Mercury appears low in the west- southwest evening sky during the last week in January in one of its best evening appearances of the year. Look for it with binoculars, soon after sunset.
Venus hugs the western horizon during evening twilight during the first few days of the month and then disappears into the solar glare as it swings between Earth and the sun. Then, this brilliant planet reappears during the last week of January, low in the east-southeast before dawn.
Reddish Mars rises in the east around midnight as January begins and appears higher each night as the month progresses. It will also become brighter as Earth, in its faster orbit, catches up with it.
The largest known star (by radius) is the red hypergiant VY Canis Majoris. Although its temperature is cooler than our sun, its total luminosity is 500,000 times that of the sun.
Courtesy Universe Today
There is a vast range of star sizes. Some neutron stars are just 20 miles in diameter and many white dwarfs are the size of Earth. The largest known star, VY Canis Majoris, has a radius estimated to be 2100 times the radius of our sun.
Courtesy Dave Jarvis
This shows the size of our sun in comparison to the planets. The mass of the sun accounts for 99.86 percent of the total amount of material in the entire solar system.
It’s easy to spot reddish Betelgeuse (arrowed) in the constellation Orion this month. As you view it, remember that this red supergiant is larger than the size of Jupiter’s orbit.
Courtesy A. Dupree, CfA, NASA, ESA
Some of the largest, hottest and most massive stars known lie in this huge star cluster in the Tarantula Nebula, 170,000 light-years away from Earth. Powerful winds and ultraviolet radiation from these gigantic stars has sculpted the dust and gas clouds into elongated shapes.
Courtesy NASA, ESA, INAF-IASF, U. Virginia
Jupiter shines brightly in the east during evening twilight. The mighty planet is at opposition on Jan. 5. On that date it is opposite the sun in Earth's sky and is visible all night long. Steadily held binoculars will allow you to see Jupiter's four largest moons.
Beautiful Saturn appears low in the east-southeast predawn sky. This planet has more moons that are visible in medium to large amateur telescopes than any other planet. These moons orbit outside the incredible ring system.
The Quadrantid Meteor Shower peaks in the predawn sky on the morning of Jan. 3. There will no moon in the sky to interfere this year, so you should be able to see even the faint meteors if you pick a dark observing site.
THE LARGEST KNOWN STARS
"Two men look out the same prison bars; one sees mud and the other stars."
Currently, the largest known star (in terms of radius) is VY Canis Majoris, a red hypergiant located about 5,000 light-years away in the constellation Canis Major. If it occupied the position of our sun, its surface would extend out beyond the orbit of Saturn. It would take light over 8.5 hours to travel around this star, compared to the 14.5 seconds to travel around our sun. Although its size is fantastic, it is somewhat cooler in temperature than the sun.
The largest known star in terms of mass and brightness is the so-called Pistol Star, which is over 100 times more massive than the sun and nearly10 million times brighter. It radiates as much energy in 20 seconds as our sun does in an entire year. This incredibly brilliant star is 25,000 light-years from Earth and is mostly hidden behind gigantic dust clouds near the center of the Milky Way Galaxy. Ultrabright and ultramassive stars like that are very rare and are near the upper limit for stars in our region of the universe.
Another huge and extremely luminous star in our Galaxy is Zeta Puppis, one of the nearest massive stars to Earth. It is over 1,000 light-years from our planet but is so bright (550,000 times more luminous than the sun) that it can be seen without optical aid from the Southern Hemisphere. Massive stars like Zeta Puppis burn their nuclear fuel much more quickly than stars like the sun and usually explode as supernovae after just a few million years. Throughout their brief lives they eject a tremendous fraction of their mass through fierce winds that continually stream from their outer layers.
Probably the most well-known massive star in our sky is Betelgeuse in the constellation Orion. It is a red supergiant that lies 640 light years from our solar system. If placed in the position of our sun, its outer atmosphere would extend out beyond the orbit of Jupiter. Nearing the end of its life, astronomers believe that Betelgeuse will become a supernova sometime within the next million years. At the present time, the mammoth star is ejecting material equal to the Earth's mass every year.
While the largest stars live a fast and furious life, giving off tremendous heat and light, they experience a relatively short lifespan of only a few million years. Fortunately, our much steadier and lower key sun still has a life expectancy of billions of years. In fact, our sun has been converting hydrogen into helium for 4.57 billion years and yet has only converted 0.03 percent of its mass into energy.
Editor's note: This monthly guide to the stars is from the Marshall Martz Memorial Astronomical Association and The Post-Journal. For further information, contact the M.M.M.A.A. at www.martzobservatory.org