Rare nova visible in predawn sky
Posted April 6, 2015
Clouds spoiled Saturday’s lunar eclipse, but another rare treat waits in the predawn skies.
John Seach of Chatsworth Island, New South Wales, Australia, discovered a nova in the constellation Sagittarius last month. The University of Liverpool confirmed it as Nova Sagittarius 2015 Number 2, estimating gas being ejected at more than 6.2 million mph (10 million km/h). This is the brightest nova in Sagittarius since 1898 and brightest elsewhere in the sky since Nova Centauri 2013 peaked in December 2013,
At the time of discovery, Nova Sagittarius was just beyond the visual limit of the naked eye. Since then it’s brightened, dimmed and brightened again to the fourth magnitude (the human eye is limited to seeing objects at about sixth magnitude from a dark location). Recent observations by members of the American Association of Variable Star Observers put the brightness at about magnitude 4.5. While this isn't something observers in downtown Raleigh are going to be able to make out, it should be possible to see from darker locations.
While the word nova comes from Latin for “new,” novae aren’t new stars. Novae are white dwarf stars in a binary star system, which draw off gas from a companion star triggering an explosion. That explosion significantly brightens the star, usually for a period of months, but unlike supernovae, aren't enough to destroy the star. So, think temporary power surge, not death star.
To see the nova for yourself, look to the south between Sagittarius’s rise around 3 a.m. and before nautical twilight begins to brighten the sky at 6 am. Look to the lid of the “teapot” asterism within Sagittarius. A little to the left of a point just below the line formed between Phi Sagittarii on the left (stars within a constellation are identified by Greek letters in descending order of brightness) and Epsilon Sagittarii on the right, you will see the nova which should appear white to the naked eye. The nova will be a bit dimmer than the left star in the lid. A decent pair of binoculars or small telescope will improve the view. You may even notice a slight yellow color, which recent observers have noted, is deepening.
While you are out, be sure to look for Saturn up and to the right of the orangey star Antares (Greek for “rivaling Mars”, which it is often mistaken for). Those binoculars or small telescope can reveal Saturn’s rings that are tipped toward Earth (and will be for the next 10 years).
If you prefer evening to pre-dawn hours, the International Space Station will again be visible over central North Carolina this week after sunset. Monday look to the west at 8:47 p.m. for a pass lasting a little more than 5 minutes before setting in the NNE, on Tuesday look WSW at 7:53 p.m. for a pass reaching 43º above the horizon before setting in the NE 6 minutes later, and finally look to the WNW.
Tony Rice is a volunteer in the NASA/JPL Solar System Ambassador program and software engineer at Cisco Systems. You can follow him on twitter @rtphokie.