March 16, 2012 at 9:40 am | Leave a Comment
Hercules Saves the Day
Want to explore galaxies? Look no further than the latest image of interacting galaxies in the Hercules Cluster. It’s chock full of ‘em!
This glorious image was taken with the VLT Survey Telescope (VST) at ESO’s Paranal Observatory. When you dig into this image, you can see a collection of interacting galaxies that lie about 500 million light-years away.
This cluster is a rather interesting one and the story accompanying this image on the ESO Web site is a study in galaxy interactions. As well as being somewhat irregular in shape, there are many different types of galaxies. Some are young and active, creating many new stars. About the only type of galaxies this cluster doesn’t have are giant ellipticals.
You’ll find galaxy pairs getting up close and personal with each other, well on their way to merging into single, larger galaxies. The numerous other interactions, and the large number of gas-rich, star-forming spiral galaxies in the cluster, make the members of the Hercules cluster look like the young galaxies that astronomers see in the distant universe (farther back in cosmic history). Because of this similarity, astronomers believe that the Hercules galaxy cluster is a relatively young cluster. It’s thought to be a collection of at least three smaller subclusters and groups that are all assembling themselves into a much larger structure within the cluster. But, the interactions don’t stop there… the Hercules cluster itself is merging with other large clusters to form a galaxy supercluster. All this information is giving astronomers good insight into how larger galaxy structures and clusters assemble themselves together in the universe over cosmic time. Stay tuned!
March 13, 2012 at 10:03 am | Leave a Comment
Lunar and Otherwise
I have a great gig doing cruise ship enrichment presentations about astronomy. Lots of good conversations flow after my talks, particularly at sunset when some of us gather on the top deck to wave goodbye to the Sun. Sunsets at sea are some of my favorite scenes, so I always make time to enjoy them.
One of the questions I got from a passenger recently was about how he’d read that the survivors of the Titanic sinking in 1912 had looked up at the stars as they floated (freezing) in their lifeboats awaiting rescue. I would imagine the view would have been spectacular in the chilly scene. It’s interesting that people did mention seeing the stars, considering what a life-threatening situation they were in. Maybe those things become more important when the end appears nigh.
Speaking of Titanic, there’s a theory afloat now (see what I did there?) about how a team of astronomers from Texas State Universe in San Marcos worked together with Sky & Telescope’s senior contributing correspondent Roger Sinnott, to figure out if the Moon played a roll in this infamous disaster.
Most of us know the story: the ship was supposedly unsinkable, and was steaming through an iceberg-ridden seas when it struck a huge chunk of ice, took on water, and went down, killing 1,500 people. Those facts are unsinkable. Or unassailable, so to speak. What the team found interesting, however, was that the Moon, along with the Sun and Earth may have played a curious role in the sinking.
Early in 1912, the Moon and Sun had lined up in such a way their gravitational pulls enhanced each other more than usual. That created a well-known effect called a spring tide, which was an unusually high tide. At the same time, the Moon was at perigee — that it is, it was at its closest Earth, and it was the closest perigee in 1,400 years. Perigee came within six minutes of a full Moon. To add icing to this orbitally dynamical cake, Earth had just passed through its own closest approach to the Sun (called perihelion) the day before. In astronomical terms, this was like the perfect storm of variables that may have contributed to another phenomenon: many more icebergs clogging up the sea lanes that year.
How would this have happened? According to the Texas State group, the fate of the Titanic was sealed by the prevalence of grounded and stranded icebergs. Icebergs calve off of glaciers in Greenland and take to the seas. As they travel south, many get stuck in the shallow waters off the coasts of Labrador and Newfoundland. Normally, icebergs remain in place and cannot resume moving southward until they’ve melted enough to refloat or the tide rises high enough for them to float free. A single iceberg can become stuck multiple times on its journey southward, a process that can take several years. The unusually high tide in Jan. 1912 would have been enough to dislodge many of those icebergs and move them back into the southbound ocean currents, where they would have just enough time to reach the shipping lanes for that fateful encounter with the Titanic.
You can read more of this fascinating story in the April 2012 edition of Sky & Telescope magazine.
March 11, 2012 at 8:30 am | Leave a Comment
No UFOs Here
Unless you’ve been buried under a blanket of clouds the past few weeks, you’ve probably noticed some bright lights in the western sky just after sunset. Aside from the Moon (and you know what that looks like, don’t you?), you might be wondering what they are. Well, if they’re not moving rapidly (like changing position over the space of a few minutes, as aircraft would do), then what you’re seeing are the planets Venus and Jupiter. Here’s tonight’s view of the pair, well after sunset. You won’t see Mercury (too close to the Sun), but you can’t fail to notice how dazzling the two planets appear these early springish nights.
If you have binoculars or a small telescope, check out Jupiter. You might be able to see its four largest moons. They’ll look like little pinpoints of light on either side of Jupiter.
The next couple of nights, these two planets snuggle up really close together in the western sky. Once you’ve found them, and turn toward the east and look for Mars snuggled up underneath the constellation, Leo the Lion. An hour or two later, you should be able to find Saturn just rising in the East. It’s a planet spectacular!
Of course, there are a lot of other things to look at in the sky this month, so don’t run back inside after you’ve seen the planet. Dress warmly (if it’s cold where you are), and explore that sky! There’s a lot to be found.
By the way, check out “Our Night Sky” at Astrocast.TV for a short program I did on what’s up this month. It’s free to embed on observatory and planetarium Web sites (with proper credit, of course), so check it out!
March 10, 2012 at 13:01 pm | Leave a Comment
Is There No End to Its Incessant Demands?
How did I miss this story? Early in February, the folks working with the Chandra X-ray Observatory announced that they’ve been watching the black hole at the heart of the Milky Way Galaxy munching down on asteroids. According to them, this happens pretty frequently. They’ve seen the evidence: once-a-day x-ray flares from Sagittarius A* (that’s the name given to our central black hole), or Sgr A* for short. The flares last a few hours, and have also been seen in infrared light by detectors at the Very Large Telescope in Chile.
The idea is that there is a cloud around Sgr A* containing hundreds of trillions of asteroids and comets. Where did they come from? Astronomers suggest that this debris collection is made of material stripped from the parent stars by the force of gravity.
An asteroid that gets too close to another object, such as a star or planet, can get thrown into an orbit that places it on a heading for Sgr A*. If it gets too close — say within 100 million miles of the black hole (about the distance between Earth and the Sun) it would be torn into pieces as it encountered the tidal forces from the black hole. These fragments would be vaporized as they pass through the hot, thin gas that continually flows toward Sgr A*. This is very similar to what happens to a meteor when it encounters Earth’s atmosphere for example. It heats up and glows, and eventually it vaporizes, and we see a flare marking the end of the meteor’s trip. When an object does this near Sgr A*, we can see it in x-rays and infrared. Whatever’s left of the asteroid gets sucked into the black hole.
This is kind of a cool thing to see at an object so far away, and Chandra’s still on the case. Over the next year or so, the satellite will study more of these things that go “fuff” in the night near Sgr A*.
March 8, 2012 at 9:43 am | Leave a Comment
What You Should Know
I see that “big” media has picked up on the idea of solar storms, in the wake of two most recent and very strong X-class events on the Sun. The headlines are breathless and I’ve already spotted some science bloopers on some sites that should know better (sites that used to have good science reporters, but who let them go in order to concentrate on important things, like Snooki’s baby).
Anyway, for all news about solar activity, I first turn to Spaceweather.com. The folks there have noted the impact of the coronal mass ejection was light at first, but warn it could pick up in the coming hours. Thus, people who live at high latitudes — northern regions around 50 degrees north or more — should get to see even MORE auroral displays than usual. If the storms get strong enough, those of us at lower latitudes might get to glimpse some aurorae, too.
All this solar activity is actually pretty much on schedule for the Sun. It goes through cycles of high and low activity, and we’re headed into a time of very high activity called “solar maximum”. So, increased numbers of flares and coronal mass ejections and sunspots are part of this process. It’s perfectly normal and nothing to get worried about. But, there will be the big media reports, and there will be some fascinating whack jobs tying this to something mysterious and paranormal.
That, too, is perfectly normal and nothing to get excited about.
Space weather, which is a term that covers all the solar-caused and geomagnetic disturbances that occur in near-Earth space, does have its down sides. While we gaze at lovely aurorae, giant disturbances in Earth’s uppermost atmospheric layers and nearby space can disrupt power grids, satellite communications, GPS signals, and many other bits of our modern technology. So, that IS of concern, and during such events you will read reports that warns of GPS outages or communications outages due to space weather (solar storms). This happens because these bits of technology rely on radio signals which bounce off the layers of our atmosphere in order to propagate (travel) long distances on our planet. In the case of GPS, those signals go THROUGH the atmosphere. So, if the upper atmosphere is disturbed by space weather, those signals can get broken up, delayed, or even lost. It’s an interesting and potentially dangerous side-effect of living near a star.
A while back we worked with MIT’s Haystack Observatory on a series of short videos about space weather. The series is called Space Weather FX. You can watch the whole series here and learn more about the effects that the Sun has on us and our technology. Also keep an eye on Spaceweather.com for the latest and most accurate info on solar activity.
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Copyright 2013, Carolyn Collins Petersen
Image of Horsehead Nebula: T.A.Rector (NOAO/AURA/NSF) and Hubble Heritage Team (STScI/AURA/NASA)
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