Proxima Centauri is the closest star (excepting the Sun) to Earth. It is a red dwarf a bit more than a tenth the mass of our Sun, and about four light years away. We don’t know if it has any planets, but that may change in a few years due to a fortunate alignment.
Dark of Night
When you look up in the night sky, there are areas of the sky that appear dark. That’s because there is nothing in that region bright enough for us to see with the naked eye. If you looked upon this region with a telescope, you would find dim stars and galaxies, but you would still see areas that appeared dark to you. How far could you take this? If you kept looking at smaller and smaller dark regions with ever more powerful telescopes, what would you see?
Shades of Gray
Despite all the wonderful color images we have from the Hubble space telescope, there is no color camera on the Hubble. The main reason for this is scientific. When observing astronomical objects, you’d like to get as much light as you can from the object. You also want to get as wide a range of wavelengths as you can.
Rumor Weed
Yesterday there was a flurry of news about a gamma ray burst (GRB) appearing in the Andromeda galaxy. This would make it the closest observed gamma ray burst, which would be a boon for astronomers. News of this discovery travelled fast, particularly on Twitter and other social networks. Pretty soon a few news sites had picked up the story. But it turns out it wasn’t a gamma ray burst.
Adaptation
If you’ve ever looked up in the night sky you’ve seen the twinkling of the stars. This twinkle is not due to the stars themselves, but to the turbulent motion of the Earth’s atmosphere. As starlight enters our atmosphere, the variations in density in turbulent air cause the light wave fronts to distort. So instead of reaching the telescope evenly like even rows of a band on parade, the wave fronts come in uneven and wobbly. This wobbly behavior is why stars appear to twinkle.
Losing Direction
Launched in 2009, Kepler was intended as a “planet hunter” telescope. It finds planets by observing stars for long periods of time. To make long observations, Kepler needs to be able to point in the same direction very precisely, and it must be able to adjust its direction if it starts to drift. So how do you keep a telescope oriented?
Reading the Rainbow
Our eyes see color through cones in our retina, where the three different types (S, M, and L) each have a slightly different range of wavelengths to which they are light sensitive. Through the response of these different cones our brains are able to distinguish different wavelengths of light, which we interpret as color. Telescope detectors typically have a much wider range of light sensitivity, which is good if you want to detect a great deal of light, but not so good if you want to observe a particular color range. So many telescopes have filters that block light outside a particular range.
Blood Moon
This week those of us in the western hemisphere will have the chance to observe a lunar eclipse. It will happen in the evening/morning of April 14/15, reaching peak darkness at about 3 a.m. EDT (0600 GMT). Depending on the darkness of your sky, the Moon may be invisible to the naked eye, or it may appear as a dark, blood moon.
Parallax View
How is it possible to say with confidence that one star is 8 light-years away, while another is 640 light-years away? There are actually several methods to determine cosmic distances, and these are combined to create what is known as the cosmic distance ladder, but the oldest and most direct method uses the property of parallax.