Universe Today

September 11, 2009December 24, 2015 by Nancy Atkinson

Earth From Space: Plankton Bloom

This Envisat image captures a plankton bloom in the Barents Sea. Credit: ESA

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What a gorgeous shot of our blue planet! This Envisat satellite image taken on August 19, 2009 captures a plankton bloom larger than the country of Greece stretching across the Barents Sea off the tip of northern Europe. The land visible across the bottom of the image belongs to Norway (left) and Russia’s Murmansk Oblast.

Plankton, the most abundant type of life found in the ocean, are microscopic marine plants that drift on or near the surface of the sea. Microscopic plankton have been called ‘the grass of the sea’ because they are the basic food on which all other marine life depends.

The colorful blossoming bloom in the Barents Sea, a rather deep shelf sea with an average depth around 230 m, is approximately 136,000 sq km. In comparison, Greece has a land area of 131,940 sq km.

For more about this image, see this page from ESA.

September 11, 2009December 24, 2015 by Tammy Plotner

Weekend SkyWatcher’s Forecast – September 11-13, 2009

Greetings, fellow SkyWatchers! Now that the Moon is backing off the early evening skies, it’s time to enjoy some more elusive targets – like ones that are gone in the “blink” of an eye, or “veiled” in mystery… While you might think all of these are telescope-only domain, if you’ve got dark skies and eyes, you might be surprised! Why not take some time this weekend to get out your telescopes or binoculars and have some fun? There’s some tasty summer treats waiting on you, and I’ll see you in the backyard…

Friday, September 11, 2009 – Today we celebrate the birthday of Sir James Jeans. Born in 1877 on this date, English-born Jeans was an astronomical theoretician. At the beginning of the twentieth century, Jeans worked out the fundamentals of the process of gravitational collapse. This was an important contribution to the understanding of the formation of solar systems, stars, and galaxies.

While we are studying some of the summer’s finest objects, we’d be remiss if we didn’t look at another cosmic curiosity—the ‘‘Blinking Planetary.’’ Located a couple of degrees east of visible star Theta Cygni, and in the same lower power field as 16 Cygni (RA 19 44 48 Dec +50 31 30), it is formally known as NGC 6826.

Viewable in even small telescopes at mid-to-high power, you’ll learn very quickly how its name came about. When you look directly at it, you can only see the central 9th magnitude star. Now, look away. Focus your attention on visual double 16 Cygni. See that? When you avert, the nebula itself is visible. This is actually a trick of the eye. The central portion of our vision is more sensitive to detail and will only see the central star. At the edge of our vision, we are more likely to see dim light, and the planetary nebula appears. Located around 2,000 light-years from our Solar System, it doesn’t matter if the Blinking Planetary is a trick of the eye or not. . .because it’s cool! Also known as Herschel IV.73 and Caldwell object 16, this tiny planetary shows an abundance of carbon and dust pockets in its structure. It skyrocketed to fame when viewed by the Hubble Space Telescope (HST), which revealed the mysterious red ‘‘FLIERS,’’ whose bow shocks point toward this planetary nebula instead of away
from it!

Saturday, September 12, 2009 – Today we note two births: Arthur von Auwers (1838), who calculated stellar distances; and Guillaume Le Gentil (1725), who was a frustrated Venus transit observer! Tonight, do your best not to be frustrated as we encourage those with larger binoculars and telescopes to head for a dark sky location. We are going on a quest… the quest for the holy ‘‘Veil.’’

By no means is the Veil Nebula Complex an easy one. The brightest portion, NGC 6992 (RA 20 56 20 Dec +31 41 48), can be spotted in large binoculars, and you can find it just slightly south of a central point between Epsilon and Zeta Cygni. NGC 6992 is much better in a 6″ scope, however, and low power is essential to see the long ghostly filaments that span more than a degree of sky.

About 2.5 degrees west-southwest, and incorporating star 52, is another long narrow ribbon of what may be classified as a supernova remnant. When aperture reaches the 12? range, so does the true breadth of this fascinating complex. It is possible to trace these long filaments across several fields of view. They sometimes dim and at other times widen, but like watching a surreal solar flare, you will not be able to tear your eyes away from this area. Another undesignated area lies between the two NGCs, and the whole 1,500-light-year-distant area spans over 2.5 degrees. Sometimes known as the Cygnus Loop, it’s definitely one of late summer’s finest objects.

Sunday, September 13, 2009 – Your first challenge for this morning is to check out the last quarter Moon and look for Mars nearly touching it!

On this date in 1922, the highest air temperature ever recorded at the surface of Earth occurred. The measurement was taken in Libya and burned in at a blistering 136F (58C), but did you know that the temperatures in the sunlight on the Moon are double that? If you think the surface of the Moon is a bit too warm for comfort, then know surface temperatures on Mars average only about 80F (27C) during the day!

Tonight, let’s take the time to hunt down an often overlooked globular cluster—M56. Located roughly midway between Beta Cygni and Gamma Lyrae (RA 19 15 35.50 Dec +30 11 04.2), this Class X globular was discovered by Charles Messier in 1779 on the same night he discovered a comet and was later resolved by Herschel.

At magnitude 8 and small in size, it’s a tough call for a beginner with binoculars but is a very fine telescopic object. With a general distance of 33,000 light-years, this globular resolves well with larger scopes but doesn’t show as much more than a faint, round area with small aperture. However, the beauty of the chains of stars in the field makes it quite worth the visit! While you’re there, look carefully: M56 is one of the very few objects for which the photometry of its variable stars was studied strictly with amateur telescopes. Although one bright variable had been known previously, up to a dozen more have recently been discovered. Of those, six had their variability periods determined using CCD photography and telescopes just like yours!

Until next week? Enjoy!

This week’s awesome images are (in order of appearance): Sir James Jeans (widely used public image), NGC 6826: the Blinking Planetary (credit—Hubble Space Telescope/NASA), The Veil Nebula (credit—NOAO/AURA/NSF), Mars (credit—NASA) and M56 (credit—Palomar Observatory, courtesy of Caltech). We thank you so much!

September 10, 2009April 26, 2016 by Fraser Cain

Schwarzschild Radius

Magnetic field around a black hole. Image credit: NASA

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A black hole is an object where the gravity is so powerful that nothing, not even light can escape it. They’re called black holes because they emit no radiation. If you take any object and compress it down, there will be a point that it becomes a black hole. If you could compress the Sun down to a radius of 2.5 km, it would be come a black hole. For the Earth, that radius is 0.9 cm. And a large mountain might be smaller than a nanometer. That radius is called the Schwarzschild Radius.

The term was named after the mathematician Karl Schwarzschild, who first developed the formula: R_{s = 2 GM/c². M is the mass of the body, G is the universal constant of gravitation, and c is the speed of light. You can use this formula to calculate the Schwarzschild radius of any object.}

And so, an object smaller than its Schwarzschild radius is known as a black hole. The surface of a black hole acts as an event horizon; a point at which nothing, not even light or radiation can escape it.

What actually happens to the mass within the Schwarzschild radius is a mystery. Some theorists believe that an extremely dense state of matter will stop the black hole from compressing any further, while others believe that the black hole will continue compressing infinitely down. It’s unknown if you would encounter the black hole itself when passing through the event horizon, or if you would still continue to travel down to the compressed inner black hole itself. Whatever the case, once you pass within the Schwarzschild radius, there’s no escape.

We have written many articles about black holes for Universe Today. Here’s an article about how you can maximize your time falling into a black hole. And here’s an article about the search for medium-sized black holes.

Want more information? Check out the formula from Wolfram Research, and here’s more info from Swinburne Astronomy Online.

We have recorded an episode of Astronomy Cast all about black holes. Check it out here: Episode 18 – Black Holes Big and Small.

September 10, 2009September 10, 2009 by Nancy Atkinson

NASA, ATK Unleash Ares Engine in Test Firing

In an impressive show of the power and might of the new Ares rocket, NASA and ATK Space systems successfully completed the first full-scale, full-duration test firing of the first stage motor for the potential successor to the space shuttle. The two-minute burn was powered with 22 million horsepower, and this first stage motor will generate up to 3.6 million pounds of thrust, or lifting power, at launch. Flames shot out twice as long as the rocket itself, at temperatures where steel boils and sand turns to glass — about 4,500 degrees Fahrenheit (2,480 degrees Celsius). 650 sensors sampled data from the test firing with rates up to 2000 samples a second. “We got an incredible amount of data today, ” Alex Priskos, first stage manager for Ares Projects, “and we were looking at 46 different objectives, but we should be able to understand every aspect of this motor, including strengths and weaknesses, and ultimately deliver the safest and most reliable motor possible.”
Continue reading “NASA, ATK Unleash Ares Engine in Test Firing”

September 10, 2009December 24, 2015 by Tammy Plotner

IYA Live Telescope Today: Messier 93

At last… Some clear skies in Central Victoria! (and i thought ohio was bad…) If you had a chance to check on our IYA Live Telescope today, you got a treat. We broadcast the “Running Man Nebula” for awhile, then switched over to Puppis as it rose to pick up Messier 93. Need a replay? We saved one for you…

Messier 93 (also known as M 93 or NGC 2447) is an open cluster in the constellation Puppis. It was discovered by Charles Messier in 1781.

M93 is at a distance of about 3,600 light years from Earth and has a spatial radius of some 10 to 12 light years. Its age is estimated at some 100 million years.

As always, keep checking periodically with the link on the left. It can’t stay cloudy forever… Can it?!?

Factual Information courtesy of Wikipedia.

September 10, 2009May 2, 2022 by Fraser Cain

What is Sagittarius A*?

Detection of an unusually bright X-Ray flare from Sagittarius A*, a supermassive black hole in the center of the Milky Way galaxy. Credit: NASA/CXC/Stanford/I. Zhuravleva et al.

At the very heart of the Milky Way is a region known as Sagittarius A*. This region is known the be the home of a supermassive black hole with millions of times the mass of our own Sun. And with the discovery of this object, astronomers have turned up evidence that there are supermassive black holes at the centers most most spiral and elliptical galaxies.

The best observations of Sagittarius A*, using Very Long Baseline Interferometry (VLBI) radio astronomy have determined that it’s approximately 44 million km across (that’s just the distance of Mercury to the Sun). Astronomers have estimated that it contains 4.31 million solar masses.

Of course, astronomers haven’t actually seen the supermassive black hole itself. Instead, they have observed the motion of stars in the vicinity of Sagittarius A*. After 10 years of observations, astronomers detected the motion of a star that came within 17 light-hours distance from the supermassive black hole; that’s only 3 times the distance from the Sun to Pluto. Only a compact object with the mass of millions of stars would be able to make a high mass object like a star move in that trajectory.

The discovery of a supermassive black hole at the heart of the Milky Way helped astronomers puzzle out a different mystery: quasars. These are objects that shine with the brightness of millions of stars. We now know that quasars come from the radiation generated by the disks of material surrounding actively feeding supermassive black holes. Our own black hole is quiet today, but it could have been active in the past, and might be active again in the future.

Some astronomers have suggested other objects that could have the same density and gravity to explain Sagittarius A, but anything would quickly collapse down into a supermassive black hole within the lifetime of the Milky Way.

We have written many articles about Sagittarius A. Here’s an article about how the Milky Way’s black hole is sending out flares, and even more conclusive evidence after 16 years of observations.

Here’s an article from NASA back in 1996 showing how astronomers already suspected it was a supermassive black hole, and the original ESO press release announcing the discovery.

We have recorded an episode of Astronomy Cast all about the Milky Way. Give it a listen: Episode: 99 – The Milky Way

Source: Wikipedia

September 10, 2009December 24, 2015 by Nancy Atkinson

Anticipated Joint Experiment with Chandrayaan-1 and LRO Failed

India Moon Mission — Artist concept of Chandrayaan-1 orbiting the moon. Credit: ISRO

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A highly anticipated Bi-static radar experiment to look for possible water ice hiding in polar craters on the Moon failed due to the deterioration and eventual loss of the Chandrayaan-1 lunar orbiter. “Everything worked out as best as could be hoped, except for one thing,” said Paul Spudis, principal investigator for Chandrayaan-1’s radar instrument, Mini-SAR. “It turned out Chandrayaan-1 wasn’t pointed at the Moon when we were taking the data, but we didn’t know that at the time. So, the Bi-static attempt was a failure.” The experiment was attempted on August 20, and one week later the Chandrayaan-1 spacecraft failed completely due to overheating. The Indian Space Research Organization (ISRO) admitted they underestimated the amount of heat radiating from the Moon and didn’t have enough thermal protection on the spacecraft.

Spudis told Universe Today that both Chandrayaan-1 and the Lunar Reconnaissance Orbiter were in the right locations to do the experiment, but Chandrayaan-1 was pointed in the wrong direction. “We didn’t realize it, but the spacecraft was on its last legs at that point. When we commanded it to get into a certain attitude to do the experiment, it just wasn’t in that attitude, and we had no way of knowing it.”

The experiment required tricky maneuvers for both Chandrayaan-1 and LRO. The test was timed to coincide when both spacecraft were only 20 kilometers (12.4 miles) apart over Erlanger Crater near the Moon’s north pole. Chandrayaan-1’s radar was to transmit a signal to be reflected off the interior the crater to be picked up by LRO. Comparing the signal that would have bounced straight back to Chandrayaan-1 with the signal that bounced at a slight angle to LRO would have provided unique information about any water ice that may be present inside the crater.

Erlanger crater imaged by LRO. Credit: NASA

Because of the loss of the star trackers earlier this year on Chandrayaan-1, Spudis said they weren’t certain during the test what direction the spacecraft was pointing. “We thought it was oriented in the right attitude, but it turned out it was not. So we didn’t send the radar beam into the crater like we had hoped, so therefore we didn’t get any echoes from it. It is disappointing, but that’s the space biz, that’s the way things go.”

Spudis said the international coordination required for the experiment between ISRO, JPL, NASA and the Applied Physics Lab worked exceptionally well. “Everyone did a great job and gave us great support on it. We came very close and the actual encounter was better than predicted. So everything worked except for the Chandrayaan-1 spacecraft.”

The teams were getting ready to try a repeat of the experiment, during the last weekend in August when Chandrayaan-1 quit communicating. “We were going to have another opportunity where the spacecraft were going to be close together over a different crater on the north pole,” Spudis said, “but then we lost the spacecraft on that Thursday. So that was disappointing. We gave it our best shot, but that’s the way it goes.”

But Spudis said he has his team have been busy focusing on studying and understanding the monostatic data they do have.

“We have some excellent quality data collected from mid- Feb to mid-April of this year,” he said. “We were able to get data from over 90% of both poles. We’re really just getting started analyzing it.”

There are missing pieces of data, especially directly at the poles because the instrument was a side-looking radar. The Mini-SAR always looked off nadir, off to one side of the ground track that is directly below the spacecraft. “So if you are in perfectly polar orbit, you will never image the poles because you are always looking off to the side,” Spudis explained. ” So we have these black zones around the poles. But we do have a lot of coverage around the poles of terrain that is in permanent darkness. We are studying that right now, and In fact, I am in the midst of writing up our first paper, and we’ll have some interesting results from that.”

Spudis said the loss of Chandrayaan-1 wasn’t totally unexpected due to the problems the spacecraft had been experiencing, but no one thought it would happen quite this quickly. “It was a little unexpected how rapidly it happened, how soon the end came,” he said. “Because the spacecraft had been having problems, we had been living with the various losses of capabilities, and we just kept soldiering through hoping that everything would work out. The timing was unfortunate.”

In addition the substantial amount of data received from Chandrayaan-1 data, Spudis is also looking to the data that will be coming from LRO. “LRO has a radar instrument that is a more advanced version than the one on Chandrayaan,” he said. “The difference is that there are two frequencies instead of one, and it has two resolutions – a normal resolution similar to India’s version on Chandrayaan-1 one, as well as a zoom version, a hi-res mode, with a factor of 6 or 7 better than the nominal mode.”

Spudis said LRO’s Mini-RF has been turned on during the LRO commissioning and so far it has been used to support the LCROSS impact. “They wanted to look at targets near the south pole, so we took some data for them. That data looks very interesting as well.”

For more information on Spudis’ work, check out his website.

September 10, 2009December 24, 2015 by Jerry Coffey

When Was Mars Discovered?

This full-circle view from the panoramic camera (Pancam) on NASA's Mars Exploration Rover Spirit shows the terrain surrounding the location called "Troy," where Spirit became embedded in soft soil during the spring of 2009. Credit: NASA/JPL

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It is impossible to know the answer to ”when was Mars discovered”. It is bright enough to be seen in the night sky without binoculars or a telescope and has been documented for at least 4,000 years.

If you were to change the question a little to ”who first theorized that Mars was a planet”, then an answer can be found. Nicolaus Copernicus is the first astronomer to postulate that Mars and a few other bodies known at the time were planets. The heliocentric theory that he published in 1543 marked the first time that astronomers widely considered the possibility that the Sun was the center of the Solar System instead of the Earth.

While no one knows who first discovered Mars, we do know who made many of the discoveries about the planet. It is known that Tycho Brahe, a Danish astronomer made accurate calculations of the position of Mars as early as 1576. Johannes Kepler theorized that the orbit of Mars was elliptical in contradiction to what astronomers believed at the time. He soon expanded that theory to encompass all planets. In 1659, Christian Huygens, a Dutch astronomer drew Mars with the observations he made using a telescope he designed himself. He also discovered a strange feature on the planet that became known as Syrtis Major.

On November 28, 1964, Mariner 4 was launched successfully on an eight-month voyage to the Red Planet. It made its first flyby on July 14, 1965, collecting the first close-up photographs of another planet. The pictures showed many impact craters, some of them touched with frost in the chill Martian evening. The Mariner 4 spacecraft was able to function for about three years in solar orbit, continuing long-term studies of the solar wind environment and making coordinated measurements with Mariner 5.

There are currently six spacecraft in orbit around Mars or on its surface and several more are in the planning or design stages. Five are gathering data at an amazing rate, the other(Phoenix) is non-functioning. New discoveries like subsurface water ice and methane plumes in the atmosphere are being made on a regular basis. Scientists may not be able to give an answer to ”when was Mars discovered”, but they can offer answers to thousands of other questions and the list is growing as we speak.

We have written many articles about the study of Mars. Here an article about how methane is being produced on Mars, and the possible discovery of life on Mars.

Here are some additional articles about the early observations of Mars, and here’s a whole book about observing Mars.

We have recorded an entire episode of Astronomy Cast about the planet Mars. Listen to it here, Episode 52: Mars.

Source: NASA

September 10, 2009 by Fraser Cain

Aliens

September 10, 2009May 4, 2017 by Fraser Cain

K-T Boundary

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What killed the dinosaurs? That’s a question that has puzzled paleontologists since dinosaurs were first discovered. Maybe the global climate changed, maybe they were killed by disease, volcanoes, or the rise of mammals. But in the last few decades, a new theory has arisen; an asteroid strike millions of years ago drastically changed the Earth’s environment. It was this event that pushed the dinosaurs over the edge into extinction. What’s the evidence for this asteroid impact? A thin dark line found in layers of sediment around the world; evidence that something devastating happened to the planet 65 million years ago. This line is known as the K-T boundary.

What is the K-T boundary? K is actually the traditional abbreviation for the Cretaceous period, and T is the abbreviation for the Tertiary period. So the K-T boundary is the point in between the Cretaceous and Tertiary periods. Geologists have dated this period to about 65.5 million years ago.

When physicist Luis Alvarez and geologist Walter Alvarez studied the K-T boundary around the world, they found that it had a much higher concentration of iridium than normal – between 30-130 times the amount of iridium you would expect. Iridium is rare on Earth because it sank down into the center of the planet as it formed, but iridium can still be found in large concentrations in asteroids. When they compared the concentrations of iridium in the K-T boundary, they found it matched the levels found in meteorites.

The researchers were even able to estimate what kind of asteroid must have impacted the Earth 65.5 million years ago to throw up such a consistent layer of debris around the entire planet. They estimated that the impactor must have been about 10 km in diameter, and release the energy equivalent of 100 trillion tons of TNT.

When that asteroid struck the Earth 65.5 million years ago, it destroyed a region thousands of kilometers across, but also threw up a dust cloud that obscured sunlight for years. That blocked photosynthesis in plants – the base of the food chain – and eventually starved out the dinosaurs.

Researchers now think that the asteroid strike that created the K-T boundary was probably the Chicxulub Crater. This is a massive impact crater buried under Chicxulub on the coast of Yucatan, Mexico. The crater measures 180 kilometers across, and occurred about 65 million years ago.

Geologists aren’t completely in agreement about the connection between the Chicxulub impact and the extinction of the dinosaurs. Some believe that other catastrophic events might have helped push the dinosaurs over the edge, such as massive volcanism, or a series of impact events.

We have written many articles about the K-T boundary for Universe Today. Here’s an article about how the dinosaurs probably weren’t wiped out by a single asteroid, and here’s an article about how asteroids and volcanoes might have done the trick.

Here’s more information from the USGS, and an article from NASA.

We have recorded an episode of Astronomy Cast all about asteroid impacts. Listen to it here: Episode 29: Asteroids Make Bad Neighbors.

Reference:
USGS