The new stars

Posted by Daniel Pendick
on Tuesday, February 27, 2007
 
This image made by the Chandra X-ray Observatory
in 2004 shows SN 1572, the youngest supernova
remnant in the Milky Way. It is sometimes referred to
as “Tycho’s nova,” after the 16th century astronomer
who observed and wrote about it. NASA/CXC/MIT/
UMass Amherst/M.D.Stage et al.

A lot of stars came out last week for the Oscars, but astronomers were more interested in the two novae, or "new stars," discovered by Japanese observers in the constellation Scorpius.

Well, not really new. The term "nova" comes from the Latin title of a book written by 16th century astronomer Tycho Brahe (1546–1601). In De Stella Nova (1573), Tycho reported his observation of a star that seemed to appear suddenly in the constellation Cassiopeia.

What Tycho actually saw was a supernova: the cataclysmic explosion of a star. Today we call the nebulous remains of that explosion SN 1572. But the point is that the bright star Tycho saw was new to him, thus the term "new star."

The novae of February 2007 were not stellar deaths. Instead, explosions on the surfaces of the stars triggered the sudden brightening — by a factor of hundreds to thousands.

Novae were a bit of a problem back in the day. The prevailing cosmology in Tycho's time was rooted in the Aristotelian notion that the universe above Earth was perfect and unchanging. Tycho's contemporaries assumed that a "new star" had to be the result of something happening in Earth's atmosphere — not inside the immutable cosmos.

But Tycho's observations showed that the nova had to be quite distant from Earth. He reportedly decried the "thick wits" and "blind watchers of the sky" who would sooner believe their philosophies rather than their own eyes.

Just a parting observation of my own: Although we media people made a big deal out of the fact that two different novae were observed in the same constellation within the same month, it must be said that constellations are artificial constructions of the human mind. The stars in Scorpius are not related, in any objective, physical sense.

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