Posted on by Fraser Cain

The Eye of God

Helix Nebula

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There was an email going around a few years ago talking about “the Eye of God”. This photo was actually an image of the Helix Nebula taken by the Hubble Space Telescope.

The Eye of God nebula is a bright planetary nebula located about 700 light-years away in the constellation Aquarius; it’s also known as NGC 7293. In fact, the Helix Nebula is probably the closest planetary nebula we can see in the sky, and it shows the future that stars like our Sun go through when they run out of fuel and puff out their outer layers.

It’s thought that the Helix Nebula is actually cylindrical shaped. From our perspective, we’re looking down the cylinder to see the central star. Astronomers estimate that the Helix Nebula is about 10,600 years old, based on the rate of expansion of the nebula.

With the power of the Hubble Space Telescope, astronomers were able to see knots of material in the nebula. They’ve now discovered more than 20,000 of these cometary knots in the nebula. These knots have cometary tails, and it’s been discovered that they can collide with one another.

Here’s the email you might get:

Subject: Fw: Eye of God
This is a picture taken by NASA with the Hubble telescope. They are referring to it as the “Eye of God”. I thought it was beautiful and worth sharing.

Some emails even say that this is a rare event that only happens once every 3,000 years. The reality is that this is just a beautiful photograph taken by the Hubble Space Telescope. There are other images that have been taken by other telescopes and they look beautiful as well.

We’ve written several articles about the Helix Nebula for Universe Today. Here’s an article about a new view into the Helix Nebula, and here’s an article about comets colliding inside the Helix Nebula.

If you’d like more info on the Helix Nebula, here’s a nice picture from the La Silla Observatory at Astronomy Picture of the Day.

We’ve also recorded an entire episode of Astronomy Cast just about nebulae. Listen here, Episode 111: Nebulae.

Posted on by Fraser Cain

Artificial Satellites

It's getting crowded out there: active and inactive satellites are tracked (Google/Analytical Graphics)

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Artificial satellites are human-built objects orbiting the Earth and other planets in the Solar System. This is different from the natural satellites, or moons, that orbit planets, dwarf planets and even asteroids. Artificial satellites are used to study the Earth, other planets, to help us communicate, and even to observe the distant Universe. Satellites can even have people in them, like the International Space Station and the Space Shuttle.

The first artificial satellite was the Soviet Sputnik 1 mission, launched in 1957. Since then, dozens of countries have launched satellites, with more than 3,000 currently operating spacecraft going around the Earth. There are estimated to be more than 8,000 pieces of space junk; dead satellites or pieces of debris going around the Earth as well.

Satellites are launched into different orbits depending on their mission. One of the most common ones is geosynchronous orbit. This is where a satellite takes 24 hours to orbit the Earth; the same amount of time it takes the Earth to rotate once on its axis. This keeps the satellite in the same spot over the Earth, allowing for communications and television broadcasts.

Another orbit is low-Earth orbit, where a satellite might only be a few hundred kilometers above the planet. This puts the satellite outside the Earth’s atmosphere, but still close enough that it can image the planet’s surface from space or facilitate communications. This is the altitude that the space shuttle flies at, as well as the Hubble Space Telescope.

Artificial satellites can have a range of missions, including scientific research, weather observation, military support, navigation, Earth imaging, and communications. Some satellites fulfill a single purpose, while others are designed to perform several functions at the same time. Equipment on a satellite is hardened to survive in the radiation and vacuum of space.

Satellites are built by various aerospace companies, like Boeing or Lockheed, and then delivered to a launch facility, such as Cape Canaveral. Launch facilities are located as close as possible to the Earth’s equator, to give an extra velocity kick into space. This allows rockets to use less fuel or launch heavier payloads.

The altitude of a satellite’s orbit defines how long it will stay in orbit. Low orbiting satellites are mostly above the Earth’s atmosphere, but they’re still buffeted by the atmosphere and their orbit eventually decays and they crash back into the atmosphere. Other satellites orbiting in high orbits will likely be there for millions of years.

We’ve written many articles about artificial satellites for Universe Today. Here’s an article about geosynchronous orbit, and here’s an article about orbital speed.

You can get more information about satellites from NASA. Here’s a cool realtime satellite tracking system, and here’s Hubblesite.

We’ve also recorded several episodes of Astronomy Cast about satellites. Here’s a good one, Episode 82: Space Junk.

Source: NASA

Posted on by Nancy Atkinson

Get the Big Picture of the Milky Way at the Adler Planetarium

Spitzer infrared image on display at the Adler Planetarium. Credit: Adler

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Astronomy is all about getting the big picture of our place in the cosmos, but some pictures are bigger than others. This one is really big. The world’s largest image of our Milky Way galaxy went on display today at the Adler Planetarium in Chicago. The image spans an area of 37 meters (120 feet) long by 1 meter (3 feet) wide at its sides, bulging to 2 meters (6 feet) to show the center of our humongous galaxy. The panorama represents 800,000 separate images taken by the Spitzer Space Telescope over a five-year period.


“This is the highest-resolution, largest, most sensitive infrared picture ever taken of our Milky Way,” said Sean Carey of NASA’s Spitzer Science Center, speaking when the image was unveiled in 2008 at the American Astronomical Society meeting in St. Louis (see our article and image of the unveiling). “Where previous surveys saw a single source of light, we now see a cluster of stars. With this data, we can learn how massive stars form, map galactic spiral arms and make a better estimate of our galaxy’s star-formation rate.”

Spitzer Survey image compiled. Credit: NASA/JPL
Spitzer Survey image compiled. Credit: NASA/JPL

Data from Spitzer’s Infrared Array Camera (IRAC) and the Multiband Imaging Photometer were used to create the image.

If you want to download a very large version of this image (2400 x 3000) click here — warning: very big file.

From our vantage point on Earth, we see the Milky Way as a blurry, narrow band of light that stretches across the sky. In the visible, we only see about 5% of what’s actually out there. But with Spitzer’s dust-piercing infrared eyes, astronomers have peered 60,000 light-years away into this fuzzy band, called the galactic plane, and saw all the way to the other side of the galaxy.

The panorama reveals star formation as never seen before on both the large and small scale. Most of the star forming regions had not been seen before this project was undertaken.

I had the good fortune of seeing the image in St. Louis, and I highly recommend taking the opportunity to go see it at the Adler Planetarium if you are in Chicago. Here’s a video that explains how astronomers took the images and put them all together to form this gigantic panorama.

*Serendipitously, I am currently at the dotAstronomy conference where Eli Bressert from the Chandra X-Ray Center talked about the GLIMPSE Viewer. Here’s the link to see the Spitzer image with GLIMPSE (Galactic Legacy Infrared Midplane Extraordinaire).

Adler Planetarium is located at 1300 South Lake Shore Drive, Chicago, Ill., 60605. Phone: 312-922-7827. Adler Planetarium website. .

Posted on by Fraser Cain

Tenth Planet: The Next World in the Solar System

Tenth planet? Artists concept of the view from Eris with Dysnomia in the background, looking back towards the distant sun. Credit: Robert Hurt (IPAC)
Tenth planet? Artists concept of the view from Eris with Dysnomia in the background, looking back towards the distant sun. Credit: Robert Hurt (IPAC)

Before 1930, there were 8 planets in the Solar System. And then with the discovery of Pluto in 1930, the total number of planets rose to 9. Although astronomers kept searching for more planets, it wasn’t until 2005 that an object larger than Pluto was found orbiting in the distant Solar System. This new object was known as Eris, and many considered it to be a tenth planet; but it actually created a controversy that ended up with Pluto being kicked out of the planet club and becoming a dwarf planet. There really is no 10th planet, in fact, we don’t even have a ninth planet any more.

Discovery of Eris

Eris, originally named 2003 ub 313 was discovered by Palomar observatory researcher Mike Brown; Mike has been behind many of the trans-Neptunian discoveries in the last decade. Mike and his team discovered Eris by systematically scanning the sky for objects moving at the right speed in the right object to be in the outer Solar System.

Further observations of Eris showed that it was actually larger than Pluto by a significant amount; it measured 2,500 km across, compared to Pluto’s 2,300 km diameter. And it orbited at a distance of 67 astronomical units, compared to Pluto’s 39 AU (1 AU is the average distance from the Earth to the Sun).

Tenth Planet, Dwarf Planet

Because there was now a larger object than Pluto found orbiting the Sun, astronomers needed to decide whether this would be come the tenth planet. At a meeting of the International Astronomical Union in 2006, astronomers decided to redefine their classification of a planet. And these new rules excluded Eris. Instead of becoming the tenth planet, Eris became a dwarf planet; the same fate as Pluto.

We’ve written many articles about Eris for Universe Today. Here’s an article about how Eris is changing, and here’s an article about how Xena was renamed to Eris.

If you’d like more info on Eris, check out NASA’s page on Eris.

We’ve also recorded an episode of Astronomy Cast that explains why Pluto isn’t a planet any more. Listen here, Episode 1: Pluto’s Planetary Identity Crisis.

Posted on by Fraser Cain

Life of a Star

Artist’s impression of a baby star still surrounded by a protoplanetary disc in which planets are forming. Credit: ESO

Stars are kind of like people. They’re born, they live their lives, and then they die. Let’s take a look at the life of a star.

All stars start out a giant clouds of neutral hydrogen, which has been left over since the Big Bang. Some event, such as a nearby supernova explosion causes the cloud to collapse inward, and then gravity takes over. As the cloud collapses, it breaks up into different knots of material, each of which will go on to form a star.

As the cloud continues to collapse inward, the conservation of angular momentum from all the particles sets the cloud spinning. As gravity pulls it further inward, it begins spinning faster and faster and flattens out into a disk. The star forms from the concentration of material in the center of the protostellar disk, and the planets form out in the disk.

In the beginning, a star shines because of the heat of compression through gravity. But eventually the core of the star heats up to the point that nuclear fusion reactions can occur. At this point, the star blasts away the remaining dust and gas with its solar winds and enters the main sequence phase of life.

A star like our Sun will continue as a main sequence star for billions of years; slowly converting hydrogen into helium in its core. But it will eventually run out of easily usable hydrogen in its core. When this happens, the star collapses down a little and then starts to convert a shell of hydrogen into helium around the core. This additional heat puffs out the star into a red giant, causing it to become much larger.

A typical star will go through several phases of expansion and contraction as it burns through shells of hydrogen around its core. Larger stars will also switch to helium fusion in the core, and even go up the periodic table of elements, fusing heavier and heavier elements. Eventually they’ll reach the limits of gravity, running out of fuel to burn. The star will then slough off its outer layers, creating the beautiful planetary nebulae we see from Earth.

And then the star will collapse inward, becoming a white dwarf star. This is a highly compressed object that can have the mass of the Sun, but only be as small as the Moon. It’s still hot because of the residual energy it had when it was a true star, but it slowly cools down, eventually becoming a black dwarf; the same temperature as the background of the Universe.

Stars much larger than our own Sun can have a more dramatic finish. The largest stars will detonate as supernovae when they reach the end of their lives. Some will then collapse down to become neutron stars or black holes, while others explode with such energy that the entire star just blows itself apart.

We’ve written many articles about stars for Universe Today. Here’s an article about the death of stars, and here’s an article about the life cycle of stars.

If you’d like more information on stars, check out Hubblesite’s News Releases about Stars, and here’s the stars and galaxies homepage.

We’ve also recorded several episodes of Astronomy Cast about stars. Here’s a good one, Episode 12: Where Do Baby Stars Come From?

Source: NASA

Posted on by Fraser Cain

Retrograde

Neptune's largest Moon, Triton. Astronomers think that Triton is a captured Kuiper Belt Object. Credit: NASA/JPL

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When objects in the Solar System orbit other objects, they can either go in a regular prograde direction, or in a retrograde direction.

Almost all of the orbits in the Solar System are caused by the initial collapse of the Solar System 4.6 billion years ago from the solar nebula. As the cloud of gas and dust collapsed down into the stellar disk, the conservation of angular momentum caused the disk to rotate. The Sun formed out of a bulge in the center of the Solar System, and the planets formed out of lumps in the protoplanetary disk.

And so, all of the planets in the Solar System orbit in a prograde direction. And then the planets themselves also collapsed down, and started rotating because of the conservation of angular momentum. And again, almost all of the planets rotate in a prograde direction; except one: Venus. When seen from above their north pole, all the planets rotate in a counter-clockwise direction. But Venus is actually rotating in a clockwise direction.

It’s believed that most of the moons in the Solar System formed in place around their planets. And so they orbit in a prograde direction as well, orbiting in the same direction that their planet turns. There are a few exceptions; however, like Neptune’s moon Titan, which orbits in a retrograde direction.

Because the Earth and the planets are orbiting the Sun, we get a changing perspective of their position as we go around the Sun. The planets can seem to slow down, stop, and then move backwards in the sky. Of course, they’re not actually going backwards in their orbit, but we’re seeing that from our perspective. When the planets move in this backwards direction, they’re said to be “in retrograde”. And then they start moving forward again and come out of retrograde.

We’ve written a few articles about retrograde orbits for Universe Today. Here’s an article about Mercury in retrograde, the 2009 Mercury retrograde dates, and here’s an article about Venus in retrograde.

If you’d like more information on orbits, check out this cool list of orbit diagrams. And here’s more info on Neptune’s moon Triton, which follows a retrograde orbit.

We’ve also done an episode of Astronomy Cast about Neptune. Listen here, Episode 63: Neptune.

Posted on by Fraser Cain

Supernova

Crab Nebula

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A supernova is the explosion of a star. In an instant, a star with many times the mass of our own Sun can detonate with the energy of a billion suns. And then, within just a few hours or days, it dims down again. Some explode into a spray of gas and dust, while others become exotic objects like neutron stars or black holes.

Astronomers have classified supernovae into two broad classifications: Type I and Type II. Type I supernovae occur in binary systems, where one star pulls off mass from a second star until it reaches a certain amount of mass. This causes it to explode as a supernova. Type II supernovae are the explosions of massive stars which have reached the end of their lives.

All of the elements heavier than iron were created in supernova explosions. As a massive star runs out of hydrogen fuel, it starts to fuse together heavier and heavier elements. Helium into carbon and oxygen. And then oxygen into heavier elements. It goes up the periodic table this way, fusing heavier elements until it reaches iron. Once a star reaches iron, it’s no longer able to extract energy from the fusion process. The core collapses down into a black hole, and the material around it is fused together into the elements heavier than iron. If you’re wearing any gold jewelry, that was created in a supernova.

In 1054 Chinese astronomers saw a supernova explosion that was so bright it was visible in the middle of the day. The explosion of gas and dust is now visible as the Crab Nebula (that’s the picture at the top of this article). The most recent powerful supernova explosion occurred in 1987, when a star exploded in the Large Magellanic Cloud.

Astronomers use Type I supernovae to judge distances in the Universe. This is because they always explode with approximately the same amount of energy. When a white dwarf star collected approximately 1.4 times the mass of the Sun, it can’t support its mass and collapses. This amount is called the Chandrasekhar Limit. When an astronomer sees a Type I supernova, they know how bright it is, and so they can measure how far away it is.

We’ve written many articles about supernovae for Universe Today. Here’s an article about a slow motion supernova, and here’s an article about a theoretical supernova that was actually found to exist.

If you’d like to see a gallery of supernova photographs, check out this section of the Hubble Space Telescope site, and here’s NASA’s Photo Gallery of Nebulae.

We’ve also recorded several episodes of Astronomy Cast about supernovas. Check out this one, Episode 14: We’re All Made of Supernovae.

References:
http://www.cfa.harvard.edu/supernova//newdata/supernovae.html
http://en.wikipedia.org/wiki/Chandrasekhar_limit

Posted on by Nancy Atkinson

Exploring to the Beat of Pulsars

PULSE@Parkes project. Credit: Andrew Crosling

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An innovative project that provides high school students in Australia the opportunity to work with the famous Parkes radio telescope will soon make the data available to schools around the world. The PULSE@Parkes project allows for hands-on remote observing of pulsars producing real-time data, which then becomes part of a growing database used by professional astronomers. “Students can help monitor pulsars and identify unusual ones or detect sudden glitches in their rotation,” said Rob Hollow from the Australia Telescope National Facility, and coordinator for the PULSE@Parkes project. “They can also help determine the distance to existing pulsars.”

Initially, the project was only available to schools in Australia, but PULSE@Parkes hopes to expand globally, allowing students to collaborate on monitoring pulsar data. The first international session will be held on Dec. 7, 2009 at Cardiff University in the UK.

“We had the challenge to develop and implement simulation radio astronomy activities for high school students, providing the opportunity for them to actually use a radio telescope facility and engage with professional scientists,” said Hollow, speaking at the .Astronomy (dot Astronomy) conference this week in Leiden, The Netherlands. “We also wanted to have students doing science that is appropriate for them and useful for professional astronomers.”

Students in Sydney controlling the Parkes radio telescope. Credit: R. Hollow, CSIRO
Students in Sydney controlling the Parkes radio telescope. Credit: R. Hollow, CSIRO

Hollow said that even though radio astronomy data consists of squiggly lines, students are still engaged by the results, even without the pretty pictures produced by other astronomical instruments. “It works surprisingly well, and the visuals haven’t been as big an issue and we thought,” Hollow said. “But in looking at pulsars, the students do get the pulse profiles and they get immediate feedback.”

Plus, when the dish actually moves in response to the students’ inputs, they really become engaged. “There’s a real ‘wow’ factor in being able to control the telescope,” Hollow said. “The students pick it up quickly, and they really like that they are contributing to science.”

Recently, the first science paper was published using results obtained by students.

The program is done remotely, and students view webcams of the telescope and control room. They control the telescope directly via the internet, monitor the data in real time, and use Skype to communicate with astronomers at Parkes.

So far, Hollow said, they have done 25 sessions, with 28 schools, working with about 450 students. “This project is not just for gift and talented students,” he said, “and any school can apply.”

The Parkes Radio Telescope. Credit: R. Hollow, CSIRO
The Parkes Radio Antenna. Credit: R. Hollow, CSIRO

Parkes is a 64 m diameter radio antenna that was built in 1961. Hollow said the dish has received regular updates and is still on the cutting edge of science. Most famously, Parkes was to receive video from the Apollo mission to the Moon.

Hollow said he sees PULSE@Parkes as just the beginning of working with students. The Australian Square Kilometre Array Pathfinder (ASKAP) will be coming online in just a couple of years, with thirty-six 12-meter dishes. “This will provide for very fast surveys that will increase the area of coverage and increase the capability for sensitivity,” Hollow said. “From ASKAP, we’ll be getting massive data sets, which will provide more opportunity for student and public involvement.

For more information, including an audio of what a pulsar “sounds” like, as well as info for schools and teachers, requirements, and how to apply visit the PULSE@Parkes website

Posted on by Nicholos Wethington

Countdown to Christmas: Hubble Advent Calendar

This is way cooler than those chocolate filled advent calendars that you can buy at the grocery store (although arguably less yummy): The Big Picture over at The Boston Globe is doing an advent calendar to count down the days until Christmas, only instead of opening a little door to nuggets of chocolate each day, you get huge chunks of Hubble eye candy!

Each day until Christmas you can feast your eyes on a new image from the Hubble Space Telescope like today’s shown above. Hubble has produced enough images over its lifetime to fill a few thousand advent calendars. If you happened to be worried about your waistline this holiday season, forget buying a calorie-bloated advent calendar and head on over to The Big Picture for the next 24 images, which are sure to be stunning.

Little cycling cap tip to The Bad Astronomer

Posted on by Nicholos Wethington

Mars Odyssey Goes into Safe Mode

An artist's impression of the Odyssey orbiter around Mars. . Image Credit: NASA

The Mars Odyssey orbiter went into safe mode on Saturday, November 28th because of a glitch in the “memory error external bus” of the satellite. Odyssey will remain in safe mode at least until the end of the week, effectively slowing down communication with the two rovers, Spirit and Opportunity.

Odyssey is still operating at normal temperatures and communicating with the control team back on Earth. It stayed in safe mode over the weekend. After a full reboot today, the craft is on the mend and expected to be fully operational later this week.

“This event is a type we have seen before, so we have a known and tested path to resuming normal operations,” said Odyssey Project Manager Philip Varghese of NASA’s Jet Propulsion Laboratory in a press release.

Odyssey has been orbiting Mars since January 2002, mapping the surface and taking global measurements of the planet. Odyssey has also been the link to the Earth for the two rovers since 2004, acting as a communications relay that speeds up the transference of signals between the robots and the control team. Though Spirit and Oppy have their own antennae for communication, Odyssey can communicate with the Earth at 10 times the speed and with a fraction of the energy usage.

This glitch is really nothing new for the satellite – it’s much like having to reboot your laptop when it freezes up. The Mars Reconnaisance Orbiter would be the obvious backup for Odyssey, but the MRO has been in safe mode since August 26th. The MRO rebooted itself four times in 2009, and after the last reboot the spacecraft has stayed in safe mode to prevent any catastrophic damage to its memory.

NASA had planned to uplink files to the MRO to restore it sometime this week, but the uplink and recalibration of the satellite would take over a week, meaning that if Odyssey isn’t back up by the end of the week Spirit and Opportunity are on their own for a little while longer.

Odyssey is a key player in the efforts to free the Spirit rover, which has been stuck in a sand trap since May 1st of this year but is making progress. Because of a wheel stall problem that the control team thinks may be internal, an extrication attempt made on November 28th wasn’t successful. The Spirit control team hadn’t planned on making any more maneuvers to free the rover this week, as they are still analyzing the recent attempts to plan for future efforts at freeing its wheel.

Hopefully, by the end of next week we’ll be seeing two fully-functioning orbiters and a freewheelin’ Spirit.

Source: NASA press release