inside a plexiglass aurora dome in Churchill, Manitoba at the Churchill Northern Studies Centre. Credit and copyright: Alan Dyer.
There are not many places where you can be indoors and have a spectacular view of the Aurora Borealis, but the Churchill Northern Studies Centre in Canada is one. This incredible shot of the the aurora was taken from inside a plexiglass dome created specifically for being able to watch the sky from indoors. Astrophotographer Alan Dyer described it as “a warm way to watch the aurora.”
This view is a 30-second exposure looking up through the dome. Below you can see how the aurora looked from outsdoors, which is stunning as well.
The aurora of February 3-4, 2014 as seen from outdoors in Churchill, Manitoba at the Churchill Northern Studies Centre, looking west to Orion and Taurus. Credit and copyright: Alan Dyer.
The Churchill Northern Studies Centre non-profit research and education facility located 23 km east of the town of Churchill, Manitoba that supports sub-arctic scientific researchers working on “a diverse range of topics of interest to northern science,” in addition to being an educational resource center for schools.
Thanks to Alan for sharing his images from his aurora experience at the Centre, and you can see more on Alan’s Flickr page or his website.
Host: Fraser Cain Astrojournalists: Scott Lewis, Nicole Gugliucci, Morgan Rehnberg, Brian Koberlein, Elizabeth Howell, Amy Shira Teitel, David Dickinson
We record the Weekly Space Hangout every Friday at 12:00 pm Pacific / 3:00 pm Eastern. You can watch us live on Google+, Universe Today, or the Universe Today YouTube page.
Centaurus A (the site of a supermassive black hole) shines brightly in this composite image from the Chandra X-ray Observatory. Scientists used the equivalent of 9.5 days' worth of observations between 1999 and 2012. Credit: X-ray: NASA/CXC/U.Birmingham/M.Burke et al.
This image, right here, shows us the value of long-term observations. It’s a composite of pictures taken between 1999 and 2012 from NASA’s Chandra X-ray Telescope. Put 9.5 days’ worth of observations together, and you can see a lot of action in Centaurus A — namely, a huge jet emanating from a ginormous black hole embedded in the galaxy.
“As in all of Chandra’s images of Cen A, this one shows the spectacular jet of outflowing material – seen pointing from the middle to the upper left – that is generated by the giant black hole at the galaxy’s center. This new high-energy snapshot of Cen A also highlights a dust lane that wraps around the waist of the galaxy. Astronomers think this feature is a remnant of a collision that Cen A experienced with a smaller galaxy millions of years ago,” NASA stated.
Black hole with disc and jets visualization courtesy of ESA
A past survey of X-ray sources in Cen A revealed that most of them are black holes or neutron stars (the latter created from the wake of a huge star’s collapse). It seems that most of these sources are either less than twice the mass of the sun, or more than five times as massive. Here’s the more interesting bit: the smaller ones appear to be neutron stars, and the bigger ones black holes.
“This mass gap may tell us about the way massive stars explode. Scientists expect an upper limit on the most massive neutron stars, up to twice the mass of the Sun,” NASA added.
“What is puzzling is that the smallest black holes appear to weigh in at about five times the mass of the Sun. Stars are observed to have a continual range of masses, and so in terms of their progeny’s weight we would expect black holes to carry on where neutron stars left off.”
