The Fate of the Universe

 Astronomers can use telescopes to look deep into space, where essentially we are looking back in time, and try to understand how the universe began. We know from observations that the universe is about 14.5 billion years old, and that it's currently expanding due to some Big Bang or moment of Inflation sometime in the past. Based on the current structure of our universe, and the theories behind how it began, astronomers are trying to predict the fate of our universe. What will eventually happen to the universe billions of years from now?  Below are four current theories.

 

 

1. Infinite Expansion: The universe will expand forever. We will survive, but eventually loose contact with places that are too far away and ultimately be isolated in darkness.
2. The Big Rip: The expansion of the universe will continue to increase until it expands so fast that spacetime itself is ripped to shreds. The fate of humanity is unknown.
3. The Big Chill: The universe will expand and continue to cool until it reaches absolute zero. At this temperature, all movement will cease and black holes will evaporate into the vacuum of space. Essentially we will freeze to death.
4. The Big Crunch: gravitational pull from black holes  will cause the expansion of the universe to stop, and the universe will collapse back onto itself. We will not survive, but a new universe may be created in a second big bang after the crunch. 

As time goes by we hope to learn more about the structure of our universe and be able to accurately predict which one of the above (or a completely different scenario) will be true. Sadly, none of these scenarios are "happy endings".  I guess our best hope lies in the bubble universe theory. This says that other universes have budded off of ours and are completely separate and now unbound to ours.  If we are in trouble in the future, maybe we will have the technology to travel to a more stable bubble universe and continue to live there!

Image credit: LSST

Flowing Water On Mars!

The above image was taken back in May by the Mars Reconnaissance Orbiter, a satellite orbiting Mars that takes photos of the Martian surface. First released last Friday, the image depicts dark brown streaks  on the edge of a crater. These streaks appear during the Martian summer, then fade away during the winter months, and reappear again the next summer. It's believed that these streaks are actually flowing  liquid salt water on Mars! That's right, I said flowing liquid water! Over the past decade or so, astronomers have found much evidence that water flowed on Mars sometime in the past, but they believed that conditions on Mars today are too harsh to support liquid water. I guess they were wrong!

The main thing preventing liquid water from flowing on other planets is temperature. Planets closer to the sun than Earth are too hot; any water would evaporate. Planets farther away from the sun than earth are too cold; any water would freeze. Temperatures on Mars range from 68 F during the summer, to -124 F in the winter, with an average of -81F. So in the summer months Mars can get warm enough to have flowing liquid water! One thing that also helps is the fact that the Martian surface is very salty. This salt gets dissolved in any surface water, lowering the freezing point of water and preventing it from turning to ice. (This is why we throw salt on the roads in the winter, it lowers the waters freezing point preventing ice from forming.) Any water on Mars will be very salty, allowing it to be in liquid form at fairly cold temperatures. Water that has dissolved as much salt as it can possibly handle has a freezing point of -4 F.

This discovery  of this water on Mars has once again peaked interest in astronomers minds about searching for life on Mars. Maybe there are some microbes or bacteria that live in the water during the summer months? We will have to wait for the next round of Mars rovers to find out!

Image Credit:HiRISE, MRO, LPL (U. Arizona), NASA

The Many Types of Disks

If you've ever read an article about young stars, or seen an image of a star forming region, you've probably come across talk of disks around stars. Stars form from giant disks of material slowly falling, or accreting, onto them, so we expect to see disks around young stars. There are many different types of disks, and what you call the disk depends on the age of the star, the disk structure, and other properties of the system. Below are some definitions of different types of disks so you will understand what astronomers are referring to.

Circumstellar Disk: A generic term used to describe a disk of gas, dust, and rocky material around a young star. Most of the following disks are specific types of circumstellar disks.

Accretion Disk: A disk of gaseous material that spinning around and falling onto the young star. Often the inner portion of a circumstellar disk. Accretion disks can exist around other objects as well, such as black holes.

Protoplanetary Disk: A disk around a star that has aged ~3 million years or more containing mostly dust particles and rocks. This is the type of disks that planets form from.

Transition Disk: A slang term for a circumstellar disk around a young star that has a clear hole between the star and the edge of the disk. This occurs, for example, when a large planet forms and clears out a small portion of the disk.

Circumbinary Disk: A disk of material around a binary star system (two stars gravitationally bound to each other.) The disk surrounds both stars at once as if they were one object.

Debris Disk: A disk of material around an older star of any type. If a star begins burning Hydrogen in its core and still has a disk around it, it's called a debris disk. Also, a disk around a neutron star or a white dwarf would be referred to as a debris disk. These may occur from interactions with nearby stars, catastrophic collisions between planets in a system, or after the star dies and explodes.

Infrared image of a circumbinary disk around GG-Tau, taken with Gemini in Hawaii. The two stars are where the star symbols are (their light is blocked out on purpose) and the blue/white is the disk of material.

Image Credit: Gemini Observatory/AURA

HII Regions

Have you ever seen an image of a colored cloud in night sky with the caption HII (read "H-two") region under it? Or heard that the Orion Nebula, pictured below,is  an HII region? HII regions make for nice telescope images, but do you know what they are?

 

Clouds of hydrogen gas in the form of molecular hydrogen (H2)or atomic hydrogen (HI) are where star formation often takes place. These gas clouds collapse in various places, triggering the formation of stars. Groups of young, hot stars emit lots of ultraviolet light which is very energetic. This light is absorbed by some of the atomic hydrogen, causing the hydrogen to lose a electron or become ionized (now called HII). The more stars that form, the more hydrogen they ionize, and thus the larger the HII region. These regions exist most often within the spiral arms of galaxies, where we know star formation is occurring. HII regions exist until some of the young stars within them age and die in a supernova explosion. This explosion causes any HII in the area to be blown away, leaving behind an open cluster of stars.

Image Credit: NASA/ESA

Fourth Moon Discovered Around Pluto

NASA announced the discovery of a fourth moon around Pluto last week! Astronomers were using the Hubble Space Telescope to look for rings around the dwarf planet when they discovered the new moon. It's currently designated P4 until they come up with a better name for it. The Hubble image above shows Pluto and its four moons. The big black bar down the center is used to block most of the light Pluto reflects so faint objects around it, like the moons, can be seen. P4 is only 8-21 miles wide, whereas Charon is 648 miles wide and Nix and Hydra are more like 20-70 miles wide. Pluto is a member of the Kuiper belt, along with 70,000+ other objects, so it's not surprising that Pluto has another moon that went undetected for years. It's difficult to see such small objects in space, even with Hubble! NASA's new horizon mission is currently on its way to Pluto to study the planet and its moons. It will be another ~5 years before New Horizons makes it there, but once it has arrived it will no doubt send back unprecedented information about Pluto and other outer solar system objects

Image Credit: NASA, ESA, and M. Showalter (SETI institute)

Doppler Shift

Astronomers use a phenomenon called the Doppler shift to measure how fast objects are moving towards or away from us in outer space. But how does the Doppler shift work? Here's the common example. You pull over to the side of the road because you hear an approaching ambulance. As the ambulance gets closer, the siren sounds like it's being emitted at a higher pitch. This happens because the sound waves are compressed in the air as the ambulance approaches, making their wavelength shorter and pitch higher. The opposite occurs after the ambulance passes; the sound waves stretch and increase in wavelength and the siren sounds lower pitched. 

Light waves experience this same phenomenon of squeezing and stretching as an object moves. Relative to the Earth, objects that are moving away from us have their light waves stretched to longer wavelengths, making the object appear more red. If an object is moving towards earth, it's light waves are compressed to smaller wavelengths making the object appear more blue. We can measure how Doppler shifted an object is by observing spectral lines emitted or absorbed by different elements in the moving object. In the image above, some absorption lines were red shifted, meaning this object is moving away from us.  The larger this change in wavelength (called "red shift" or "blue shift"), the faster the object is moving. Some objects are moving so or are so far away that their lines are shifted out of the visible spectrum and into other portions of the spectrum not normally seen! Astronomers have viewed many ancient galaxies whose light appears today in the radio, but was originally emitted in the visible spectrum.

Image Credit: Wikipedia commons

What's Next For NASA?

The shuttle program officially ended this morning around 6am EDT as Atlantis safely landed back on Earth at Kennedy Space Center. Many people seem to think that the end of the shuttle missions means the end of NASA. This is by no means true! Just because we aren't sending astronauts into space doesn't mean our space program is shutting down! NASA is hard at work developing new technology for future manned space missions, and is planning many robotic missions for the near future. Hubble, Spitzer, and Chandra are still operational and providing astronomers with gorgeous views of space objects. As long as funding continues, JWST will be launched in the upcoming years giving astronomers huge amounts of data to work with. So much is left to be learned about our own solar system and NASA is working on many orbiters, landers, and rovers will be launched to planets and moons in our solar system.

It's sad to see the shuttle program go, but we can still do great science without sending man into space. In fact it's often easier and more beneficial to send a satellite or robot rather than a person into outer space. To learn more about what's next for NASA, check out this excellent article: http://www.nasa.gov/about/whats_next.html