Enjoy our starry night skies

Be a considerate neighbor: Reduce nighttime glare. Shield your outside lights downward, so no glare goes up to dull the night sky (or in your neighbor’s bedroom windows) and enjoy the beautiful, stars above.

Photograph of the monster star, Eta Carinae, by the Hubble Space Telescope WFPC2, June 10, 1996

February 2008 Night Sky—The Unstable Southern Monster

—CHARLIE CHRISTMANN

Just below the horizon for most Americans is a monster star called Eta Carinae in the constellation Carina. If you live along the southernmost U.S. or better yet, in Hawaii or the Caribbean, this star barely gets above the southern horizon. Located about eight thousand light years (47,028,000,000,000,000 miles) away, Eta Carinae is one of the brightest stars known in our galaxy, shining as bright as five million Suns.

Between 1822 and 1855, Eta Carinae had several major temper tantrums. In 1820, Eta Carinae began to brighten. By 1822, it had brightened from a fourth magnitude to a second magnitude (smaller magnitude numbers are brighter and negative numbers are brighter still) and first magnitude by 1827. It faded for about five years before becoming a zero magnitude star. After another fading period, it glowed almost at a magnitude of -1.0 in April 1843, outshining all stars in the sky except Sirius (remember, planets are not stars). The result of this outburst was the Homunculus Nebula. Much of the light leaving Eta Carinae is absorbed, scattered, and generally dimmed by this nebula, resulting in a fifth magnitude star as seen from Earth.

The reason for this type of behavior is its size. You may have heard of supergiant stars; that does not even begin to describe Eta Carinae’s size. Astronomers call it a hypergiant. Eta Carinae weighs in at more than 150 times the mass of our Sun. Other stars in the rarefied category of hypergiant include P Cygni, in the heart of Cygnus the Swan, and Rho Cassiopiae in Cassiopeia, but neither can match Eta Carinae.

Scientists called the mid-1800s outburst a “supernova impostor.” It looked like a supernova, but the star survived. As unstable as this star seems to be, its lifetime will be very limited. Massive stars have a short lifetime, roughly one million years. Eta Carinae must have formed “recently” in the cosmic sense. It is located in the active star forming nebula NGC 3372. It will probably end its life in a supernova (or would hypernova fit better?) explosion in ten thousand or twenty thousand years. The end result will be the addition of material to the Homunculus Nebula with a central black hole.

So what happens to us when Eta Carinae goes nova? Researchers have suggested that one or more mass extinctions during the past few hundred million years might have been triggered by a supernova. In a supernova, large amounts of “star stuff” are flung trillions of miles into space along with dangerous gamma rays. The worst of the gamma rays are concentrated in two oppositely directed beams leaving the rotational poles of the former star. Among the negative effects of a large dose of gamma rays is a sudden depletion of Earth’s protective ozone layer. Left naked, the Earth could be fried by the UV rays of our own Sun.

Fortunately in the case of Eta Carinae, most people who study this star think that the rotational axis is along the symmetry axis of the Homunculus Nebula. This axis is tilted by about forty-five degrees to our line of sight, which means that most of the dangerous gamma radiation would not be directed at us. However, there might be enough radiation to disable communication and other satellites, and perhaps astronauts, in orbit. To be really dangerous to Earth, the nova would need to be within thirty light years (176,355,000,000,000 miles).

One effect earthlings will notice is just how bright the nova will be. For about six months or so, not only will the afterglow of the blast cast a bluish glow in the southern night sky strong enough to read by, it will also be visible during the day.

So, why are astronomers worried now? Eta Carinae suddenly and unexpectedly doubled its brightness in 1998–1999 from eighth to fifth magnitude. Is this the start of another outburst, or is this the beginning of an unexpectedly early supernova? Stay tuned; only time will tell.

The Planets and the Moon

• Mercury will be in the glow of the rising sun most of the month. But, on the 27th, use binoculars about forty-five minutes before sunrise, at about 7:00 a.m., to look for Mercury positioned above and slightly left of Venus.

• Venus will rise in the east-southeast about thirty minutes before sunrise. On the 1st, look for Jupiter and Venus very close together as they rise at about 7:00 a.m. It will be worth a look as Venus rises just ahead of Jupiter.

• Mars will be high in the east at sunset. The Moon and Mars will make a spectacular grouping on the night of the 15th. Aldebaran will be to the right of the Moon with Orion below.

• Jupiter rises about an hour before sunrise, ahead of Venus, in the east-southeast most of the month. Look again at 6:35 a.m. on the 4th as the crescent Moon, only two days from new, joins Jupiter and Venus as they rise. Jupiter will be leading the pack this time around.

• Saturn rises just after sunset early in the month but disappears in the sunset late in the month in the east-northeast.

• If you have a good telescope, you will find Pluto about ten degrees above Venus in the morning sky this month.

• Are you ready for a lunar eclipse? It happens on the evening of the 20th. The show begins at 6:09 p.m. MST before moonrise in New Mexico. Moon rise here is at 6:42 p.m. Totality starts at 8:00 p.m. and lasts for fifty-one minutes. The Moon will be partially eclipsed until 10:00 p.m. Check out Saturn to the lower left of the Moon that evening. The 20th is also the night of the “Full Snow” Full Moon. The next partial or full lunar eclipse visible in the U.S. will not be until 2010. The New Moon is on the 6th.

If you have a question or comment for Charlie, you may email him at: k5cec@yahoo.com.

Celebrate Lunar New Year—build a dragon at the Placitas Library

The Placitas Community Library invites everyone—adults and children of all ages—to join with the millions of people in or from Far East countries in some traditional, and not so traditional, ways of marking the Lunar New Year 4705. This year’s celebration, in honor of the Year of the Rat, will be held at the library on Saturday, February 16 from 10:00 a.m. to 4:00 p.m., with special activities planned from 10:00 to 11:30 a.m.

Learn your Chinese zodiac sign and what the Year of the Rat holds for you. Enjoy stories about Lunar New Year customs, play trivia games and word searches, create your own Chinese lanterns and snack on traditional New Year candies and fruits. Special guest Choon Fritch will create New Year’s cards for children personalized in Korean calligraphy while her son Chan David and his friends will present a demonstration of a traditional martial art, Tae Kwon Do, around 10:30 a.m. There will be activities for all ages, prizes, decorations to add to the festivities, and the official presentation of the New Year Dragon.

The library encourages the entire community to help create this special dragon by stopping in at the library beginning February 2 and making an outline of your hand on construction paper. Put your name on your hand print and it will be added as a scale to form the dragon’s body. Large and small, all hand prints are welcome. They ask that everyone “give them a hand” to make this the biggest, best dragon Placitas has ever seen.