Friday, February 6, 2015

How Do We Study The Sun?

How Do We Study The Sun?:

A coronal mass ejection erupts from the Sun. Credit: NASA Goddard Space Flight Center


A coronal mass ejection erupts from the Sun. Credit: NASA Goddard Space Flight Center
A quick think about optical astronomy would have you imagine that most of it takes place at night. Isn’t that when the stars and galaxies come out to play? Well, that assumption makes at least one glaring error: Earth happens to be close to a star that is worthy of study. It’s called the Sun, and it only appears during the day.

We love being close to the Sun because it gives energy that gives us light. But that same energy can also be damaging to eyes and to instruments. Below are how amateurs and professionals alike safely observe our closest stellar neighbor.

Amateur astronomy

The safest way to observe the Sun is by projecting it on to a surface. By doing this, you’ll be able to see huge sunspots and you can also watch as the star marches through a solar eclipse — if you’re lucky enough to be in the area.

This is how Sky & Telescope suggests you get it done: “Poke a small hole in an index card with a pencil point, face it toward the Sun, and hold a second card three or four feet behind it in its shadow. The hole will project a small image of the Sun’s disk onto the lower card.”

The partial solar eclipse on Nov. 2, 2013 at its peak over Israel. Credit and copyright: Gadi Eidelheit.


The partial solar eclipse on Nov. 2, 2013 at its peak over Israel. Credit and copyright: Gadi Eidelheit.
If you prefer to look at the Sun directly, you must protect your eyes and your equipment (binoculars/telescope/camera) from looking at it unexposed. We’ll refer you again to the Sky & Telescope article for the best expertise, but in general, understand that you will need special equipment to do it safely.

Professional astronomy

There are numerous larger telescopes that are used on the ground, which typically have special filters to block out the damaging parts of the Sun’s light. We have a few examples below, but we’re sure you’ll come up with more examples from your own neighborhoods!

Of note, professional astronomers use multiple tools to look at the Sun. They can examine the Sun in different wavelengths of light to see its surface and corona. They can use spectroscopy to see the elements produced in different parts of the Sun. They can study its radiation using radar, or its interior using techniques such as acoustic interferometry.

  • U.S. National Solar Observatory: The observatory has two major optical facilities, called the Dunn Solar Telescope (Sacramento Peak) and the McMath-Pierce Solar Telescope (Kitt Peak). Luckily for the public, both are open to visitors. The observatory also is part of the Global Oscillation Network Group, which looks at acoustic waves inside the Sun using six stations spaced around the world.
  • Big Bear Solar Observatory‘s New Solar Telescope can view features on the Sun that are as small as 50 miles (80 kilometers) across. It saw “first light” in 2010 and for now, is the largest aperture solar telescope at 1.6 meters across.
  • For future-casting, look at the 4.24 meter Daniel K. Inouye Solar Telescope and four-meter European Solar Telescope.
But that’s not all we’ve got. Here are a few examples of space telescopes in orbit:

The Sun as viewed by the Solar and Heliospheric Observatory (NASA/SOHO)


The Sun as viewed by the Solar and Heliospheric Observatory (NASA/SOHO)
Solar and Heliospheric Observatory (SOHO): Launched in 1995, this NASA and European Space Agency is supposed to study the Sun’s interior, figure out more about the superheated solar corona or envelope that surrounds the Sun, and understand how the solar wind is created. It’s also a famous comet catcher and observer.

STEREO (Solar TErrestrial RElations Observatory): Launched in 2006, these twin spacecraft are in different parts of the Earth’s orbit: one ahead, and one behind. Their goal is to produce three-dimensional images of the Sun to improve space weather forecasting (specifically, when large eruptions on the Sun could disrupt Earth communications). As of early 2015, STEREO-B is not communicating with Earth.

Solar Dynamics Observatory: Launched in 2010, it aims to understand why the Sun has an 11-year solar cycle and to learn more about the Sun’s magnetic field and energy. The ultimate goal, again, is to improve space weather predictions.

We have written many articles about solar observatories, both ground and space-based, here on Universe Today. Here’s an article about the STEREO spacecraft seeing a tsunami on the Sun. We have recorded an episode of Astronomy Cast just about the Sun called The Sun, Spots and All.



About 

Elizabeth Howell is the senior writer at Universe Today. She also works for Space.com, Space Exploration Network, the NASA Lunar Science Institute, NASA Astrobiology Magazine and LiveScience, among others. Career highlights include watching three shuttle launches, and going on a two-week simulated Mars expedition in rural Utah. You can follow her on Twitter @howellspace or contact her at her website.

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Planck Mission Explores the History of Our Universe

Planck Mission Explores the History of Our Universe:


A festive portrait of our Milky Way galaxy shows a mishmash of gas, charged particles and several types of dust.


New data from Planck are helping scientists better understand the history and fabric of our universe, as well as our own Milky Way galaxy.






Posted by Nelio Inacio at 6:33 AM 0 comments

Rare Images of Red Sprites Captured at ESO

Rare Images of Red Sprites Captured at ESO:

Distant sprites (right) captured from ESO's VLT by Photo Ambassador Petr Horálek. (P. Horálek/ESO)

Red sprites (right) captured from ESO’s VLT platform by Petr Horálek. (P. Horálek/ESO)
At the ESO’s observatories located high in the Atacama Desert of Chile, amazing images of distant objects in the Universe are captured on a regular basis. But in January 2015, ESO photo ambassador Petr Horálek captured some amazing photos of much closer phenomena: red sprites flashing in the atmosphere high above distant thunderstorms.

The photo above was captured from ESO’s Paranal Observatory. A few days earlier during the early morning hours of Jan. 20 Petr captured another series of sprites from the La Silla site, generated by a storm over Argentina over 310 miles (500 km) away.

Sprites spotted from ESO's La Silla observatory by Petr Horálek


Sprites spotted from ESO’s La Silla observatory by Petr Horálek (left horizon)
So-named because of their elusive nature, sprites appear as clusters of red tendrils above a lighting flash, often extending as high as 55 miles (90 km) into the atmosphere. The brightest region of a sprite is typically seen at altitudes of over 40-45 miles (65-75 km).

Because they occur high above large storms, only last for fractions of a second and emit light in the portion of the spectrum to which our eyes are the least sensitive, observing sprites is notoriously difficult.

Read more: On the Hunt for High-Speed Sprites

These furtive atmospheric features weren’t captured on camera until 1989. Continuing research has since resulted in more images, including some from the International Space Station. When they are spotted, sprites – and their lower-altitude relatives blue jets – can appear as bright as moderate aurorae and have also been found to emit radio noise. It has even been suggested that looking for sprite activity on other planets could help identify alien environments that are conducive to life.

Find out more about sprite research from the University of Alaska Fairbanks, and check out the PBS NOVA program “At the Edge of Space” below about a sprite hunt in the skies over Denver, CO conducted by a team of American scientists and Japanese filmmakers.

Source: ESO



About 

A graphic designer in Rhode Island, Jason writes about space exploration on his blog Lights In The Dark, Discovery News, and, of course, here on Universe Today. Ad astra!

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Jupiter Reaches Opposition on February 6th

By Jove: Jupiter Reaches Opposition on February 6th:

Jupiter +Great Red Spot as seen on January 22nd 2015. Credit:


Jupiter +Great Red Spot as seen on January 22nd 2015. Credit and copyright: Efrain Morales Rivera.
Did you see the brilliant Full Snow Moon rising last night? Then you might’ve also noticed a bright nearby ‘star’. Alas, that was no star, but the largest planet in our solar system, Jupiter. And it was no coincidence that the king of the gas giants is near the Full Moon this February, as Jupiter reaches opposition this Friday on February 6th at 18:00 Universal Time or 1:00 PM EST.

As the term implies, opposition simply means that an outer planet sits opposite to the Sun. Mercury and Venus can never reach opposition. Orbiting the Sun once every 11.9 years, oppositions for Jupiter occur once every 399 days, or roughly every 13 months. This means that only one opposition for Jupiter can happen per year max, and these events precess forward on the Gregorian calendar by about a month and move one zodiacal constellation eastward per year.

Starry Night.


The apparent path of Jupiter through Spring 2015. Created using Starry Night Education Software.
Through a telescope, Jupiter exhibits an ochre disk 40” in diameter striped with two main cloud belts. The northern equatorial belt seems permanent, while the southern equatorial belt is prone to pulling a ‘disappearing act’ every decade of so, as last occurred in 2010. The Great Red Spot is another prominent feature gracing the Jovian cloud tops, though its appeared salmon to brick-colored in recent years and seems to be shrinking.

Jupiter rotates once every 9.9 hours, fast enough that you can watch one full rotation in a single night.

Photo by author


Jupiter near opposition in 2014. Photo by author.
It’s also fascinating to watch the nightly dance of Jupiter’s four large moons Io, Europa, Ganymede and Callisto as they alternatively cast shadows on the Jovian cloud tops and disappear into its shadow. Near opposition, this shadow casting activity is nearly straight back as seen from our perspective.  Here is the tiny ‘mini-solar system’ that fascinated Galileo and further convinced him that the Earth isn’t the center of the cosmos. Jupiter has 67 moons in all, though only 4 are within range of modest sized telescopes… Even 5th place runner up Himalia is a challenge near the dazzling disk of Jove at +14th magnitude.

Also watch for a phenomenon known as the Seeliger or Opposition Effect, a sudden surge in brightness like a highway retro-reflector in the night.

Opposition 2015 finds Jupiter just across the Leo-Cancer border in the realm of the Crab. Jupiter crossed from Leo into Cancer on February 4th, and will head back into the constellation of the Lion on June 10th. Jupiter then spends the rest of 2015 in Leo and heads for another opposition next year on March 8th.

Jupiter will also make a dramatic pass just 24’ — less than the diameter of the Full Moon — from Regulus on August 11th, though both are only 11.5 degrees east of the Sun in the dusk sky. Jupiter also forms a 1 degree circle with Regulus, Mercury and Jupiter 14.5 degrees east of the Sun on August 7th.

Jupiter reaches a maximum declination north for 2015 on April 7th at 18 degrees above the celestial equator. We’re still in a favorable cycle of oppositions for Jupiter for northern hemisphere viewers, as the gas giant doesn’t plunge south of the equator until September 2016.

Looking farther ahead, Jupiter reaches east quadrature on May 4th, and sits 90 degrees elongation from the Sun as the planet and its moons cast their shadows far off to the side from our Earthly perspective. We’re still also in the midst of a plane crossing: February 5th is actually equinox season on Jupiter! This also means that there’s still a cycle of mutual eclipses and occultations of the Jovian moons in progress. One such complex ballet includes (moons) on the night of February 26th.

February 26th. Starry Night


The close grouping of Io, Callisto and Ganymede on the night of February 26th. Created using Starry Night Education software.
And yes, it is possible to see the Earth transit the disk of the Sun from Jove’s vantage point. This last occurred in 2014, and will next occur in 2020.

But wait, there’s more. Jupiter also makes a thrilling pass near Venus on July 1st, when the two sit just 0.4 degrees apart. We fully expect a spike in “what are those two bright stars?” queries right around that date, though hopefully, the conjunction won’t spark any regional conflicts.

Stellarium


Jupiter, Regulus and the rising waning gibbous Moon on the evening of February 4th. Credit: Stellarium.
Solar conjunction for Jupiter then occurs on August 26th, with the planet visible in the Solar Heliospheric Observatory’s (SOHO) LASCO C3 camera from August 16th to September 6th.

Emerging into the dawn sky, Jupiter then passes 0.4 degrees from Mars on October 17th and has another 1.1 degree tryst with Venus on October 26th.

Looking for Jupiter in the daytime near the waxing gibbous Moon. Credit: Stellarium.


Looking for Jupiter in the daytime near the waxing gibbous Moon. Credit: Stellarium.
Let the Jovian observing season begin!

-Wonder what a gang of rogue space clowns is doing at Jupiter? Read Dave Dickinson’s original tale Helium Party and find out!



About 

David Dickinson is an Earth science teacher, freelance science writer, retired USAF veteran & backyard astronomer. He currently writes and ponders the universe from Tampa Bay, Florida.

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Skywatchers Identify Aircraft as They Pass in Front of the Sun

Skywatchers Identify Aircraft as They Pass in Front of the Sun:

An Aer Lingus Airbus A320 passes in front of the Sun on Feb. 4, 2015. Credit and copyright: Chris Lyons.


An Aer Lingus Airbus A320 passes in front of the Sun on Feb. 4, 2015. Credit and copyright: Chris Lyons.
It’s all about timing and location.

You’ve probably seen images we’ve posted on Universe Today of planes crossing in front of the Sun or the Moon. But how do the photographers manage to capture these events? Hint: it’s not random luck.

“I live under a main flight path out of Heathrow,” said photographer Chris Lyons from the UK who took the image above earlier today, “and can easily spot the planes not long after they take off — if it is clear — from when they are about 100 miles away!”


Chris posts many of his images on Universe Today’s Flickr page, and what is great about Chris’ airplane photos is that he includes a handy infographic about the plane in the shot; the type of plane, its takeoff and destination, and more, garnered from online flight trackers.

Chris told Universe Today that he originally started trying to catch planes passing in front of the Moon.

A waxing gibbous Moon with an American Airlines flyby on Feb. 2, 2015. Credit and copyright: Chris Lyons.

A waxing gibbous Moon with an American Airlines flyby on Feb. 2, 2015. Credit and copyright: Chris Lyons.
“It went from snapping them near it when just taking Moon shots to wanting to get closer and have them actually passing it,” he said. “Then I got a Solar filter and tried it with the Sun. It is far more difficult than the Moon, as you cannot look at it for long. I limit my viewing (our eyes are precious) and only look through high rated neutral density filters.”

We’ve also featured images from Sebastien Lebrigand who lives about 70 km outside of Paris, France. Lebrigand is prolific: he takes almost daily images of planes passing in front of the Sun and Moon and posts them on Twitter.

A Boeing 777 and a sunspot crosses the Sun on April 17, 2014, as seen from France. Credit and copyright: Sebastien Lebrigand.


A Boeing 777 and a sunspot crosses the Sun on April 17, 2014, as seen from France. Credit and copyright: Sebastien Lebrigand.
Lebrigand is an amateur astronomer but says he especially enjoys “the rare conjunction of the planes passing by the Sun and the Moon.’

He uses a Canon EOS 60D and a telescope to take his photos the pictures. But his work takes hours of time for analyzing when a potential photo opportunity might occur, setting up equipment, waiting for the exact moment, and then perfecting the images.

An Airbus A319 jet flying at 37,800 feet as it passes in front of the Moon, as seen from near Paris, France. Credit and copyright: Sebastien Lebrigand.


An Airbus A319 jet flying at 37,800 feet as it passes in front of the Moon, as seen from near Paris, France. Credit and copyright: Sebastien Lebrigand.
Check out more of Chris Lyons’ work at his Flickr page, and you can see more of Sebastien Lebrigand’s work at his website or his Twitter feed.

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Which Planets Have Rings?

Which Planets Have Rings?:

Which Planets Have Rings?


This colorized image taken by the Cassini orbiter, shows Saturn’s A and F rings, the small moon Epimetheus and Titan, the planet’s largest moon.
Credit: NASA/JPL/Space Science Institute
Planetary rings are an interesting phenomena. The mere mention of these two words tends to conjure up images of Saturn, with its large and colorful system of rings that form an orbiting disk. But in fact, several other planets in our Solar System have rings. It’s just that, unlike Saturn, their systems are less visible, and perhaps less beautiful to behold.

The planets of Jupiter, Saturn, Uranus and Neptune all have ring systems  – all of the gas giants in our Solar System. And that’s not all! In fact, ring systems may be more common than previously thought…

In was not until 1979 that the rings of Jupiter were discovered when the Voyager 1 space probe conducted a flyby of the planet. They were also thoroughly investigated in the 1990s by the Galileo orbiter.

Because it is composed mainly of dust, the ring system is faint and can only be observed by the most powerful telescopes, or up-close by orbital spacecraft. However, during the past twenty-three years, it has been observed from Earth numerous times, as well as by the Hubble Space Telescope.

A schema of Jupiter's ring system showing the four main components. For simplicity, Metis and Adrastea are depicted as sharing their orbit. Credit: NASA/JPL/Cornell University


A schema of Jupiter’s ring system showing the four main components. Credit: NASA/JPL/Cornell University
The ring system has four main components: a thick inner torus of particles known as the “halo ring”; a relatively bright, but extremely thin “main ring”; and two wide, thick, and faint outer “gossamer rings”. These outer rings are composed of material from the moons Amalthea and Thebe and are named after these moons (i.e. the “Amalthea Ring” and “Thebe Ring”).

The main and halo rings consist of dust ejected from the moons Metis, Adrastea, and other unobserved parent bodies as the result of high-velocity impacts. Scientists believe that a ring could even exist around the moon of Himalia’s orbit, which could have been created when another small moon crashed into it and caused material to be ejected from the surface.

The rings of Saturn, meanwhile, have been known for centuries. Although Galileo Galilei became the first person to observe the rings of Saturn in 1610, he did not have a powerful enough telescope to discern their true nature. It was not until 1655 that Christiaan Huygens, the Dutch mathematician and scientist, became the first person to describe them as a disk surrounding the planet.

Subsequent observations, which included spectroscopic studies by the late 19th century, confirmed that they are composed of smaller rings, each one made up of tiny particles orbiting Saturn. These particles range in size from micrometers to meters that form clumps orbiting the planet, and which are composed almost entirely of water ice contaminated with dust and chemicals.

Saturn and its rings, as seen from above the planet by the Cassini spacecraft. Credit: NASA/JPL/Space Science Institute. Assembled by Gordan Ugarkovic.


Saturn and its rings, as seen from above the planet by the Cassini spacecraft. Credit: NASA/JPL/Space Science Institute/Gordan Ugarkovic
In total, Saturn has a system of 12 rings with 2 divisions. It has the most extensive ring system of any planet in our solar system. The rings have numerous gaps where particle density drops sharply. In some cases, this due to Saturn’s Moons being embedded within them, which causes destabilizing orbital resonances to occur.

However, within the Titan Ringlet and the G Ring, orbital resonance with Saturn’s moons has a stabilizing influence. Well beyond the main rings is the Phoebe ring, which is tilted at an angle of 27 degrees to the other rings and, like Phoebe, orbits in retrograde fashion.

The rings of Uranus are thought to be relatively young, at not more than 600 million years old. They are believed to have originated from the collisional fragmentation of a number of moons that once existed around the planet. After colliding, the moons probably broke up into numerous particles, which survived as narrow and optically dense rings only in strictly confined zones of maximum stability.

Uranus has 13 rings that have been observed so far. They are all very faint, the majority being opaque and only a few kilometers wide. The ring system consists mostly of large bodies 0.2 to 20 m in diameter. A few rings are optically thin and are made of small dust particles which makes them difficult to observe using Earth-based telescopes.

The labeled ring arcs of Neptune as seen in newly processed data. The image spans 26 exposures combined into a equivalent 95 minute exposure, and the ring trace and an image of the occulted planet Neptune is added for reference. (Credit: M. Showalter/SETI Institute).


The labeled ring arcs of Neptune as seen in newly processed data. Credit: M. Showalter/SETI Institute
The rings of Neptune were not discovered until 1989 until the Voyager 2 space probe conducted a flyby of the planet. Six rings have been observed in the system, which are best described as faint and tenuous. The rings are very dark, and are likely composed by organic compounds processed by radiation, similar to that found in the rings of Uranus. Much like Uranus, and Saturn, four of Neptune’s moons orbit within the ring system.

In addition, the minor planet of Chariklo – an asteroid that orbits the Sun between Saturn and Uranus – also has two rings that orbit it. These are perhaps due to a collision that caused a chain of debris to form in orbit around it. The announcement of these rings was made on March 26th of 2014, and was based on observations made during a stellar occultation on June 3rd, 2013.

Back in 2008, it was suggested that the magnetic effects around the Saturnian moon of Rhea may indicate that it has its own ring system. However, a subsequent study indicated that observations obtained the Cassini mission suggested that some other mechanism was responsible for the magnetic effects.

Pluto is not known to have any ring systems, but some astronomers think that the New Horizons probe might find a ring system when it visits in 2015.

In short, four planets in our Solar System have intricate ring systems, as well as the minor planet Chariklo and possibly even Pluto. In this sense, ring systems appear to be a lot more common in our Solar System than previously thought.

We have written many articles about planets with rings for Universe Today. Here’s an article about the composition of Saturn’s rings, and here’s an article about the planets with rings.

If you’d like more info on the planets, check out NASA’s Solar System exploration page, and here’s a link to NASA’s Solar System Simulator.

We’ve also recorded a series of episodes of Astronomy Cast about every planet in the Solar System. Start here, Episode 49: Mercury.



About 

Author, freelance writer, educator, Taekwon-Do instructor, and loving hubby, son and Island boy!

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Thursday, February 5, 2015

What Is A Wolf-Rayet Star?

What Is A Wolf-Rayet Star?:

M1-67 is the youngest wind-nebula around a Wolf-Rayet star, called WR124, in our Galaxy. Credit: ESO


M1-67 is the youngest wind-nebula around a Wolf-Rayet star, called WR124, in our Galaxy. Credit: ESO
Wolf-Rayet stars represent a final burst of activity before a huge star begins to die. These stars, which are at least 20 times more massive than the Sun, “live fast and die hard”, according to NASA.

Their endstate is more famous; it’s when they explode as supernova and seed the universe with cosmic elements that they get the most attention. But looking at how the star gets to that explosive stage is also important.

When you look at a star like the Sun, what you are seeing is a delicate equilibrium of the star’s gravity pulling stuff in, and nuclear fusion inside pushing pressure out. When the forces are about equal, you get a stable mass of fusing elements. For planets like ours lucky enough to live near a stable star, this period can go on for billions upon billions of years.

Being near a massive star is like playing with fire, however. They grow up quickly and thus die earlier in their lives than the Sun. And in the case of a Wolf-Rayet star, it’s run out of lighter elements to fuse inside its core. The Sun is happily churning hydrogen into helium, but Wolf-Rayets are ploughing through elements such as oxygen to try to keep equilibrium.

The core of a red or blue supergiant moments before exploding as a supernova looks like an onion with multiple elements "burning" through the fusion process to create the heat to stay the force of gravity. Fusion stops at iron. With no energy pouring from the central core to keep the other elements cooking, the star collapses and the rebounding shock wave tears it apart. Credit: Wikimedia


The core of a red or blue supergiant moments before exploding as a supernova looks like an onion with multiple elements “burning” through the fusion process to create the heat to stay the force of gravity. Fusion stops at iron. With no energy pouring from the central core to keep the other elements cooking, the star collapses and the rebounding shock wave tears it apart. Credit: Wikimedia
Because these elements have more atoms per unit, this creates more energy — specifically, heat and radiation, NASA says. The star begins to blow out winds reaching 2.2 million to 5.4 million miles per hour (3.6 million to 9 million kilometers per hour). Over time, the winds strip away the outer layers of the Wolf-Rayet. This eliminates much of its mass, while at the same time freeing its elements to be used elsewhere in the Universe.

Eventually, the star runs out of elements to fuse (the process can go no further than iron). When the fusion stops, the pressure inside the star ceases and there’s nothing to stop gravity from pushing in. Big stars explode as supernova. Bigger ones see their gravity warped so much that not even light can escape, creating a black hole.

We still have a lot to learn about stellar evolution, but a few studies over the years have provided insights. In 2004, for example, NASA issued reassuring news saying these stars don’t “die alone.” Most of them have a stellar companion, according to Hubble Space Telescope observations.

A composite image with Chandra data (purple) showing a "point-like source" beside the remains of a supernova, suggesting a companion star may have survived the explosion. Hydrogen is shown in optical light (yellow and cyan) from the Magellanic Cloud Emission Line Survey and there is also optical data available from the Digitized Sky Survey (white). Credit: X-ray: NASA/CXC/SAO/F.Seward et al; Optical: NOAO/CTIO/MCELS, DSS


A composite image with Chandra data (purple) showing a “point-like source” beside the remains of a supernova, suggesting a companion star may have survived the explosion. Hydrogen is shown in optical light (yellow and cyan) from the Magellanic Cloud Emission Line Survey and there is also optical data available from the Digitized Sky Survey (white). Credit: X-ray: NASA/CXC/SAO/F.Seward et al; Optical: NOAO/CTIO/MCELS, DSS
While at first glance this appears as just a simple observation, cosmologists said that it could help us figure out how these stars get so big and bright. For example: Maybe the bigger star (the one that turns into a Wolf-Rayet) feeds off its companion over time, gathering mass until it becomes stupendously big. With more fuel, the big stars burn out faster. Other things the smaller star could influence could be the bigger star’s rotation or orbit.

Here’s a few other facts about Wolf-Rayets, courtesy of astronomer David Darling:

  • Their names come from two French astronomers, Charles Wolf and Georges Rayet, who discovered the first known star of this kind in 1867.
  • Wolf-Rayets come in two flavours: WN (emission lines of helium and nitrogen) and WC (carbon, oxygen and hydrogen).
  • Stars like our Sun evolve into more massive red giants as they run out of hydrogen to burn in the core. When these stars begin to shed their outer layers, they behave somewhat similarly to Wolf-Rayets. So they’re called “Wolf-Rayet type stars”, although they’re not exactly the same thing.
We have written many articles about stars here on Universe Today. Here’s an article about a binary pair of Wolf-Rayet stars, and the good news that WR 104 won’t kill us all. We have recorded several episodes of Astronomy Cast about stars. Here are two that you might find helpful: Episode 12: Where Do Baby Stars Come From, and Episode 13: Where Do Stars Go When they Die?



About 

Elizabeth Howell is the senior writer at Universe Today. She also works for Space.com, Space Exploration Network, the NASA Lunar Science Institute, NASA Astrobiology Magazine and LiveScience, among others. Career highlights include watching three shuttle launches, and going on a two-week simulated Mars expedition in rural Utah. You can follow her on Twitter @howellspace or contact her at her website.

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Wednesday, February 4, 2015

FULL HD BLUE SPACE PLANETS STARS EARTH WALLPAPER

FULL HD BLUE SPACE PLANETS STARS EARTH WALLPAPER
FULL HD BLUE SPACE PLANETS STARS EARTH WALLPAPER
 
FULL HD BLUE SPACE PLANETS STARS EARTH WALLPAPER
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Tuesday, February 3, 2015

Asteroids: 10 Interesting Facts About These Space Rocks

Asteroids: 10 Interesting Facts About These Space Rocks:

Artist's conception of asteroids and a gas giant planet. Credit: Harvard-Smithsonian Center for Astrophysics


Artist’s conception of asteroids and a gas giant planet. Credit: Harvard-Smithsonian Center for Astrophysics
At first glance, looking at a bunch of space rocks doesn’t sound that exciting. Like, aren’t they just a bunch of rubble? What use can they be in understanding the Solar System compared to looking at planets or moons?

Turns out that asteroids are key to figuring out how the Solar System came to be, and that they’re more interesting than they appear at first glance. Below, we have 10 facts about asteroids that will make you reconsider that biased first impression.

Asteroids are leftovers of the early Solar System.

The leading theory about how our neighborhood came to be is this: the Sun coalesced from a compressed grouping of gas that eventually began fusing atoms and creating a protostar. Meanwhile, the dust and debris nearby the Sun began to coalesce. Small grains became small rocks, which crashed into each other to form bigger ones. The survivors of this chaotic period are the planets and the moons that we see today … as well as a few smaller bodies. By studying asteroids, for example, we get a sense of what the Solar System used to look like billions of years ago.

This image shows the Themis Main Belt which sits between Mars and Jupiter. Asteroid 24 Themis, one of the largest Main Belt asteroids, was examined by University of Tennessee scientist, Josh Emery, who found water ice and organic material on the asteroid's surface. His findings were published in the April 2010 issue of Nature. Credit: Josh Emery/University of Tennessee, Knoxville


This image shows the Themis Main Belt which sits between Mars and Jupiter. Asteroid 24 Themis, one of the largest Main Belt asteroids, was examined by University of Tennessee scientist, Josh Emery, who found water ice and organic material on the asteroid’s surface. His findings were published in the April 2010 issue of Nature. Credit: Josh Emery/University of Tennessee, Knoxville
Most asteroids are in a “belt”.

While there are asteroids all over the Solar System, there’s a huge collection of them between the orbits of Mars and Jupiter. Some astronomers think that could have formed into a planet if Jupiter was not nearby. By the way, this “belt” may erroneously create the impression that it is chock full of asteroids and require some fancy Millennium Falcon-style maneuvering, but in reality there are usually hundreds or thousands of miles in between individual asteroids. This shows the Solar System is a big place.

Asteroids are made of different things.

In general, an asteroid’s composition is determined by how close it is to the Sun. Our nearby star’s pressure and heat tends to melt ice that is close by and to blow out elements that are lighter. There are many kinds of asteroids, but these are the three main types, according to NASA:

  • Dark C (carbonaceous) asteroids, which make up most asteroids and are in the outer belt. They’re believed to be close to the Sun’s composition, with little hydrogen or helium or other “volatile” elements.
  • Bright S (silicaceous) asteroids and are in the inner belt. They tend to be metallic iron with some silicates of iron and magnesium.
  • Bright M (metallic) asteroids. They sit in the middle of the asteroid belt and are mostly made up of metallic iron.
Illustration of small asteroids passing near Earth. Credit: ESA / P. Carril


Illustration of small asteroids passing near Earth. Credit: ESA / P. Carril
Asteroids also lurk near planets.

NASA also has classifications for this asteroid type. Trojans stay in the same orbit as a planet, but they “hover” in a special spot known as a Lagrangian point that balances the pull of the planet’s gravity and the pull of the Sun. Trojans near Mars, Jupiter and Neptune have been discovered — as well as at least one near Earth in 2011. We also have near-Earth asteroids, which cross our orbit and could (statistically speaking) one day pose a threat to our planet. That said, no one has yet identified any one asteroid that will one day collide with our planet for sure.

Asteroids have moons.

While we think of moons as something that orbits a planet, asteroids also have smaller bodies that orbit them! The first known one was Dactyl, which was discovered in 1993 to be orbiting a larger asteroid called Ida. More than 150 asteroids are known to have moons, with more being discovered periodically. A more recent example is one discovered orbiting Asteroid 2004 BL86, which passed 750,000 miles (1.2 million kilometers) from Earth in early 2015.

Another set of images of 2004 BL86 and its moon. Credit: NAIC Observatory / Arecibo Observatory


Another set of images of 2004 BL86 and its moon. Credit: NAIC Observatory / Arecibo Observatory
We have flown by, orbited and even landed on asteroids. NASA says there are more than 10 spacecraft that accomplished at least one of these, so we’ll just cover a couple of examples here. NEAR Shoemaker touched down and survived for weeks on 433 Eros in 2001 despite not being designed to do it. NASA’s Dawn spacecraft spent months orbiting Vesta — the second-largest member of the asteroid belt — in 2011 and 2012. And in 2010, Japan’s Hayabusa spacecraft made an astonishing return to Earth bearing samples of asteroid Itokawa that it nabbed in 2005.

Asteroids are too small to support life as we know it. That’s because they’re too tiny to even hold on to atmospheres. Their gravity is too weak to pull their shape into a circle, so they’re irregularly shaped. To get a sense of just how small they are in aggregate, NASA says the mass of all the asteroids in the Solar System is less than our Moon — which only has a tenuous “exosphere” itself.

Impactors strike during the reign of the dinosaurs (image credit: MasPix/devianart)


Impactors strike during the reign of the dinosaurs (image credit: MasPix/devianart)
Despite their small size, water may flow on asteroid surfaces. Observations of Vesta released in 2015 show gullies that may have been carved by water. The theory is that when a smaller asteroid slams into a bigger one, the small asteroid releases a layer of ice in the bigger asteroid it hit. The force of the impact briefly turned the ice into water, which streaked across the surface. (As for how the ice got there in the first place, it’s possible that comets deposited it in some way — but that’s still being investigated as well.)

An asteroid could have killed the dinosaurs. The fossil record for dinosaurs and other creatures of their era show them rapidly disappearing around 65 million or 66 million years ago. According to National Geographic, there are two hypotheses for this event: an asteroid or comet hitting the Earth, or a huge volcano eruption. The case for an asteroid comes from a layer of iridium (a rare element on Earth, but not in meteorites) that is found all over the world, and a crater called Chicxulub in Mexico’s Yucatan Peninsula that is about 65 million years old. Iridium, however, is also found inside the Earth, which lends credence to some theories that it was volcanoes instead. In either case, the resulting debris blocked the Sun and eventually starved those survivors of the impact.

At least one asteroid has rings. Called Chariklo, scientists made the surprise discovery in 2013 when they watched it pass in front of a star. The asteroid made the background star “blink” a few times, which led to the discovery that two rings are surrounding the asteroid.



About 

Elizabeth Howell is the senior writer at Universe Today. She also works for Space.com, Space Exploration Network, the NASA Lunar Science Institute, NASA Astrobiology Magazine and LiveScience, among others. Career highlights include watching three shuttle launches, and going on a two-week simulated Mars expedition in rural Utah. You can follow her on Twitter @howellspace or contact her at her website.

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Posted by Nelio Inacio at 2:29 PM 0 comments

The Solar System’s ‘Yearbook’ is About to Get Filled In

The Solar System’s ‘Yearbook’ is About to Get Filled In:

The 33 largest objects in our Solar System, ordered by mean radius, using the best images available as of January, 2015. Credit and copyright: Radu Stoicescu.


The 33 largest objects in our Solar System, ordered by mean radius, using the best images available as of January, 2015. Credit and copyright: Radu Stoicescu.
Lined up like familiar faces in your high school yearbook, here are images of the 33 largest objects in the Solar System, ordered in size by mean radius. Engineer Radu Stoicescu put this great graphic together, using the highest resolution images available for each body. Nine of these objects have not yet been visited by a spacecraft. Later this year, we’ll visit three of them and be able to add better images of Ceres, Pluto and Charon. It might be a while until the remaining six get closeups.

“This summer, for the first time since 1989,” Stoicescu noted on reddit, “we will add 3 high resolution pictures to this collection, then, for the rest of our lives, we are not going to see anything larger than 400 km in high definition for the first time. It is sad and exciting at the same time.”


Dawn will enter orbit at Ceres approximately March 6, 2015, four months before New Horizons flies past Pluto and Charon.

But a comprehensive Solar System yearbook might never be completed. Not only will there likely be new dwarf planets discovered in the Kuiper Belt, uUnless things change in the budgetary and planetary missions departments for any of the world’s space agencies, the remaining six unvisited objects in the graphic above will likely remain as “fuzzy dots” for the rest of our lives.

If you like the graphic above, you can see more imagery and space discussions at Stoicescu’s reddit page.

For more Solar System yearbook-like imagery, Emily Lakdawalla has also created some wonderful graphics/montages of our Solar System, like this one:

Every round object in the solar system under 10,000 kilometers in diameter, to scale. Montage by Emily Lakdawalla. Data from NASA / JPL and SSI, processed by Gordan Ugarkovic, Ted Stryk, Bjorn Jonsson, and Emily Lakdawalla.


Every round object in the solar system under 10,000 kilometers in diameter, to scale. Montage by Emily Lakdawalla. Data from NASA / JPL and SSI, processed by Gordan Ugarkovic, Ted Stryk, Bjorn Jonsson, and Emily Lakdawalla.
As Emily wrote in the accompanying blog post, “Just look at all of these worlds, and think about how much of the solar system we have yet to explore. Think about how much we have to learn by orbiting, and maybe even landing on, those planet-sized moons. Think about how Pluto isn’t the end of the planets, it’s the start of a whole new part of the solar system that we’ve never seen before, and how seeing Charon is going to clue us in to what’s happening on a dozen other similar-sized, unvisitably far worlds.”

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Posted by Nelio Inacio at 2:28 PM 0 comments

How We’ve ‘Morphed’ From “Starry Night” to Planck’s View of the BICEP2 Field

How We’ve ‘Morphed’ From “Starry Night” to Planck’s View of the BICEP2 Field:



Vincent Van Gogh’s Starry Night is a finished work of art known to billions. After 13.8 billion years, the Universe remains an unfinished work. Planck Observatory data revealing the Milky Way’s magnetic field is morphed into a Starry Night of June 1889. (Credits: Vincent Van Gogh, ESA, Illustration – J.Schmidt, T.Reyes)
From the vantage point of a window in an insane asylum, Vincent van Gogh painted one of the most noted and valued artistic works in human history. It was the summer of 1889. With his post-impressionist paint strokes, Starry Night depicts a night sky before sunrise that undulates, flows and is never settled. Scientific discoveries are revealing a Cosmos with such characteristics.

Since Vincent’s time, artists and scientists have taken their respective paths to convey and understand the natural world. The latest released images taken by the European Planck Space Telescope reveals new exquisite details of our Universe that begin to touch upon the paint strokes of the great master and at the same time looks back nearly to the beginning of time. Since Van Gogh – the passage of 125 years – scientists have constructed a progressively intricate and incredible description of the Universe.

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Read the rest of How We’ve ‘Morphed’ From “Starry Night” to Planck’s View of the BICEP2 Field (1,408 words)

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Posted by Nelio Inacio at 2:27 PM 0 comments

What Was The Impact That Killed The Dinosaurs?

What Was The Impact That Killed The Dinosaurs?:

Artist's conception of an asteroid crashing into the Yucatan Peninsula about 65 million years ago. Credit: Donald E. Davis/NASA


Artist’s conception of an asteroid crashing into the Yucatan Peninsula about 65 million years ago. Credit: Donald E. Davis/NASA
What suddenly made the dinosaurs disappear 65 million or 66 million years ago? Whatever it was, all indications show that it was a massive extinction event. The fossil record not only shows dinosaurs disappearing, but also numerous other species of the era. Whatever it was, there was a sudden change in the environment that changed evolution forever.

The leading theory for this change is a small body (likely an asteroid or a comet) that slammed into Mexico’s Yucatan Peninsula. The impact’s force generated enough debris to block the Sun worldwide, killing any survivors of starvation.

The crater

There have been numerous theories proposed for the dinosaurs’ death, but in 1980 more evidence arose for a huge impact on the Earth. This happened when a father-son University of California, Berkeley research team — Luis Alvarez and Walter Alvarez — discovered a link with a 110-mile (177-kilometer) wide impact crater near the Yucatan coast of Mexico. It’s now known as Chicxulub.

Chicxulub crater in Mexico. Credit: Wikipedia/NASA


Chicxulub crater in Mexico. Credit: Wikipedia/NASA
It sounds surprising that such a huge crater wasn’t found until that late, especially given satellites had been doing Earth observation for the better part of 20 years at that point. But as NASA explains, “Chicxulub … eluded detection for decades because it was hidden (and at the same time preserved) beneath a kilometer of younger rocks and sediments.”

The data came from a Mexican company that was seeking oil in the region. The geologists saw the structure and guessed, from its circular shape, that it was an impact crater. Further observations were done using magnetic and gravity data, NASA said, as well as space observations (including at least one shuttle mission).

The layer

The asteroid’s impact on Earth was quite catastrophic. Estimated at six miles (9.7 kilometers) wide, it carved out a substantial amount of debris that spread quickly around the Earth, aided by winds in the atmosphere.

What Killed The Dinosaurs


K-T Boundary. Image Credit: NASA Earth Observatory
If you look in the fossil record all over the world, you will see a layer that is known as the “K-T Boundary”, referring to the boundary between the Cretaceous and Tertiary periods in geologic history. This layer, says the University of California, Berkeley, is made up of “glassy spheres or tektites, shocked quartz and a layer of iridium-enriched dust.”

Of note, iridium is a rare element on the surface of the Earth, but it’s fairly common in meteorites. (Some argue that the iridium could have come from volcanic eruptions churning it up from inside the Earth; for more information, see this Universe Today story.)

Was it simply ‘the last straw’?

While an asteroid (or comet) striking the Earth could certainly cause all the catastrophic events listed above, some scientists believe the dinosaurs were already on their last legs (so to speak) before the impact took place. Berkeley points to “dramatic climate variation” in the million years preceding the event, such as very cold periods in the tropical environment that the dinosaurs were used to.

Impactors strike during the reign of the dinosaurs (image credit: MasPix/devianart)


Impactors strike during the reign of the dinosaurs (image credit: MasPix/devianart)
What might have caused this were several volcanic eruptions in India around the same time. Some scientists believe it was the volcanic eruptions themselves that caused the extinction and that the impact was not principally to blame, since the eruptions could also have produced the iridium layer. But Berkeley’s Paul Renne said the eruptions were more a catalyst for weakening the dinosaurs.

“These precursory phenomena made the global ecosystem much more sensitive to even relatively small triggers, so that what otherwise might have been a fairly minor effect shifted the ecosystem into a new state,” Renne stated in 2013. “The impact was the coup de grace.”

Here on Universe Today there are several articles on the asteroids and the Chicxulub Crater. Astronomy Cast has an episode on asteroids as bad neighbors.



About 

Elizabeth Howell is the senior writer at Universe Today. She also works for Space.com, Space Exploration Network, the NASA Lunar Science Institute, NASA Astrobiology Magazine and LiveScience, among others. Career highlights include watching three shuttle launches, and going on a two-week simulated Mars expedition in rural Utah. You can follow her on Twitter @howellspace or contact her at her website.

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Posted by Nelio Inacio at 2:26 PM 0 comments

Jupiter and the Full Snow Moon Come Together In a Beautiful Conjunction Tonight

Jupiter and the Full Snow Moon Come Together In a Beautiful Conjunction Tonight:

A halo rings the bright moon and planet Jupiter (left of moon) last night Feb. 2. Ice crystals in high clouds like cirrostratus refract moonlight into a circle of light. Tonight the Full Snow Moon will shine just 4.5° from the planet. Credit: Bob King


A halo rings the bright moon and planet Jupiter (left of moon) last night Feb. 2. Ice crystals in high clouds like cirrostratus refract moonlight into a circle of light. Tonight the Full Snow Moon will shine just 4.5° from the planet. Credit: Bob King
The Full Moon celebrates Jupiter’s coming opposition by accompanying the bright planet in a beautiful conjunction tonight.

Even last night Jupiter and the Moon were close enough to attract attention. Tonight they’ll be even more striking. Two reasons for that. The Moon is full this evening and will have crept within 41/2° of the planet. They’ll rise together and roll together all night long.

The Full Snow Moon will share the sky with Jupiter in Cancer tonight not far from the Sickle or head of Leo the Lion. The map shows the scene around 8 o'clock local time. Source: Stellarium


The Full Snow Moon will share the sky with Jupiter in Cancer tonight not far from the Sickle or head of Leo the Lion. The map shows the scene around 8 o’clock local time. Source: Stellarium
February’s full moon is aptly named the Full Snow Moon as snowfall can be heavy this month. Just ask the folks in Chicago. The Cherokee Indians called it the “Bone Moon”, named for the tough times experienced by many Native Americans in mid-winter when food supplies ran low. With little left to eat people made use of everything including bones and bone marrow for soup.

Not only is the Full Moon directly opposite the Sun in the sky, rising around sunset and setting around sunrise, but in mid-winter they’re nearly on opposite ends of the celestial seesaw.

Jupiter, like tonight's Full Moon, will be directly opposite the Sun this Friday and in "full moon" phase. Credit: Bob King


Jupiter, like tonight’s Full Moon, will be directly opposite the Sun this Friday and in “full moon” phase. Because both planets are lined up on the same side of the Sun, Jupiter will also be at its closest to us for the year. Credit: Bob King
In early February the Sun is still near its lowest point in the sky (bottom of the seesaw) for the northern half of  the globe. And while daylight is steadily increasing as the Sun moves northward, darkness still has the upper hand this month. Full Moons like tonight’s lie 180° opposite the Sun, placing the Moon near the top of the seesaw. Come early August, the Sun will occupy the Moon’s spot and the Full Moon will have slid down to the Sun’s current position. Yin and Yang folks.

Now here’s the interesting thing. Jupiter will also be in “full moon” phase when it reaches opposition this Friday Feb. 6.  Take a look at the diagram. From our perspective on Earth, Jupiter and the Sun lie on opposite sides of our planet 180° apart. As the Sun sets Friday, Jupiter will rise in the east and remain visible all night until setting around sunrise exactly like a Full Moon.

So in a funny way, we have two Full Moons this week only one’s a planet.

Like me, a lot of you enjoy a good moonrise. That golden-orange globe, the crazy squished appearance at rising and the transition to the bright, white, beaming disk that throws enough light on a winter night to ski in the forest without a headlamp. All good reasons to be alive.

If Jupiter were moved to the Moon's distance it would span about 20 of sky or 40x the apparent diameter of the Full Moon. Credit: Roscosmos with additions by the author


If Jupiter were moved to the Moon’s distance it would span about 20 degrees or 40 times the apparent diameter of the Full Moon. Credit: Roscosmos with additions by the author
To find when the moon rises for your town, click over to this moonrise calculator. As you step outside tonight to get your required Moon and Jupiter-shine, consider the scene if we took neighboring Jupiter and placed it at the same distance as the Moon. A recent series of such scenes was released by the Russian Federal Space Agency (Roscosmos). I included one here and added the Moon for you to compare. Is Jupiter enormous or what?



About 

I'm a long-time amateur astronomer and member of the American Association of Variable Star Observers (AAVSO). My observing passions include everything from auroras to Z Cam stars. Every day the universe offers up something both beautiful and thought-provoking. I also write a daily astronomy blog called Astro Bob.

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Posted by Nelio Inacio at 2:24 PM 0 comments

Gravitational Waves from Early Universe Remain Elusive

Gravitational Waves from Early Universe Remain Elusive:


Color scale image from Planck



A joint analysis of data from Planck and the ground-based experiment BICEP2 has found no conclusive evidence of gravitational waves from the birth of our universe.






Posted by Nelio Inacio at 2:23 PM 0 comments
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