Wonders of outerspace: `New` stars visible in September
`Nova Delphinus 2013, discovered by a Japanese amateur astronomer Koichi Itagaki this August, is one of the very few novae visible to the naked eye. Find out about others you can in September.
Astronomers call erupting stars Novae—Latin for ‘new’—because they abruptly appear in the sky. The most recent discovery of a nova was made on 14th August 2013 by Koichi Itagaki from Yamagata in Japan. Using a small reflecting telescope with a CCD camera, the amateur astronomer discovered a ‘new’ star in the constellation of Delphinus, as it brightened enough to be visible to the naked eye, but at present its brilliance is just below naked-eye visibility.
A nova occurs in a close binary star system, in which a small, but extremely dense, white dwarf star pulls hydrogen from its closely orbiting companion, a cool red giant star. After swirling about in a disk around the dwarf, the gas is funnelled down to the star’s hot surface, where gravity compacts and heats it till it detonates like billions of thermonuclear bombs. That’s how a faint star that was almost invisible suddenly appears as if out of nowhere.
At first the nova shines brightly, but the gas expelled in the blast travels away from the binary star at speeds reaching 3,200 kilometers per second. This results in an expanding shell of debris, but the stars are not destroyed. Classical novae recur when the flow of gas onto the white dwarf resumes after several years and produces an outburst.
Nova V838 Monocerotis
Vincent van Gogh`s famous painting ‘Starry Night’ is renowned for its bold whorls of light sweeping across a raging night sky. Although this image of the heavens came only from the artist`s restless imagination, the image of Nova V 838 Monocerotis from NASA`s Hubble Space Telescope bears remarkable similarities to the Van Gogh painting, complete with spirals of dust swirling across trillions of kilometers of interstellar space.
Nova Cygni 1992
Astronomers got their earliest look at a rapidly ballooning bubble of gas blasted off Nova Cygni 1992, which erupted in the constellation Cygnus.
It was one of the brightest novae in 20 years, reaching naked eye visibility for a brief period. Due to the shell of gas surrounding the nova, astronomers were able to ascertain its diameter and precisely measure its distance from the Earth, as 10,430 light-years.
Erupting star T Pyxidis
The close double star system, T Pyxidis is a recurring nova that saw its last outburst in April 2011 after 45 years of peaceful bliss. It is located in the southern constellation Pyxis also known as the Mariner`s Compass. Astronomers have been able to capture the light echo, a flash of light accompanying the blast, for this nova. Contrary to some predictions the ejected materials stayed in the vicinity of the star and formed a disk of debris, which expands outward along the system`s orbital plane, but doesn`t escape the system.
Viewing Equipment: Nova Delphinus 2013 can be seen with a pair of binoculars or small telescope, but the other three novae are very faint at present and will require large telescope to be viewed.
Image Credit: Nova V838 Monocerotis by NASA, Nova Delphinus Map by Sky & Telescope Magazine,Nova Cygni 1992 by NASA and Hubble Space Telescope and T Pyxidis by NASA and ESA
Aadil Desai is an amateur astronomer interested in observational astronomy, astrophotography, eclipses, comets, planets, meteor showers, deep-sky objects, solar and lunar observations besides astronomical sketching since 1981.
Did you know?
The maximum magnitude that novae can brighten to would be equivalent to 50,000 to 100,000 times the brightness of our Sun; that too in just a few days.
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