Jan 03

What’s Up in the Sky

What’s Up in the Sky – January, 2017

2016 – An Historic Year for Astronomy

This is a time of year traditionally known for reflection and anticipation and last year was also been a year of milestones for astronomers. It seems appropriate to look back on major events and discoveries that will make 2016 historic.

Thought by many to be the greatest discovery of the year, as well as one of the greatest in history, was the detection of gravitational waves, ripples in the fabric of spacetime and the result of a cataclysmic event in the distant universe. Although the gravitational waves were detected in September of 2015, it took until February of this year for scientists to verify the observation after much painstaking analysis of the data.

The gravitational waves were a result of a merger of two black holes to produce a single, more massive, black hole, 1.3 billion years ago. The observation confirmed a major prediction of Albert Einstein’s 1915 general theory of relativity and gives astronomers a completely new method by which to study the universe. The discovery was made using the LIGO (Laser Interferometer Gravitational-wave Observatory) detectors, located in Hanford WA and Livingston, LA.

On July 4th, the Juno spacecraft entered into orbit around the giant planet, Jupiter. Although not the first spacecraft to study Jupiter (there have been eight others) nor even the first to orbit the planet (that was Galileo in 1995), Juno is unique in that its orbit is polar rather than equatorial and brings it far closer to the giant planet’s cloud tops than any other spacecraft. With its mission still in its early stages, we can look forward to many great discoveries when Juno probes Jupiter’s deep structure, studies its atmospheric circulation and attempts to learn more about the high-energy physics of its magnetic field.

In September, the European Space Agency’s Rosetta spacecraft ended its mission with a soft landing on the surface of Comet 67P. After two years of study that included ground-breaking observations at extremely close distances, Rosetta has provided scientists with a wealth of data that should keep them busy for years.

The New Horizons spacecraft was still in the news as it finished returning all the data from its flyby of Pluto. One major discovery was that of a massive ice sheet whose top lies 2.5 kilometers below Pluto’s mean elevation. Most likely an impact basin, it may have been formed by a glancing impact of a 200-kilometer body.

And the new year promises to be an exciting one here in the U.S. with next August’s “Great American Solar Eclipse”, an event you will NOT want to miss. It will be the greatest thing you have ever witnessed up in the sky.

Dec 13

Big Science in Small Packages

By Marcus Woo

About 250 miles overhead, a satellite the size of a loaf of bread flies in orbit. It’s one of hundreds of so-called CubeSats—spacecraft that come in relatively inexpensive and compact packages—that have launched over the years. So far, most CubeSats have been commercial satellites, student projects, or technology demonstrations. But this one, dubbed MinXSS (“minks”) is NASA’s first CubeSat with a bona fide science mission.

Launched in December 2015, MinXSS has been observing the sun in X-rays with unprecedented detail. Its goal is to better understand the physics behind phenomena like solar flares – eruptions on the sun that produce dramatic bursts of energy and radiation.

Much of the newly-released radiation from solar flares is concentrated in X-rays, and, in particular, the lower energy range called soft X-rays. But other spacecraft don’t have the capability to measure this part of the sun’s spectrum at high resolution—which is where MinXSS, short for Miniature Solar X-ray Spectrometer, comes in.

Using MinXSS to monitor how the soft X-ray spectrum changes over time, scientists can track changes in the composition in the sun’s corona, the hot outermost layer of the sun. While the sun’s visible surface, the photosphere, is about 6000 Kelvin (10,000 degrees Fahrenheit), areas of the corona reach tens of millions of degrees during a solar flare. But even without a flare, the corona smolders at a million degrees—and no one knows why.

One possibility is that many small nanoflares constantly heat the corona. Or, the heat may come from certain kinds of waves that propagate through the solar plasma. By looking at how the corona’s composition changes, researchers can determine which mechanism is more important, says Tom Woods, a solar scientist at the University of Colorado at Boulder and principal investigator of MinXSS: “It’s helping address this very long-term problem that’s been around for 50 years: how is the corona heated to be so hot.”

The $1 million original mission has been gathering observations since June.

The satellite will likely burn up in Earth’s atmosphere in March. But the researchers have built a second one slated for launch in 2017. MinXSS-2 will watch long-term solar activity—related to the sun’s 11-year sunspot cycle—and how variability in the soft X-ray spectrum affects space weather, which can be a hazard for satellites. So the little-mission-that-could will continue—this time, flying at a higher, polar orbit for about five years.

If you’d like to teach kids about where the sun’s energy comes from, please visit the NASA Space Place: http://spaceplace.nasa.gov/sun-heat/

Astronaut Tim Peake on board the International Space Station captured this image of a CubeSat deployment on May 16, 2016. The bottom-most CubeSat is the NASA-funded MinXSS CubeSat, which observes soft X-rays from the sun—such X-rays can disturb the ionosphere and thereby hamper radio and GPS signals. (The second CubeSat is CADRE — short for CubeSat investigating Atmospheric Density Response to Extreme driving – built by the University of Michigan and funded by the National Science Foundation.) Credit: ESA/NASA

This article is provided by NASA Space Place. With articles, activities, crafts, games, and lesson plans, NASA Space Place encourages everyone to get excited about science and technology. Visit spaceplace.nasa.gov to explore space and Earth science!

Dec 03

What’s Up in the Sky

What’s Up in the Sky – December, 2016

December’s Sky Has Much to Offer

December can be a frustrating month for observing due to its notoriously bad weather, but the legends and lore associated with those hidden sky wonders can add wonder to the season.

Venus is currently doing a good job posing as the Christmas Star albeit in the wrong direction. She, along with two of her companions, Mercury and Mars, can be found all lined up above the southwest horizon after sunset.

Venus is by far the brightest and most easily visible of the three and, in early December, is almost exactly half way in between the others, about twenty degrees (two fists held at arm’s length) from each one. Mercury is to the lower right of Venus, near the southwest horizon, and is rather dim so binoculars or a small telescope will probably be needed to spot it. Mars is to the upper left of Venus and should be easy to see high above the southern horizon.

This week you can also let the crescent Moon be your guide. Keeping in mind the need for a clear horizon and optical aid (binoculars), go out tomorrow around 5:30 p.m. and look for a thin crescent Moon near the southwestern horizon. Mercury will be to its left and even closer to the horizon but on Thursday it will be right below the Moon and both should be a little easier to find.

The following nights the Moon will pass Venus and then, on Sunday, December 4, now approaching first quarter, will be just to the right (west) of Mars. As the month progresses, the Venus-Mars separation will shrink considerably as the two approach a late January close encounter.

You early birds should not feel left out since you have Jupiter dominating the pre dawn sky high in the south. It will be joined by a waning crescent Moon on December 22.

If the weather does not allow these observations, we can always remember the connection between celestial objects and the celebrations of the seasons. Many cultures over the centuries have had stories and legends about this time of year, most concerned with the return of the Sun after the winter solstice. All autumn the Sun sets at a point farther south on the horizon as the days get colder and shorter. Early people were concerned about its return.

Many of our traditions involve the theme of light and have their origins in early rituals meant to coax the Sun back.
The Norsemen of northern Europe used to honor the Sun with a feast called Yule, during which logs of oak were burned. We are still familiar with the Yule log. Candles in windows and luminarias on paths are meant to light the way for Mary and Joseph. Wreaths of holly, with its red berries, were originally used to represent the Sun, and evergreens, with their permanent foliage, were considered symbols of eternal life and assurance of the Sun’s return.

So get out and enjoy the symbols of the Holiday Season that can be found up in the sky.
This month in history:
Dec. 3: Pioneer 10 spacecraft makes closest approach to Jupiter – 1973
Dec. 7: Gerard Kuiper born – 1905
Dec. 14: Gene Cernan, Apollo 17 astronaut, is last human to walk on Moon – 1972
Dec. 20: Founding of Mt. Wilson Solar Observatory – 1904
Dec. 24: Apollo 8 astronauts give us inspirational moment from lunar orbit – 1968
Dec. 25: Isaac Newton born – 1642

Nov 12

Dimming stars, erupting plasma, and beautiful nebulae

By Marcus Woo

Boasting intricate patterns and translucent colors, planetary nebulae are among the most beautiful sights in the universe. How they got their shapes is complicated, but astronomers think they’ve solved part of the mystery—with giant blobs of plasma shooting through space at half a million miles per hour.

Planetary nebulae are shells of gas and dust blown off from a dying, giant star. Most nebulae aren’t spherical, but can have multiple lobes extending from opposite sides—possibly generated by powerful jets erupting from the star.

Using the Hubble Space Telescope, astronomers discovered blobs of plasma that could form some of these lobes. “We’re quite excited about this,” says Raghvendra Sahai, an astronomer at NASA’s Jet Propulsion Laboratory. “Nobody has really been able to come up with a good argument for why we have multipolar nebulae.”

Sahai and his team discovered blobs launching from a red giant star 1,200 light years away, called V Hydrae. The plasma is 17,000 degrees Fahrenheit and spans 40 astronomical units—roughly the distance between the sun and Pluto. The blobs don’t erupt continuously, but once every 8.5 years.

The launching pad of these blobs, the researchers propose, is a smaller, unseen star orbiting V Hydrae. The highly elliptical orbit brings the companion star through the outer layers of the red giant at closest approach. The companion’s gravity pulls plasma from the red giant. The material settles into a disk as it spirals into the companion star, whose magnetic field channels the plasma out from its poles, hurling it into space. This happens once per orbit—every 8.5 years—at closest approach.

When the red giant exhausts its fuel, it will shrink and get very hot, producing ultraviolet radiation that will excite the shell of gas blown off from it in the past. This shell, with cavities carved in it by the cannon-balls that continue to be launched every 8.5 years, will thus become visible as a beautiful bipolar or multipolar planetary nebula.

The astronomers also discovered that the companion’s disk appears to wobble, flinging the cannonballs in one direction during one orbit, and a slightly different one in the next. As a result, every other orbit, the flying blobs block starlight from the red giant, which explains why V Hydrae dims every 17 years. For decades, amateur astronomers have been monitoring this variability, making V Hydrae one of the most well-studied stars.

Because the star fires plasma in the same few directions repeatedly, the blobs would create multiple lobes in the nebula—and a pretty sight for future astronomers.

If you’d like to teach kids about how our sun compares to other stars, please visit the NASA Space Place: http://spaceplace.nasa.gov/sun-compare/en/

This four-panel graphic illustrates how the binary-star system V Hydrae is launching balls of plasma into space. Image credit: NASA/ESA/STScI

This article is provided by NASA Space Place. With articles, activities, crafts, games, and lesson plans, NASA Space Place encourages everyone to get excited about science and technology. Visit spaceplace.nasa.gov to explore space and Earth science!

Sep 13

One Incredible Galaxy Cluster Yields Two Types of Gravitational Lenses

By Ethan SiegelSP-Logo-300.en

There is this great idea that if you look hard enough and long enough at any region of space, your line of sight will eventually run into a luminous object: a star, a galaxy or a cluster of galaxies. In reality, the universe is finite in age, so this isn’t quite the case. There are objects that emit light from the past 13.7 billion years—99 percent of the age of the universe—but none before that. Even in theory, there are no stars or galaxies to see beyond that time, as light is limited by the amount of time it has to travel.
But with the advent of large, powerful space telescopes that can collect data for the equivalent of millions of seconds of observing time, in both visible light and infrared wavelengths, we can see nearly to the edge of all that’s accessible to us.

The most massive compact, bound structures in the universe are galaxy clusters that are hundreds or even thousands of times the mass of the Milky Way. One of them, Abell S1063, was the target of a recent set of Hubble Space Telescope observations as part of the Frontier Fields program. While the Advanced Camera for Surveys instrument imaged the cluster, another instrument, the Wide Field Camera 3, used an optical trick to image a parallel field, offset by just a few arc minutes. Then the technique was reversed, giving us an unprecedentedly deep view of two closely aligned fields simultaneously, with wavelengths ranging from 435 to 1600 nanometers.

With a huge, towering galaxy cluster in one field and no comparably massive objects in the other, the effects of both weak and strong gravitational lensing are readily apparent. The galaxy cluster—over 100 trillion times the mass of our sun—warps the fabric of space. This causes background light to bend around it, converging on our eyes another four billion light years away. From behind the cluster, the light from distant galaxies is stretched, magnified, distorted, and bent into arcs and multiple images: a classic example of strong gravitational lensing. But in a subtler fashion, the less optimally aligned galaxies are distorted as well; they are stretched into elliptical shapes along concentric circles surrounding the cluster.

A visual inspection yields more of these tangential alignments than radial ones in the cluster field, while the parallel field exhibits no such shape distortion. This effect, known as weak gravitational lensing, is a very powerful technique for obtaining galaxy cluster masses independent of any other conditions. In this serendipitous image, both types of lensing can be discerned by the naked eye. When the James Webb Space Telescope launches in 2018, gravitational lensing may well empower us to see all the way back to the very first stars and galaxies.

If you’re interested in teaching kids about how these large telescopes “see,” be sure to see our article on this topic at the NASA Space Place: http://spaceplace.nasa.gov/telescope-mirrors/en/


Galaxy cluster Abell S1063 (left) as imaged with the Hubble Space Telescope as part of the Frontier Fields program. The distorted images of the background galaxies are a consequence of the warped space dues to Einstein’s general relativity; the parallel field (right) shows no such effects. Image credit: NASA, ESA and Jennifer Lotz (STScI)

This article is provided by NASA Space Place. With articles, activities, crafts, games, and lesson plans, NASA Space Place encourages everyone to get excited about science and technology. Visit spaceplace.nasa.gov to explore space and Earth science!

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