I love it when scientists discover something unusual in nature. They have no idea what it is, and then over decades of research, evidence builds, and scientists grow to understand what’s going on.
My favorite example? Quasars.
Astronomers first knew they had a mystery on their hands in the 1960s when they turned the first radio telescopes to the sky.
They detected the radio waves streaming off the Sun, the Milky Way and a few stars, but they also turned up bizarre objects they couldn’t explain. These objects were small and incredibly bright.
They named them quasi-stellar-objects or “quasars”, and then began to argue about what might be causing them. The first was found to be moving away at more than a third the speed of light.
But was it really?
An artist’s conception of jets protruding from an AGN.Maybe we were seeing the distortion of gravity from a black hole, or could it be the white hole end of a wormhole. And If it was that fast, then it was really, really far… 4 billion light years away. And it generating as much energy as an entire galaxy with a hundred billion stars.
What could do this?
Here’s where Astronomers got creative. Maybe quasars weren’t really that bright, and it was our understanding of the size and expansion of the Universe that was wrong. Or maybe we were seeing the results of a civilization, who had harnessed all stars in their galaxy into some kind of energy source.
Then in the 1980s, astronomers started to agree on the active galaxy theory as the source of quasars. That, in fact, several different kinds of objects: quasars, blazars and radio galaxies were all the same thing, just seen from different angles. And that some mechanism was causing galaxies to blast out jets of radiation from their cores.
But what was that mechanism?
This artist’s concept illustrates a quasar, or feeding black hole, similar to APM 08279+5255, where astronomers discovered huge amounts of water vapor. Gas and dust likely form a torus around the central black hole, with clouds of charged gas above and below. Image credit: NASA/ESAWe now know that all galaxies have supermassive black holes at their centers; some billions of times the mass of the Sun. When material gets too close, it forms an accretion disk around the black hole. It heats up to millions of degrees, blasting out an enormous amount of radiation.
The magnetic environment around the black hole forms twin jets of material which flow out into space for millions of light-years. This is an AGN, an active galactic nucleus.
When the jets are perpendicular to our view, we see a radio galaxy. If they’re at an angle, we see a quasar. And when we’re staring right down the barrel of the jet, that’s a blazar. It’s the same object, seen from three different perspectives.
Supermassive black holes aren’t always feeding. If a black hole runs out of food, the jets run out of power and shut down. Right up until something else gets too close, and the whole system starts up again.
The Milky Way has a supermassive black hole at its center, and it’s all out of food. It doesn’t have an active galactic nucleus, and so, we don’t appear as a quasar to some distant galaxy.
We may have in the past, and may again in the future. In 10 billion years or so, when the Milky way collides with Andromeda, our supermassive black hole may roar to life as a quasar, consuming all this new material.
Noctilucent clouds taken from the ISS Image Credit: NASA
Intrigued by mysterious noctilucent, or night-shining clouds? This beautiful new film from TWAN (The World At Night) photographer P-M Hedén combines timelapse and real-time footage to provide a stunning compilation of his month in the field in Sweden this summer to capture these lovely blue electric clouds. Noctilucent clouds are visible sometimes low in the northern sky during morning and evening twilight, usually through late May through August, and they seem to be increasing the past few years.
Enjoy the stunning, tranquil views (lots of wildlife and night sky imagery too!) and lovely music in this new film, just published yesterday.
If you need a break from the Perseid Meteor Shower, come join us for a Virtual Star Party. This is where we connect up a bunch of telescopes into a Google+ Hangout on Air and broadcast the skies live.
Host: Fraser Cain
Astronomers: Scott Lewis, Thad Szabo, Gary Gonella and Bill McLaughlin.
We run the Virtual Star Party every Sunday night when it gets dark on the West Coast. In the summer time, that’s 9:00 pm Pacific/12:00 am Eastern. In the Winter time, we start at 5/8 (which is much better for the East Coasters).
We’re always looking for more astronomers to join us, especially from South America, where we can get a view of the southern skies. If you’d like to participate, drop me an email at [email protected].
Gather round the internets for another episode of the Weekly Space Hangout. Where our experienced team of journalists, astronomers and astronomer-journalists bring you up to speed on the big happenings in the universe of space and astronomy.
Our team this week:
Reporters: Casey Dreier, David Dickinson, Amy Shira Teitel, Sondy Springmann, Nicole Gugliuci
We record the Weekly Space Hangout every Friday at Noon Pacific, 3 pm Eastern. Join us live here on Universe Today, over on our YouTube account, or on Google+. Or you can watch the archive after the fact.
The Lagoon Nebula M8 (NGC 6523) , The Trifid Nebula M20 (NGC 6514), Star cluster M21 and star forming region NGC6559. Credit and copyright: Terry Hancock/Down Under Observatory.
Here’s a beautiful deep look at a wide-field view of the Lagoon Nebula (M8, NGC 6523) and the Trifid Nebula (M20, NGC 6514) along with star cluster M21 and star forming region NGC6559. Amateur astronomer and astrophotographer Terry Hancock from Michigan says this is one of his favorite fields of view to observe. However, right now it’s very low in the southern sky and therefore limited to a couple of hours each night. Just wait until next month, and this region will be higher in the sky for better northern hemisphere viewing.
Terry captured this view in H-Alpha plus RGB over 4 nights.
I’ll let him explain the view:
“Both of these objects are intensely rich with HII regions. Right of center is The Lagoon Nebula, a giant emission Nebula and HII region, bottom center can be seen the star forming region NGC6559 , these are estimated at 4,000 to 6,000 light years from us in the constellation Sagittarius.
Upper left in this image can be seen M20 or NGC 6514 known as The Trifid Nebula also in the constellation of Sagittarius and lies at a distance of approximately 5000 light years from us.
This object is a combination of emission nebula (the red area), reflection nebula (the blue area) and dark nebula (the dark jagged lines within the Trifid Nebula). Below left of M8 is the Star cluster M21.”
Just a really stunning “deep and wide” view of this region of the sky. See more of Terry’s work at his website, The Down Under Observatory (he’s originally from Australia) or on Flickr or Google +.
He’s also got a great video of some of his work:
Want to get your astrophoto featured on Universe Today? Join our Flickr group or send us your images by email (this means you’re giving us permission to post them). Please explain what’s in the picture, when you took it, the equipment you used, etc.
An occultation of the star Mu Geminorum (to the upper right off the dark limb of the Moon) Photo by author.
The first in a cycle of challenging occultations of the bright star Spica for northern hemisphere observers begins this coming Monday on August 12th.
Watching a bright star or planet wink out on the dark limb of the Moon can be an amazing event to witness. It’s an abrupt “now you see it, now you don’t” event in a universe which often seems to move at an otherwise glacial pace. And if the event grazes the limb of the Moon, an observer may see a series of winks as the starlight streams through the lunar valleys.
Close companion stars have been discovered during occultations, and astronomers even used a series of occultations of radio source 3C 273 in 1962 to pin down the position of the first quasar.
An occultation occurs when one object passes in front of another as seen from the observer’s vantage point. The term has its hoary roots back in a time when astronomy was intertwined with its pseudoscience ancestor of astrology. Even today, I still get funny looks from non-astronomy friends when I use the term occultation, as if it just confirms their suspicions of the arcane arts that astronomers really practice in secret.
But back to reality-based science. At an apparent magnitude of +1.1, Spica is the 3rd brightest star that the Moon can occult along its five degree path above and below the plane of the ecliptic. It’s also one of only four stars brighter than +1.4 magnitude on the Moon’s path. The others are Antares (magnitude +1.0), Regulus (magnitude +1.4), and Aldebaran (magnitude +0.8). All of these are bright enough to be visible on the lunar limb through binoculars or a telescope in the daytime if conditions are favorable.
It’s interesting to note that this situation also changes over time due to the precession of the equinoxes. For example, the bright star Pollux was last occulted by the Moon in 117 BC, but cannot be covered by the Moon in our current epoch.
Spica is currently in the midst of a cycle of 21 occultations by our Moon. This cycle started in July 25th, 2012 and will end in January 2014.
Spica is a B1 III-IV type star 10 times the mass of the Sun. At 260 light years distant, Spica is one of the closest candidates to the Earth along with Betelgeuse to go supernova. Now, THAT would make for an interesting occultation! Both are safely out of the ~100 light year distant “kill zone”.
What follows are the circumstances for the next four occultations of Spica by the Moon. The times are given for closest geocentric conjunction of the two objects. Actual times of disappearance and reappearance will vary depending on the observer’s location. Links are provided for each event which include more info.
Looking westward 30 minutes after sunset for North American viewers on the night of August 12th. (Created by the Author using Starry Night).
First up is the August 12th occultation of Spica, which favors Central Asia and the Asian Far East. This will occur late in the afternoon sky around 09:00 UT and prior to sunset. The waxing crescent Moon will be six days past New phase. North American observers will see the Moon paired five degrees from Spica with Saturn to the upper left on the evening of August 12th.
The footprint for the September 8th occultation of Spica by the Moon. Note that the broken line indicates where the occultation will take place in the daytime sky. ( Credit: Occult 4.1.0.2)
Next is the September 8th daytime occultation of Spica for Europe, the Middle East and northern Africa around ~15UT. This will be a challenge, as the Moon will be a waxing crescent at only 3 days past New. Observers in the Middle East will have the best shot at this event, as the occultation occurs at dusk and before moonset. Note that the Moon also occults Venus six hours later for Argentina and Chile.
Looking to the east the morning of November 2nd for North American observers. (Created by the author using Stellarium).
After taking a break in October (the occultation of October 5 occurs only 23 hours after New and is unobservable), the Moon again occults Spica on November 2nd for observers across Europe & Central Asia. This will be a difficult one, as the Moon will be only 20 hours from New and a hybrid solar eclipse that will cross the Atlantic and central Africa. It may be possible to lock on to the Moon and track it up into the daylight, just be sure to physically block the rising Sun behind a building or hill!
The occultation footprint of Spica by the Moon for November 29th, 2013. (Reproduced from the Astronomical Almanac online and produced by the U.S. Naval Observatory and H.M. Nautical Almanac Office).
Finally, the Moon will occult Spica for North American observers on November 29th centered on 17:03 UT. This will place the event low in the nighttime sky for Alaskan observers. It’ll be a bit more of a challenge for Canadian and U.S. observers in the lower 48, as the Moon & Spica will be sandwiched between the Sun and the western horizon in the mid-day sky. As an added treat, comet C/2012 S1 ISON will reach perihelion on November 28th, just 20 hours prior and will be reaching peak brilliance very near the Sun.
And as an added bonus, the Moon will be occulting the +2.8 star Alpha Librae (Zubenelgenubi) on August 13th for central South America.
All of these events are challenges, to be sure. Viewers worldwide will still catch a close night time pairing of the Moon and Spica on each pass. We’ve watched the daytime Moon occult Aldebaran with binoculars while stationed in Alaska back in the late 1990’s, and can attest that such a feat of visual athletics is indeed possible.
And speaking of which, the next bright star due for a series of occultations by the Moon is Aldebaran starting in 2015. After 2014, Spica won’t be occulted by the Moon again until 2024.
But wait, there’s more- the total eclipse of the Moon occurring on April 15th 2014 occurs just 1.5 degrees from Spica, favoring North America. This is the next good lunar eclipse for North American observers, and one of the best “Moon-star-eclipse” conjunctions for this century. Hey, at least it’ll give U.S. observers something besides Tax Day to look forward to in mid-April. More to come in 2014!
The FastSound project's 3D map of the large-scale structure of a region in the Universe about 4.7 billion years after the Big Bang. This area covers 2.5 times 3 degrees of the sky, with a radial distance spanning 12-14.5 billion light years in comoving distance or 8-9.6 billion light years in light travel distance. Credit: NAOJ, SDSS, CFHT.
I remember seeing the Hubble 3-D IMAX movie in 2010 and literally gasping when the view pulled back from zooming into distant stars and galaxies to show clusters and superclusters of galaxies interwoven like a web, creating the large scale structure of the Universe. In 3-D, the structure looks much like the DNA double helix or a backbone.
Now, a new project that aims to map the Universe’s structure has looked back in time to create a 3-D map showing a portion of the Universe as it looked nine billion years ago. It shows numerous galaxies and interestingly, already-developed large-scale structure of filaments and voids made from galaxy groups.
The map was created by the FastSound project, which is surveying galaxies in the Universe using the Subaru Telescope’s new Fiber Multi-Object Spectrograph (FMOS). The team doing the work is from Kyoto University, the University of Tokyo and the University of Oxford.
The team said that although they can see that the clustering of galaxies is not as strong back when the Universe was 4.7 billion years old as it is in the present-day Universe, gravitational interaction will eventually result in clustering that grows to the current level.
The new map spans 600 million light years along the angular direction and two billion light years in the radial direction. The team will eventually survey a region totaling about 30 square degrees in the sky and then measure precise distances to about 5,000 galaxies that are more than ten billion light years away.
But the FastSound project hopes to create a 3-D map of the very distant Universe by covering the volume of the Universe farther than ten billion light years away. FMOS is a wide-field spectroscopy system that enables near-infrared spectroscopy of over 100 objects at a time, with an exceptionally wide field of view when combined with the light collecting power of the 8.2 meter primary mirror of the telescope.
The map released today is just the first from FastSound. The final 3-D map of the distant Universe will precisely measure the motion of galaxies and then measure the rate of growth of the large-scale structure as a test of Einstein’s general theory of relativity.
Although scientists know that the expansion of the Universe is accelerating, they do not know why – whether it is from dark energy or whether gravity on cosmological scales may differ from that of general relativity, this mystery is one of the biggest questions in contemporary physics and astronomy. A comparison of the 3D map of the young Universe with the predictions of general relativity could eventually reveal the mechanism for the mysterious acceleration of the Universe.
The team said their 3-D map shown in this release uses a measure of “comoving” distance rather than light travel distance. They explained:
Light travel distance refers to the time that has elapsed from the epoch of the observed distant galaxy to the present, multiplied by the speed of light. Since the speed of light is always constant for any observer, it describes the distance of the path that a photon has traveled. However, the expansion of the Universe increases the length of the path that the photon traveled in the past. Comoving distance, the geometrical distance in the current Universe, takes this effect into account. Therefore, comoving distance is always larger than the corresponding light travel distance.
In the lead image above from FastSound, the colors of the galaxies indicate their star formation rate, i.e., the total mass of stars produced in a galaxy every year. The gradation in background color represents the number density of galaxies; the underlying mass distribution (which is dominated by invisible dark matter that accounts for about 30% of the total energy in the Universe) and how it would look like this if we could see it. The lower part of the figure shows the relative locations of the FastSound and the Sloan Digital Sky Survey (SDSS) regions, indicating that the FastSound project is mapping a more distant Universe than SDSS’s 3D map of the nearby Universe.
Clear of the launch utility tower, the Delta IV Medium+ and its WGS-6 payload begin the climb uphill. Credit: John O'Connor/nasatech.net
Who doesn’t like a good launch? These images and videos from last night’s launch of United Launch Alliance’s Delta 4 rocket are just pretty. The rocket boosted an international military communications satellite to orbit following a beautiful night-time launch from Cape Canaveral Air Force Station at 8:29 pm EDT on August 7 (00:29 UTC on August 8, 2013). The 21-story-tall Delta 4 included four solid-fuel strap-on boosters for extra oomph. As @OxyAstro said on Twitter last night, “I like to think of the Delta IV as an apartment building sitting on a few million lbs of thrust.”
Images here are from John O’Connor at Nasatech.net, and enjoy a close-up video of the launch, below, from Matthew Travis.
A standard video view of the launch is below.
On board was the WGS-6 (Wideband Global Satcom)a big 6,000 kg (13,200 lb) satellite that is part of a military communications network shared by the United States, Australia, Canada, Denmark, Luxembourg, the Netherlands and New Zealand.
As flames from the hydrogen-rich ignition coil around the boosters the RS-68 main engine comes up to full power. Credit: John O’Connor/nasatech.netRising from the launch table the Delta IV/WGS-6 mission begins. Credit: John O’Connor/nasatech.netClear of the lightning towers the WGS-6 mission streaks to super-sync geo orbit. Credit: John O’Connor/nasatech.net.
Did you know you can distinguish between stars and planets in the sky?
Stars twinkle, planets don’t.
Okay, that’s not actually correct. The stars, planets, even the Sun and Moon twinkle, all in varying amounts. Anything outside the atmosphere is going to twinkle.
If you’re feeling a little silly using the word twinkle over and over again, we can also use the scientific term: astronomical scintillation.
You can’t feel it, but you’re carrying the entire weight of the atmosphere on your shoulders. Every single square inch of your skin is getting pushed by 15 pounds of pressure. And even though astronomers need our atmosphere to survive, it still drives them crazy. As it makes objects in space so much harder to see.
Stars twinkle, I mean scintillate, because as light passes down through a volume of air, turbulence in the Earth’s atmosphere refracts light differently from moment to moment. From our perspective, the light from a star will appear in one location, then milliseconds later, it’ll be distorted to a different spot.
We see this as twinkling.
So why do stars appear to twinkle, while planets don’t?
Stars appear as a single point in the sky, because of the great distance between us and them. This single point can be highly affected by atmospheric turbulence. Planets, being much closer, appear as disks.
We can’t resolve them as disks with our eyes, but it still averages out as a more stable light in the sky.
Astronomers battle atmospheric turbulence in two ways:
First, they try to get above it. The Hubble Space Telescope is powerful because it’s outside the atmosphere. The mirror is actually a quarter the size of a large ground-based observatory, but without atmospheric distortion, Hubble can resolve galaxies billions of light-years away. The longer it looks, the more light it gathers.
Second, they try to compensate for it.
Some of the most sophisticated telescopes on Earth use adaptive optics, which distorts the mirror of the telescope many times a second to compensate for the turbulence in the atmosphere.
A beam from the Laser Star Guide on one of the VLT’s four Unit Telescopes helps to correct the blurring effect of Earth’s atmosphere before making observations (ESO/Y. Beletsky)Astronomers project a powerful laser into the sky, creating an artificial star within their viewing area. Since they know what the artificial star should look like, they distort the telescope’s mirror with pistons cancelling out the atmospheric distortion. While it’s not as good as actually launching a telescope into space, it’s much, much cheaper.
Now you know why stars twinkle, why planets don’t seem to twinkle as much, and how you can make all of them stop.
We have written many articles about stars here on Universe Today. Here’s an article that talks about a technique astronomers use to minimize the twinkle of the Earth’s atmosphere.
A Soyuz rocket on the launchpad at the Baikonur Cosmodrome in December, 2012. Credit: NASA.
Want to know more about the Soyuz rocket? This new video from ESA is based on actual lessons for astronauts about the Soyuz rocket and describes the parts of the Soyuz, the stages and launch sequence. The info here was part of ESA Basic Training for the ESA astronaut class of 2009 (also known as the Shenanigans09).
When the jets are perpendicular to our view, we see a radio galaxy. If they’re at an angle, we see a quasar. And when we’re staring right down the barrel of the jet, that’s a blazar. It’s the same object, seen from three different perspectives.
