Stargazing 03-03-18

There are more than 100 billion galaxies in the observable universe and keeping on eye on each one of them is, shall we say, “difficult to do.” A supernova will happen in a galaxy roughly once a century. Seems like a long time to wait but when you have 100 billion galaxies to work with, there will be many supernova going off somewhere in the universe in any given year but where should you look to catch one just beginning to happen?

Even with all the huge array of telescopes pointed up at the sky on any given night around the world for many decades, we haven’t caught a supernova in its beginning stage. That is until Victor Buso, an amateur astronomer in Argentina, pointed his telescope at NGC 613, a spiral galaxy about 68 million light years away from us, so we are seeing the galaxy as it was 68 million years ago. Up until Buso’s observation, no one had seen the “shock breakout phase” of a supernova that occurs in the first few hours as the shockwave from the sudden core collapse, which triggers a supernova, reaches the huge star’s surface.

When the shockwave reaches the star’s surface, the gas layers heat up, blast outward, and the star gets brighter and brighter at a rate of 10 quadrillion times per day. (I had to look up what number equals a thousand trillion —“quadrillion” is the name for that number.) After Buso and Sebastian Otero, a fellow amateur astronomer and friend, sounded the alarm, other ground-based research telescopes and space telescopes were pointed at NGC 613 to catch those precious photons encoded with all sorts of information about the death of a star much more massive than the sun.

Only the very massive stars will have the violent death of a supernova. These stars are very rare — much less than 1 percent of the stars out there. Most stars, including our sun, will have a gentler way of dying. Analysis will continue on the observations being gathered from this supernova but Buso’s observations already do finally confirm the theoretical models of what happens in the first several hours of a supernova explosion.

Venus rising

Closer to home, another brilliant spot continues to climb higher up in the early evening sky. That spot is Venus, which is now probably high enough to be above the dust and smog layer after sunset. Venus’ separation from the sun as seen from Earth will increase through spring and we’ll have an easier time seeing it.

Venus appears so bright in our sky because it is the closest planet to us and its clouds made of sulfuric acid droplets reflect 77 percent of the sunlight reaching Venus. One popular science article I read said that Venus is so bright because of its thick atmosphere. The picky astronomer in me said, “No, the thickness of atmosphere doesn’t make it reflect so much sunlight — the clouds do and they make up a teeny tiny (to use a highly technical scientific term) fraction of its atmosphere.”

Venus’ atmosphere is 96.5 percent carbon dioxide and 3.5 percent nitrogen both of which are transparent to visible light. The other trace gases (like sulfur dioxide, argon, and water vapor) are measured in parts per million. The carbon dioxide is not transparent to infrared energy, which is why Venus is so darn hot (another technical scientific term). Carbon dioxide is a greenhouse gas that traps infrared energy close to the surface and Venus has a lot of it — its surface air pressure is 92 times higher than Earth’s.

In the night sky

Saturday night you’ll see Mercury right next to Venus about a thumb width at arm’s length to the right of Venus. Speedy Mercury will climb higher past Venus and reach its greatest separation from the sun on March 15 but it will get slightly dimmer as it does so.

The moon was at full phase Friday, so we’ll get a “blue moon” at the end of March but no lunar eclipse. The moon will be at perigee (closest to Earth) on March 26, so no “supermoon” either. Saturday the gibbous moon will rise shortly after 8 p.m. and wash out most of the sky for the rest of the night.

Early risers will see a nice lineup of the outer planets, moon and the two bright stars Antares and Spica. In Sunday morning’s sky, the order, from left, will be Saturn, Mars, Antares, Jupiter, Spica and the moon. You might have a hard time seeing Spica next to that bright moon. The accompanying chart shows the moon’s motion over the next several mornings. On March 10, the waning crescent moon will form a beautiful triangle with Saturn and Mars.

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