Friday, September 19, 2008

First planet imaged around a sun-like star

The enormous 8 meter North Gemini telescope in Hawaii captured what appears to be the first image of a planet orbiting a sun-like star(the planet is circled in the image shown).

According to spectra obtained from the image, the dim object is a planet and not a background star like it may seem at first glance.  The planet weighs in at a whopping 8 Jupiter masses and was 330 AU (Earth's distance from sun: 93 million miles = 1 AU)  from its parent star which was 500 light years away from Earth when this image was taken.

Astronomers are hoping to get a follow-up study on this planet to determine an orbit and learn more about this large world.

Normally, Astronomers take careful measurements of a star's movement as it gets tugged by a nearby planet by seeing if the light is slightly blue or slightly red shifted (called a Doppler shift).  This method works best for very large Jupiter-like planets that orbit really close to their star.  The reason Astronomers haven't been able to image planets like this with ease is not just because they're all too faint, it's because the light from their parent star outshines them and blocks out the light.   It's similar to detecting a spotlight and a firefly a few feet apart on the moon.  Planets are similar to that firefly, they're really hard to see!

Using infrared imaging we can see warm planets like this (it has a temperature of around 1800K or 1500°C) next to a star easily since stars give off less light in the infrared than the visible part of the spectrum.

The star - which was creatively named 1RXS J160929.1-210524 - and its planet are very young, astronomically speaking, at only 5 million years old.  This leaves the planet nice and warm and easy to detect since it gives off a lot of infrared light.

Jupiter sized planets aren't supposed to form so far out from their parent star, according to our current theories, so it's most likely that it formed in closer to its parent star and then slowly migrated outward into the orbit it has today.  Van Kerkwijk (one of the authors of the paper announcing the discovery) thinks that this Jupiter-like planet is uncommon and may only be found in one in every 100 stars.

If you want to read more into this interesting find, click here to read the paper announcing the discovery.  The paper is called "Direct Imaging and Spectroscopy of a Planetary Mass Candidate Companion to a Young Solar Analog" and was written by David Lafrenière, Ray Jayawardhana, and Marten H. Van Kerkwijk.

Friday, September 12, 2008

Dust devils around Phoenix

Recently, with temperatures around the Phoenix Mars Lander changing as Winter on Mars approaches, dust devils have started forming.  Scientists working on the Phoenix mission have noticed that they are steadily increasing in number.  They believe this is caused by the growing difference of day and night temperatures which are currently around -30C and -90C, respectively.  The following animated image is composed of 10 images taken during a Martian night and clearly illustrates the moving clouds that are swirling in the night sky and moves in a westerly direction.  Just click the image below to see the animated image.

Phoenix has photographed several of these dust devils (below image, click for animated image) and has even recorded a drop in air pressure as one passed over the Lander .

One of these dust devils had recorded wind speeds that exceeded 5 meters per second (about 11 miles per hour) and range in size from 2 meters (7 feet) to 5 meters (16 feet).  This was recorded with the telltale during the Martian night and is shown in the below image (those blurs moving in the background are clouds, click for animated image).

The winds from these dust devils are now strong enough to stir up dust and shake the solar panels on the Phoenix lander, moving them up about half a centimeter (0.19 in).  In the below image this effect is shown well as you will see on part of the panel, it was blurred in the image as it moved during an exposure in the image below (the white spikey patch is caused by a few overexposed pixels in the camera, it may be a reflection from the sun).

Tuesday, September 9, 2008

Eyeing up Stellar Oddballs

Welcome back to What's Up?

Finishing up on a quick overview of stars, this month will be all about the stellar oddballs.

You may remember white dwarfs from last month, but let's take a closer look into these weird stars.

A white dwarf is the core of a star left over from when a star like our sun sheds off its outer layers and dies.  A white dwarf that weighs as much as our sun would be the size of the Earth which makes it so dense that if you were to take a sugar cube sized portion it would weigh as much as a hippo!

Stars that are less massive than the sun will leave behind a white dwarf mostly composed of helium, the second lightest element.

Stars that weigh around the same as our sun will leave behind a core made of heavier elements since they have the mass to fuse the lighter elements into somewhat heavier ones.  White dwarfs left over from these sun-like stars will be composed mainly of carbon (sixth lightest element) with some oxygen (eighth lightest) mixed in.  The intense gravity of these little stars causes the atoms to get squished together very closely.  This creates a crystalline structure of carbon.  We call this carbon structure a diamond.

Don't think about putting one of these suckers on a ring quite yet.  They are extremely hot.  They are a little over 100,000 degrees Celsius and take billions upon billions of years to cool down to reasonable temperatures.  

If a white dwarf star gathers up enough material to increase to over 1.4 times the sun's mass it will completely explode, leaving nothing behind.  If the remnant from a star is over that 1.4 solar mass limit at the time of death in a star, it will collapse down even further than a white dwarf.  The little negative electrons will combine with the positive protons creating neutrons.  All of the neutrons in the star will be squished together very tightly so that if you took a teaspoon of this material it would weigh as much as a mountain!

Astronomers, using the creativity they are well known for, gave these stars made of neutrons this name: neutron stars.

Neutron stars are very bizarre stars.  If they spin fast enough they will create immense magnetic fields which get twisted and occasionally release enormous amounts of energy.  These neutron stars are called Magnetars.

Some neutron stars have jets that shoot high energy particles out of their north and south poles and as they spin around the jets point in different directions just like a lighthouse.  When these cosmic lighthouses are pointing their beams in Earth's direction we see them brighten and they appear to pulse as the beam appears and disappears.  These stars are called Pulsars.

When stars get larger than about 3 or 4 solar masses the neutrons stars will collapse down even further.  This is where we get a black hole.

Black holes are truly the weirdest things that exist in our universe.  According to theoretical models (lots of juicy mathematical equations) they are infinitely dense points of mass.  Anything that falls into a black hole can't escape unless it travels faster than the speed of light, which is impossible according to Einstein's Theory of General Relativity.

If someone were to fall into the black hole they would become "spaghettified".  The gravity at their feet would be pulling on them so much more than on their head that they would get stretched out into a long noodle shape and then get torn apart.  If they were somehow able to survive being torn apart they would experience a very interesting effect.

According to Einstein's theory of General Relativity, gravity slows down time.  A clock on Earth actually ticks very slightly slower than it would if it were in space.  This has been tested very accurately with satellites.  If there was someone falling into a black hole and they were sending a signal back to us every second we would see this poor bloke's signal separated by longer and longer time spans.  One second between signals... two seconds between... 3... 4...5... and so on until they were spaced by apart by very large amounts of time and the person just faded away and the signals wouldn't get received anymore.

Before time nearly comes to a stop lets see what's up in this month's sky.

Mercury is at greatest eastern elongation on Sept. 11 which means the best time to observe Mercury would be a few days around that date.

Mars and Venus are also in the western horizon this month.  They will be less than a hand width held at arm's length above Mercury in the sky.

On Sept. 15 will be the full moon and on Sept. 29 will be a new moon.

Finally, on Sept. 22 is the Autumnal Equinox, the first day of fall.

Until next month just look up!

Hey Kids...
Remember about the Phoenix mars lander?  It landed on Mars a little more than three months ago and has been digging around in the dirt to see what's in the soil.  It dug down a few inches and hit ice.  Looking at the ice scientists on Earth found out that the ice used to be liquid.  This means tons of liquid water used to be on Mars!  Sadly, it has gotten so cold that all water has since frozen.  Temperatures on Mars where the Phoenix lander is can dip lower than -80 degrees Celsius!  Hopefully the lander brought a winter coat!