Illustration by S. Wiessinger, NASA's Goddard Space Flight Center
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A nova occurs when a white dwarf has siphoned off so much gas from a Sun-like star, such as the one on the right in this artist’s illustration, that it reaches critical temperature and explodes.

Illustration by S. Wiessinger, NASA's Goddard Space Flight Center

This Week’s Night Sky: Earthshine and an Exploding Star

A lucky few in the far north will also see a solar eclipse on the first day of spring.

This week sky-watchers can see a newly discovered stellar explosion and watch the moon play tag with the gods of love and war.

New Star. Backyard astronomers this weekend reported the appearance of a nova quickly brightening in the southern constellation Sagittarius, the Archer.

Discovered by Australian sky-watcher John Seach on Sunday, March 15, the exploding star has been dubbed PNV J18365700-2855420. This star was not previously visible but shot up in brightness to magnitude 6.3 at the time of its discovery. Amateur astronomers in Japan are reporting today that its brightness continues to rise and now sits at magnitude 5.3—making it just barely visible to the naked eye from dark locations and a fairly easy target with binoculars.

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Before dawn this week, Saturn and Sagittarius highlight the skies in the southeast. The giant "teapot" asterism houses a brightening new nova, which is visible through binoculars. 

Discoveries of new novae are exciting for astronomers because they represent stars that are blowing their stack. Novae are the violent explosions of the outer atmosphere of tiny white dwarf stars. These Earth-size, hot cores of long-dead sunlike stars have a companion star from which they gravitationally siphon off gases. Over time, this matter accumulates on the surface of the white dwarf. When the star reaches critical temperature, it ignites in a massive thermonuclear explosion that can be seen thousands of light-years away.

To find this new stellar interloper, start your hunt in the early morning before local dawn and gaze toward the southeast. Look for the distinct stellar asterism pattern of the giant teapot to the far lower left of brilliant Saturn. The nova sits just beneath the triangular teapot lid.

Will this nova continue to brighten or level off? That’s anyone’s guess for now—but the only way to know is to keep watching.

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This sky chart shows the location of the new nova star in the "teapot" stellar pattern within the constellation Sagittarius. 

Solar Eclipse. On the morning of Friday, March 20, a total solar eclipse—the first since November 2013—will occur over the North Atlantic and Arctic Oceans.

A solar eclipse occurs when the Earth, moon, and sun are in perfect alignment such that the sun’s entire disk, as viewed from Earth, is blotted out by the moon. Such an event lasts for only a few minutes, and any one location on Earth gets to experience this rare event on average only once every three centuries. 

Lucky sky-watchers in southern Greenland and Norway’s Svalbard Islands will have front-row seats as the moon completely covers the sun and its shadow creeps across Earth’s surface along a path that is less than 62 miles (100 kilometers) across.

Vernal Equinox. Also on March 20, at 6:45 p.m. EDT, spring will have officially sprung for the Northern Hemisphere.

The vernal equinox marks one of the four major turning points in the cycle of our planet’s seasons. The seasons exist because the Earth is tilted 23.5 degrees. As the planet travels around the sun, the Northern Hemisphere tilts either away from (during winter) or toward (during summer) the sun. The exceptions are the vernal and autumnal equinoxes. The word equinox comes from Latin meaning “equal night,” and it’s on this day that light and dark appear to be about the same length—roughly 12 hours each of day and night.

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This simulated view of the sky on Saturday at dusk shows the thin crescent moon paired with faint Mars. 

While it still may seem like winter lingers on the ground for many in the north, we can take heart in that this part of the Earth will soon warm up as the midday sun climbs higher and days get longer.

The next time a solar eclipse and the spring equinox fall on the same day will be in the year 2053.

Silver Moon With Red Mars. A slight sliver shines in the sky on Saturday, March 21, just after dark. The moon is still young and shines only four percent of its full size that night. The moon’s dark side will also brighten due to a phenomenon called earthshine. It’s caused by sunlight reflecting off the Earth onto the dark portion of our own gray satellite.

As a bonus, just to the right is our planetary neighbor Mars. A mere one degree away from the moon, this ruddy planet, so frequently visited by our technology, can be seen with the naked eye. But the view is better with binoculars or a small telescope. Although this reddish “star” seems to be shining, a visual aid will allow stargazers to see that it is a disk with Mars’ signature red hue.

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This simulated view of the sky on Saturday at dusk shows the thin crescent moon paired with faint Mars. 

Growing Moon, Glowing Venus. Yesterday, the moon guided stargazers to Mars. On Sunday, March 22, it shows the way to Venus.

By now, the moon has grown in girth to 10 percent of its full size and moved higher in the sky. Gaze over to its right, and there will be brightly shining Venus, only three degrees away, closer to the Sun.

Venus is called our sister planet because it is almost the same size as Earth but has a carbon dioxide atmosphere with sulphuric acid clouds. Living under this toxic vapor would be impossible for us, but we can thank those clouds for making Venus appear so bright in our skies.

Happy Hunting!

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