Bright Lights in the Sky

No UFOs Here

The post-sunset view on March 11, planets Venus and Jupiter. Click for a larger view.

Unless you’ve been buried under a blanket of clouds the past few weeks, you’ve probably noticed some bright lights in the western sky just after sunset.  Aside from the Moon (and you know what that looks like, don’t you?), you might be wondering what they are.  Well, if they’re not moving rapidly (like changing position over the space of a few minutes, as aircraft would do), then what you’re seeing are the planets Venus and Jupiter.  Here’s tonight’s view of the pair, well after sunset. You won’t see Mercury (too close to the Sun), but you can’t fail to notice how dazzling the two planets appear these early springish nights.

If you have binoculars or a small telescope, check out Jupiter. You might be able to see its four largest moons. They’ll look like little pinpoints of light on either side of Jupiter.

Mars is just below Leo, and Saturn and Spica rise together later in the evening. Click to ensaturnate.

 

The next couple of nights, these two planets snuggle up really close together in the western sky.   Once you’ve found them, and turn toward the east and look for Mars snuggled up underneath the constellation, Leo the Lion.  An hour or two later, you should be able to find Saturn just rising in the East. It’s a planet spectacular!

Of course, there are a lot of other things to look at in the sky this month, so don’t run back inside after you’ve seen the planet.  Dress warmly (if it’s cold where you are), and explore that sky!  There’s a lot to be found.

By the way, check out “Our Night Sky” at Astrocast.TV for a short program I did on what’s up this month.  It’s free to embed on observatory and planetarium Web sites (with proper credit, of course), so check it out!

 

 

 

Black Hole Munches Asteroids

Is There No End to Its Incessant Demands?

This image from NASA's Chandra X-ray Observatory shows the center of our Galaxy, with a supermassive black hole known as Sagittarius A* (Sgr A* for short) in the center. Using intermittent observations over several years, Chandra has detected X-ray flares about once a day from Sgr A*. The flares have also been seen in infrared data from ESO's Very Large Telescope in Chile. Click to embiggen.

How did I miss this story?  Early in February, the folks working with the Chandra X-ray Observatory announced that they’ve been watching the black hole at the heart of the Milky Way Galaxy munching down on asteroids.  According to them, this happens pretty frequently. They’ve seen the evidence:  once-a-day x-ray flares from Sagittarius A* (that’s the name given to our central black hole), or Sgr A* for short. The flares last a few hours, and have also been seen in infrared light by detectors at the Very Large Telescope in Chile.

The idea is that there is a cloud around Sgr A* containing hundreds of trillions of asteroids and comets. Where did they come from? Astronomers suggest that this debris collection is made of material stripped from the parent stars by the force of gravity.

An asteroid that gets too close to  another object, such as a star or planet, can get thrown into an orbit that places it on a heading for  Sgr A*.  If it gets too close — say within 100 million miles of the black hole (about the distance between Earth and the Sun) it would be torn into pieces as it encountered the  tidal forces from the black hole. These fragments would be vaporized as they pass through the hot, thin gas that continually flows toward Sgr A*.  This is very similar to what happens to a meteor when it encounters Earth’s atmosphere for example. It heats up and glows, and eventually it vaporizes, and we see a flare marking the end of the meteor’s trip. When an object does this near Sgr A*, we can see it in x-rays and infrared.  Whatever’s left of the asteroid gets sucked into the black hole.

This is kind of a cool thing to see at an object so far away, and Chandra’s still on the case. Over the next year or so, the satellite will study more of these things that go “fuff” in the night near Sgr A*.