Archive | Astronomy RSS feed for this section

Transit of Venus

5 Jun

Don’t forget to watch the transit of Venus today, when Venus will pass in front of the sun. It will be visible around sunset here in the US.

Don’t forget to use proper safety precautions. Sunglasses are not enough. If you have welding glasses, those work great. If you don’t have welding glasses or special eclipse viewing glasses, you can use a pinhole projection, but it will need to be magnified to see anything. You can use a telescope to project an image onto a piece of paper (big end towards the sun), and view it that way.


Earth-like planet a result of a gas giant getting swallowed?

12 Jan

Some interesting questions have been brought up by these recent Kepler discoveries. Stars like our sun usually expand to become red giants and then become compact again as helium fusion begins in their cores. Sometimes, the hydrogen is stripped off of the star (by another star for example), leaving just the helium-fusing core behind, compact and very hot. A star in this state has been observed (a hot B subdwarf), where the hydrogen was stripped off, except there is no companion star to have taken the hydrogen away. It’s a cosmic mystery: What happened to the hydrogen?

This star system has several recently-discovered small, (presumed) rocky planets orbiting it. The emerging theory is that when the star expanded to become a red giant, it consumed several gas giants with orbits close enough to be swallowed. When the star contracted again to enter the helium fusion phase, the planets reemerged as small, rocky planets, stripped of their gaseous exteriors. The disruption resulting from the planetary collisions with the star could have stripped the star of some of its hydrogen, causing it to be in the state we now find it: very hot, with several small, rocky planets locked in a tight orbit. Time will tell if this theory is correct. There is so much we don’t understand about the birth and evolution of stars and planets.

Article here.

More earth-sized planets discovered

11 Jan

Scientists have spotted 2 earth-sized planets in an extremely tight orbit around a star very like our own sun.

Article here.

First habitable-zone planet discovered

3 Jan

Observing planets outside our solar system has always been a challenge. The only way to spot one is when a planet crosses in front of its star and causes a fluctuation in the light emitted from that star. Such small fluctuations are difficult to observe from earth, where conditions have to be just right and atmospheric effects accounted for. In the past, we have been able to spot mostly large, Jupiter-sized planets. So, in 2009, NASA launched the Kepler spacecraft, whose only purpose is to observe planets outside our solar system from space, free from atmospheric troubles.

The data are flowing back fast. In fact there have been over 200 earth-sized planets spotted that are waiting to be confirmed by earth-based telescopes before announced. Forty-eight of the planetary candidates lie in the “habitable zone” of their solar systems, which means that the temperatures are right for liquid water to be sustained on the surface. That doesn’t mean they do have liquid water; it just means that it is a possibility. We are waiting on the ground telescopes to confirm these planetary candidates. And then we can get to work on determining their densities, and therefore what they’re made of.

Kepler 22-B is the first confirmed habitable-zone planet discovered outside our solar system. It is on the inside of the habitable zone. Were it in our solar system, it would be somewhere between Earth and Venus.

You may remember the discovery of a planet closely orbiting a double-sun (Kepler 16-B), confirmed by ground telescopes in Septemberish of 2011. Stay tuned for more exciting planetary discoveries from Kepler (there were several exciting ones over Christmas break).

Lunar eclipse

9 Dec

Don’t miss the total lunar eclipse tomorrow. The earth will pass between the sun and the moon, covering the moon with earth’s shadow and making the moon appear red. The moon normally appears white or grey in color because it reflects the light from the sun directly and encompasses the entire visible spectrum. During an eclipse, the direct sunlight will be blocked by the earth. The only light that will reach the moon will be the light redirected by the earth’s atmosphere, which will cause the moon to be sunset red in color.

This will be the last total lunar eclipse visible from North America until 2014. The eclipse will begin at about 4:45am, and be full from 6am to 7am tomorrow morning, Pacific time. Set your alarms and get up a little early. It will be worth it!

Black holes: Friend or Foe?

7 Dec

Too often, black holes are depicted as prowling, hungry, colossal beings that swallow everything in their path and wreak havoc on the Universe. Although that makes for good science fiction, it is pretty far from the truth. Here’s what’s up with black holes:

How they’re born:

Black holes are born when massive stars die, meaning they explode and collapse inward on themselves. Smaller stars that die turn into white dwarfs. More massive stars that collapse turn into neutron stars. Stars bigger than about three solar masses, however, are too massive to support any structure, even one as dense as a neutron star. These super massive stars turn into black holes when they die.

What they are:

A black hole is a region of space where the gravitational force is so large that the escape velocity is greater than the speed of light, meaning that even light cannot escape the region. It contains a singularity inside that region of space, or a point of infinite density. The matter from the core of the star collapses so far that there is no longer any force to stop it from collapsing and it collapses to a point of zero radius and infinite density, meaning that the surface gravity is infinite at that point as well. There is some debate as to whether the point at the center of a black hole is actually a singularity of zero radius. Some say that there cannot be singularities in nature and that the collapse must halt at some extremely small radius (like way, way smaller than a proton). But in practice, it doesn’t really matter either way. You still have your crazy-dense point surrounded by a region that light cannot escape from.

To understand black holes a little better, let’s step back for a minute and talk space-time. Einstein is the one that discovered the link between space and time. Space and time are cut from the same cloth: the fabric of the Universe, a material that we now call space-time. Gravity exists because objects with mass warp space-time, and cause other objects with mass to fall towards them because of that warping. It would be as if you had a sheet pulled tight at all edges and put two heavy balls near each other on the sheet. The balls would roll towards one another because of the dents they put in the sheet. This is the same phenomenon that causes gravity, except in two dimensions. Black hole singularities warp space-time so much that it wraps around upon itself again, and nothing can escape this region of super-warped space-time. This is known as the event horizon.

How they live:

There are many different kinds of black holes, mainly the differences are size (which is proportional to how much matter the black hole has consumed), rotation, and electrical charge. Black holes with rotation and charge have very large, complex magnetic fields surrounding them that actually spew out a stream of matter along the magnetic poles (not matter from inside the black hole, just some of the stuff that approached it). The stuff being spewed out of the black holes are called jets. See photo above. There is a visible accretion disk of matter surrounding the black hole, and long jet streams coming out of the magnetic poles.

Why you don’t have to lock your doors at night because of them:

So far, so good. It is true that nothing can escape from inside a black hole and that as far as we know, they can continue swallowing matter indefinitely. The misconceptions begin when people start talking about black holes like we are in danger of being swallowed by a black hole at any second. The truth is that the force you feel from a black hole is the same as the force you’d feel from any form of matter with an equivalent mass, unless you get up really close. In fact, if you were to replace our sun with a black hole of equivalent mass, we would not feel the difference gravitationally. The earth would continue to orbit around the black hole the same way that we do now around our sun. Of course the lack of light would be a bit noticeable after a couple of minutes, but you get the idea. It is true that our galaxy might collide with another galaxy someday, and there’s a chance that we’d end up at the center of that galaxy’s black hole in the process, but it is extremely unlikely, and it’d be so far into the future that odds are none of us’d be around to witness it anyways.

Semi-recent discoveries have indicated that there are black holes at the center of every galaxy,  including our own Milky Way Galaxy. The truth is that black holes are really a natural, benign part of our Universe, holding galaxies together and intriguing scientists on this insignificant little planet called earth. So where’s the love?

Here’s a shoutout to the reader that asked an awesome question about black holes and inspired this post. There’s some good black hole reading here if you’re interested in learning more.

Oldest recorded supernova

31 Oct

This picture was recently released by NASA. It was made by combining data from 4 different space telescopes at different wavelengths. RCW 86 is the oldest documented example of a supernova, and was observed by the Chinese in 185 A.D. They called it a “guest star” and documented that it stayed in the sky for 8 months.

Data from the X-ray spectra (shown in blue and green) show that the interstellar gas has been heated to millions of degrees by the passing shock wave caused by the supernova. The infrared data (in yellow and red) show dust that is radiating at several hundred degrees below zero, which is warm compared to our galaxy’s dust. This thing was a class 1A supernova that was caused when a dead star (a white dwarf) sucked a bunch of material off of a companion star. RCW 86 has gotten large quicker than it should have. It is postulated that the star released gasses and blew out a region of low-density prior to going supernova, allowing the explosion to reach a large area very quickly. It is pretty neat that we know all of this partly thanks to the work of scientists 2000 years ago. Imagine what we will know about the universe a couple thousand years from now.